Oxidized Granitic Magmas and Porphyry Copper Mineralization
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Absence or presence of modal magnetite and whole-rock Fe2O3/FeO ratio of granitoids have been potentially used to recognize the bimodal series of granioids in Japan viz. magnetite-series and ilmenite-series granitoids corresponding to oxidized and reduced granitoids respectively. Oxidized granitoids are mostly responsible for the origin of metallic (copper and gold) sulfide deposits particularly of porphyry nature. Oxidation status of some copper-hosting Precambrian and Phanerozoic granitoids have been assessed in order to understand intrinsic properties of source regions and prevailed oxygenated environment evolving through time. Chemistry of hydrous mafic silicates (amphibole and biotite) and apatite has also been discussed specifically to characterize the mineralized, oxidized granitoids and explaining the key role of F, Cl and SO3 as potential carrier of ore metals in hydrothermal system emanated from granitic magmas respectively.
KeywordsOxidized granitoids Magnetite-series Ferric/ferrous ratio Porphyry copper Mafic silicates Apatite
The authors wish to acknowledge Joseph B. Whalen and W. J. Davis for providing unpublished data. Santosh Kumar is thanked for generous comments on the earlier version and meticulous editorial work.
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