Oxygen and sulfur isotopic compositions of quartz, anhydrite and sulfide minerals from the El Teniente and Rio Blanco porphyry copper deposits, Chile

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Authors:Kusakabe, Minoru; Nakagawa, Seiko; Hori, Mika; Matsuhisa, Yukihiro; Ojeda, Jose Miguel; Serrano, Luis
Author Affiliations:Primary:
Toyama Univ., Gofuku, Toyama, Japan
Geol. Surv. Japan, Japan
Corp. Nac. Cobre Chile, Chile
Volume Title:Special issue for overseas geology and mineral resources; (I), Calc-alkaline magmatism and related mineralization in Chile
Source:Special issue for overseas geology and mineral resources; (I), Calc-alkaline magmatism and related mineralization in Chile. Chishitsu Chosajo Geppo = Bulletin of the Geological Survey of Japan, 35(11), p.583-614. Publisher: Kogyo Gijutsu-in-Chishitsu Chosajo, Kawasaki, Japan. ISSN: 0016-7665
Publication Date:1984
Note:In English with Japanese summary. 31 refs.; illus. incl. 5 tables, sects., geol. sketch maps
Summary:At El Teniente, the average delta 18O values of anhydrite and quartz are lowest in stage I (potassic alteration), and increase gradually through stages II and III (phyllic alteration) with a marked increase in stage IV (latest mineralization). This isotopic behaviour suggests that the minerals were precipitated from a common fluid in oxygen isotopic equilibrium. The anhydrite-chalcopyrite sulphur isotope geothermometer indicates that the mineralization T decreases from 460°C at stage I through 420-410°C at stages II and III down to 360°C at stage IV. A lower T of 300°C is indicated for stage IV by the chalcopyrite-galena geothermometer. With these T and oxygen isotopic data, the delta 18O value of the hydrothermal fluids is calculated to be virtually constant at 6per mille for all stages, suggesting that magmatic fluids or fluids of meteoric origin which had extensively interacted with wall-rocks might have been repeatedly incorporated during the primary mineralization- alteration processes. At Rio Blanco, participation of the similar fluids is indicated for mineralization because of the isotopic resemblance between the two deposits, although mineralization-alteration is not so clearly divided into different stages. The genesis of ore fluid is discussed with reference to the observed delta 34S values. [Y.K.]
Subjects:Alteration; Anhydrite; Classification; Copper ores; Economic geology; Endogene processes; Framework silicates; Gangue; Isotopes; Metal ores; Mineral deposits, genesis; O-18/O-16; Ore minerals; Oxygen; Polyphase processes; Porphyry copper; Quartz; S-34/S-32; Silica minerals; Silicates; Stable isotopes; Sulfates; Sulfides; Sulfur; Zoning; Chile; South America; Central Chile; El Teniente Deposit; Ratios; Rio Blanco Deposit
Abstract Numbers:88M/2142
Record ID:1985083679
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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