大陆碰撞成矿作用:Ⅰ.冈底斯新生代斑岩成矿系统  

Metallogenesis of continental collision setting:Part Ⅰ.Gangdese Cenozoic porphyry Cu-Mo systems in Tibet

作　　者：侯增谦[1] 郑远川[1] 杨志明[1] 杨竹森[2] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质科学院矿产资源研究所,北京100037

出　　处：《矿床地质》2012年第4期647-670,共24页Mineral Deposits

基　　金：国家重点基础研究发展计划(973计划)项目(编号:2011CB4031006);国家自然科学基金重点项目(编号:238925;40425014);地质调查项目(编号:1212011121255)联合资助

摘　　要：火山岩浆弧和大陆碰撞带是产出巨型斑岩矿床的两类重要环境。岩浆弧环境的斑岩铜矿成矿理论业已建立,而大陆碰撞环境的斑岩矿床则研究薄弱。在青藏高原,印度-亚洲大陆碰撞导致了大规模斑岩成矿作用,在主碰撞期(65～41Ma)发育沙让式斑岩Mo矿和亚贵拉式斑岩-矽卡岩型Pb-Zn-Mo矿床,在晚碰撞期(40～26Ma)形成明则式斑岩Mo矿和努日式斑岩-矽卡岩型Mo-W-Cu矿床,在后碰撞期(25～13Ma)产生驱龙式斑岩Cu-Mo矿床。这些矿床构成了3条规模不等的成矿带,分别发育在冈底斯的北带(中拉萨地体)、南带(泽当弧地体)和中带(南拉萨地体)。冈底斯含矿斑岩系统通常为多期多相浅成侵入杂岩体。含矿斑岩以高K为特征,多为高K钙碱性岩和钾玄岩系列。含Cu斑岩以二长花岗斑岩为主,显示埃达克岩地球化学亲和性,含Mo斑岩以花岗斑岩为主,显示大陆壳成因特点。微量元素和Sr-Nd-Hf同位素地球化学研究表明,含Cu斑岩来自碰撞加厚的西藏镁铁质的新生下地壳(如角闪榴辉岩),早期卷入新生下地壳的幔源物质及硫化物的重熔为斑岩岩浆提供了部分金属Cu、Au和S;含Mo岩浆来自古老的西藏镁铁质下地壳(如角闪岩)的部分熔融,金属Mo主要来自古老地壳物质的贡献。冈底斯含矿斑岩均含有不同成分的微粒镁铁质包体(MME),并显示典型的长英质与镁铁质岩浆混合特征。以MME为代表的含Cu富H2O幔源岩浆,或底侵于冈底斯地壳底部,为下地壳熔融提供了热和H2O,或注入长英质岩浆房,为斑岩系统提供了部分金属Cu和S,并提升了岩浆氧逸度。冈底斯斑岩岩浆-热液-成矿系统受控于斑岩就位的地壳环境。在斑岩体侵位的花岗岩基环境,其良好的封闭性导致热液流体(岩浆出溶)以斑岩岩株为核心向外扩散,形成环状蚀变分带,并主要在钾硅酸盐化带发生Cu-Mo矿化;在碎屑岩-碳酸盐建造环境,碳酸盐建造发生矽卡�Giant porphyry deposits are generally found in magmatic arcs and continent collisional belt.Metallogenic theory of the porphyry copper deposit under the magmatic arc condition has been well established,while that in the continental collision setting has not been formed.A large number of porphyry deposits were formed in Tibetan plateau as the result of collision between the India and the Lhasa plates.Three different porphyry deposit belts have been found in the Lhasa terrene.The Sharang-type porphyry Mo deposit and the Yaguila-type porphyry-skarn Pb-Zn-Cu deposit distributed along the north margin of the Gangdese belt（the central Lhasa terrane） were formed in the main-collisional period（65～41 Ma）.The Mingze-type porphyry Mo deposit and the Nuri-type porphyry-skarn Cu-Wu-Mo deposit in the central part of the Gangdese belt（southern Lhasa terrane） were formed in late-collisional period（40～26 Ma）,whereas the Qulong-type porphyry Cu-Mo deposits developed in the Zedong arc belt was formed in the post-collisional period（25～13 Ma）.The fertile Gangdese porphyry systems are generally composed of multistage hypergenic intrusive complexes.These complexes are generally characterized by high-K,and most of them are K calc-alkali and shoshonitic in composition.The Cu-bearing porphyries are dominated by monzogranite,and generally show geochemical affinity to adakites,while the Mo-bearing porphyry deposits are mainly associated with granite,which was most likely derived from continental crust.Whole-rock geochemistry and Sr-Nd-Hf isotopic data indicate that the Cu-bearing magmas were most probably derived from the thickened juvenile mafic lower-crust beneath south Tibet.The melting of sulfide-bearing phases in the juvenile mantle components of the Tibetan lower-crust probably provided parts of Cu,Au and S for the fertile magmas.However,the Mo-bearing magmas were likely derived from partial melting of the ancient Tibetan lower crust,while Mo was also mainly derived from the ancient crust.Large amounts of mic

关 键 词：地质学 斑岩矿床 围岩建造 深部过程 成矿作用 大陆碰撞造山 青藏高原 

分 类 号：P611[天文地球—矿床学]