Summary
The Layo epithermal deposit, cutting Miocene-Pliocene calc-alkaline volcanites of the Tacaza group, includes a well-developed eastern zone (Vetas 7 and 8) in which brecciated and banded textures are associated with a large, intensely argillized zone containing diaspore and alunite. The vetas contain a typical Cu-As mineralogy of the “acid-sulfate” type (pyrite, enargite, Cu-excess tennantite, chalcopyrite, covellite) with an associated original stanniferous paragenesis including vinciennite and mawsonite. The vinciennite is close to the ideal end-member (Cu10Fe4SnAsS16) and the Cu-excess tennantite (Cu11FeAs4S13) shows a total absence of Zn and Ag; its very specific chemical composition suggests that all the iron is Fe3+, equilibrated by Cu+ and probably minor Cu2+.
This particular mineralogical association implies deposition at relatively low temperature (∼300°C) and high aS2 (10−6.5 decreasing to 10−8.5), from a Cu-S-rich and Fe-Zn-poor fluid. The “acid-sulfate” epithermal mineralization of the eastern vetas of Layo appears to have preceded an “adularia-sericite” epithermal mineralization expressed in the western vetas of Layo and also in the nearby large epithermal veins at Orcopampa and Shila. It also supports the genetic relationship that is commonly evoked between porphyry copper and epithermal deposits.
Résumé
Le gîte épithermal de Layo est encaissé dans les volcanites calco-alcalines Miocène-Pliocène du groupe de Tacaza. Sa zone orientale renferme des corps minéralisés (Vetas 7 et 8) bien développés, à textures bréchiques et rubanées associées à une large zone intensément argilisée contenant diaspore et alunite.
Les “vetas” présentent une association minéralogique à As-Cu typique des gisements “acide-sulfate” (pyrite, énargite, tennantite riche en cuivre, chalcopyrite, covellite) et une paragenèse stannifère originale renfermant vinciennite et mawsonite. La vinciennite est proche du pôle théorique (Cu10Fe4SnAsS16) et la tennantite riche en Cu (Cu11FeAs4S13) est dépourvue de Zn et de Ag; sa composition chimique suggère que tout le fer se présente sous la forme Fe3+, en équilibre avec Cu+, avec probablement une participation mineure de Cu2+.
Cette association minéralogique particulière implique une mise en place sous forte fugacité en soufre (aS2 = 10−6.5 décroissant jusqu'à 10−8.5) à une température relativement basse de l'ordre de 300°C à partir d'un fluide riche en Cu et S et pauvre en Fe et Zn. La minéralisation de type “acide-sulfate” des vetas orientales de Layo précéderait celles de type “adulaire-sericite” des vetas occidentales de Layo et des gisements voisins de Orcopampa et Shila. Elle contribue à renforcer le lien fréquemment évoqué entre les porphyres cuprifères et les gisements épithermaux.
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References
Arenas Figueroa MJ (1975) Geologia de la mina Orcopampa y alrededores Arequipa. Bol Soc Geol Peru 46: 9–24
Benavides QA (1990) Exploration and mining ventures in Peru. Econ Geol 85(7): 1296–1302
Blès JL (1989) Contexte structural des minéralisations aurifères épithermales d'Orcopampa, Layo et Shila (département d'Arequipa, Pérou). BRGM Technical Report 89 PER 054 GEO, France, 61pp
Candiotti de los Rios H, Noble DC, McKee EH (1990) Geologic setting and epithermal silver veins of the Arcata district, Southern Peru. Econ Geol 85(7): 1473–1490
Cesbron F, Giraud R, Picot P, Pillard F (1985) La vinciennite, Cu10Fe4Sn(As, Sb)S16, une nouvelle espèce minérale: étude paragénétique du gîte type de Chizeuil. Saône-et-Loire. Bull Minéral 108: 447–456
Charlat M, Lévy C (1974) Substitutions multiples dans la série tennantite-tétraédrite. Bull Soc Fr Minéral Cristallogr 97: 241–250
Charnock T, Garner C, Pattrick R, Vaughan D (1989) EXAFS and M6ssbauer spectroscopic study of Fe-bearing tetrahedrites. Mineral Mag 53: 193–199
Craig JR, Barton PB (1973) Thermochemical approximations for sulfosalts. Econ Geol 68: 493–506
Diakow LJ, Panteleyev A, Schroeter TG (1991) Jurassic epithermal deposits in the Toodoggone river area, Northern British Columbia: examples of well-preserved, volcanic-hosted, precious metal mineralization. Econ Geol 86: 529–554
Einaudi MJ (1977) Environment of ore deposition at Cerro de Pasco, Peru. Econ Geol 72: 893–924
Ericksen GE, Eyzaguirre VR, Urquidi BF, Salas OR (1987) Neogene-Quaternary volcanism and mineralization in the central Andes. U.S. Geol Survey Open-File Report 87-634, Washington, 10pp
Gibson PC, Noble DC, Larson LT (1990) Multistage evolution of the Caldera epithermal Ag-Au vein system, Orcopampa district, Southern Peru: first results. Econ Geol 85(7): 1504–1519
Hayba DO, Bethke PM, Heald P, Foley NK (1985) Geologic, mineralogic and geochemical characteristics of volcanic-hosted epithermal precious-metal deposits. Rev Econ Geol 12: 129–167
Heald P, Foley NK, Hayba DO (1987) Comparative anatomy of volcanic-hosted epithermal deposits: acid-sulfate and adularia-sericite types. Econ Geol 82: 1–26
Johan Z, Le Bel L (1980) Minéralogie des minéralisations type porphyre cuprifère rencontrées dans les batholites de la Caldera et de Colombie britannique. Mém 99, Edit. BRGM, France, pp 141–149
Karup-Möller S, Makovicky E (1974) Skinnerite CU3SbS3, a new sulfosalt from the Ilimaussaq alkaline intrusion, South Greenland. Am Mineral 59: 889–895
Kovalenker VA (1982) Sn-bearing minerals and mineralogical assemblages of a sub-surface gold ore deposit (in russian). Geol Rvdn Mestorojd 1: 31–41
Loucks RR, Petersen U (1988) Polymetallic epithermal fissure vein mineralization, Topia, Durango, Mexico. Part II. Silver mineral chemistry and hight resolution patterns of chemical zoning in veins. Econ Geol 83: 1529–1559
Marcoux E, Milési JP (submitted) Mineralogical and textural position of the Au-Ag bearing-minerals in the evolution of the epithermal deposits of Orcopampa and Shila (Southern Peru). Mineral Petrol
Maske S, Skinner BJ (1972) Studies of the sulfosalts of copper. l. Phases and phase relations in the system Cu-As-S. Econ Geol 66: 901–918
Milèsi JP, Marcoux E, Nehlig P, Sunarya Y, Sukandar, Felenc J (in press) Cirotan, West Java, Indonesia: a 1.7 m.y. hydrid epithermal Au-Ag-Sn-W deposit. Econ Geol
Pauling L, Weinbaum S (1934) The crystal structure of enargite, Cu3AsS4. Z Krist 88: 48–53
Petersen U (1977) An issue devoted to mineral deposits in the South American Cordillera. Introduction. Econ Geol 72: 887–892
Rançon JP (1989) Etude géo-volcanologique des prospects d'or et d'argent épithermaux d'Orcopampa-Layo et Shila (Département d'Arequipa, Sud-Pérou). BRGM Technical Report 89 PER 059 GEO, France, BRGM, 24pp
Schmidt ST, Burkart-Baumann J (1991) The sulphide-sulphosalt paragenesis of the Cu-Pb-Zn-Ag deposit Quiruvilca, Peru. E.U.G., Strasbourg. Terra Abstracts: 42
Sillitoe RH (1983) Enargite-bearing massive sulphide deposits high in porphyry-copper system. Econ Geol 78: 348–352
Sillitoe RH (1988) Environments, styles and origins of gold deposits in western Pacific Island arcs. In: Bicentennial Gold 1988. Melbourne, Australia, pp 127–138
Thouvenin JM (1983) Les minéralisations polymétalliques à Pb-Zn-Cu-Ag de Huaron (Pérou central). Thesis, ENSM, Paris, 210pp
Wu I, Petersen U (1977) Geochemistry of tetrahedrite and mineral zoning at Casapalca, Peru. Econ Geol 72: 993–1016
Yamanaka T, Kato A (1976) Mössbauer effet study of57Fe and119Sn in stannite, stannoïdite, and mawsonite. Am Mineral 61: 260–265
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Marcoux, E., Milési, J.P. & Moëlo, Y. Vinciennite and Cu-excess tennantite from the Layo (Cu, Sn, As, Au) epithermal deposit (Southern Peru). Mineralogy and Petrology 51, 21–36 (1994). https://doi.org/10.1007/BF01164912
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DOI: https://doi.org/10.1007/BF01164912