全球早古生代造山带(Ⅲ):华南陆内造山

Global Early Paleozoic Orogens(Ⅲ):Intracontinental Orogen in South China

华南早古生代加里东期变形、岩浆、沉积等特征表现为陆内造山带特征。通过对加里东期角度不整合分布、褶皱、断裂逆冲极性等特征的分析,发现大明山、大瑶山地区EW轴向的寒武系褶皱不对称性和角度不整合空间上向北的拓展变新规律,指示晚寒武世—早奥陶世的由南向北推覆挤压可能是云开、滇—桂北越地块依次向北推挤的结果;从全球背景看,可能和华南陆块南部一些地块与冈瓦纳大陆北缘依次碰撞接触导致的远程陆内效应有关。然而,湘赣边境、桂北元宝山及越城岭地区的早古生代NE向褶皱不对称性指示向西拓展,这可能是由于华夏地块与扬子地块在晚奥陶世—早志留世沿郴州临武断裂陆内收缩挤压的结果,其全球背景可能和华南陆块顺时针旋转与冈瓦纳全面碰撞相关。总之,加里东期构造运动总体由南向北、由东向西渐新,变形强度由强到弱的特征,反映华南陆内碰撞造山事件的根本原因是其与冈瓦纳北缘碰撞的远程效应。450~420 Ma华南已经属于冈瓦纳北缘一部分。

This paper takes South China Early Paleozoic Caledonian intracontinental orogenic belt as an example, analyzing the intracontinental orogenic deformation, magmatic and sedimentary characteristics,the distribution of angular unconformity,fold-thrust belts,and subduction polarity.It was found that E-W-striking Cambrian fold asymmetry and spatial distribution of angular unconformities propagated and became younging towards the north in the Daming Mountain and the Dayaoshan area,indicating that the younging and propagation of north-directed thrusting may resulted from the seuqantially southward collision of the Yunkai block and the Diangui-North Vietanam blocks.Under the global tectonic setting,the deformation may be related to far-field intracontinental effect caused by sequential collision of some blocks in the South China block to the northern margin of Gondwana.The Yuanbaoshan and Yuechengling area in the north Guangxi,and the Hunan-Jiangxi border area developed the Early Paleozoic NE-NNE-trending folds and thrusts of which asymmetry indicates westward propagation,probably resulting from the collision of the Cathaysia block to the Yangtze block along the Chenzhou-Linwu fault in the Late Ordovician and Early Silurian.In the global view,it may be related to the clockwise rotation and comprehensive collision of the South China block to Gondwana.In summary,the Caledonian tectonic movement as a whole was sequentially propagated from south to north,and from east to west,their deformation intensity is from strong to weak toward the north or the west,reflecting that South China intracontinental collisional orogenic event is a far-field effect of its collision to the Gondwana.During about 450-420 Ma the South China block has been apart of the northern margin of Gondwana.