西藏1:5万改则东地区4幅区域地质调查主要成果

    Achievements of 1:50 000 regional geological survey in the east of Gaize area,Tibet

    • 摘要: 围绕加强重要成矿带基础地质调查的要求,开展了西藏改则东地区1:5万区域地质调查工作,以新的填图方法和现代地质成矿理论为指导,从基础地质调查入手,结合地质、物探、化探及遥感综合信息,查明了区域地层、岩石、构造特征和成矿地质条件。以岩石地层单位为基础,注重岩石地层单位与生物地层单位的对应关系,有条件地利用旋回地层、事件地层等多重地层划分和对比,重新厘定了测区中生代、新生代地层的形成时代和地层序列,并使用非正式的填图单元,系统查明了区域地层、岩石、构造及成矿地质条件。系统总结了日干配错组基本层序和物质组成,并将其进一步划分为2个段; 测区内木嘎岗日群表现出沉积混杂堆积特征; 重新解体仲岗洋岛岩组并建立了洋岛火山-沉积建造序列模式; 测区内榴辉岩及唢呐湖组泥灰岩中光叶山栎Quercus pseudosemicarpifolia的首次发现分别为班公湖—怒江洋构造演化、青藏高原隆升提供了重要的资料; 测区内地层划分出3个构造层和6个主要构造事件; 圈定2个成矿远景区和1个找矿靶区。总结出测区班怒带构造演化经历班公湖—怒江洋扩张、形成(约242 Ma)、班公湖—怒江洋俯冲(早侏罗世)和高压变质岩折返((193.8±1.5) Ma)、班公湖—怒江洋闭合(110~85 Ma)和碰撞造山4个演化阶段。

       

      Abstract: Based on the regional geological survey standard and technical requirements for major mineral zone,the east Gaize 1:50 000 regional geological survey project was carried out. The regional stratigraphic units, rocks, structure characters and metallogenic conditions were investigated from basic geology survey under the guidance of new mapping and modern metallogenic theory. Based on lithostratigraphic unit,focusing on the correspondence between litho-stratigraphic unit and bio-stratigraphic unit, and effectively utilizing multiple stratigraphic classification and correlation,such as cyclic stratigraphy and stratigraphy, the formation age and stratigraphic sequence of Mesozoic and Cenozonic strata were defined. It systematically summarized the basic sequence and constituent compositions and divided the Riganpeicuo Formation into two sets. The Mugagangri Group showed the characteristics of the sedimentary chaotic melanges and the Zhonggang ocean island was disassembled and volcanic-sedimentary sequence model was built. The first discovery of the eclogites and Quercus pseudosemicarpifolia provided important information for tectonic evolution of the Bangong Lake-Nujiang River and uplift of the plateau. The strata in the study area were divided into 3 structural layers,6 tectonic events since Mesozoic and 2 prospecting areas and 1ore prospecting target were found. We also systematically summarized four tectonic evolution stages of the Bangong Lake-Nujiang River, spreading and formation (about 242 Ma), subduction (Early Jurassic), metamorphic rocks exhumation (194 Ma), closure (110-85 Ma) and collisional orogeny.

       

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