江南古陆中段沧水铺群锆石U-Pb年龄和构造演化意义

江南古陆中段湖南益阳地区沧水铺群发育在冷家溪群和板溪群之间,其在地层柱中的位置一直是中国地质学家解疑江南造山带何时启动的关键层位。笔者在沧水铺群中的火山集块岩中获得锆石SHRIMP U-Pb年龄(821±13)Ma,再次验证了沧水铺群中的火山岩是820 Ma武陵运动之前的火山事件的产物,与武陵运动的启动有关,也说明该期火山岩与冷家溪群中大量的火山凝灰岩为同一构造运动的产物。

SHRIMP dating of Cangshuipu Group in the middle part of the Jiangnan Orogen and its implications for tectonic evolutions

The Cangshuipu Group is developed between the Lengjiaxi Group and Banxi Group in Yiyang area of Hunan Province,located in the middle part of the Jiangnan orogenic belt.It is considered that the study of its position in chronostratigraphic column can solve the problem of the initiation of the Jiangnan orogenic belt.The authors obtained a SHRIMP zircon U-Pb age of 821±13 Ma from the volcanic rocks in the Cangshuipu Group.This age suggests that the volcanic rocks represent a volcanic event before the Wuling movement(820 Ma),which was related to the initiation of the Wuling movement,with the volcanic tuff of this volcanic event being the product of the same tectonic movement as the volcanic tuff in the Lengjiaxi Group.