贵州南部石炭纪古地磁初步研究

Teh Preliminary Study of the Carboniferous Palaeomagnetism in Southern Guizhou

一、前言近年来对中国岩相古地理研究已取得不少研究成果,对中国板块也有不少新进展,1986年国际大陆边缘地质科学讨论会中已经广泛涉及到我国南方,北方各地质时代的构造变迁和海陆迁移以及板块、推覆体的演化过程。愈来愈多的资料表明,任何一个地质时期的地质事件出现,均以全球地质背景为前提。相带的变动,生物礁滩的出现,特殊环境里各种矿产的产出,无不与当时的古气候、古纬度有关。因此,研究古地磁学,将是研究岩相古地理中应当借鉴的一个重要方面。通过古地磁学研究,能得到某些有益的启示,以补充岩相古地理研究的某些不足。

This paper deals with palaeomagnetic reconstruction of Guizhou in Southwest China. It is evident that the South China block drifted episodically northwards or southwards during its geological evolution. Being a part of the South China block, Guizhou is thought to be placed around 24°north latitude during the Late Devonian. Until well into the Early Carboniferous, the South China block continued to drift southwards to 15.1°north latitude during the Tangbagou stage, then returned northwards to 19.4°north latitude during the Xiangbai stage, migrated southwards again to 8.7°north latitude during the late Datang stage. and lastly to 7.8°north latitude during the Late Carboniferous. The block may be close to the equator during the Permian, and subsequently moved towards the southern hemisphere. It once migrated dramatically between 20°and 30°north latitude from Middle Triassic to Jurassic times. It follows that the drifting of the block may be regarded as a leading factor controlling the distribution of reefs and ore deposits, especially the bauxite deposits. Detailed magnetic study may also serve as a useful tool for palaeogeographic reconstruction.