华南双桥山群和河上镇群凝灰岩中的锆石SHRIMP U-Pb年龄—对江南新元古代造山带演化的制约

SHRIMP U-Pb zircon dating of tuff in the Shuangqiaoshan and Heshangzhen groups in South China—constraints on the evolution of the Jiangnan Neoproterozoic orogenic belt

摘要: 通过西澳科庭大学离子探针中心的远程测试，在双桥山群横涌组和安乐林组斑脱岩中获得大量锆石，其SHRIMP U-Pb加权平均年龄为831 Ma±5 Ma(横涌组)、829 Ma±5 Ma（安乐林组），在河上镇群上墅组中获得加权平均年龄767 Ma±5 Ma。锆石SHRIMP U-Pb年龄表明华南地区广为发育的双桥山群应归入新元古界,该年龄为标定双桥山群在地层柱中的位置提供了准确的年代学依据。

Abstract: A large number of zircons were obtained from three samples of bentonite in the Hengyong and Anleling formations of the Shuanqishan Group and Heshangzhen Group. They yielded weighted mean 206Pb/238U ages of 831 ± 5 Ma for the Hengyong Formation, 829 ± 5 Ma for the Anleling Formation and 767 ± 5 Ma for the Shangshu Formation of the Heshangzhen Group by the sensitive high-resolution ion microprobe at the SHRIMP center, Curtin University, Western Australia. These ages show that the widespread Shuangqiaoshan and Heshangzhen groups should be assigned to the Neoproterozoic and provide accurate chronostratigraphic evidence for the determination of the location of the Shuanqishan Group in the stratigraphic column.