Regional geology and major ore deposits of central Peru

Petersen, Uwe

doi:10.2113/gsecongeo.60.3.407

Cited by 77 publications

(59 citation statements)

References 6 publications

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“…tennantite, enargite, and Fe-poor sphalerite. At Morococha (Petersen, 1965;K. Kouzmanov et al, 2006, unpub. report for Pan American Silver Corp.), the mineralogy of the Italia manto consists of pyrrhotite, magnetite, sphalerite, and galena, and a later stage of mineralization consists of enargite, and/or tennantite, and Fe-poor sphalerite.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, prior to 1950, 1200 million ounces (Moz) Ag, 2 Moz of Au, and about 50 Mt at 2 wt percent Cu were mined (our estimate based on data of Jiménez, 1924; Geological staff of Cerro de Pasco Corporation, 1950;Einaudi, 1977;Fischer, 1977;Baumgartner, 2007). Contributions on the geology and mineralization at Cerro de Pasco include McLaughlin (1924), Bowditch (1935), Graton and Bowditch, (1936), Lacy (1949), Geological staff of Cerro de Pasco Corporation (1950), Jenks (1951), Ward (1961), Petersen (1965), Einaudi (1968Einaudi ( , 1977, Silberman and Noble (1977), Mégard (1978), Rivera (1997), Angeles (1999), Baumgartner et al (2003), and Baumgartner (2007). Several unpublished reports of Cerro de Pasco Corporation, CENTRO-MIN, and Volcán Compañía Minera S.A contain additional information on Cerro de Pasco.…”

Section: Introductionmentioning

confidence: 99%

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Mineral Zoning and Geochemistry of Epithermal Polymetallic Zn-Pb-Ag-Cu-Bi Mineralization at Cerro de Pasco, Peru

Baumgartner¹,

Fontboté²,

Vennemann³

2008

Economic Geology

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The large Cerro de Pasco Cordilleran base metal deposit in central Peru is located on the eastern margin of a middle Miocene diatreme-dome complex and comprises two mineralization stages. The first stage consists of a large pyrite-quartz body replacing Lower Mesozoic Pucará carbonate rocks and, to a lesser extent, diatreme breccia. This body is composed of pyrite with pyrrhotite inclusions, quartz, and black and red chalcedony (containing hypogene hematite). At the contact with the pyrite-quartz body, the diatreme breccia is altered to pyrite-quartz-sericite-pyrite. This body was, in part, replaced by pipelike pyrrhotite bodies zoned outward to carbonate-replacement Zn-Pb ores bearing Fe-rich sphalerite (up to 24 mol % FeS).The second mineralization stage is partly superimposed on the first and consists of zoned east-west-trending Cu-Ag-(Au-Zn-Pb) enargite-pyrite veins hosted in the diatreme breccia in the western part of the deposit and well-zoned Zn-Pb-(Bi-Ag-Cu) carbonate-replacement orebodies; in both cases, sphalerite is Fe poor and the inner parts of the orebodies show typically advanced argillic alteration assemblages, including aluminum phosphate sulfate (APS) minerals. The zoned enargite-pyrite veins display mineral zoning, from a core of enargite-pyrite ± alunite with traces of Au, through an intermediate zone of tennantite, chalcopyrite, and Bi minerals to a poorly developed outer zone bearing sphalerite-galena ± kaolinite. The carbonate-hosted replacement ores are controlled along N35°E, N 90°E, N 120°E, and N 170°E faults. They form well-zoned upward-flaring pipelike orebodies with a core of famatinite-pyrite and alunite, an intermediate zone with tetrahedrite-pyrite, chalcopyrite, matildite, cuprobismutite, emplectite, and other Bi minerals accompanied by APS minerals, kaolinite, and dickite, and an outer zone composed of Fe-poor sphalerite (in the range of 0.05-3.5 mol % FeS) and galena. The outermost zone consists of hematite, magnetite, and Fe-Mn-Zn-Ca-Mg carbonates. Most of the second-stage carbonate-replacement orebodies plunge between 25°and 60°to the west, suggesting that the hydrothermal fluids ascended from deeper levels and that no lateral feeding from the veins to the carbonate-replacement orebodies took place.In the Venencocha and Santa Rosa areas, located 2.5 km northwest of the Cerro de Pasco open pit and in the southern part of the deposit, respectively, advanced argillic altered dacitic domes and oxidized veins with advanced argillic alteration halos occur. The latter veins are possibly the oxidized equivalent of the second-stage enargite-pyrite veins located in the western part of the deposit.The alteration assemblage quartz-muscovite-pyrite associated with the pyrite-quartz body suggests that the first stage precipitated at slightly acidic pH. The sulfide mineral assemblages define an evolutionary path close to the pyrite-pyrrhotite boundary and are characteristic of low-sulfidation states; they suggest that the oxidizing, slightly acidic hydrothermal fluid was buffered by...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mineral Zoning and Geochemistry of Epithermal Polymetallic Zn-Pb-Ag-Cu-Bi Mineralization at Cerro de Pasco, Peru

Baumgartner¹,

Fontboté²,

Vennemann³

2008

Economic Geology

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“…The Shila-Paula district is one of the many areas of low-sulfidation epithermal Au-Ag deposits hosted by the Tertiary subaerial volcanic rocks of the Western Cordillera of southern Peru (Petersen 1965;Sillitoe 1976;Fig. 1).…”

Section: The Metallogenic Provinces Of Southern Perumentioning

confidence: 99%

Internal vein texture and vein evolution of the epithermal Shila-Paula district, southern Peru

et al. 2006

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The epithermal Shila-Paula Au-Ag district is characterized by numerous veins hosted in Tertiary volcanic rocks of the Western Cordillera (southern Peru). Field studies of the ore bodies reveal a systematic association of a main E-W vein with secondary N55-60°W veins-two directions that are also reflected by the orientation of fluid-inclusion planes in quartz crystals of the host rock. In areas where this pattern is not recognized, such as the Apacheta sector, vein emplacement seems to have been guided by regional N40°E and N40°W fractures. Two main vein-filling stages are identified. stage 1 is a quartz-adulariapyrite-galena-sphalerite-chalcopyrite-electrum-Mn silicate-carbonate assemblage that fills the main E-W veins. stage 2, which contains most of the precious-metal mineralization, is divided into pre-bonanza and bonanza substages. The pre-bonanza substage consists of a quartz-adularia-carbonate assemblage that is observed within the secondary N45-60°W veins, in veinlets that cut the stage 1 assemblage, and in final open-space fillings. The two latter structures are finally filled by the bonanza substage characterized by a Fe-poor sphalerite-chalcopyrite-pyrite-galena-tennantite-tetrahedrite-polybasite-pearceite-electrum assemblage. The ore in the main veins is systematically brecciated, whereas the ore in the secondary veins and geodes is characteristic of open-space crystallization. Microthermometric measurements on sphalerite from both stages and on quartz and calcite from stage 2 indicate a salinity range of 0 to 15.5 wt% NaCl equivalent and homogenization temperatures bracketed between 200 and 330°C. Secondary CO 2 -, N 2 -and H 2 S-bearing fluid inclusions are also identified. The age of vein emplacement, based on 40 Ar/ 39Ar ages obtained on adularia of different veins, is estimated at around 11 Ma, with some overlap between adularia of stage 1 (11.4±0.4 Ma) and of stage 2 (10.8±0.3 Ma). A three-phase tectonic model has been constructed to explain the vein formation. Phase 1 corresponds to the assumed development of E-W sinistral shear zones and associated N60°W cleavages under the effects of a NE-SW shortening direction that is recognized at Andean scale. These structures contain the stage 1 ore assemblage that was brecciated during ongoing deformation. Phase 2 is a reactivation of earlier structures under a NW-SE shortening direction that allowed the reopening of the preexisting schistosity and the formation of scarce N50°E-striking S2-cleavage planes filled by the stage 2 pre-bonanza minerals. Phase 3 coincides with the bonanza ore emplacement in the secondary N45-60°W veins and also in open-space in the core of the main E-W veins. Our combined tectonic, textural, mineralogical, fluid-inclusion, and geochronological study presents a complete model of vein formation in which the reactivation of previously formed tectonic structures plays a significant role in ore formation.

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“…1). It contains one of the largest concentrations of massive polymetallic ores within the Miocene metallogenic belt of central and northern Peru (Vidal et al 1997), where numerous other Cordilleran base metal lode and replacement deposits occur (Petersen 1965;Einaudi 1977Einaudi , 1982Einaudi , 1994Guilbert and Park 1986;Bartos 1988). Indeed, from a metallogenetic point of view, the Colquijirca district is part of a larger belt that also comprises the giant ore concentrations of Cerro de Pasco.…”

Section: Geologic Setting and Mineralizationmentioning

confidence: 99%

Relative age of Cordilleran base metal lode and replacement deposits, and high sulfidation Au?(Ag) epithermal mineralization in the Colquijirca mining district, central Peru

Bendezú

Fontboté

Cosca

2003

Mineralium Deposita

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At Colquijirca, central Peru, a predominantly dacitic Miocene diatreme-dome complex of 12.4 to 12.7 Ma ( 40 Ar/ 39 Ar biotite ages), is spatially related to two distinct mineralization types. Disseminated Au-(Ag) associated with advanced argillic alteration and local vuggy silica typical of high-sulfidation epithermal ores are hosted exclusively within the volcanic center at Marcapunta. A second economically more important mineralization type is characterized as ''Cordilleran base metal lode and replacement deposits.'' These ores are hosted in Mesozoic and Cenozoic carbonate rocks surrounding the diatreme-dome complex and are zoned outward from pyrite-enargite-quartz-alunite to pyritechalcopyrite-dickite-kaolinite to pyrite-sphalerite-galena-kaolinite-siderite. Alunite samples related to the Au-(Ag) epithermal ores have been dated by the 40 Ar/ 39 Ar method at 11.3-11.6 Ma and those from the Cordilleran base metal ores in the northern part of the district (Smelter and Colquijirca) at 10.6-10.8 Ma. The significant time gap ($0.5 My) between the ages of the two mineralization types in the Colquijirca district indicates they were formed by different hydrothermal events within the same magmatic cycle. The estimated time interval between the younger mineralization event (base metal mineralization) at $10.6 Ma and the ages of $12.5 Ma obtained on biotites from unmineralized dacitic domes flanking the vicinity of the diatreme vent, suggest a minimum duration of the magmatic-hydrothermal cycle of around 2 Ma. This study on the Colquijirca district offers for the first time precise absolute ages indicating that the Cordilleran base metal lode and replacement deposits were formed by a late hydrothermal event in an intrusive-related district, in this case post Au-(Ag) high-sulfidation epithermal mineralization.

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Regional geology and major ore deposits of central Peru

Cited by 77 publications

References 6 publications

Mineral Zoning and Geochemistry of Epithermal Polymetallic Zn-Pb-Ag-Cu-Bi Mineralization at Cerro de Pasco, Peru

Mineral Zoning and Geochemistry of Epithermal Polymetallic Zn-Pb-Ag-Cu-Bi Mineralization at Cerro de Pasco, Peru

Internal vein texture and vein evolution of the epithermal Shila-Paula district, southern Peru

Relative age of Cordilleran base metal lode and replacement deposits, and high sulfidation Au?(Ag) epithermal mineralization in the Colquijirca mining district, central Peru

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