| 西藏改则地区美苏组岩浆岩锆石U-Pb年龄及地质意义 |
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| 引用本文： | 张耀玲,沈燕绪,吴珍汉,赵珍.西藏改则地区美苏组岩浆岩锆石U-Pb年龄及地质意义[J].地质力学学报,2018,24(1):128-136. |
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| 作者姓名： | 张耀玲 沈燕绪 吴珍汉 赵珍 |
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| 作者单位： | 中国地质大学(北京);中国地质科学院地质力学研究所;国土资源实物地质资料中心;中国地质科学院; |
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| 基金项目： | 中国地质科学院地质力学研究所基本科研业务费项目（DZLXJK201508）；中国地质调查局项目（1212011220903） |
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| 摘 要： | 西藏中部南羌塘改则盆地美苏组由砖红色砂砾岩和火山岩夹层组成,一些学者在美苏组建组剖面等地获得古新世—始新世的K-Ar年龄(34.0~69.1Ma),目前对其形成时代还缺少可靠的年代学约束。应用激光烧蚀多接收器电感耦合等离子体质谱仪(LA-MC-ICP-MS)方法,对改则盆地美苏组沉积地层中的流纹岩、石英粗安岩和花岗斑岩中锆石进行了U-Pb同位素测定。结果表明,改则盆地美苏组红层中的三个火山岩样品及一个侵入岩样品岩浆锆石~(206)Pb/~(238)U年龄分别为38.3±0.5 Ma、39.0±0.3 Ma、37.4±0.4 Ma、38.8±0.6 Ma,从而限定了该地区美苏组沉积时代为始新世晚期。改则地区美苏组岩浆岩形成时代为班公湖—怒江缝合带调节印度—欧亚大陆碰撞之后高原内部刚性块体向东"逃逸"而重新活动提供了年代学证据。
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| 关 键 词： | 岩浆岩 U-Pb年龄 美苏组 西藏 始新世 |
| 收稿时间： | 2017/8/1 0:00:00 |
| 修稿时间： | 2017/12/1 0:00:00 |
ZIRCON U-PB AGES OF MAGMATIC ROCKS FROM MEISU FORMATION IN GERZE AREA IN TIBET AND ITS GEOLOGICAL SIGNIFICANCE |
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| ZHANG Yaoling,SHEN Yanxu,WU Zhenhan and ZHAO Zhen.ZIRCON U-PB AGES OF MAGMATIC ROCKS FROM MEISU FORMATION IN GERZE AREA IN TIBET AND ITS GEOLOGICAL SIGNIFICANCE[J].Journal of Geomechanics,2018,24(1):128-136. |
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| Authors: | ZHANG Yaoling SHEN Yanxu WU Zhenhan and ZHAO Zhen |
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| Institution: | China University of Geoscience, Beijing 100083, China;Institute of Geomechanics, Chinese Academy of Geological Science, Beijing 100081, China,Cores and Samples Center of Land & Resources, Sanhe 065201, Hebei, China,Chinese Academy of Geological Science, Beijing 100037, China and Chinese Academy of Geological Science, Beijing 100037, China |
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| Abstract: | The Meisu Formation exposed in Gerze basin of southern Qiangtang, middle Tibet, is composed of red sandstones and conglomerates with volcanic rock interlayers. At present, its formation age is still lack of reliable geochronologic constraints as other researchers only acquired Paleocene-Eocene K-Ar ages(34.0~69.1 Ma) from type section and other places of Meisu Formation. Laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) method is used to determinate zircon U-Pb isotope from rhyolite, quartz trachyandesite, and granite secondary volcanic rock of sedimentary strata of Meisu Formation in Gerze basin. The results indicate that the average 206Pb/238U age of magma zircons of 3 volcanic samples and 1 intrusive rock sample are respectively 38.3±0.5 Ma, 39.0±0.3Ma, 37.4±0.4 Ma and 38.8±0.6 Ma, which defines the formation age of Meisu Formation of this area is late Eocene. The forming age of Meisu Formation of Gerze area provides chronological evidence of reactivation of Bangonghu-Nujiang Suture to regulate internal rigid block of Tibet Plateau "escape" to the East after India-Eurasia continental collision. |
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| Keywords: | magmatic rock U-Pb age Meisu Formation Tibet Eocene |
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