苏北海州群双峰式火山岩及其构造背景

On the volcanic rock with bimodal and their tectonic setting in the Haizhou Group of Northern Jiangsu

在苏胶南古小陆块的东南部,断续出露一套浅—中变质岩系,称海州群。海州群含有大量的火山岩及火山碎屑岩。主要岩石类型有石英角斑质岩、角斑-石英角斑质岩、细碧质岩及个别角斑质岩。它为寻找与细碧角斑岩及凝灰岩有关的块状硫化物矿床及贵金属矿床等提供了一定的地质前提,是江苏古火山变质岩系找矿远景区之一。为此。

The volcanic rocks are divided into A-series and C-series. The A-series belongs to the alkali-basalt series, their magma is the batch partial melting of upper mantle. The C-series is ofhe acidic series of which the magma is generated from the partial melting sialic crust, These two series constitute a typical bimodal-style volcanic rock complex in chemical composition which is different from that of volcanic rocks of ophilite complex and island arc-volcanic rocks. It is characterized by the chemical composition of volcanic rock in intracontinental rift of which the mag was formed by local remelting of crystalline basement of Donghai Group. So it is the results ofvolcanic activity of Haizbou rift in the austral margin of Su-Jianonan old small landmass duringmiddle-late Proterozoic Era. It infers that the Haizhou rift is a continental rift of which the evoluon is not complete and its bottom is a taphrogeosyncline of sialic crust owing to the northward movement of old Yangtze landmass during the Jinning Orogeny. Its volcanic activity is characterized by potassium-rich alkalic or alkalic acidic eruption.