海南岛西南几个金矿床成矿流体与稳定同位素地球化学

ORE-FORMING FLUIDS AND STABLE ISOTOPE GEOCHEMISTRY OF SEVERAL GOLD DEPOSITS IN SOUTHWESTERN HAINAN ISLAND

二甲、抱板、不磨三个金矿床位于海南岛西部,沿北东向戈枕断裂带分布,含金脉体产于中元古代抱板群中,受韧性剪切带控制。其成矿流体是中温(250～350℃)、低盐度(4wt％～10wt％NaCl)、较富CO_2+CH_4的流体,氢、氧、硫同位素研究证明主要为变质一混合岩化热液矿床,成矿物质大多来自抱板群矿源层。雅亮伴生金矿位于海南岛南部,沿东西向九所—陵水深断裂分布,同位素研究表明该矿床为一低温(150～200℃)岩浆热液矿床,成矿物质主要来自地壳深部.

Ore-forming fluids and stable isotopes of the Erjia, Baoban, Bumo and Yaliang gold deposits located in southwestern Hainan island have been preliminarily studied, with a discussion given on their geneses. The first three deposits are distributed along the NE-trending Gezhen faulted zone in the west of the island. Gold-bearing veins occur in metasedimentary (±metavolcanic) sequences of the Middle Proterozoic Baoban Group and are controlled by ductile shear zones. The gold deposits might be divided into mylonite type (Erjia and Baoban)and quartz vein type(Bumo), and the ore-forming process of each type may be regarded as consisting of 2～3 metallogenic stages. Microthermometric measurements of fluid inclusions in quartz from these deposits indicate that the early ore-forming fluid was a hydrothermal solution of moderate temperature(250～350℃)and low salinity(4～10wt% NaCl equivalent) , whereas the middle-late stage ore-forming fluid had relatively lower temperature(150～250℃)and similar salinity. Ghemical analyses of fluid inclusions in quartz indicate the presence of abundant CO_2+CH_4 in the ore-forming fluid. Oxygen, hydrogen and sulfur isotope studies show that these deposits are mainly metamorphic-migmatized hydrothermal deposits with a small amount of meteoric water and that their ore--forming materials were largely derived form the source bed--Baoban Group.However, the ore-forming fluids of these deposits were transformed into recirculating meteoric water in the middle-late mineralization stages. The Yaliang gold-silver deposit is situated in the south of Hainan island and spreads along the east-west Jiusvlo-LJngshui deep fault zone.Gold-bearing and silver-rich polymetallic quartz veins occur in a fault zone of the Yanshanian syntectic or I-type granitoids that comprise Yaliang stock. Based on lead, sulfur, oxygen and hydrogen isotope studies, it is considered that the deposit is an epithermal(150～200℃)deposit with mixed magmatic and meteoric waters, in which the ore-forming materials were mainly derived from the deep crust. According to the above study combined with other geological data, the authors infer that there probably exists a gold-silver ore belt associated with Yanshanian granites and volcanic rocks along the Jiusuo-Lingshui deep fault zone.