扬子西缘新元古代裂谷盆地演化的年代学新证据及其意义

扬子西缘康滇裂谷是华南新元古代裂谷系的主要组成部分，对理解华南新元古代裂谷盆地演化与Rodinia超大陆裂解的响应关系具有重要意义。澄江组是康滇裂谷最为典型的沉积充填序列，其时代的准确限定是解析Rodinia超大陆裂解背景下盆地演化的重要前提。本文对滇东北巧家谓姑地区澄江组火山岩开展了LA-ICP-MS锆石U-Pb同位素年代学分析，获得澄江组底部玄武岩年龄806.4±6.7 Ma和下部凝灰岩年龄788.4±5.9 Ma。结合已有年龄数据，将澄江组沉积时代准确限定为800～720 Ma，与开建桥组及陆良组上部为同期异相产物。康滇裂谷的三个次级盆地演化基本同步，均于800 Ma左右开始全面接受沉积，是Rodinia超大陆的裂解的响应。

New zircon U-Pb chronology of the Neoproterozoic rift basin evolution in the western Yangtze Block and its geological significance

The Kangdian rift on the western margin of the Yangtze Plateau is one of the main components of the Neoproterozoic rift system in South China, which is of great significance for understanding the response between the evolution of the Neoproterozoic rift basin in South China and the breakup of the Rodinia supercontinent. The Chengjiang Formation is the most typical filling sequence in the Kangdian rift, and the accurate definition of its sedimentary age is an important prerequisite for the interpretation of the basin evolution in the context of the breakup of the Rodinia supercontinent. LA-ICP-MS zircon U-Pb dating of the volcanic rocks of the Chengjiang Formation in the Qiaojiaweigu area, northeastern Yunnan, yielded an age of 806.4±6.7 Ma for the basalt at the bottom of the Chengjiang Formation and an age of 788.4±5.9 Ma for the tuff at the bottom. Combined with the available age data, the sedimentary age of the Chengjiang Formation is accurately defined as 800~720 Ma, which is a contemporaneous heterogeneous product with the Kaijianqiao Formation and the upper part of the Luliang Formation. The evolution of the three secondary basins in the Kangdian rift is basically synchronous, and they all began to receive full sedimentation at ~ 800 Ma, in response to the breakup of the Rodinia supercontinent.