浙南中元古界龙泉群的地质特征及构造演化

龙泉群（Pt2ln）是浙闽前寒武纪变质基底的一个组成部分,它与下元古界八都群之间以大型韧性剪切带为界,系浙闽克拉通于中元古中晚期（1.0～1.4Ga）张裂环境下的火山—沉积产物。本群底部为双峰式火山建造,中部（主体）为砂泥质碎屑岩建造,上部为碎屑岩—碳酸盐岩建造。主要岩石类型有变粒岩、云母片岩、绿帘斜长角闪岩,含铁石英岩和大理岩。它经历了高绿片岩相区域变质作用和三期褶皱变形,总体构造形态为近南北向的线型褶皱系。龙泉群变质基性火山岩的化学成分相当于大陆拉斑玄武岩,原始岩浆源自壳下亏损地幔。变质火山岩类的 Sn-Nd、Rb-Sr 等时线年龄分别为1376±82Ma 和952±11Ma,989±40Ma。在龙泉群的整个构造演化历史中没有洋壳的出现与消减。

GEOLOGICAL FEATURES AND TECTONIC EVOLUTION OF THE MIDDLE PROTEROZOIC LONGQUAN GROUP IN SOUTHERN ZHEJIANG

The Longquan Group is a component part of the Precambrian metamor- phic basement of Zhejiang and Fujian.It is separated from the lower Pro- terozoic Badu Group by a large ductile shear zone and is the volcanic-sedi- mentary product in a tensional fracturing environment.The basal part of this group is represented by a bimodal volcanic formation,the middle part an arenaceous-pelitic clastic formation,and the upper part a clastic-carbonate formation. The main rock types include granulitite,mica schist,epidote-plagio- clase amphibolite,itabirite and marble.The group has undergone regional metamorphism and folding.The general structural configuration is a nearly N-S-trending linear fold system.