Title: Geochemical Characteristics and Origins of the Lower Cambrian Source Rocks from the Southern Guizhou Depression,SW China
Abstract: The Lower Cambrian source rock samples from three typical profiles in the southern Guizhou Depression were analyzed for TOC values,δ13C values,Tmax temperatures,potential generation,and biomarkers using Rock-Eval,GC,GC-MS to elucidate the geochemical characteristics and its origin.The results show that the Lower Cambrian black shales in the southern Guizhou Depression are regional marine excellent source rocks with depth of 50-150m,and have the TOC values of 0.13%-15.40%,average 3.31%(n=169);the kerogens of the source rocks have the δ13C values of-35.79‰——29.88‰,average-32.85‰(n=35),and the kerogen macerals are mainly sapropelinites;the values of the marine vitrinite reflectance of the kerogens are 1.95%-3.96%,and the values of the equivalent vitrinite reflectance are 2.02%-3.47%;the distribution shapes of the n-alkanes are mainly single peak,and the maximum peak carbon are mainly C22,the C30 hopane and C27ααα20R regular sterane are abundant,the regular steranes are mainly C27C29C28,the Pr/Ph values are 0.27-0.62,the source rocks have relative high abundance of gammacerane and dibenzothiophene,the OEP values are 0.82-1.11,C31 homohopane 22S/(22S+22R) have values of 0.56-0.63,average 0.59;the source rocks are generally characterized by enrichment in light REE,Ba,Mo,V and U element,relative strong negative anomaly of Ce element,relative strong positive anomaly of Eu element and relative high ratio of U/Th.In summary,the Lower Cambrian marine source rocks in the southern Guizhou Depression have a wide distribution with a thickness of from tens of meters to hundreds of meters,the source rocks have high TOC values,are excellent for organic matter type,and have a post-maturity.It is the product which is jointly controlled by high paleo-productivity and anoxic environment.It can provide abundant organic matter for hydrocarbon generation in the southern Guizhou Depression.
Publication Year: 2012
Publication Date: 2012-01-01
Language: en
Type: article
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