Source of carbonate and origin of zonation in pyritiferous carbonate concretions: evaluation of a dynamic model

Abstract

Spheroidal, diagenetic concretions in the Toarcian black shales of the Jet Rock (Yorkshire, United Kindom) are predominantly calcite with a microspar texture. Pyrite occurs within the concretions, but its concentration increases to the margins to form a sharply-defined massive pyrite rim. This striking zonation can be described by a dynamic model. The mineral zonation of the concretions is spatially rather than temporally controlled, and successive zones do not represent changes in porewater composition during burial. -from Authors