Constraints on Cation Order in Calcium-rich Sedimentary Dolomite |
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| Authors: | Richard J Reeder |
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| Institution: | (1) Department of Geosciences, State University of New York at Stony Brook, Stony Brook, NY, 11794-2100, U.S.A. |
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| Abstract: | Most sedimentary Ca-rich dolomite in pre-Holocenerocks is known to exhibit a fine-scale modulation inTEM images, reflecting a domain structure of which onecomponent is a low-symmetry variant of dolomite. Thevarious structural models proposed for thelow-symmetry component involve Ca–Mg order patternsthat are different from that in dolomite. Caution istherefore required for interpretation of X-raydiffraction data, which average over the entirestructure. The average structures of two Ca-richdolomites having a structural modulation are refinedusing single-crystal intensity data. The resultsindicate a poor fit using a dolomite model, which isconsistent with the findings from TEM and electrondiffraction indicating that one component of thedomain structure is different than dolomite. Resultsalso indicate that average model A and B cation siteshave mixed Ca–Mg occupancy, which provides someconstraints on possible models for the low-symmetrydomains. |
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| Keywords: | dolomite crystal structure dolomite x-ray diffraction dolomite electron microscopy dolomite |
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