论海南、广东地体

Some Aspects of the Hainan and Guangdong Terranes

本文系“广东省石炭纪岩相古地理及沉积、层控矿产远景预测”研究课题成果之一。笔者认为这些成果对研究我国东南沿海大地构造格局及其演化、岩相古地理展布以及矿产分布规律都有重要的参考价值。借以引起国内外学者的关注。通过实际工作和资料分析,笔者认为在石炭纪,广东大陆和海南岛分别属于二个联合地体。前者属华南地体的一部分(许靖华,1987),它是在加里东褶皱的基础上形成的,在石炭系沉积前(实际上古生代早期就开始),它与扬子地体已经形成了一个联合地体。后者包括了海南岛主体部分及其南端(九所—陵水断裂之南)。本文仅讨论石炭纪时的二个联合地体。地矿部南京地矿所李耀西、张瑛及成都地矿所潘杏南。

The Carboniferous Guangdong continent and Hainan Island are believed to be two distinct composite terranes based on the following main features. (1)They have significantly different sedimentary formations. During the Permian Period. the Guangdong continent was an epeiric sea where the sediments dominated by the shallow-water carbonate rocks were deposited. whereas the Hainan Island was then a marginal sea where the deepwater sediments dominated by mudstones and siliceous mudstones were deposited. (2)There was no transitional facies between the Guangdong continent and Hainan Island. (3)The Hainan Island was isolated by the rifts all around: the Qiongzhou Channel rift to the north; the Yingge Sea rift to the west(The rift stretched northwestwards to the Red River rift in Viet Nam.), and the Southeast Qiongzhou rift to the southeast. (4)The palaeotectonics of the Carboniferous sediments on the Guangdong continent tend to be controlled by a series of the NE-trending rifts, whereas those on the Hainan Island by the EWtrending rifts. (5)The faunal provinces vary greatly. The fossils are very rich in vaiious horizons of the Guangdong continent, but very rare in those of the Hainan Island. There exist, on the Guangdong continent, blue-green algae and green algae which are absent on the Hainan Island. On the other hand, there occur, on the Hainan Island. the fossils Fusella Xeospirifer as well as the Cambrian Xystridura which are also absent on the Guangdong continent. (6)After the Carboniferous Period. the Guangdong continent was compressed as a result of the NE-trending collision between the Pacific and Eurasian Plates resulting in intense magmatism and contact metamorphism. whilst the Hainan Island was compressed due to the collision of the NS-trending terranes leading to the regional metamorphism and strong silicification and schistositization. (7)The differences between the two terranes may also be indicated by the pre-Carboniferous sedimentary records. (8)It can be seen. from the palaeomagnetic data. that the Hainan Island once drifted from the south to the north and collided with the Guangdong continent.