巴林左旗双尖子山银多金属矿床基本地质特征及成因机制

摘要

巴林左旗双尖子山银（铅、锌）矿床位于大兴安岭南段，为超大型热液脉型矿床，在时空分布上与中生代构造—岩浆岩关系密切。双尖子山银多金属矿化多呈席状、细脉浸染状、网脉—脉状在下二叠统大石寨组火山—沉积岩产出，并且构成似层状、（长）扁豆状、透镜状和囊状矿体。初步研究表明：与银多金属共生的绢云母和辉钼矿同位素年龄分别为146.9±1.9 Ma和162.6±2.6 Ma，与区域侏罗纪火山岩同位素年龄160～147 Ma基本一致。根据矿区外围白音诺尔花岗岩体锆石年龄142～115 Ma，可以推测双尖子山银多金属主成矿作用与侏罗纪构造—岩浆活动相关，而与后期大规模中酸性岩浆侵位并无直接的成因联系。根据矿床产出环境、矿化和热液蚀变特征的初步研究结果表明，双尖子山可能经历了多次矿化的叠加，其可能与古太平洋板块远程俯冲和中生代动力机制转换作用有关。%Located in the southern segment of the Great Hinggan Mts.(Da Hinggan Range,or Great Xing’an Mts.)in Hinggan—Mongolia Orogenic Belt (XMOB),the Shuangjianzishan Ag—polymetallic deposit in Balinzuo Qi(Balin Zuoqi;Baarin Left Banner)is a newly discovered superlarge scale epithermal deposit,which is closely related to the Mesozoic tectono-magmatic activities in space,age and genesis.The polymetallic mineralization (Ag, Zn,Pb,and Cu)hosted by the volcano—sedimentary rocks is composed of the layered,lenticular,wedge shaped and cystic orebodies occurring as disseminated,vein,sheet,and veinlets.Preliminary study showed that the sericite yielded an Ar-Ar plateau age of 146.9 ± 1.9 Ma,and the molybdenite from the silver polymetallic ore yielded a model age of 162.6 ±2.6 Ma.These two ages are identical with the age of regional Jurassic volcanic rocks (160~147 Ma).Therefore,the formation of the Shuangjianzishan silver polymetallic deposit is related to the Jurassic tectono—magmatic activities caused mainly by the remote effect of the subduction of the Mesozoic Paleo-Pacific plate during the tectonic transformation.