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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    东昆仑西段拉陵灶火沟地区变质侵入体的年代学与地球化学特征及其地质意义

    Chronological and Geochemical Characteristics of Metamorphic Intrusions in the Lalingzaohuogou Area of the Western Section of the East Kunlun Mountains

    • 摘要: 东昆仑西段拉陵灶火沟地区古元古界金水口群地层中新解体出一套花岗质变质侵入体,岩性以眼球状黑云二长花岗岩为主,笔者通过岩石学、锆石LA-MC-ICP-MS U-Pb同位素年代学和岩石地球化学等方面入手研究,探讨了这套变质侵入体的岩石成因、形成时代、大地构造意义。岩石地球化学研究表明,这套变质侵入体岩石具高Si(SiO2=65.52%~75.31%)、全碱含量高(K2O+Na2O=6.82%~8.81%)、Al2O3含量偏高(12.17%~14.22%)、δ=1.89~2.54,属于高钾钙碱性系列,A/CNK值为1.37~1.68,显示为S型过铝质花岗岩特征;稀土配分曲线呈现轻稀土元素相对富集的右倾分布特征,具明显的Eu负异常(δEu=0.173~0.52);洋脊花岗岩标准化微量元素蛛网图显示为右倾型,Nb、Ta亏损和 Rb、K、Th富集。岩石CaO/Na2O值为0.35~0.91,平均为0.61;Rb/Sr值较高,为0.6~2.83,平均为1.77,显示区内花岗岩为上部地壳源区特征,可能为含少量泥质成分的砂屑沉积岩熔融形成。这套变质侵入体LA-MC-ICP-MS锆石U-Pb加权年龄(865.8±3.9)Ma(MSWD=0.24), 属新元古代早期。结合东昆仑地区前人年代学及区域构造演化研究,通过文中构造判别认识, 认为拉陵灶火沟这套岩体形成于同碰撞的构造环境,是东昆仑造山带西段地区存在新元古代早期大陆汇聚碰撞环境下的岩浆活动。综合资料认为, 东昆仑地区在新元古代早期存在一次陆陆碰撞拼合事件,与全球 Rodinia超大陆的形成基本吻合,也就是说东昆仑拉陵灶火沟地区的变质侵入体为Rodinia超大陆聚合中在东昆仑陆块中岩浆活动的响应。

       

      Abstract: In the Laling Zao Huo Gou area of the western segment of the Eastern Kunlun Mountains, a newly identified set of granitic metamorphic intrusions was discovered within the Jinsui Kou Group of the Paleoproterozoic. The lithology is predominantly composed of eye-shaped hornblende monzogranite. Through studies in petrology, zircon LA-MC-ICP-MS U-Pb isotopic dating, and petrogeochemistry, the author explores the petrogenesis, formation age, and tectonic significance of these metamorphic intrusions. Petrogeochemical studies indicate that these metamorphic intrusive rocks exhibit high silica content (SiO2=65.52%–75.31%), high total alkali content (K2O+Na2O=6.82%–8.81%), elevated Al2O3 content (12.17%–14.22%), and a δ value of 1.89–2.54, classifying them as the high-K calc-alkaline series with an A/CNK ratio of 1.37–1.68, displaying characteristics of S-type peraluminous granite. The rare earth element (REE) distribution pattern shows a right-leaning trend with relative enrichment of light rare earth elements and a distinct negative Eu anomaly (δEu=0.173–0.52). The mid-ocean ridge granite-normalized trace element spider diagram reveals a right-leaning trend, with deficits in Nb and Ta and enrichments in Rb, K, and Th. The CaO/Na2O ratio of the rocks ranges from 0.35 to 0.91, averaging 0.61, while the Rb/Sr ratio is relatively high, ranging from 0.6 to 2.83, averaging 1.77, indicating that the granites in the region are derived from the upper crustal source, likely formed by the melting of sandy clastic sedimentary rocks with minor mud components. The LA-MC-ICP-MS zircon U-Pb weighted age of this metamorphic intrusive suite is (865.8±3.9) Ma (MSWD=0.24), belonging to the early Neoproterozoic. Based on previous studies of chronology and regional tectonic evolution in the eastern Kunlun region, and through the tectonic discrimination criteria discussed in the paper, it is concluded that the Laling Zao Hui Gou rock suite formed in a post-collisional tectonic setting, representing magmatic activity under the early Neoproterozoic continental convergence and collision environment in the western segment of the eastern Kunlun orogenic belt. Based on comprehensive data, it is believed that there was a land collision and assembly event in the early Neoproterozoic in the East Kunlun region, which is basically consistent with the formation of the global Rodinia supercontinent. In other words, the metamorphic intrusion in the Lalingzaohuogou area of the East Kunlun is a response to magmatic activity in the East Kunlun block during the aggregation of the Rodinia supercontinent.

       

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