西藏羌塘南缘青草山北花岗闪长岩锆石U-Pb年代学、地球化学特征及其成矿意义

发布时间：2018-07-13 11:52

【摘要】：青草山北花岗闪长岩体位于班公湖-怒江缝合带北侧、羌塘陆块南缘,呈岩脉、岩株状与晚二叠世龙格组碳酸盐岩呈侵入接触。本文对该花岗闪长岩的锆石进行了LA-ICP-MS U-Pb年代学和岩石地球化学研究,其岩浆锆石U-Pb年龄为154.8±1.2Ma(MSWD=1.7),属晚侏罗世,与热那错埃达克质英安岩年龄高度一致,岩石地球化学特征显示,青草山北花岗闪长岩属于准铝质、高钾钙碱性系列,富集轻稀土元素、大离子亲石元素,亏损重稀土元素、高场强元素,具弱Eu负异常,显示出典型岛弧岩浆岩特征;锆石原位微量元素分析表明,锆石总体富集重稀土,相对亏损轻稀土,在锆石Nb/Ta-Y图解中样品点落入金伯利岩区域,而在岩石地球化学构造环境判别图解中,样品点同样指示其可能来源于幔源岩浆。青草山北花岗闪长岩班公湖-怒江洋壳晚侏罗世北向俯冲到一定深度后,俯冲洋壳发生部分熔融,形成的岩浆在上升的过程中与地幔楔发生混染,其中,部分岩浆在侵位的过程中形成中酸性的花岗闪长质岩浆房,部分岩浆则喷出地表,形成热那错组英安岩。
[Abstract]:The northern granite diorite rock is located on the north side of the ban Gong Lake Nu River suture zone, the southern margin of the Qiangtang land block, and the rock veins are in contact with the carbonate rocks of the Late Permian longg group. The zircon of the granodiorite was studied by LA-ICP-MS U-Pb chronology and rock geochemistry, and the U-Pb age of the magma zircon was 154.8 + 1.2Ma (MSWD =1.7), which belongs to the late Jurassic, is the same as that of the hot diacinite age. The rock geochemical characteristics show that the granodiorite in the north of Qinghai province belongs to the quasi aluminum, high potassium calc alkaline series, rich in light rare earth elements, large ion stone elements, heavy rare earth elements, high field strong elements and weak Eu negative anomalies, showing typical island arc magma. The zircon in situ trace element analysis shows that the zircon is enriched with heavy rare earth and relatively light rare-earth, and the sample point in the zircon Nb/Ta-Y diagram falls into the Kimberley region, and in the diagrammatic diagram of the geochemical tectonic environment of the rock, the sample point also indicates that it may come from the mantle derived magma. After the late Jurassic of the Nu River oceanic crust subducted to a certain depth, the subduction oceanic crust partially melted, and the magma formed in the ascending process was mixed with the mantle wedge. Some of the magma formed a medium acidic granodiorite magma chamber in the emplacement process, and some magma erupted out of the surface to form the hot dianite rock.
【作者单位】：成都理工大学;中石化西南油气分公司勘探开发研究院;
【基金】：国家自然科学基金资助项目(批准号:40173022)的成果
【分类号】：P588.12;P597.3;P612

【相似文献】