新疆库斯拉甫一带铅锌矿床成矿模式初探

PRELIMINARY DISCUSSION ON METALLOGENIC MODEL OF LEAD-ZINC DEPOSIT IN KUSILAFU AREA,XINJIANG

新疆库斯拉甫一带铅锌矿床数量众多,规模巨大,主要包括卡兰古、乌苏里克、托库孜阿特和托吾白等矿床。矿石中w(Ba)很高,为776×10^(-6)~15 511×10^(-6)(平均6 495×10^(-6)),Th/U值为0.42~1.26(平均0.91),稀土元素含量较低,ΣREE仅为27.4×10^(-6)~87.5×10^(-6)(平均49.9×10^(-6)),矿石的δEu为0.68~1.05(除一特高值2.53外),具有弱负Eu异常。矿石的Pb同位素表生年龄为461 Ma^508 Ma,δ^(34)S为-26.2‰^+3.4‰,范围较为宽泛,δD_(SMOW)值为-114‰^-70‰(平均-92‰);δ^(18) O_(SMOW)值为-1.70‰^-15.2‰(平均-8.24‰),图6中靠近大气降水线附近。综合分析认为铅锌矿床主要形成于有海底热水活动相对贫氧的非典型淡水海相环境,区域上西侧的寒武纪中酸性侵入岩和奥陶纪地层可能为铅锌矿的形成提供了初始的成矿物质来源,成矿流体主要以大气降水为主,成矿与低温热卤水关系密切,印支造山期后侏罗纪的伸展拉伸构造为成矿热卤水及海底热液的上涌提供了通道。

The Kalangu,Wusulike,Tuokuziate and Tuowubai lead-zinc ore deposits In Kusilafu area of Xinjiang are characteristic of high content of Ba ranging from 776 X 10-6 to 15 511 ）〈 10-6 （6 495X10-6 on average） ,and the ratios of Th/U range from 0.42 to 1.26 （0. 91 on average）. Geochemical study reveals that the EREE content in the ores is low, varying from 27.4 X 10-6 to 87.5 ）〈 10-6 （49.9 X 10-6 on average）, and 3Eu from 0.68 to 1.05 （2.53 is a special high value）, without significant negative Eu anomalies. The Pb isotope hypergene ages of ores are from 461 Ma to 508 Ma,with the 334S content of--26.2‰to ＋3.4‰. The analysis shows that the contents of 3DsMow and 318OsMow range from --114‰ to --70‰ （--92‰ on average） and from --1.70‰ to -- 15.2‰ （--8.24‰ on average） ,respectively,with plot near the meteoric water line in 3D-3180 dia- gram. Through comprehensive analysis, it is considered that the lead-zinc deposits are mainly formed in the non typical freshwater marine environment with relatively low oxygen. The Cambri- an intermediate acid intrusive rocks and Ordovician strata of the region probably provide the ini- tial ore-forming material for the formation of lead-zinc deposits. Also, the ore-forming fluid is dominated by meteoric water and mineralization is closely related to the low temperature hot brine. Extensional structures in the late stage of Indosinian orogeny provides channel for up- welling of hydrothermal mineralization and hot brine.