【摘要】 东昆仑出露大面积的中酸性侵入岩,为研究大陆地壳生长提供了天然实验室。该区古特斯时期花岗岩形成的构造背景及其深部演化过程一直存在争议,本文通过对东昆仑扎玛休玛地区出露的正长花岗岩开展岩相学、锆石U-Pb定年、Hf同位素及地球化学研究,以期限定其形成时代,探讨岩石成因,为解决上述问题提供新依据。正长花岗岩由斜长石,碱性长石,石英,黑云母,少量角闪石等组成,LA-ICP-MS锆石U-Pb年龄为240.3±1.8Ma,形成于中三叠世;岩石地球化学结果富硅（SiO₂=70.36%～71.20%）,相对富碱,Na₂O+K₂O含量为7.52%～7.89%,Al₂O₃含量为14.06%～14.18%,TiO₂和MgO含量低,富集大离子亲石元素Rb、Th等,相对亏损Nb、Ta、Ti等高场强元素特征,岩石属于高钾钙碱性准铝质-弱过铝质Ⅰ型花岗岩;ε_Hf（t）值介于-4.1到+2.3之间,二阶段Hf模式年龄T_DM2为1126～1536 Ma,暗示正长花岗岩源于中元古古老地壳熔融。综合分析认为扎玛休玛正长花岗岩形成于活动大陆边缘环境,是东昆仑古特提斯洋由俯冲向碰撞转换阶段的产物。更多还原

【Abstract】 East Kunlun hosts large-sized intermediate-acid intrusive rocks, providing a natural laboratory for the study of continental crust growth. However, the tectonic setting of granite formation and the evolution processes of Paleo-Tethys belt of East Kunlun remains controversial. In this paper, we carried out a detailed investigation on the Zhamaxiuma syenogranite from the eastern segment of East Kunlun using zircon U-Pb dating, whole rock geochemistry and Hf isotopes in order to identify the formation time and petrogenesis of rocks, and provide basis data for the evolution of regional tectonics. Syenogranite consists mainly of plagioclase, alkaline feldspar, quartz, biotite, with minor amount of hornblende. Zircon U-Pb dating yields an age of 240.3±1.8 Ma, indicating its emplacement in Middle Triassic. The syenogranite is geochemically characterized by high SiO₂（70.36%～71.20%） and Al₂O₃（14.06%～14.18%）, relatively rich in alkali with Na₂O+K₂O（7.52%～7.89%）, low TiO₂ and MgO, enriched in large ion lithophilic elements Rb, Ba, Th, etc, depleted high field strength elements such as Nb, Ta, Ti, etc. The rock belongs to high K Ca-alkaline and metaluminus-weak peraluminous I-type granite. ε_Hf（t） values range from-4.1 to +2.3, and T_DM2 ages between 1126 Ma and 1536 Ma,indicating that the syenogranite originated from partial melting of Middle Proterozoic crustal materials. The integrated analyses show that the syenogranite probably formed in the active continental margin and was the product of transformation from subduction of paleo-Tethys Ocean in East Kunlun to collision.更多还原