Dissolution of biogenic carbonates: Effects of skeletal structure

Abstract

Dissolution of biogenic shallow-water carbonates exposed on deep-sea moorings indicates that skeletal structure is important for the rate of disintegration of biogenic carbonates, besides mineralogy and grain size of particles. The aragonites and high Mg-calcites used represent a wide spectrum of mineralogies and types of skeletal framework. The particles were deployed at different water depths on a mooring in the Drake Passage for 52 days. Weight loss curves for the various types of particles show the relative importance of the different structural factors for the disintegration of these biogenic carbonates. Organic coatings, intraskeletal pore spaces, and sizes and shapes of individual crystallites in the skeletons may be more important than carbonate mineralogy and particle size in cases. The presence of internal sediments, cement aggregates and natural contaminations and of diatoms incorporated during growth into carbonate skeletons, strongly influence the disintegration of the skeletal materials. The first step of particle disintegration is the selective removal of impurities. This step is analogous to a “cleaning” of specimens. It is succeeded by initial dissolution, by strong dissolution and finally by disintegration.