Occurrence and Geological Genesis of Pyrites in Late Paleozoic Coals in North China

摘要

The occurrence and geological genesis of pyrites in Late Paleozoic coals of North Chi- na have been systematically studied in terms of coal petrology, coal chemistry, elemental geo- chemistry and sulfur isotope geochemistry. The results suggest that eight types of pyrite, i.e., framboida, automorphic granular, oolitic, massive, homogeneous spherical, allotriomorphic, nodular, joint- and fissure-filling pyrites can be subdivided under the microscope. Four genera- tions of pyrite are also recognized according to the shape, size, coexisting assemblage, special distribution relationship with macerals, the contents of sulfur and iron, atomic s/Fe rations and associated elements in pyrites. Sulfur in Late Paleozoic coals of North China is of diverse source as evidenced by sulfur isotope variations in the pyrites. The δ34_s values of pyrite generated at the early stage tend to be negative, and at the late stage, positive.