大兴安岭中段扎赉特旗地区晚侏罗世花岗岩地球化学特征及构造环境  

Geochemical characteristics and tectonic setting of Late Jurassic granites in the Jalaid Banner,central Daxing′anling

作　　者：王春宇 丁加鹏 徐前玮 张涛 Wang Chunyu;Ding Jiapeng;Xu Qianwei;Zhang Tao(School of Mining Engineering,Heilongjiang University of Science and Technology,Harbin 150090,Heilongjiang,China)

机构地区：[1]黑龙江科技大学矿业工程学院,黑龙江哈尔滨150090

出　　处：《地质学刊》2024年第4期369-378,共10页Journal of Geology

基　　金：国家自然科学基金项目“深俯冲陆壳折返深熔机制及其与同碰撞花岗岩的成因关系研究:以柴北缘超高压变质带为例”(42372247)。

摘　　要：为深入探讨大兴安岭中段中生代构造环境,对扎赉特旗格吉格吐山花岗岩开展岩石学、锆石U-Pb年代学、岩石地球化学研究。结果表明:花岗岩形成年代为(161.8±0.9)Ma,属于晚侏罗世早期;铝饱和指数(A/CNK)为1.07~1.23,属于高钾钙碱性的I型花岗岩;轻、重稀土分馏,Eu负异常,Rb、Th、K、Zr等大离子亲石元素富集,Nb、Ta、Ti等高场强元素亏损;花岗岩来源于下地壳玄武质岩石的部分熔融,形成于蒙古—鄂霍茨克洋闭合过程中后碰撞阶段的构造环境;蒙古—鄂霍茨克洋在大兴安岭中段的闭合应早于晚侏罗世早期。研究结果可为深入开展区内中生代岩浆构造演化提供参考。To further investigate the Mesozoic tectonic setting of the central Daxing′anling region,petrological,zircon U-Pb geochronological,and geochemical studies were conducted on the granites of the Gejigetushan area in Jalaid Banner.The results indicate that the granites formed at(161.8±0.9)Ma,corresponding to the early stage of the Late Jurassic.The aluminum saturation index(A/CNK)ranges from 1.07 to 1.23,categorizing the granites as high-K calc-alkaline I-type granites.The rocks display fractionation between light and heavy rare earth elements,negative Eu anomalies,enrichment in large ion lithophile elements(Rb,Th,K,Zr),and depletion in high field strength elements(Nb,Ta,Ti).The granites are derived from partial melting of basaltic rocks in the lower crust and formed in a post-collisional tectonic setting during the closure of the Mongol-Okhotsk Ocean.The closure of the Mongol-Okhotsk Ocean in the central Daxing′anling region likely occurred earlier than the early Late Jurassic.These findings provide valuable references for further studies on the Mesozoic magmatic and tectonic evolution of the region.

关 键 词：锆石U-PB测年 晚侏罗世 构造环境 大兴安岭中段 扎赉特旗 

分 类 号：P595[天文地球—地球化学] P548[天文地球—地质学]