Content And Implication Of Radioactive Elements In Marine Source Rocks Of Lower Paleozoic In Upper Yangtze Region

Helium is an indispensable material in national defense industry,precision manufacturing,cryogenic superconducting and other high-tech fields,but most of our helium depends on imports.The evaluation of helium source rock resource potential can not only enrich and improve the helium genesis theory,but also have important significance for solving the helium energy demand in China.In this paper,using the methods of elemental geochemistry and mineralogy,the distribution characteristics of U and Th,enrichment factors and helium generation potential of Paleozoic marine source rocks in Sichuan Basin and its surrounding areas are studied.The following results and understandings are obtained:Using principal component analysis and cluster analysis,combined with the distribution characteristics of U and Th and enrichment control factors,the study shows that U is mainly enriched in the deep-water shelf environment with high productivity and organic matter content,and has a strong positive correlation with Ni,Mo and TOC.This is because the enrichment of U is mainly affected by the sedimentary environment,and it is easy to form a complex with organic matter in the reductive environment.Th is enriched in clay minerals,heavy minerals,feldspar minerals and rare earth elements,indicating that the enrichment of Th is different from that of U,which is mainly affected by the supply of terrigenous debris.According to the decay principle of uranium and thorium,the volume method is used to calculate the helium generation potential of shales in Sichuan Basin and its surrounding Lower Cambrian and Wufeng Formation-Longmaxi Formation,which are230.82×10~8m~3and 172.43×10~8m~3,respectively,with good helium generation potential.