Abstract:

Abstract:  It is commonly accepted that tectonic regimes underwent a tremendous change, during the Mesozoic, from the Tethys tectonic domain to the Pacific tectonic domain in South China, although the timing and geological effects of such a change have been debated. This paper identified two generations of superimposed folds that widely develop in Indosinian to early Yanshanian tectonic layer (DJ12) in South China, and it is found that the earlier generation of folds is well zonated in WE and the later one is distributed in NNE. Based on the analysis of stratigraphic contact relationship and isotopic dating results of Early Mesozoic igneous rocks, it is considered that these two fold generations clearly record two phases of Early Mesozoic tectonic compression in South China: the nearly WE trending fold zones resulted from farfield effect of Indosinian collision or accretion occurred along the northern and southern margins of the South China Block, while the NNEtrending folds were originated from low angle subduction of the paleoPacific plate under the South China Block, which occurred in the time of Middle to Late Jurassic around (170±5) Ma. Crustal thickening caused by these two compressions induced melting and emplacement of Triassic and Late Jurassic granites particularly developed in the Cathaysian Block. The recognition of the two superimposed fold generations in South China is key to understanding the change from the Triassic continentcontinent collisionrelated tectonic system to the MiddleLate Jurassic subductionrelated tectonic system.

Key words:

Key words: South China Block; superimposed fold; Indosinian collisionrelated fold system; Early Yanshannian subductionrelated fold system; tectonic regime change