Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Dissolution kinetics of biogenic carbonates; effects of mineralogy, microstructure, and solution chemistry

Lynn M. Walter and John W. Morse
Dissolution kinetics of biogenic carbonates; effects of mineralogy, microstructure, and solution chemistry (in AAPG annual convention with divisions SEPM/EMD/DPA, Anonymous)
AAPG Bulletin (May 1982) 66 (5): 639-640

Abstract

Previous models of early carbonate diagenesis assume mineralogy controls alteration sequence, with magnesian calcites dissolving more rapidly than aragonites. Results of this study indicate that: (1) mineralogic effects can be overridden by microstructure; and (2) dissolved magnesium enchances dissolution rates. The study determined laboratory dissolution rates of biogenic grains found in modern carbonate environments and evaluated the relative importance of grain mineralogy, microstructure, and solution chemistry by determining dissolution rates at various undersaturations in seawater and in freshwater solutions containing different amounts of dissolved magnesium. Although aragonitic grains dissolved more rapidly than low-magnesian calcites of the same grain size, most aragonites also dissolved as fast, or faster than, magnesian calcites containing 12 to 17 mole % MgCO3. Mineralogy alone, then, is not the sole control on reactivity. Dissolution rate is also affected by microstructure. Microstructure determines the amount of surface area available for dissolution and may exert greater control over reactivity than mineralogy. For example, the porous but smooth surface of an echinoid (magnesian calcite) dissolves much more slowly than aragonitic coral and gastropod grains, which have more complex microstructures. The presence of dissolved magnesium enhances rates of dissolution, but does not strongly affect the relative reactivity between different grain types. The absolute dissolution rates show a strong progressive decrease in magnesium-depleted solutions. Thus, assumption of mineralogic control over grain reactivity during early diagenesis is an oversimplification. Microstructure and solution chemistry emerge as important variables with predictive power for modeling both porosity development and diagenetic evolution within carbonate sequences.


ISSN: 0149-1423
EISSN: 1558-9153
Coden: AABUD2
Serial Title: AAPG Bulletin
Serial Volume: 66
Serial Issue: 5
Title: Dissolution kinetics of biogenic carbonates; effects of mineralogy, microstructure, and solution chemistry
Title: AAPG annual convention with divisions SEPM/EMD/DPA
Author(s): Walter, Lynn M.Morse, John W.
Author(s): Anonymous
Affiliation: Univ. Miami, Rosenstiel Sch. Mar. Atmos. Sci., Miami, FL, United States
Pages: 639-640
Published: 198205
Text Language: English
Publisher: American Association of Petroleum Geologists, Tulsa, OK, United States
Meeting name: AAPG annual convention with divisions SEPM/EMD/DPA
Meeting location: Calgary, AB, CAN, Canada
Meeting date: 19820627June 27-30, 1982
Summary: Y
Accession Number: 1983-044285
Categories: Sedimentary petrology
Document Type: Serial Conference document
Bibliographic Level: Analytic
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute.
Update Code: 1983
Close Modal

or Create an Account

Close Modal
Close Modal