重庆秀山凉桥板溪群红子溪组凝灰岩SHRIMP锆石测年及其意义

SHRIMP zircon U-Pb dating for crystal tuff from Hongzixi Formation of Banxi Group in Xiushan area,Chongqing,and its significance

关于板溪群的时代归属及其地层划分对比,一直以来存在较大争议,为此作者在重新研究了秀山—梵净山地区板溪群的沉积序列及其演化的基础上,首次对秀山凉桥地区的板溪群红子溪组顶部的晶屑凝灰岩进行了SHRIMP锆石U-Pb测年,研究显示板溪群早期的盆地扩张阶段结束于790Ma左右,随后盆地转入快速充填和差异升降阶段。地层对比研究表明,秀山—梵静山地区的板溪群沉积仅相当于黔东的下江群、湘西的板溪群下部,沉积时限为820～790Ma,是新元古代中期Rodinia裂解背景下的裂陷盆地的早期充填。

There has long existed considerable controversy concerning the epoch and stratigraphic division of Banxi Group. Based on restudying the sedimentary sequence and evolution of Banxi Group in Xiushan- Fanjingshan area, the authors performed the crystal tuff SHRIMP zircon U-Pb dating for Hongzixi Formation of Band Group in Xiushan area. The result suggests Ma, followed immediately by the quick infilling that the expansion of the early Banxi basin ended at about 790 and differential uplifting stage. The deposition epoch of Banxi Group in Xiushan-Fanjingshan area corresponded to that of the lower part of Banxi Group in western Hunan and that of Xiajiang Group in eastern Guizhou, It was the early infilling of the rift basin under with the deposition duration being between 820Ma and 790Ma. the background of the break-up of Rodinia supercontinent in middle Neoproterozoic.