湘中南晋宁期和加里东期构造线走向变化成因

POTENTIAL GENESIS OF THE TRENDING CHANGES OF JINNING PERIOD AND CALEDONIAN STRUCTURAL LINEAMENS IN MIDDLE-SOUTHERN HUNAN

湘中南晋宁期和加里东期构造线走向横向上存在显著变化,通道—溆浦—安化—桃江一线晋宁期与加里东期构造线呈向北西凸出的弧形弯曲;湘东浏阳—川口一带晋宁期构造线自北而南由东西向转为北东—北北东向,加里东期构造线在湘南九嶷山地区和彭公庙—汝城一带为东西向,在都庞岭—塔山隆起带以及高挂山—关帝庙隆起带呈北东—北北东向,在湘中大乘山—龙山一带呈东西向。地质与地球物理资料显示湖南境内钦杭结合带与扬子陆块分界可能沿南桥—新化—隆回—苗儿山一线,自东向西由东西向转为北北东向;与华夏陆块分界可能沿川口—常宁—双牌一线,呈北东向。通过与区域挤压应力方向结合,上述构造边界走向可以较好地解释湘中南地区晋宁期和加里东期构造线方向的若干横向变化特征。

There existed visible lateral variations of the Jinning Period and Caledonian structural lineaments in middle-southern Hunan. The Jinning Period and Caledonian structural lineaments in Tongdao-Xupu-Anhua-Taojiang area showed an arc bulging to northwest. The Jinning Period lineaments trend in Liuyang-Chuankou area of eastern Hunan changed from EW to NE-NNE from north to south. The Caledonian structural lineaments in Jiuyishan area and Penggongmiao-Rucheng area in southern Hunan took on EW-trend, while in Dupangling-Tashan uplift and Gaoguashan- Guandimiao uplift took on NE-NNE-trend, and in Dachengshan-Longshan area in middle Hunan took on EW-trend. Geological and geophysical data suggested that the boundary between Qinzhou- Hangzhou juncture and Yangtze block in Hunan Province might extends along Nanqiao-Xinhua- Longhui-Miaoershan with change of EW- to NNE-trend from east to west, and the boundary between the juncture and Cathaysian block extends along Chuankou-Changning-Shuangpai with NE-trend. Combined with regional compressional stress field, the trend of the boundaries can be taken to explain the dynamic mechanisms of the lateral changes of Jinning Period and Caledonian structural lineaments.