煎茶岭硫化镍矿床成岩成矿作用的同位素地球化学证据  

Isotopic Geochemical Evidence of Rock-forming and Ore-forming Processes in the Jianchaling Sulfide Nickel Deposit, Lueyang County, Shaanxi Province

作　　者：瑞廷 毛景文[1] 任小华 赫英[3] 汤中立[4] 汪军谊 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]西北有色地质勘查局,陕西西安710054 [3]西北大学地质学系,陕西西安710069 [4]长安大学地球科学与资源学院,陕西西安710054

出　　处：《地球学报》2005年第6期513-519,共7页Acta Geoscientica Sinica

基　　金：国家重大基础研究发展规划项目(编号:1999043211);西北有色地质勘查局人才基金联合资助。

摘　　要：笔者通过ReOs同位素地球化学研究,在前人工作的基础上系统运用煎茶岭硫化镍矿床岩石及矿石的同位素资料对其成岩成矿作用进行了深入分析,认为煎茶岭超基性岩体自变质热液和蚀变流体主要来源于由岩浆水和地表水组成的混合水;其成岩物质来源于比较亏损的上地幔,但形成过程中有地壳硫的明显混染,岩浆同化混染富含硫、铁的围岩发生硫化作用,导致局部硫饱和发生硫化萃取作用而成矿,这是其成矿的重要机制。煎茶岭硫化镍矿床成矿过程中有含高放射性成因锇的壳源物质混染。多数矿石的锇同位素组成较接近富硫沉积物范围,反映地壳富硫围岩混染的效应;仅有一件矿石样品与地幔包体、球粒陨石地幔或科马提岩接近,暗示其深部地幔源区的性质。新元古代为煎茶岭镍矿床的主成矿期,形成大多数岩浆型矿石,但并不排除有一少部分矿石为后期热液作用形成。The rock-forming and ore-forming processes in the Jianchaling sulfide nickel deposit were systematically studied by using Re-Os isotopic method and analyzing other isotopic references available. The results show that the autometamorphic hydrothermal fluids and alteration fluids of Jianchaling ultrabasic intrusion were mainly derived from the mixed water composed of magmatic water and surface water, and the rock-forming substance originated from relatively depleted upper mantle, obviously contaminated by crustal sulfur during its formation. The assimilation of sulfur-and iron-rich wall rocks by the magma and the consequent sulfidation constitute an important metallogenic mechanism for the nickel deposit in that such a process caused local sulfur saturation and extraction leading to mineralization. In addition, there also existed the hybridization of the crustal substance which contained Os with high radioactivity during the formation of the sulfide nickel deposit. Os isotopic composition of most ores is close to that of sulfur-rich sediments, reflecting the hybridization effect of sulfur-rich surrounding rocks. Only one ore sample is compositionally close to mantle inclusion, chondrite mantle or komatiite, indicating the property of deep mantle source. New Proterozoic during which lots of magma-type ores were formed seems to be the main metallogenic period of the nickel deposit, with a small part of ores probably formed by later hydrothermal activities.

关 键 词：同位素 硫化镍矿床 成岩成矿作用 煎茶岭 

分 类 号：P597[天文地球—地球化学] P588.13[天文地球—地质学]