Synorogenic clay rocks: Specifics of bulk composition and paleotectonics

Abstract

The paper is devoted to the specifics in the chemical composition of synorogenic clay rocks in various environments: the Ural foredeep, Olyutorskii terrane, Dnestr pericratonic trough, Indus-Gang trough, etc. The compositions of the rocks are plotted in conventionally utilized discriminant paleotectonic diagrams. It is demonstrated that the bulk composition of such rocks, which were formed under active tectonic conditions typical of the collisional evolutionary phase of mobile belts, reflects the nature of the rock assemblages produced during both the divergent and the convergent (including collisional) phases. Their mean composition is the closest to PAAS as an integrated parameter of the average composition of the continental crust. The materials presented in the publication suggest that data on the bulk composition of clay rocks shown in conventionally utilized discriminant diagrams, such as SiO 2 -K 2 O/Na 2 O, K 2 O/Na 2 O-SiO 2 /Al 2 O 3 , are insufficient to reproduce the tectonic environments in which these rocks were formed.