South China Sea Regional Heat-flow Prediction from Gravity Inversion Mapping of Crustal Thickness and Continental Lithosphere Thinning

Kusznir, Nick¹; Alvey, Andy²; Roberts, Alan²
¹Geology and Geophysics, University of Liverpool, Liverpool, United Kingdom.
²Badley Geoscience, Hundleby, United Kingdom.

The prediction of heat flow at rifted continental margins and their ocean-continent transition presents a substantial scientific and technical challenge in frontier deep-water hydrocarbon exploration. Sea-floor spreading re-orientation and ridge jumps during the Oligocene-Miocene formation of the South China Sea have led to the present complex distribution of oceanic crust, thinned continental crust, micro-continents and volcanic ridges. We determine top basement heat-flow for the South China Sea and adjacent rifted continental margins using gravity inversion mapping of crustal thickness and continental lithosphere thinning. Continental lithosphere thinning and post-breakup residual thicknesses of continental crust determined from gravity inversion have been used to predict the preservation of continental crustal radiogenic heat productivity and the transient lithosphere heat-flow contribution within thermally equilibrating rifted continental margin and oceanic lithosphere. The resulting crustal radiogenic productivity and lithosphere transient heat flow components, together with base lithosphere background heat-flow, are used to produce regional maps of present-day top-basement heat-flow for the South China Sea. We determine crustal thickness, continental lithosphere thinning factors and ocean-continent transition location for the South China Sea using a new gravity inversion method which incorporates a lithosphere thermal gravity anomaly correction (Chappell & Kusznir, 2008). Public domain free air gravity anomaly, bathymetry and sediment thickness data are used in the gravity inversion. The sensitivity of present-day South China Sea top basement heat-flow to initial continental radiogenic heat productivity, continental breakup age and oceanic lithosphere age has been examined. The techniques described above are applicable globally to all rifted continental margins.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012