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Geology, alteration, and mineralization of the Cerro Corona porphyry copper-gold deposit, Cajamarca Province, Peru James, John
Abstract
The Cerro Corona deposit is located in the Hualgayoc mining district of the Cajamarca province of northern Peru. The copper-gold mineralization is hosted by the Cerro Corona stock which is divided into two intrusive units: a pre or synmineralization phase (Quartz Diorite 1) and post-mineralization phase (Quartz Diorite 2). Intrusive phases are compositionally very similar and have fine grain crowded porphyritic textures. The quartz diorite is comprised of approximately 25 % plagioclase, 8 % biotite and 8 % hornblende phenocrysts and the remainder is a fine grained groundmass. ²°⁶Pb/²³⁸U analysis of zircon gives a Middle Miocene age (14.4 ±0.1 Ma) for the Cerro Corona quartz diorite. The Cerro Corona stock intruded the late Cretaceous Pariatambo formation which is composed of silty limestones. Skarning and mineralization of the Pariatambo formation is restricted to within twenty meters of the limestone diorite contact. Four hydrothermal alteration assemblages have been classified at the Cerro Corona deposit: 1) K-silicate, 2) Sericite-chlorite-clay (SCC), 3) Quartz-sericite-pyrite (QSP), 4) Orange clay (OC). K-silicate alteration is characterized by replacement of primary hornblende by hydrothermal biotite, replacement of plagioclase by potassium feldspar and the formation of potassium feldspar and leafy hydrothermal biotite in the groundmass and in veins. K-silicate alteration is interpreted to be the oldest alteration assemblage and it occurs commonly in the deeper levels of the Cerro Corona stock. SCC alteration is characterized by pale green colour and waxy texture due to the replacement of plagioclase and groundmass by sericite, chlorite, clay, and calcite. SCC alteration comprises a large area in Quartz Diorite 1 and is interpreted to have the occurred after K-silicate alteration. QSP alteration is characterized by the destruction of intrusive texture and the formation of massive quartz, sericite and pyrite. QSP alteration occurs in the upper levels of the stock in Quartz Diorite 1 and is interpreted to be the last stage in the hydrothermal sequence which is associated with mineralization. OC alteration is characterized by the replacement of plagioclase and groundmass by clay which is bright orange in colour where the alteration affects magnetite-hematite bearing rocks. OC alteration occurs throughout the Cerro Corona stock and may be related to supergene fluids. The main vein types classified at Cerro Corona are: 1) Biotite 2) K-feldspar 3) Magnetite 4) Quartz-oxide-sulphide (QOS) 5) Quartz-pyrite (QP) 6) Pyrite 7) Calcite. The majority of the copper mineralization occurs as chalcopyrite which forms in the Kfeldspar, Magnetite, QOS, QP and Pyrite veins. Two types of supergene mineralization occur at Cerro Corona: oxidized Au bearing rock and supergene Cu mineralized rock both of which occur in zones sub-parallel to the surface. Significant hypogene mineralization occurs throughout Quartz Diorite 1 above 3500m. Mineralization is interpreted to have occurred in two separate phases: 1) low Au/Cu ratio mineralization which occurs throughout Quartz Diorite 1 and is related to K-silicate alteration; and 2) high Au/Cu ratio mineralization which occurs in the center of the SCC altered zone and may be related to SCC alteration. The size, grade and mineralogy of the Cerro Corona deposit are characteristic of porphyry copper-gold deposits which occur throughout the world. The alteration and mineralization at Cerro Corona represents a magmatic-hydrothermal system which chemically changed and collapsed over time resulting in intense overprinting alteration assemblages and related mineralization.
Item Metadata
Title |
Geology, alteration, and mineralization of the Cerro Corona porphyry copper-gold deposit, Cajamarca Province, Peru
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1998
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Description |
The Cerro Corona deposit is located in the Hualgayoc mining district of the
Cajamarca province of northern Peru. The copper-gold mineralization is hosted by the
Cerro Corona stock which is divided into two intrusive units: a pre or synmineralization
phase (Quartz Diorite 1) and post-mineralization phase (Quartz Diorite 2). Intrusive
phases are compositionally very similar and have fine grain crowded porphyritic textures.
The quartz diorite is comprised of approximately 25 % plagioclase, 8 % biotite and 8 %
hornblende phenocrysts and the remainder is a fine grained groundmass. ²°⁶Pb/²³⁸U
analysis of zircon gives a Middle Miocene age (14.4 ±0.1 Ma) for the Cerro Corona
quartz diorite. The Cerro Corona stock intruded the late Cretaceous Pariatambo
formation which is composed of silty limestones. Skarning and mineralization of the
Pariatambo formation is restricted to within twenty meters of the limestone diorite
contact.
Four hydrothermal alteration assemblages have been classified at the Cerro Corona
deposit: 1) K-silicate, 2) Sericite-chlorite-clay (SCC), 3) Quartz-sericite-pyrite (QSP), 4)
Orange clay (OC). K-silicate alteration is characterized by replacement of primary
hornblende by hydrothermal biotite, replacement of plagioclase by potassium feldspar and
the formation of potassium feldspar and leafy hydrothermal biotite in the groundmass and
in veins. K-silicate alteration is interpreted to be the oldest alteration assemblage and it
occurs commonly in the deeper levels of the Cerro Corona stock. SCC alteration is
characterized by pale green colour and waxy texture due to the replacement of plagioclase
and groundmass by sericite, chlorite, clay, and calcite. SCC alteration comprises a large
area in Quartz Diorite 1 and is interpreted to have the occurred after K-silicate alteration.
QSP alteration is characterized by the destruction of intrusive texture and the formation of
massive quartz, sericite and pyrite. QSP alteration occurs in the upper levels of the stock
in Quartz Diorite 1 and is interpreted to be the last stage in the hydrothermal sequence
which is associated with mineralization. OC alteration is characterized by the replacement
of plagioclase and groundmass by clay which is bright orange in colour where the alteration affects magnetite-hematite bearing rocks. OC alteration occurs throughout the
Cerro Corona stock and may be related to supergene fluids.
The main vein types classified at Cerro Corona are: 1) Biotite 2) K-feldspar 3)
Magnetite 4) Quartz-oxide-sulphide (QOS) 5) Quartz-pyrite (QP) 6) Pyrite 7) Calcite.
The majority of the copper mineralization occurs as chalcopyrite which forms in the Kfeldspar,
Magnetite, QOS, QP and Pyrite veins.
Two types of supergene mineralization occur at Cerro Corona: oxidized Au
bearing rock and supergene Cu mineralized rock both of which occur in zones sub-parallel
to the surface. Significant hypogene mineralization occurs throughout Quartz Diorite 1
above 3500m. Mineralization is interpreted to have occurred in two separate phases: 1)
low Au/Cu ratio mineralization which occurs throughout Quartz Diorite 1 and is related to
K-silicate alteration; and 2) high Au/Cu ratio mineralization which occurs in the center of
the SCC altered zone and may be related to SCC alteration.
The size, grade and mineralogy of the Cerro Corona deposit are characteristic of
porphyry copper-gold deposits which occur throughout the world. The alteration and
mineralization at Cerro Corona represents a magmatic-hydrothermal system which
chemically changed and collapsed over time resulting in intense overprinting alteration
assemblages and related mineralization.
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Extent |
42184603 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-04-30
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0053185
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1998-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
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Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.