大别造山带北部石竹河片麻岩的锆石U-Pb年龄及其地质意义

Zircon U-Pb dating of gneiss from Shizhuhe in North Dabie and its geologic implications.

大别造山带北部石竹河二长片麻岩的锆石 U- Pb年龄测定结果表明 ,其原岩形成时代为 70 7± 42 Ma,在 2 2 9±18Ma曾受到高温变质作用。这一结果表明印支期变质作用不仅反映在大别造山带南部的变质岩中 ,而且造山带北部的部分变质岩也保存了这一重要记录。大别造山带北部存在印支期变质年龄的片麻岩、榴辉岩或残留相表明 ,该地块与造山带南部一样是印支期板块俯冲碰撞中俯冲板块的一部分。

The zircon U Pb age of a monzogneiss from Shizhuhe in North Dabie was dated. The results indicate that the protolith of the gneiss was formed at 707±42Ma, and the rock underwent metamorphism at 229±18Ma. The ages suggest that the Indosinian metamorphism of the Dabie orogen affected not only the metamorphic rocks in South Dabie, and also some rocks in North Dabie. The gneiss with Indosinian metamorphic age, the occurrence of eclogites and eclogite facies relics in North Dabie suggest that North Dabie was a part of the subducted block as the South Dabie. The suture line between North China Block and Yangtze Block may be in the north of Dabie orogen.