Sulfur Isotope Studies in the Zinc-Lead Mine San Vicente, Central Peru

Gorzawski, Hendrik; Fontboté, Lluı́s; Field, Cyrus W.; Tejada, R.

doi:10.1007/978-3-642-88282-1_22

Cited by 8 publications

(3 citation statements)

References 12 publications

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“…The Pucará Group is host to a range of MVT Zn-Pb deposits (Reid 2001), with the most important being the San Vicente and Shalipayco deposits Gorzawski et al 1990;Moritz et al 1996;Spangenberg et al 1996Spangenberg et al , 1999. In addition, the porphyry-related epithermal polymetallic (BCordilleran^) deposits of Cerro de Pasco (Baumgartner and Fontboté 2008;Baumgartner et al 2009;Rottier et al 2016), San Gregorio in the Colquijirca district (Bendezú and Fontboté 2009) and the mines located in the Yauli Dome (e.g., San Cristobal, Carahuacra and Morococha; Beuchat et al 2004;Catchpole et al 2015) are also hosted by the Pucará Group.…”

Section: Regional Geological Setting and Mineralizationmentioning

confidence: 99%

Germanium enrichment in supergene settings: evidence from the Cristal nonsulfide Zn prospect, Bongará district, northern Peru

et al. 2018

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Supergene nonsulfide ores form from the weathering of sulfide mineralization. Given the geochemical affinity of Ge to Si 4+ and Fe 3+ , weathering of Ge-bearing sulfides could potentially lead to Ge enrichments in silicate and Fe-oxy-hydroxide minerals, although bulk rock Ge concentrations in supergene nonsulfide deposits are rarely reported. Here, we present the results of an investigation into Ge concentrations and deportment in the Cristal supergene Zn nonsulfide prospect (Bongará, northern Peru), which formed from the weathering of a preexisting Mississippi Valley-type (MVT) sulfide deposit. Material examined in this study originates from drillcore recovered from oxidized Zn-rich bodies~15-20 m thick, containing~5-45 wt% Zn and Ge concentrations~100 ppm. Microanalysis and laser ablation-ICP-MS show that precursor sphalerite is rich in both Fe (mean Fe = 8.19 wt%) and Ge (mean Ge = 142 ppm). Using the mineral geothermometer GGIMFis-geothermometer for Ga, Ge, In, Mn, and Fe in sphalerite-proposed by Frenzel et al. (Ore Geol Rev 76:52-78, 2016), sphalerite trace element data from the Cristal prospect suggest a possible formation temperature (T GGIMFis ) of 225 ± 50°C, anomalously high for a MVT deposit. Germanium concentrations measured in both goethite (mean values 100 to 229 ppm, max 511 ppm) and hemimorphite (mean values 39 to 137 ppm, max 258 ppm) are similar to concentrations measured in hypogene sphalerite. Additionally, the Ge concentrations recorded in bulk rock analyses of sphalerite-bearing and oxidized samples are also similar. A persistent warm-humid climate is interpreted for the region, resulting in the development of an oxidation zone favoring the formation of abundant Zn hydrosilicates and Fe hydroxides, both able to incorporate Ge in their crystal structure. In this scenario, Ge has been prevented from dispersion during the weathering of the Ge-bearing sulfide bodies and remains in the resultant nonsulfide ore.

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Section: Regional Geological Setting and Mineralizationmentioning

confidence: 99%

Germanium enrichment in supergene settings: evidence from the Cristal nonsulfide Zn prospect, Bongará district, northern Peru

et al. 2018

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“…Analytical methods: Analyses reported in this study are discussed in Gorzawski et al (1990) and are carried out on 20 individual sulfide concentrates that were extracted from five samples. The sulfide sulfur in each concentrate was converted to SO2 gas for mass spectrametric analysis of the sulfur isotope ratio according to the method described by Ohmoto and Rye (1979).…”

Section: Sulfur Isotopesmentioning

confidence: 99%

“…The isotopically heavy and uniform •4S values of the sphalerites are inconsistent with a biogenic mechanism for the reduction of sulfate in place. Also the generation of H2S by thermal degradation of organic sulfur-bearing hydrocarbons is not considered to produce reduced sulfur with the required sulfur isotope composition for the fixation of metals at San Vicente (Gorzawski et al, 1990).…”

Section: Sulfur Isotopesmentioning

confidence: 99%

Genesis of the mississippi valley-type Zn-Pb deposit of San Vicente, central Peru; geologic and isotopic (Sr, O, C, S, Pb) evidence

Fontboté¹,

Gorzawski²

1990

Economic Geology

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The San Vicente Zn-Pb ore deposit is situated 300 km east of Lima in central Peru, within the Upper Triassic-Lower Jurassic carbonate platform (Pucarft Group) at the western margin of the Brazilian Shield. Production during the last 20 years and present reserves exceed 12 million tons of ore assaying about 12 percent Zn and 1 percent Pb. Sphalerite and galena, the only ore minerals, occur as lens-shaped bodies generally parallel to the bedding. Within the 1,400-m-thick Pucarfi sequence three ore-bearing dolomite units occur. The ore lenses are bound to dolomitized tidal fiat and lagoon facies with cryptalgal lamination and evaporite molds and to adjacent oolithic grainstones of barrier facies. Strontium, carbon, oxygen, and sulfur isotope geochemistry was carried out on consecutive crystallization generations. The results obtained display systematic trends. The 87Sr/S6Sr ratios range between 0.7077 and 0.7084. The first generations display values very similar to those of Upper Triassic-Lower Jurassic ocean water. Later generations are slightly enriched in radiogenic strontium. The degree of enrichment in radiogenic strontium is low compared to other Mississippi Valley-type deposits. The b180 values range between-6 and-10 per mil PDB, and the b•3C values between +2 and-1 per mil PDB. The late crystallization generations are enriched in the light isotopes of oxygen and carbon compared to the first generations. The sulfur isotope ratios of sphalerite are relatively homogeneous, ranging between 9.9 and 13.0 per mil. A trend to lighter sulfur isotope ratios with advancing diagenetic stage can also be recognized. The San Vicente lead-zinc deposit formed during burial diagenesis. The temperatures indicated by sulfur isotope geothermometry (75ø-92øC) would be consistent with temperatures reached at a burial depth of about 2 to 3 kin. This might have been reached by the end of the Jurassic. A model based on abiogenic reduction of sulfates at or near the ore site, and the introduction of a zinc-and lead-bearing basinal brine characterized by strontium isotope ratios slightly higher than contemporaneous seawater and highly radiogenic lead, is favored. The association of the orebodies with peritidal facies with abundant sulfate molds is important evidence favoring the existence of two separate reservoirs for sulfur and metals. Leaching of detrital material derived from Precambrian upper crust from the Brazilian Shield would explain both strontium and lead isotope ratios.

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Stratabound Ore Deposits in the Pucará Basin

Fontboté

1990

Stratabound Ore Deposits in the Andes

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Sulfur Isotope Studies in the Zinc-Lead Mine San Vicente, Central Peru

Cited by 8 publications

References 12 publications

Germanium enrichment in supergene settings: evidence from the Cristal nonsulfide Zn prospect, Bongará district, northern Peru

Germanium enrichment in supergene settings: evidence from the Cristal nonsulfide Zn prospect, Bongará district, northern Peru

Genesis of the mississippi valley-type Zn-Pb deposit of San Vicente, central Peru; geologic and isotopic (Sr, O, C, S, Pb) evidence

Stratabound Ore Deposits in the Pucará Basin

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