SHRIMP U-Pb Ages of Detrital Zircons: Discussions on Provenance Control and the Red River Capture

Xu, Qiang; Zhu, Weilin; Wang, Yingmin; Li, Dong; Wang, Yongfeng; Zhuo, Haiteng

A huge Red River submarine fan has been discovered recently in Upper Miocene along the northwestern margin of the South China Sea. To further explore the provenance of the submarine fan and the controversial issue of the Red River capture, SHRIMP U-Pb ages of detrital zircons have been measured using the samples recovered from the well S which intersected the fan. The result shows:

1. Six main age intervals have been recognized in the zircon grains of the Red River submarine fan, which are 230-300Ma,400-500Ma,700-1000Ma,1700-1900Ma,2400-2500Ma and ~2700Ma, respectively. The age distribution spectrum of zircons displays a good similarity with the Red River drainage area. It thus can be inferred that the zircons between 230-300Ma are mainly from the Khorat Plateau - Kon Tum block. Zircons of 400-500Ma and 1700-1900Ma are linked with the Songpan-Ganze block, and the 700Ma-1000Ma zircons are considered to be from the Yangtze Craton. Zircons with the age of 2400-2500Ma and ~2700Ma are related with the ancient basement of Yangtze Craton within Songpan-Ganze block.

2. The zircon grains of the Red River submarine fan, including the ages of 400-500Ma, 1700-1900Ma and older than 2.4 Ga, are proved to exist in the Songpan-Ganze block. It indicates that the Red River had once extended into the Songpan-Ganze block, holding a far more lager drainage area than today. The general decrease of the drainage area today implies that the Red River be once captured.

3. The samples of zircon grains are mainly from the late-Miocene Red River fan, suggesting the Red River had not been captured by the Late Miocene. Once took place, this capture would be inevitable to cause a dramatic decrease in the drainage area and the according loss of the sediment supply, both of which would be recorded in the basin fill. Subsequently, the timing of the Red River capture can be identified through the careful investigation on the evolution history of the Red River depositional systems, as well as the calculations of parameters such as the sediment flux or total volume.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013