苏北盆地与周围地区的新生代玄武岩及其形成的大地构造环境

Cenozoic Basaltic Rocks in North Jiangsu Basin and Surrounding Area and Their Bearing on Tectonic Environment

本文首先计算了苏北盆地及周围地区30多个地点的150多个玄武岩的岩石化学分析数据的标准矿物值,并进行化学分类,进而探讨了各时期岩浆活动性质。利用地质温度计和压力计对照计算了部分地点玄武岩的形成条件,并综合各种岩石化学特征指数、岩浆来源深度以及微量元素含量等分析结果,着重讨论了岩浆活动的规律及其所反映的大地构造环境问题。

The Cenozoic basaltic rocks in North Jiangsu Basin and the surrounding area are the products of the four main periods of volcanic activity, from Early Tertiary to Quaternary. Their formation is closely related to the tectonic evolution in this area. Based on the study of the ages of the rocks and their mineral and chemical properties, the author discusses in this paper the forming conditions of the rocks and their tectonic implication. The activity of basaltic magma in the studied area may be divided into three major stages according to the chemical properties, appearing roughly two cycles. Comprehensive analyses indicate that the rocks formed at the rather lower pressure. The general trend of the magmatic activity was that the alkalinity increased and so did the depth of initial magma, associated with the change of the tectonic environment related to the plate motion in Cenozoic.