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孙高远,王建刚,胡修棉,Marcelle K BOUDAGHER-FADAL. 2018. 西藏札达地区上白垩统-下始新统达机翁组:对冈底斯弧前盆地演化的制约. 岩石学报, 34(6): 1847-1861
西藏札达地区上白垩统-下始新统达机翁组:对冈底斯弧前盆地演化的制约
作者单位E-mail
孙高远 河海大学海洋学院, 南京 210098  
王建刚 中国科学院地质与地球物理研究所, 北京 100029 wangjiangang@mail.iggcas.ac.cn 
胡修棉 内生金属矿床成矿机制研究国家重点实验室, 南京大学地球科学与工程学院, 南京 210023  
Marcelle K BOUDAGHER-FADAL Department of Earth Sciences, University College London, London WC1H 0BT  
基金项目:本文受国家自然科学青年基金项目(41202082、41602104)和江苏省自然科学青年基金项目(BK20160858)联合资助.
摘要:
      冈底斯弧前区域地层沉积记录,对新特提斯洋消亡和印度-亚洲碰撞过程的研究具有十分重要的意义。位于西藏南部札达地区的达机翁组,北邻冈底斯岩浆弧,南靠雅鲁藏布江缝合带。岩石组成主要包括砾岩、岩屑砂岩、泥页岩和灰岩等。沉积环境分析认为达机翁组形成于扇三角洲相环境。火山灰锆石U-Pb定年、碎屑锆石最年轻年龄以及底栖有孔虫化石组合共同约束达机翁组的形成时代为晚白垩世-始新世早期(即ca.73~49Ma)。物源区分析结果表明达机翁组物源类似于区域上分布的日喀则弧前盆地沉积,直接以北侧冈底斯岩浆弧为主要物质源区。通过与区域弧前沉积对比,为冈底斯弧前盆地海相地层时代提供制约,结果显示新特提斯洋在亚洲大陆南缘的弧前海退存在东西方向上的穿时性,即海水自东向西逐渐退出,并最终在~49Ma退出冈底斯-拉达克弧前区域。
英文摘要:
      The marine strata in the Gangdese forearc area play a significant role in the study of the closure of Neo-Tethyan Ocean and the subsequent India-Asia collision. The Dajiweng Formation exposed in the Zhada area, southern Tibet, is bounded by the southern Gangdese magmatic arc to the north and the Indus-Yarlung Zangbo suture zone to the south. It is mainly composed of conglomerate, sandstone, mudstone and limestone. Sedimentary analysis revealed that the Dajiweng Formation had been deposited in the fan-delta environment. A combination of the tuff zircon U-Pb dating, youngest detrital zircon ages and large benthic foraminiferal assemblage yielded that the Dajiweng Formation formed during the Late Cretaceous-Early Eocene period (i.e., ca.73~49Ma). The provenance data showed that the Dajiweng Formation is similar to that of the Xigaze forearc basin sediments, which were mostly derived directly from the Gangdese magmatic arc. In contrast to the Gangdese-Ladakh forearc deposits, the forearc marine regression was diachronous along the strike, i.e. the sea water regressing gradually from east to west and disappearing at ~49Ma in the western Gangdese-Ladakh forearc area.
关键词:始新世  沉积记录  锆石U-Pb和Hf  弧前海退  弧前盆地
投稿时间:2017-06-05  修订日期:2017-12-03
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