新疆北山二叠纪镁铁-超镁铁质岩成因、成矿作用和找矿信息  

Petrogenesis, Mineralization and Prospecting Information of Permian MaficUltramafic Rocks, Beishan, Xinjiang

作　　者：阮班晓[1] 吕新彪[1] 俞颖敏 刘月高 柳潇 魏巍[1] 王鹏 王恒 Ruan Banxiao;LüXinbiao;Yu Yingmin;Liu Yuegao;Liu Xiao;Wei Wei;Wang Peng;Wang Heng(Institute of Geological Survey,China University of Geosciences,Wuhan 430074,China;State Key Laboratory of Metallogenesis of Endogenic Metallic Deposits,Nanjing University,Nanjing 210023,China;CAS Key Laboratory for Experimental Study under Deep-Sea Extreme Conditions,Institute of Deep-Sea Science and Engineering,Chinese Academy of Sciences,Sanya 572000,China;Wuhan Center of China Geological Survey,Wuhan 430205,China;No.6 Geological Party,Xinjiang Bureau of Geology and Mineral Exploration and Development,Hami 839000,China)

机构地区：[1]中国地质大学地质调查研究院,湖北武汉430074 [2]南京大学内生金属矿床成矿作用国家重点实验室,江苏南京210023 [3]中国科学院深海科学与工程研究所深海极端环境模拟重点实验室,海南三亚572000 [4]中国地质调查局武汉地质调查中心,湖北武汉430205 [5]新疆地矿局第六地质大队,新疆哈密839000

出　　处：《地球科学》2020年第12期4481-4497,共17页Earth Science

基　　金：国家自然科学基金项目(No.41802101);新疆358项目(No.XGMB2012012);中国地质调查项目(No.DD20179607);教育部中央高校基本科研基金项目(Nos.G1323541879,G1323541839)。

摘　　要：为认识新疆北山二叠纪镁铁-超镁铁质岩石成岩成矿作用,基于地质调查获得的新资料,对这套岩石存在争议或认识模糊的年代学、岩浆起源与性质、动力学背景、硫化物熔离机制等进行了重新梳理.区内幔源岩浆除了早二叠世大规模侵入,中二叠世还有一期小规模侵入(261~266 Ma).母岩浆起源于受俯冲流体交代改造的亏损地幔在相对浅的深度发生高程度部分熔融,其具高温、高镁、含水、氧化特征.这些岩石并非地幔柱成因,亦非产于岛弧环境,而是造山后伸展背景下板片断裂引起的软流圈地幔上涌形成镁铁质侵入岩.坡北亚带和红石山亚带具有类似的岩石矿物组合和地球化学特征,但是矿化方式有明显差异.不同类型矿化是硫化物多期次熔离的产物,来自邻近VMS型铜矿床的外源硫混染触发硫化物在橄榄石结晶分异之前熔离,高品位脉状矿化是硫化物矿浆晚期贯入苏长岩的产物.超镁铁质岩相橄榄石中较低的Ni含量,岩体低Ti、高Mg、高m/s和m/f比值、母岩浆MgO含量大于11.5%、部分熔融程度不低于10%、固结指数SI大于50,均是有利的找矿指标,红十井深大断裂一带可能具有找矿潜力.A series of Permian mafic-ultramafic complexes associated with large and medium-sized Ni deposits have been found in recent decades in the Beishan area, Xinjiang, NW China. Based on the new data obtained from the geological survey, a few controversial scientific issues, such as geochronology, the origin and nature of parental magma, tectonic setting, sulfide immiscibility mechanism, etc., are redefined. Two episodes of mafic magmatism in the Beishan area were recognized. i. e. the Early Permian and Middle Permian(261-266 Ma). The parental magma may have originated from high degree partial melting of the depleted mantle which suffered from metasomatism and modification by subduction-related fluid in relatively shallow depth. It is characterized by high temperature, high Mg content, oxidized and hydrous nature. The Beishan mafic-ultramafic rocks are of non-plume origin, as well as of non-arc origin. The tectonic setting seems more likely slab break-off and consequent upwelling from an asthenosphere mantle in post-orogenic setting. The Pobei sub-belt and the Hongshishan sub-belt have similar rock types and geochemical features, but di ff erent mineralization types, suggesting multi-stages and differences of sulfide segregation mechanism. Addition of external S from adjacent VMS Cu deposits triggers sulfide segregation prior to olivine crystallization.Injection of ore pulp to later norite gives rise to vein-type mineralization with high Ni tenor. Finally, some indicators are proposed for the future prospecting, for example, relatively low Ni content in olivine from ultramafic rocks, high Mg but low Ti contents,high m/s and m/f ratios, tholeiitic parental magma(>11.5% MgO), relatively high degree of partial melting(>10%) and high solidification index(>50). The area along the Hongshijing deep fault is of further prospecting potential.

关 键 词：镁铁-超镁铁质岩 二叠纪 非地幔柱成因 多期次熔离 成矿模式 找矿信息 新疆北山 

分 类 号：P612[天文地球—矿床学]