Geology
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KOMUNITAS BLOGGER UNIVERSITAS SRIWIJAYA
GEOLOGICAL AND METALLOGENIC RECONNAISSANCE OF SOUTH OF MANBIJA
GEOMINES 1. INTRODUCTION 1.1. OBJECT OF THE PROJECT AND USED METHODS
The purpose of the project consists of elaborating a detailed geological map (1: 2000) of a
region of 632 hectares or rather 6.32 km² located immediately to the South of the
auriferous zone of Nambija, on current development. With this purpose, an equipment
composed by two geologists and a topographer, and complementing afterwards with a
geophysical, they have stayed during 10 weeks in the area of the project, from May 22 to
October 1st, 1987. The maps and the final report have been elaborated in the offices of
Geomines Ltee in Montreal, Quebec, Canada. In first term, it has been proceed to effect a
topographic raising to scale 1:2000 of the creeks and paths using compass and cord. Then,
the geological map simultaneously has been elaborated. they have been taken superficial
rock samples and sediments of the rivers using bats. These samples have been after
mashed and analyzed in laboratories by 36 elements. Of the same way, they have been
developed geophysical explorations by magnetometric and electromagnetic (VLF) on a mesh
NS - EW with exploration lines that have 16 km of length. Also, it has been effected a
geological recognition to scale 1:5000 with takes simultaneous samples of bat rock, in a
region of some 18 km2 located to the South and to the East of the maping region to the
detail. 1.2 LOCATION AND ACCESS Nambija is located in Southeast of the Ecuador, at 20
km to the East of Zamora, capital of the province of Zamora Chinchipe, and 420 km to the
South of Quito. The first section of the route to Nambija is from Quito to Loja. In this first
section can be traveled by plane from Quito to La Toma (airport of Loja) in a flight that take
approximately an hour or in car, in a trip that delay 18 hours, by asserted highway. From Loja
part a second category route to Zamora, whose normal tour delay two hours and a half, but
the frequent landslides that produce in this route can cause serious arrears. From Zamora
the route continues to Namírez, place to where is arrived after a trip of an hour. In
Namírez is necessary to cross the river Zamora, either in boat, if the level of the
water is not too high, or using a peatonal pendulous bridge. The trip continues then in car or
bus by an additional hour until Cumay Alto (locally called San Carlos), place where it can be
rented mules to rise to Nambija in a trip of three hours and a half, duration by a horse-shoe
road in wrong state. 1.3. TOPOGRAPHIC AND CLIMATE The region in study is located in
the mountain chain of Nanguipa that form part of the buttresses of the Eastern mountain
chain of the Andes. The relief is very injured, with altitudes that vary between 1400 and 2400
msnm. The area is characterized by the numerous defects presence and scars let by the
landslides. The drainage system of the region is certified by the tributaries of the Quebrada
del Fierro. The waters of this gaps empty successively in the rivers Nambija, Zamora,
Santiago, Marañon and Amazon and finally in the Atlantic Ocean. The climatological
information is extremely limited. The climate is tropical wet. The temperature oscillates
between 7°C in the evening and 20°C in the day, but exceptionally it can reach
30°C. The region is frequently covered of fog and the rainfall surpasses 3000 mm by
year, what has hindered much the advance of the field projects. In September has been
observed a certain truce in the rainfalls that possibly will be extended until December. The
vegetation is of the type florets pluvial equatorial and therefore very dense, to such point that
it is necessary to use machetes to open path. The rock outcrops better exposed are found in
the creeks, that constitute at the same time the improvements access process. 1.4.
LOGÍSTIC The communications are difficult in Nambija. The only one transmitting
radio station - receiving of the place is found in the branch of the Central Bank for internal
use. Within little time, the bank will be equipped also with a telephone operated at micro waves. Concerning the public facilities, the IETEL of Zamora offers international telegraphic
and telephonic services but it does not have telex. The most next Airport is La Toma, near to
Loja, that gives services in regulars flights to Guayaquil and to Quito. Exist also a runway
and a military heliport in Cumbaratza. In Nambija, there is a heliport located in the facilities of
the Central Bank. Also, it is possible to rent pickup trucks without difficulty, taxi to Loja and to
the airport La Toma, the same as to Zamora. Insofar as the provisions, the basic products
can be acquired in Nambija, but the variety is limited. The available water in Nambija has a
high risk of be contaminated, so that in the present campaign the personnel has been
provisioned of spring water, considerated pure, that buds in the South flank of Mapasingue.
In Nambija is difficult to find a housing adapted to stay by long time. Therefore, it should be
to consider the need of building a base camp. Because of the climate, the type of
construction more common is of wood, up with respect to the natural surface and with zinc
roof. The wood in plates can be acquired of the local rafters but the zinc must be bought in
other place. Taking into account to the temperature descends by the nights, it will be very
useful to have any type of heater (to kerosene for example). In the place is found kerosene,
oil diesel, gasoline and also gas balls. Electricity can be acquired of some proprietary of
stamp mills equipped with electrical generators. Also, in the area is possible to find hand of
work not qualified: guides - cutters, carrying, pawns, etc. The availability of this labor
fluctuates of agreement at the rate of the mining production. 1.5 HISTORY AND METHODS
OF EXPLORATION The development of the gold in the region date of the pre-Columbian
era. To mid of the XVI Century, the Spanish continued the development using the indigenous
labor, but around the end of this century the diseases and the social instability caused to the
close of the mining activity in the region. It is recently the beginning of the present decade
that the deposit of Nambija was rediscovered for the gold seekers that were soaring the
creeks washing the sediments by batting. At the beginning, the development were made
discreetly, but the secret could not be kept by far time and the region was quickly invaded by
thousands of persons contaminated by the fever of the gold. According to our estimates, to
the moment of elaborating this report, the population of Nambija is between 7 and 10
thousand inhabitants. Regrettably, the deposit is being exploited of inefficient and chaotic
way. Many small mining their dig where better galleries seem, without planning and without
taking into account the most elemental safety rules. To trigger the driller hammers are used
compressors activated by diesel motors. Once the drills are punctured, they are put dynamite
charges and is flown the rock. After is separated visually the sterile fraction from the
mineralized fraction that is transported immediately by the shoulder to one of the numerous
windmills of stamping where the rock is mashed in water presence. The product of the
grinding is gone through a wash channel in order to separating the heavy fraction.
Immediately, this last fraction is washed in mercury presence to obtain finally a ball from
amalgam from mercury - gold that then is burnt to the blowpipe to make to boil the mercury
and to obtain relatively pure gold. After, this product is transported to the local branch of the
Central Bank that buys the metal after have been molten and heavy. 1.6 GRATEFULNESS
The authors wish to thank to the Central Bank of the Ecuador by the price help that has
provided, in particular, to the Chief of the Marketing Department of the Gold in Quito, Lcdo.
Oswaldo Hernández, and to the managers of the branch of Nambija, Lcdo. Galo
Román, Lcdo. Fausto Andrade and Lcdo. Baltasar Guaruizo. Our permanency in
Nambija has been more agreeable thanks to your hospitality, his experience with respect to
the local conditions and your logistics assistance, without speaking of the banking services.
In Zamora, we want to thank to Mr. Magner Turner and his equipment by the borrowed
logistical services and by the visit to the mine of Guaysimi. Two teachers of the University of
Quebec in Montreal, Dr. Michel Gauthier and Dr. Michel Jebrak, they have encouraged us
much with theis stimulant discussions on the nature of the deposit. We thank also to Dr.
Robert Wares (Ph.D.), they specialized in skarns that it has contributed largely in the
elaboration of the chapter "Metallogenic" already to Mrs. Anne Charland (M.SC.)
that has participated with their knowledge of volcanic rocks, both of the University McGill in
Montreal. In the University of Laval in Quebec, we want to thank to Dr. Réjean
Hébert (Ph.D.) and to Mrs. Sylvie Roy (M.SC.) by their petrographic descriptions, as
well as to Dr. Robert Ledoux (Ph.D.) by their appreciated concerning advice to the heavy
minerals. We thank, also, to all the equipment of the INEMIN of the Ecuador, whose
countless services would certify a vast list. Furthermore, we thank also to the Ing. Edgar
Pillajo, who has elaborated the cartography of the vertex NE of the map B. We are
particularly recognized by the services of the Eng. Ivan Endara, Director of the Laboratory of
Chillogallo, and Dr. Ahmed Mahmood, belonging to the regional office of Geomines in
Rouyn-Noranda (Quebec), by the execution of the petrographic studies. We thank to the field
brigade certified by Mr. Marc Chénier - geologist project chief, Mrs. Sylvie
Prud\'homme - geologist, Mr. Albert Bastien - technical - topographer - drawing, Mr. Jan
Stembera - geophysical, and Mr. Arturo Cabrera - assistant of field and logistical support in
Ecuador. At the end, thank you very much to all the auxiliary personnel so much in Ecuador
as the Central headquarters of Géomines in Montréal, Canada. 2. GENERAL
GEOLOGY Exist two recent geological maps, to scale 1:1.000.000. that they cover the
Republic of Ecuador. One of them has been published by the DGGM and the French Institute
of Oil, in 1969, and the gold by the DGGM and the Geological Sciences Institute, in 1982.
The present chapter is widely based on this last and in the explanatory bulletin that
accompanies it. Ecuador is split into three geological provinces that correspond
approximately at three regions phisiographycs. These three regions are, from West to East:
The Coast, the Sierra split into two mountain chains separated by the Interandino Valley in
the North of the country and the East separated in two regions: the subandina zone and the
Eastern Basin (Figure 3) The basement of the coast is constituted by basaltics toleitics rocks
of the Cretacic, that would constitute a portion of the Oceanic bark welded to the continent.
These rocks are recovered of detritics sediments of the Cretacic Sup. and of the Terciary.
The Western mountain chain is composed by basaltic volcanic rocks of the Cretacic
(equivalent to those of the Coast), recovers of andesitics and of piroclastics lavas of the
Terciary and of the Quaternary. The Real mountain chain (or Eastern), on the contrary it is
formed by a whole slew of metamorphics rocks (esquists to mica) of the Paleozoic. The rut
intra -Andean, that separates the two mountain chains in north half of the country, it is a
depression whose exact nature is not known due to the fact that the contacts are covered by
the volcanics recent. A great fault of cabalgamiento separates the Sierra from the East,
where is found in first term the subandina zone structurally separate, but stratigraphicmently
forming part of the properly such Eastern Basin located more to the East. This basin is
composed of sedimentary rocks deposited in three phases on the precambrics rocks of the
Shield Guyano-Brasilian. First, the marine sedimentary of the Paleozoic and of the low
Mesozoic (Formations Pumbuiza, Macuma, Santiago and Chapiza), phase ended by the
volcanism (member Misahuallí of the Formation Chapiza). Then, the marine
sediments deposition geosinclinales of the Cretacic Superior (Fm. Hollín, Napo and
Tena regrouped also under the training name Lemon). The end of the Cretacic brand the
origin of the Andean orogenismo that is characterized by a classic sedimentation originating
from the West. The subandian zone has been distorted in the Terciary Superior. The fault
that defines the West limit of the subandian zone and their contact with the Real mountain
chain is labeled by the presence of a series of batholith granitic of the Jurassic (?), probably
displaced by the tectonic associated with raising of the proto -mountain chain (end of the
Cretic). The volcanic rocks and subvolcanics associated with certain batholiths, as the
batolite of Abitagua and included in the miembre Misahuallí of the Chapiza
Formation, they could represent a late phase of that same plutonic (evidence of
comagmátic origin). By extension, this theory would be related perhaps also to home
volcanic rocks observed within the limits of the Batholith of Zamora, in the area object of the
present study. In addition to rocks plutonics granitics, they have been mapping, very about
this region, sedimentary rocks of the Santiago and Chapiza Formations to the North and to
the South and possibly to the East (Feininger, 1987), the same as sediments more youths of
the Lemon Formation (to the North). Feininger (1987) proposes a theory according to the one
which Ecuador would be split into five "lands" allotóctonosos, between
those which is found the "Santiago Terrane" that understands the South half so
much of the Real mountain chain as the of subandian zone (including the Batholith of
Zamora), zone characterized by the exclusive presence of the Santiago Formation that would
be absent in the other areas. Santamaría et all. (1983) and Pillajo (1983) have
effected projects in the region of Nambija (photogeologyc maps and general recognition
visits). Both identify a sedimentary and volcanic rocks zone to the inferior of the batholith,
zone that would have been in part skarnificated. The auriferous deposit of Nambija is found
within this zone. 3. GENERAL GEOLOGY 3.1 LITOLOGIC DESCRIPTIONS 3.1.1
GENERALITIES In the framework of the present work have been carried out two geological
raisings. The first, to scale 1:2000, it has covered a zone of 6 km2 located immediately to the
South of the deposit of Nambija on current development. To the East and to the South of this
detailed zone, was effected a mapping of recognition level, to scale 1:5000, that covers a
total surface of 18 km2 . During the development of these raisings were described about 700
outcropss and the litological and structural information obtained were registered on the
respective topographic maps. In order to determine the nature of the litological units found,
very affected locally by hydrothermal alteration, and to specify the nature of the auriferous
mineralization, they have been studied 180 sample thin plates and 56 thin polish plates with
the intervention of five specialists in petrography. All the samples originate of the zone of 18
km2, 29 that they were taken within sector of the mine of Guaysimi. The conclusions of these
petrographic studies form part of the description of the different litological units and of the
chapter "Metallogenic". The region of Nambija is little known geolgically, the few
existing maps are very general and they have been elaborated for the most part by
photogeological interpretation. This region located to the South of the Ecuador, in the
subandian zone, it is a characterized by the sediments presence and volcanic of age
Paleozoic to Mesozoic cut by batholiths of composition between tonalitic and
granodiorític of Jurassic age (?). The zone is tectonicly active and constitutes a
strongly ridden waist that is displaced currently to the East. The estratigraphy of this zone is
relatively well known in the North and in the central part of the country, largely thanks to the
oil exploration projects. On the contrary, in the South of the country, to the East of Zamora,
the place is not very documented and, according to certain recent projects (Feininger , 1987),
would seem that the estratigraphy and the tectonic evolution in this place would have been
different with relation to the North parth. Consequently, even though the rocks observed in
these raisings seem to belong to the training Santiago (Jurassic - Superior), lack geological
data to regional and local scale in the region of Nambija, so that the restricted surface of the
studied zone does not permit to establish estratigraphic correlations in the present study.
Furthermore, the relationships between the different litological units found not always they
can be clearly established in reason to the numerous defects that cut all the considerated
zone. During the mapping, we have attempted of regrouping the studied rocks by phases
recognizable on the area, that is to say, in lithologics maps. In general way, is found a
sequence volcanic - sedimentary that houses to the auriferous mineralizations, forming a
band of some kilometers of broad in the bosom of a batholith of granodiorític
composition . This band volcanic - sedimentary seems be extended by several kilometes
according to direction N-S and it is limited from East to the West by probably normal defects.
The sequence is constituted by proplastici rocks ( volcanic gap, block tuffs and lapillis, crystal
tuffs) between those which are intercalated thin horizons of calcareous (sands and
calcareous shales) metasomatcs in skarns and associated with the auriferous
mineralizations. All these materials are cut by dikes and by small stocks of diorite, of apilitc
and of subvolcanic rocks of composition as same as the strusive rocks also volcanitcs (basalt
alkaline) and late dolerites in the defects and shear zones. 3.1.2 INTRUSIVE ROCKS 3.1.2.1
Granodioritic (G and G1) This litological units, probably located in the lower part of the
stratigráfic sequence of the studied zone, is found in the edges East and West of the
mapping surface, constituting in fact a batholith that is extended throughout several
kilómeters within the region. In the considerate place, this unit is cut by numerous
defects that they have given cause for a collapse structure within the one which has been
deposited thereinafter a sequence volcanic – sedimentary. The unit that is all right
characterized in the outcrops and it can or not to present alterations. The rock is of pink
color, gray and white with small black stains caused by the crystals of hornblende. The
texture is generally mean and equigranular. In the eastern part of the mapping zone, in the
region of the river Guaysimi, is observed a facies of phenocrysts of hornblende with middle
size that varies between 5 mm and 1cm. Locally, the granodioritc can contain intrusive fine
material enclaves of obscure gray color and of variable diameter between 2 and 10cm. It is
equally certain note composition zones more potassic than confer to the rock a most reddish
color. At petrographic level, the granodiorite is mainly composed by waved extinction quartz,
of plagioclase (oligoclasas-andesina) and of pheldespatos potassics kaolinizeds and
sericitizeds, of hornblende and of small quantities of biotite with alteration in chlorite and of
traces of disseminated opaque minerals (mainly pyrite). It is observed equally trace of apatite
and of zircón as incorporation in the plagioclase, as well as esfene. The epidote,
under the form of prismatic crystals, is found in the form of incorporation in the plagioclases
pheldspars, replacing to the hornblende and in the form of veins. Finally, they are found
secondary carbonatics altering the plagioclases and the hornblende. 3.1.2.2 Tonalite-diorite
(T) The second intrusive important unit of the region seems to cut the granodioritic. its
composition, though locally tonalite, it is mainly diorite. It is frequently found in the
granodiorite in the edges of the e mapping zone in touch of defect with the volcanitcs
according to the direction NS. It is note also the presence of some dikes as well as of a small
stock in intrusion within the volcancs in the central part of the region (Bankrupt #15). In this
place, the diorite is cut by numerous defects and the intrusion contacts with the volcanic that
surrounds it seem labeled by defects. The rock is of fine texture, (1 mm), equigranular, of
clear gray color to gray middle, locally cut by pink veins of potassic alteration. In the eastern
part of the region, are observed locally outcrops of granitic thoroughly pink inside of this unit.
The rock is composed mainly of pheldespar potassics and of plagioclase kaolinized,
sericitized and epidotized, of waved extinction quartz, and of hornblende and altered biotite
in chlorite. It is note also intersiticial secondary calcite in the plagioclase and the hornblenda,
as well as in the form of veins. They are equally present the opaque minerals. In a sample
(#1101), is observed a "stockwork" of veins of pyrite, pirrotine and calcopyrite,
with impregnations of magnetite associated with the alterations in epidote-chlorite. The dikes
observed in the region can be microdiorítics, of whitish color, sericitized, with the
mafics minerals thoroughly altered. In the center of the region, in the Bankrupt #11, are noted
dikes with epidote, clinozoisite and tremolite-ferro -actinote. A little more to the East, in the
Bankrupt #14, to the height of the Wells Eight, can observe an intrusive of whitish color and
of fine texture, probably semi - deep and located throughout a defect E-W, the one which are
associated some occurrences of skarn. The rock presents an n biotític precocious
alteration, a very strong hydrothermal sericítice alteration with piritizatión and
finally a potassic alteration. 3.1.2.3 Subvolcanics Intrusives (A1 and A2) Between the
intrusives that they seem late and that they cut the granodiorite and the diorite, it is note a
hipoabisal facies of andesitic composition that is presented under the form of small intrusions
in the Southwest part as well as in the center of the region, associated with the skarns of the
mineralized zones on current development of Nambija. It has been noted their its presence in
the sector of Mapasingue, where seems intercalated with the horizons of ashes tuff, as well
as in the zone of the Playón. To fresh surface, the rock is of porphiritic texture with
phenocrysts of plagioclase whitish of 1 to 2 mm, in the bosom of a gray color greenish
counterfoil, frequently pyritized. When the rock is altered, is presented of whitish color and of
rather mean texture. Microscópicmently, they are observed phenocrysts of
plagioclase, strongly sericitized, in a quartz counterfoil – feldspar microgranular. The
mafics amphiboles minerals are entirely decomposed in clorite, ferro-actinote, calcite and
epidote. It is note equally secondary quartz and calcite in microfisures. In the contour of the
stock dioritic, in the part east-central of the region, the results of the geophysical raising
indicate the probable presence of a dike of granitic of direction NW - N. The outcrops in the
surroundings indicate the rocks presence of type lode, hollocristaline and porphyritics. The
rock shows a beige counterfoil color to clear brown with phenocrysts of whitish plagioclase
from 2 to 4 mm. Microscopicmently, in addition to the plagioclase, is note the green
hornblende, a little of quartz in a quartz counterfoil - feldspar with esfeno, tourmaline and
opaque accessory. The composition is tonaític. 3.1.2.4 Reddish composition dikes
tonalitic-dioritic (D1) To the Northwest of the mapping zone, in particular in the bosom of the
diorite, are observed dikes of some meters of thickness, of direction E-W, NE-SW and of
abrupt slope, constituted of a brown material - reddish to reddish, of slightly texture
porphyritic, compound of plagioclase (and of Kfeldspar) altered by the calcite and epidote, of
quartz, and of a fierro -magnésic (amphibol) clorotized. It is note also the apatite, in
incorporation within the plagioclase, and the epidote. Locally, the dikes present edges of
about 1 m of broad composed of a fine material, laminated, of beige color. In thin plates, the
rock is leucócrata, constituted of felsics minerals thoroughly sercitized. The global
composition of the dikes seems be from tonalitic to granodiorític. Finally, these dikes
seem be displaced by the defects N and NE. 3.1.2.5 Dikes of dolerite (D2) Some dikes of
dolerite cut the volcanics in the central part, to the South of the region. These dikes, of
direction NW, seem associated with the important defect of the same direction and slightly
decalados by the direction defects N-S and NE-SW. These dikes, with a broad maximum of
about 2 meters, present a fresh surface of obscure green color, of fine texture to mean or
slightly porphyritic. They are composed of plagioclase moderately basic, kaolinized, of
pyroxene (augite) fractured with a chlorític alteration and a little of disseminated
opaque minerals. Locally, they have been able to observe tapes in the bosom of the dikes
with an edge aphanític obscure and obscure color levels and of fine texture to mean,
altering with levels clearer. It should be to note that the dikes, subsequent to the volcanic,
they are not affected all over the net of fractures that cut to these last. 3.1.2.6 Dikes aplitics
and intrusive felsics several (D3) Flat several of defects N-S and E-W they are associated
with the presence of aplitcs or of intrusives felsics, generally of clear gray color and of bulk
texture. These rocks are composed mainly of plagioclase (oligoclasa-andesina) and
Kfeldspar, kaolinized, sericitized and with alterations in epidote and carbonates. 3.1.2.7
Dikes of andesite porphyritic (D4) In the north - center of the region, in the Bankrupts #11
and #14, are noted "dikes" or washes of andesite porphyritic of about 1 m of
broad cutting the pyroclastics rocks. In the outcrops, the rock is of gray color - greenish clear
with phenocrysts from 2 to 5 mm of diameter and obscure color. In thin plates, is observed a
counterfoil formed by microlits of plagioclase, phenocrysts sub - automorfs of an ancient
ferromagnesiane (piroxene or hornblende) entirely replaced for the counterfoil. Finally, it is
note the presence of pyrite and of calcopyrite, in irregular bulks of about 5 mm of diameter
disseminated in the rock. 3.1.3 VOLCANIC ROCKS 3.1.3.1 Generalities The lion\'s share of
the mapping territory for this study is composed of volcanic rocks, that certify a sequence
volcanic - sedimentary. Such as has been mentioned previously, these rocks form a band of
some kilometers of broad, of direction N-S, and it is in touch of defect with the granodiorite.
Seem, to the light of the field observations, that the volcanic rocks would be subsequent to a
batholith granodioritic. However, the volcanic rocks are cut by dikes and by small instrusions
of composition tonalite-diorite, as well as by dikes of dolerite, intrusives felsics and, less
frequently, by rocks hipoabisals, lava washes andesitics and injected basaltics in the shear
zones. The sequence is formed mainly of piroclastics rocks in those which the composition
seems quite uniform, of andesitic to dacitic locally. In general way, they are observed tuffs of
lapilli, , they are constituted by crystals of plagioclase and by fragments of traquiandesite in
the bosom of a volcanic counterfoil. With much frequency, is note the minerals presence
metamorphics such as the epidote, zoisite, tremolite-ferro - actinote, chlorite, vesubianite,
calcite, probably due to a metamorphism of contact. The final facies constitute the cornea
rocks. Such as has been mentioned in the introduction of this chapter, the different mapping
facies represent descriptive facies (litological map units) before that litoestratigráphic
units in the strict sense. The distinction between the various parts, even though it is
substantially granulometric, it is given also by the color and the texture of the rock, as well as
by the percentage and the composition of its constituent. Locally, the rocks present own
characteristics in several facies and not always it has been able be established a very clear
distinction. 3.1.3.2 Volcanic Breccia (V1) The facies most characteristic facies consists of a
volcanic breccia located in the Northeast part of the mapping area, that is to say, in the
Bankrupt of the Diamond and to the East of the mountain chain of Nanguipa. In the outcrops,
this litology unit is presented either masive or intercalated with block tuffs, lapillis and ashes,
forming visible tapes to the natural scale. The composition of these tuffs seems the same
that of the breccia, with the only difference of the smaller size and the abundance of the
fragments in the rock. The breccia facies presents a whitish alteration surface to beige clear
with dusky color fragments. In fresh surface, the counterfoil is generally mean greenish to
obscure. The rock is composed mainly of a counterfoil criptocristaline quartz - feldspar, of
phenocrystals of plagioclase of about 2 mm and of litics subangulares fragments of middle
size, about 1 to 4 cm, being able to reach a ten centimeter. These fragments are of volcanic
origin, originate of trachite compounds rocks of microlits of plagioclase with volcanic glass
and present a fluidal texture. The global composition of the volcanic breccia is andesitic.
3.1.3.3 Tuff of Lapillis (V2) This facies occupies most share of the mapping surface and it
can present various aspects. However, in general terms this unit is composed of phenocrysts
and of litics volcanic subangular fragments of variable size between 1 mm and 3 cm (with an
average about 1 to 2 mm) in the bosom of a fine counterfoil. The alteration surface is of gray
color - greenish middle beige clear, spotty of black points that present an aspects that
denotes the differential erosion of the fragments. In the eastern part of the Bankrupt of the
Diamond, this fragment tuff litics and of phenocrysts is the equivalent of the volcanic breccia
of bulk grain described previously. It is note equally in the same sector, and frequently
intercalated with these facies, a rock a little different with a clear gray fresh surface showing
fragments, of phenocrysts pale and obscure. In thin plates, the composition is revealed
similar to that of the breccia. They are observed phenocrysts of plagioclase (0.2-1 mm),
occasionally sericitized and epidotized with rock fragments andesitic of traquític
texture. The counterfoil composed of quartz, of feldspars and locally of micas, it is finely
crystalline. It can be also to note alterations in chlorite, epidote and serecite, as well as
secondary quartz and coals in veins. The global composition of the rock is andesític
and dacitic locally. 3.1.3.4.- Crystals tuff (V3) Even though understand occasionally litics
fragments and are related also with the tuffs of lapillis described before, the rocks grouped
under the present facies contains a percentage relatively topmost of phenocrysts. To fresh
surface, this litologic unit presents whitish phenocrysts of plagioclase of about 1 to 2 mm in
the bosom of an obscure gray counterfoil to black. When the rock is altered can present a
greenish or clear gray dye. Microscopicamently, they are observed crystals of plagioclase
(oligoclase-andesine) that they can be sericitizeds or epidotizeds with the hornblende
chloritizade locally in a counterfoil criptocristaline quartz - felddpar. It is note frequently an
alteration in epidote, chlorite, calcite and a secondary silicification in all the rock whose
composition can vary of generally andesític to riodacític locally. In the zone
located in the immediacys of the stock of tonalite-diorite, in the center of the region, that is to
say, in the intersection of the Bankrupt of the Fierro and of the Bankrupt of the Green Snake
and in the road of Guaysimi, the rock shows a potassic pronounced alteration. They are
noted Kfeldspar and the presence of epidote and occasionally of garnet. 3.1.3.5 Black Tuff
(V4) This faices groups to the grain rocks highly finer in comparison with the others faices
described before and understands the ash tuffs as well as the tuffs lítics of crystals
riodacític composition to andesític. In the bosom of this unit are observed
frequently originated tapes for the alternation of ash caps, of lapillis and crystals, in particular
in the center of the region, being directed northward and the hill of Mapasingue (head-board
of the Bankrupts #5 and #11). The litologic characteristic of this facies is a tuff of obscure
gray color to black, of afanitic texture and of andesitic composition. In thin plates, are noted
crystals of plagioclase, quartz and biotite, recristalized with a size middle size of about 0.05
to .5 mm. Equally, they can be consisted the volcanic glass presence in process of
desvitrification, being transformed into chlorite. This black tuff can be observed, between
other, in the Bankrupt of the Fierro, between the South branch of this same bankrupt and the
Bankrupt of the Green Snake. In the Bankrupt #11, it can be stressed the outcrops of a rock
of obscure gray color, slightly reddish and of aphanitic texture. Locally, this rock shows
phenocrysts of plagioclase and litics traquiandesítics fragments whose size varies
from 1 to 4 mm, as well as greenish lodes of epidote. The criptocristaline quartz - feldspar
counterfoil is epidotized and the tremolite and the quartz replace locally the lítics
fragments. 3.1.3.6 Welded Tuff and Ashes Tuff (V5) This facies understands the piroclastics
rocks located on the hill of Mapasingue, in the part center - north part center of the mapping
region , and associated with the auriferous skarns. Include, equally, the identical piroclastics
that they have been observed in contact with the skarns of the development of Nambija that
they are designated "box" by the inhabitants of the place. The outcrops of this
rock show an alteration surface beige clear and an afanitic texture. This alteration penetrates
profoundly in the rock and alone very rarely it can be perceived a freshest surface of bluish
pale gray color. In thin plates, this facies reveals a litic tuff composition with fragments weld
of tranquiandesite and of hialine rock with vitreous cement and phenocrysts of plagioclase.
The grains counterfoil very fine is sericitizade. It is note, equally, an intensive silicification
expressed by numerous beaches, aggregates and quartz lodes, as well as of epidote, of
calcite and of vesubianite in the contact zones with the skarns. These afanitics levels can be
intercalated to the centimetric scale with horizons of whitish material of fine texture, the same
that they are particularly observed in the summits of Mapasingue toward the South flank. The
horizons are constituted of tuffs with phenocrysts of plagióclase thoroughly sericitized
and some traquític fragments rock, whose plagioclase are transformed into tremolite
esferulitic. It is note also a fort silicification of the rock. In the extremity East of the
Mapasingue hill is observed a similar rock, but in the one which the size of the crystals is
superior to those of the others piroclastic rocks. For that reason, this rock has been
represented under the facies of crystal tuffs on the geological map. This piroclastics is the
equivalent of a traquiandesite or microdiorite with a counterfoil holocristaline and some
composition fragments andesitic. The rock has suffered, on the other hand, a tectonic sharp,
such as reveals it the parallel fractures presence full of quartz, as well as a metamorphism of
contact with epidot and vesubianite. From the point of view petrographic, the rocks belong to
that facies can be approximated with those of the facies " black tuff" with tapes. it
would said that its current aspect, as well as its low magnetic susceptibilities, they would be
due to a strong hydrothermal alteration and to an intensive silicification, before that an
original composition more felsic. Some occurrences (Bankrupt #5 et #14) of welded tuff more
typical ("ash-flow tuff") have been included equally in this facies. This litic tuff of
crystals is constituted substantially of plagioclase sericitizade and epidotizade in a vitreous
counterfoil altered in zealots or hidrobiotite and presents flowing structures (laminations and
stretched glass thorns). 3.1.3.7 Alkaline Basalt (V6) In certain greater defect zones (Bankrupt
#5, Bankrupt of the Fierro South, Well Ramón), is note the late lavas presence. In the
outcrops, the rock is of obscure green color, of afanitic texture to porphyritic, with
phenocrysts of plagioclase that reach 1 mm of size, epidote and chlorite. In thin plates are
observed plagioclase sericitizade and epidotizade either with hornblende or with a piroxene
(titano-augita). The counterfoil is composed of microlits of plagioclase and of volcanic glass
replaced by clorite and serpentine. The epidote, the quartz and the carbonats are present in
veins and the chlorite under the form of alteration mafics minerals. The opaque minerals are
disseminated in the counterfoil or in the form of incorporation in the amphibolite. These rocks
have been classified as andesitcs or andesitc basaltic when they have been effected the
petrographic studies. The chemical analysis of total rock reveal, however, an alkaline affinity
for these rocks that they have been regrouped under the denomination of "alkaline
Basalt\'s" in attention to the geochemistry studies more detailed. 3.1.3.8 Volcanic
Indeterminate (V) This category has been used on the geological map in the places in which
they have not been possible to specify the type of volcanic rock, either in reason to the lack
of data or to the intensive hydrothermal alteration that they do not permit the identification of
the rock. 3.1.4 SEDIMENTARY ROCKS 3.1.4.1 Calcareous and Sandstones (k) The alone
important occurrence of calcareous in the region is located in the surroundings Well
Ramón, to the Northeast of the mapped region. In this place, is observed with
calcareous intercalated with some few sandstone banks as well as with litchis tubas of
lapillis. Certain banks of calcareous are metamorphosed in skarns. The calcareous observed
are constituted by calcarenitas, calcisititas and calcilutitas, slightly marmorized in contact
with the skarn. A fragment of braquiópodo not identifiable has been stressed locally.
The sandstone banks have between 0.5 and 2 m of broad and they are composed of
feldspar angular sericitized and kaolinized, rounded quartz grains as well as rock effusive
fragments constituted of submicroscopic crystals. The cement is carbonated. 3.1.5
METAMORPHICS ROCKS 3.1.5.1 Generalities The places where are found the cornea
rocks and the skarns represent zones of metamorphism of contact, accompanied of
metasomatism in the case of the training of the skarns. These rocks derive from the
transformation from a sequence volcanic - sedimentary in rocks the one which piroclastics
are intercalated with calcareous and calcareous sandstones. In the immediate surroundings
to the mapped region, the only important zones where they can be observed the skarns
constitute the same sites of mining development of Nambija and of Guaysimi. In these
places, the original carbonats rocks are thoroughly altered in skarns, while the piroclastics
rocks, substantially of very fine grain, they are transformed into cornea rocks. 3.1.5.2 Cornea
Rocks Most of rocks of this unit are associated with the horizons of skarn presence, though
also are found isolated outcrops in the bosom of the piroclastics in contact with any intrusive.
In the sectors of auriferous development of Nambija and Guaysimi the cornea rocks are
presented under the form of rocks of clear green color, of fine texture to aphanitic and of
aspect silicificated. The rocks can show equally fine laminations (2 mm) parallel and be
interstratificade with horizons more bulk of epidote or garnet. Generally, they are not found
meaningful auriferous values in the bosom of this facies; however, it is observed a
mineralized cornea rock, intimately associated with the zones of auriferous skarns, of
obscure green color and of very fine texture. Finally, they are found rocks thoroughly
epidotized, of green pistache color and of aphanitic texture. In the zone of Wells Eight,
several outcrops enclose a mineralogy derived from a metamorphism of contact probably
due to the presence of the intrusive dioritic. In this way, it is note a rock cornea of clear
greenish gray color, of fine texture to aphanitic, with pyrite and chalcopyrite in veins. To the
East of the mountain chain of Nanguipa, to the edge of the batholith granodioritic, are
observed prompt outcrops of skarns and of granodioritic, are observed outcrops prompt of
skarns and of cornea rock in the bosom of the piroclastics. As a rule, the rock is of fine
texture to moderately fine, of obscure green color, with altered zones of pink and clear green
color and veins of epidote. In thin plates, all the described rocks demonstrate a volcanic
origin, belong generally to the litics tuffs with crystals, of fine texture (black tuff V4, ash tuff
V5) and exhibit a metamorphic mineralogy. They are observed various mineralogical
assemblies that understand essentially to the epidote, zoisite, vesubianite, diopside, tremolite
- ferroactinolite and calcite. The counterfoil is frequently chloritized, epidotized and sericitized
could note locally a secondary silicification of all the rock. 3.1.5.3 Skarns (M2) Very few
outcrops of skarns properly said have been able be observed in the mapped region for this
work. They are noted some prompt occurrences within area with geological raising at
recognition level to the East of the mountain chain of Nanguipa that seem be derived from
the metamorphism of thin intercalated carbonates caps with piroclastics rocks. In the center
of the region. In the surroundings of the Wells Eight, it has been verified the presence of
skarns and of cornea rock in touch with the intrusion diorite subvolcanic thoroughly altered
hydrothermally. The West edge of the intrusive presents a skarns of calcics garnets and
carbonateds that derive probably from a carbonated rock, while the eastern extremity is
found a rock base of vesubianite and zoisite that shows an intensive silification and
constitutes, probably, a endoskarn. In the sector Well Ramón is note the presence of
skarns in the bosom of the outcrops of calcareous under the form of small lenses in those
which the contacts continue the stratification plans. In Well Ramón, it can be seen
one of these caps, of about 5 m of thickness, that it has been thoroughly exploited. In this
place, the skarns, of bulk texture, it is composed mainly of calcics garnets, of calcite,
vesubianite, epidote, diopside and quartz, as well as a mineralization of pyrite, pyrrhotite,
chalcopyrite and sphalerite. The piroclastics horizons intercalated with the calcareous are
above all epidotized in these alterations. On the mining developments of Nambija and
Gauysimi are observed auriferous skarns that contain mainly garnets calcics (grossular),
diopside, vesubianite, quartz, calcite and adularia. The calcite, under the form of bulk plates,
alters and includes the vesubianite. Of the same form, the secondary quartz invades the
rock, including and surrounding the metamorphic minerals. The skarns are frequently
presented with tapes in those which can be observed thin striping of clear green color and of
fine grains that represent rock level corneas derived from piroclastics, altering with beds of
skarn of garnets, of texture more bulk. 3.2 TOTAL CHEMICAL ANALYSIS OF ROCK 3.2.1
Sampling and Analysis In order to determine the chemistry nature of the different lithologics
units as well as of the hidrothermals alterations that affect them, it has been selected 94
samples for total analysis. The samples were selected in form such of having a
representative sampling of all the observed facies, so much of the rocks that present few or
no alteration as of those that appear altered in the area. The origin of these samples is as
continues: 22 correspond from the different intrusive rocks, 46 to the sequence of piroclastics
and volcanic, 6 to the outcrops of skarn within the studied region, including 9 samples of the
mine of Nambija and 2 of the mine of Guaysimi. The rock samples have been ground until
obtaining a grain that passes the mesh 200 in the laboratory of the INEMIN, in Chillogallo
(Quito), and transmitted then to the laboratory Bondar - Clegg of Ottawa, Canada. The
chemical analysis has been effected by spectrometrics of the atomic emission of the plasma
for the greater elements such as Si02, Al203, Faith (total), Mg0, Ca0, Na20, K20, Ti02, P205,
Mn0, as well as for the C02 et S (total). 3.2.2 Results The general results are presented in
Annex II - 1.2 for numerical order. Annex includes the corresponding lithologic each sample
as well as a legend of the used abbreviations. All the places of origin of the analyzed
samples are identified on the location map C-1, exception made of 6 samples of skarn
originating from the development of Nambija , (#1287 - A, 1287 - B, 1289, 1336 - C, 1340,
207), and of the two samples of skarn belonging to the development of Guaysimi (#G-2, G-5)
that are located outside of the limits of the map. The remaining three show of Nambija (#
1290 - A, 1290 - B,et 1290 - C) are included in the location map. It should be to note that
most of samples analyzed by the greater elements, they are equally analyzed by 36 smaller
elements. On 46 volcanic rock samples and 22 of intrusive rocks, that is to say, on 68 of 94
analyzed samples have been applied computer procedures. The figures 5 to 9 present the
binary variation graphs of oxides: Na20 K20 versus Si02, for the two groups and K20 versus
Si02, Na20 versus Si02 and Na20 versus K20 for the volcanic rocks only. The number of
each sample is convenient identified above all the graphs and the different lithologics units
are represented by different symbols. 3.2.3 Succinct Interpretation The examination of the
variation graphs indicates in the first place the similarity of composition between the intrusive
and extrusive rocks; the two groups present the same dispersion standard about the curve
that separates the alkaline fields and subalcanics. This characteristic would suggest equally
the character of transition of the originating means in these rocks. Even though the high
alkali contents in certain samples located about the zones of skarns, of smaller defects or of
the intrusive in the case of the piroclastics, demonstrate without no doubts the presence of a
potash alteration in the bosom of the rocks, seems doubtful that this alone fact will be
responsible of the character highly alkaline of certain samples. This situation, to be
compared with the two populations obtained of Na as a result from the processing of the
geochemical data to see chapter 4.2, alone permits to speculate by the moment on the
possibility of the existence of different two episodes of magmatism or of two alteration
episodes potash. In the group of volcanic rocks, seems be noted a trend subalcaline trace alkaline in the piroclástics, while the lava washes relatively little altered found
sporadically in the defect zones associated with the late magmatic episodes, would reveal an
alkaline trend and would belong, therefore, to the basalts alkaline. Of the same form, the
intrusive rocks that present few or no alteration show also a subalcaline trend, except for the
hypoabisal rocks associated equally with the late magmatic events that present compositions
located in the alkaline field. These observations could then to indicate the presence of two
sources or volcanic episodes and of a tectonic means in transition. A tectonic basin
environment after - arch associated with a continental magmatic arch and with volcanism
trace - alkaline, it can be easily considerate. A potash enrichment and an evolution toward
smaller magmatic episodes more alkaline, it is not thing unknown in this type of context
(Reading, 1978; Best, 1982). Finally, the examination of the results of the analysis of the
samples that are presented altered on the area the area does not reveal, to first sight,
differences labeled with the freshest samples, as would have been able to wait. In any case,
is present a potash alteration, such as has gone mentioned before and the figure 9 shows
the relationship inversely proportional between Na20 and K20. it is note equally a trace
alteration – silice in the bosom of the rocks located about zones of skarn. 3.3
STRUCTURAL GEOLOGY 3.3.1 Generalities In the course of the geological raisings, they
have been taken about 2000 structural mediations, the same that they were thereinafter
processed by computer methods. The stereonet obtained are presented in the figures 10 to
15. The studied zone presents mainly flat of defect and faulting and would be interesting to
make a structural raising directly within mineralized sector of Nambija, in order to understand
better the relationships between the same flat and with the zones of mineralización.
3.3.2 Photointerpretation The results of the photogeological interpretation are presented in
the figure 4. The lineaments most labeled to regional scale are guided in the address NS and
seem to delimit a volcanic rocks corridor -sedimentary, in the form of abrupt combs, in the
granitoides bosom rocks that present relief more rounded. The deposits of auriferous skarns
of Cambana, Campanillas, Nambija and Guaysimi are located in the bosom of this rocks
band that seems be extended by several length kilometers. The most attentive examination
of the lineaments NS reveals than would be tried to normal defects, possibly with a of the
central sections and a collapse to the edges East and West. They are presented also
numerous lineament of direction N-NE and NE and limited by the outcrops NS. In the center
of the considerate region is presented an important lineament NW cutting the deposits of
Nambija and Guaysimi. Other general direction elements EW are equally important and cut
the structure NS in one way more extensive. As a rule, the hydrographyc system reflects the
structural lineaments. In conclusion, to the South of the studied region is note a structure in a
way regulation and of origin done not know. Between other possibilities, the structure would
represent traces of an ancient volcanic center. This structure is cut by a lineament NW akin
to that that joins the deposits of Nambija and Guaysimi. In certain zones of the mountain
chains, are found boiler systems associated with the tectonic graves (grabens) and with the
lode deposits (by example., San Juan, Colored, USA). Would be interesting to explore this
structure in form more intense in order to verifying its nature and its importance. 3.3.3
General Structures observed on the Area In general form, all the studied zone is fractured
and failed. Such as indicates it the photogeological interpretation, the region is cut by
numerous and important, with directions N-NE, NE (as the visible defect in the sector of the
mine of Nambija and of the defect throughout the Bankrupt #5) and NW (as the defect that
continues the Bankrupt of the Fierro South and is extended of Nambija to the Guaysimi
Mine). It is observed, also, important defects in direction EW (more precisely to 280°290°). In the Bankrupt of the Fierro, to the center of the studied region, exist flat of shear
and important defects, as well as in the Wells Eight, where a defect EW seems to dial the
edge of an intrusion and gives rise to an important shear zone in the Bankrupt #14. In end, in
the extremity NE of the hill of Mapasingue in the sector of the mine of Nambija, is note a
greater defect plan guided to 280°-290° to what is long of which is observed a
tectonic gap. It is possible that this defect, as that of the Wells Eight, is extended toward the
East, crossing the mountain chain of Nanguipa, such as suggests it the photointerpretation
and the interpretation of the geochemical values in gold that seem to follow these
lineaments. The movements observed throughout the defect plan NS, N-NE they are always
vertical movements, while the horizontal displacements seem have taken place preferably
according to the flat EW. This is particularly evident in the sector of the Playón of the
mine of Nambija, where it can be observed flat two subvertical defects that seem conjugated
with the directions 20° and 110°. The flat NE and NW limited by the defect NS
would represent extence bound fractures to a principal system NS and to secondary systems
N-NE and EW. It is difficult to establish precisely the chronology of the defect plans without a
structural study more meticulous. However, it can be supposed that the first located system
has been the system NS, responsible for the collapses and of the creation of a graben. The
subsequent systems would be the defects NW/SE and NE/SW throughout those which are
found dikes of dolerite and of basalts alkaline, respectively. Finally, they would be intervened
the flat EW and NS, of possibly conjugated way, and the numerous intrusives félsics
would have been inserted according to those fracture plans, as for example the intrusive
volcanic félsic of the Wells Eight or the granitic dikes of the Bankrupt of the Fierro
South. The fact of the that the system NS could have returned to move tardily it is indicated,
between other, by the traces now rectilinear of that primary system. The structural
observations to the scale of the outcrops goes equally in the same way. The systems of
quartz veins - pyrite located in the volcanic are almost exclusively guided according to that
plan and cut often the others systems. The dikes of dolerite, late in relationship to the
volcanic, they are only cut by join and veins of direction NS. Unwillingly to speculate too, we
mention that the defect systems NNE and EW they have been recognized in the Southwest
of the Ecuador, bound to the ENE movement of the Plate of Nazca in the Terciary Superior.
The porphyry copper of Chaucha in the Southwest of the country is located in the
intersection of those two transverse defects (Frutos, 1986). Finally, they have been
measured some tens of stratification plans within the piroclastics and calcareous units ,
demonstrating the direction NW of the caps, with a slope toward the NE in the part West of
the slope band toward the NE in the part West of the band volcanic - sedimentary (sector of
the Mapasingue), and a direction SE, with a dips toward the SW in the part East (sector of
the Well Ramón and of the mountain chain of Nanguipa). This, along with the
lithologic contacts observed, suggests a structure sinclinale with the piroclatics bulk
sediments to the foreign happening to the finest sediments associated with the carbonates
sequences and with the auriferous skarns toward the interiorof the structure. The lineament
NW/SE that cut the deposits of Nambija and Guaysimi would correspond approximately to
the shaft of the structure. Finally, it seems that a defect EW, located in the surroundings of
the Bankrupt of the Fierro, it has given place to the displacement of the structure toward the
left. The determination of the important structural shafts is confirmed by the stereonet
obtained with the computer processing from the data. 3.3.4 Stratification The figure 10
presents the stratification pole means. This graph suggests, of general way, a shaft structure
NW/IS with irregular micropliegues, probably due to the movements throughout the
numerous defects. 3.3.5 Faults The figures 12 and 13 represent the concentrations of the
poles of the defect plans and the strias that are associated respectively. They can be defined
four (4) large plan families. The most important groups to the direction plans N-NE/S-SW
(5° to 20°) and of mainly abrupt slope (70°-90°). A second family would
have as flat middle a direction NE/SW (30°) with a slope 55° to 70°. A third
family would follow a direction NE/SW (40°) abrupt slope by 80° to 90°.
Finally, a last family, less important by the fractures density that characterizes it, with a
direction between 90° and 115° and a slope on the SW of about 50° to
80°. 3.3.6 Join The figure 11 represents the graph of density contours of the fracture
poles. The join with direction multidirectional with generally abrupt slopes. In spite of all, the
most frequent systems are substantially the same than for the defects, that is to say, the
systems N-NE/S-SW, NE/SW, E-W, and a plans family less important NW/SE. 3.3.7 Veins
The veins (fig. 14) are guided continuing the important fractures system, that is to say, in
connection with a flat N-NE (5°-10°) with a mean slope of 65°. Other two
secondary plans can be equally observed according to the hosiery directions of
NE/SW(60°-80°) and NW/SE (300°-330°) with subverticales slopes. 3.3.8
Dikes The figure 15 presents a graph of directions and slope poles of the dikes, with different
symbols according to their composition. As a rule, the plans compiled in this graph show a
mean direction NW-SE. 4. GEOCHEMICAL OF THE ROCKS AND OF THE HEAVY
MINERALS 4.1 INTRODUCTION AND USED METHODS During the geological cartography
campaign, they have been gathered systematically superficial rock samples as well as
samples of the heavy fraction of the sediments in the creeks, these last concentrated using
bat that are employed to carry gold. They have been obtained 565 sample rocks and 321
sample sediments, what makes a total of 886 samples. These samples have been
withdrawals above all within the region of 682 hectares but also in the recognition zone of 18
km2. the site of the sample points is indicated in the Maps C-1 and D-1, respectively. The
sample rocks have been mashed in the laboratory of the INEMIN, in Chillogallo (in Quito),
until the resulting material pass the mesh 200 and then they have been sent to be analyzed
in the laboratory Bondar-Clegg, of Ottawa, Canada. The heavy mineral samples have been
also ground in this same laboratory. 866 samples have been analyzed by neutronic
activation simultaneously to the gold and to 33 elements more and by atomic absorption to
the copper and to the lead. The results have been send to Géomines in diskettes and
transferred then to our electronic file. An impression of this file, including all the results of the
analysis and the coordinates of each sample, figure in Annexes II - 1.1 and III - 1. The data
of this file have been processed numerically with help of the program GDM (Geological Date
Management) in a computer IBM PC-AT. The rocks and the heavy minerals have been
treated separately to produce the following documents: tables of statistics base, counterfoils
correlation, histograms of laws, binary graphs and geochemical maps to scale 1:5000. For
the binary graphs, it has been used the logarithmic scale in reason to the great extension of
the values (to see Table 1). The histograms show the distribution of the concentrations of
each investigated element. For the same previous reason, not always results possible to
present graphically the whole the laws, so that in some histograms has been necessary to
put explanatory notes. The geochemical maps to the scale 1:5000 show, with the aid of
symbols, the distribution of the laws within the region of each one of the considerate
elements. Additionally, it has been indicated with a black point above all the geochemical
maps, the site of 32 sample rocks in those which the concentration of the gold is presented
anomalous, i.e. 100ppb (to see chapter 4.2). 4.2 GEOCHEMICAL OF THE ROCKS The
examination of the histograms of laws of gold in the analyzed rocks has permitted to define
the anomalous concentrations limit in 100 ppb, above the one which exist 32 samples.
Confronting the geometric averages of the laws of each element of this subgroup (Table 1) is
observed that the average of the average is topmost for the arsenic, the fierro and the lead
and bottommost for the sodium and the bario (has not been taken into account the tungsten
on account of the pollution had to the crushing). These five elements have been considered
as accompanist elements of the gold and therefore they have been elaborated the
histograms (Annex II - 2), the binary graphs of each one of them versus the gold(Annex II - 4)
and the geochemical maps to the scale 1:5,000 of the distribution of each one of these
elements within the region (Maps C-2 to C-7). The laws of gold in the rocks of the region vary
from less values than the direction index (5 ppb) until a maximum of 37,900 ppb (Table 1).
The anomalous laws(>100 ppb) are frequently associated with the defects or with the
shear zones and appear some times aligned according to the greater defect plans, as for
example throughout the Bankrupt of the Fierro - The Diamond, with a possible prolongation
to the East of the comb of the mountain chain of Nanguipa. In the Northwest corner of the
zone, the anomalous values , is note a values concentration increased in the extreme part
North of the region, about deposit of Nambija. It is of noting that to the East of the comb of
the mountain chain of Nanguipa, the laws of gold are generally very decrease with exception
of one of them . The laws of arsenic in the rocks of the region vary from smaller values than
the detection index (1 ppm) until a maximum of 383 ppm. The great majority of laws are
located in less than 40 ppm and the geometric average is of 4.99 ppm (to see Table 1). The
anomalous concentrations are found grouped within the region of Mapasingue, where the
laws of gold are relatively high, and directly to the such region South, in the sector of
"The Wells Eight", where the laws of gold are rather decreases. In the Bankrupt
of the Wasps, to the East of the comb of the mountain chain of Nanguipa, there is a certain
correspondence between the high values of the laws of the gold and of the arsenic. In the
others places (for example more to the West and to the Southwest), where the laws of gold
are increased, there is no correspondence with the arsenic. These observations demonstrate
the limited value of the arsenic as indicative of the gold presence within the region in study.
The presence of the fierro in the rocks varies also from laws more decreases than the
detection limit (i.e. 0.5%) until a maximum of 43%. The great majority of the laws is being in
less than 10% and the geometric average is of 3.8% (to see Table 1 and Annex II - 3). The
high laws are generally associated with the presence of the pyrite. The fierro is a staunch
companion of the gold in all the areas of the world (Boyle, 1979) and Nambija is not an
exception. The fierro continues very near to the gold in the sense of the fact that where the
values of the gold are increased, those of fierro are also and conversely (to see Map C-4).
The content in lead in the rocks varies from smaller laws than the detection index (i.e 2 ppm)
until a maximum of 10,600 ppm with a geometric average of 6.47 ppm (Table 1). Though the
geometric average will be topmost for the samples with gold to >100 ppb that for the
whole the samples, there is no actually correlation between the lead and the gold. This is
evident in the binary graph (Annex II - 4) where, for the major share of the anomalous
samples in gold, the corresponding value in lead is not very high. Observing the geochemical
map of the element (Map C-5), stressed remain that the high lead concentrations are found
grouped in two sites in particular: "Well Ramón" and the "Wells
Eight". In first case, is found also a little of zinc associated with the anomalous low laws
of bario. From the geological point of view is found within the calcareous stratified where is
found galena and sphalerite. The wells have been abandoned after a first attempt of
development on account of a decrease law of gold. In the "Wells Eight" the high
laws of lead also they are associated with the decrease laws of bario. It is found a little of
skarn, but the principal rock is an altered tuff. The wells have been quickly abandoned.
However, the first accompanies to the gold in the Bankrupt to the West, in an important
defect zone. Agree to note that the corresponding sodium contents are particularly low. It is
found also a series of anomalous lead concentrations aligned according to a shaft NS, on a
parallel located to the East of the comb of the mountain chain of Nanguipa. The law of bario
in the rocks varies from values less than the detection index (100 ppm) until a maximum of
28,200 ppm, with a geometric average of 458 ppm (Table 1). For the group of samples in
those which the gold is anomalous, the corresponding geometric average to the bario is of
217 ppm (Table 2), quite bottommost that for the set of the samples. On the binary graph
(Annex II - 4) is seen clearly this trend. In the geochemical map of the element (Map C-6),
the anomalous low values of bario are generally associated with the high laws of gold, but
are found also decrease laws of bario in the region of "Well Ramón" and
"Wells Eight". Furthermore, is evidence a alineament of anomalous values of
bario on the flank East of the mountain chain of Nanguipa. The sodium characteristics in the
rocks vary from 0.1 to 6.7% with a geometric average of 1.6%. for 32 samples, in those
which the gold content is superior to 100 ppb, this average is of 0.2%, highly bottommost.
According to the binary graph of the sodium versus the gold (Annex II - 4) seems have two
(2) populations: a first with high sodium values for the laws of gold less than 100 ppm and a
second population with decrease laws of sodium. On the geochemical map of the sodium
(Map C-7) is seen that the low laws of this element are associated with the high gold
contents. But is found also places, as "Well Ramón", where there is no
practically gold, but lead and zinc associated with decrease laws of sodium. The sodium
would would have, then, scarce value as indicative of the gold in the region. In the chapter
3.2, they have been bought the values of k20 versus the values of Na20 for 46 volcanic rock
samples in those which have been effected total analysis. Turned out to be it a relationship
inversely proportional. Would be interesting to analyze the whole of the taken samples of the
region in relationship to their contained of potassium and to put the results on a map in order
to seeing if it can be located in this way the potash alteration zones that they would be
perhaps bound to the presence of the gold. 4.3 GEOCHEMICAL OF THE HEAVY
MINERALS For 321 samples of the heavy fraction of the collected river sediments and
concentrate by batting and then analyzed by 36 elements (Annex III - 1), it has been
elaborated also a table of statistics base(Table 3), two correlation counterfoils: arithmetic and
logarithmic (Annex III - 3), a histogram of gold concentrations (Annex III - 2) and the
geochemical map of the gold (Map D-2). Furthermore, the same as for the rock samples, it
has been elaborated a statistics table for the samples that had high gold concentrations, or
rather greater than 1500 ppb (Table 4). Comparing the geometric hosieries of the elements
of this table with those of the whole the samples, evidenced remain that the average is
topmost in the subgroup for the arsenic, the antimony, the bario and the tungsten, those
which would be therefore accompanied elements of the gold in the concentrate by batting.
For this study have been considered solely the values of the gold, seen that it is the own gold
indicative the best by the gold. The law varies from values less than the detection index (5
ppb) until a maximum of 41,500 ppb, with a geometric average of 182 ppb. On the
geochemical map of the present gold in the concentrate by batting, is seen that the contents
increased in gold are found grouped in four places in particular: - Firstly, in the lion\'s share of
the creeks that drenan the South flank of Mapasingue, in the sector NW of the region, what
does not result surprising if is considered the proximity of the deposit of Nambija. - In the
second place, is found a concentration of high laws in the center section - south of the
Bankrupt of the Fierro. This anomaly is interesting on account of the favorable conjuncture:
important defect and proximity of volcanic rocks of fine grain (frequently associated with
calcareous) (to see chapter 5). - A third high values concentration of the gold content in the
bat is found in the recognition zone, in the corner SW of the region of the Bankrupt 24, where
nearly all the samples present values. Considering that is added to this the proximity of an
important defect in direction NS, the anomaly results very interesting. Since the laws of gold
are very high, it is possible that it will be due to the presence of this metal in the form of pips,
what would be possibly associated with a porphyry (seen the predominance of intrusive in
that sector). Of all way would be needed to make a geological mapped and a more detailed
sampling in this sector. - A fourth anomaly, also in the recognition zone, is found in the sector
SE of the region, waters down of the auriferous deposit of Guaysimi, on current
development, on the Bankrupt #22. the taken sample waters up present the risk of be
contaminated by the relaves of the mines, but the four anomalous values samples have been
taken waters down, in the affluent that come of the West. This zone would deserve be better
examined: in addition to the anomalous values found in the bat, it should be take into
account the presence of a great calcareous rolled song observed in the Bankrupt #22,
between the samples B92 et ++B93. Additionally, the existing geological conditions on the
flank East of the comb of the mountain chain Nanguipa would be favorable to the presence
of skarn: or rather volcanic sediments mapping not far from there, possibly with intercalates
of calcareous (the rolled song) and the proximity of an important defect in the address NS
throughout the comb. 5. METALLOGENIC 5.1 GENERALITIES This chapter presents the
conclusions of a paragenetic study accomplished in order to define a metallogenic model of
the deposit of Nambija. The surface covered by our field projects do not include own deposit
of Nambija. Having accomplished solely two project sessions and available having only the
taken samples, the conclusions that are presented are proposed solely as a first stage within
elaboration process of a genetic model of the deposit. It will be recommended to effect
subsequent stratified studies, , structural and paragenetics, in the same sites of all the
deposits known of the volcanic - sedimentary band (Cambana, Campanilla, Nambija and
Guaysimi) in parallel with studies of the regional geological context in order to specifying the
model. The examined samples have been taken in the sectors of Mapasingue, of The Arch
and of the Playón in the mineralized zone of Nambija, in the mine Guaysimi during a
visit to the earthly, as well as in different places included in the mapped surface to the detail,
mainly in the sector of the Well Ramón. The paragenetic study has encompassed: 1)
A megascopic evaluation of the alteration within the skarns and the associated volcanic
rocks, including alteration tests potash. 2) An examination in polished thin plates of the
skarns auriferous and sterile. 3) A tending bibliographical conference to compare these
deposits with the others auriferous skarns (to see Annex I SAW - 2). 5.2 CONTEXT
LITHOLOGICAL AND STRUCTURAL OF THE GOLD MINERALIZATIONS The auriferous
mineralizations are located within the skarns in the bosom of a volcanic - sedimentary
sequence. This last constitutes a rocks band of some kilometers of broad, of direction NS
and of unknown extension, limited to each side by defects that seem to define a tectonic pit
(record) to the interior of a batholith granogioritic. The sequence is constituted of piroclastics
(volcanic breccia, block tuffs and lapillis, crystals and ash tuffs) and of volcanic mixed
alkaline and trace - alkaline (basalts alkaline, andesite, dacite) within those which are
intercalated thin horizons of calcareous (sands and calcareous shales). The set is cut by
dikes and by small stocks of diorite, applies and subvolcanics rocks of similar compositions
to the extrusive rocks. They have not been observed sedimentary pelitics rocks. The
sequence volcanic - sedimentary is affected by foulding more or less irregular than define
globally a synclinal structure of shaft NW/SE, strongly cut by defects N-S, N-NE, NW/SE,
NE/SW with vertical movements and by defects E-W throughout those which have been
produced horizontal displacement. Of the foreign toward the interior of the sinclinal is gone
from bulk piroclastics facies toward the finest facies. They are observed two types of skarn in
the region. The first, it is located in the eastern part of the studied zone (Well
Ramón), it is in touch of defect with piroclastics means to bulk. The values in gold are
weak and the mineralization observed is constituted by pyrite, chalcopyrite and sphalerite
with a little of galena. The auriferous skarns properly said are located in the center of the
studied region, in the heart of the synforme structure and they are associated with the ash
tuffs being able to be presented finally laminated, silicated and metamorphosed. The
magnetic susceptibilities of these rocks seem be more decreases than of the surrounding
rocks, what remain demonstrated by the geophysical raising. The explanation of this fact intrinsic properties of the rocks or product of the hydrothermal alteration very intensive - is
still unknown. It is note equally the stocks presence and of dioritics dikes as well as of
subvolcanics intrusions mineralizated in pyrite in contact of the skarns. In the mine of
Nambija, sector of the Playón, it has been observed locally a rock that is resembled
to a intrusive breccia (diatreme) associated with the mineralized zones. Finally, the deposit of
Guaysimi, located within same type of rock that of Nambija, is found in the prolongation of
the lineament NW/SE that defines the shaft of the sinclinal. 5.3 MORPHOLOGY OF THE
DEPOSITS The mineralization auriferous economic seems bound exclusively to the horizons
of skarns and of intercalated cornea rocks, though is note also an enrichment in gold of the
greater defect zones inside of the volcanic rocks. The levels of calcareous, skarns and ashes
more competent constitute very fractured and permeable trainings than permit the passage
of mineralized solutions. The matters precipitants presence (Fe, C02) can equally to play a
trap geochemical role in addition to structural trap originated by the great number of
fractures. In Nambija, the auriferous mineralization is presented under the form of gold in
native state, so much disseminated in the rock, more frequently between the garnets of the
skarns of bulk texture (derivatives from the metamorphism of carbonates rocks quite pure),
as of the lenses or of the quartz veins - potash feldspars that cut the skarns and the cornea
rocks (derivatives from the metamorphism of the piroclastics rocks). In Guaysimi, the context
is similar. The observed typical sequence, according to certain mining, they would be tuffs
altered by elements (calls "quartzite"), followed by laminated metamorphosed
tuffs in cornea rocks, of clear green color, followed after gaps (not always present) and by
skarn properly said. The mineralization is disseminated in the skarns but in certain zones, is
presented under the form of veins of quartz - potash feldspars that cut all the sequence
before described. 5.4 ALTERATION HYDROTHERMAL An megascopic examination of
about 25 samples originating from the mapped sector and of the deposit of Nambija indicates
two types of important alteration: 1) A potash Alteration in the igneous rocks and piroclastics.
This alteration understands the replacement of the plagioclases, in the form of phenocrysts
and within the counterfoil, by a potash feldspars and by the epidote as well as the
replacement of the amphiboles for the biotite or the chlorite. The pyrite can be introduced in
the fractures. The dyed of the samples with cobaltinitrito of sodium indicates that all the rocks
are altered, unless possibly the aplits, in those which the dye is presented weak. The potash
intensive alteration is manifested by a pink color alteration, beige or gray pale in the
counterfoil of the rock (#1056 a, 1056c, 1065 a, 1175, 1329c) throughout the veins and
fractures (#79 a, 209, 1033 a). The phenocrysts of plagioclase are thoroughly replaced
(1329c) or altered throughout the plans of cleavage (#1056 to). The sample #1037b presents
an potash alteration cut by a sterile quartz vein. 2) Alteration of calco - silícea of the
calcareous (exoskarns)and, in touch with the exoskarns, a similar but limited alteration of the
piroclastics (endoskarns). The exoskarns are characterized by a trace assembly silíce of grain means of green color, beige or brown pale. The mineralogy and the
paragenesis of the exoskarns are described in the following chapter. 5.5 PARAGENETIC OF
THE SKARNS COPPER The primary skarns of Nambija present texture and simple
mineralogy, with an assembly of seed clinopiroxene of grain means. The garnet crystals
(70%) are mainly allotriomorfos and of 0.5 to 1mm of broad. Furthermore, the crystals have
concentric colored bands and they are anisotropics and distorted. The deformation textures
include you laminate and "kinks" of sobretensión, waved extinctions and
cataclastics textures (fracturación, brechificación). In a originating sample
from the surroundings Well Ramón (1329C) is observed a garnet isotropic idiomorfo
that replaces to the anisotrópicos garnets (photo 21), what indicates at least two
garnet generations, being the most subsequent youths to the deformation than there have
sobretensionado the precocious garnets. Chemically, the garnets are members of the series
of the solid solution grossular-andradite (C03(A1, Fe)2Si3012). The color beige of the
garnets suggests mainly the grossular, while the andradite is customarily of obscure color.
The clinopyroxenes (30%) are of the series diopsida-salita, with allotrimorfos crystals of up to
0.5 mm of length that form irregularmixed bulks with the garnet crystals. It is observed, they
associated with the diopside, about 1% of grains of pyrite and of chalcopyrite as well as trace
of calcite and of epidote. In the sample 1329C, the sphalerite (10%) fill the fractures and
provide the breccia characteristic to the garnets (photo 22). This texture represents a
removilization of mineralization primary associated with a deformation. The primary assembly
is retrogradado in a sample originating from Well Ramón by an episode of zinc
mineralization. The bulks of sphalerite that house small incorporation of chalcopyrite and of
galena (<0.1 mm of broad) are associated with an assembly of pyrite - chancopyrite calcite - quartz – chlorite - tremolite - epidote. The primary assembly of the skarns is
also retrogrado for the episode of auriferous mineralization. To megascopica scale are
observed small lenses and discontinue veins (tension fissures) of quartz – k-feldspar calcite – hematite – chlorite – zoisite – gold, that alter the skarn.
The quartz, the hematite and the zoisite fibrous replace to the garnet, while the calcite and
the hematite replace to the diopside. The pyrite is replaced by the hematite. The adularia is
identified by the morphology of the potash feldspars. This secondary assembly replace to the
primary minerals in the edge of the veins and also in the nets of microfracturas present in the
skarns. Small veins of late sericite cut the auriferous assembly. The gold is found in the form
of grains or of allotriomorfas bulks of 0.1 to 5mm of broad in the skarns altered or in the veins
(photo 23). No silver-bearing phase or other sulfurized phase has been observed in the
veins, indicating that this mineralizador episode is substantially monometalic. The sample
70ª. Taken in the Bankrupt of the fierro, a located defect zone outside of the zone of
skarns auriferous, it is a skarn thoroughly retrogradado in an assembly of chlorite - hematite quartz -calcite. This sample is anomalous in gold (1860 @@ppb Au) and is presumed that
this alteration is the result, perhaps the equivalent distal, of the episode of auriferous
mineralization, though in native gold and the adularia are absent. In short, they are
recognized three states of mineralization in the studied samples (figure 16): 1) Primary
Mineralization of pyrite - sphalerite - chalcopyrite continuing a deformation of the assembly of
skarn; 2) Secondary Mineralizacion of sphalerite - pyrite - chalcopyrite - galena that there has
retrogradado the assembly of skarn; 3) Auriferous Mineralization of the type lode that also
there has retrogradado the primary assembly. Though it can not be determined the
paragenetic relationship between the states 2 and 3, is presumed that the stadium 2
constitutes a secondary mesothermal alteration of the skarn and that it is older than the
episode of auriferous mineralization. 5.6 DISCUSSION The skarns of the region of Nambija
present the characteristics of the calcics skarns coppers. These characteristics include: 1)
Mineralization of pyrite, pyrrhotite, chalcopyrite and sphalerite in a trace bargain - silicea of
garnet (andradite-grossular), diopside, wollastonite, magnetite, etc. 2)
Retrogradación of the primary skarns by late mesothermales processes. 3)
Association to the trace calco - alkaline intrusions (diorite, granodiorite, Qz monzonite). 4)
Tapping of metasomatism of calcareous beds in the volcanic cogenetics sequences
(andesites, dacite). 5) Middle tectonic orogenic of continental arch (Einaudi et al., 1981;
Einaudi and Burt, 1982). We think that the skarns studied are derived from a metasomatism
of calcareous observed in the volcanic sequence -sedimentary. The presence of piroclastics
altered is not unknown in means hydrothermales and the training of skarns in the igneous
rocks (endoskarns) is typically a local process (Einaudi et to the., 1981; Meinert, 1986). The
skarns of Nambija are poor in sulphurs (pyrite, chalcopyrite, sphalerite late) and they are
associated with an activity hydrothermal apparently bound to the intrusions dioritics local.
The alteration potash important of the piroclastics, the volcanic and the intrusions
subvolcanics is geographically associated with the skrans and it is probably contemporary to
the training of they. The alteration potash of the igneous rocks or pelítics associated
with the genesis of the skarns coppers that is all right documented (Einaudi et to the., 1981;
Carten, 1986; Wares 1986). The auriferous mineralization is very rich in the skarns. The gold
is presented in native state, mainly housed in the discontinue veins that fill the tension
fissures, what represents a state of the type secondary lode that was seeming be
independent to the training of the skarns. The mineral assembly 2gico of the veins indicates
an epithermal episode (<300°C) of type adularia-sericita (Hayba, 1985), while the
skarns are normally formed at high temperatures (400°-600°C, mesothermals
conditions). It has not been observed no auriferous mineralization in the volcanic rocks,
except for the piroclastics levels intercalated with the skarns. Alone have been found quartz
veins slightly pyritized that cut the potash alteration, what seems particular because,
customarily, the epithermals deposits of type adularia-sericite are associated with defect
zones or they are housed in a variety of lithologics, mainly of volcanic calco - acaline. This
type of mineralization is normally deposited a million of years after the training of the hosted
rock rocks. These facts indicate that the structural controls on this epigenetic mineralization
are more important than the nature of the hosted rock rocks (Buchanan, 1981; Hayba, 1985).
Thus the auriferous mineralization of Nambija represents a particular situation where the
skarns have served as structural traps or, being rich in fierro, of geochemicals traps where
the structures have permitted an infiltration of the bearing gold fluids. The receiving behavior
of the lithologic ferríferas on the auriferous bisulfurados fluids is documented for the
trainings of fierro of the Precámbric (Phillips et al., 1984), what can be relevant in
relationship to the skarns studied. At world level, the skarns of Nambija are compared with
difficulty to the skarns known, yet if these last have been formed in similar tectonic means
(Einaudi, 1981, 1982), already they will be the means of the oceanic arch or of the orogenics
continental edges (principal arch and hind arch). The "auriferous" skarns are
typically ferríferos or coppers skarns where the gold is extracted as by-product from
the development from the usual metals (Einaudi et al., 1981; Shimazaki, 1980; Mainert,
1986). These skarns are generally poor in gold (<3g/t ++Au) and the metal form part of the
primary mineralization or it is enriched in the polimetalics mesothermals veins that alter the
skarns. The auriferous mineralization is frequently it associated with the pyrite
nickelífera and cobaltífera in the ferríferos skarns and with the small
quantities of bornite/calcosina, arsenopyrite, sulphur of bismuto, telururos or sulfosales in the
coppers skarns. Table 5 summarizes the characteristics of the exploited skarns by the usual
metals and by the gold. The auriferous deposits of the region of Nambija present a form of
uncommon mineralization. In Ecuador, as in the Peru, the mineralizations of usual metals of
type skarn and the polimetalics/auriferous mineralizations of the type epithermal lode are
found almost exclusively in the volcanic Mesozoics and Cenozoics of the Western mountain
chain (Petersen, 1965, 1977, 1979; Goossens, 1972, 1976). Nambija constitutes then a
discovery only of hydrothermal mineralization cutting a calcic copper skarn. The exact
geological context of the region of Nambija stays uncertain, taking into account the following
facts: 1) The subandian zone is a waist ridden in active comprehension; 2) The volcanic sedimentary band is limited by defects (where the in-depth nature is unknown); the band
defines a lineament NS according to the air photograph; 3) The rocks within the band are not
submitted to a metamorphism of contact. We permitted ourselves to speculate that the band
is housed in a thin laminates ridden between two intrusives with important horizontal
displacement. The absence of metamorphism of contact excludes the possibility of a gigantic
enclave (roof pendant) within the batholiths. The alkaline mixed nature/trace - alkaline of the
volcanic compatible with the training of a hind arch basin (graben) that in the origin was,
probably, the means of sequence accumulation volcanic - sedimentary The Andean tectonic
evolution consists of a successive stages overlapping of compressions with foulding, inverse
defects and intrusive magmatism followed by extended periods characterized by the normal
defects occurrence, development of grabens and predominance of intrusive magmatism. The
singenetic deformation textures within the skarns (garnets sobretensionados, epithermales
veins within the tension fissures) attest the deposits training in a means in comprehension
state. This fact would explain the overlapping of two types of mineralization (epithermal and
skarn) in the deposits if is speculated that, continuing the sequence training volcanic sedimentary has been transported at lithotectonics topmost levels, permitting the epithermal
mineralization under the conditions of <300°C and of <0.1 kb. In resume, the
auriferous mineralization of the skarns of Nambija is highly secondary. These skarns are
different of the auriferous typical skarns by virtue of the wealth and of the monometalic and
epithermal nature of the mineralization. We concluded then in which the mineralization can
not be classified as type " auriferous skarn ", since it constitutes a auriferous
epithermal mineralization housed in a skarn. This discovery is economic and geologically
important because indicates the existence of an economic potential for the epithermals
auriferous deposits not only in the subandian zone, but in the coppers skarns as a rule. 6.
CONCLUSIONS AND RECOMMENDATIONS 6.1 CONCLUSIONS From the geological point
of view, is found a rocks volcanic -sedimentary guided in direction NS of some kilometers of
broad that houses to the auriferous mineralizations. This band is found in the bosom of a
batholith granodioritic composition. The auriferous mineralization is associated with skarns
and with piroclastics fine rocks. The set is cut by dikes and small stocks of diorite, aplita and
subvolcanics rocks. Locally, they are observed also volcanic and late doleritas in the defect
and shear zones. From the metallogenic point of view, the auriferous mineralization in the
skarns of Nambija is highly secondary. These skarns are different of the auriferous typical
skarns by virtue of their wealth and of the monometalic and epithermal nature of the
mineralization. We concluded that the mineralization can not be classified as of the type
"skarn auriferous", since constitutes an auriferous epithermal mineralization
housed in a skarn and represents therefore a new style of mineralization in the Andes. From
the geochemical point of view, the determination of the gold in the concentrate materials to
the bats seems us the most useful way prospectus gold in the region. Three characteristic
zones have been determined in this way (to see recommendations). The geochemical of the
rocks indicates us that the lead is associated with the large defect zones(current
phenomenon in the grabens zones) and that the gold seems associated with arsenic in the
favorable lithologcs related to a structural control NW-SE. The magnetometrics and
electromagnetic geophysical raisings VLF have been useful to help mapping the lithologics
units, but not directly to recognize the auriferous zones. A summary inspection of the same
deposit of Nambija leads us to believe that the auriferous mineralization would be distributed
in small rich lenses in gold in the skarns, but also under the form of stockworks and would be
associated with the stocks and intrusive lode rocks as well as with the controls of structural
order. 6.2 RECOMMENDATIONS 6.2.1 To effect an air photographic raising in order to
produce a series of airphotographics more detailed . 6.2.2 Photogeological study of these
photos and regional mapped in order to specifying the regional geological context, especially
the extension of the band volcanic - sedimentary and the structure (especially the grabens
and the boilers). 6.2.3 Samples litogeochemical analysis for the potassium in order to
delimiting the alteration potash zones (those with a high relationship k : Na). 6.2.4 Follow-up
of the three (3) characteristic zones determined by the anomalous gold presence in the
heavy sediment samples: detailed mapped, closed sampling of heavy sediments,
litogeochemical sampling for the gold, the sodium and the potassium. The skarns zones
associated with the intrusive rocks and of lineament in direction NW, the skarns are
frequently about tuffs to fine grain. In the corner SW of the recognition zone, the geological
characteristic zone possibly a phorphyry granitic. 6.2.5 Geophysical magnetrometric and
electromagnetic raisings VLF on the deposits known of Nambija, Cambana, Campanilla and
Guaysimi in order to determining if agreing to use these methods with the purpose of
exploration. Annex IV: Geophysical Report 1. INTRODUCTION In the area of the South East project, of Ecuador, they have been effected magnetrometrics raisings to total field, as
well as electromagnetic raisings T.B.F. (VLM-EM) from August 27 and October 1st, 1987.
These raisings have been effected with the principal purpose from obtaining basic
information that serves of support for the best geological knowledge of the earthly and also in
order to seek the geophysical evidence in relationship to the prolongation of the deposit of
Nambija southward, that is to say, within area where was developed our investigations. 2.
PERSONAL In the raisings has participated the following personal: - J. Stembera,
geophysical responsible of the project. - A. Bastien, technical. - 2 Workers. 3. LOCATION
The geophysical mesh is located between the Bankrupt of the Fierro and the North limit of
the area of the project. The site of the principal lines in direction East - West has been
determined by the presumed North - South direction of the general structures, accordant is
detached of the analysis of the air photographs, as well as by the distribution of the field
workers that they have accomplished before the arrival of the geophysical equipment. It is
important to indicate that, in some places, the site of the lines has been influenced by the
inaccessibility of the earthly. 4. ACCOMPLISHED PROJECTS MagnetomEtrics raisings to
total field: 15.0 km Raisings VLF-EM, Station NAU :15.7 km Station NLK :13.9 km The
readings have been taken each 12.5 m for the magnetomEtrics raisings and each 25.0 m for
the raisings. The lines have been signaled with stakes located each 25.0 measured m
horizontally. The lines LB 0+00 have served as base to certify the mesh. In order to have a
fixed reference point for the successive workers, it has been installed a concrete plate in the
progressive 0+75E of the line LB 0+00. 5. RAISINGS MAGNETOMETRIC 5.1
Instrumentation The magnetometric raisings has been executed with the aid of a nuclear
procession appliance, model G-856A of GEOMETRICS. To permit the due alterations to the
daytime variations, it has been installed in the place a base station that it has operated
during the execution of all the raising . The precision of the appliance is of 0.5 gamma. 5.2
Results The results were presented in the form of profile on a map of field total values (Map
E-1). Furthermore, is included a map of field total contours. The base level in the profiles
map is of 29500 gammas. The position of the magnetic bodies is represented by a shaft that
joins the center of the anomalies of each profile. The lines 4+875N and the part North of the
line 8+75E were not lifted due to technical problems. 5.3 Interpretation The magnetometric
raising has revealed many zones with different magnetic susceptibilities, indicating thus the
existence of litostratified different units. We indicate, at the same time, that the intensity
variations are, as a rule, between 100 and 500 gammas approximately. The magnetic relief
in the West part of the zone of the project is more stressed between the lines LB 0+00 and
2+00S of the map E-1. the relief is composed of four (4) magnetic shafts - not. 1,2,3 and 4.
the intensity vary between 100 and 400 gammas and suggest the presence of a quite
physical means homogeneous (intrusive body) possibly shortened by dikes or lavas washes.
Seem also that this unit would be extended toward the East until approximately 10+00W
(above all between the lines LB O+OO and L 1+00S), being associated to the conducting
shaft T.B.F not. 3(Map E-3). In the central part of the area of the project, between the lines
LR 4+00W, and 8+00W, are observed two (2) magnetic shafts # 5 and 6 (Map E-1) with an
intensity of 200-400 gammas approximately. It should be to note that the shaft # 5 probably it
does not continue until the line 4+50S since the intensity on this line is less strong, of the
order of 100-150 gammas. The magnetic shaft # 7 (Map E-1) is not associated with the
mentioned shafts previously, being able to the same to continue until the shaft # 5 on the line
2+00S. This possibility seems be reinforced by the decreases magnetic intensity of its West
flank that they can be observed until the line 1+00S, suggesting thus the presence of a
defect NW - SE, or the presence of a dike with the same direction, in the prolongation of the
outcrops of basalt aclcaline trachytic observed in the Bankrupt # 5. The shafts # 8,9 and 10
(Map E-1) between the lines 3+50S and 4+50S delimit rocks of possibly volcanic origin that
present highly stronger susceptibilities than the rocks located to the North, that is to say,
between the lines LB 0+00 and 2+00S. This zone is extended perhaps until 2+00E
approximately (on the lines 3+50S and 4+50S) and their limit is labeled by the magnetic shaft
# 12. It is observed, on the flank East of the shaft # 12 (Map E-1), a magnetic depression of
clean-looking continuity that is extended northward, to the progressive 362.5E (L4+50S),
337.5E (L3+50S), 237.5E (L2+00S) and perhaps to 2+00E (l1+00S). This zone would
represent phyllitic rock bands limited on the flank East by the magnetic shaft # 13 of the line
L2+00S(Map E-1). The magnetic shaft # 14 (Map E-1), with a nearby intensity to 200-400
gammas, delimited probably the West flank of a intrusive is associated to the weak magnetic
intensity; it seems be recovered in its North extremity by the volcanic rocks, what can explain
the strongest intensity, of about 100 ranges, on the line 1+50N. 6. ELECTROMAGNETIC
RAISINGS T.B.F. 6.1 Instrumentation This raising has been accomplished simultaneously
with the magnetic raising, using an appliance CRONE RADEM of Crone Geophysics that
permits to measure the slope angle (dip angle) of the great shaft of the polarization ellipse.
The measures were taken each 25 m and immediately filtered and transformed continuing
the method FRASER. As source networks have been used two stations T.B.F - Puerto Rico
(NAU) to 28.5 kHz and Seattle, Washington (NLK) to 24.8 kHz. Initially had been chosen the
station Laulauli of Hawai, but it had to be abandoned on account of its weak sign. 6.2 Results
The results obtained with the station NAU, that it was selected as principal station, are
presented in the form of a profiles map (Map E-3). The lines East - West of the discussed
raising mesh are in relationship to the direction given by the network station. Additionally, the
anomalies of the station PR are represented in the form of contours (Map E-4) in a filter map
Fraser on the slope angle (such as is described in Geophysics, Vol. 34, 1969). For the
interpretation of the results it has adopted the convention of Crone. It should be to note that
the values on the North - South lines have been incorporated in the computer treatment of
the contours, causing thus a light certain anomalies displacement on the map Fraser, without
influencing, however, on the quality of the results. The network station SW has been related
to the North - South lines of the traced mesh (Map E-5). The lines 1+50N, 12+00W, 14+25W
and a part of 1+00S have not been lifted on account of an interruption in the sign of the
station. One must to note that the quality of the results of the station SW are not all
satisfactory due to the weakness of the sign. However, the obtained results have been
incorporated in the report. 6.3 Interpretation They have been identified seven (7) numbered
different conducting zones of the 1 to the 7 on the map Fraser of the station NAU (Map E-4),
probably located in the rock. Conducting Zones 1 and 2 These two (2) conducting zones
appear in the West corner of the area of the project, between the lines LB0+00 and L2+00S
(zone 1) and LB 0+00 and 4+50S (zone 2). They correspond to the conducting shafts T.B.E
1, 2 and 3. The zone 1 reaches an intensity of 1 degrees Fraser and shows a good
association with the shafts of the magnetic bodies 1 and 2 (Map E-1) that represent magnetic
intensity of the order of 200 to 300 gammas. The type of the magnetic anomaly indicates that
would be tried to susceptibility contrasts either due to the lithologic abrupt changes, those
which can be indeed associated with a intrusive shortened by dikes or to a zones of direction
defects N-NE. The conducting zone 2 ( conducting shaft T.B.F. 3) show the strongest
intensity, of up to 25 degrees Fraser, that are associated with the weak magnetic anomalies,
next to 100 gammas. The conducting zones 1 and 2 should possibly to indices of pyrite
present in the intrusive rock and associated with the defect zones. Conducting Zone 3 This
zone is located between the lines LB 0+00 and 3+50S between 6+00 and 10+00W,
continuing an direction NE-SO. The zone reaches 20 and 25 degrees of intensity and it is
represented by the conducting shafts T.B.F. 4 and 5 (Map E-3). In some places (L12+00S
and 3+50S between 6+00W - 9+00W) the zone shows direct magnetic associations of 200 to
400 gammas that they are represented by the shafts of the magnetic bodies 5 and 6 (Map E1). it should be to note that the anomalies T.B.F and magnetic are not extended until the line
4+50S. Conducting Zone 4 This mean intensity zone (10 to 15 degrees Fraser) is located
between the lines 3+50S and 4+50S in the level 6+00W. The zone seems be associated with
magnetic bodies shaft # 7 (Map E-1), with intensity of 200 to 300 gammas but of limited
extension. A lava mafic or a failed zone and mineralized in pyrite can be the origin of this
zone, whose West flank is adjacent to a magnetic intensity zone very irregular (L 4+50S
between 6+00W and 8+00W) that suggests the presence of a failed zone. Conducting Zone
5 East zone is limited by the lines LB 0+00 and 4+59S as well as by LR+00 in the This and
LR 4+00W. In some places, the zone reaches strong intensity that be at the point 25 degrees
Fraser and seems be divided in two (2) segments, the first on the line 1+00S (0+50W) and
the other between the lines 3+50S and 4+50S (20 degrees Fraser). This zone is represented
by the conductor # 9 (Map E-3) of clean-looking continuity. However, its site on the line
2+00S (0+75W) is not all right identified. The North segment of the zone does not
correspond to no magnetic anomaly. On the contrary, the South segment is associated to
several magnetic intensity anomalies media to strong, between 200 and 500 gammas, that
they are represented by the magnetic shafts 8, 9 and 10 (Map E-1). This characteristic would
indicate the presence of various lithologics types (volcanic and intrusive dikes). The
anomalies would correspond also this time to pyritized zones inside of these rocks.
Considering what is mentioned previously, the most probable interpretation of the conducting
shaft #9 (Map E-3) would be that it is considered a defect, probably mineralized, that there
can in effect be the prolongation of the structures that affect to the deposit of Nambija to the
other side of the mountain. Within this failed zone is returned to find, on the other hand, the
very prompt presence of skarn and of mineralization in pyrite. Conducting Zone 6 This zone,
of limited extension, sample high intensity that be at the point 30 degrees Fraser between the
lines 3+50S and 4+50S between2+00 and 3+00E and corresponds to the conducting shaft #
10 on the profiles map NAU (Map E-3). It can be observed a direct association with the shaft
of the magnetic body # 12 (Map E-1). This conduct zone seems be located in the South
extremity of a slightly zone NO - SE that corresponded to the magnetic shaft # 12 (Map E-1)
and quiz160s also to the shaft # 11 (Map E-1). it should be not to forget that this zone is
found within shaft of the sinclinal bound structure to the deposit of Nambija. Conducting Zone
7 This zone is located in the extremity East, between the lines 1+50N and 1+00S, and
presents hosiery intensity of 15 degrees Fraser. The zone does not correspond to no
meaningful magnetic anomaly, has a limited extension and it is probably located to the
middle of a intrusive structure. 7. CONCLUSIONS AND RECOMMENDATIONS In how much
concerns to the evaluation of this part of the area of the project in relationship to the
prolongation of the deposit of Nambija, it should be take into account the following: 1) The
geological raisings effected do not reveal the presence of auriferous skarns neither in the
adjacent zone to the deposit of Nambija nor in the explored region, to exception of the skarn
of the Well Ramón where two (2) samples have gold contents moderately high. 2)
The interpretation of the geochemical information does not demonstrate no meaningful
association between mineralization in gold and mineralization of metal gold in the skarns
investigated, what hinders the election of appropriate geophysical methods. The projects
effected in the area of the project have permitted to detect seven (7) conducting zones. Most
of them demonstrates a good association with the magnetic anomalies. The structural
conclusions or lithostratigraphyc relevant to each one of the zones are found in the par. 5.3
and 6.3 respectively. In light of the mentioned reasons previously, two (2) zones of limited
importance could be taken in consideration for the contingent confirmation of the projects.
These are: 1) The conducting zone # 5 (Map E-4) defined by the conducting shaft T.B.F. #
9(Map E-3), in particular its segment between the lines LB 0+00 and L 2+00S, I would be
investigated insofar as the possibility of finding isolated zones of skarn as well as to
understand better the structural elements within this zone. Methods of resistive such as the
provoked polarization or the provoked spectral polarization could be used. In the event of
requiring in-depth investigation, they could be taken in methods consideration magneto telluric (AMT, CSAMT). It is pointed out that the zones is decreased resistive would not have
to be the most interesting, since they could correspond to zones of mineralization in pyrite
(defects). These zones, yet if present anomalous values in gold, they are not probably
interesting from the economic point of view. The investigation and the adequate
interpretation of the rocks of high resistive could also be hindered by the rocks presence with
similar geophysical standards (intrusive, piroclastic, etc). 2) The zone of skarn located
between the well Ramón and the road Guaysimi would be explored more in detail.
They could be discovered thus the rich zone mineralized in isolated gold. The task probably
would be facilitated by the meaningful mineralization in zinc that seems be associated with
this skarn. The population provoked in configuration dipolo-dipolo seems be the most
appropriate method. OBSERVATIONS RELATED TO THE CONTINUATION OF THE
PROJECTS TO THE SOUTH OF THE BANKRUPT OF THE FIERRO 1) Lineament spaced
each 100 m as maximum. 2) Magnetic Raising ( total field and gradient), not to identify the
possible extension of the deposit but rather to delimit the extension of the litológicas
units. 3) Measure of the magnetic susceptibility directly on the rock samples in order to
facilitating the interpretation of the raisings magnetometrics. 4) Location of the structural
lineaments (defects with pyrite) with the help of the method EM-VLF. DOWNLOAD