Organic Geochemical Characteristics of Source Rocks from Yiliekede Formation in the Intermittent Stages of Volcanic Activity in Mohe Basin

Key words: 
• source rocks

Abstract: Mohe basin is a fault basin infilled with Lower Cretaceous volcanic rock and with growth of dual structure consisting of volcanic rock and sedimentary rock. The Yiliekede group source rock in Mohe basin belongs to limnetic facies and is developed in basaltic series. The source rocks including oil shale, shale and coal. The source rocks were deposited in the same time with the basalts, and the igneous rock were formed for the volcanic lava or pyroclastic into lake water directly. Based on the analytic technique of GC and GCMS, the depositional environment, biogenetic derivation and maturity of the source rocks were discussed. The results show that the abundance of the organic material of source rock is rather high, the kerogen of the oil shale is mainly of type Ⅱ, the coal and the shale is mainly of type Ⅲ; The source rocks were not heated by the basalt magma (Ro=0.56%~0.59%), and the thermal evolution of the samples have reached low maturation stage, and just entered the oil generation threshold. Thus the source rock is a set of excellent source rock measures with much better hydrocarbon generation potential. The source rocks are deposited in an water body of strong weakly reduction. The salt of the water bowere changed between salt and freshwatertiny salt quickly. The hydrocarbon came from the mixedsource of organics from the input of aquatic organisms and terrigenous plant, and the terrigenous plant is more enough in coals. 