ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    柴达木盆地北缘滩间山群新厘定

    Revision of the Tanjianshan Group on the Northern Margin of the Qaidam Basin

    • 摘要: 滩间山群是柴达木盆地北缘早古生代重要的火山-沉积建造,总体为一套绿片岩相和强烈变形岩石。基于野外地质特征、古生物组合、同位素年龄、构造-热事件和火山-沉积演化等的综合分析,笔者认为滩间山群形成于早—晚奥陶世,同位素年龄在496~440Ma。重新厘定的滩间山群从老到新岩石地层单位有:早—中奥陶世火山-碎屑岩组;晚奥陶世沉积岩组;晚奥陶世熔岩-次火山岩组。原滩间山群c岩组(紫色砂砾岩组)变质微弱,仅达千枚岩相,与晚奥陶世熔岩-次火山岩组间呈角度不整合接触。其中的泥质岩Rb-Sr等时线年龄为313±1.0Ma(代表其千枚岩相的变质年龄),将其从滩间山群中剥离,归属早志留世。新的层序总体反映柴北缘早古生代经历了大陆裂谷开合的演化过程。

       

      Abstract: The Tanjianshan Group distributed on the northern marg in of the Qaidam basin is an important volcanic-sedimentary for mation of the Early Paleozoic and composed of a suit of greenschist facies and strongly deformed rocks.Combined analyses of geological,palaeontological and geochronologic studies have indicated that the Tanjianshan Group was for medin the early-late Ordovician of 496~440 Ma.The revisedl it hologic and strat igraphic units for the group (from the lower part to upper part): the early-middle Or dovician volcanic-clastic formation,late Ordovician sedimentary formation,late Ordovician volcanic-subvolcanic formation.The previous C formation of the Tanjianshan Group (mauve graywakeconglomerate formation) only experienced weak phyllite-facies metamorphism and is unconformably overlain by the volcanic-subvolcanic formation.The pellite from the former gaverise a Rb-Sr isochron age of 313±1.0 Ma,which is interpreted to represent its age of metamorphism.Thus,it is thought that C formation was formed in the early Silurian and separated from the Tanjianshan Group.The new sequences of Tanjianshan Group also suggest that an open-closure cycle of intracontinental rift took place during the Ordovician in the region.

       

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