赣东北珍珠山群的建立及意义

Establishment of the Zhenzhushan Group in northeast Jiangxi and its signi ficance

珍珠山群是发育在扬子板块与华夏板块拼接带东段之婺源—乐平地区的一套中元古代蓟县纪变质深海浊积岩-火山岩组合,自下而上可进一步划分为佛子坑组、鄣山组、周溪组、中洲组,火山活动呈现由弱—强—弱的演化规律。岩石化学特征反映其大地构造环境属火山岛弧或活动边缘盆地,其层位与弧后盆地双桥山群修水组、溪口群,弧间盆地诸家群、铜厂岩群、张村岩群,火山岛弧双溪坞群相当,但岩性组合差异甚大,属同时异相产物。它们共同构成扬子陆缘的双列岛弧造山带模式,是中元古代末华夏板块与扬子板块俯冲-碰撞造山的结果。珍珠山群的建立,为华南中元古代板块碰撞提供了新的证据。

The Zhenzhushan Group consists of a suite of Mesoproterozoic J ix ianian metamorphosed abyssal turbidite and volcanic rocks in the eastern segment of the convergence zone between the Yangtze plate and the Cathaysian plate in the Wuyuan-Leping areas,northern Jiangxi.From below upward it can be further divided into the Fuzikeng Formation,Zhangshan Formation,Zhouxi Formation and Zhongzhou Formation.Volcanism shows the trend of evolutions from weak to st rong and again to weak.The petro-chemical characteristics suggest that the tec tonic environment belongs to the volcanic island arc or active marginal basin and that the group is stratigraphically equivalent to the Xiushui Formation of the Shuangqiaoshan Group and the Xikou Group in a back-arc basin,the Zhujia Group,Tongchang Group-complex and Zhangcun Group-complex in an inter-arc bas in and the Shuangxiwu Group in a volcanic is-land arc,but they differ greatl y in rock association.They are synchronous but heteropic products.They combi ne to form a double-island arc orogenic belt model on the Yangtze continental m argin.It is the re-sult of subduction-collisional orogeny of the Cathaysian plate and Yangtze plate at the end of the Meso-proterozoic.The establishment of the Zhenzhushan Group provides new evidence for Mesoproterozoic plate col lision in South China.