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Book Chapter

Relationship between Dolomite Nonstoichiometry and Carbonate Facies Parameters

By
David N. Lumsden
David N. Lumsden
Memphis State University, MemphisTennessee 38152
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John S. Chimahusky
John S. Chimahusky
Pomona College, Claremont, California 91711Union Oil Research CenterBrea, Cahfornia 92621
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Published:
January 01, 1980

Abstract

Two hundred ninety carbonate rock samples from nearly all pre-Cenozoic periods, from widely scattered North American sites, representing all of Dunham's carbonate rock types, and containing 5%–100% ordered dolomite in the carbonate fraction were analyzed for a possible relationship between dolomite nonstoichiometry (expressed as mole percent CaCO3) and pétrographie parameters and stratigraphie position. Dolomite composition ranged from 49.3 to 57.3 mole percent CaCO3, with modes from 50.0% to 52.0% and 54.0% to 56.0%. Data indicate that dolomite nonstoichiometry is not related to insoluble residue, porosity, rock type, percentage of crinoid fragments, recrystallization (dolomite crystal size), and percentage of dolomite in the carbonate fraction in dolomitized limestones. A general trend toward more nearly stoichiometric composition with age is obscured by local effects. Crystalline dolomites tend to be more nearly stoichiometric and less variable in composition (mode 50.0%–51.0% CaCO3) relative to dolomicrites (modes 51.0%–52.0% evaporitic; 54.0%–55.0% nonevaporitic) and dolomitized lime mudstones (modes 51.0%–52.0% evaporitic; 55.0%–56.0% nonevaporitic). Evaporite-related dolomite is almost invariable near stoichiometric or calcium depleted. Open-marine and stoichiometric, evaporite-related dolomites are products of syndepositional dolomitization; nonstoichiometric nonevaporite dolomite is syndepositional to early diagenetic; and crystalline dolomite is middle to late diagenetic.

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Contents

SEPM Special Publication

Concepts and Models of Dolomitization

Donald H. Zenger
Donald H. Zenger
Pomona College, Claremont, California
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John B. Dunham
John B. Dunham
Union Oil Research Center, Brea, California
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Raymond L. Ethington
Raymond L. Ethington
Ethington, University of Missouri-Columbia
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SEPM Society for Sedimentary Geology
Volume
28
ISBN electronic:
9781565761582
Publication date:
January 01, 1980

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