The Discovery and Geology of the Kham
Thong Lai Copper-Gold Deposit, Lao, PDR
AIG Geoscientists Symposia
May 27th-29th 2013, Bali, Indonesia
Paul Merriner
Presentation Overview
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Prospect Location & Regional Setting
Exploration Targeting
Drilling
Geology
Alteration
Mineralisation
Structure
Location and Regional Setting
Xiengkhouang
Province
Phu Bia Contract
Area
(2600km2)
Phonsavan
Capital
KTL Cu-Au
Deposit
 The Phu Bia contract area (MEPA) is located in the north
central part of Lao, PDR and lies at the confluence of the
prospective Loei (LFB) and Truong Son fold belts (TFB).
 LFB and TFB are associated with widespread plutonism
and volcanic activity and strong compressive forces which
have moved prospective rocks to near surface.
 Mineral deposit discoveries made in the fold belts include
Phu Kham Cu-Au, Sepon Cu-Au, Chatree Au-Ag and Ban
Houayxai Au-Ag.
 Kham Thong Lai (KTL) Cu-Au deposit is in the northern part of
the PBM MEPA, approx. 8 km east of the Xiengkhouang
Province capital Phonsavan. The deposit lies on the broad
Xiengkhouang Plateau at the northern end of the Annamese
Cordillera.
Location and Regional Setting
Exploration – Geochemistry

During 1994-1996 Normandy Anglo Asian
completed regional BLEG stream sediment
sampling which returned broad Au and Cu
BLEG anomalies over KTL which led to its
rediscovery.

Normandy Anglo followed-up the BLEG
results with detailed geological mapping and
a gridded soil auger program, the results
from which defined a 2.6 km long Cu and Au
in soil geochemical anomaly.

In 2008 PBM extended the Normandy Anglo
soil grid to the north, south and west of the
target and also completed infill sampling from
100m x 200m to 100m x 100m. Anomalous
results extended the KTL Cu-Au geochemical
anomaly a further 1km to the west.
Coincident anomalous molybdenum in soil
was also identified.

Best Cu–Au mineralisation at KTL deposit
occurs beneath the strongest Cu-Au-Mo
soil anomalies.
Exploration - Geophysics

During 1994-1996 Normandy Anglo completed dipoledipole IP survey, ground and airborne magnetic survey
over the KTL target area.
• IP Chargeability zone identified
• Magnetic high identified over the KTL

During 2008 PBM completed gradient array, 3D IP and
ground magnetics over the KTL area.
• 3D IP survey identified two strong
chargeability zones located immediately
north and south of the mineralisation zone.
Magnetic ground survey identified anomalous
magnetic high zones (magnetite and
pyrrhotite skarns) directly over the KTL
deposit .

In 2008 a tenement wide helimagnetic and radiometric
survey Magnetic data over KTL produced a similar
result to the previous survey. Closer spaced flight lines
did improve the definition of the KTL magnetic
response.
•
Best geophysical targets at KTL are coincident
magnetic high- mod IP chargeability zones.
Exploration - Geophysics
Exploration and Resource Drilling
2005-2006
PhaseAnglo
2
Program
– 23
drill
holes
for
1994-1996
2010-2012
Normandy
4
Drill Program
96
(diamond)
– 31 drill
drill
holes
holes
forfor
3248m.
29,931.6m.
Program
Program
2012-2013
2009-2010 PBM
5
3 DrillScout
106
47 (diamond/RC)
(diamond)
drill
holes
for
20,050.5m.
9584.3m.
Program
3157m.Program
designed
to
test
previous
Normandy
Anglo
targets
and
continuity
designed
to
test strike
coincident
and
down-dip
anomalous
continuity
and
Au
of
significant
inMo
soil,
mineralisation
IPtest
fromhigh
Program
to infill
anomalous
at 50m
x Cu
50m
Cu,
Au
spacing
and
over
is dipole-dipole
soil
selected
and
IPparts
chargeability
of defined
the
deposit
and
to
Totaldesigned
drilling
to drill
date
323
drill
holes
for
70,100
metres
of
significant
mineralisation
intersected
in high.
the
scout
program.
chargeability
previous
drilling
high
and
and
to
airborne
upgrade
magnetic
the
resource
category.
increase
magnetic
confidence
response
from
and
the
upgrade
geochemical
the
KTL
and
resource
geophysical
category.
surveys completed in 2008.
Geology

KTL geology consists of an E-W trending, moderate
south dipping, weak to moderately foliated volcanosedimentary package of Late Carboniferous–EarlyPermian age containing alternating sequences of
deformed siliclastics, calcareous sediments and
volcaniclastics (co-genetic with intrusives).

Volcano-sedimentary sequence intruded by rift
associated multi-phase intrusive complex
containing:
• Low-K calc-alkali diorite/tonalite granitoid
stocks
• Late quartz-feldspar rhyodacite porphyry
dykes
• Late basaltic to basaltic andesitic intrusives

Skarn is common throughout KTL. Mainly occurs
as exoskarn. Prograde skarns - calc-silicate
(garnet/epidote/pyroxene) and magnetite.
Retrograde skarns - actinolite, chlorite, sulphide.
Form at granitoid and porphyry intrusive contacts
with limestone and calcareous sediments.

Redbeds (ferruginous arenite) lies unconformably
over sediment package and intrusives.
KTL Geology Block Model
Alteration
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The KTL deposit is host to complex hydrothermal and
metasomatic hydrothermal alteration patterns with strong
lithological and structural control.
Propylitic –widespread throughout the KTL deposit. Common
alteration style in stocks. Contains epidote, chlorite, albite,
actinolite, carbonate, pyrite, silica, pyrrhotite, hematite.
Phyllic – common throughout deposit. Weak to strong sericite,
silica, pyrite, carbonate, chlorite, albite. Common in dioritetonalite intrusive and feldspar-quartz porphyries and nearby
sediments and volcanics.
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Magnetite skarn - magnetite, pyrrhotite, pyrite, chalcopyrite.
Mainly forms as exoskarn at limestone/intrusive contacts.

High-T calc-silicate skarns - prograde? Mainly forms as
exoskarn, garnet skarn (grossular-andradite) or clinopyroxene
skarn (diopside-hedenbergite), ±magnetite.

Low-T retrograde skarns – formed during thermal collapse,
form as exoskarn, commonly overprint calc-silicate and
magnetite skarn. Assemblage contains actinolite, calcite, quartz,
sulphide (pyrrhotite, chalcopyrite, pyrite, sphalerite), chlorite,
prehnite.
Pyrrhotite-magnetite-chlorite-pyrite-chalcopyrite skarn
containing 1.5% Cu, 1.75g/t Au.
Qtz-carb-sulfide-gold veined, high-intensity sericite-qtzsulfide alt quartz-feldspar porphyry
Foliated high-intensity sericite-chlorite-quartz-calcitesulfide (intermediate phyllic) altered porphyry
Mineralisation

The KTL deposit is a stratabound porphyry-skarn style
copper gold system which is host to:
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Quartz-dominant stockworks and sheeted quartzsulphide veins.
Sulphide disseminated mineralisation
Fractured-controlled sulphide veining in volcanosedimentary wall rocks.
Skarn mineralisation. High-T and Low-T type.
Supergene mineralisation

Mineralisation is considered to be coeval with stock
emplacement. Re-Os age dating from vein hosted
molybdenite returned an age of 289.4 ± 1.0 Ma (Early
Permian). Partial remobilisation of the Early Permian KTL
mineral system during thrust related shearing – possibly
related to the Indosinian accretion event.
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Main Sulphide Minerals: pyrite, chalcopyrite and
pyrrhotite with less common molybdenite, bornite,
sphalerite and galena.
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Main Gangue Minerals: quartz, carbonate, pyrite,
magnetite, pyrrhotite, albite, plagioclase, epidote,
sericite, chlorite, garnet, actinolite.
Mineralisation
Structure

The regional structure in the Phonsavan area is dominated by south verging fold-thrust belt of
probable Late Permo-Mid Triassic age related to accretionary tectonics during the Indosinian.

Evidence of the fold-thrust system is observed at KTL as fold-thrust related shear and foliation
fabrics. Most parts of the KTL deposit show some degree of deformation ranging from weak to
pervasive. Phyllic altered zones typically show more intense and pervasive deformation than the
outer propylitic zones. Main thrust planes are easy to identify but difficult to measure in core.

Foliation measurements from outcrop and drill core show a consistent E-W strike and south dip
orientation - which is parallel with regional thrust structures. Similarly bedding shows a general E-W
strike and dips moderately to the south.

Vein measurement data from drill core indicates multiple vein sets occur at KTL which are associated
with the main fold-thrust event and late NW and NE orientated faults.
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Late NW and NE faults at KTL formed post mineralisation and are responsible for brittle deformation
throughout the deposit. 3D modeling interpreted from the current drilling and assay indicates that
displacement and/or truncation of the KTL ore deposit is minor except in the central part of the
deposit where a late NW dextral strike-slip appears to have displaced the deposit by approximately
200m.
Structure
CLEAVAGE
BEDDING
Phu Bia Mining
Thank You