Abstract:

The study of deep seated structure and tectonics in the midupper Yangtze block is important for understanding the genesis, migration and gathering of oil and gas, the conservation of structures, and the occurrence and distribution of mineral resources, which are related to the formation and evolution of the midupper Yangtze block. By manipulating geophysical data in detail and combined with the surface geology, we found and collated an EW trending Tectonic Zone (EWTZ) from Chishui in Guizhou Province to Lianyuan in Hunan Province and presented the geological and geophysical evidences for the existence of the EWTZ. The results showed that the EWTZ was an important boundary tectonic unit between the northern tectonic block and the southern one in the midupper Yangtze and HunanGuangxi regions since the Proterozoic or earlier. The findings suggested that the EWTZ has multiphase evolution characteristics from basement rock to cover, as well as a diachronous migration trend from south to north. The formation and evolution of the EWTZ may probably be divided into two stages: the Late Precambrian period and the post Late Cretaceous period.

Key words: basement structure, aeromagnetic anomaly by reduced to the pole, gravity anomaly, ChishuiLianyuan EW trending tectonic zone, midupper Yangtze block