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引用本文:付建刚,李光明,王根厚,黄勇,张林奎,董随亮,梁维. 北喜马拉雅双穹隆构造的建立:来自藏南错那洞穹隆的厘定[J]. 中国地质, 2018, 45(4): 783-802.
FU Jiangang,LI Guangming,WANG Genhou,HUANG Yong,ZHANG Linkui,DONG Suiliang,LIANG Wei. Establishment of the North Himalayan double gneiss domes: evidence from field identification of the Cuonadong dome, south Tibet[J]. Geology in China, 2018, 45(4): 783-802(in Chinese with English abstract).
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北喜马拉雅双穹隆构造的建立:来自藏南错那洞穹隆的厘定
付建刚1,2, 李光明1, 王根厚2, 黄勇1, 张林奎1, 董随亮1, 梁维1
1.中国地质调查局成都地质调查中心, 矿产资源室, 四川 成都 610081;2.中国地质大学(北京)地球科学与资源学院, 北京 100083
摘要:
错那洞穹隆属于北喜马拉雅片麻岩穹隆带(NHGD)的东南部重要组成部分,是本次研究首次发现并确立的穹隆构造。穹隆位于藏南扎西康矿集区南部,由外向内被两条环形断裂划分为三个岩石-构造单元:特提斯喜马拉雅沉积岩系上部单元、中部单元以及核部,其中内侧断裂为下拆离断层,外侧为上拆离断层。上部单元主要由侏罗系日当组的泥质粉砂质板岩和片岩组成,由外向穹隆中心靠近,根据变质矿物组合特征,其岩性呈较明显的渐变过程,即含或者不含变质矿物的泥质粉砂质板岩、含堇青石粉砂质板岩、含石榴石堇青石粉砂质板岩和含石榴石黑云母粉砂质板岩;中部单元从上至下岩石变质程度逐渐加深,构造变形依次增强,岩性依次为日当组低-高变质的片岩(包括含石榴石黑云母石英片岩、含蓝晶石-十字石二云母石英片岩、含矽线石二云母二长片麻岩)、含电气石(化)花岗质黑云母片麻岩、石榴石云母片麻岩和糜棱状石英二云母片麻岩,其典型变质矿物有石榴石、十字石、矽线石和蓝晶石;核部主要由糜棱状花岗质片麻岩夹少量的副片麻岩和错那洞淡色花岗岩组成。错那洞穹隆主要发育四期线理构造:近N-S向逆冲、N-S向伸展线理、近E-W向线理和围绕核部向四周外侧倾伏线理,分别对应了穹隆构造经历的四期主要变形:初期向南逆冲、早期近N-S向伸展、主期近E-W向伸展和晚期滑塌构造运动,其中主期近E-W向伸展对应于错那洞穹隆的形成,其动力学背景可能是印度板块斜向俯冲及由俯冲引起的中地壳向东流动双重作用。错那洞穹隆的发现和确立丰富了NHGD近E-W向伸展构造,进一步将NHGD划分为由近N-S向伸展所形成的穹隆带(简称NS-NHGD)和近E-W向伸展所形成的穹隆带(EW-NHGD)。
关键词:  穹隆  E-W向伸展  错那洞  扎西康  北喜马拉雅片麻岩穹隆带(NHGD)
DOI:10.12029/gc20180410
分类号:P542
基金项目:国家自然科学基金项目(41602214)、中国地质调查局项目(DD20160015)和国家科学技术部“青藏高原典型矿集区透明化与矿体定位预测”(2016YFC060308)联合资助。
Establishment of the North Himalayan double gneiss domes: evidence from field identification of the Cuonadong dome, south Tibet
FU Jiangang1,2, LI Guangming1, WANG Genhou2, HUANG Yong1, ZHANG Linkui1, DONG Suiliang1, LIANG Wei1
1.Chengdu Institute of Geology and Mineral Resources, China Geological Survey, Chengdu 610081, Sichuan, China;2.School of Earth Sciences and Resources, China University of Geosciences(Beijing), Beijing 100083, China
Abstract:
The Cuonadong dome, which is firstly reported in this study, is exposed as an east-southern important part of the North Himalayan gneiss domes (NHGD),. The Cuonadong dome is located in the southern part of the Zhaxikang ore concentration area, which is divided into three tectono-lithostratigraphic units by two circle faults around the dome, which is geometrically from upper to lower (or from outer to inner) in order of cap rocks, decollement system and core, with the outer fault being upper detachment fault and the inner fault being lower detachment fault. The Cuonadong dome is a magmatic orthogneiss and leucogranite mantled by orthogneiss and metasedimentary rocks, which in turn are overlain by Jurassic metasedimentary and sedimentary rocks. The grades of metamorphism and structural deformation increase towards the core, which is consistent with the low to high degree metamorphic schist, tourmaline granitic biotite gneiss, garnet mica gneiss, and mylonitic quartz mica gneiss of the Ridang Formation. Their typical metamorphic minerals include garnet, staurolite, sillimanite and kyanite. The Cuonadong dome has preserved evidence for four major deformational events:southward thrust, early approximately N-S extensional deformation, main approximately E-W extensional deformation, and late collapse structural deformation around the core of the Cuonadong dome, which are consistent with four groups of lineation, respectively. The form of the Cuonadong dome resulted from the main E-W extension which resulted from eastward flow of middle or lower crust from beneath Tibet accommodated by northward oblique underthrusting of Indian crust beneath Tibet. The establishment of the Cuonadong dome has enhanced and enriched the significance of the E-W extension of the NHGD, which is further divided into two structural dome zones according to the different extensional directions:approximately NS extensional North Himalayan gneiss domes (NS-NHGD) and E-W extensional North Himalayan gneiss domes (EW-NHGD).
Key words:  dome  E-W extension  Cuonadong  Zhaxikang  North Himalayan gneiss domes (NHGD)