Characteristics of Copper Mineralization and Age of Intrusive Rocks

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Characteristics of Copper
Mineralization and Age of Intrusive
Rocks, Tapaya Prospect, Northern
Luzon, Philippines
Akira IMAI1,2, Asuka MITANI1, Ryohei
y
TAKAHASHI1,2, Takahiro TANAKA1,
Koichiro WATANABE1, and Anders SCHERSTEN3
1
Geologic Background
Luzon is being subducted
westward by Philippine Sea Plate
in the east at East Luzon Trench
and eastward by Eurasia Plate
(South China Sea) in the west at
Manila Trench
Arc magmatism and fractures
are associated with epithermal
Au and porphyry Cu deposits
Department of Earth Resources Engineering, Faculty of Engineering, Kyushu
University, Fukuoka 819-0395, Japan
2
Department of Earth Science and Technology, Faculty of Engineering and Resource
Science, Akita University, Akita 010-8502, Japan
3
Department of Earth and Ecosystem Sciences Division of Geology, Lund University,
Solvegatan 12, S-223 62 Lund, Sweden
Objectives
Geologic Background
(Baguio mineral district)
Location：
Southern Baguio district
1. Characteristics of intrusive rocks associated with
mineralization
Area：
approx. 3×2 km
Status
being explored by Philex Mining Corp
Philex Mining Corp．
2. Age determination of intrusive rocks associated with
mineralization
3. Characteristics of mineralization (style, ore
mineralogy, formation condition,etc)
porphyry Cu deposit
epithermal Au deposit Santo Tomas II deposit
Tapaya prospect
Geology
Rock Description
Quartz Diorite (Agno)
○ field observation：
outcrops
drill cores (TAP1,TAP6)
Brecciated MetaAndesite intruded
by Dacite Porphyry
(Middle Miocene)
Dacite Porphyry
←PHILEX MINING CORP., Unpublished
Rock Description
Dacitic Volcanic Rocks
→ 40Ar-39Ar dating on
hornblende yielded
12.7±0.5 Ma
Dacite Porphyry
Characteristics of intrusive rocks associated with
mineralization
hbl
hbl
ap
pl
Magnetic
Susceptibility
Rock type
(×10-3 SI unit)
Dacite Porphyry
Dacite Porphyry
Dacite Porphyry
Dacite Porphyry
→Classified as Magnetite-series
40Ar/39Ar
Whole-rock composition
18.8～21.2
18.1～21.8
24.5～27.3
42.9～44.0
qtz
opq
qtz, quartz; pl, plagioclase; hbl, hornblende; bt, biotite; ap, apatite; opq, opaque mineral Age of Dacite Porphyry Associated with Mineralization
13.4±0.8 Ma,14.6±0.3 Ma (Middle Miocene)
Method：
X-ray fluorescence
spectroscopy
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● classified to low-K to
medium-K series
adakite
● adakitic in Sr/Y-Y diagram
typical arc
K2O ‐ SiO2 diagram： Le Maitre et al. (1989)
Sr/Y ‐ Y diagramDefant and Drummond (1990) and Defant et al. (1991)
Mineralization Characteristics
Young Formation Ages of Ore
Deposits in the Southern
Baguio Mineral District
Mineralization at Tapaya
Prospect Associated with
Middle Miocene Intrusion
Methods：Ore Microscopy
X‐ray Diffractometry
SEM‐EDX
Fluid Inclusion Microthermometry
Porphyry Cu:
•Santo Tomas II 1.5 Ma
•Black Mountain 2.1 Ma
(Whole rock K-Ar age:
Imai, 2001, 2002)
Kelly
Further Potential of Ore
Deposits in Baguio
Mineral District
Associated with Middle
Miocene Intrusive Rocks
in Addition to those with
Plio-Pleistocene
Magmatism
Epithermal Au:
•Kelly 1.4-0.9 Ma
(K-Ar age on alunite :
Aoki et al., 1993)
•Acupan 0.65±0.07 Ma
(K-Ar age on sericite :
Aoki et al., 1993)
Acupan
Black Mountain
Santo Tomas II
２ Types/Stages of Mineralization
●Early PorphyryPorphyry-type
overprinted by
●Late Epithermal Vein
Vein--type
Early Porphyry-type Mineralization Overprinted by Late
Epithermal-type Mineralization
TAP6
Early Porphyry-type Mineralization
Location： TAP 6-416m, 650-660m
Mode of Occurrence： Veinlets of Chlorite-Magnetite, Biotite Alteration
cut by epithermal quartz veinlet
Ore Minerals： Chalcopyrite, Magnetite, Bornite, Hematite, Molybdenite
ccp, chalcopyrite; mag, magnetite; bn, bornite;
hem, hematite; mo, molybdenite
Porphyry-type Veinlet (Magnetite-Chalcopyrite)
Late Epithermal-type Quartz Vein
PHILEX MINING CORP., Unpublished →
TAP6 TAP1
Late Mineralization
Late Mineralization
S, Bi, Pb
aikinite-like mineral
Pb: Bi: S = 0.9: 1.04: 1.06
1. Quartz Vein
Locality： Widely Distributed (High Grade Cu Ore at TAP1－300m）
Ore Minerals： Chalcopyrite, Pyrite, Bornite, Digenite-like Mineral,
Sphalerite, Emplectite, Aikinite-like Minerals, Unknown Minerals
S, Bi, Pb
unknown １：
Cu-Pb-Bi-S-Se system
Cu
Se
Cu
S, Bi, Pb
ccp, chalcopyrite; py, pyrite; bn, bornite; Sph, sphalerite; clc, digenite‐like; qtz, quartz
Cu
Se
ccp, chalcopyrite; emp, emplectite; aik, ikinite‐like mineral; qtz, quartz;
ui 1, unknown １; ui2, unkown ２
TAP1
Late Mineralization
3. Calcite-Epidote Vein
Locality：at TAP1-342m
Ore Minerals： Chalcopyrite, Pyrite,
Bornite, Sphalerite, Digenite-like
Locality： at TAP 6-116m
Opaque Minerals： Pyrite,
Magnetite, Rutile, Chalcopyrite
Intensit
y
2θ(°)
Fe
Cu
SEM-EDX spectrum
TAP6
Late Mineralization
2. Sericite-Quartz Vein
ccp, chalcopyrite; py, pyrite bn, bornite; Sph, sphalerite; dg, digenite‐like mineral
unknown ２：
Cu-Fe-Pb-Bi-S-Se system
Wall Rock
Opaque Minerals： Chalcopyrite,
Pyrite, Magnetite, Ilmenite
ccp, chalcopyrite; py, pyrite; rt, rutile; ilm, ilmenite;
ttn, titanite
Fluid Inclusions in Late Vein Quartz
Homogenization
Temperature：
Temperature
：180
180--300
TAP6‐416.2m
Fluid Inclusions Microthermometry
TAP1‐302.1m
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TAP1‐306.0m
Boiling：
Mono-phase Vapor Inclusions,
Vapor-rich Inclusions with Variable
Vapor-Liquid Ratio
Not Homogenized upon Heating
250～297
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TAP6‐456.9m
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256～298
183～305
Fluid Inclusions Microthermometry Salinity : 2-9 NaCl eq.wt%
TAP1‐302.1m
Coexistence of Chalcopyrite-Pyrite-Bornite
Sulfidation State
Formation Temperature：250-300
TAP6‐416.2m
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241～302
Estimated Sulfur
Fugacity
approximately 10-7～10-9 bar
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：
High-sulfidation to intermediatesulfidation condition
2.2-3.4 NaCl eq.wt%
TAP1‐306.0m
6.0-9.4 NaCl eq.wt%
TAP6‐456.9m
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3.0-7.3 NaCl eq.wt%
2.8-4.4 NaCl eq.wt%
Summary and Conclusions
＊40Ar‐39Ar age of the dacite porphyry intrusion is dated as
13.5±0.8 Ma, 14.6±0.3 Ma.
(40Ar‐39Ar age of the dacitic volcanic rock is dated as 12.7±0.5 Ma.)
＊Potential exploration targets of ore deposits associated with
Middle Miocene intrusive rocks in southern Baguio mineral district
in addition to those associated with Plio-Pleistocene intrusive rocks
＊Two stages mineralization:
Early porphyry Cu-Mo
Late high-intermediate sulfidation quartz vein Cu-Bi.
Modified from Einaudi et al. (2003)
Remaining - further study
＊To confirm geologic relationships between the intrusive rocks
40Ar‐39Ar age of the dacite porphyry (13.5±0.8 Ma, 14.6±0.3 Ma)
and dacitic volcanic rock (12.7±0.5 Ma) younger than the Agno
quartz diorite (ca.15 Ma)
＊To confirm distribution of and ore-forming condition of early
porphyry Cu
Cu-Mo
Mo mineralization
Rock Description
Intensit
y
skarn-like rock
TAP6 164.8～166.0m
2θ(°)
ep, epidote;
tr, tremolite; cal,
calcite;
an, anorthite PHILEX MINING CORP., Unpublished

Characteristics of Copper Mineralization and Age of Intrusive Rocks

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