南秦岭勉(县)略(阳)构造混杂岩带的泥盆纪—石炭纪古海洋演化

PALAEOOCEAN EVOLUTION OF DEVONIAN - CARBONIFEROUSIN TECTONIC MELANGE ZONE OF MIANXIAN - LUEYANGIN SOUTH QINLING MOUNTAINS

南秦岭勉略构造混杂岩带是由太古宙—石炭纪不同时代的构造岩片组成的非史密斯地层区.其中,泥盆纪发育裂谷火山岩,石炭纪发育蛇绿岩、岛弧和洋壳火山岩及放射虫硅质岩.泥盆纪—石炭纪的火山岩、硅质岩常量元素、微量元素、Ce异常、稀土元素总量和轻/重稀土元素分异特征及其配分型式反映出当时勉略洋为一开放洋盆.区域地质资料分析表明,勉略洋是在早古生代后期勉略裂陷槽的基础上进一步发育而成的.该洋盆于石炭纪俯冲萎缩,在三叠纪后期最终关闭和碰撞造山.

Tectonic melange zone of Mianxian-Lueyang is a non-Smith stratigraphic region which consists of many structural slices from the Archean to Carboniferous. This region has developed rift volcanic rocks of the Devonian, ophiolite, island arc and ocean volcanic rocks, and radiolarian siliceous rocks of the Carboniferous . The features of ordinary, trace and rare earth elements of the volcanic rocks and siliceous rocks suggest the existence of an open ocean during the Devonian and Carboniferous. This ocean basin was formed by further breaking off on the basis of the rift during the Palaeozoic, subducted in the Carboniferous , and closed and collided in the Late Triassic.