New evidence of magmatic-fluid–related phyllic alteration: Implications for the genesis of porphyry Cu deposits
- 1 January 2002
- journal article
- Published by Geological Society of America in Geology
Abstract
The phyllic alteration in a number of circum-Pacific porphyry Cu-Au deposits is related to high-temperature saline magmatic fluids. This contradicts the widely used genetic mod- els wherein phyllic alteration formed as the result of mixing between magmatic and me- teoric fluids. At the Endeavour 26 North porphyry deposit in eastern Australia, the tran- sition from early potassic to the main-stage phyllic alteration is associated with fluids that with time decline in total salinity, NaCl/KCl, and temperature from ;600 to ;550 8C. Calculated and measured d18O and dD compositions of fluids (5.1‰-8.5‰ d18O, 257‰ to 273‰ dD) confirm a primary magmatic origin for both the early potassic and main- stage phyllic alteration. These results are consistent with other recent studies (e.g., El Salvador, Chile, Far Southeast, Philippines, and Panguna and Porgera, Papua New Guin- ea) and suggest that, rather than these results being unusual, a major revision of porphyry Cu genetic models is required.Keywords
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