Caledonian intrusive rock body is newly discovered in the Maerzheng region in the south area of East Kunlun. Based on zircon U-Pb dating, the age is determined to be Early Ordovician. The lithology is composed of some tonalite, a few of anorthosite and diorite-porphyry. According to research on petrologic and geochemical characteristics of intrusive rocks, the content of Na2O is much richer than that of K2O in basic and acid rocks, which shows characteristics of rich Na. The content of A12O3 is from 13. 21% to 16. 03% , and increases gradually from basic rocks to acid rocks. The content of A12O3 is higher than the total content of K2O, Na2O, and CaO, showing that the rock belongs to an aluminium saturation type. The rock body is characterized by obvious fractionation of REE, enrichment of LREE, weak nagative Eu anomaly (5Eu values are 0. 61 -0. 94); the rock body is characterized by richment of Ba, Th, Zr and depletion of Nb. The lithologic combinations show the characteristics of representative TTG. Combining with the geotectonic environment map of granite in the Maerzheng region, the intrusive rock body formed as a result of Tethys ocean subduction from south to north in Early Ordovician. The age of Maerzheng Formation in Early-middle Permian is redefined to be Early Ordovician ac- cording to the age of the intrusive rock body and field investigation.%东昆南马尔争地区加里东侵入体为新发现岩体,根据锆石U-Pb测年,其时代为早奥陶世.该岩体岩性主要为英云闪长岩及少量斜长岩、闪长斑岩,通过对该岩体地球化学特征研究发现,在基性岩和酸性岩中Na2O的含量均远大于K2O的含量,显示富Na特征.Al2O3含量为13.21％～16.03％,从基性岩到酸性岩含量逐渐增高,显示基性岩中富Mg特征.w( Al2O3)＞w( K2O+ Na2O+ CaO),属铝过饱和的岩石类型.轻稀土富集、轻重稀土分异现象明显,显示出中等程度的负铕异常(δEu =0.61～0.94)；微量元素以富集Ba、Th、Zr等元素、亏损Nb等元素为特征.岩石组合类型为较典型的TTG特征.结合花岗岩构造环境判别图解可知,该岩体是古特提斯洋在早奥陶世裂解而由南向北俯冲下形成的岛弧环境下的产物.结合侵入体的时代及野外路线观察,对早—中二叠世马尔争组局部重新进行了厘定,其时代为早奥陶世.
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