新疆东天山多头山铁-铜矿区花岗岩类的年代学、地球化学、岩石成因及意义  

Geochronology,Geochemistry and Petrogenesis of Granitoids in the Duotoushan Fe-Cu Deposit,Eastern Tianshan,Xinjiang:Implications on Tectonic Setting of Late Paleozoic Magmatism

作　　者：张维峰[1,2] 陈华勇 江宏君[1,2] 陆万俭 梁培 许超[1,2] 严学录 杨俊弢 ZHANG Weifeng;CHEN Huayong;JIANG Hongjun;LU Wanjian;LIANG Pei;XU Chao;YAN Xuelu;YANG Juntao(CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, Guangdong, China;University of Chinese Academy of Sciences, Beijing 100049, China;No.1 Geological Party, Xinjiang Bureau of Geology and Mineral Exploration, Changji 831100,Xinjiang, China)

机构地区：[1]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广东广州510640 [2]中国科学院大学,北京100049 [3]新疆地质矿产勘查局第一地质大队,新疆昌吉831100

出　　处：《大地构造与成矿学》2017年第6期1171-1191,共21页Geotectonica et Metallogenia

基　　金：重点基础研究计划"973"项目"新疆北部古弧盆体系成矿机理"(2014CB440802)资助

摘　　要：多头山矿床是东天山阿奇山?雅满苏成矿带铁铜矿床的典型代表,矿床成因与区内岩浆岩有紧密联系。矿区出露的侵入岩主要有花岗斑岩、二长花岗岩、钾长花岗岩及英安玢岩。LA-ICP-MS锆石U-Pb年代学研究获得花岗斑岩、二长花岗岩及英安玢岩的年龄分别为316.3±8.1 Ma、318.3±3.0 Ma和197.2±3.5 Ma。花岗斑岩A/CNK介于0.82~1.01之间,显示偏铝质特征,为Ⅰ型花岗岩;同时样品富集大离子亲石元素Th、U、Pb,亏损高场强元素Nb、Ta、Ti,显示弧岩浆特征。钠质蚀变导致了花岗斑岩显示出富Na、贫K、Rb、Ca、Sr的特征。钠化花岗斑岩Nb/Ta为12.4~16.0,具有较高的ε_(Nd)(t)(5.76~6.24)值和较低的I_(Sr)值(0.70353~0.70532),与安第斯中生代岩基地球化学特征相似,结合样品中出现古老锆石的捕掳晶,表明其源区为新生的下地壳,混合有少量幔源物质,并伴随有地壳混染。二长花岗岩与钠化花岗斑岩具有相近的形成年龄和相似的地球化学特征,如Nb/Ta比值(14.2),亏损高场强元素、富集大离子亲石元素,同为准铝质(A/CNK=0.97)弧岩浆,暗示它们可能具有相似的源区。而早侏罗世的英安玢岩具有高Sr(552×10^(-6))含量和较高的Sr/Y(73.6)比值,显示出钙碱性埃达克岩的特征,同时样品具有较高的K_2O(3.27%)含量、Mg~#指数(55),表明其来源于拆沉下地壳的熔融并混有少量幔源岩浆。综合区域研究资料、年代学、地球化学及同位素特征,我们认为多头山所在的阿奇山?雅满苏成矿带可能是晚古生代洋壳向南俯冲至中天山地块之下形成的大陆边缘弧。Like the other Fe-Cu deposits in the Aqishan-Yamansu belt,the ore genesis of the Duotoushan deposit is believed to be closely associated with granitic magmatism.The exposed intrusive rocks at the Duotoushan deposit are mainly granite porphyry,monzonitic granite,granite and dacite porphyry.Zircon U-Pb dating yielded ages of316.3Ma,318.3Ma,and197.2Ma for the granite porphyry,monzonitic granite,and dacite porphyry,respectively.The granite porphyry shows metaluminous affinity,with A/CNK values of0.82-1.01.The granite porphyry is enriched in Th,U and Pb,depleted in Nb,Ta,and Ti,displaying I-type and normal arc magma geochemical features.Due to sodic alteration,Na content of the rocks are enhanced,whereas Ca,K,Rb,Sr contents are reduced.The albitized granite porphyry have wide range of Nb/Ta(12.4-16.0)ratios,the appearance of zircon xenocrysts,along with positiveεNd(t)(5.76-6.24)and low ISr values(0.70353-0.70532).The geochemical features indicate that the magma could be derived from a juvenile lower crust with minor mantle component inputs and crustal contamination,which are similar to the Mesozoic Coastal Batholiths in the Central Andes.The Duotoushan monzonitic granite may have magma source similar to the uartz albite porphyry,as is demonstrated by the identical Nb/Ta(14.2)ratios,and similar geochronology and geochemical features.Whilst,the early Jurassic dacite porphyry has high Sr/Y(73.6)ratio and Sr(552-10?6)contents,indicative of an adakite affinity.Combined with high K2O(3.27%)and Mg#(55)values,we suggest that they were probably derived from melting of the delaminated lower crust that mixed with some mantle-derived materials.Integrating the data obtained from studies on geology,geochronology,geochemistry and isotopic compositions,we propose that the Aqishan-Yamansu metallogenic belt may have been generated by the southward subduction of the Kanggur Ocean beneath the Central Tianshan Plate during the late Paleozoic.

关 键 词：岩石成因 I型花岗岩 埃达克岩 晚古生代 中生代 东天山 

分 类 号：P597[天文地球—地球化学] P595[天文地球—地质学]