1:25万亚热幅、普兰县幅、霍尔巴幅、巴巴扎东幅(国内部分)地质调查成果与进展

1:250 000 Yagra, Burang, Horba and Babazhadong Sheets in Xizang

关键词:  1:25万  地质调查  普兰县幅  霍尔巴幅  巴巴扎东幅(国内部分)  成果与进展  西藏

Key words:  1:250 000  geological survey  Yangra Sheet  Burang Sheet  Horba Sheet  Babazhadong Sheet  development  Xizang

摘要:

在雅鲁藏布江南带分区蹬岗组之上新发现硅质岩与玄武岩两套地层,分别新建为郭雅拉组和盐多组,时代为始新世;在北带分区嘎学组之下发现一套砂岩、页岩的韵律层,新建为桑果组;建立了仲巴分区泥盆纪系马攸木群,分上、中、下3个组和4个岩性;对石炭纪地层新命名为康拓组和拉沙组;将下二叠统变质玄武岩命名为才巴弄组;将原划冈仁波齐组中下部与沃马组下部地层新命名为旦增竹康组,时代为中新世,其上部地层仍为沃马组,时代为上新世,两组合称岗仁波齐群。进一步证实了雅鲁藏布江缝合带具两带夹一微陆的特点,南带在中侏罗世发生过双向俯冲事件。对蛇绿岩、混杂岩进行详细划分。

Abstract:

Two successions of strata composed of siliceous rocks and basalts are found to be overlain upon the Denggang Formation and renamed the Guoyala and Yanduo Formations of Eocene in age in the southern subzone of the Yarlung Zangbo zone. The rhythmic succession composed of sandstones and shales beneath the Gaxue Formation is renamed the Sangguo Formation in the northern subzone of it. The Devonian Mayum Group and Carboniferous Kangtog and Lasha Formatigns and Lower Permian Caibanong Formation are re-established in the Zhongba stratigraphic subprovince. The middle and lower parts of the formerly Kangrinboqe Formation and the lower part of the Orma Formation are renamed the Danzengzhukang Formation of Miocene in age, and the upper strata of the formerly Kangrinboqe Formation is defined as the Orma Formation of Pliocene in age, both of the Formations are incorporated into the Kangrinboqe Group. The ophiolites and melanges are grouped into seventeen mappable units. The oceanic-floor bidirectional subduction once took place during the Middle Jurassic in the southern subzone of the Yarlung Zangbo zone.