Abstract:The formation of Duobaoshan porphyry copper deposit is a result of the favorable combination of various geological factors. Genetically, the deposit is not only related to the magmatic and hydrothermal activities, but also governed by some stratigraphic and structural factors. According to statistics, the tops of large-sized orebodies are mostly confined to the andesite in the lower part of the Middle Duobaoshan Group. Only small orebodies with much weaker mineralization sometimes have their tops located in other strata. Average copper content of the rocks of the Duobaoshan Group is 135 ppm. The middle and lower portions of orebodies lie in the granodiorite (292 m. y.). The granodiorite and the granodioritic porphyry (283 m.y.) intruding it were of passive emplacement along the pre-existing tectonic channels. The contact surfaces between intrusions and country rocks are complex, containing a large number of pendants, xenoliths and magmatic conglomerates. The country rocks underwent various degrees of weak thermal metamorphism, and the intrusive rocks were crushed and altered to various extent everywhere. Copper mineralization occurs in a NW trending shear-compressional fracture zone, while magmatic emplacement and hydrothermal process took place during the period of the tectonic movement in the NE trending shear-compressional fracture zone. When the tectonic movement in the NE trending fractures happened, NW trending fractures opened, and then passive magmatic emplacement and hydrothermal process occurred. A quartz core is present in the middle of the deposit, From it outward there appear in sequence ovoid (quartz-perthite-) biotitization, (quartz-chlorite-) sericitization and propylitization zones. The copper mineralization occurs inside the sericitization zone superimposed on the biotitization zone. Within the (quartz-chlorite-) sericitization zone bornite seems concentrated chiefly in the central portion, from it outward bornite gradually decreases while chalcopyrite increases. But chalcopyrite suddenly disappears near the periphery, where pyrite becomes predominant. The zonation of minerals is outlined in this papen. The evolution of intrusion-alteration-mineralization is indicated in Figure A-R.
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杜琦, 陈明秀.1983.多宝山斑岩铜矿床成因模式[J].矿床地质,2(2):42~48.1983.The genetic model of Duobaoshan porphyry copper deposit[J].Mineral Deposits2(2):42~48
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