木嘎岗日岩群是羌塘南缘的增生楔杂岩

发布时间：2019-03-08 08:20

【摘要】：木嘎岗日岩群是班公湖—怒江缝合带的标志性单元,其内部构造变形复杂,很难作为连续的沉积层序进行分析,因而其板块构造背景有待进一步解释。本文在野外工作基础上,对西藏改则地区木嘎岗日岩群地质特征取得了如下认识:(1)木嘎岗日岩群由有序地层和混杂岩组成,有序地层可以分解为4个非正式地层分段,各自具有不同的沉积学、岩性和物源特征,且具有较为稳定的走向延伸,有作为填图地质单元的可能,这为解体和细分木嘎岗日岩群提供一种可行方案;(2)混杂岩以构造接触关系伏于有序地层之下,且混杂岩内部物质成分具有分层特征,上部富"原地"砂岩块体,下部富"外来"洋壳块体,这表明在混杂岩形成过程中洋壳位于混杂岩之下;(3)木嘎岗日岩群内部发育北倾南冲的逆冲推覆体系,叠瓦式发育的逆断层可能在深部汇入由构造混杂岩组成的主滑脱断层。组合的地质特征表明木嘎岗日岩群是羌塘南缘增生楔杂岩,形成于班公湖—怒江洋壳北向俯冲背景下的羌塘南缘增生过程。
[Abstract]:The Mugagangri Group is a typical unit of the Bangongghu-Nujiang suture zone. Its internal tectonic deformation is complex and difficult to be analyzed as a continuous sedimentary sequence, so its plate tectonic background needs to be further explained. On the basis of field work, this paper has obtained the following knowledge about the geological characteristics of the Mugagang Riyan Group in Xianze area, Tibet: (1) the Mukagang Riyan Group is composed of ordered strata and mixed rocks, and the ordered strata can be divided into four informal strata segments. Each of them has different characteristics of sedimentology, lithology and provenance, and has a relatively stable strike extension, which may be used as a mapping geological unit, which provides a feasible scheme for disintegration and subdivision of the Mugagangri Group. (2) the migmatite lies under the ordered strata in the relationship of structural contact, and the internal material composition of the mixed complex has the characteristics of stratification, the upper part is rich in "in situ" sandstone block and the lower part is rich in "foreign" oceanic crust block. This indicates that the oceanic crust lies under the migmatite during the formation of the migmatite. (3) the thrust nappe system of north dip and south thrust is developed in the Mugagang Riyan Group, and the imbricate type of thrust fault may converge into the principal slip fault composed of tectonic melange in the deep part. The geological characteristics of the assemblage indicate that the Mugagangri Group is a accretive wedge complex in the southern margin of Qiangtang and formed in the southern margin of Qiangtang under the background of the northward subduction of the Bangonghu-Nujiang oceanic crust.
【作者单位】：成都理工大学油气藏地质及开发工程国家重点实验室;成都理工大学地球科学学院;中国地质大学(北京)地球科学与资源学院;
【基金】：国家自然科学基金项目(41102065) 中国地质调查局地质调查项目(1212011121297)
【分类号】：P548

【相似文献】