Pb, Sr isotopes in organic matter of Lower Tertiary hydrocarbon source rocks in Liaohe Fault Depression

The Pb, Sr isotopic compositions in organic matters (kerogen and soluble or ganic matter) of Lower Tertiary hydrocarbon source rock in Liaohe Fault Dep ression is first reported. There is a great variable rang of Pb isotopic co mpositions in kerogen, Pb-206/Pb-204 = 17.488-18.656, Pb-207/Pb-204 = 15.38 8-15.692, Pb-208/Pb-204 = 37.656-37.484. And soluble organic matters have a very stable Pb isotopic composition, that is Pb-206/Pb-204 = 17.424-17.601 , Pb-207/Pb-204 = 15.376-15.448, Pb-208/Pb-204 = 37.620-37.870. Sr isotopic composition varies in the range of 0.747 59-0.716 79 in kerogen and of 0.7 09 67-0.747 59 in soluble organic matters that have a great range. It is sh own that mantle fluid can influence organic matters and make them form hydr othermal hydrocarbon in the geoglogic environment of rift basin.