青藏高原北羌塘他念他翁山吉塘岩群酉西岩组时代的确定

关于位于青藏高原北羌塘地区的吉塘岩群是否属于前寒武纪变质岩系历来存在较大争议,对其形成年龄一直缺少有效同位素年代学限定。通过高精度的LA-ICP-MS(激光剥蚀等离子体质谱仪)锆石微区原位U-Pb同位素测年,获得他念他翁山一带吉塘岩群酉西岩组石英绿泥片岩(原岩为中性火山岩)的原岩形成年龄为965±55Ma,绿片岩(原岩为中基性火山岩)的原岩形成年龄为1048.2±3.3Ma,表明吉塘岩群酉西岩组原岩形成时代为蓟县纪末—南华纪初。吉塘岩群酉西岩组可能代表Rodinia超大陆裂解早期伸展期间火山-沉积作用的地质记录。

The age of Youxi formation of Jitang rock Group in Taniantaweng mountains, northern Qiangtang, Qinghai-Tibet Plateau

Whether the Jitang rock group in northern Qingtang,Qinghai-Tibet Plateau belongs to Precambrian metamorphite series has long been controversial,especially on the age of formation due to lack of effective isotopic age to restrict its age.High resolution LA-ICP-MS in situ dating yields the original rock U-Pb age of 965±55Ma and 1048.2±3.3 Ma for quartz-chlorite schist(the protolith is intermediate volcanic rocks) and greenschist(the protolith is intermediate-basic volcanic rocks) in Jitang rock Group,Taniantaweng mountains,respectively.This indicates the original rock of Youxi Formation of the Jitang rock group formed during the end of Jixian Period or early Nanhua Period.Meanwhile,the Youxi Formation of the Jitang rock group may represent the geological record of volcanicsm-sedimentation during the extension of early Rodinian supercontinent break.