新疆乌恰县乌拉根铅锌矿床地质特征和S-Pb同位素组成

乌拉根矿床是喀什中新生界凹陷内新近勘查的具超大型远景的铅锌矿床。铅锌矿体呈板状，顺层分布于乌拉根向斜南、北两翼,容矿地层为下白垩统克孜勒苏群第五岩性段(K1kz5)褪色灰白色砂砾岩及古新统阿尔塔什组(E1a)泥质白云岩。矿石具块状、微细浸染状、细脉状、团斑状等构造及胶结结构、交代反映边结构等。乌拉根矿床硫化物δ34S值为-27.9‰~14.6‰,指示相邻层位中石膏、天青石等硫酸盐提供硫,同时有机物的热分解也可能作为硫的来源,硫的还原可能包括生物还原与有机质热化学还原两种模式。硫化物的206Pb/204Pb、207Pb/204Pb、208Pb/204Pb分别为18.528~18.663、15.611~15.669、38.616~38.839,极为均一,指示上地壳和造山带剥蚀区是成矿金属的来源。综合分析乌拉根铅锌矿床地质、地球化学特征,并与已有成因认识进行对比,判定乌拉根矿床是与盆地流体活动相关的砂岩型铅锌矿床。

Ore geology,S-and Pb-isotopic compositions of the Wulagen Zn-Pb deposit,Wuqia County,Xinjiang

The Wulagen zinc-lead deposit occurring in the Kashi Mesozoic-Cenozoic sedimentary sag,Xinjiang,is a newly explored deposit,with perspective of a super-large scale.The Zn-Pb ore-bodies of tabular shape occur in the northern and southern flanks of the Wulagen syncline,which are in parallel with the stratum and hosted in the faded gray sandstone-conglomerate of the fifth Member of Lower Cretaceous Kezilesu Group(K1kz5) and the mud-dolostones of Paleocene Aertashi Formation(E1a).The ores are characterized mainly by massive structure,micro-disseminated structure,veinlet structure,porphyritic structure,cemented texture,and metasomatic reaction edge texture.The sulfide δ34SV-CDT of the Wulagen deposit varies from-27.9‰ to 14.6‰,which indicates that the gypsum,celestite and other sulfate in the adjacent stratum provided sulfur,and that the thermal decomposition of sulfur-bearing organic matter may also be the source of the sulfur.Reduced sulfurs were mainly derived from the biogenic sulfate reduction and the thermo-chemical reduction of organic matter.The compositions of Pb isotopes of Wulagen deposit are homogenous(206Pb/204Pb=18.528-18.663,207Pb/204Pb=15.611-15.669,208Pb/204Pb=38.616-38.839),which indicates that the ore-forming materials came from the upper crust and orogenic erosion zone.Integrated analysis of geological characteristics and geochemistry of the Wulagen deposit and compared with the previous understanding of its genesis,we concluded that the Wulagen deposit is a basin fluid-related sandstone-type zinc-lead deposit.