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496～440 Ma.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±1.0 Ma(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.
The Tanjianshan Group distributed on the northern margin of the Qaidam basin is an important volcanic-sedimentary formation 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 formed in the early-late Ordovician of 496~440 Ma. The revised lithologic and stratigraphic units for the group (from the lower part to upper part):the early-middle Ordovician volcanic-clastic formation, late Ordovician sedimentary formation, late Ordovician volcanic-subvolcanic formation. The previous C formation of the Tanjianshan Group (mauve graywake-conglomerate formation) only experienced weak phyllite-facies metamorphism and is unconformably overlain by the volcanic-subvolcanic formation. The pellite from the former gave rise a Rb-Sr isochron age of 313±1.0Ma, 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.
出处
《西北地质》
CAS
CSCD
2006年第3期83-90,共8页
Northwestern Geology
基金
西部矿业公司项目(20040068)
关键词
柴达木盆地北缘
滩间山群
时代
岩石地层单位
northern margin of the Qaidam basin
Tanjianshan Group
age
lithostratigraphic unit
