西藏羌塘地体三叠纪—侏罗纪海相砂岩颗粒组分及其构造意义 Mesozoic Sandstone Composition in the Qiangtang Block, Tibet: Implications for Tectonic Setting期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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西藏羌塘地体三叠纪—侏罗纪海相砂岩颗粒组分及其构造意义

引用本文：	张玉修,张开均,夏邦栋,谢尧武.西藏羌塘地体三叠纪—侏罗纪海相砂岩颗粒组分及其构造意义[J].沉积学报,2006,24(2):165-174.

作者姓名：	张玉修张开均夏邦栋谢尧武

作者单位：	中国科学院边缘海地质重点实验室广州 510640

基金项目：	中国科学院“百人计划”，中国科学院边缘海地质重点实验室研究基金(MSGL04-14)资助

摘要：	来自羌塘地体(33°-35°N, 85°-93°E)的154件中生界砂岩样品颗粒组分实验结果表明，羌塘地体中部中下三叠统砂岩(Q61±8F27±13L12±10, Qm59±8F28±13Lt13±9, Qp28±22Lvm72±22Lsm0±0)的物源区为复杂的再旋回造山带和陆块内部，大部分上三叠统砂岩(Q78±14F6±5L16±12, Qm77±15F6±5Lt17±12, Qp14±23Lvm34±37Lsm52±33)、下侏罗统砂岩(Q83±20F2±2L15±22, Qm79±23F2±2Lt19±24, Qp35±19Lvm0±0 Lsm65±19)、中侏罗统砂岩(Q69±22F6±6L24±25, Qm67±22F6±6Lt26±24, Qp14±22Lvm32±38Lsm54±38)和上侏罗统砂岩(Q80±17F6±4L14±17, Qm78±17F6±4Lt16±16, Qp17±23Lvm27±35Lsm56±34)的物源区以再旋回造山带为主，然而，南羌塘地体南缘的上三叠统以及北羌塘地体南缘的下侏罗统同时发育物源来自陆块内部的砂岩。整个中羌塘复背斜带砂岩颗粒中常含有不稳定重矿物及其它易风化铁镁矿物表明该地区有丰富的蛇绿岩残片，这预示着双湖缝合带沿整个中羌塘复背斜带展布，羌塘中部含蓝片岩变质杂岩体可能形成于中羌塘不规则大陆边缘的海湾处，而不是来自金沙江缝合带。中生代砂岩的颗粒组分及岩石学证据表明，中羌塘复背斜至少从早三叠世就因为造山隆升并遭剥蚀提供物源。上三叠统砂岩物源区为再旋回造山带，这表明这种挤压背景下不存在沿班公湖—怒江缝合带弧后扩张的伸展机制。
关键词：	砂岩中生代羌塘青藏高原特提斯
文章编号：	1000-0550（2006）02-0165-10
收稿时间：	2005-03-15
修稿时间：	2005-09-21
Mesozoic Sandstone Composition in the Qiangtang Block, Tibet: Implications for Tectonic Setting

ZHANG Yu-xiu,ZHANG Kai-jun,XIA Bang-dong,Xie Yao-wu.Mesozoic Sandstone Composition in the Qiangtang Block, Tibet: Implications for Tectonic Setting[J].Acta Sedimentologica Sinica,2006,24(2):165-174.

Authors:	ZHANG Yu-xiu ZHANG Kai-jun XIA Bang-dong Xie Yao-wu

Institution:	Key Laboratory of Marginal Sea Geology, Chinese Academy of Sciences, Guangzhou 510640

Abstract:	One hundred and fifty four Mesozoic sandstone samples from the Qiangtang block (ca. 3３°~35°N, 85°~93°E) were conducted for analysis of detrital modes, in an attempt to evaluate their provenance and the type of tectonic setting in which they were deposited. The Lower Middle Triassic sandstones (Q61±8F27±13L12±10, Qm59±8F28±13Lt13±9, Qp28±22Lvm72±22Lsm0±0) in central Qiangtang are characterized by complex derivations from both recycled orogen and continental block provenances. The most of the Upper Triassic (Q78±12F7±7L15±11, Qm77±12F7±7Lt16±11, Qp16±11Lvm30±35Lsm54±33), Lower Jurassic (Q83±20F2±2L15±22, Qm79±23F2±2Lt19±24, Qp35±19Lvm0±0 Lsm65±19), Middle Jurassic (Q69±22F6±6L24±25, Qm67±22F6±6Lt26±24, Qp14±22Lvm32±38Lsm54±38), and Upper Jurassic (Q80±17F6±4L14±17, Qm78±17F6±4Lt16±16, Qp17±23Lvm27±35Lsm56±34) sandstones are dominated by recycled orogen origin. However, the sandstones that were derived from continental block source also exist in the southern margin of southern Qiangtang and in the Lower Jurassic strata in the southern margin of northern Qiangtang. It could have contained abundant ophiolitic fragments and other readily decomposed ferromagnesian minerals across the entire anticlinorium. These mafic minerals point to the presence of the Shuanghu suture along the entire central Qiangtang anticlinorium and the blueschist bearing metamorphic complexes in central Qiangtang could be accommodated in a large scale enclave in an irregular central Qiangtang continental margin. The distribution of Mesozoic recycled orogen derived sandstones on Qiangtang indicates a contraction background, supporting〖KG*2〗a tensile mechanism for back arc spreading along the Bangong Nujiang belt. 

Keywords:	sandstone Mesozoic Qiangtang Tibetan plateau Tethys
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