地学前缘 ›› 2015, Vol. 22 ›› Issue (3): 382-393.DOI: 10.13745/j.esf.2015.03.033

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增生杂岩带1∶5万地质填图的实践与探索： 以西藏羌塘中部角木日地区为例

毛晓长, 王根厚, 梁晓, 张锋, 刘洋, 刘军平, 郑艺龙   

  1. 中国地质大学(北京) 地球科学与资源学院， 北京 100083; 中国地质调查局， 北京 100037; 天津地质调查中心， 天津 300170; 云南省地质调查局， 云南 昆明 650216
  • 收稿日期:2014-04-09 修回日期:2014-06-18 出版日期:2015-05-15 发布日期:2015-05-15
  • 作者简介:毛晓长(1979—)，男，博士研究生，构造地质学专业，主要从事造山带地质研究及区调管理。E-mail：xmaoteng@163.com
  • 基金资助:

    中国地质调查局项目(12121010818014，1212011221115)；中国地质大学(北京)优秀教师基金项目(292014004)

Practice and exploration of 1∶50000 geological mapping in accretionary complex belt: An example from Qomo Ri area of Central Qiangtang, Tibet.

 MAO  Xiao-Chang, WANG  Gen-Hou, LIANG  Xiao, ZHANG  Feng, LIU  Xiang, LIU  Jun-Beng, ZHENG  Yi-Long   

  • Received:2014-04-09 Revised:2014-06-18 Online:2015-05-15 Published:2015-05-15

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摘要：

增生杂岩带1∶5万地质填图的理论与方法是目前区域地质调查工作亟待解决的难点。1∶5万地质填图是调查增生杂岩的地层组成、拼贴结构与构造变形的重要手段，也是构造演化研究的基础。羌塘中部角木日一带出露典型的印支期增生杂岩，按照物质组成与构造调查并重的原则开展了1∶5万地质填图与1∶1万构造岩性解析填图。发现增生杂岩物质组成具有基质岩块的拼贴结构，边界为俯冲期形成的脆性、脆韧性及韧性剪切断层，基质由大陆斜坡洋底环境的细碎屑沉积岩及强面理化构造岩组成，岩块为洋岛蛇绿岩残块、基性岩脉残块、海山碳酸盐岩残块、外来岩块等。其以俯冲期后收缩背景下的缩短褶劈理S2为区域面理，并叠加有造山期后陆内浅层次变形。地质图图面表达采用了“三元”与“四要素”方法，客观表达了该杂岩的组成与结构。上述实践提出了当前增生杂岩带地质填图的工作方法及填图单位划分与图面表达的方式，有益于探索我国现阶段造山带地质填图的方法。

关键词: 1∶5万地质填图, 增生杂岩, 角木日, 构造, 造山带

Abstract:

The theory and method for 1∶50000 geological mapping in accretionary complex belt is a focus problem for present regional geological surveys. Based on 1∶50000 geological mapping, the characteristics of lithologies, collage style and structural framework for accretionary complex can be easily found, which then contributes to the knowledge of tectonic evolution in suture zone. After 1∶50000 geological mapping and 1∶10000 structurelithology mapping in Qomo Ri Indosinian accretionary complex in Central Qiangtang, it is discovered that this complex is comprised of intensivecleavaged matrix and tectonic blocks that weld each other by brittle, brittleductile and ductile shear faults forming at the oceanic subduction stage. The matrix are composed of fine plastic rocks from submarine fans, continental slope turbidite and deep ocean deposit, and also other strongly foliated rocks. Tectonic blocks mainly contain OIBtype ophiolite relics, mafic dike relics, seamount carbonate rock relics, exotic block relics etc. This complex is characterized by a stable regional foliation S2 of CCCtype, forming under a compressional background following oceanic subduction. It is also superimposed by postorogenic shallow level deformations showed by nonpenetrative foliation S3. The geological maps are expressed by means of a method named “threecomponent” and “fourfactor”. The above practice presents methods including outcrop observation, mapping unit classification, and graphic expression of map for 1∶50000 geological mapping in accretionary complex, which also provides implications for the present geological mappings in orogenic belt.

Key words: 1∶50000 geological mapping, accretionary complex, Qomo Ri, structure, orogenic belt

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