新疆东准噶尔卡拉麦里地区红柳沟组玄武岩发现及地质意义  

Discovery and Significance of Hongliugou Formation Basalts in Kalamaili,East Junggar,Xinjiang

作　　者：刘阁 杨硕 腾宇翔 靳刘圆 郑海峰 Liu Ge;Yang Shuo;Teng xuxiang;Jin Liuyuan;Zheng Haifeng(Xinjiang Institute of Geological Survey,Urumqi,Xinjiang,830000,China;Xinjiang Mining Investment(Group)Co.,Ltd,Urumqi,Xinjiang,830000,China)

机构地区：[1]新疆维吾尔自治区地质调查院,新疆乌鲁木齐830000 [2]新疆地矿投资(集团)有限责任公司,新疆乌鲁木齐830000

出　　处：《新疆地质》2023年第2期133-140,共8页Xinjiang Geology

基　　金：新疆1∶25万北山煤窑幅区调修测项目和新疆区域地质调查片区总结与服务产品开发(DD20160345-04)共同资助。

摘　　要：新疆北部东准噶尔卡拉麦里地区红柳沟组中发现玄武岩,测年结果显示,红柳沟组玄武安山岩形成于(428.1±2.5)Ma,属中志留世晚期。岩石地球化学特征表明,红柳沟组玄武安山岩Nb含量13.7×10^(-6)~14.8×10^(-6),Al2O3含量17.62%~17.76%,均值17.71%,具富Nb玄武岩特征,为钙碱性系列。该岩石轻重稀土元素分馏较明显,分布模式为无明显铕异常的右倾曲线,微量元素表现出不同程度富集轻稀土元素和大离子亲石元素特征,具弱的Nb,Ta,Ti负异常。红柳沟组玄武安山岩原岩可能为具陆内弧后盆地玄武岩性质的岩石,源区受到俯冲板片熔体改造,岩浆作用期间发生一定程度混染。结合前人研究,认为红柳沟组玄武岩安山可能形成于碰撞造山后的板内伸展环境,代表北部卡拉麦里洋盆初期陆内拉张阶段。The basalts found in Hongliugou formation in kalamaili area,eastern Junggar,Northern Xinjiang.In this study,LA-ICP-MS zircon dating for Hongliugou formation basaltic andesite has obtained U-Pb age of(428.1±2.5)Ma.indicating formating during the late middle Silurian.Lithogeochemical characteristics show that the basaltic andesite in Kalamaili area are characterized by obvious enrichment of Nb and Al2O3,with the values of Nb being13.7×10^(-6)~14.8×10^(-6) and Al2O3being 17.62%~17.76%,averaging 17.71%,suggesting Nb-rich basalt of calc alkaline series.The REE patterns are of the LREE enrichmengt with no Eu anomalies,suggesting obvious fractionation.On primitive mantle-normalized trace element diagrams,the basalts display different degrees of enrichment of LIFEs(e.g.,Rb,U,K),weakly depletion of HFSE(Nb,Ta,Ti).Therefore,the protoliths of the Hongliugou basalts could be interpreted to be derived from intraconti-nental BABB with the origin reconstructed by subduction-related crust and assimilation contamination during magma-tism.Combined with previous studies,the Hongliugou basalts may be formed in the plate extensional setting after the collision.which may represent the stage of Karamaili ocean intracontinental initial extension.

关 键 词：东准噶尔 卡拉麦里 富Nb玄武岩 弧后盆地 中志留世 

分 类 号：P619.221[天文地球—矿床学]