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东昆仑祁漫塔格地区晚三叠世正长花岗岩岩石成因及构造意义
Petrogenesis and tectonic implications of the Late Triassic syenogranite in Qimantag area, East Kunlun Mountains
投稿时间:2017-02-14  
中文关键词:地球化学  锆石U-Pb年代学  Hf同位素  A型花岗岩  祁漫塔格
英文关键词:geochemistry  zircon U-Pb geochronology  Hf isotope  A-type granite  Qimantag
基金项目:国土资源部公益性行业科研专项经费项目(201411025);中国地质调查局地质调查项目(1212011085528);中国地质调查局高层次地质人才培养计划(201309);青年地质英才计划(201112)
作者单位E-mail
张明玉 中国地质科学院 矿产资源研究所 国土资源部成矿作用与资源评价重点实验室, 北京 100037  
丰成友 中国地质科学院 矿产资源研究所 国土资源部成矿作用与资源评价重点实验室, 北京 100037  
王辉 长安大学 地球科学与资源学院, 陕西 西安 710054  
李大新 中国地质科学院 矿产资源研究所 国土资源部成矿作用与资源评价重点实验室, 北京 100037  
瞿泓滢 中国地质科学院 矿产资源研究所 国土资源部成矿作用与资源评价重点实验室, 北京 100037 hongyingqu@126.com 
刘建楠 中国地质科学院 矿产资源研究所 国土资源部成矿作用与资源评价重点实验室, 北京 100037  
周建厚 中国地质科学院 矿产资源研究所 国土资源部成矿作用与资源评价重点实验室, 北京 100037  
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中文摘要:
      青海省东昆仑祁漫塔格地区肯德可克矿区外围东部发育一正长花岗岩体,主要矿物组合为正长石(50%~60%)+石英(20%~30%)+斜长石(10%~20%)+黑云母(1%~5%)。其LA-ICP-MS锆石U-Pb加权平均年龄为217.9±1.7 Ma(MSWD=0.74,n=20),形成时代为晚三叠世,与祁漫塔格地区铁多金属矿床基本同时形成。岩石地球化学组成具有高硅(SiO2=74.53%~75.28%)、富碱(K2O+Na2O=8.81%~8.95%)、富铁贫镁(FeOT/MgO=18.02~31.48)的特征,并具强烈的负Eu异常(δEu=0.04~0.05),富集Rb、Th、U、K、Ga,亏损Sr、Ba、Ta、P、Ti,显示其为准铝质A型花岗岩。正长花岗岩锆石εHf(t)为2.0~12.4,平均6.4,显示其源区具有壳幔混合作用的特征,壳幔物质交换为区内铁多金属矿化提供了大量成矿物质。该正长花岗岩属A2型花岗岩,暗示其形成于造山后的伸展构造体制,反映了祁漫塔格地区晚华力西-印支期造山旋回于晚三叠世由造山后期转为伸展阶段。
英文摘要:
      The syenogranite in Qinghai Province is located on the east periphery of the Kendekeke deposit in the Qimantag area, East Kunlun Mountains. It consists of alkali feldspar (50%~60%), quartz (20%~30%), plagioclase (10%~20%), and biotite and hornblende (1%~5%). The results of LA-ICP-MS zircon U-Pb isotope dating reveal that the syenogranite was formed at 217.9±1.7 Ma (MSWD=0.74, n=20), suggesting the Late Triassic and the same time as the metallogenic age of the iron-polymetallic deposit in Qimantag area. The syenogranite is characterized by high silicon (SiO2=74.62%~75.28%), high alkali (K2O + Na2O=8.81%~8.95%), and fairly high ratio of FeOT/MgO (18.02~31.48). The trace element and REE compositions show the features of significant negative Eu anomalies (δEu=0.04~0.05), enrichment of Rb, Th, U, K, Ga, and depletion of Sr, Ba, Ta, P, Ti. The geochemical characteristics indicate that the syenogranite belongs to metaluminous-weakly peraluminous A-type granite. The εHf(t) values of syenogranite vary from 2.0 to 12.4 with the two-stage model ages being tDM2 of 1 126~458 Ma. It is held that the source region of syenogranite probably had a mixture with the mantle and ancient crust, which provided abundant materials for the iron-polymetallic mineralization in this area. In the discrimination diagrams of A-type granite, the syenogranite falls into A2-type granites, which suggests that it was formed in an extensional tectonic regime after the orogenic process. All these characteristics display a transition of the Late Variscan-Indosinian orogenic cycle from the epi-orogenic stage to the extensional tectonic regime in Qimantag area in the late Triassic.
张明玉,丰成友,王辉,李大新,瞿泓滢,刘建楠,周建厚,2018,东昆仑祁漫塔格地区晚三叠世正长花岗岩岩石成因及构造意义[J].岩石矿物学杂志,(2):197~210.
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