Recent research of submarine massive sulfide deposit ( MSD) showed that the MSD generation was closely related to some processes of tectonic structure and volcanism, which occurred in a special period of tectonic evolution and generally ore-forming time-span within several million years. The Xitieshan deposit, located in the northern margin of the Qaidam basin, Qinghai Province, is the largest MSD in the northwest of China. Based on systematic petrochemical and geochemical research of ore-hosting volcanic rocks, named the Tanjianshan Group, it can be stated that, (1) petrochemistry and geochemistry of volcanic rocks of the Tanjianshan Group indicate that the magmas were originated from an identical source, evolving from acidic to mafic and thus generating various volcanic rocks with a transitional petrochemical and geochemical trend. (2) Attributes of REE and trace elements, and tectonic discrimination diagrams collectively display that the tectonic settings for generating the Tanjianshan Group volcanic had been evolved continuously from continental magmatic arc, through transitional arc, to oceanic basin. (3 ) The magma evolution and Rb-Sr isotope systematics imply that the tectonic setting of the Xitieshan MSD might be a continental back-arc basin similar to Okinawa tough in the southwest Pacific. (4) As to the mineral prediction, it is concluded that, the volcanic-sedimentary successions within the bimodal volcanic sequence formed during the early back-arc extension, are believed to be the important target in the Xitieshan orefield and its vicinities, but the upper stratigraphic successions of the Tanjianshan Group are not favorable in finding MSD mineralization.%近年来海底块状硫化物矿床的深入研究表明,块状硫化物矿床形成与其成矿构造环境演化期间特定阶段的构造-火山作用有关,矿床持续形成时间一般不超过几个百万年.锡铁山矿床是我国西北地区最大的海底热液块状硫化物铅锌矿床,本文通过锡铁山矿床赋矿岩系火山岩岩石化学及地球化学特征的系统研究,对锡铁山矿床赋矿火山岩系岩浆演化过程及成矿构造环境得出如下几点认识:(1)锡铁山矿区赋矿滩间山群火山岩岩石化学及地球化学特征一致表明滩间山群岩浆活动具有自酸性向基性同源岩浆演化的特点.矿区滩间山群不同岩组/段的火山岩代表了同源岩浆不同演化阶段的产物.自O1-2tna-1岩段、O1-2tnb岩组→O1-2tnd-1岩段→O1-2tnd-3岩段,矿区火山岩岩石化学及稀土与微量元素地球化学具有明显的渐变过渡关系.(2)矿区滩间山群火山岩稀土、微量元素组成特征度成岩构造环境判别图解一致揭示,从O1-2tna-1岩段、O1-2t nb岩组→O1-2tnd-1岩段→O1-2tnd-3岩段,滩间山群火山岩成岩构造环境经历了从陆缘基底岛弧→洋陆过渡型地壳→典型大洋地壳的连续过渡变化.(3)矿区滩间山群火山岩岩浆演化过程及Rb、Sr组分变化趋势与大陆边缘弧后盆地火山岩岩浆演化过程相近,与现代西太平洋冲绳海槽形成过程相似.(4)综上推断,矿区深部及外围找矿工作的重点对象是弧后盆地拉张早期形成的具有双峰式火山岩组合的下部火山-沉积组合,而矿区南部O1-2tnd岩组找寻同类矿床的可能性不大.
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