The organic matter-rich strata of the Yurtusi Formation of Lower Cambrian are wildly spread and steady in the Tarim Basin, in which cherts are developed, companied with phos-phorite. Al/(Al+Fe+Mn) ratio and Si/(Si+Al+Fe) ratio of cherts range from 0.0023 to 0.0046 and 0.965 to 0.98, respectively, suggesting that cherts are formed in submarine hydrothermal activity and far away from terrestrial. Trace elements, such as As, Hg, Pb, Zn, Cu, Co, P, V, Ba, etc., are markedly rich in organic matter-rich sedimentary rocks of which Ba/Sr ratios are between 21.2 and 158.1. Compared with modern hydrothermal sediments, their Ba/Sr ratios are similar, it in-dicates that the organic matter-rich strata have the geochemical feature of submarine hydro-thermal sediments. The total content of rare earth elements (SREE) in cherts is from 8.81 to 56.682 mg/g, on average 31.41 mg/g and the SREE of cherts is between continental margin cherts and abyssal cherts. The LREE/HREE ratio of cherts varies from 1.01 to 3.56, which re-veals the characteristics of hydrothermal sediments. There is positive correlation between the total organic content (TOC) and Ba/Sr ratio which is geochemical index of submarine hydro-thermal activity, which indicates that the submarine hydrothermal activity obviously influences the richness of organic matter in the Yurtusi Formation.
