Clay Polymerization in Carbonate Rocks: A Silicification Reaction Defined

Abstract
A carbonate rock silicification reaction has been defined and shown to be dependent on the presence of clay in the host rock. Introduction of silica in soluble form(s) serves to polymerize the clay fraction, forming a continuous three-dimensional network. This siliceous network (polymer) can be separated from the rock by leaching away the carbonate minerals. Laboratory silicification of argillaceous carbonate rocks under controlled conditions has served to define critical variables.Early studies were limited to argillaceous carbonate rocks from the Devonian Cedar Valley formation in eastern Iowa. Similar results have been obtained with carbonate rocks from the Devonian Chaffee formation in south-central Colorado. Some of the rocks in the latter formation have been silicified in nature, and yield siliceous polymers on acid leaching identical to those formed by silicification in the laboratory.The reaction defined is suggested to be common in natural diagenesis of argillaceous rocks, clay-rich sedimentary material, and soils.In the case of argillaceous carbonates this reaction affects physical properties of the rock which control processes involved in petroleum migration, ore-metal transfer, rock leaching and all diagenetic reactions that involve solution transfer.

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