摘要
对西秦岭北部花岗质岩体的岩石学、地球化学研究表明,花岗岩体的岩性主体为花岗闪长岩-二长花岗岩,属高钾钙碱系列,少数为钙碱系列;LA-ICPMS锆石U-Pb测年表明其形成时代介于216～264Ma,为中二叠世末至晚三叠世。江里沟、阿夷山和中川岩体属弱过铝质花岗岩(ACNK>1.05),温泉岩体和德乌鲁岩体属准铝和弱过铝质花岗岩(ACNK=0.95～1.05);花岗岩具有埃达克岩(Sr>400×10-6,Yb<2×10-6)或喜马拉雅型花岗岩(Sr<400×10-6,Yb>2×10-6)的地球化学特征,或两者兼而有之。其中,江里沟、德乌鲁和中川岩体具喜马拉雅型花岗岩的地球化学特点,阿夷山岩体具埃达克岩的地球化学特点,温泉岩体是两者兼而有之。花岗岩浆起源于下地壳的部分熔融,源岩最有可能是古老的玄武质岩石。西秦岭北部存在埃达克岩和喜马拉雅型花岗岩,说明三叠纪时期存在陆-陆碰撞或陆-陆俯冲导致的地壳加厚,加厚的下地壳的部分熔融以及部分熔融发生深度的不同,形成本区具有埃达克或喜马拉雅型地球化学特点的花岗岩侵入体。埃达克岩和喜马拉雅型花岗岩对寻找金铜矿产具有一定的指导意义。
Based on petrogeochemistry, the samples form intrusions in western Qinling mostly belong to high-K cale-alkalic series with a few scatter to calc-alkalic series. The study results in this essay also show that there exist adakite and Himalaya type granites in the northern edge of Western Qinling, and the Jian- glugou, Ayishan and Zhongchuan intrusions are similar to Himalaya type granite, and Ayishan pluton is similar to adakite based on the content of Sr and Yb. Whereas, the Wenquan intrusion shows both adakite and Himalaya type granite according go geochemical features. The granites of adakite and Himalaly type with low Mg^# may caused by partial melting of basalts in thickened lower crust. On the other hand, the adakite and Himalaya type granitoids in the northern edge of Western Qiling provide the clue to the collision of subduction between the North China Plate and the Yangtze Plate in Trassie period, which lead to the event of crust thickening, and the partial melting of thickened lower eurst in different depth produced adakite or Himalaya type granite. In addition, the adakite or Himalaya type granitoid in northern edge of Western Qinling should be pay more attention to the mineralization of Cu-Au.
出处
《西北地质》
CAS
CSCD
2012年第4期76-82,共7页
Northwestern Geology
基金
国家自然科学基金项目"罗汉寺岩组物质组成研究--对北秦岭古生代俯冲-增生作用的约束"(40972150)
国土资源大调查项目"西北地区基础地质调查成果集成与综合研究"(1212011121137)
