浙江诸暨地区陈蔡群主要地质特征及其构造演化探讨

DISCUSSION FOR MAIN GEOLOGICAL FEATURES AND TECTONIC EVOLUTION OF CHENCAI GROUP IN ZHUJI DISTRICT, ZHEJIANG PROVINCE

陈蔡群原岩的主体形成于大洋岛弧环境，由拉斑玄武岩和同源辉长岩，碳酸盐岩和浊流沉积的泥砂质碎屑岩组成；经受了中压角闪岩相区域动力—热流变质作用和多期褶皱变形；岩石地球化学和同位素年代资料表明，中国东南的威尔逊旋回在中元古晚期便已开始，即那时于扬子古陆与华夏地块之间存在一大洋盆地，洋壳上可能存在拉张期残留的花岗质陆壳碎块。中元古晚期开始了洋壳消减作用及其有关的火山—沉积作用，新元古晚期陈蔡大洋岛弧地体与双溪坞陆弧地体拼贴、碰撞，壳体间的聚合作用触发了陈蔡群岩石的变质、变形。

The main body of the origional rocks of Chencai group was formed in ocean island,compsed of tholeiite and cognate gabbro, Carbonatite and argillo-arenaceous clastic rocks of turbidity current deposition. It has experlenced peregional dynamo-heat flow metamorphism of amphibolite phase under middle pressure and several periods of deformation. Data of geo chemistry and isotope chronology indicated that the Wilson Cycle in south-east of China had begun in late of Meso-proterozoic era. That's to say, there existed an ocean basin between Yangzi and Cathysian terrain at that time, and there may be existed some granitic crust frag ments of the continente which were residual materials from the Tonian period on the oceanic crust. In late of Meso-proterozoic era, the depletion of oceanic crust and some related vol cano-sedimentation began. In late of Neo- proteozoic era, the terrain of Chencai ocean arc island and terrain of Shuangxiwu continental arc were pieced togather and collided, and the polymerizations between crustaL bodies resulted in the metamorphism and deformation of the rocks of Chencai group.Data of isotope geolhronology and micropaleontology showed that the diagenetic age of Chenacai proup was Meso-neo-proterozoic era, and its main body might be formed in Ste nian period.