东昆仑东段香加南山花岗岩基中加鲁河中基性岩体形成时代、成因及其地质意义

发布时间：2018-11-10 18:29

【摘要】：东昆仑东段香加南山花岗岩基中加鲁河中基性岩体主要岩石类型包括角闪辉长岩和石英闪长岩。LA-ICP-MS锆石U-Pb同位素定年结果显示加鲁河中基性岩体的结晶年龄为220 Ma。岩体SiO_2含量较低,为47.91%~58.92%,Al_2O_3含量为15.54%~18.35%,Na2O为1.70%~3.34%,K_2O为0.58%~1.92%,Na_2O/K_2O比值为1.34~2.93,平均1.92,MgO含量为3.69%~8.24%,Mg~#为46~61,铝饱和指数A/CNK介于0.70~0.90之间,主体属于准铝质中钾钙碱性系列。岩体富集轻稀土元素,亏损重稀土元素,具明显的Eu负异常(δEu=0.40~0.59);微量元素富集Rb、Th、Ba等大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE)。岩石学和地球化学研究显示岩体在地壳深部和浅部经历了两次岩浆混合作用。在深部,幔源岩浆底侵作用使下地壳部分熔融形成长英质岩浆,两种岩浆不同比例混合,经过化学扩散均一化,从而具有相似的同位素特征和岩石地球化学特征。在地壳浅部,经深部混合的岩浆注入花岗质岩浆,岩浆边部同花岗岩完全混合形成加鲁河岩体中石英闪长岩,不完全混合则形成暗色微粒包体。对加鲁河中基性岩体研究表明,东昆仑东段在晚三叠世处于古特提斯演化的后碰撞阶段,在这一时期存在岩浆底侵事件。
[Abstract]:The main rock types of the central Jialu River basic rock body in the Xiangganshan granite base in the eastern part of East Kunlun Mountains include hornblende gabbro and quartz diorite. LA-ICP-MS zircon U-Pb isotopic dating results show that the Jialu River middle basic rock body Age of crystallization 220 Ma. The content of SiO_2 in rock mass is relatively low, 47.91 and 58.92. The content of Al2O3 is 15.54 / 18.35 and the value of Na _ 2O is 1.70 and 3.34. The K2O value is 0.58 and 1.92 respectively. The ratio of Na _ 2O / K _ 2O is 1.342.93, The average content of 1.92% MgO is 3.69 and the content of MgO is 461.The saturation index of aluminum (A/CNK) is between 0.70 and 0.90, and the main body belongs to the calc-alkaline series of potassium in quasi-aluminite. The rock mass is enriched in light rare earth elements, depleted in heavy rare earth elements, with obvious Eu negative anomaly (未 Eu=0.40~0.59), and enriched in Rb,Th,Ba and other large ion lithophile elements, such as (LILE), which is depleted in high field strength elements such as Nb,Ta,Ti. Petrological and geochemical studies show that the rock mass experienced two magmatic mixing processes in the deep and shallow crust. In the deep part of the lower crust, the mantle magma underplating causes the partial melting of the lower crust to form felsic magma. The two magmas are mixed in different proportions and are chemically diffused and homogenized, thus having similar isotopic and petrogeochemical characteristics. In shallow crust, magma is injected into granitic magma through deep mixed magma, magma edge is completely mixed with granite to form quartz diorite in Kaluhe rock body, while incomplete mixing forms dark color microparticle inclusion. The study of the basic rock bodies in the middle Kalu River shows that the eastern part of East Kunlun is in the post-collision stage of PaleoTethys evolution in the late Triassic, and there are magmatic underplating events in this period.
【作者单位】：长安大学地球科学与资源学院西部矿产资源与地质工程教育部重点实验室国土资源部岩浆作用与找矿重点实验室;南阳理工学院土木工程学院;中国地质大学(北京)地球科学与资源学院;山西师范大学地理科学学院;
【基金】：国家自然科学基金(41472191、41502191、41172186、40972136) 中央高校基本科研业务费专项资金(310827161002、310827161006) 青海省国土资源厅-中国铝业公司公益性区域地质矿产调查基金(200801)联合资助
【分类号】：P588.12

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