Geochemistry of the Upper Precambrian and Lower Cambrian Black Shales From the Phjonnam Depression

Thirty two samples from the Upper Precambrian and Lower Cambrian deposits of the Phjonnam depression, Sino-Korean Shield, have been analyzed for 43 chemical elements by X-ray fluorescence, atomic-absorption and instrumental neutron-activation methods. Organic carbon in black shales was established to be accompanied by the same elements as in sapropelic mud of the Black Sea Holocene. The alternative geochemical association brought into sediment together with well homogenized aleuropelite material, reflects the integral composition of vast provenances with heterogeneous structure. Two geochemical associations, which are common with the Black Sea sapropelic mud, were also recognized in Cambrian black shales in different regions of Eurasia. High-carbonaceous deposits of the Phjonnam depression contain all elements of organophilic association, concentrations of Mo, U, As, Sb, Ni, and Ag in particular. Only in the case of extremely high selective concentrations of some elements of organophilic association in any region, one may assume the contribution of other source than marine water.