Lanthanoids, Actinoids, and Mineral Assemblages in Bitumen of the Siberian Platform

摘要

The basement rocks and lower section of the sedimentary cover of petroliferous basins are characterized by an abundance of solid carbonaceous material that corresponds to anthraxolites, kerites, and asphaltites in terms of physical properties. It is substantially enriched in lithophile elements. For example, the contents of Th, U, Y, and REE in bulk samples of kerites (40-70 mg) amount to 6.2-1.0, 0.072-0.015, 0.17-0.013, and 9.5-19.5%, respectively (ICP-MS data). In contrast to bitumen, oils are sharply depleted in these elements (n • 10~(-5)-n • 10~(-7)%). However, they are notably enriched in chal-cophile elements (Hg, As, Se, Sb, Ag, Au, and others), the concentrations of which are two or three orders of magnitude higher as compared to their clarke values in the upper crust. The difference in the accumulation mode and the contents of metals in the resinous-asphaltene oil components and the solid bitumens suggest that the latter compounds are not the products of oil transformation. The solid bitumens are formed as a result of the delamination and breakdown of the deeply reduced C-O-H-Me system in the upper zones of the consolidated crust during changes in thermodynamic migration conditions (T= 300-60℃; P < 2 kbar).