西藏玛依岗日地区辉长岩地球化学特征及其构造意义

发布时间：2018-05-19 19:22

本文选题：玛依岗日 + 辉长岩　；参考：《现代地质》2017年02期

【摘要】：西藏玛依岗日地区侵入脉岩为辉长岩,通过采集辉长岩样品,观察显微照片,并进行主量元素、微量元素和稀土元素含量测试。结果表明:Na_2O与K_2O含量变化范围不大,全碱(K_2O+Na_2O)含量为1.86%~4.11%,样品K_2O/Na_2O值的范围为0.25~0.66。岩石富集轻稀土、亏损重稀土,铕无正负异常。总体富集Hf、La、Nd、Ti,亏损P、Yb、Y等元素。地球化学特征表明其形成于陆内裂谷环境,岩浆来源于富集地幔,受到硅铝质地壳物质的混染。结合辉长岩围岩为晚石炭世—早二叠世浅变质岩系以及早二叠世晚期之后的地层中不发育岩墙群的事实,而且根据前人对藏北羌塘南部地区基性岩墙群为晚石炭世—早二叠世的年龄约束,推断研究区内南北向辉长岩可能为古特提斯洋拉张初期的产物。
[Abstract]:The intrusive dikes in Mayi Gangri area, Tibet are gabbro. The samples of gabbro are collected, the microscopic photographs are observed, and the contents of principal elements, trace elements and rare earth elements are tested. The results showed that the content of K2O and K2O changed little, the content of K _ 2O and K _ 2O was 1.86 and 4.11, and the K_2O/Na_2O value of the sample was 0.25 ~ 0.66. Rock enriched light rare earth, depleted heavy rare earth, europium has no positive and negative anomalies. The total enrichment of HfN LaNdN Ti and the depletion of elements such as Pu Yb Y and so on. The geochemical characteristics indicate that the magma originated from the enriched mantle and was mixed by silica-aluminum crust material. Combined with the fact that the surrounding rock of gabbro is the late Carboniferous to early Permian shallow metamorphic rock series and the undeveloped rock dike group in the strata after the late early Permian. Furthermore, according to the age constraint that the basic rock dike group in the southern Qiangtang area of northern Tibet is late Carboniferous to early Permian, it is inferred that the north-south gabbro in the study area may be the product of the early PaleoTethys extension.
【作者单位】：北京探矿工程研究所;中国地质大学(北京)地球科学与资源学院;
【基金】：中国地质调查局区域地质调查项目(1212011086062,1212011221115)
【分类号】：P588.124

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