Sulfidation State of Fluids in Active and Extinct Hydrothermal Systems: Transitions from Porphyry to Epithermal Environments

Sulfidation State of Fluids in Active and Extinct Hydrothermal Systems: Transitions from Porphyry to Epithermal Environments
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DOI:
10.5382/sp.10.15
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发表时间:
2003
期刊:
--
影响因子:
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通讯作者:
M. Einaudi;J. W. Hedenquist
M. Einaudi;J. W. Hedenquist
中科院分区:
其他
文献类型:
--
作者:
M. Einaudi;J. W. Hedenquist

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Use of the concept of "sulfidation state", in parallel with oxidation state, in the study of ore deposits finds its beginnings with the studies of Reno Sales and Charles Meyer at Butte, Montana. Experimental determination of the stability of sulfide minerals in terms of f S2 and temperature followed, leading to definition of contrasts in ore-forming environments. More recent studies of vapor compositions in active volcanic and geothermal systems allow direct comparisons with geochemical environments deduced from petrologic study. In this paper, we present a compilation of oxidation and sulfidation states of fresh igneous rocks from arc environments and on sulfidation states of sulfide assemblages in calc-alkalic porphyry copper, porphyry-related base-metal veins, and epithermal gold-silver deposits. These data are contrasted with compositions of fluids from active systems by plotting vapor compositions on log f S2 – 1000/T, RH – 1000/T, RS – 1000/T diagrams, where RH ≈ log (X H2 / X H2O), RS ≈ log ( X H2 / X H2S ) and X = mole fraction of the gas. Oxidation states of andesitic arc magmas plot in a tight cluster between fayalite + magnetite + quartz and pyrrhotite + pyrite + magnetite. On equilibrating below the solidus, arc plutons deviate toward higher oxidation states. Sulfidation states of arc magmas are very low to