赣东北地区早古生代登山岩群弧后盆地火山岩的成因与洋壳演化

The Genesis of Back_Arc Basin Volcanic Rocks of Early Paleozoic Dengshan Group Complex in Northeastern Jiangxi

由于早古生代微古化石群的发现（薛重生等，１９９５），赣东北广丰－上饶地区的登山岩群被划归下古生界，本文介绍了登山岩群中海相火山岩的地质特征，对其中的拔竹坑岩组、叶家岩组的火山岩岩石地球化学特征和成因进行了研究，指出该两岩组火山岩均属岛弧拉斑玄武岩系列，并具向大洋拉斑玄武岩过渡的性质，是弧后小洋盆扩张期的产物。两岩组火山岩在火山活动方式、岩浆演化方式和岩浆进化程度上存在与洋壳由早到晚减薄的相应规律变化。

In view of the discovery of Early Paleozoic microfossil group, the Dengshan Group Complex in Guangfeng_Shangrao district of northeastern Jiangxi is considered to be of Early Paleozoic. In this paper, the geology of oceanic volcanic rocks in Dengshan Group Complex is described, and the petrochemistry, geochemistry and genesis of Bazhukeng and Yejia volcanic rocks are studied. It is suggested that all volcanic rocks belong to island arc tholeiitic series, and are somewhat transitiona to oceanic tholeiitic series, being products of the expansion of the back_arc small oceanic basin. There are some differences between volcanic rocks of two formations in volcanic activites and magmatic evolution forms and degrees, which are consistent with the thinning of the oceanic crust from early to late stage.