下扬子前中生代构造演化

下扬子具有前震旦系变质基底，自震旦纪进入板内演化。震旦纪－早古生代发育三个向ＮＥ方向打开的拗拉槽，具有典型的三段式建造序列，槽内沉积作用不同于槽间区域的沉积作用。自晚奥陶世末期到志留纪末期，下扬子转变为前陆盆地。碎屑沉积厚度逾６０００ｍ，物质来自东侧，说明东侧有一新生的造山带崛起。自晚泥盆世初期到二叠纪末期，该造山带向前陆推挤，下扬子发生ＳＮ向引张，在晚二叠世出现成熟的撞击槽。槽内发育火山岩，碎屑沉积物来自该造山带。建议称之为东海造山带。

PRE MESOZOIC TECTONIC EVOLUTION OF THE LOWER YANGTZE REGION

The Lower Yangtze region containing a pre Sinian metamorphic basement, has entered an episode of intraplate evolution since the Sinian. During Sinian Early Paleozoic, three aulacogens within the region formed with the mouths opening toward the northeast. They have typical three sector type sediment assemblages. Especially to say, the intra aulacogen sedimentation is different from the inter aulacogen. From the last stage of Late Ordovician to that of Silurian, the Lower Yangtze block evolved into a foreland basin. Debris sediments that are over 600 m thick come from an area to its east, which suggests that a later submerged orogen may have been located to the east of the block. Between the early stage of Late Devonian and the late stage of Permian, this orogen propagated toward the foreland and caused the extension of the Lower Yangtze in the S N direction. So the mature impactogen rich in volcanic rocks formed in Late Permian. Its sediments originated from the orogen which is named the Donghai Orogen.