ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    新疆阿尔泰大东沟乌雷库-克朗岩体LAICPMS锆石UPb年龄、地球化学特征及其地质意义

    LA-ICP-MS Zircon U-Pb Age,Geochemistry of the Wuleiku-Kelang Pluton from the Dadonggou Area of Altay in Xinjiang and Its Tectonic Implications

    • 摘要: 乌雷库-克朗岩体正长花岗岩和花岗闪长岩中锆石的LA-ICP-MS U-Pb年龄分别为(404±2.7)Ma(MSWD=0.24)和(410.5±2.1)Ma(MSWD=0.3),属早泥盆世早期岩浆活动的产物,为阿尔泰造山带在400Ma有一次强烈的岩浆侵入活动提供了新依据,限定了康布铁堡组时代早于410Ma。岩石具高硅(72.22%~78.33%)、高碱(5.76%~9.24%)、高Al2O3(12.07%~14.30%)、低P2O5(0.02%~0.1%)和FeO+MgO(0.33%~3.50%),高A/NCK值(1.04~1.47),低CaO/Na2O值(均值<0.3)特点,属过铝质花岗岩。富Rb、Th、U、K,贫Ba、Sr、P、Ti,高场强元素Nb、Ta的含量偏低。亲Fe元素(V、Co)的含量低,也指示岩体分异演化程度高。岩石的轻稀土富集,并具有Eu(δEu=0.05~0.67)的显著负异常,显示了岛弧花岗岩的地球化学特征。结合阿尔泰的区域地质背景综合分析,推测岩体形成于活动大陆边缘环境,由泥质沉积物和少量变质杂砂岩组成的地壳物质部分熔融形成,源区残留有富钙的斜长石、钛铁矿和磷灰石等。

       

      Abstract: LA-ICP-MS zircon U-Pb ages and whole rock geochemical data about the Wuleiku-Kelang pluton from the Dadonggou area of Altay in Xinjiang have been reported in this paper.Zircons from granodiorite and syenogranite have well-defined oscillatory zoning, which yielded the mean 206Pb/238U ages of (404±2.7)Ma (MSWD=0.24) and (410.5±2.1)Ma (MSWD=0.3), respectively, indicating that the Kangbutiebao Formation was formed prior to 410Ma.The granitoid rocks have high SiO2 (ranging from 72.22% to 78.33%), total alkali (Na2O+K2O) (changing from 5.76% to 9.24%) and Al2O3 (varying from 12.07% to 14.30%), and low P2O5 (ranging from 0.02% to 0.1%) and MgO+FeO (changing from 0.33% to 3.50%).In addition, they are characterized by high A/CNK values (varying from 1.04 to 1.47) and low CaO/Na2O ratios (average ratios are less than 0.3), which have been defined as calc-alkaline peraluminious granitoid rocks.These rocks have obvious negative anomalies of Ba, Sr, P, Ti, Nb,Ta and Eu (δEu=0.05~0.67) and obvious enrichment of LREE, Rb, Th, U and K, resembling that these granitoid rocks were formed in the volcano arc settings.Combined with the tectonic evolution of the southern margin of Altay, it's suggested that these granitoid rocks were generated by partial melting of the crust in an active continental margin, with the residues of plagioclase, ilmenite and apatite.

       

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