新疆库鲁克塔格地区晚古元古代兴地塔格群沉积特征及其碳同位素研究

Sedimentation Characteristic and Carbon Isotope Composition in Late Paleoproterozoic Xingditage Group in Quruqtagh Region of Xinjiang,China

新疆库鲁克塔格地区兴地塔格群被认为是晚古元古代地层,该地层黑色云母石英片岩的铅同位素测年为2 063.28~2 321.4 Ma。通过对兴地塔格群辛格尔组白云石大理岩的碳同位素测定,其碳同位素分布在5.15‰^-0.79‰PDB,大部分数据为2‰PDB,明显不同于中元古代1 600~1 400 Ma时期的δ13Ccarb值处在0‰~1‰PDB特征。其与国内外同时期地层的碳同位素数据比较,特别是与华北长城系碳同位素特征比较,认为辛格尔组应该属于晚古元古代1 700~1 600 Ma时期沉积产物。同时,对兴地塔格群的沉积地层特征及沉积环境进行系统研究,认为兴地塔格群沉积环境属于浅海沉积环境。

The Xingditage Group in the Quruqtagh region of Xinjiang is considered as the Late Paleoproterozoic stratigraphy whose age is 2063.28Ma to 2321.4Ma from Pb isotopic dating.The carbon isotopic composition of marble of theXinge＇er Formation of Xingditage Group shows that its carbon isotopic composition ranges from 5.15‰PDB to-0.79‰PDB,and most carbon isotopic data distribute in 2‰PDB,much different from δ13Ccarb composition （0‰-1‰PDB） in early Middle Proterozoic（1 600-1 400Ma）.The comparison of carbon isotopic data of Xinge＇er Formation with those of other continents in this age,particularly with the carbon isotopic composition of Changchengian System in north China platform shows that the Xinge＇er Formation and the Changchengian System are obviously alike in carbon isotopic composition.Therefore,we suggest that the Xinge＇er Formation of Xingditage Group belongs to Late Paleoproterozoic in age. In addition,we also studied the sedimentation character and sedimentation environment of Xingditage Group,showing that sedimentation environment of Xingditage Group is a shallow sea.