THE THERMAL STRUCTURE OF MAIN SEDIMENTARY BASINS IN THE NORTHERN MARGIN OF THE SOUTH CHINA SEA

Geothermal study,for main sedimentary basins of the northern margin of the South China Sea,reveals that the distribution of temperature at depth is different.Especially,the constitutions of heat flow among these basins are not uniform with respect to each other.Calculation shows that in Preal River Mouth basin the contribution of crustal heat flow is lower than 25% and decreased by degrees from margin to sea.In Yinggehai basin,the contribution of crustal heat flow is lower than 30% and increased by degrees along the northeast direction.In Beibuwan basin,the contribution of crustal heat flow varies between 38% and 42%.The results suggest that the instability of thermal structure in this region can be attributed to the thinning of marginal crust and the up flowing of hot material of asthenosphere.