Indosinian Hydrocarbon Accumulation in South China:A Re-Os Isotope Constrain

Rhenium-Osmium isotope system is a new and challenging method used to determined the hydrocarbon accumulation and date of desdtruction. This paper reports a Re-Os approach to date the hydrocarbon accumulation and destruction time of the Majiang paleo-oil pool,one of the largest paleo-oil reservoirs in South China. The Re and Os contents in the bitumen vary from 41.5×10-6 to 642×10-6 and 0.21×10-6 to 12.15×10-6,respectively. Their 187Re/188Os ratios are characterized by high and variable range of 270.90 to 4 074.99,while their 187Os/188Os ratios are moderately radiogenic,ranging from 0.340 0 to 3.655 7. The Re-Os model ages for the bitumen vary between 28 Ma and 144 Ma,with an average of ~85 Ma. With conbination of the documented geological researches,the paper suggests that the Majiang hydrocarbon deposit should be finally accumulated at ~144 Ma of Indosinian to Early Yanshanian period,and destroyed at ~85 Ma of Late Yanshanian period.