Session 15
Exploration, Discovery, and
Mine Developments in China
(SEG Sponsored Session)
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Chapter 15-1
15-1
Metallogeny and prospectivity of the Dayaoshan
Region, Guangxi Province, China
Cui Bin, Huang Huimin, Zhao Lei
China University of Geosciences, Beijing, 100083, China
Li Zhong
Shijizhuang Railway Institute, Shijiazhuang, Hebei Province, China
Keywords. Metallogenic series, ore-forming prognosis, granite, mantle
plume, Dayaoshan
Abstract
The Dayaoshan region is located in the Qinzhou-Qiantang
link-belt between the Yangtze plate and the South China
plate. Following multistage geological reworking, the resulting structural pattern gave rise to the Dayaoshan belt
which was surrounded by several basins. Since 1949 exploration aimed at gold, tungsten-tin and lead-zinc, and
special scientific research have focused on in this area.
Following a multi-scale study of the tectonics in the
Nanling area, the authors put forward a model that proposes a mantle-plume existed which had played an important role in the metallogeny of the region. On the basis of geology, geophysics and geochemistry, it is considered that gold is located in the centre of the plume
region, with tungsten, tin, lead and zinc in Dayaoshan
region surrounding the core. Mineralization displays a
strong spatial and temporal relationship with the origin
and evolution of granites in the region. These granites
represent two cycles of mantle-plume activity, and are
accompanied by Caledonian Au-Cu deposit series and
Yanshanian REE-W-Sn-Pb-Zn deposit series
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Chapter 15-2
15-2
The high-grade Baolun gold deposit, Hainan Island, China
Shijiang Ding, Yangrong Fu
Hainan Geological Survey, 88 Nansha Rd, Haikou, Hainan Province 570226, China
Taihe Zhou, Guoyi Dong
Sino-QZ Group Pty Limited, PO Box 2424 Mt Waverley, VIC 3149, Australia; and HT Mining (Beijing) Ltd, 22C-2, 2 Xinxi Rd,
Shangdi Zone, Haidian District, Beijing 100085, China
Abstract. The Baolun gold deposit has the highest grade ores among
the new discoveries for gold in China. The lode-gold quartz vein
systems are hosted in the Silurian low grade metamorphic rocks of
sericite-quartz phyllite, carbonaceous phyllite and slate, and controlled by NNW-trending structures. Thirteen shear zones with alteration and mineralization have been identified in the Baolun area,
and nineteen orebodies have been found within the shear zones 1
to 5. There is significant potential to find more high-grade large
gold deposits in the surrounding areas.
Keywords. Geological setting, high-grade ores, Baolun gold deposit,
Hainan, China
1
Introduction
The Baolun gold deposit in the Hainan province is one of
the most significant discoveries for gold in China for the
last decade. The identified and inferred resources are some
73 Mt ores averaging approximately 10.34g/t gold @ 3g/t
cut off. The main orebody (V1-3) is estimated to contain
some 20 tonnes of Au (643,000 oz Au) averaging 29.48 g/t
Au (Ding et al. 2001), making it the highest grade deposit
of new discoveries for gold in China.
Approximately 50% of the gold is free-milling, coarse
grained, and recovered by gravity circuit (water separation table). The mine grade was about 18 g/t (0.52 oz/t)
with a total recovery of 97%, making it one of the most
economically profitable mines in China.
Thirteen alteration and mineralization zones have been
identified in the Baolun area, and the exploration has been
mainly concentrated in the fault zone 1 by far, therefore,
there is significant potential to make new discoveries. Initiated by Sino-QZ Group, a Canadian and Chinese exploration JV project has been established in an area of approximately 53 km2 directly surrounding the 1.2 km2
Baolun Mine. This paper summarizes the geological setting and characteristics of the orebodies in the Baolun
gold deposit.
2
Geological background
Hainan is an island off the south coast of the mainland
China in the South China Sea. The Baolun gold deposit is
located in the southern part of the island, approximately
110km by road northwest of the city of Sanya. The mine
site is located at an elevation of 220 to 500 meters above sea
level. The topography is moderately rugged, with considerable tree and shrub cover. Access to the deposit is via the
main road, which passes only 13km from the deposit.
In general, there is lack of tectonic information and data
about the Hainan Island. It was suggested that the Hainan
Island was probably a part of the terranes derived from
Gondwanaland in the Devonian (Metcalfe 1997, unpublished
report, New England University). The major NE fold belts
in the island may have been largely affected by the TriassicJurassic orogenic movement, the same time as the
Ailaoshang – Red River fold belt in Yunnan. The island is
close to the contact zone of the southern margin of the South
China craton and the SE Asia block.
The deposit is located along the Ledong basin margin
between the regional E-W trending Jianfeng-Luodiao and
Jiusuo-Lingshui faults. The major rock units in the area
include the high grade metamorphic basement of the
Mesoproterozoic Baoban Group of the Changcheng System, the Silurian low grade metamorphic rocks of the
Tuolie Formation and the Cretaceous sedimentary covers, and some Indosinian (Triassic-Jurassic) and
Yanshanian (late Mesozoic) granites.
The basement metamorphic rocks only occur in the
southwest corner of the Baolun district, and are composed
of the migmatite, plagioclase gneiss and schists. The Silurian Tuolie Formation, which hosts the gold mineralisation,
comprises sericite-quartz phyllite, carbonaceous phyllite and
slate with the total thickness over 1200m. The Tuolie Formation is fault contacted with the underlying Mesoproterozoic
Baoban Group in the southwest; fault contacted with Cretaceous sedimentary rocks in the southeast; and is intruded
by the late Triassic Jianfeng granite in the northwest.
The NE-trending Bahaoshan-Tiewanling thrust separates the Silurian Tuolie Formation and the Cretaceous
sedimentary rocks in the southeast of the mining district. The NNW-trending shear zones, which directly host
the ore bodies, are well developed near the hinge of the
Haogangling anticline, which is about 1.5 km long and
0.8 km wide with its axial trace trending NNW.
3
The Baolun gold deposit
Thirteen shear zones with alteration and mineralization
have been found in the Baolun district. The zones are subparallel to each other, with individual zones 400 to 1300m
Close
1522
Shijiang Ding · Yangrong Fu · Taihe Zhou · Guoyi Dong
long and 10 to 30m wide (up to 80 m wide). In general,
the shear zones trend 325-3550 and dip southwest at 55850. Nineteen orebodies have been identified within the
shear zones 1 to 5. Among them, fourteen orebodies are
located in the major shear zone 1. Occurrences of ore bodies are controlled by the shear zones, with high-grade
auriferous veins in the middle and lower grade disseminated ores enveloping the veins. The orebodies are exposed from 270m to 510m above the sea level, and are
controlled by the underground development from 320 to
130m above the sea level (25m below the sea level for the
orebody V1-3). The orebodies are projected over a strike
length of 160 to 1100m, with an average thickness of 0.454.86m for the individual orebodies. The average ore grades
of the individual orebodies vary from 1.61 to 29.48g/t Au.
Trenching in one of the mineralization/shear zones in the
far southwest also indicates significant gold mineralisation
of four possible orebodies grading from 2.3 to 29g/t Au.
Exploration, development and production have been
mainly concentrated in the shear zone 1, which is some
120m wide, and extends for several kilometres along the
strike. Within the shear zone 1, the orebody V1-3, which is
the principal orebody of the deposit, comprises mainly
of high-grade (29.48 g/t Au) quartz vein type mineralization with lower grade (2.7 - 4.18 g/t Au) ores in the alteration zone enveloping the quartz veins. The orebody V1-3
is totally under overburden, trends 325-3450 and dips
southwest (locally northeast) at 75-850. It has a controlled
length of 310m, averaging 2.62m thick, up to 7.49m locally, and is confined to a depth of 415m downdip. The
orebody V1-3 contains some 20t gold with average grade
over 29.48 g/t, up to 282.70g/t. Visible gold is common in
the major quartz vein orebody, and analysis results are
often over 80 g/t. Approximately 50% of the gold is freemilling, coarse grained, and recovered by gravity circuit
(water separation table). The mine grade was about 18 g/
t (0.52 oz/t) with a total recovery of 97%. The dominant
ore minerals are pyrite, pyrrhotite and free gold, with
subordinate amounts of arsenopyrite and minor nickelbearing pyrite, chalcopyrite, sphalerite, galena, native bismuth, maldonite, bismuthinite, and various Bi-Pbsulfosalts. The gold fineness varies from 921 to 968, and
the gold mainly occurs as fracture filling within or between quartz and pyrite grains; or as tiny inclusions within
pyrite, arsenopyrite, pyrrhotite, chalcopyrite, sphalerite
and quartz. Alteration minerals include quartz, sericite,
chlorite, carbonate and illite.
4
Discussion and conclusion
The Baolun gold deposit is a quartz-vein-system deposit
controlled by structures in metamorphosed Paleozoic sedimentary rocks. Its alteration, mineralization and structurecontrolling characterize an orogenic gold-only deposit
(Groves et al. 1998; Zhou 1999; Zhou and Lu 2000; Zhou et
al. 2002). A preliminary fluid inclusion study indicated that
the main mineralization stage was formed in temperatures
ranging from 240 to 3000C; and analysis on two samples of
alteration illite gave the K-Ar ages of 216 Ma and 205 Ma,
respectively (Ding et al. 2001), which may suggest Hainan
Island could be originally from the Ailaoshan belt, although
further detailed works are required.
The multiple alteration/shear zones that hosting the highgrade gold quartz vein systems, the thickness of the slatephyllite belt along the major structures, and the orogenic
gold nature of the Baolun deposit indicate the significant
potential to find more high-grade large gold deposits in
the corridor as well as in other belts in the Hainan Island.
Acknowledgements
We wish to thank many geologists and management staff
of the Hainan Geological Survey and the Baolun Mine
for sharing their experience and knowledge of the Baolun
deposit and Hainan Island. We also appreciate the time
and support provided to us by the staff from Fury Explorations and Eldorado Gold. In addition, we would like to
extend our appreciations for assistance from staff of the
Sino-QZ Group and HT Mining (Beijing), particularly
Huijuan Wen and Junqi Yin.
References
Ding S, Huang X, Li Z, Fu Y, Dong X, Shu B, Zhang X (2001) Geological features and minieralization of the Baolun gold deposit,
Hainan. Chinese Geology 28: 28-34 (in Chinese)
Groves DI, Goldfarb RJ, Gebre-Mariam M, Hagemann SG, Robert F
(1998) Orogenic gold deposits: A proposed classification in the
context of their crustal distribution and relationship on other deposits. Ore Geology Reviews 13: 7-27
Zhou T (1999) Tectonics and gold mineralisation in East China, Proceedings of PACRIM 99, Bali, Indonesia, International Congress,
Aust. IMM Publications 341-345.
Zhou T, Lu G (2000) Tectonics, granitoids and Mesozoic gold deposits in East Shandong, China. Ore Geology Reviews 16: 71-90
Zhou T, Goldfarb RJ, Phillips GN (2002) Tectonics and distribution
of gold deposits in China - An overview. Mineralium Deposita
37: 249-282
Close
Chapter 15-3
15-3
Characteristics of rock-chip geochemical anomalies of
No. 460 gold deposits in Gansu Province, China
Wei-Xuan Fang, Zhuan-Ying Huang
Beijing Geological Survey Institute of China Non-ferrous Metals Resource Geological Survey, Beiyuan No.5 Yuan,
Chaoyangqu, Beijing 100012, and Open Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, No. 73 Guanshui Road Guiyang 550002, China
Bin Zhou, Yun-Bing Nong, Tian-You Zheng
Northwest Metallurgical Geological Survey Bureau, Xi’an City, China
Abstract. The No. 460 Au deposits of Gansu province in China is located between the Tuwu-Yandong porphyry Cu-Mo deposits and
the Oyu Tolgio porphyry Au-Cu-Mo deposit. Characteristics of rockchip geochemical anomaly were reported in this study, indicating
it might be one of the most promising targets for Au mineralization in porphyry environments in the Late Silurian-Carboniferous
magmatic arc.
Keywords. Rock-chip geochemical anomaly, promising targets, porphyry environments
1
Introduction
Gold and copper mineralization in porphyry and
epithermal environments have become increasingly important exploration objectives during the last decade,
mainly in response to discovery of world-class epithermal
and porphyry Au-Cu-Mo deposits on the Pacific rim
(Corbett and Richaeds 1990; Cooke and Bloom 1990;
MacDonald and Arnold, 1994; Meldrum et al. 1994; Sillitoe
2000). Similarly, Au-Cu mineralizations in the central Asian
orogen have been become hotspots nowadays because
some world-class porphyry or skarn Au-Cu-Mo deposits
were found, for example, Kalmakyr (Almalyk) porphyry
Cu-Mo deposit in Uzbekistan, Borly and Aktogai porphyry
Cu-Au-Mo deposit, Sayak skarn and epithermal deposits
in Kazakhstan, Axi epithermal Au deposit, Tuwu-Yandong
porphyry Cu-Mo deposits in the Tianshan in northwestern China (Feng et al. 1999; Qiu 1999; Zhuang 2003; Zhang
et al. 2000), Oyu Tolgio porphyry Au-Cu and TsagaanSuvarga porphyry Cu-Mo (Lamb and Cox 1998; Watanabe
and Stein 2000; Badarch et al. 2002) in south Mongolia.
These world-class ore deposits might be closely related
to the Late Silurian-Carboniferous magmatic arc which
extended from Kazakhstan, past Tianshan and Beishan
in northern China, via south Mongolia, onto Duobaoshan
porphyry Au-Cu-Mo of Heilongjiang Province in northeastern China (Alexander et al. 2001).
No. 460 Au deposits of Gansu province in China in this
study is located between the Tuwu-Yandong porphyry CuMo deposits and the Oyu Tolgio porphyry Au-Cu-Mo deposit. Geological evolution of the Beishan area in the Late
Paleozoic Era were possible dominated by the Kazakhstan-
Tarim plate in the south and Siberian plate in the north.
The accretion of magmatic arcs were matured and northward-directed migrated.
2
Location and physiography
The study area is located in Gansu Province, the arid Gobi
desert in northwestern China, with eastern longitude of
96°19’09” to 96°27’09” and northern latitude of 42°21’24”
to 42°26’15”. It is less than 30 km south from the border
between China and Mongolia. The Beishan Mountain with
the typical wind-blown erosive rocky hills is at average
elevation of 1695 m above sea level, with a maximum of
2583 m in the Ma’anshan peak. The region is characterized by the relatively flat to gently undulating topography of the rocky Gobi desert. The wind-blown fine-grained
sand mounds around low bushes and grasses common in
the region, indicating that fine-grained sands are transported material. Relative large-size rock-chips more than
3 cm in diameter are derived from weathering exposure
of bedrocks at the surface, which provides a special
geochemical landscape for rockchip geochemical reconnaissance (Fang 1986).
3
Methods
Sampling grids of geochemical rockchip are 250 m × 25 m
with sample spacing 25 m and without sampling within
areas of the Quaternary sediments. Rockchip samples in
the field were, generally, more than 2 cm × 2 cm in size,
most of which were directly derived from outcrops of
bedrocks. Weight of samples was more than 500 g at site
sampling.
Rock-chip samples were crushed 1–4 mm in a rollingball crusher, then quartered, and pulverized 80 g of the
samples in a crusher to less than 0.095 mm in size. The
samples were analyzed at the Analytic Laboratory of
Northwest Geophysical and Geochemical Exploration
Team, CNNC. The rock-chip samples collected for petrographical- geochemical survey were analysed quantitatively by chemical enrichment using spectrographic
method for Au, and by AAF for As, and SG-4 for mercury,
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Wei-Xuan Fang · Zhuan-Ying Huang · Bin Zhou · Yun-Bing Nong · Tian-You Zheng
and by semiquantitative emission spectrographic methods for Mo, Cu, Pb, Zn, Ag, Mn, Ba, Ni, Co, Cr, V, Ti, B, Sr
and Sn. Duplicate samples and Chinese National Standard Gold Samples including GAu-1, GAu-2, GAu-3 and GAu-4
were inserted into each batch for data quality control. For
statistical data on distributions of trace elements in different rocks and bedrock samples were collected separately from the special geochemical and geological profile surveyed and altered rocks observed were avoided
during sampling. However, special attentions were paid
on altered and fractured rocks observed and sampled respectively in order to better understand enrichments of
trace elements in altered rocks. Two type samples were
crushed separately so as to avoid from containments of
each other. Correlation, cluster and factor analysis were
employed to selected better indicator elements for gold
deposits in the region.
4
Results
4.1 Indicator element associations
Au, Ag, Hg, Cu and Mo are possible attached to the same
cluster proved by factor analysis because these elements
were put in the same area, indicating that associations of
Au-Ag-Hg-Cu-Mo may be indicator element associations
for this Au deposit.
4.2 Rock-chip geochemical anomalies
The middle B belts of anomalies typified by Au, Cu, Mo,
Ag, Hg and As may be yielded by auriferous quartz veins
and porphyry gold mineralization occur in district of the
No. 460 gold deposit along trends of the early Carboniferous Baishan Formation and in the middle-late
Hercynian composite intrusions, with the length of more
than 10 km in the NW trend and width of 1 to 3 km in
the NS direction.
Nos.1, 2 and 3 anomalies as presented in Table 1 characterize the middle B belts of rockchip geochemical
anomalies, covering district of the No. 460 gold deposit
in this study. No. 1 anomaly with Au-Cu-Mo-Ag-Hg-As
associations is 3000m long in the NW trend and 1000 to
2000m wide in the SN direction, covering approximately
4.5 km2. The No. 1 anomaly is hosted in the middle-late
Hercynian composite intrusions and altered andesite that
it is attached to the middle part of the early Carboniferous Baishan Formation. There have four higher concentrations of Au-Cu-Mo-Ag-Hg-As associations, whereas one
of them had been drilled in the former exploration activities, indicating it is difficulty only to be interpreted by
the auriferous quartz veins observed up to now. Therefore, three higher concentrations of Au-Cu-Mo-Ag-HgAs associations are open to be tested in the future.
Like No. 1 anomaly, there are two higher concentra-
tions with associations of Au-Cu-Mo-Ag- Hg-As in the
No.2 anomaly, which are much larger than those of the
auriferous quartz veins observed. It can be believed that
there are some rooms for follow-up explorations based
on the rock-chip geochemical anomaly available in the
study. Furthermore, No. 3 anomaly of Au-Cu-Mo-Ag- HgAs associations is more 2500 long in the NW trend and
1000 to 2500m wide in the SN direction, covering approximately more than 4.5 km2 due to its western part is still
open. The No. 3 anomaly is dominant hosted by the
middle-late Hercynian composite intrusions. Five higher
concentrations of Au-Cu-Mo-Ag-Hg-As associations occur in the No.3 anomaly. Actually, the auriferous quartz
veins observed are localized in the largest one, one of
higher concentrations of Au-Cu-Mo-Ag-Hg-As associations. To sum up, 7 out of 11 higher concentrations of
promising Au-Cu-Mo-Ag-Hg-As associations in Nos.1, 2
and 3 rock-chip geochemical anomalies are open to exploration for porphyry-style Au deposit (Fang 1986) to
be tested in the future.
5
Discussion
5.1 A favorable geological environment for Au
mineralization in porphyry
The middle part of the early Carboniferous Baishan Formation comprise gray-green altered andesite with
propylitization typified by chloritization, epidotization
and calcitization, which are peripheral propylitic alteration, accompanying fractured altered rocks and fractures.
These alterations around the middle-late Hercynian composite intrusions are generally extensive and cannot be
readily distinguished from regional, low-grade metamorphism affecting the volcanic rocks and the post-mineral-
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Chapter 15-3 · Characteristics of rock-chip geochemical anomalies of No. 460 gold deposits in Gansu Province, China
ization intrusions. However, regional, low-grade metamorphism of gray-green andesite is relatively weak compared
to the former alteration halo. Stronger propylitic alteration halos, accompanying magnetite, sericitization and
silicification occurred in the contract zone between graygreen altered andesites and middle-late Hercynian composite intrusions, and some of them directly being wall
rocks of the auriferous quartz veins in the district of 460
gold deposit imply that there might be Au mineralization
in porphyry environments with wallrocks of volcanic
rocks.
5.2 Au mineralization possibly occurred in porphyry
environment
First of all, it is very useful to study on distributions of
trace elements in different rocks without and with alterations and fractured for it can help us better understand
enrichment and depletion regularities of trace elements
during hydrothermal processes in the region, especially
to better understand sources of gold metallogenic material. Actually, distributions gold concentrations in different rocks implied that Au mineralization in the study area
possibly occurred in porphyry environment (Fang 1986).
As presented in Figure 3, gold is predominant enriched
in granodiorite porphyry, hematite, jaspilite, granodiorite and auriferous quartz veins. Firstly, the auriferous
quartz veins were mined as gold ores all the time. Secondly, granodiorite (85 ppb Au) and hematite jaspilite (17
ppb Au) contain higher contents of gold, and they are
supposed to be source rocks of gold metallogenic material in the region. On the other hand, Layers of hematite
jaspilite from the Early Carboniferous Baishan Formation are of stable strata with 5 to 20 m thick and more
than 1000 m long in the region, they have thick massive
and laminated structures in red, brown-red or even grey
colours. Hematite jaspilite contains quartz, chert, hema-
1525
tite and magnetite with minor pyrite and trivial chalcopyrite. However, layers of hematite jaspilite interlayered by
andesitic lava and tuff were perhaps related to epithermal
environment. Thirdly, it is very interesting that Au mineralization were found in the fractured and altered plagioclase granite. The middle Hercynian magmatic intrusions in study area comprise granodiorite and plagioclase
granite at ages of 303 Ma dated by the U-Pb method of
zircon (Cui and Chen, 1996). Plagioclase granite occurred
as stocks with long axes of ellipse shape in the EW direction. Locally, it was fractured by late faulting and altered
DP=diorite porphyry; FAGP=fractured and altered granite
porphyry; DPH= diabase porphyrite; GD= granodiorite;
GPD=granite porphyry dike; G=granite by late hydrothermal solutions. Therefore, K-silicate altered rocks in the
fractured and altered plagioclase granite comprise K-feldspar, biotite, sericite, illite and kaolinite. Obviously, some
of the auriferous quartz veins are hosted in the fractured
and altered plagioclase granite. The fractured and altered
plagioclase granite contain Au ranging 60 to more than
1000 ppb Au with a mean value of 102 ppb Au (Fig. 4)
when extensive quartz- sericite- illite alteration occurs as
fine-grained replacements of original rocks including
granodiorite and plagioclase granite, and constituents
without significant quartz-veinlets. However, advanced
argillic alteration associations rich in kaolinite, dickite,
micaceous sericite and illite are absent in the district.
It is significant that diorite porphyry dikes in NW the
trend contain a mean values of 155 ppb Au and ranges of
1.8 to more than 1000 ppb Au. Quartz-sericite-chlorite-pyrite alteration occurs as fine-grained replacements of original
rock in the Au-bearing (> 1000 ppb Au) altered diorite porphyry that it is considered to be new mineralization, i.e.,
gold mineralization in porphyry environment in the district of 460 gold deposit. The diorite porphyry dike intruded
in the granodiorite and plagioclase granite and was inter-
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Wei-Xuan Fang · Zhuan-Ying Huang · Bin Zhou · Yun-Bing Nong · Tian-You Zheng
sected by veins of granite porphyry. Auriferous quartz veins
occurred along the veins of granite porphyry that occurred
as dykes along faults with EW trend. Diabase porphyrite
occurred as dikes and emplaced in NE-trening and EWtrending faults, which can be one part of gold mineralization in porphyry environment in the study area when extensive chlorite-quartz-pyrite alteration appeared. Dikes of
diorite porphyry, granite porphyry and diabase porphyrite
are probable attached to the late Hercynian magmatic intrusions in the district of 460 gold deposit.
5.3 Known auriferous quartz veins
The structure of the district is characterized by three major
EW-trend faults although NE- and NW-trend are also
present. Most of the auriferous quartz veins occurred in
the EW-trend faults. Auriferous quartz veins at grades of
2.1-18.8 g/t Au in the 460 gold deposit are hosted in the
middle-late Hercynian composite intrusions and the altered andesite attached to the upper part of the early Carboniferous Baishan Formation. The auriferous quartz
veins were localized by faults trending EW direction, with
dipping NE 30° to NW 350° at angle of 70° to 80°. The
auriferous quartz veins occurred as veins, lenticular and
dendritic shapes, which are general 200 to 400m long with
maximum length of 900m and 1 to 2.5 m wide. Ore minerals comprise pyrite, chalcopyrite, magnetite, hematite,
siderite and native gold. Gangue minerals include quartz,
calcite, sericite and chlorite. Native gold occurred as
grained, scaly, flaky and arborescent shapes in sizes of
0.1 to 0.6mm with maximum of 1.5 mm in margins or
interstices of metal minerals and quartz. According to Cui
and Chen’s (1996) study on the 460 auriferous quartz vein,
its homogenization temperature of inclusions in quartz
ranges from 110°C to 190°C with salinity range of 12.5 to
15 wt% NaCl eq.. metallogenic presses were from 163 to
174 × 105 Pa, implying that metallogenic depth might be
from 700 m to 650 m deep.
Acknowledgement
Chinese State Key Project on Fundamental Research Planning (Grant No.2001CB409805), LODG Visiting Scholar
Fund of Institute of Geochemistry of Chinese Academy
of Sciences jointly provided financial support for this research project. We are particularly grateful to co-worker
in No. 5 Geological Exploration Team of Northwest Metallurgical Bureau for assistance during the fieldwork.
Close
Chapter 15-4
15-4
Geological characteristics of the Yindonggou Ag-Au-Pb
deposit and its mineralization model, East Qinling
Baojian Guo, Jingwen Mao, Yongfeng Li, Changqing Zhang
China University of Geosciences, 29 Xueyuan Road, Beijing 100083, China
Zhiguang Wang
Henan nonferrous metals Exploration Bureau, Zhengzhou 450052, China
Huishou Ye, Mengwen Li
Institute of Mineral Deposits, Chinese Academy of Geological Science, Beijing 100037, China
Abstract. The Yindonggou Ag-Au-Pb deposit, located in the
Erlangping Group of Palaeozoic age in the East Qinling orogen,
south-western Henan, is a recently discovered, large structural alteration-type deposit. Its main veins are ca. two thousands meters
long and extend to several hundreds meters at depth. It has an
average grade of 333 g/t silver and contains multiple paragenetic
metallic minerals. It may be the economically most potential deposit type in the area. In this paper we briefly describe the geological characteristics, ore-controlling factors, and propose a mineralization model.
Keywords. Geological characteristics, mineralization model,
Yindonggou, Erlangping, East Qinling
1
lntroduction
The Yindonggou deposit is located 100 km northwest of
the Nanyang city in south-western Henan. It occurs in
the Erlangping terrane of the East Qinling west of the
Nanyang basin (Fig. 1). The Erlangping Group consist of
a set of volcanic-sedimentary associations up to several
thousand meters thick. In the last century, several small
to medium-sized porphyry and explosive breccia type CuMo deposits and VMS type Cu-Zn deposits and disseminated Au deposits were discovered in the terrane. The
recent discovery of the large Yindonggou Ag-Au-Pb deposit by No. 3 Geological Party of the Henan Bureau of
Nonferrous Metals Exploration suggests that the area has
good prospects for further finding hydrothermal mineral deposits.
2
Geological setting
The strata exposed in the area are mainly the Erlangping
Group, which is distributed at Xixia, Neixiang, and
Nanzhao counties, Henan Province, and is separated from
the Qinling Group by the Zhuxia deep fault on the south
and from the Kuanping Group by the Waxuezi-Qiaoduan
deep fault on the north. Many geologists (Ren et al. 1980;
Xu et al. 1986; Hu et al. 1988; Zhang et al. 2001) have argued that the fault hosts ophiolites and is closely related
to the subduction of the Yangtze plate beneath the North
China plate and their collision has great significance for
the tectonic evolution of the East Qinling orogen.
Although there are different views about the age of the
Erlangping Group, most geologists assign it to Early
Palaeozoic. In the area, this group can be divided into three
formations; they are in ascending order the Damiao,
Huoshenmiao, and Xiaozai formations. The Damiao Formation is composed mainly of siliceous slate, marble, metamorphosed tuffaceous sandstone, and quartz keratophyre
with a thickness of 1134–1990 m. Its protoliths are an acid
volcanic-terrestrial clastic sequence. The Huoshenmiao
Formation consists predominantly of spilite and quartz
keratophyre with lenses of carbonaceous and siliceous rocks
and marble, with a thickness of 2004–5530 m. The ore deposits occurring in the formation are the Shuidongling and
Xizhuanghe VMS Cu-Zn deposits, Xuyiaogou Au deposits,
and some orebodies of the Yindonggou Ag-Au-Pb deposit.
The Xiaozhai Formation is a thick association of carbonaceous sericite schist and sericite-quartz schist intercalated
with volcanic rocks, having a thickness of 1617–2269 m. Its
protoliths are sandstone and claystone, belonging to abyssal and bathyal turbidity current deposits with flysch characters (Luo et al. 1992). The main part of the Yindonggou
deposit occurs in it.
To the south of the Erlangping Group occurs the
Palaeoproterozoic Qinling Group complex (Shi et al. 2004),
whose protoliths are mainly neritic carbonate rocks with
calcareous pelite. They formed in a short time in the continental-margin and rift environment and afterwards they
underwent several strong metamorphism-deformation
and thermal events (Zhang et al. 1994).
To the north of the Erlangping Group there occurs the
Mesoproterozoic Kuanping Group, which is composed
mainly of two-mica-quartz schist and two-mica schist,
with minor plagioclase-amphibole schist and carbonaceous mica-quartz schist. The protoliths are mainly a
sequence of volcanic and terrigenous clastic rocks. The
former was derived from the depleted mantle, while the
latter from the Qinling Group to the south and Taihua
Group to the north (Zhang et al. 1994; Zhang et al. 2002).
The lineament in the area generally strikes NWW, and
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Baojian Guo · Jingwen Mao · Yongfeng Li · Changqing Zhang · Zhiguang Wang · Huishou Ye · Mengwen Li
from north to south there occur the Waxuzi-Qiaoduan
fault, Zhuyangguan-Xiaguan fault, and Zhengping fault
successively. These faults are large in scale and have a longactive history. On both sides of these faults secondary faults
occur, which are generally up to several kilometres wide.
Due to the influence of regional faulting, NW- and NEtrending secondary faults are developed. They occur in
swarms, extending nearly linearly, parallelly and discontinuously, and intersect with NWW-trending faults to form
a network. All these faults exert a controlling effect on
magmatic activities and mineralization in the area.
Large-scale volcanic eruption and magmatic intrusion
at different levels have occurred in the area. The
Erlangping volcanic rocks are a suite of calc-alkaline
basalts to alkaline tholeiite, which is considered to be the
product of eruption and sedimentation in the back-arc
basin (Zhang et al. 2002). The magmatic intrusion mainly
took place in the Palaeozoic and Mesozoic, forming acid
rocks (batholiths or large rock bodies) distributed in a
nearly E-W-trending zone. Mesozoic magmatism generally occurred at the intersection sites of the NWW- and
NE-trending faults and controls vein type mineralization
surrounding them. For example, the Yindonggou Ag-AuPb deposit is controlled by a hidden rock body.
3
Geological characteristics of the Deposit
The ore district is divided into the Yindonggou ore block,
Zhouzhuan ore block and Tumuya ore block (Fig. 1). There
are a total of 53 veins in the deposit, all of which occur in
fractured zones surrounding the concealed rock body. The
host rocks are sericite-quartz schist and metasandstone
of the Xiaozhai Formation and metaspilite, spilite tuff and
granite of the Huoshenmiao Formation. There are two
groups of veins: the nearly N-S group and the NW group,
with the former predominating. The veins are several
hundred to several thousand meters long and thin and
uniform with an average thickness of 0.73 m (Table 1).
They contain many and rich useful components. The average grades are Ag 333 g/t, Au 4 g/t, Pb 2.78%, and Zn
1.90% and the ore reserves are Ag 1700 t, Au 12 t, and
Pb+Zn 430,000 t.
So far only the Yindonggou ore block has had a relatively high level of exploration and a small mine has been
operated there; therefore the characteristics of the
orebodies are clearer.
The Yindonggou ore block is located in the eastern
part of the deposit (Fig. 2), including 13 veins. The ore
reserves are Ag 1250 t, Au 10 t, Pb 100,000 t, and Zn 50,000
Close
Chapter 15-4 · Geological characteristics of the Yindonggou Ag-Au-Pb deposit and its mineralization model, East Qinling
t. The host rocks are carbonaceous fine clastic rocks of
the Xiaozhai Formation, marine mafic volcanic rocks of
the Huoshenmiao Formation, and the late Palaeozoic
Hercynian Lujiaping granite. The orebodies are not complex and mainly occur in bedded, bed-like, and podiform
shapes. Polymetallic sulphide quartz veins occur (0.21.2 m thick generally) at the centre of the orebodies and
grade into Ag-Au polymetallic sulphides and pyritizedsericitized rocks towards two sides, but the boundary of
orebodies cannot be recognized before chemical analyses.
The main orebody Y1, 2300 m long, occurs in carbonaceous fine clastic rocks of the Xiaozhai Formation and
Hercynian Lujiaping biotite granite. The shapes of the
orebody are simple, mainly bedded, bed-like or podiform.
They strike N10°E and dip west at ~30° at the surface,
and dip more steeply toward the depth. The thickness is
generally about 0.6 to 0.9 m, with an average of 0.65 m.
The averaging grades are Ag 466 g/t, Au 5.3 g/t, Pb 2.1%,
and Zn 1.9%. The thickness and grade of the orebody
increase at depth.
The main metallic minerals include electrum, argentite, gold, galena, sphalerite, pyrite, chalcopyrite, and pyrrhotite; the gangue minerals include quartz, feldspar,
sericite, chlorite and calcite. The ore exhibits euhedral to
anhedral granular texture, cataclastic, interstitial, poikilitic,
and replacement corrosion textures and spotted, disseminated, massive, banded, network, and breccia structures.
The alteration types include silicification, pyritization,
sericitization, chloritization, and carbonisation. The alteration zones, varying in thickness from ~5 to 10 m, generally are thicker in metamorphic rocks of the Erlangping
Group and narrow in granite.
There are three mineralization stages: (1) quartz-pyrite
stage, which witnessed filling of quartz along cracks and
ductile deformation; (2) quartz-polymetallic sulphide stage,
which is the crucial mineralization stage; and (3) carbonate stage, in which mineralization was relatively weak.
The mineralization and alteration exhibit apparent
vertical zoning: carbonization and weak mineralization
are pronounced at the top of the orebodies; pyrite, galena and silver increase in the middle; and at depth
sphalerite, chalcopyrite and gold increase but silver decreases.
4
1529
Proposed mineralization model
There is no direct and reliable evidence about the mineralization age so far, but it is inferred that the deposit probably formed in the Mesozoic.
As the veins cut Hercynian granite and occur around
the blind Mesozoic granite, the mineralization should
occur later than Hercynian granite and even slightly later
than Mesozoic granite. In addition, according to an analysis of the geological evolution, the Mesozoic, especially
the period of Late Jurassic to Early Cretaceous, is the main
mineralization age for most hydrothermal deposits in the
East Qinling orogen.
The ore-forming material might be derived from the
Xiaozhai Formation. On the basis of dispersion train
measurements of the Xiaozhai Formation by the No. 5
Geological Survey Party of the Henan Nonferrous Metals
Exploration Bureau in the 1990s, the contents of the oreforming elements Au, Pb, Zn, As, Sb, Bi, Ba, and F and
indictor elements are apparently higher than those in the
underlying Damiao and Huoshengmiao formations, and
the high contents of volatiles such as Ba and F suggest
that the Xiaozhai Formation might be abyssal argillaceous,
fine clastic rocks associated with hydrothermal sedimentation.
The nearly N-S- and NE-striking ore-hosting faults
exhibit the characteristics of multi-stage activities. They
were ductile in the early stage and brittle in the mineralization stage.
The ore-forming fluids are of Cl-Na type with Cl>F
and Na>K, being mainly neutral, and became CO32- type
in the late stage, showing the subalkaline character. Fluid
inclusions show that they contain magmatic water and
meteoric water. The variation in composition of the inclusions shows that more and more meteoric water entered into the ore-forming fluids with the evolution of
mineralization (Zhang et al. 2004).
The proposed mineralization is as follows: The subduction of the south China plate beneath the North China
plate in the Early Palaeozoic resulted in the formation of
the very thick Erlangping Group in a back-arc basin environment. The Xiaozhai Formation in this environment
became the main ore source because of its high content
of ore-forming material and feature of easy remobilisation.
Close
1530
Baojian Guo · Jingwen Mao · Yongfeng Li · Changqing Zhang · Zhiguang Wang · Huishou Ye · Mengwen Li
In the Triassic the North China plate and South China
plate collided and were amalgamated, resulting in N-S
compression and crustal shortening in the East Qinling
(Zhang et al. 2001; Mao et al. 2003, 2005), and the high
pressure and high temperature brought about partial
melting of the lower crust. In the Late Jurassic to Early
Cretaceous (at 140-120 Ma), lithospheric thinning and
extension in eastern China resulted in upwelling of the
asthenosphere and large-scale magma activities. Under
the controls of the tectono-thermal event, magmatism,
and magmatic fluids and later in the presence of meteoric water, ore-forming fluids extracted ore substances
from the Xiaozhai Formation and unloaded them along
the reactivated N-S- and NW-trending faults, thus forming the large Yindongou Ag-Au-Pb deposit.
References
Chu XC, Wang HZ, Sheng XG, Guo LF, Zhang JZ (1992) The geology
and mineral resources of Henan province (in Chinese). Prospect
Press of China, Beijing, 1-918
Deng JF, Zhao HL, Muo XX, Wu Z, Luo ZH (1996) Continental rootmantle tectonics in China: a key to continental dynamics (in Chinese). Geological Publishing House, Beijing, 449-356
Ren JS, Jiang CF, Zhang ZK (1980) The tectonics and evolution of
China (in Chinese). Science and Technology Publishing House,
Beijing, 1-124
Hu SX, Lin QL, Chen ZM, Sheng ZL, Li SM (1988) Nanjing University
Press, Nanjing, 1-553.
Jin SW (1988) Discussion on the aspects of Erlangping group. Henan.
Geology 6(4):21-26
Luo MJ (1992) Henan gold deposits (in Chinese). Seismology Publishing House, Beijing, 1-442
Luo MJ, Li SM, Lu XX, Zheng DQ, Su ZB (2000) Metallogenesis and
deposits series of main mineral resources of Henan province (in
Chinese). Geological Publishing House of China, Beijing, 1-355
Mao JW, Xie GQ, Zhang ZC, Li XF, Wang YT, Zhang CQ, Li YF (2005)
Mesozoic large-scale metallogenic pulses in north China and corresponding geodynamic settings (in Chinese). Acta Petrologica
Sinica 21:169-188
Shi QZ, Yu XD, Li ML, Pang J (2004) The nappe and extentional structure of north margin of east Qinling, Henan province. Geological Publishing House of China, Beijing, 1-204
Xu ZQ (1986) The metamorphic charecteristics and tectonic evolution
of east Qinling (in Chinese). Acta Geologica Sinaca 60:237-247
Wang Zg, Liu XD, Zhang ZB, Zhang YL, Xiang SH (2002) The oreforming environment of the silver polymetallic deposit in
Erlangping group, east Qinling and its prospecting perspectives.
Chinese Geology 28(7): 32-36
Zhang BR, Gao S, Zhang HF, Han YW (2002) Qinling orogenic belt
geochemistry (in Chinese). Science Press of China, Beijing, 1-187
Zhang GW, Zhang BR, Yuan XC, Xiao QH (2001) Qinling orogenic
belt and continental dynamics (in Chinese). Science Press of
China, Beijing, 1-855
Zhang J, Cheng YJ, Li GP, Li ZL, Wang ZG (2004) Characteristics of
ore geology and fluid inclusion of the Yindonggou silver deposit,
Neixiang county, Henan province: implication for metallogenic
type. Journal of Mineral and Petrology 24(3): 55-64
Zhang ZQ, Liu DY, Fu GM (1994) Isotopic research on the metamorphic strata of north Qinling (in Chinese). Geological Publishing
House, Beijing, 1-191
Close
Chapter 15-5
15-5
Mesozoic Au-Ag-Pb-Mo mineralization in the
Xiong’ershan area, western Henan Province, China
Baojian Guo, Jingwen Mao, Yongfeng Li, Fengmei Chai
China University of Geosciences, 29 Xueyuan Road, Beijing 100083, China
Huishou Ye, Mengwen Li
Institute of Mineral Deposits, Chinese Academy of Geological Science, Beijing 100037, China
Abstract. The Xiong’ershan district is located on the southern margin of the North China Craton and is the second largest Au area in
Henan Province, China. It contains Mesozoic hydrothermal Au and
Ag, Pb and Mo deposits. The deposits can be classified into different types: cryptoexplosive breccia type Au deposits, structural alteration type Au, Ag and Pb deposits, and porphyry type Mo deposits. The porphyry type Mo deposit formed earlier than other types
of deposits. Various deposits formed in an extensional environment
that resulted from rapid lithospheric thinning in eastern China during 140-120 Ma, and the combination of a tectono-thermal event
and deep deep-seated magmagtic ore fluids and meteoric water
that resulted in the formation of large-scale hydrothermal mineralization.
Keywords. Deposit type, mineralization characteristics, metallogeny,
mineralization model, Xiong’ershan
1
lntroduction
The Xiong’ershan area islocated on the southern margin of
the North China craton and is the second largest Au area in
Henan Province, China (subsequent to the Xiaoqinling Au
area). It extends 80 km from east to west and is 15 to 40
km wide, covering an area of ca.2000 km2. It is bounded on
the north by the Luoning fault and on the south by the
Machaoying fault (Fig. 1). A wealth of published data about
this gold-polymetallic area is available (Chen and Fu 1992;
Chu et al. 1992; Ren et al. 1996; Wang et al.1996; Zhang et al.
1996, 2001; Guo et al. 1997; Luo et al. 2000; Zhang et al. 2002;
Mao et al. 2002a, b, 2003, 2005; Li et al. 2004a, b, 2005). Since
the 1980s, many Au deposits and Ag- Pb-Mo deposits have
been found and several state-owned gold mines developed.
To date geological parties, state-owned gold mining enterprises, private companies and joint ventures have been successfully conducting exploration for Au, Ag, Mo and Pb resources in the area. Among the deposits, the Qiyugou
cryptoexplosive breccia type gold deposit has attracted a
good deal of attention of geologists for its specific geological characteristics.
2
Regional geological setting
The North China and Yangtze blocks collided in the Tertiary, forming a unifying continent (Ames L et al. 1993; Zhang
GW et al. 1996, 2001). Later, the Xiong’ershan area became
an important component part of the Qinling orogen. The
strata in the area are divided into three tectonic units: medium- and high-grade metamorphic basement rocks of the
Neoarchean Taihua Group (green formation); low-grade
metavolcanic rocks of the Mesoproterozoic cover Xiong’er
Group, and littoral-neritic sedimentary rocks of the
Guandaokou Group; and Meso-Cenozoic red clastic sedimentary rocks in the extensional downfaulted basins, including sandy conglomerate with mudstone of Late Cretaceous Qiuba Formation, lacustrine- dilluvial-shallow lakeswampy clastic deposits of Paleogene Gaoyugou, Dazhang
and Tantou Formations from bottom upwards in the most
developed Tantou basin (Chu et al. 1992). Of these the Taihua
Group metamorphic rocks form the basement of the craton, overlain by the widespread Xiong’er Group volcanic
rocks in west Henan and Guandaokou Group littoral-neritic sedimentary rocks. Both the Taihua and Xiong’er Groups
are main host rocks for Au-Ag-Pb-Mo deposits in the area
(Wang et al. 1996; Ren et al. 1996; Luo et al. 2000; Mao et al.
2002a).
The metamorphic complex and detachment faults developed in the area are a record of Meso-Cenozoic extensional tectonic movement (Wang et al. 1996; Wang et al.
2002; Mao et al. 2005). The detachment fault extend along
the unconformity between the metamorphic basement
of the Neoarchean Taihua Group and the overlying
Mesoproterozoic Xiong’er Group, and the north detachment fault is easier recognizable (Guo et al. 1997). The
other important regional faults include the Luoning fault
in the north and Machaoying faults in the south.
There are four sets of ore-controlling faults in the area:
NE-ENE, NNE, NNW and nearly E-W, which form the
structural framework of the area. Among them, the NEENE trending faults are best developed, widespread and
closely related to the common gold-silver-lead type-the
structural alteration type deposits.
Three periods of magmatism occur in the region: (1)
Neoarchean magmatism appeared as intermediate -basic volcanic rocks of the Taihua Group, which were metamorphosed into various of gneiss in the late stage; (2)
Mesoproterozoic magmatism mainly gave rise to rift-type
intermediate-basic-acid volcanic rocks; and (3) Mesozoic
magmatism which extensively and intensely occurred in
Jurassic -Cretaceous age, forming abundant of granitoids.
The Huashan granitic batholith is a representative com-
Close
1532
Baojian Guo · Jingwen Mao · Yongfeng Li · Fengmei Chai · Huishou Ye · Mengwen Li
posite in the area. In addition, intermediate -acid stocks
and mafic dykes are also exposed. Spatially, mineralization in the area exhibits a close relation to Mesozoic
granitoids, and most deposits occur around or within them
(Wang et al. 1996; Mao et al. 2003).
3
Types of Au-Ag-Pb-Mo deposits
The main hydrothermal mineralization includes structural alteration type, (which contains steeply dipping-subtype, e.g. the Shanggong Au, Gongyu Au, Kangshan Au,
Tieluping Ag-Pb and Shagou Ag-Pb deposits, and gently
dipping-subtype deposits, e.g. Qingangping Au and
Luyuangou Au deposits), cryptoexplosive breccia type
(Qiyugou Au deposit) and porphyry–type deposit
(Leimengou Mo deposit). The location of various main
deposits is shown in Figure 1 and their characteristics
are given in Table 1.
4
Metallogeny of Mesozoic Au-Ag-Pb-Mo
hydrothermal ore deposits
In the Mesozoic eastern China underwent an event of
prominent lithospheric thinning (Deng et al. 1996) and
tectonic regime transition, thus resulting in strong
magmatism and extensive mineralization (Mao et al. 2003,
2005). Magmatism and mineralization in this area mainly
occurred at 140-120 Ma. The reliable ages obtained in recent years are as fellows:
The Huashan granite batholith has a SHRIMP zircon
U-Pb age of 132.0 ± 1.6 Ma, the Leimengou granite- porphyry has a SHRIMP zircon U-Pb age of 136.2 ± 1.5 Ma
(Li 2005), the Mo deposit has a Re-Os model age of
132.4 ± 2.0 Ma (Li et al. 2004a), the Qiyugou Au deposit
has a mineralization age of 125 Ma (Wang et al. 2001)
and the Gongyu Au deposit has a mineralization age of
122 Ma (Li and Qi 2002). The ages show that: firstly, the
Close
Chapter 15-5 · Mesozoic Au-Ag-Pb-Mo mineralization in the Xiong’ershan area, western Henan Province, China
granite-porphyry formed earlier than the Huashan granite
batholith and secondly, the Leimengou porphyry Mo deposit formed earlier than structural alteration type deposits and crypoexplosive breccia type Au deposit.
Spatially, various types of deposits occur in the same
tectonic unit, reflecting that they are possibly correlated.
The structural alteration type (including steeply dipping
and gently dipping subtype) is directly controlled by faults
and detachments, and the cryptoexplosive breccia type and
porphyry type are mainly controlled by the intersection
site of faults. Porphyry deposits generally occur in the granite
porphyry stocks, while cryptoexplosive breccia type deposits
mainly occur in the overlying country rocks of them.
The porphyries related to the Mo deposit are mainly
derived from the upper mantle and low crust represented
by the metamorphic rocks of Neoarchean Taihua Group
(Wang et al. 1986; Zhang et al. 2002; Li 2005), and the δ34S
values for sulphide minerals from the main mineralization of Mo and Au deposits exhibit a narrow range of
closing to naught, implying a deep origin of the ore substance which possibly derived from the Taihua Group
green formation and upper mantle (Mao et al. 2002b; Li
et al. 2004a).
The Hydrogen-Oxygen, Helium-Argon and Nitrogen
isotopes show the close relationship of the ore-forming
fluids with the magmatic fluids, and in some deposits
(e.g.Qiyugou and Gouyu gold deposits) the meteoric water participated in the hydrothermal mineralization system in late stage (Mao JW et al. 2002b; Li et al. 2004b).
5
Hydrothermal mineralization model
The North China Block and Yangtze Block collided in the
Triassic, resulting in extensive N-S compression and
crustal shortening in the Qinling region (Zhang et al. 1996;
Ren et al. 1998; Mao et al. 2003, 2005) including the
Xiong’ershan area. High pressures and temperatures lead
to partial remelting of the lower crust. Approximately in
the Late Jurassic to Early Cretaceous (140-120 Ma), rapid
lithospheric thinning in eastern China resulted in regional
extension, upwelling of the asthenosphere and emplacement or eruption of voluminous magmas (ca.130 Ma).
Under the combined controls of the tectono-thermal event
and deep-seated magmatic ore fluids and late meteoric
shallow fluids, large-scale mineralization occurred (Mao
et al. 2003, 2005).
Porphyry type Mo mineralization occurred earlier, and
then cryptoexplosive breccia type Au mineralization and
structural alteration type Au- polymetallic mineralization occurred. For the structural alteration type, the orecontrolling faults has the features of multi-stage activities: in the early stage they usually exhibited a thrust and
mylonization; and during the mineralization stage, the
principal stress was oriented in a NE-SW direction (Wang
et al. 1996; Wan TF et al. 2002) and the faults of the simi-
1533
lar direction exhibited relatively extensional features,
which lead to ascent and filling of ore fluids along them
and formation of steeply dipping NE- and NNE-trending
ore veins, which occur nearly parallelly in swarms and
zones.
There are also gently-dipping structural alteration gold
deposits occurring within detachment faults (e.g. the
Qingganping gold deposit). The early-formed ductile shear
zones were superimposed by brittle faults and filling of
hydrothermal ore fluids during the mineralization stage
(Guo et al. 1997).
In the Late Cretaceous some small extensional basins
began to form in the surrounding area of the mining area.
Piedmont and fluiviolacustrine sandy conglomerate with
mudstone of the Late Cretaceous Qiuba formation are
developed on the south slope of Xiong’ershan (Chu et al.
1992). The coarse sands and poorly-sorted gravels, are
mainly derived form volcanic rocks of the Xiong’er Group
rather than metamorphic rocks of the Neoarchean Taihua
Group or Mesozoic Huashan granite, indicating that the
Taihua Group and Huashan granite had not been exposed
on the surface despite significant uplift at that time. Later,
the deposits of the Paleogene Dazhang and Tantou Formations contain the gravels derived from the Neoarchean
Taihua Group, suggesting that the Taihua Group was exposed on the surface at that time.
Acknowledgements
This study was supported by China Natural Science Foundation (Grant No.40434011).
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geochemistry (in Chinese). Science Press of China, Beijing, 1187
Close
Chapter 15-6
15-6
The significance of the early deformation
architecture in localizing “Carlin-like” gold
mineralisation at the Jianchaling Gold deposit,
Shaanxi province, Peoples Republic of China
Andrew. P. Ham
SRK Consulting, Level 26, 44 Market St, Sydney, NSW 2000, Australia
Fan Kaiqiang
Sino Mining Shaanxi Limited, Jianchaling Mine, XQG Village Hejiayan Township, Lueyang County, Shaanxi Province, 724308,
China
R. Corben, P.J. Uttley
Sino Gold Limited, Level 8, 17 Bridge St, Sydney, NSW 2000, Australia
Abstract. The Jianchaling (JCL) deposit is located on the northern
edge of the South China Craton and is separated from the North
China Craton by the ESE-WNW trending Qinling-Dabie orogenic belt.
A recent structural geology study established a new deformation
framework for the local mine area. Structural controls on the distribution of Carlin-style mineralisation developed during early ductile deformation that preceded gold mineralisation. Early ductile
deformation saw the rotation of early shallow dipping thrust faults
to upright attitudes during regional folding. Subsequent extension
or gravitational collapse folded bedding and the F145 fault asymmetrically about shallow dipping axial planes, whereby one limb
maintained a shallow north dip. These deformation events produced
the critical structural architecture for the gold mineralising event.
“Carlin type” gold mineralisation was synchronous with late reverse
movement along the F145 fault that locally brecciated the shallow
north dipping “heterogeneities” in the F145 fault geometry. These
heterogeneities were a product of early folding of the F145 fault.
The shallow dipping heterogeneities provided the zones of maximum dilation and fracture during the gold mineralising stage, resulting in shallow plunging ore shoots. Steeply plunging ore shoots
developed at the intersections of cross cutting gold stage NW and
NE striking faults with the ESE striking F145 fault.
The Jianchaling mine provides an example where the early deformation history was vital to developing “traps” for mineralisation.
In the absence of early recumbent folding, only small, steeply
plunging ore shoots would have developed along the F145 fault.
Keywords. China, Jianchaling, structure, Carlin type, cleavage asymmetry
1
Introduction
The Jianchaling (JCL) gold mine is located along the southern border of the Qinling-Dabei orogenic belt, and on
the northern edge of the South Chian Craton in southwest Shaanxi Province of the Peoples Republic of China.
It is the first mine designed, constructed, financed and
operated to western standards in China, with a pre-mined
resource of 1.6 Mt @ 9.85 g/t gold (Vielreicher et al., 2003;
Erceg et al., 2004). An ongoing drilling program is cur-
rently looking to expand the resource of the nearby
Zhangjianshan (ZJS) deposit, as reserves at JCL are almost exhausted.
In the mine region, gold is located at the contact of Proterozoic ultramafic and dolomite units that are separated
by steeply dipping ESE-WNW trending faults. Within the
Jianchaling mine, the most voluminous zone of gold
mineralisation occurs along shallow north dipping portions
of the ESE trending F145 fault; where the bulk of gold
mineralisation is hosted within the footwall ultramafic sequence with minor occurrences of economic gold in the
hanging wall dolomite sequence. Gold mineralisation is submicron sized and generally occurs in arsenic-rich rims of
finely disseminated sulfides, particularly pyrite, and is
constrained within dark grey dolomite-quartz-pyrite alteration selvedge’s in veins and fractures that have formed
late in the deformation history. The strong element association of the Au-As-Hg and the alteration and mineralisation assemblages led Erceg et al. (2004), to classify the
deposit as “Carlin type”.
Two types of ore shoots are found within the deposit.
The most voluminous high-grade ore domains are shallow ESE plunging ore shoots that are located along shallow north dipping portions of the F145 fault. Thinner by
volume are ore domains that occur at intersections of
steeply dipping NW-SE to NE-SW trending faults with
the F145 fault. These ore shoots typically have steep east
plunges, as the F145 fault has a steep NNE dip.
JCL and ZJS are both structurally controlled “Carlintype” gold deposits, where gold is sub-micron sized and
generally occurs in arsenic-rich rims of finely disseminated pyrite crystals. To optimize exploration programs,
a joint study with staff from Sino Gold and SRK Consulting was initiated to identify testable structural models
for the localisation of mineralisation in the Sino Gold mine
lease and exploration licence areas.
Close
1536
Andrew. P. Ham · Fan Kaiqiang · R. Corben · P.J. Uttley
2
Local geology and geometry of the deposit
Gold mineralisation at the Jianchaling deposit is hosted
in the steeply north dipping F145 fault and it is the most
prominent fault in the mine area. The F145 fault separates
metasedimentary rocks in the hanging wall from metamorphosed ultramafic (dunite, harzburgite - Vielreicher
2001) rocks in the footwall, and can be traced along strike
for about 5.5km (Fig. 1). The ultramafic footwall rocks
consist of variably metasomatised serpentinites and gabbroic rocks (Vielreicher et al. 2003), and are believed to
be mid to late Proterozoic in age. The serpentinized footwall sequence adjacent to the F145 fault has been primarily altered to fine grain talc schists, talc-magnesite schists,
or massive magnesite rocks with minor quartz-carbonate alteration The footwall ultramafics were overlain by a
hanging wall sequence that consists of highly fractured,
weakly metamorphosed, recrystallised, massive to well
bedded limestone and dolomite. Adjacent to the F145 fault,
the carbonate rocks are highly fractured and recrystallised,
with variable amounts of silicification. To the north, the
hanging wall carbonates are separated from a thick sequence of phyllites and graphitic slates by a steep ESE
striking fault, referred to as the F146 fault.
Bedding is generally steeply north dipping and it is
sub-parallel to the F145 fault geometry. Within the main
ore zone at JCL, the F145 fault and bedding have been
rotated asymmetrically to shallow north-northeast dips.
In long section the main ore zone has a shallow plunge
along strike that is intersected by both steep NE and NW
striking faults that are SE and NE dipping respectively.
The intersections of these faults produce moderate to
steep east pitching ore shoots. However along the main
ore zone, there are NE to NW striking faults that dip
shallowly from the NW to SE, cross cut the F145 fault and
locally have increased volumes of ore in the footwall of
these faults. Displacement along the cross cutting NE and
NW faults is usually small with the majority offsets less
than 15m.
Whilst the minor shallow faults (or splays) locally produce shallow plunging ore domains, the overall shallow
geometry of the main ore zone is continuous for more
than 500m along strike (Fig. 2). In cross section the main
ore zone ranges up to 100m wide along the shallow northdipping portion of the fault, in areas where shallow north
dipping faults are absent. Therefore the overall shallow
north dipping ore geometry along the F145 fault must be
a product of deformation that preceded mineralisation.
Thus to understand the localisation of ore along the F145
fault, necessitated an investigation into the deformation
events that initiated the fault and subsequently modified its shape.
Close
Chapter 15-6 · The significance of the early deformation architecture in localizing “Carlin-like” gold mineralisation at the Jianchaling Gold deposit
3
Summary of the deformation history
Structural mapping of the surface and underground exposures, as well as logging of drill core, provided a new
deformation framework of the local mine area. Extensional deformation in the time period between the mid
to late Proterozoic saw the extrusion of the footwall
ultramafics, which precipitated sub-economic nickel
mineralisation. Circulation of seafloor hydrothermal fluids synchronous with the extrusion serpentinised the ultramafic rocks. This was followed by the deposition of
the hanging wall sequences of the Duan Tou Yan formation in a progressively deepening ocean.
Compressional deformation (D1) which was approximately N-S directed, affected these sequences late in the
Phanerozoic by initiating thrusting along ESE striking faults,
including the F145 fault. Regional upright folding followed
during approximately NNE-SSW bulk shortening (D2).
During D2, bedding and ESE striking faults within the mine
area were rotated from shallow to steep dips. This deformation event records near peak metamorphic conditions
and produced the dominant differentiated crenulation cleavage in the region. Reverse faulting along the ESE striking
faults late in D2 enhanced the penetration of CO2 rich fluids that metasomatised both the ultramafic and sedimentary sequences. Recumbent folding during D3 locally rotated bedding and early deformation fabrics and faults from
steep to shallow dips. Deformation during D3 is possibly
the consequence of orogenic collapse of the orogen between
shifts in the direction of bulk shortening. Strain was accommodated along the F145 fault by folding during D3 rather
than by shearing, and deflected the geometry of portions
of the fault from steep to shallow dips. NE over SW displacement was recorded by bedding, the S2 foliation and
the folded portions of the F145 fault. Folding of the F145 fault
created heterogeneities in the average fault dip that focussed
deformation and mineralisation during D4.
Renewed horizontally directed NE-SW shortening transpired during D4. Exhumation of the rocks during D3 had
elevated the rock package to higher crustal levels, where
brittle deformation dominated. Reactivated sinistral reverse
(mostly reverse) faulting along the ESE striking F145 fault
saw strain accommodated across shallow dipping portions
of the fault by fracture and brecciation. Enhanced fluid flux
in to these zones of brecciation advanced the precipitation
of gold. Reactivated reverse shear along the long limbs of
the folded fault propagated new hanging wall faults. Steep
NW striking mostly reverse faults disrupted the F145 faults
and locally precipitated narrow, steep plunging ore shoots.
Small offsets (<10m) of the F145 fault along steep NNE
and NNW striking faults post date gold mineralisation
during D5. Bulk shortening during this phase of deformation was E-W directed whereby only minor fractures
and faults developed.
4
1537
Significance of early ductile deformation to
mineralisation
The early ductile deformation at Jianchaling has controlled
the architecture of the F145 fault for later gold mineralisation. A key to recognising the importance of the early
ductile deformation was found in the differentiation asymmetry of cleavage in phyllites and slates found in the hanging wall of the F146 fault, which is located parallel to and
north of the F145 fault. The hanging wall of the F146 fault
hosts an anticline where on the northern side of the anticline, the differentiated cleavage S2 is steeper than bedding and is sub-parallel to the axial plane. Vergence from
both the differentiation asymmetry and bedding cleavage relationships indicates an anticline to the south. On
the southern limb of the anticline, the S2 cleavage has a
shallower dip than bedding and the differentiation asymmetry indicates a syncline to the north. This indicates
that the S2 cleavage was not axial planar to the hanging
wall fold and that the geometric relationship is only possibly if the S2 differentiated cleavage has been folded with
bedding. Asymmetries from weaker fabrics developed
during D3 and D4 suggest that folding in the hanging wall
of the F146 fault was a two-stage process. Initially steeply
dipping beds and cleavage were rotated to shallower dips
during D3, which then exposed both bedding and cleavage to upright folding during D4.
Deformation in the hanging wall carbonate rocks could
not be accommodated by folding in the same way as the
‘weaker’ phyllites and slates within the hanging wall of
the F146 fault during D4. Instead, deformation was effectively partitioned coarsely between the two steeply dipping ESE striking faults during D4 and was mostly accommodated by reactivation of these faults. This partitioning of strain was crucial in localising brecciation along
the F145 fault during mineralisation.
Reactivation of the F145 fault, however, was not enough
to localise of economic gold mineralisation. It was the
shear of the irregular geometries within the gross F145
fault shape during reactivation that allowed mineralisation
to be localised into an economic gold deposit. The geometry of the F145 fault has followed a similar path to bedding in the hanging wall phyllites. After initial thrusting,
the F145 fault rotated to a steep north dip during regional
upright folding, where the regional fold axis is located
more than a kilometre to the SSW of the mine. Ductile
deformation during D3 folded the F145 fault about shallow dipping axial planes with a NE over SW sense of shear.
These folded portions of the F145 fault are heterogeneities within the gross fault geometry that enabled fracturing and brecciation to be localised during reactivation of the F145 fault during D4. Shallow dipping splay faults
initiated along the folded portions of the F145 fault to accommodate the mostly reverse movement of the F145 fault.
Close
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Andrew. P. Ham · Fan Kaiqiang · R. Corben · P.J. Uttley
Consistent shallow southwest dipping sheeted mineralised
veins/fractures sets developed in response to the movement along these splays and the F145 fault. In contrast,
steep NW striking reverse faults that intersect the F145
fault and were active during gold mineralisation
(Vielreicher et al. 2003) produced steeply plunging but
thin ore zones. In the absence of the heterogeneities along
the F145 fault that developed during D3 folding; only thin,
steeply plunging, sub-economic mineralised zones could
form. Therefore the deformation during both D2 and D3
has been crucial to creating heterogeneities along the F145
fault that subsequently localised gold mineralisation.
5
Conclusion
Transporting metals in a hydrothermal system typically
requires large fluid fluxes due to the low solubility of metals. The percolation of a significant volume of fluid to
precipitate an ore deposit requires enhanced permeability particularly in low permeable rocks. Fractured rocks
in fault zones create zones of high permeability for hydrothermal fluids to flow. However, the fault zone must
be active, as any precipitation of minerals from the hydrothermal fluid, such as quartz, will reduce the fault zones
permeability. Heterogeneities within active fault zones are
locations where rock fracture intensifies, as the rock has
to accommodate deformation around the heterogeneity.
Zones of intense fracture or brecciation increase fluid flow
into these zones and the enhanced porosity locally reduces
the fluid pressure and thereby promotes mineral precipitation. The Jianchaling deposit is an excellent example where
the early ductile deformation was critical in developing
heterogeneities within the F145 fault that subsequently
localised gold mineralisation. Gold mineralisation has developed late in the deformation history and has “Carlin like”
affinities, with strong element associations of the Au-AsHg as well as the alteration and mineralisation assemblages.
However without the structural “traps” that developed during early ductile deformation, gold mineralisation at the
JCL deposit, “Carlin-like” or otherwise, would have only
developed smaller ore bodies.
Acknowledgements
Paul Martin of GeoPres Pty Ltd is thanked for his redrafting of the figures. Yang Aidong, the General Manager of
the Jianchaling mine is thanked for his support of the
project.
Close
Chapter 15-7
15-7
Source of fluids in the Longquanzhan gold deposits in
the Yishui area, Shandong, China
Huabin Hu, Shuyin Niu, Baode Wang, Aiqun Sun, Chuanshi Xu
The Shijiazhuang University of Economics, 302 Huainan Road, Shijiazhuang, China
Yongfeng Li, Mengwen Li
China University of Geosciences, 29 Xueyuan Road, Beijing, China
Abstract. The Longquanzhan gold deposit, hosted in Archean gneiss
is located along the Tanlu fault zone, on the southeastern margin
of the North China craton. The orebodies occur as veins striking
15°- 18° and dipping SE at 35°–62°. Wall rock alteration types include silicification, pyritization, and sericitization, and chloritization,
calcitization. Metallic minerals in ores are dominated by pyrite. Gold
occurs mainly in the form of electrum. All inclusions are two-phase
(L+V) NaCl- H2O type. The inclusions generally range in diameter
from 2 to 8 µm with a vapour/liquid ratio of 5–90% and mainly 5–
10%. The homogenization temperatures of fluid inclusions in the
Longquanzhan gold deposit are between 108 and 300°C. The icemelting temperatures vary from –2.0 to –8.6°C, at a peak of –2.5 to
–7.0°C. The salinities determined from the ice-melting point of the
fluid inclusions range from 3.39 to 12.39 wt.% NaCl equiv. According to isotope fractionation equation and mean homogenization
temperatures, the δ18O values of the mineralizing fluids are calculated, ranging from –0.28‰ to +4.07‰, showing mixing of oreforming fluids and meteoric waters. The 3He/4He ratios of fluid inclusions in pyrite are 0.14–0.24 Ra, suggesting the crustal source of
ore-forming fluid. The assemblage of alteration minerals, the characteristics of fluid inclusions and stable isotopes indicate that the
Longquanzhan gold deposit belongs to epithermal type deposit.
Keywords. Longquanzhan gold deposit, inclusion, stable isotope,
source of fluid, China
1
Introduction
The Longquanzhan gold deposit is situated approximately
20 km south of Yishui County, Shandong, located tectonically in the Tanlu fault zone in the southeastern margin of the North China craton. The gold deposit, discovered by the Institute of Shandong Geology and Mineral
Resources in 2002, is now being prospected. The previous work of the gold deposit was scarce.
This paper describes the metallogenic setting and geological characteristics of the gold deposit. Fluid inclusion
investigations, S, O and H stable isotope data and He and
Ar isotope data from fluid inclusions are presented. These
data form the basis for an assessment of possible sources
of the ore-forming fluids.
2
Regional geological setting
The strata of the region consist of the basement and cover
strata. The basement rocks are composed of the MesoArchean Yishui Group with a residual zircon SHRIMP U-
Pb age ranging from 2.82 to 3.07Ga (Shen et al 2004), the
Neoarchean Taishan Group-complex with an age range
from 2767 to 2490Ma (Jahn et al. 1988) and trondhjemitetonalite-granodiorite suite (TTG) and Paleopro- terozoic
orogenic granites (Fletcher et al. 1995). The Taishan Groupcomplex is composed dominantly of amphibolite and biotite granulite (leptite) with minor TTG gneisses, which
suffered from medium- to low-grade metamorphism. The
cover rocks comprise the Neoproterozoic Tumen Group
and its overlying Paleozoic strata, lithologically including carbonate rocks and clastic rocks (Shen et al. 2000;
Hu et al. 2004).
Tan-Lu fault zone, which extends NNE for more than
3000 km, constitutes a conspicuous tectonic belt along
the northeastern margin of the Asia continent. In
Shandong province, the Tan-Lu fault zone strikes at 10°to
25° for about 330 km, can subdivided from west to east
into Tangwu-Gegou fault, Yishui- Tangtou fault, AnqiuJuxian fault and Changyi-Dadian fault. The Tan-Lu fault
zone is a sinistral shear zone with a slip about 540 km
and repeated extension (Okay and Sengor 1992; Yin and
Nie 1993). The age of the Tan-Lu fault is open to debate,
assigning to Precambrian (Fletcher et al. 1995), Paleozoic
(Yin and Nie 1993), and Mesozoic (Xu et al. 1987; Okay
and Sengor 1992).
Mesozoic potassium-rich volcanic rocks are distributed mostly in terrestrial down-faulted volcanic-sedimentary basins. They consist predominantly of subalkalineintermediate-basic pyroclastic rocks and lava, as well as
trachybasalt, shoshonitic rocks, determined to be 40Ar/
39Ar plateau ages varying from 114.8 ± 0.6 to 124.3 ± 0.6
Ma (Qiu et al. 2001).
3
Geology of gold deposit
The strata exposed in the Longquanzhan ore district include Cretaceous volcanic- clastic rocks, Neoarchean
gneiss and granite with zircon SHRIMP U-Pb ages ranging from 2.51 to 2.62Ga(Shen et al 2004). The gold deposit hosts in the Neoarchean gneiss in the bottom wall
of the Yishui- Tangtou fault (Fig. 1). Up to now, two
orebodies referred to as the No. I and No. II have been
discovered. Orebody No. I strikes 15° and dips at 35-50°,
with ~1600m long and 0.5-3m thick. Its grades range from
Close
1540
Huabin Hu · Shuyin Niu · Baode Wang · Aiqun Sun · Chuanshi Xu · Yongfeng Li · Mengwen Li
2.05 to 15.3g/t, with a mean of 4.52g/t. Orebody No. II
strikes 18° and dips at 48°–62°, with ~1200m long and
0.84-4.62m thick. Its grades range from 1.08 to 5.48g/t,
with a mean of 1.75g/t (Li et al. 2004).
Wall rock alteration types include silicification,
pyritization, sericitization, chloritization, and calcitization,
of which silicification, pyritization, sideritization are
closely associated with the gold mineralization.
Metallic minerals in ores are dominated by pyrite, accounting for 5-15%, with minor chalcopyrite and galena.
Gangue minerals comprise chlorite, quartz, sericite and
plagioclase.
Gold occurs mainly in the form of electrum, and minor native gold. Gold mineral is gold-yellow in colour,
with a strong metallic lustre, and mainly occurs as grains,
ranging from 0.003 to 0.18mm in size. Microprobe analysis gave the following composition (%) of electrum: Au
67.97, Ag 30.92, Cu 0.59, Fe 0.52.
4
Fluid Inclusion studies
4.1 Samples and analytical methods
Microthermometric measurements were carried out on
a Linkam THMSG 600 programmable heating- freezing
stage (-196 to +600ºC) at the Laboratory of the Faculty of
Geosciences and Mineral Resources, China University of
Geosciences, Beijing. The heating rate was 0.1 to 1 ºC/
min below 10 ºC, whereas the heating rates were about 3
to 5ºC/min at 10 to 31ºC, with a reproducibility of ± 0.1ºC.
The heating rate was 5 and 10ºC/min at higher temperatures (>100ºC), with a reproducibility of ± 2ºC.
4.2 Inclusion types and characteristics
Fluid inclusions were examined in 10 samples from the
gold deposit. There were abundant fluid inclusions in
quartz and calcite of alteration minerals. Measurements
in transparent minerals were typically restricted to primary or pseudosecondary inclusions. All inclusions are
two-phase (L+V)NaCl- H2O type, consisting of aqueous
liquid and vapor bubbles, with a vapor/liquid ratio of 5–
90% and mainly 5–10%. The inclusions generally range
in diameter from 2 to 8 µm, and in a few individual cases
may reach a maximum of 18µm. Most inclusions have
elliptical, rounded, elongated and irregular shapes.
4.3 Microthermometric results
The homogenization temperatures of fluid inclusions in
the Longquanzhan gold deposit are between 108 and
300°C. The ice-melting temperatures vary from -2.0 to 8.6ºC, at a peak of -2.5 to -7.0°C. The salinities determined
from the ice-melting point of the fluid inclusions range
from 3.39 to 12.39 wt.% NaCl equiv (Bodnar 1992). We
obtained corresponding fluid densities between 0.708 and
0.981 g/cm3 by consulting the table of Liu and Shen (1999)
according to the homogenization temperatures and salinities of the aqueous fluid inclusions.
5
Stable isotope studies
5.1 Samples and analytic methods
Four fresh pyrite samples were collected for sulphur isotope measurements, which were selected under the binocular microscope to ensure their purities were over 99%.
Cu2O was used as the oxidizer for the preparation of sulphide samples. Sulphate minerals were purified to pure
BaSO4 by the carbonate-zinc oxide semi-melt method, and
then SO2 was prepared by the V2O5 oxide method. The
SO2 released was measured for sulphur isotopes.
Four samples were selected for helium and argon isotope measurements. Each pyrite sample was picked using a binocular microscope and its purity was over 99%.
Helium and argon isotopes were analyzed at the Stable
Isotope Laboratory, Institute of Mineral Resources, Chinese Academy of Geological Sciences. The analytical procedure is as follows (Mao et al. 2002a).
Close
Chapter 15-7 · Source of fluids in the Longquanzhan gold deposits in the Yishui area, Shandong, China
For analysis of hydrogen isotope, the water in fluid inclusion was released by decrepitation method. Then the
water was reacted with Zn at 400ºC to produce H 2
(Coleman et al. 1982), which was collected in sample tube
with activated charcoal at liquid N2 temperature (Mao et
al. 2002b). All SO 2, CO2, and H 2 were analyzed in a
Finningan MAT 251 mass spectrometer, at the Stable Isotope Laboratory of the Institute of Mineral Resources,
Chinese Academy of Geological Sciences. Analytical reproducibility in this study is ± 0.2‰ for S, O and C isotopes, and ± 2‰ for H isotopes.
1541
matic water and meteoric water and have a tendency to
“drift” to the meteoric water line, showing mixing of oreforming fluids and meteoric waters.
The 3He/4He ratios of fluid inclusions in pyrite are 0.140.24 Ra, which are 5-10 times higher than that of the crust
(0.01-0.05 Ra) (Stuart et al. 1995) but 20-40 times lower
than that of the mantle (6-9 R/Ra), suggesting the oreforming fluid from crust source. The lower 3He/4He ratios of the ore are obviously different from those (3.59.8Ra) from the Wangu gold deposit adjacent to the TanLu fault (Mao et al 2002c), and from those (0.5-5.2Ra)
from the Dongping gold deposit (Mao et al 2003), which
are reported to have involved some mantle-derived fluids during mineralization. 40Ar/36Ar ratios are 289-482,
slightly higher than those of the atmosphere (40Ar/
36
Ar=295.5), indicating the existence of a small amount
of excess argon produced probably by higher radiogenic
40Ar.
Therefore, The assemblage of alteration minerals, the
characteristics of fluid inclusions and stable isotopes suggest that the Longquanzhan deposit belongs to epithermal
gold deposit (Lindgren, 1922).
The sulfur, hydrogen and oxygen, and helium and argon isotopic compositions indicate that ore-forming fluid
originated from lower crust and mixed with deeply circulating meteoric water.
Acknowledgements
This study was supported by the National Natural Science Foundation of China (No. 40272088).
5.2 Results and discussion
The δ34S values of pyrite range from -4.2 to 4.4‰ with a
mean of 1.55‰, suggesting a mantle or lower crust source
of sulphur in the ores.
In the Longquanzhan gold deposit, δ18O values of alteration minerals range from 8.3 to 12.0‰ . The mean homogenization temperature of 290? was obtained by averaging homogenization temperatures of 58 inclusions in quartz
from the Longquanzhan gold deposit. According to the
quartz-water isotope fractionation equation 1000 ln α
= 3.42 × 106 T–2 – 2.86‰ (Zhang et al. 1989, the δ18O values
of the mineralizing fluids were calculated ranging from 1.77
to 4.07). The mean homogenization temperatures of 190?
were obtained by averaging homogenization temperatures
of 90 inclusions in calcite. Using the calcite-water isotope
fractionation equation 1000 ln α = 2.78 × 106 T –2 – 2.89
(O’Neil et al. 1969), the δ18O values of the mineralizing fluids are calculated, ranging from -0.28 to 1.78‰. The δ18Ofluid
values of ore fluids of the Longquanzhan gold deposit are
relatively low, from -0.28‰ to +4.07‰, being notably deviated from the δ18O fluid range (5.5 to 9.5‰) of magmatic
water defined by Sheppard (1986). In the δD vs. δ18Ofluid
diagram (Fig. 2), five data points are plotted between mag-
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Qiu J, Xu X, Luo Q (2001) Potash-rich volcanic rocks and
lamprophyres in western Shandong province: 40Ar-39Ar dating
and source tracing. Chinese Science Bulletin 46(18): 1500-1508
Shen Q, Shen K, Geng Y, Xu H (2000). The constitutents and crust
evolution of Yishui complex, Shandong province. Geological Publishing House, Beijing, 1-179 (in Chinese with English abstract)
Shen Q, Song B, Xu H, Geng Y (2004) Emplacement and metamorphism ages of the Caiyu and Dashan igneous bodies, Yishui
county, Shandong province: zircon SHRIMP chronology. Geological Review 50(3): 275-284(in Chinese with English abstract)
Sheppard SMF (1986) Characterization and isotopic variations in
natural waters. Rev Mineral 16: 165-183
Stuart FM, Burnard PG, Taylor RP, Turne G (1995) Resolving mantle
and crustal contribution to ancient hydrothermal fluids: He-Ar
isotopes in fluid inclusions from Dae Hwa W-Mo mineralisation,
South Korea. Geochimica et Cosmochimica Acta 59: 4663-4673
Xu J, Zhu G, Tong W, Cui K, Liu Q (1987) Formation and evolution of
the Tancheng- Lujiang wrench fault system: a major shear system to the northwest of the Pacific ocean. Tectonophysics 134:
273-310
Yin A., Nie S (1993) An indentation model for the north and south
China collision and the development of the Tan-Lu and Honam
fault systems, eastern Asia. Tectonics 12(4): 801-813
Zhang L (1989) Petrogenetic and minerogenetic theories and prospecting. Press of Beijing Technological University, Beijing, 1-267
(in Chinese)
Close
Chapter 15-8
15-8
The Jinfeng gold deposit: A new mine leading the way
for foreign investment in Guizhou Province, China
Robert P. Ilchik, Phillip J. Uttley, Ross Corben
Sino Gold Limited, Level 8, 17 Bridge St, Sydney, NSW 2000, Australia
Alex Yongming Zhang
Sino Guizhou Jinfeng Mining Limited, Level 11, 1 Yan’an Zhong Road, Guiyang, China
Andrew P. Ham, Paul Hodkiewicz
SRK Consulting, Level 26, 44 Market Street, Sydney, NSW 2000, Australia
Abstract. The Jinfeng is the largest known Carlin-type gold deposit
in the Peoples Republic of China, with an identified mineral resource
of at least 3.5 m oz of contained gold. Jinfeng is a structurally controlled deposit within Triassic turbiditic sediments that overly Permian limestone. This sequence has a multi-phase deformational history dominated by NE-SW compression and to a lesser degree NWSE compression. These events have produced a complex series of
gentle to tight folds, and reactivated thrust and transfer faults. This
provided the setting for gold mineralisation, which occurred late in
the deformational history and is mainly confined to second-order
faults F3 and F2. Gold mineralisation occurs in carbonate- and clayrich rocks. Alteration accompanying gold mineralisation includes
replacement of carbonate minerals by quartz, and deposition of
arsenical pyrite rims to primary pyrite and arsenopyrite. Late in the
mineralisation cycle orpiment and native arsenic were deposited
with minor calcite. Gold is found mainly in the arsenical pyrite rims
and a lesser amount in arsenopyrite. The June 2004 total Mineral
Resource estimate, using a 2gpt Au cut-off, is 20.9 million tonnes at
5.1gpt Au and the total Proved and Probable Ore Reserves are estimated at 11.6 million tonnes at 5.5gpt Au. The project will support
annual gold production of approximately 180,000 ounces once full
production is achieved in 2006. Both open cut and underground
mines will be operated, with initial ore production coming from
the open cut. The designed treatment rate is 1.2 million tpa, with
provision for expansion. The ore at Jinfeng is refractory but responds
well to bio-oxidation and Sino Gold has opted for a BIOX® circuit to
treat a flotation concentrate prior to standard CIL leaching to recover the difficult to liberate gold. Overall gold recovery is expected
to be 85%. The pre-production capital costs for the project are estimated at approximately US$70 million.
Keywords. China, Jinfeng, gold, sediment hosted, Carlin type.
1
The area may have been first exploited last century as
a mercury and arsenic mine for Chinese medicines. Jinfeng
was discovered in 1986 by Brigade 117 of the provincial
Bureau of Geology and Mineral Resources (BGMR) following up on a stream geochemical anomaly. BGMR subsequently drilled approximately 20 km of diamond core
and drove 8 km of underground heading to delineate the
deposit, but beneficiation of the sulphide ore proved problematic. Starting in 2002, Sino Gold began an exploration
program that included more than 45 km of diamond drilling and more than doubled the previous resource.
2
Geological setting
Jinfeng, often referred to as Lannigou, is situated in SW
Guizhou Province, an agrarian area of steep hills and narrow valleys with elevations between 400 and 800 m adjoining rugged limestone karst country. Rifting of the Yangtze
craton during the Precambrian to Cambrian produced a
sedimentary basin which now hosts numerous Carlin-type
deposits. Locally, Triassic turbidites host the vast majority
of gold mineralization. These rocks overly Carboniferous
through Early Triassic limestone which core the N-S elongate Laizhishan dome less than 1 km to the west. The sequence has a multi-phase deformational history dominated
by NE-SW compression and to a lesser degree NW-SE compression. These events have produced a complex series of
gentle to tight folds and thrust and transfer faults, and provided the setting for gold mineralization (Fig. 2).
Introduction
3
The Jinfeng is the largest known Carlin-type gold deposit
in the Peoples Republic of China, with an identified mineral resource of at least 3.5 m oz of contained gold (Fig. 1).
It is currently being explored and developed by Sino Gold
Ltd. Sino Gold holds 82% equity in the Sino-Foreign joint
venture with Chinese partners. Development began in
early 2005, and full production is scheduled for mid-2006.
Open-pit and underground operations will produce approximately 180,000 ounces annually from refractory ore
using the BIOX® process.
Gold mineralisation
Gold mineralisation occurred late in the deformational history and is tightly confined to second-order faults, known
locally as the F3 and F2, which cut the turbidites. These
faults were warped during deformation. The main F3
orebody is a moderately- to steeply-dipping shear zone with
several rolls along the 800 vertical meters it has been explored to date (Fig. 3). This orebody trends N73W, and in
long section plunges moderately-steeply to the ESE. Several important ore domains are present where splays de-
Close
1544
Robert P. Ilchik · Phillip J. Uttley · Ross Corben · Alex Yongming Zhang · Andrew P. Ham · Paul Hodkiewicz
veloped off the F3 late in the deformational history. Mineralization in the F3 is open to the E and at depth. The F2
(N20E, 85E) crosscuts the F3, and is only mineralized near
this intersection. Further to the W, only scattered bits of
mineralization are encountered in local shear zones.
Gold mineralization occurs in carbonate- and clay-rich
fine sand facies turbidite rocks. Carbonate minerals, both
cements and veins that formed earlier in the deformational
history, were replaced by quartz. Accompanying this main
stage is the deposition of arsenian pyrite rims to primary
pyrite and arsenopyrite. Late in the mineralization cycle
orpiment and native arsenic were deposited with minor
calcite. Gold is found mainly in the arsenian pyrite rims
and a lesser amount in arsenopyrite.
Gold and mercury are tightly confined to fluid conduits,
whereas arsenic and antimony are disseminated up to 30m
from these structures. Host rocks contain high concentrations of reactive iron, suggesting that sulphidation was the
main mechanism for gold precipitation.
4
Resource development
Drilling, completed since the June 2004 resource estimate,
continued to produce new intercepts that fall within the
open cut design. These intercepts are related to both foot-
wall and hanging wall splay faults not intersected by previous drilling (e.g. 21.7m @ 7.6gpt Au down-hole in HDDS101). Additional drilling is expected to increase the amount
of gold that is recoverable from the designed open cut.
Since acquiring the project, Sino Gold has spent over
US$10 million in drilling and underground exploration of
the deposit to produce Mineral Resource and Ore Reserve
estimates in accordance with JORC, in preparing a Bankable Feasibility Study and completing an Optimization Study.
It has taken almost four years for Sino Gold to successfully progress the world-class Jinfeng Project to the
construction and development stage. Construction
earthworks began in March 2005. Sino Gold is committed to integrating safety and environmental considerations
into all phases of the project: its design, its construction,
its operation and its ultimate closure. The utmost priority is placed on the safety and health of employees, contractors and visitors and the protection of the natural
environment. The promotion of safe work habits receives
the highest priority.
In early 2004, a commitment was made to compensate
residents living in the proposed mine area for relocating.
A new village area and market place is being built by Sino
Gold to replace the existing facility that was also affected
by the mine’s construction.
Close
Chapter 15-8 · The Jinfeng gold deposit: A new mine leading the way for foreign investment in Guizhou Province, China
Regular meetings were held with community leaders
in the Sino Gold community centre and in the local villages to explain the progress and impact of the operation
and to receive feedback on community concerns. A water
supply was provided to the nearby Lannigou village. In
total, 360 local people will be trained in technical and
administrative skills over a 12-month period.
County and Prefecture government officials have been
very supportive of the project and were instrumental in
undertaking land measurement for compensation for the
70 hectares of land required by the operation.
The Jinfeng Bankable Feasibility Study was completed
in March 2004, but exploration drilling continued to discover additional mineralisation and is having a significant effect on the project evaluation. Subsequently, an
Optimization Study was completed following an update
of the Mineral Resources estimate in June 2004. Using
this resources estimate, the Optimization Study estimated
Ore Reserves from mining and treatment operations using a gold price of US$350/oz.
The June 2004 total Mineral Resource estimate, using
a 2gpt Au cut-off, is 20.9 million tonnes at 5.1gpt Au and
1545
is more than double the original Chinese resource estimate at the time Sino Gold became involved with the
project. Total Proved and Probable Ore Reserves are estimated at 11.6 million tonnes at 5.5gpt Au. The project
will support annual gold production of approximately
180,000 ounces once full production is achieved in 2006.
At this rate, the operation’s life will be at least 12 years
with cash operating costs estimated to be approximately
US$183/oz.
Both open cut and underground mines will be operated, with initial ore production coming from the open
cut. Having a 6-year life, with additional drilling, the open
cut is expected to produce 6.5 million tonnes at 5.1gpt Au
at a strip ratio of approximately 13:1. The underground
mine is scheduled to begin ore production in the latter
part of 2012 and is expected to produce 6.9 million tonnes
at 5.7gpt Au in total.
The designed treatment rate is 1.2 million tpa, with provision for expansion. The ore at Jinfeng is refractory with
most of the gold locked up with pyrite. It responds well to
bio-oxidation and Sino Gold has opted for a BIOX® circuit
to treat a flotation concentrate prior to standard CIL leaching to recover the difficult to liberate gold. Overall gold recovery is expected to be 85%. The pre-production capital
costs for the project are estimated at approximately US$70
million, with a more precise estimate being prepared as a
result of the design work done by Ausenco and NERIN.
The underground workings will not be accessed from
the open cut and this allows the option of accelerating
development of the underground mine. As Sino Gold has
a very positive view on the geological endowment of the
Jinfeng area, a scoping study was completed for a Phase 2
expansion to 1.8 million tonnes per annum, adding 50%
to the treatment capacity. This scoping study suggests
expansion capability to approximately 300,000 ounces per
annum with mining of the underground and open pit
occurring in parallel. The estimated capital cost for this
expansion is approximately US$14 million.
Ongoing exploration activity at Jinfeng is being directed
at locating resources within trucking distance of the future Jinfeng plant to supplement ore supplies and sustain
a Phase 2 expansion.
Now that construction has commenced, site activity
will rapidly increase during 2005 as China’s second largest gold mine is built. Sino Gold is eagerly anticipating
2006, which will be the year when gold production commences.
Acknowledgements
The contributions of all the other geologists who have
worked on Jinfeng are acknowledged. Sino Gold Limited
is thanked for permission to publish. Paul Martin of
GeoPres Pty Ltd is thanked for his redrafting of the figures.
Close
1546
Robert P. Ilchik · Phillip J. Uttley · Ross Corben · Alex Yongming Zhang · Andrew P. Ham · Paul Hodkiewicz
References
Hofstra AH, Leventhal JS, Northrop HR, Landis GP, Rye RO, Birak DJ,
Dahl AR (1991) Genesis of sediment-hosted disseminated-gold
deposits by fluid mixing and sulfidization: Chemical-reactionpath modeling of ore-depositional processes documented in the
Jerritt Canyon District, Nevada: Geology 19: 36-40.
Ilchik RP, Barton M (1997) An amagmatic origin of Carlin-type gold
deposits: Economic Geology 92: 269-288.
Li Z, Peters SG (1998) Comparative geology and geochemistry of
sedimentary-rock-hosted (Carlin-type) gold deposits in the
People’s Republic of China and in Nevada, USA: USGS Open-File
Report 98-446, 157 p.
Peters SG (2002) Geology, geochemistry, and geophysics of sedimentary-hosted Au deposits in P.R. China: USGS Open-File Report:
02–131, 403 p.
Seward TM (1973) Thiocomplexes of gold and the transport of gold
in hydrothermal ore solutions: Geochimica et Cosmochimica Acta
37: 379-399.
Woitsekhowskaya MB, Peters SG (1998) Geochemical modeling of
alteration and gold deposition at the Betze deposit, Eureka county,
Nevada: in Tosdal, R.M. (ed), Contributions to the gold
metallogeny of Northern Nevada, USGS Open-File Report 98338, p. 211-222.
Zhang X (1997) The geology and hydrothermal evolution of sediment-hosted gold deposits in Southwest Guizhou Province, PRC:
Imperial College, London, unpublished Ph.D. dissertation, 273 p.
Zhang X, Spiro B, Halls C, Stanley CJ, Yang K (2003) Sediment-Hosted
Disseminated Gold Deposits in Southwest Guizhou, PRC: Their
Geological Setting and Origin in Relation to Mineralogical, Fluid
Inclusion, and Stable-Isotope Characteristics: International Geology Review, vol. 45, pp. 407-470(64)
Close
Chapter 15-9
15-9
An overview of diamond exploration in the North
China Craton
Michael Michaud
China Diamond Corp.1724 Hyde Park Road,London, Ontario,N6H 5L7 Canada
Keywords. Diamond exploration, kimberlite, North China Craton
1
Introduction
China’s history of diamond exploration and production extends over 40 years, initially concentrating on the discovery
of alluvial deposits and later the kimberlitic sources. Diamond production from China currently totals 90,000 carats/
annum from one kimberlite diamond mine, namely China
Diamond Corp.’s 701 Changma Mine in Shandong Province
that has operated for the past 34 years. Previously, between
1987 and 2002, additional kimberlite diamond production
came from the Wafangdian Mine in Liaoning Province, producing approximately 60,000 carats/annum. To date, over 20
diamondiferous kimberlite deposits have been discovered,
several of which have been mined on a very small scale.
China is underlain by three large Archean cratons, namely
the North China Craton, also known as the Sino-Korean
Craton, and the Yangtze and Tarim Cratons. In all three of
the cratons, several alluvial diamond deposits have been
discovered; however, to date, only two diamondiferous
kimberlite deposits have realized commercial production,
those being located in the North China Craton (Fig. 1). This
is due in part to the difficult terrain, lack of adequate access, and extensive soil cover in the Yangtze and Tarim Cratons, comparatively.
The North China Craton is considered prospective for
diamonds due to the fact that Ordovician-aged kimberlites
have traversed the Archean mantle with the potential to be
laden with diamonds. However, numerous tectonic episodes
have modified the underlying lithosphere since the Ordovician emplacement of the kimberlites, so that selected geophysical data would be misleading as a prospecting tool to
identify regions with cratonic physical properties.
2
Regional geology
All the so-called cratons in China are not strictly cratons;
since they have undergone multiple tectonism since the late
Paleozoic. The tectonic framework of China is dominated
by three global orogenic systems, the Central-Asian or PaleoTethyan, the Circum-Pacific and the Tethys–Himalaya systems. The Mesozoic–Cenozoic Circum-Pacific orogenic belt
in eastern China and the Tethys–Himalaya system in southwestern China are the products of the subduction of the
Pacific Ocean floor beneath China, and the indentation of
the Indian continent into Eurasia, respectively. The area is
underlain by numerous fold belts that are dominantly products of subduction and accretion of oceanic complexes, and
were the focus of deformation in Paleozoic–Mesozoic cratonic collisions during final ocean closures.
The North China Craton is comprises early Archean
to Early Proterozoic basement rocks overlain by Middle
Proterozoic to Cenozoic cover. The three major cratons
in China (North China, Tarim, and Yangtze) underwent
at least three orogenies during the Archean, widely-termed
the Qianxian (ca. 3.2 Ga), Fuping (ca. 2.8 Ga), and Wutai
(ca. 2.5 Ga). During these orogenies, rock units experienced extensive greenschist to granulite facies metamorphism, intensive migmatization, and widespread
magmatism. Subsequently, the Precambrian sequences
were locally uplifted and exposed, especially along the
margins of the North China Craton during a series of
Phanerozoic orogenies. The primary orogenies are defined as between 600 and 405 Ma as Caledonian, 405 and
270 Ma as Variscan, 270 and 208 Ma as Indosinian, 208
and 90 Ma as Yanshanian, and <90 Ma as Himalayan. These
collisions may have coincided with development of the
Tanlu fault system, extending over 4,000 kilometers, which
was continually active along the eastern margin of China
during the middle and late Mesozoic Yanshanian orogeny. The Tanlu fault is considered by many to have resulted in a 500 kilometer displacement of the Wafangdian
Mine (Fuxian kimberlite field) from the 701 Mine
(Mengyin kimberlite field). In the Yanshanian (210–90
Ma) and Himalayan (<90 Ma), the oblique subduction of
the Izanagi–Pacific basin plates under the eastern edge
of China led to the formation of the NNE-trending
Yanshanian magmatic belts and faults along the Pacific
continental margin, considered to one the of the most
important metalogenic orogenies in China.
A comprehensive study using “4-D lithosphere mapping” was completed by Griffin, et. al. in 1997. The main
results of this study are summarized as follows:
The Lithosphere-Asthenosphere Boundary about 500
Ma ago was at ~180-200 kilometers deep;
An Archean lithosphere ~200 km thick existed under
the eastern Sino-Korean Craton up to Late Ordovician
allowing the emplacement of diamondiferous kimberlite pipes and dikes;
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Michael Michaud
Geophysical data show a present-day thin lithosphere
(60 -120 km) and high geothermal gradient under the
North China Craton implying the replacement of 80 140 kilometer thick section of the Archean lithosphere
with “oceanic” lithosphere since the Ordovician;
The replacement of the lithosphere is interpreted to
be a result of thermal erosion of the lithosphere linked
to two episodes of basin development and rifting associated with subduction.
3
The kimberlitic bodies are typically characterized by
porphyritic kimberlite with a matrix of serpentinized olivine and phlogopite and phenocrysts of olivine, biotite and
pyrope. The accessory minerals include ilmenite, chromite,
and chrome diopside. The breccia rock fragments include
local country rock inclusions of limestone and gneiss, and
mantle eclogite and garnet lherzolite. The mineral resources
for different deposits, and for that matter between different
pipes within a deposit, varies considerably in grade, diamond size distribution and quality, as indicated in Table 1.
Kimberlite emplacement
4
The emplacement of the kimberlite pipes and dikes in
the North China Craton occurred at several times, ranging from 450- 480Ma in age to a much later Tertiary age,
the former being diamondiferous and include the
kimberlites at the 701 Mine and Wafangdian Mine. The
kimberlitic bodies appear to be related to deep mantle
structures that have been further controlled by near-surface crustal faults. Many of the kimberlite pipes and dikes
in the area occur at or near the intersection of major westnorthwest and north-northeast trending geological structures along the Tanlu Fault trend. The kimberlites form
both narrow and often discontinuous dikes that are connected to larger, more ellipsoidal pipes (Figure 2).
Discussion
The North China Craton is considered prospective for
diamonds due to the fact that Ordovician-aged kimberlites
have traversed the Archean mantle with the potential to
be laden with diamonds. However, numerous tectonic
episodes have modified the underlying lithosphere since
the Ordovician resulting in the replacement of an approximately 80-140 kilometer thick section of the Archean lithosphere with “oceanic” lithosphere. The Ordovician is related to several episodes of basin development and rifting associated with plate subduction.
The thinning of the crust in the North China Craton
has important implications for diamond exploration. Geo-
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Chapter 15-9 · An overview of diamond exploration in the North China Craton
physical data would be of little use as a prospecting tool
to identify regions with cratonic physical properties, and
also, in the determination of the age of kimberlites that
had the potential to “tap” Archean lithosphere. Great care
must be taken to unravel the timing and nature of these
tectonic events in order to assist any exploration efforts.
1549
Reference
Griffin WL, Andi Z, O’Reilly SY, Ryan CG (1997) Phanerozoic evolution of the lithosphere beneath the Sino-Korean Craton. In: Mantle
Dynamics and Plate Interactions in East Asia (Flower, M., Chung,
S.L., Lo, C.H. and Lee, T. Y. eds) American Geophysical Union Spec.
Publ., in press 7/96
Close
Close
Chapter 15-10
15-10
Metallogenic dynamics and model of cobalt
deposition in the eastern Kunlun Orogenic Belt,
Qinghai Province
Tong Pan
Qinghai Bureau of Nonferrous Metals Exploration, 5 Jianguo Road, Xining 81007, China
Caisheng Zhao
Institute of Mineral Resources, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, Beijing 100037, China
Fengyue Sun
College of Earth Sciences, Jilin University, 2199 Jianshe Road, Changchun 130026, China
Keywords. Metallogenic dynamics, model of cobalt deposit, Eastern
Kunlun orogenic belt, Qinghai Province
1
Introduction
Recently discovered cobalt is an important mineral species in the eastern Kunlun Orogenic Belt and has shown
favorable prospecting prospects, high tenor and large scale
reserves. To date, three cobalt deposits have been discovered: that is, Kendekeke and its periphery cobalt-bismuthgold deposit, Tuolugou cobalt-gold deposit and Dulenggou
copper-cobalt deposit. Cobalt has the characteristics of
being heat-resistant, wear-resistant, high strength and
strong magnetism. Furthermore, its alloy and alloy steel
are important additives which are indispensable to aviation, electrical appliances and the chemical industry. There
are associated cobalt deposit and independent cobalt deposit in this orogenic belt. What are the ore-controlling
characteristics and how about their ore-forming
metallogenic dynamic mechanism and geology of mineral deposit? The dissertation briefly discusses these scientific problems.
2
Regional geology of the eastern Kunlun
Orogenic Belt
The eastern Kunlun Orogenic Belt represents the western part of China’s central orogen, and is located in the
southern margin of Qaidam massif. The belt has undergone polycyclic complex orogenic processes, polycyclic
ocean-continent transition and complex intercontinental evolution after the collision. As a result, typical structure-magma-sedimentation occurred. From north to
south, the eastern Kunlun orogenic belt can be divided
into the Kunbei back-arc basin, Kunzhong basement uplift and granitic belt and Kunnan composite belt. The predominant strata include the Precambrian, Ordovician,
Carboniferous-Permian and Triassic. E-W fracture zones
have formed in the eastern Kunlun orogenic belt since
the Paleozoic due the influence of three regional faults.
Extensive magmatism developed and different epoch rock
assemblages demonstrate the plate subduction-collision
and evolution of a polycyclic ocean.
Metamorphism drove element redistribution and enrichment in the eastern Kunlun orogenic belt. For the significant contribution of metamorphism to mineral deposit is that it can supply metamorphic fluids, remobilize
the mineral elements and extract the mineral elements
from source beds.
Regional gravity and aeromagnetic anomaly present the
N-W orientation in the Western part, E-W orientation in
Middle part and N-E orientation in Eastern part. Gravity
anomaly reflects E-W and N-W orientation gradient belt
and mineral resources of non-ferrous metal have close relationship with the N-W orientation gravity and aeromagnetic anomaly. Along the gravity gradient belt and periphery of the aeromagnetic anomaly, some commercial nonferrous metal deposits have been discovered. Ore bodies
are commonly hosted in anomaly intersections. Eastern
Kunlun mineralized belt is located in an active fractured
zone, lithospheric thinning and has a coincident relationship with strong earthquake centers. Mineral deposits
formed along the low velocity zone and the transitional belt
between the high velocity zone and low velocity zone.
Volcanic rocks of Eastern Kunlun orogenic belt can be
divided into four series: pre-Xingkai, Caledonian, Variscan
and Indosinian-Yanshanian. Pre-Xinkai volcanic rocks are
composed of basaltic lava of Wanbaogou group. Chemical components of volcanic rocks wholly belonged to
subalkalic series. Characteristics of geochemistry and sedimentation formation indicated that the forming environment was oceanic volcanic island. Caledonian volcanic
rocks include Nachitai group and Tanjianshan group. Furthermore, volcanic rocks of Tanjianshan group are bimodal volcanic rocks composed of basic basalts and intermediate-acidic basalts. Geochemistry shows the
Tanjianshan group developed in a back-arc basin tectonic
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Tong Pan · Caisheng Zhao · Fengyue Sun
environment. Nachitai group contributed some limestone
and siliceous rocks that formed in deep water. Variscan volcanic rocks are composed of the Maoniushan, Dagangou,
Halaguole and Haoteluowa group. Calcalkalic volcanic rocks
of early Carboniferous Halaguole group are rocks developed in an island arc or active continental margin. Halaguole
group of Kunnan composite belt develop tholeiitic basalt
series and Calcalkalic series characterized by magmatic arc
showing its formation have genetic relation with the northward subduction of Bayan Har ocean.
Exhalative sedimentation formations are developed extensively in Eastern Kunlun orogenic belt. Because of the
influence of the different metallogenic geological-structural
setting, some special submarine hydrothermal exhalation
sedimentation formations were formed. For example,
Kendekeke ore district located in Qimantage aulacogen developed siliceous rocks-bearing Sedex formation. However,
Tuolugou ore district located extensional oceanic setting
developed siliceous albitite-bearing volcanic clastic debris
sedimentation formation. Dulenggou copper deposit is
formed in a subduction back-arc of Bayan Har ocean and
developed Calcalkalic series magmatic arc.
3
Geodynamic evolution of the eastern Kunlun
Orogenic Belt
Based on observations made by previous researchers and
our own investigations, the geological history of the orogen
can been divided into three stages, i.e. pre-Caledonian,
Caledonian and Indochinese-Himalayan.
Pre-Caledonian evolution includes formation of
Precambrain platform, breakup and convergence of Proterozoic paleocontinent. Wanbaogou oceanic bassalts, which
are important to understand the tectonic evolution, were
formed in late Proterozoic. The ocean plate of the ProtoTethys began to be consumed by northward subduction to
Qaidam massif along the location of the present Kunzhong
falut in early Paleozoic, and the structural framework of
Kunbei and Kunnan formed. With the development of the
subduction, a trench formed in the sourthern margin of
Qaidam massif. Active continent margin was formed between the Kunzhong fault and Kunbei fault, but a back arc
basin formed in Kunbei belt. Bimodal volcanic rocks were
distributed extensively. By that time, a trench-arc-basin system was developed in the southern edge of Qaidam
massif.Nachitai group, which is composed of volcanic clastic rocks and carbonatite formation was formed in the basalt plateau after formation of the Wanbaogou oceanic basalt and before collision with Qaidam massif. In early middle
Silurian, siliceous albitite formed in extensional tectonic
setting of Wanbaogou oceanic basalt plateau. In late
Caledonian, Wanbaogou plateau basalts were collaged to
the Qaidam massif.
According to Luo et al. (1990), the late Paleozoic volcanic rocks formed in an Andean-type continental mag-
matic arc. The oceanic crust was directly subducted downward to the continent without island arc formation
The Hercynian batholiths, are the most widely developed intrusives in the orogenic while early Indochinese
granites are mostly stock-shaped and mainly distributed
in Kunnan belt. Based on petrochemical data, it is recognized that the granites of this stage belong to subduction
and syncollisional types. Since the late Indochinese stage,
intensive crustal-mantle reaction occurred, which lead to
the formation of a series of widely distributed mafic-ultramafic intrusives. The tectonic regime transformed from
compressional orogeny to extensional liosphere thinning,
which coincided with the beginning of the breaking up
of the supercontinent Pangea. The tectonic regime transformation controlled the formation of mantle-derived,
mantle-crustal hybrid magmatic activities and a large
number of hydrothermal ore deposits in late Indochinese.
4
Characteristics and model of cobalt deposition
in the eastern Kunlun Orogenic Belt
Kendekeke Co, Bi and Au deposit: This deposit developed in the early Paleozoic back-arc basin of the Kunbei
fracture zone. With the northward subduction of seamounts, the back-arc basin and submarine hydrothermal exhalation sedimentation ore-bearing formation
formed. Submarine hydrothermal exhalation sedimentation formed siliceous rocks together with pyrites, pyrrhotites, gel pyrites and other Co, Bi, Au and Cu multiple
ore-forming elements. Because of the short life of the
active basin, thermal influence was relatively minor; the
hydrothermal sedimentation provided important oreforming materials for the later mineralization. Hercynian
orogenic activities enriched the mineral elements again.
Large scale mineralization developed in Mesozoic era and
is the predominant mineralization stage for the
Kendekeke deposit. Indosinian-Yanshanian magma
brought strong thermodynamics condition and hydrothermal replacement. Tuolugou Co deposit: Bayan Har
Ocean was located in the southern part of Eastern Kunlun
orogenic belt entered the oceanic subduction phase after the Paleozoic extension. Metallic elements were accumulated by hydrothermal activities caused by seeping
of seawater and formations bearing Co and Au. Modified mineralizations and deformation of fold and shear
developed during Yanshanian-Himalayan thrusting.
There were extensive structural deformation and replacement and no large scale magmatic intrusions in Kunnan
belt similar to the paleozoic Kunzhong belt. Primary
stratifications were replaced by penetrative foliations.
Mineralized siliceous albitite were deformed and reoriented and characteristics of veinlike deposits were generated. Later phase structures developed intensively and
cut the original mineralization belt and formed diverse
uplift and denudation.
Close
Chapter 15-10 · Metallogenic dynamics and model of cobalt deposition in the eastern Kunlun Orogenic Belt, Qinghai Province
An oceanic basalt plateau was produced by a mantle
plume in the Pro-Tethys ocean in the Precambrian and hydrothermal activities developed extensively. With the rift
extending downward to the deep crust or upper mantle,
basic vocanics were deposited widely. Large scale hydrothermal sedimentation and submarine exhalation were active for a long time. Co, Cu and others metalic elements
from Archean formations were remobilised into the sea basin
and accumulated and deposited in the hydrothermal vents.
Acknowledgements
This study is financially supported by China Geological
Survey project (200110200021 and 200310200012).
1553
References
Kuang J, Sun FY, Chen GH (2003) Geological features and genetic
type of Kendekeke Co,Bi,Au deposit in Qinghai Province[J].
Jouranal of Jilin University(Earth Science Edition) 33(supp.): 4752 (in Chinese with English abstract)
Pan T, Ma MS, Kang XR (2001) Implication of ore prospecting breakthrough for Co and polymetal deposit in Kendekeke and its periphery, Eastern Kunlun[J]. Chinese Geology 28(2): 17-21
Pan T, Sun FY (2003) The mineralization characteristic and prospecting of Kendekeke Co-Bi-Au deposit in Dunkunlun, Qinghai
Province [J]. Geology and Prospecting 39(1): 18-22 (in Chinese
with English abstract)
Qian ZZ, Tang ZL, Li WY (2003) Metallogenic regularity of QinlingQilian-Kunlun metallogenic domain in Paleozoic[J]. Northwestern Geology 36(1): 34-40 (in Chinese with English abstract)
Close
Close
Chapter 15-11
15-11
A review of gold exploration in the Tulasi Area,
Xinjiang Uygur Autonomous Region, China
Peng Zhang
WMC Resources (China) Pty Limited, Beijing, China
Keywords. WMC, gold exploration, activity, Tulasi, Xinjiang
Abstract
In August 1997 WMC Resources Limited (“WMC”) entered
into a joint venture agreement (WMC 75%, Chinese partner 25%) with No. 1 Exploration Party of Xinjiang BGMR
and the National 305 Project, thus establishing the Xinjiang
Hua Ao Exploration and Mining Venture (Hua Ao JV). The
objective of the joint venture was to explore for a world
class gold deposit in the Tulasi area, north of the city of
Yining in the Xinjiang Uygur Autonomous Region.
Covering 715 km2, the Tulasi project area is host to significant epithermal mineralisation associated with termination of an Early Carboniferous continental margin magmatic arc. Numerous occurrences of gold mineralisation,
and some of base metal (Ag-Pb-Zn) mineralisation, are distributed throughout the area. In two areas excised from the
centre of the project area, significant deposits of low
sulphidation epithermal style mineralisation, known as the
Arxi gold deposit and the Towerbeck gold prospect, have
been previously discovered. On Hua Ao JV tenements, the
only significant low sulphidation epithermal system
recognised was the base metal rich (Ag-Pb-Zn), but gold
poor, Tulasu vein. The majority of known mineralisation
on Hua Ao JV tenements is of medium-high sulphidation
epithermal style according to PIMA analysis, represented
by Jinxi-Yelmand prospect which hosts broad zones of low
grade gold mineralisation (tens of metres thick and with
potential for continuity on the scale of >1km). Mineralisation
is hosted by shallow-dipping clastic units, dominantly conglomerate and sandstone, that lie above a series of Ordovician and Devonian carbonate units, and below a felsic pyroclastic unit. The greater permeability of the clastic units
has favoured channelling of hydrothermal fluids along this
horizon.
The first exploration stage was to conduct project-scale
systematic exploration in search of major zones of
mineralisation that may have escaped previous recognition.
This exploration, comprising targeting, stream sediment
geochemistry, reconnaissance geologic mapping and
rockchip sampling and soil geochemistry, identified coincident geochemical, geophysical and geological anomalies.
The second exploration stage was to advance prospectscale exploration at the Jinxi-Yelmand prospect in expec-
tation of making a quick discovery of a world class gold
deposit. Detailed mapping, dipole-dipole IP geophysics,
and diamond drilling were undertaken at the JinxiYelmand prospect. This work indicated that the
mineralised system is extensive, possibly extending over
an area of 14km2, with a “high grade” core possessing
dimensions of about 1.5km by 1km. Gold grades in this
“high grade” core appear to average only about 1.0 g/t,
and metallurgical testing indicates that the ores are refractory and not amenable to simple heap leach gold extraction. The grades are well below the 3.5-3.8 g/t required
to make this prospect a world-class opportunity by economic modelling.
Life of the Tulasi project covered five years in four
stages: reconnaissance stage 1997-1998; diamond drilling stage 1999; retargeting stage of the project area in
2000 and the project termination stage in 2001. Despite
the conclusion that the Tulasi project area does not contain a world class opportunity for the Hua Ao JV, it was
regarded as having been technically successful. As the first
foreign-Sino exploration cooperation between WMC and
the local partners in the Xinjiang Uygur Autonomous
Region, it was a new experience for all parties. Excellent
cooperation, modern technology and milestone-driven
approach enabled the systematic evaluation of the Tulasi
project area.
References
Begg GC (2001) Tulasi Project Targeting Exercise, March 2000. Unpublished WMC Report
Begg, GC, Carver R, Zhang P, Wang LP, Cui MP (2001) Final Technical report on Tulasi Project, Xinjiang Autonomous Region Of
China, unpublished WMC report
Hayward N, Zhang G (1998) Structure Interpretation for the Tulasi
Project, NW China. Unpublished WMC Report.
Mu R, Tian C, Yang F (1995) Mineralisation patterns and targeting in
flanking regions of Arxi gold deposit in Yilin, Xinjiang: Publication
of 305 Project Office of Xinjiang Uygur Autonomous Region, 248
Qi Shu-ji (1999) The Tectonic Characteristics Of Tulasu Vocanic Basin in Yining and its relation to gold mineralization, Xinjiang
Geology, Jun 1999, vol.17. No.2, p121-128
Sengor AMC, Natal’in BA, Burtman VS (1993) Evolution of the Altaid
tectonic collage and Palaeozoic crustal growth in Eurasia. Nature, v.364, pp.299-307
Xiao L (2000) A Study of Fractal Nature of Gold Deposits Distribution and Gold Metallogenesis of Jinxi-Yelmand Prospect, Tulasi
Basin, North-western Tianshan Belt. Unpublished PhD thesis.
China University of Geosciences (Wuhan)
Close
Close
Chapter 15-12
15-12
Analyzing metallogenic conditions and exploration in
the Mian-Lue-Kang tectonic belt, Shannxi and
Sichuan provinces, China
Ren Xiaohua
Faculty of Geosciences and Land Resources, Chang’an University, Xi’an 710054; and Bureau of geological exploration for
nonferrous metals in northwest China, Xi’an 710054, China
Wang Ruiting
Bureau of geological exploration for nonferrous metals in northwest china, Xi’an 710054; and Faculty of geosciences and
resources, China University of Geosciences, Beijing, 100083, China
Li Furang, Wang Junyi
Bureau of geological exploration for nonferrous metals in northwest china, Xi’an 710054, China
Mao Jingwen
Faculty of Geosciences and Resources, China University of Geosciences, Beijing, 100083; and Institute of mineral resources,
Chinese Academy of Geological Sciences, Beijing, 100037, China
Wang Xiaohong
Faculty of Geosciences and Land Resources, Chang’an University, Xi’an 710054, China
Keywords. Mian-Lue-Kang tectonic belt, ophiolite, tectonic mélange,
metallogenic condition, exploration prospect
The Mian-Lue-Kang tectonic mélange belt is located in
Mianxian County, Lueyang County in Shannxi Province,
and Kangxian County in Gansu Province. It represents
an important part of a plate suture belt recently revealed
in the south margin of Qinling orogenic belt. It forms a
narrow belt 85 km from east to west, and 10 to 15 km
from south to north. The belt extends to Wenxian County
in the west and reaches Animaqing; it also approaches
Fangxian County Hubei Province through Gaochuan to
the east, and forms a divisional regional tectonic belt for
Qinling area that is parallel with Shangdan ophiolite
stucture melange in the northern Qinling.
With the recent development of multi-discipline studies on Qinling orogenic belt, basic research about the MianLue-Kang tectonic belt has made considerable progress
in aspects of composition, tectonic nature, temporal and
spatial evolution regularities, and its dynamic character
(Zhang et al. 1996, 2001). Metallogenic geological understanding for the belt has also improved but some issues
regarding metallogenic conditions and metal ore-forming processes for this anomalous region remain unresolved. Following exploration achievements through recent land and resources surveying in the belt, this paper
analyzes primarily the metallogenic conditions and exploration potential for Mian-Lue-Kang tectonic belt, combined with geological reconnaissance practise. The tectonic belt comprises of a series of parallel, different character faults, with all microlithons divided by nappe shear
faults and decollement faults to form a tectonic network
that extends in east west direction (Fig. 1). Schistosity
zones dominated by S1 deformation foliation mainly exist in volcanic sedimentary rocks. Shear deformation between hard and soft rock interfaces plays an important role
in multi-metals mineralization. Besides a divsion of stratigraphy in the Archean Group (Yudongzi microlithon), the
Sinian system (Xianggongshan microlithon) was deformed
during the Indosinian-Yanshan main orogenic period,
with sedimentary rocks from Paleozoic era metamorphosed to phyllite, and greenschist in epimetamorphic
phase (Tao et al. 1993).
Mian-Lue-Kang tectonic belt underwent an evolution of
extensional splitting in initial stages and subduction and
collision in later stages. Under the conditions of primary
extension, a deep tectonic system generated extensive
volcanics that contained metallogenic materials to supply
abundant sources for subsequent ore-forming processes.
About 90 forming processes. percent of host wall rocks for
gold and multi-metals deposits are volcanic rock, which
shows the influence of the extensional rift structure on ore.
The formation of tectonically altered rock typed gold
deposit relates to stripping the shear belt between basement and overburden of Archean and Proterozoic groups;
syntectonic ultrabasic and basic intrusion activity are the
main thermodynamic conditionss for metallogenesis for
gold formation (for example Jianchaling gold deposit;
Wang et al. 1996, 2000). Metallogenic elements (As, Sb and
Pb) anomalies and brittle and ductile shear structures
are geochemical and tectonic marks for metal deposits
emplaced in the belt.
Close
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Ren Xiaohua · Wang Ruiting · Li Furang · Wang Junyi · Mao Jingwen · Wang Xiaohong
Mian-Lue-Kang tectonic belt also hosts tectonic
ophiolite belts through the evolution of a Paleozoic rift
to limited ocean basin to converging orogeny. The composition of ophiolites chiefly include epidote albite schist,
chlorite sericite schist (phyllite), chlorite actinolite schist,
quartz sericite phyllite, silic rock, slate, serpentinite, mafic magnesite rock, talc magnesite rock, diabase, and gabbro, which constitute different nature tectonic microlithon
in big and small hybrid ways.
On the basis of petrologic results of volcanic rock
microlithons, the geochemistry and petrochemical features of Jinjiahe microlithon indicate that its protolith was
a island arc volcanic rock. The content of SiO 2
(Ø(SiO2) = 46.65) and A12O3 (A12O3)=15.38) are lower
than that of MORB, and its ω(TiO2), ω (Fe2O3), and ω(FeO)
are also low, moreover, low K2O content reflects Jinjiahe
microlithon formed in an island arc environment. REE
analysres for basic and intermediate basic volcanic rock
of Jinjiahe and Guandimen microlithons indicate that
there exist two types rock, one depleted REE, its (La/Yb)
value is 0.3 to 0.36, (Ce/Yb) 0.33 to 0.42 (La/Sm) 0.55 to
0.83, and ΣNd(t) 6, which approach that of N-typed MORB,
the other enriched LREE, its (La/Yb) value is 1.84 to 4. 70,
(Ce/Yb) 1.82 to 3.38, (La/Sm) 2.79 to 4.75, which have the
character of typical VBA basalt.
The belt is an important section with anomalies of Au,
Ag, Pb, Zn, Cu, As, and Sb in Mian-Lue-Yang metal de-
posit cluster field, where Au distributes in the west and
Ag (Pb - Zn) in the east. There are six 10 km long stream
sediment anomalies of Au and associated As, Sb, and Hg
in Ganheba-Jinjiahe region. Three parallel mineralized
strips have been delineated by ravine soil secondary halo
densified method in Ganheban anomaly, and a 30 t gold
resource has been identified in the centre mineralized
strip; at the same time, the other two mineralized strips
still have good prospecting potential.
References
Tao HX, He YY, Wang QQ (1993) Tectonic evolution history of north
margin in Yangzi plate. Xi’an: Northwest university press, 1-133
Wang RT, He Y, Wang X (2000) Probe into the metallogenic mechanism of Jianchaling large gold ore deposit. Northwest Geoscience
21(1): 19-26(in Chinese with English abstract)
Wang X, Tang RY, Li Shi (1996) Qinling orogeny and metallogenesis.
Beijing: Metallurgical Industry Press, 12-31(in Chinese with English abstract)
Zhang BR, Luo TC, Gao S (1994) Geochemical study on lithosphere
struture and metallogenic regularity of Qinba region. Wuhan:
China University of geosciences Press, 257-311 (in Chinese with
English abstract)
Zhang GW, Meng QR, Yu Z (1996) Orogenisis and dynamics of the
Qinling Orogen. Science in China(Series D) 39(3): 225-234
Zhang GW, Zhang BR, Yuan XC (2001) Qinling orogenic belt and
continental dynamics. Beijing: Science Press, 702-705(in Chinese
with English abstract)
Close
Chapter 15-13
15-13
Zhengguang: A potentially large, high-grade
epithermal gold deposit in the Duobaoshan
metallogenic belt, Heilongjiang, northeastern China
Zhang Baolin, Wang Jie, Liang Guanghe, Xiao Qibin, Cai Xinping, Song Baochang
Key Laboratory of Mineral Resources Institute of Geology and Geophysics, Chinese Academy of Sciences, Qijiahuozi, Beijing
100029, China
Zheng Qingdao
Heilongjiang Bureau of Geology and Moneral Resources, Zhongshan Road, Harbin 151000, China
Abstract. Traditional ideas and methods are of limited use in deep
prospecting in plant and volcanic-covered areas in Heilongjiang
Province. The application of the authors’ ‘three-field anomaly interrestrain’ theory and a new geological-geophysical-geochemical prospecting technique combination has helped the local geological team
to learn more about ore-controlling structural and metallogenic information under the cover. Subsequent drilling programs have revealed and assessed a potential large high-grade epithermal gold
deposit in the southeastern part of the important porphyry copper belt.
Keywords. Zhengguang, epithermal, Duobaoshan, Heilongjiang
The Duobaoshan copper deposit in Heilongjiang Province was found and exploited in the 1970s. From then on,
the area has been considered as an important Paleozoic
porphyry copper zone. Although there is a very large reserve of 2.4 million tons of copper in the deposit, the very
low grade (aregage 0.45%) of copper ores has limited its
development. In recent years, a potential large high-grade
epithermal gold deposit was discovered and quickly assessed in its southeastern part, which may supply us with
some new understanding of the particular region.
From 2000, through geochemical survey of stream
sediments, the Zhengguang gold prospect was discovered by Qiqihaer minerals exploration team of the
Heilongjiang BGMR. After trenching work, altered diorite and andesite were found in the area. Via a series of
surface geological and geochemical exploration, geologists have delineated some discrete ore bodies with relatively high-grade of over 100g/t. However, due to the thick
cover of plants and soils in the region, they could not
learn more deep information by traditional prospecting
methods. Therefore, the relationship between ore bodies and ore-controlling structures could not be inferred
correctly.
In the autumn of 2002, the authors commenced deep
predictive work by means of a combined prospecting technique which consists of metallogenic fluid structural
analysis, reflection wave seismic exploration, MT survey
(equipped with high frequency sensor), deep penetrating geochemical survey and ground gama survey. Through
combined field observation, survey and data processing,
the complicated folding system, potential breccia pipe and
magmatic intrusions have been identified from the profiles. We have inferred that Zhengguang should be a Mesozoic crypto-explosive breccia-type gold deposit. With
the help of a new positioning predictive theory termed
‘three field (geological- geophysical-geochemical) interrestrain’, favorable metallogenic structural positions (targets or potential mineralization zone) were predicted
under the cover (Zhang et al. 2002).
In 2003, local geological teams finished two 500 meterdepth test drill holes which intersected seven ore zones
in depths of between 20 and 400 meter. The high-grade
ores develop the strong veinlet-type alteration of silicification-pyritization-epidotization. The highest grade is
in excess of 30g/t of gold. In addition, the drill holes intersected very thick alteration zones under the cover
which extended over 500m in the depth. From the preliminary result, the authors have inferred that there
should be a potential large gold deposit under the cover
(Zhang, 2004a, b).
In 2004, the Black Dragon Joint Venture which was established by the Heilongjiang BGMR and Leyshon Resources Limited of Australia carried out a 4500 meter diamond drill program in the target zone. The 30 drill holes
with the average depth of 150 meters and horizontal spacing 50 meters were arranged within the strong alteration
area. Finally, thick (up to 44 meters) ore bodies of high
grade (up to 580g/t) were intersected in the depth. Among
them, Hole ZGD029 recorded 24 meters @ 28.6g/t Au,
includeing 6 meters @ 93.0 g/t Au at about 90 meters below the surface. The estimated gold reserve of the explored
area is more than 20 tons (Leyshon Resources Limited,
2004a, b, c, 2005).
The discovery of the Zhengguang gold deposit has further confirmed the existence of a major epithermal gold
mineralization belt in the Mesozoic volcanic areas along
the Heilongjiang River bordering Far East Russia. Therefore, a significant number of prospecting targets is likely
to be delineated in the near future (Zhang et al. 2004).
Close
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Zhang Baolin · Wang Jie · Liang Guanghe · Xiao Qibin · Cai Xinping · Song Baochang · Zheng Qingdao
References
Leyshon Resources Limited (2004a). Significant first drill results from
Zheng Guang gold project, northeast China. In: http://www.asx. com.au
(July.15)
Leyshon Resources Limited (2004b). First Quarter Activities&
Cashflow Report. In: http://www.asx. com.au (Oct.29)
Leyshon Resources Limited (2004c). New High Grade Drill Results-Zheng
Guang Gold Project China. In: http://www.asx.com.au (Nov.15)
Leyshon Resources Limited (2004d). MD Presentation to the China
Mining Conference. In: http://www.asx. com.au (Nov.16)
Leyshon Resources Limited (2005). Second Quarter Activities &
Cashflow Report. In: http://www.asx. com.au (Jan.28)
Zhang Baolin (2004a) Application and result of the new predictive
theory of “three-field anomaly inter-restrain” and related techniques in rapidly selecting exploration targets in blind areas. Journal of Gold Science and Technology, 12(5): 48 (in Chinese)
Zhang Baolin (2004b) Zhengguang—a newly discovered highgrade epithermal gold deposit in the northern part of
Heilongjiang. Journal of Gold Science and Technology, 12(6):
46, 14 (in Chinese)
Zhang Baolin, Cai Xinping, Liang Guanghe, Xiao Qibin, Wang
Jie, Xu Xingwang, Song Baochang, Qi Min (2004c) The
positioning predictive theory, and techniques of the “threefield (geological- geophysical-geochemical) anomalies interrestrain” and their application in blind areas. Bulletin of
Mineralogy, Petrology and Geochemistry, 23 (supp): 151 (in Chinese)
Zhang Baolin, Wang Jie, Cai Xinping, Liang Guanghe, Xiao Qibin,
Song Baochang, Qi Min, Zhang Chengyu, Wang Baoiquan, Lu
Bingyan (2002) Summary of predictive work in 2002 and design of testing drill holes (Report of Scientific Project “Deep
prospecting prediction of Zhengguang lode gold target in
Nenjiang county, Heilongjiang”) (in Chinese)
Close
Chapter 15-14
15-14
An under-recognized mineralization style along
the northern margin of the North China craton:
Potential for discovery of large-tonnage
disseminated and stockwork-style gold deposits
T. Zhou, G. Dong
Sino-QZ Group Pty Limited, PO Box 2424, Mt Waverley, VIC 3149, Australia, and HT Mining (Beijing) Limited, 22C-2, 2 Xinxi
Rd, Shangdi Zone, Haidian District, Beijing 100085, China
Abstract. Based on recent field investigations of a number of the important gold deposits along the northern margin of the North China
craton, it is argued that broad zones of disseminated and stockwork–
style mineralization in some of the deposits have far greater importance than previously recognized. On a regional scale, the intersection
of the major NNE/NE- and E-W-trending structures, products of Mesozoic Pacific margin oblique subduction and Paleozoic-early Mesozoic craton collision, respectively, is a key to localization of the ores.
Keywords. Disseminated and stockwork–style ores, large-tonnage,
gold deposits, North China craton
1
Introduction
The northern margin of the North China craton has been
attracting much attention from both academic researchers
and mining industry personnel in the past decade, as it has
undergone perhaps the most lengthy, complex tectonic history in China, as well as hosting a resource of approximately
800-900t Au (Zhou 1999; Zhou and Lu 2000; Hart et al. 2002;
Zhou et al. 2002). In the past, much of the exploration work
in the region has focused on finding gold vein style mineralization; this style of deposit has been well described in
various recent research papers (e.g. Miller et al. 1998; Ao et
al. 2002; Hart et al. 2002; Zhou et al. 2002; Jin 2003). In the
past couple of years, we visited many of the important gold
deposits in this region, and have gained extensive and updated geological data through our exploration and mining
projects along the craton margin. Our observations indicate a much greater importance for broad zones of disseminated and stockwork–style mineralization in some of the
deposits than was previously recognized. We will attempt
here to share our experience in developing these newly identified targets with other explorationists, particularly those
from western countries who have been actively involved in,
or intend to step into, gold exploration and mining in China.
2
Broad zones of disseminated and stockworkstyle mineralization
The northern margin of the North China craton underwent several orogenic events as the result of the collision
of the North China craton with the Siberia and South
China cratons, and subduction of the Izanagi/Pacific oceanic plates. The E-W structures that dominate the area
were caused by the convergence between the North China
and Siberia cratons from late Paleozoic through Early Jurassic time, with the closure of the Solonkar Ocean occurring between the two blocks. In the eastern part of
this area, the E-W structures were overprinted by NNENE structures that developed as a result of the NW-directed, oblique subduction of the Izanagi/Pacific plates
under the eastern margin of China.
In the western part of the northern craton margin, such
as in the Wulashan goldfield (i.e., Hadamengou and
Wulanbulang gold deposits, approx. 20 km west of Baotou
City, Inner Mongolia), the majority of gold deposits belong to the well-described, gold-bearing quartz veins,
which are mostly about 1-1.5 m in width. In some favorable structural intersections and possibly favorable rock
types, however, relatively high-grade and wider veins may
be found.
From the city of Zhangjiakou (Hebei province) eastwards, an area containing the Dongping and Xiaoyingpan
(also called Zhangjiakou) gold deposits, the influence of
the NNE-NE structure is significant. Importantly, broad
zones of disseminated and stockwork-style mineralization have been recently identified throughout this region.
For example, a 70- to 130-m-wide zone of disseminated
and stockwork style ore was found to average 5-6 g/t Au
near the contact of a middle Paleozoic alkalic intrusive
complex and Late Archean gneiss/amphibolite at
Dongping. Similar looking disseminated and stockworkstyle ore zones have also been observed at properties
throughout Kuancheng, Qinglong and Pingquan counties,
which include parts of eastern Hebei province and adjacent Liaoning province, where the two major E-W and
NNE-trending structural corridors intersect. At the
Huajian-Niuxinshan deposit (about 200 km northeast of
Beijing), underground development intersected an over
35-m-wide disseminated and stockwork style ore zone
averaging 4.5 g/t Au, hosted in a silica-sericite-pyrite altered syenite dyke. Additionally, disseminated ores in
Close
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T. Zhou · G. Dong
sericite-pyrite altered Mesozoic granite, with grades as
high as 7.5 g/t Au, are mined by local workers from several adits driven into the Niuxinshan granite. The extent
of the gold mineralization in the granite is still unknown.
Only about 20 km north of the Huajian-Niuxinshan deposit, gold mineralization at the Yuerya deposit occurs as
both quartz veins and disseminated/stockwork style ores
within the Mesozoic Yuerya Granite. Most mineralization
occurs near the contact of the granite and Middle Proterozoic carbonate rocks. The disseminated/stockwork ores
have accounted for almost 25% of the production to date.
Recent underground exploration identified a 30-m-thick
disseminated/stockwork ore zone averaging 4 g/t Au. Further to the north, the Dongliang deposit and its extension within Pingquan county (Liaoning province) are characterized by similar high-grade zones of stockwork and
disseminated style gold ores over widths of 10-20 m. Further east, at the Baizhangzi deposit, a broad zone of disseminated/stockwork ores, 20- to 50-m-wide and with a
grade >5-6 g/t Au, has been identified along the margin
of a Mesozoic granite that intrudes Middle Proterozoic
metasedimentary rocks.
Although local controlling factors for these broad zones
of disseminated and stockwork style ore require further
investigation, a regional control appears to be the intersection of major NNE- to NE-trending structures with
the older E-W structures. In these areas of intersection
of structural domains, the competent margins of Paleozoic-Mesozoic igneous bodies are particularly favorable
hosts for development of gold-rich stockworks and disseminations. These areas within the northern margin of
the North China craton are the key targets for western
companies who are seeking large-tonnage gold deposits
in China.
ferent government organization. Once mining commenced, workers usually tried to extract the already recognized and easily accessible ores as thoroughly as possible, and neglected the importance of further exploration, particularly drilling to depth to enlarge the resource.
In fact, the majority of the mines in the region had never
been subjected to any underground drilling since the
mining operations started. As a result, after a few years of
mining activities, a mine was quite often defined as “the
mine in crisis” due to apparent depletion of the remaining resource. However, many mines have been revived after
new underground exploration and subsequent identification of additional resources. For example, the Dongping
deposit was given the status of “mine in crisis” before
May, 1999. However, further underground development
guided by experienced mine geologists has identified significant new gold resources at depth. As a result, the
Dongping deposit today remains as one of largest active
gold mines in China. Similar experiences have characterized development of many existing mines including the
Yuerya, Baizhangzi, and Niuxinshan deposits.
It is also worth noting that the broad zones of disseminated and stockwork-style gold ores usually do not
appear in outcrop and often occur solely in the subsurface. Above these broad ore zones, mineralization may
occur as narrow, auriferous quartz veins, e.g., at Dongping,
Baizhangzi and Niuxinshan. Therefore, during due diligence review for acquisition of mining projects in China,
explorationists from the western countries may need to
realize when considering the remaining resource numbers that these may be somewhat deflated, and they should
not under-estimate the potential for finding more resource
at depth in many of the already active gold mines across
northern China.
3
4
Issues relating to remaining resource/reserve in
existing gold mines
To correctly assess the remaining resource/reserve in existing gold mines, one must first fully understand the common practices in the Chinese exploration and mining industry. Traditionally, geological brigades under various
ministries of the State Council were assigned to conduct
regional geological and geochemical reconnaissance surveys, followed by preliminary and detailed exploration
projects that included trenching, limited underground
development, and some drilling. Generally, the footage
of each drill hole was in the range of 100 to 200 m, with
only a few extending to depths of 300 m or more, and the
majority of the drill holes were sub-vertical. By the end
of a detailed exploration project, each brigade would submit a geological report with indicated and inferred resource (in Chinese categories C and D, but occasionally
B), and all data would be transferred to the mining sector
representatives, who were usually administered by dif-
Concluding remarks
The northern margin of the North China craton is one of
the major gold provinces in China. However, most exploration and mining companies from the western countries
appear to be perplexed when it comes to exploration in
this area, as the deposits there were traditionally described
as narrow gold –bearing quartz veins, normally only 1to 2-m-wide, and, therefore, would not be suitable for largescale mining. Our recent work suggests that significant
potential exists for the discovery of broad zones of disseminated and stockwork-style gold mineralization in the
subsurface beneath known vein systems. On a regional
scale, the intersection of the major NNE/NE- and E-Wtrending structures, products of Mesozoic Pacific margin oblique subduction and Paleozoic-early Mesozoic craton collision, respectively, is a key to localization of the
ores. This particularly characterizes the North China craton margin to the east of Zhangjiakou. Because these broad
zones of disseminated and stockwork style gold ores typi-
Close
Chapter 15-14 · An under-recognized mineralization style along the northern margin of the North China craton
cally occur at depth, and giving the common practices in
the Chinese exploration and mining industry, one should
not under-estimate the significant potential in finding
multiple Moz gold resources during evaluation of exploration properties and existing gold mines.
Acknowledgements
We wish to thank many mine geologists and management
staff for sharing their experience and knowledge in Chinese exploration and mining industry, particularly those
from CNGC and its gold mines; Dongping Mine; CITIC
Gold; and government administration of Kuancheng
County, Qinglong County and Chongli County. We also
appreciate the time and support provided to us by the
staff from Eldorado Gold, Hunter Dickinson, Noranda,
Ivanhoe, Gold Fields, Planet Explorations, Fury Explorations, and Anglo American during our joint field investigations. Richard Goldfarb of US Geological Survey is
thanked for review and editing of the manuscript. We also
would like to extend our appreciations for assistance and
support from staff of the Jinyou Exploration, Sino-QZ
Group and HT Mining, particularly Zhigang Yang,
1563
Renzhao Zhou, Guowei Lei, Guanglan Wang, Pencheng
Zhang, Huijuan Wen and Junqi Yin.
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