1:5万区域地质调查工作对青海夏吾一带巴龙贡噶尔组的岩性特征、基本层序、沉积构造、岩相变化、时代依据等进行了系统收集及研究,于该套地层中新发现了变玄武安山岩.采用LA-ICP-MS锆石U-Pb定年方法,获得锆石U-Pb同位素年龄为427.2±2.8Ma,即该套火山岩形成于早志留世.结合前人研究成果,确定巴龙贡噶尔组的形成时代为早志留世.研究成果对于厘定南祁连的早古生代地层层序及构造演化具有重要意义.%The Balonggongga'er Formation is distributed in the South Qilian Mountain and belongs to marine terrestrial clastic rock series, and its geological epoch has aroused much attention. Based on 1:50000 regional geological survey, the authors systematically studied the lithological characteristics,basic sequence,sedimentary structure,lithofacies change,and age of the Balonggongga'er For-mation.Some basaltic andesite samples within the Balonggongga'er Formation were identified,and LA-ICP-MS zircon U-Pb analy-ses indicate that the basaltic andesite was formed at 427.2±2.8Ma,belonging to the Early Silurian period.In combination with previous achievements,the authors have further confirmed that the Balonggongga'er Formation was formed in Early Silurian period.These re-sults are of importance for the study of the Early Paleozoic stratigraphic sequence and tectonic evolution in the South Qilian Mountain.
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