赣南临江盆地余田群双峰式火山岩的Rb-Sr年代学研究

位于南岭构造岩浆带东段,受三南—寻邬断裂带控制的临江中生代火山沉积盆地内发育一套由玄武岩及流纹质火山岩组成的十分典型的双峰式火山岩组合。对临江地区余田群菖蒲组中存在的双峰式火山岩组合进行了Rb-Sr同位素定年研究,确定其基性端元(玄武岩)和酸性端元(流纹岩)的Rb-Sr等时线年龄分别为(173.7±2.5)Ma和(174.9±3.9)Ma,从而确认余田群菖蒲组双峰式火山岩的形成时代为中侏罗世。这为南岭东段在燕山早期发生的伸展裂解构造事件提供了可信的同位素年龄证据。

Rb-Sr chronology of bimodal volcanic rocks of the Yutian Group in the Linjiang basin, southern Jiangxi

Abstract: A typical bimodal volcanic rock association, composed of basalt and rhyolitic volcanic rocks, is distributed in the Mesozoic Linjiang volcanic-sedimentary basin, which is located in the eastern segment of the Nanling tectono-magmatic belt and controlled by the Sannan-Xunwu fault belt. The Rb-Sr isochron ages of the basic end-member (basalt) and acid end-member (rhyolite) of the bimodal association in the Changpu Formation of the Yutian Group in the Linjiang area are 173.7 ± 2.5 Ma and 174 .9 ± 3.9 Ma respectively. Thus it is ascertained that the bimodal volcanic rock association is of Middle Jurassic age. This provides convincing isotope age evidence for the extension and break-up of the eastern segment of the Nanling during the Early Yanshanian.