An oxygen- and hydrogen-isotope study of the Panguna porphyry-copper deposit, Bougainville
Titel:
An oxygen- and hydrogen-isotope study of the Panguna porphyry-copper deposit, Bougainville
Auteur:
Ford, J. H. Green, D. C.
Verschenen in:
Australian journal of earth sciences
Paginering:
Jaargang 24 (1977) nr. 1-2 pagina's 63-80
Jaar:
1977-03
Inhoud:
Hydrogen- and oxygen-isotope analyses of biotite (19), sericite (8), chlorite (2), quartz (27), and total rocks (37) from the Panguna porphyry-copper deposit on Bougainville Island, place important constraints on the origin of the hydrothermal fluids responsible for mineralization and alteration in the mine region. Early high-temperature amphibole-magnetite alteration resulted from magmatic-hydrothermal fluids. Several lines of evidence indicate 500°C as a realistic average temperature for mineralization, development of quartz veins, and biotitization processes. On the basis of mineral isotope data, responsible fluids could represent either 18O-shifted ground-waters or magmatic-hydrothermal fluids at submagmatic temperatures. Independent evidence, as well as total-rock 18O data, support the magmatic-hydrothermal model. Late-stage sericitization processes probably resulted from fluids produced by 18O shifting of groundwaters during the evolution of the propylitic zone. Outermost quartz veins and biotitization conceivably resulted from fluids similar to those that caused sericitization, indicating that some interaction between relatively cool, 18O-poor meteoric waters and the ore fluids occurred near the margins of the deposit. The origin of the chlorite-sericite alteration cannot be resolved solely by isotope studies.
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