Ore-forming P-T-X conditions and the nature of gold occurrence in the Shaxi-Changpushan porphyry copper deposit, central Anhui Province, eastern China, were investigated employing a wide range of geological and geochemical methods. Our results document liquid-vapour conditions and show that abundant fluid inclusions occur in quartz veins accompanied by pyrite-chalcopyrite-gold mineralization. Most economic deposits involved coexisting liquid and gas phases, whereas a few formed in equilibrium with a homogeneous aqueous liquid. The ore-forming temperature lies between 230 and 350 degrees C. Isotope studies show that the 34S values are between -0.20 and 3.00 parts per thousand for most of the sulphides; 34S values of chalcopyrite are somewhat more homogenous than those of pyrite. Ore-forming fluids and materials were mainly derived from magmatic sources. Meteoric water played a small role in the ore-forming process, judging by the oxygen and hydrogen isotope data for fluid inclusions measured by the explosion method (18O values ranging from 3.51 to 5.52 parts per thousand, and D ranging from -59.8 parts per thousand to -82.4 parts per thousand). In the ore deposit, the gold occurs as micro-inclusions heterogeneously distributed in chalcopyrite and pyrite. Gold mineralization is positively correlated with As in chalcopyrite, pyrite, and some Cu-bearing ores. Igneous rocks and sedimentary rock distributions in the Shaxi-Changpushan ore district were strictly controlled by the regional fault system since the Jurassic period, especially the Tan-Lu fault system in east China. Intrusive bodies comprising porphyritic quartz dioritoid, biotite-quartz dioritoid, and fine-grained dioritoid are ore-bearing, cutting sedimentary rocks of the Upper Jurassic and Middle-Lower Silurian series. Sediments exposed in the ore district consist of Upper Devonian-Middle Silurian clastic rocks, Middle and Lower Jurassic and Upper Cretaceous terrestrial clastic rock series. Petrologic data show that formation of Cu-Au ore bodies was related to adakitic intrusives in the Shaxi-Changpushan area. Based on geochemical exploration and the tectonic background of the southern part of Tan-Lu fault zone, we propose a porphyric copper (gold) ore-forming model for the Lower Yangtze metallogenic belt: ore bodies were controlled by structural shielding in the core of the regional anticline. Combined geological and geochemical evidence suggests that a super-large porphyry (gold) deposit may be present in the region.
| Publication name |
INTERNATIONAL GEOLOGY REVIEW Volume: 53 Issue: 5-6 Special Issue: Sp. Iss. SI Pages: 580-611 Published: 2011 |
| Author(s) |
Yang, Xiaoyong; Yang, Xueming; Zhang, Zhengwei; Chi, Yueyu; Yu, Liangfan; Zhang, Qianming |
| Corresponding author |
YANG, Xiaoyong
xyyang555@163.com
1. Univ Sci & Technol China, CAS Key Lab Crust Mantle Mat & Environm, Hefei 230026, Peoples R China
2. Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang, Peoples R China |
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