藏南色岗辉绿岩墙群年代学及成因研究

发布时间：2019-02-16 00:55

【摘要】：岩浆岩对于间接研究构造背景和大地动力学机制具有重要意义。受印度板块向欧亚大陆碰撞造山作用的影响,藏南地区的岩浆活动极为强烈,但在靠近主中央逆冲断裂带(MCT)的特提斯-喜马拉雅锑金成矿带内,目前报道的岩浆岩出露则相对较少。扎西康铅锌多金属矿整装勘查区正是位于该成矿带东部,在勘查区内发现众多的侵入岩浆岩体或岩脉/墙,具有典型的双峰式岩浆岩特征。对区内的色岗辉绿岩墙群进行了锆石U-Pb年代学及元素地球化学研究,结果表明这些铁镁质岩浆岩形成于早白垩世(138~134 Ma),并显示较高的TiO_2含量和Nb/Y比值,极度富集轻稀土元素(LREEs)和不相容元素,与洋岛玄武岩(OIB)的特征非常一致,为较大规模伸展构造背景下的产物。色岗辉绿岩群应为软流圈地幔部分熔融产生的基性岩浆在上升过程中受地层围岩不同程度混染下的产物,大地动力学机制可能与古Kerguelen地幔柱的活动相关。该项研究有助于解读藏南地区中生代的构造-岩浆作用及形成机理。
[Abstract]:Magmatic rock plays an important role in the indirect study of tectonic setting and geodynamic mechanism. Influenced by the collision orogeny of Indian plate to Eurasia, the magmatic activity in southern Tibet is extremely strong, but in the Tethys Himalayan antimony gold metallogenic belt near the (MCT) of the main central thrust fault zone, At present, relatively few magmatic outbursts have been reported. The integrated exploration area of Zaxikang Pb-Zn polymetallic ore deposit is located in the eastern part of the metallogenic belt. Many intrusive magmatic bodies or veins / walls have been found in the exploration area, which is characterized by typical bimodal magmatic rocks. Zircon U-Pb geochronology and elemental geochemistry of the Xiegang diabase dike group in this area were studied. The results show that these ferromagnesian magmatic rocks were formed in the early Cretaceous (138Cretaceous) and show high TiO_2 content and Nb/Y ratio. The extreme enrichment of light rare earth elements (LREEs) and incompatible elements is very consistent with the characteristics of oceanic basalt (OIB) and is the product of a large scale extensional tectonic setting. The xiegang diabase group should be the product of the basic magma caused by partial melting of the soft mantle during the rising process, and the geodynamic mechanism may be related to the activity of the paleo-Kerguelen mantle plume. This study is helpful to understand the Mesozoic tectonic-magmatism and its formation mechanism in southern Tibet.
【作者单位】：中国地质调查局成都地质矿产研究所;中国地质科学院矿产综合利用研究所;
【基金】：国家自然科学基金青年基金(41202067) 中国地质调查局区域地质矿产调查项目(121201010000150016-05)
【分类号】：P597.3;P618.2

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