| PDF: | |
| Time: | 2012 |
| Journal: | Earth Science(Journal of China University of Geosciences) |
| Volumn: | 37 |
| Issue: | 4 |
| Pages: | 654-666 |
| Type: | EI |
| Author: | Jingfu Wu,Gongcheng Zhang,Pujun Wang,Xiaojun Xie,Shegnbiao Hu,Jiafu Qi. |
Abstract: | An important tectonic event and associated unconformity surface occurred in deepwater area of the Pearl River Mouth basin,South China Sea.Research results indicate:(1)The 23.8Ma tectonic events is the convert face of Cenozoic tectonic evolution in ZhuⅡdepression of the basin,which divides the Paleogene syn-rifting stage and Neogene post-rifting stage.In the former,the basin-forming mechanisms are dominated by the stretching and strike-slip faults systems,however,in the later, faulting and geothermal effect(late in geothermal effect primarily)control the basin evolution.(2)The 23.8Ma tectonic events resulted in great change in basin sedimentary filling.Through the analysis of trace elements and isotope,the sediment provenance comes from the southeast coastal granite materials before the 23.8Ma,but from the east of the Qinghai-Tibet plateau and the Yunnan-Guizhou plateau after 23.8Ma.At the same time,the slope-break surface jumps from south to north in the Baiyun depression,and sedimentary facies change also from shallow continental shelf to deepwater slop environments.(3)The 23.8Ma tectonic events is a transferring surface of basin geothermal system.The quantitative restore of typical drilling thermal history shows geothermal gradient obviously changes at the 23.8Ma.Through the thermal history inversion in deepwater area of the Pearl River Mouth basin,geothermal gradient rising process occur during the Paleogene,indicating the basin underwent extensional process,and the geothermal gradient falls clearly after 23.8Ma,indicating the basin underwent a geothermal subsidence process.(4)The 23.8Ma tectonic events reveals a great change in volcanic activity,the single ingredient of large basaltic magma eruption gradually strengthened before the 23.8Ma,and the eruption gradually weakened after the surface.A dynamic model of the 23.8Ma tectonic events is established.The mantle diapir from the asthenosphere flowing is regarded as the power source for the South China Sea spreading.The 23.8Ma tectonic events resulted from the jumping of the South China Sea spreading and change in mantle diapir possibly related with the deep magma escaping. |