广东梅县地区晚中生代伸展构造特征

广东梅县地区位于政和—大埔断裂南段之莲花山断裂带中。通过开展1∶5万野外地质调查及室内研究表明,广东梅县地区存在晚中生代伸展构造体系,该体系主要由剥离断层和2个不同层次的剥离层组成,结合火山岩、侵入岩、沉积地层接触关系及高精度测年数据,讨论了该体系的形成时限,认为其形成和主导作用时期在晚侏罗世—早白垩世早期(160~135 Ma),最大伸展期在145 Ma左右;前人认为莲花山断裂为早古生代俯冲带,但研究表明,其构造属性为晚侏罗世形成的剥离断层。因此,政和—大埔断裂一带很可能也存在晚中生代的伸展构造体系,说明华南主要构造形迹奠定于中生代,这为华南主要热液金属矿床区域成矿规律研究提供了新的参考模型。

Characteristics of Late Mesozoic extensional structures of Meixian in Guangdong Province

Meixian in Guangdong Province, is located in the Lianhuashan fault zone, southern part of Zhenghe-Dapu fault zone. The 1:50 000 field geological survey and indoor analyses have indicated the existence of Late Mesozoic extensional structure system in the Meixian of Guangdong Province. This system consists of detachment fault and two stripper layers with different levels. Based on contact relationship and high-precise dating data of volcanic rocks, intrusive rocks and sedimentary rocks, we concluded that the time scale of this extensional structure system ranges from Late Jurassic to Early Cretaceous (160-135 Ma), with the peak time of extension around 145 Ma. Lianhuashan fault zone was previously believed to be formed around the early Paleozoic, and now it is confirmed to be a detachment fault formed at the Late Jurassic. So the Zhenghe-Dapu fault extensional system also occurred in the Late Mesozoic. The results above showed that the dominant tectonic activity in the southern China occurred in the Mesozoic, providing a new reference model for the study of regional metallogenic rules of hydrothermal metal deposit in the southern China.