新元古代—早古生代华南裂谷系的格局及其演化

摘要

本文运用地层、构造与地质事件的综合研究方法,对新元古代—早古生代华南裂谷系的格局及其演化进行了研究.该裂谷系发生于晋宁期造山(约820 Ma)后不久的青白口纪晚期(约815 Ma),有皖浙赣堑垒带、湘桂台阶式斜坡带和南华裂谷海盆3个部分.皖浙赣堑垒带由“两谷两隆”组成,火山活动强烈,消亡于“青白口纪”末(约780 Ma).湘桂斜坡带拥有武陵(红板溪)、雪峰(灰板溪)和钦杭西段(黑板溪)3个台阶式斜坡.南华裂谷海盆以南岭中央海盆为核心,外侧有武夷、岭南两个水下裂陷块体和闽中裂谷等.海盆于志留纪时由东向西逐渐闭合造山,以“北贴西拼”为主要运动方式,形成了复杂的复合构造格局.由于南岭与岭南块体不同步的向西推移并南北贴合形成了河池-定南挤压转换式拼接带,出现了南岭东西向构造带的雏形.钦杭裂谷是华南裂谷系的主干和主要海水通道,其南端的钦州残留裂谷海槽于中二叠世末才宣告封闭.华南裂谷系的形成发展是华南地史上的一个重大事件,对后期地质构造以及岩浆成矿活动都具有重要的约束作用.%This paper deals with the framework and evolution of the Neoproterozoic-Early Paleozoic South-China Rift System based on the stratigraphy, structure and geologic events, etc. The rift occurring in the Qingbaikou Period (ca 815 +Ma) shortly after the Jinning Orogeny (about 820 +Ma) consists of Anhui-Zhejiang-Jiangxi graben-horst belt, Hunan-Guangxi step slope belt and South-China rifting ocean basin. The graben-horst belt is composed of "double upwarpings and double valleys" accompanied with intensive volcanic activities, maintained at the end of Qingbaikou Period (about 780 +Ma). The step slope belt is composed of three step slopes, namely; Wuling (red Bnaxi) , Xufeng (gray Banxi) and west section of Qinzhou-Hangzhou belt (black Banxi). South-China riftmg ocean basin takes the Nanhng central ocean basin as the core, surrounded by the Wuyi and Lingnan rifting blocks at underwater and the central Fujian rift valley along the outer rim. During the Silurian, the basin was gradually closing from east to west to form mountains in the movement form of "affixed to the North and matched to the West" , resulting in the complex structural framework. The asynchronous westward movement of Nanling and Lingnan blocks and their integration formed a Hechi-Dingnan compressed transform suture zone, which constitutes the primary framework of Nanling east-west-trending tectonic belt. The Qinzhou-Hangzhou rift is the main branch and water channel of South-China Rift system, while the Qinzhou residual rift trough in the south was not closed until end of middle Triassic. The formation and development of South-China rift system was a major event in the geological history of South China and played an important restriction on later structure and magmatic metallogenesis.