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Dolomite crystal architecture; genetic implications for the origin of the Tertiary dolostones of the Cayman Islands

Brian Jones
Dolomite crystal architecture; genetic implications for the origin of the Tertiary dolostones of the Cayman Islands
Journal of Sedimentary Research (March 2005) 75 (2): 177-189

Abstract

Dolostones in the Cayman Formation on Grand Cayman and Cayman Brac, which are the product of two and possibly three phases of dolomitization, are formed of very small (<100 mm) but architecturally complex dolomite crystals that are characterized by planar and non-planar boundaries, corrosional internal discontinuities, oscillatory low-Ca calcian dolomite (LCD) and high-Ca calcian dolomite (HCD) zoning, and syntaxial (?) overgrowths. The dolomite over-growths, which grew on earlier formed but corroded rhombs, increased crystal size and modified crystal shape and, hence, caused significant textural modifications. The size and shape of the overgrowths that developed preferentially on those crystal faces that formed the walls of micropores was controlled by the competition for growth space with neighboring crystals. Interpretation of this textural information suggests that the development of planar and non-planar dolomite boundaries crystals is probably related to critical supersaturation levels rather than critical roughening temperatures. The recognition that individual dolomite crystals, irrespective of their size, may be architecturally heterogeneous carries important implications for dolomite genesis. Many interpretations of finely crystal-line dolostones, for example, have tacitly assumed that they formed through one phase of dolomitization. In the Cayman Formation, however, dolomite crystals as small as 10 mm are characterized by internal heterogeneities that record their development through multiple, time-separated growth phases. Any model developed to explain dolomitization must take this into account. The interpretation of chemical data, for example, must consider the multiple-stage development of the dolostones that is evident from their internal zoning and discontinuities.


ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 75
Serial Issue: 2
Title: Dolomite crystal architecture; genetic implications for the origin of the Tertiary dolostones of the Cayman Islands
Author(s): Jones, Brian
Affiliation: University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada
Pages: 177-189
Published: 200503
Text Language: English
Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States
References: 40
Accession Number: 2005-030977
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., sketch map
N19°15'00" - N19°45'00", W81°30'00" - W79°45'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 200511
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