首页|Reduced magma generation and its implications for the Pulang giant porphyry Cu-polymetallic deposit in Northwest Yunnan,China
Reduced magma generation and its implications for the Pulang giant porphyry Cu-polymetallic deposit in Northwest Yunnan,China
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Reduced magma generation and its implications for the Pulang giant porphyry Cu-polymetallic deposit in Northwest Yunnan,China
The Pulang giant porphyry Cu-Mo polymetal-lic deposit is located in the Zhongdian area in the center of the Sanjiang Tethys tectonic domain,which was formed by the westward subduction of the Garze-Litang oceanic slab beneath the Zhongza massif.Chalcopyrite-pyrrhotite-pyrite-molybdenite occurs as disseminations,veins,veinlets,and stockworks distributed in the K-silicate alteration zone in the monzonite porphyry,which is superimposed by propylitiza-tion.The chemical compositions of biotite and amphibole analyzed by electron probe microanalysis(EPMA)indicate that the ore-forming magma and exsolved fluids experienced a continuous decrease in the oxygen fugacity(fO2).Primary amphibolite and biotite(type Ⅰ)crystallized at relatively high temperatures(744-827 ℃)and low fO2(logfO2=-12.26 to-11.91)during the magmatic stage.Hydrothermal fluids exsolved from the magma have a relatively lower tempera-ture(621-711 ℃)and fO2(logfO2=-14.36 to-13.32)than the original magma.In addition,the presence of a high abundance of pyrrhotite and an insufficiency of pri-mary magnetite and sulfate in the ore(i.e.,anhydrite and gypsum)indicate that the deposit may be a reduced por-phyry deposit.Magma and fluid fO2 results,combined with previous research on magmatic fO2 at the Pulang deposit,indicate that the magma associated with the reduced Pulang ore assemblages was initially generated as a highly oxidized magma that was subsequently reduced by sedimentary rocks of the Tumugou Formation.
Porphyry depositOxygen fugacity(fO2)Contamination of surrounding rockPulangZhongdian arc
Jingwei Guan、Tao Ren、Lei Wang、Shenjin Guan、Lianrong Wu、Baosheng Shi
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Faculty of Land Resources Engineering,Kunming University of Science and Technology,Kunming 650093,People's Republic of China
Diqing Nonferrous Metals Co.,Ltd,Shangri-La 674400,People's Republic of China
Porphyry deposit Oxygen fugacity(fO2) Contamination of surrounding rock Pulang Zhongdian arc
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