The intensity evaluation of the hydrothermal sedimentation and the relationship with the formation of organic-rich source rocks in the Lower Cambrian Niutitang Formation in Guizhou Province, China

Abstract

ABSTRACTA synthetical study was carried out on the relationship between the hydrothermal sedimentation and the formation of organic-rich source rocks in the Lower Cambrian Niutitang Formation in Guizhou Province, China. Analysis of the high trace elemental contents showed that the V/Sc-V/Cr diagram can be used to distinguish the hydrothermal sediments from normal marine sediments. Cr/Sc ratios can quantitatively evaluate the intensity of hydrothermal sedimentation on account of the positive correlation between the ratios with enrichment factors (EFs) for As, Sb and others. The relationship between Cr/Sc ratios and TOC content illustrated that (1) there was a positive linear correlation between them under the low intensity of hydrothermal activities (Cr/Sc<20), and the enrichment and preservation of organic matters were obviously dominated and potentiated by the hydrothermal sedimentation; (2) The hydrothermal sedimentation was one of the most essential factors influencing the enrichment and preservation of organic matters amidst the medium condition (20< Cr/Sc <300); (3) in the high condition (Cr/Sc > 300), the higher the hydrothermal intensity, the less the enrichment and preservation of organic matters, in other words, it is not conducive to the formation of organic-rich source rocks.