大兴安岭北部斯木科地区晚侏罗世斑状正长花岗岩年代学、地球化学特征及其成因  

Chronology,geochemical characteristics and petrogenesis of Late Jurassic porphyritic syenogranite in Simuke area,northern Da Hinggan Mountains

作　　者：刘世伟[1] 孙国胜[1] 王清海[2] 晋瑞香 何欣[1] 刘承先[1] LIU Shi-wei SUN Guo-sheng WANG Qing-hai JIN Rui-xiang HE Xin LIU Cheng-xian(College of Earth Sciences, Jilin University, Changchun 130061, China International Centre for Geoscience Research and Education in Northeast Asia, Jilin University, Changchun 130026, China)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]吉林大学东北亚国际地学研究与教学中心,长春130026

出　　处：《世界地质》2017年第2期402-412,共11页World Geology

基　　金：基金项目:内蒙古自治区鄂伦春自治旗马布拉其汗等三幅1:5万区域矿产地质调查(NMKD2014-38)

摘　　要：对斯木科斑状花岗岩进行了锆石LA-ICP-MS U-Pb年代学及岩石地球化学特征研究。测年结果显示,该岩体年龄为(144±0.85)Ma,为晚侏罗世。岩石地球化学分析表明,斯木科斑状正长花岗岩为准铝质-过铝质岩石,属于高钾钙碱性系列;稀土元素丰度总量较高,轻稀土富集且轻重稀土分馏较明显[(La_N/Yb_N=3.15~6.63)],表现为"右倾型"的稀土配分模式,岩石具有轻度的负Eu异常(δEu=0.54~0.66);微量元素以相对富集Rb、K等大离子亲石元素,而相对亏损Nb、Ta、P、Ti等高场强元素为特征。斯木科斑状正长花岗岩具有高分异I型花岗岩的特征,来源于地壳中火山岩的部分熔融。对Nb-Y构造环境判别图解及构造环境讨论,结合其所具有的I型花岗岩的特征,斯木科斑状正长花岗岩应为伸展构造体制下的产物,形成于造山后伸展构造环境。LA-ICP-MS zircon U-Pb dating and geochemical data of Simuke porphyritic syenogranite have been studied.The results indicate that the diagenetic age of porphyritic syenogranite is （144±0.85）Ma,belonging to Late Jurassic.The geochemical study shows that the porphyritic syenogranite belongs to high-K calc-alkaline series and high aluminum rocks. The rare earth elements are characterized by rich light rare earth elements and significant fractionation of LREE and HREE[（La/Yb）N=3.15-6.63].The REE distribution patterns are right deviated, with weak negative europium anomalies（δEu=0.54-0.66）. For trace elements, the porphyritic syenogranites are enriched in Rb and K,but depleted in Nb,Ta,P and Ti.The porphyritic granite in Simuke area is high differentiation I type granite,derived from partial melting of basic volcanic rocks in the crust.Based on Nb-Y tectonic environment discrimination diagram and tectonic environment,combined with the characteristic of I type granite,the porphyritic granite in Simuke area should be the product of extensional tectonic system and it is formed in post-orogenic extensional tectonic environment.

关 键 词：晚侏罗世 锆石U-PB年龄 地球化学 岩石成因 斑状正长花岗岩 斯木科 大兴安岭 

分 类 号：P597[天文地球—地球化学] P595[天文地球—地质学]