大兴安岭北段雅尔根楚Ⅰ型花岗岩年代学、岩石地球化学及其地球动力学意义  

Geochronology and Geochemistry of the Yaergenchu I Type Granites in Northern Da Hinggan Range and Its Geodynamic Implications

作　　者：徐久磊[1] 郑常青[1] 施璐[1] 李娟[1] 崔芳华[1] 高源[1] 张行行[1] 高峰[1] 

机构地区：[1]吉林大学地球科学学院,长春130061

出　　处：《地质学报》2013年第9期1311-1323,共13页Acta Geologica Sinica

基　　金：中国地质调查局地质调查项目(1212011120654);国土资源部公益性行业科研专项经费项目(201011083)共同资助的成果

摘　　要：对内蒙古大兴安岭北段雅尔根楚花岗岩岩体岩相学研究表明,该花岗岩岩体主要岩性组合为正长花岗岩和花岗质糜棱岩,应用锆石U-Pb LA-ICP-MS测年方法,测得的3组年龄为226.8±2.2Ma、230.2±1.3Ma和233.6±1.5Ma,表明其岩体侵位时代为晚三叠世。岩石主量元素（XRF）具有富硅、富钾的特征,A/CNK值为0.81~1.10,显示铝弱饱和,相对富集轻稀土元素、亏损重稀土元素,具有Eu负异常,微量元素相对富集大离子亲石元素,亏损高场强元素,显示岛弧性质的花岗岩特征,微量元素特征显示其为I型花岗岩。经过综合研究认为该I型花岗岩可能是在整个伸展环境下,岩石圈地幔压力降低导致地幔上涌,残余的洋壳熔融提供流体注入,从而该岩体发生侵位。The study of the Yaergenchu granites in northern Da Hinggan Range indicates that the granites consist of syenogranite, mylonitized granite in lithology. Analysis of zircon U-Pb LA-ICP-MS dating yielded three concordant ages of 226.8 4- 2.2Ma, 230.2 ~ 1.3Ma and 233.6 ~ 1.5 Ma, indicating intrusive time of the granites is the late Triassic. The chemical analyses （XRF） show that the granites have high SiO2, K20 contents, A/CNK ratios ranging from 0.81 to 1. 10. The REE patterns are characterized by enrichment of LREEs relative to HREEs with negative Eu anomalies in chondrite-normalized REE diagram. The trace elements are relatively enrichment of large ion lithophile elements （LILE）, depletion of high field strength elements （HFSE）. These features are similar to the island arc granites and I type granites. Integrated study shows that these I type granites formed in the whole extensional setting. The decreasing pressure of lithosphere mantle resulted in upwelling of the mantle, and the melted residual oceanic crust provided fluid, thus causing the emplacement of this pluton.

关 键 词：大兴安岭 雅尔根楚 晚三叠世 Ⅰ型花岗岩 伸展环境 

分 类 号：P588.121[天文地球—岩石学]