南盘江坳陷及邻区海西晚期岩浆活动特征及其形成机制探讨  

Characteristics of Late Hercynian magmatic activity and its formation mechanism in Nanpanjiang depression and adjacent areas

作　　者：汪新伟[1] 韩效忠[2] 侯宇光[1] 周维博[1] 

机构地区：[1]中国地质大学,北京100083 [2]核工业北京地质研究院,北京100029

出　　处：《铀矿地质》2005年第2期72-78,共7页Uranium Geology

基　　金：中国石油化工集团股份有限公司南方勘探开发分公司项目资助。

摘　　要：南盘江坳陷及邻区海西晚期岩浆岩分布显示有从中、西部大规模玄武岩喷发→中东部中酸性岩浆活动→东南部花岗岩侵入的演化规律。其中, 在十万大山盆地以西地区的偏基性岩浆活动受北东和北西向深断裂控制明显, 尤其以此两组断裂交汇处的岩浆活动强烈, 盆地构造背景属大陆伸展裂谷环境; 在十万大山盆地以东地区为偏酸性岩浆活动, 主要受东吴运动形成的钦防造山带的控制,属大陆边缘造山带或岛弧造山带环境。岩浆活动的模式为: 早二叠世末期, 在研究区中、西部地壳强烈拉张应力作用下, 扬子板块向南东仰冲于云开地体之上, 钦防海槽关闭, 沿北东向的博白 岑溪断裂带发生陆 陆碰撞, 其动力来源可能与邻区的“峨嵋山玄武岩省”相关。海西晚期盆地的沉积特征也反映出岩浆活动的规律。Based on the distribution and petrochemistry of magmatic rocks,the techonic background of sedimentary basin and the mechanism of magmatic activity at the Late Hercynian in Nanpanjiang depression and its adjacent areas,southern China,have been studied.The results indicate:(1)The distribution of magmatic rocks shows the feature that in the middle and western part of the study area basic igneous rocks dominate,and in the middle-eastern part intermediate rocks are predominant,while in the southeastern part acid ones are developed.(2)In the area west to the Shiwandashan basin,intermediate magmatites were controlled by deep NE-striking and NW-striking faults,especially at the conjunction site of these two group faults,magmatic activity was strong;and its tectonic background can be attributed to extensional continental rift.On the contrary,in the area east to the Shiwandashan basin,intertmediate-acid magmatites were developed and controlled by Qingfang orogenic belt resulting from the Dongwu movement and its tectonic background can be identified as the orogenic belt of continental margin or island arc.(3)The model of magmatic activity has been determined as follows:at the end of Early Permian,under the action of strong tension of the crust in the middle and western part of the study area,the Yangzhi plate was obducted southeastward onto the Yunkai terrane,leading to the closure of Qingfang oceanic trough and the occurrence of continent-continent collision along the NE-trending Bobai-Chengxi fault belt.The dynamics source might be associated with“the basalt province of E-mei Mountain”adjacent to the study area,and the mechanism of magmatic activity reflected the sedimentary features of Late Hercynian basins.

关 键 词：岩浆活动 构造背景 海西晚期 南盘江坳陷及邻区 

分 类 号：P581[天文地球—岩石学]