甘肃北山地区狼娃山铁矿床地质地球化学特征及成矿机理探讨

Geological-geochemical characteristics and discussion on metallogeneticmechanism of Langwashan iron deposit in Beishan area,Gansu

横跨甘肃新疆内蒙古的北山地区是我国西北地区重要的黑色、有色及稀贵金属成矿潜力区。狼娃山铁矿为我国西北地区重要的磁铁矿床,目前为中型规模,其地处北山构造带中重要的铁、金多金属成矿带内,成矿地质条件优越,找矿勘查潜力大,但矿床研究程度较低,对其成矿环境、形成规律的认识尚不清晰,矿床成因存在较大争议。在已有勘查、研究的基础上,结合大量野外调查研究成果,在对主要矿体进行类型初识区分的前提下,通过对区域成矿背景、矿床地质、地球化学特征等进一步厘定,探讨矿体形成机理。研究表明,狼娃山铁矿主要形成于晚古生代红石山洋向塔里木板块俯冲所形成的陆缘弧环境,成矿与火山活动关系密切,且受控于俯冲带流体的交代,成矿物质主要源自地幔楔经交代熔融所形成的富铁岩浆,矿体主要形成于幔源富铁岩浆分异结晶及后期火山热液的充填交代过程,属海相火山喷流沉积-叠加改造型成因。

Beishan Tectonic belt,conjuncting among Gansu,Xinjiang and Inner Mongolia,is an important metallogenic potential area for black,non-ferrous and rare and precious metals in Northwest China.Langwashan iron deposit,an important medium-scale magnetite deposit in Northwest China,is located at the important Fe-Au polymetallic ore belt in Beishan tectonic zone.It has the superior metallogenic geological condition and a great potential for exploration and prospecting.However,the understanding of the metallogenic environment and metallogenic regularity is still unclear,and the metallogenic mechanism of the deposit are still controversial.Based on the existing exploration works,combined with a large number of field investigation and research results,this study further defines the regional metallogenic background,geological and geochemical characteristics of the deposit,and discusses the genesis and metallogenic mechanism.The result suggests that Langwashan iron deposit is mainly formed in the continental margin arc environment for the subduction of Latepaleozoic Hongshishan ocean to Tarim plate.The mineralization is closely related to the volcanic activity and controlled by the metasomatism of the subduction zone fluid.The ore-forming material mainly originates from the Fe-rich magma formed by the metasomatic melting of mantle wedge.The ore body is mainly formed in the process of Fe-rich magma differentiation and the filling and replacement of volcanic hydrothermal fluid in the later stage.The deposit belongs to the origin of marine volcanic eruption deposition-superimposed transformation type.