Polynesia). In Proceedings of the Fifth International Coral Reef
Congress. Tahiti, Vol. 3, pp. 263–269.
Purser, B. H., and Schroeder, J. H., 1986. The diagenesis of reefs:
a brief review of our present understanding. In Schroeder,
J. H., and Purser, B. H. (eds.), Reef Diagenesis. Berlin: Springer,
pp. 424–446.
Purser, B. H., Brown, A., and Aïssaoui, D. M., 1994. Nature, origins
and evolution of porosity in dolomites. Dolomites: International
Association of Sedimentologists. IAS special publication, 21,
pp. 283–308.
Reid, R. P., and Macintyre, I. G., 1998. Carbonate recrystallization
in shallow marine environments: a widespread diagenetic
process forming micritized grains. Journal of Sedimentary
Research, 68, 928–946.
Repellin, P., 1977. Contribution à l’étude pétrologique d’un récif
corallien: le sondage “Colette”, Atoll de Mururoa (Polynésie
Française). Cahiers du Pacifique, 20, 1–209.
Robbins, L. L., and Ostrom, P. H., 1995. Molecular isotopic and
biochemical evidence of the origin and diagenesis of shell
organic material. Geology, 23, 345–348.
Rougerie, F., 1995. Nature et fonctionnement des atolls des
Tuamotu (Polynésie Frangaise). Oceanologica Acta, 18, 61–78.
Rougerie, F., and Wauthy, B., 1986. Le concept d’endo-upwelling
dans le fonctionnement des atolls-oasis. Oceanologica Acta, 9,
133–148.
Sandberg, P. A., 1984. Recognition criteria of calcitized skeletal and
non-skeletal aragonites. Palaeontographica Americana, 54,
272–281.
Shinn, E. A., 1969. Submarine lithification of Holocene
carbonate Sediments in the Persian Gulf. Sedimentology, 12,
109–144.
Scherer, M., 1986. Diagenesis of aragonitic sponges from Permian
patch reefs of southern Tunisia. In Schroeder, J. H., and Purser,
B. H. (eds.), Reef Diagenesis. Berlin: Springer, pp. 291–310.
Schroeder, J. H., 1972. Fabrics and sequences of submarine carbonate cements in Holocene Bermuda cup reefs. Geologische
Rundschau, 61, 708–730.
Walter, L. M., 1985. Relative reactivity of skeletal carbonates during dissolution: implications for diagenesis. In Schneidermann,
N., and Harris, P. M. (eds.), Carbonate Cements. Tulsa, OK:
Society of Economic Paleontologists and Mineralogists. SEPM
special publication, 36, pp. 3–16.
Werner, U., Blazejak, A., Bird, P., Eickert, G., Schoon, R., Abed,
R. M. M., Bisset, A., and de Beer, D., 2008. Microbial photosynthesis in coral reef sediments (Heron Reef, Asutralia). Estuarine,
Coastal and Shelf Science, 76, 876–888.
Cross-references
Antecedent Platforms
Aragonite
Atolls
Beach Rock
Calcite
Calcrete/Caliche
Dolomitization
Emerged Reefs
Micrite
Mururoa Atoll
Oil and Gas Reservoirs and Coral Reefs
Palaeosols
Porosity Variability in Limestone Sequences
Stable Isotopes and Trace Elements
Submarine Lithification
DOLOMITIZATION
Peter Flood
University of New England, Armidale, NSW, Australia
Definition
Dolomite, CaCO 3 ÁMgCO 3 , is a common mineral, usually
found with limestone (CaCO 3 ). The rock, consisting principally of the mineral dolomite, is also called dolomite;
more recently it has come to be called dolostone. The process of the formation of the mineral and rock is referred to
as dolomitization.
Dolomite, the mineral, and the dolomitization
process
Dolomite, the mineral, was named at the end of the eighteenth century by the French Naturalist/Geologist
Deodat Gratel de Dolomieu (1750–1801) for rocks in
the Southern Tyrol Alps of northern Italy, an area now
referred to as the Dolomites. The study of the formation
of dolomite commenced with the classic papers of Cullis
(1904), Skeats (1905) and Van Tuyl (1916). The reader
is referred to Deelman (2008) for a comprehensive discussion on its mineralogy, regional occurrences, mechanisms of formation, and the subtleties of its chemistry
including ordered/disordered and stoichiometric/
enriched dolomites. Dolomite is not a solid solution
series with Ca and Mg end members but a mixed lattice
crystal, which contains approximately equal amounts of
CaCO 3 and MgCO 3 . The Ca
2+ and the Mg
2+ ions are
separated into individual monolayers, which are themselves separated by carbonate ion layers. Simple substitution of calcium ions by magnesium ions is not
possible and non-stoichiometry is very common. Usually, the wt% CaO:wt% MgO = 3:2. This is a very
important factor to be considered in the models of dolomitization, for simple substitution of Ca
2+ ions by Mg
2+
ions is not chemically feasible and dolomitization
models that propose this process are in error. Notwithstanding this, seawater is an ideal source of the Mg
2+
ions for dolomitization in reefal carbonates. Nucleation
of dolomite cannot be explained in terms of classical
equilibrium thermodynamics. Deelman (2008) proposes
that reaction kinetics that provide ongoing multiple fluctuations better explain dolomite formation. “The kinetic
hindrances to dolomite precipitation from seawater can
be overcome by evaporating seawater, diluting it, raising
the temperature or lowering the SO 4
2À content” (Tucker
and Wright, 1990). These authors as well as Deelman
(2008) provide a comprehensive, up-to-date account of
the complexities of dolomite formation, either as
a primary precipitate or as a secondary replacement of
a metastable precursor mineral. It was Deelman (1999)
who first explained how dolomite can form under
low temperatures and atmospheric conditions through
DOLOMITIZATION
321
Congress. Tahiti, Vol. 3, pp. 263–269.
Purser, B. H., and Schroeder, J. H., 1986. The diagenesis of reefs:
a brief review of our present understanding. In Schroeder,
J. H., and Purser, B. H. (eds.), Reef Diagenesis. Berlin: Springer,
pp. 424–446.
Purser, B. H., Brown, A., and Aïssaoui, D. M., 1994. Nature, origins
and evolution of porosity in dolomites. Dolomites: International
Association of Sedimentologists. IAS special publication, 21,
pp. 283–308.
Reid, R. P., and Macintyre, I. G., 1998. Carbonate recrystallization
in shallow marine environments: a widespread diagenetic
process forming micritized grains. Journal of Sedimentary
Research, 68, 928–946.
Repellin, P., 1977. Contribution à l’étude pétrologique d’un récif
corallien: le sondage “Colette”, Atoll de Mururoa (Polynésie
Française). Cahiers du Pacifique, 20, 1–209.
Robbins, L. L., and Ostrom, P. H., 1995. Molecular isotopic and
biochemical evidence of the origin and diagenesis of shell
organic material. Geology, 23, 345–348.
Rougerie, F., 1995. Nature et fonctionnement des atolls des
Tuamotu (Polynésie Frangaise). Oceanologica Acta, 18, 61–78.
Rougerie, F., and Wauthy, B., 1986. Le concept d’endo-upwelling
dans le fonctionnement des atolls-oasis. Oceanologica Acta, 9,
133–148.
Sandberg, P. A., 1984. Recognition criteria of calcitized skeletal and
non-skeletal aragonites. Palaeontographica Americana, 54,
272–281.
Shinn, E. A., 1969. Submarine lithification of Holocene
carbonate Sediments in the Persian Gulf. Sedimentology, 12,
109–144.
Scherer, M., 1986. Diagenesis of aragonitic sponges from Permian
patch reefs of southern Tunisia. In Schroeder, J. H., and Purser,
B. H. (eds.), Reef Diagenesis. Berlin: Springer, pp. 291–310.
Schroeder, J. H., 1972. Fabrics and sequences of submarine carbonate cements in Holocene Bermuda cup reefs. Geologische
Rundschau, 61, 708–730.
Walter, L. M., 1985. Relative reactivity of skeletal carbonates during dissolution: implications for diagenesis. In Schneidermann,
N., and Harris, P. M. (eds.), Carbonate Cements. Tulsa, OK:
Society of Economic Paleontologists and Mineralogists. SEPM
special publication, 36, pp. 3–16.
Werner, U., Blazejak, A., Bird, P., Eickert, G., Schoon, R., Abed,
R. M. M., Bisset, A., and de Beer, D., 2008. Microbial photosynthesis in coral reef sediments (Heron Reef, Asutralia). Estuarine,
Coastal and Shelf Science, 76, 876–888.
Cross-references
Antecedent Platforms
Aragonite
Atolls
Beach Rock
Calcite
Calcrete/Caliche
Dolomitization
Emerged Reefs
Micrite
Mururoa Atoll
Oil and Gas Reservoirs and Coral Reefs
Palaeosols
Porosity Variability in Limestone Sequences
Stable Isotopes and Trace Elements
Submarine Lithification
DOLOMITIZATION
Peter Flood
University of New England, Armidale, NSW, Australia
Definition
Dolomite, CaCO 3 ÁMgCO 3 , is a common mineral, usually
found with limestone (CaCO 3 ). The rock, consisting principally of the mineral dolomite, is also called dolomite;
more recently it has come to be called dolostone. The process of the formation of the mineral and rock is referred to
as dolomitization.
Dolomite, the mineral, and the dolomitization
process
Dolomite, the mineral, was named at the end of the eighteenth century by the French Naturalist/Geologist
Deodat Gratel de Dolomieu (1750–1801) for rocks in
the Southern Tyrol Alps of northern Italy, an area now
referred to as the Dolomites. The study of the formation
of dolomite commenced with the classic papers of Cullis
(1904), Skeats (1905) and Van Tuyl (1916). The reader
is referred to Deelman (2008) for a comprehensive discussion on its mineralogy, regional occurrences, mechanisms of formation, and the subtleties of its chemistry
including ordered/disordered and stoichiometric/
enriched dolomites. Dolomite is not a solid solution
series with Ca and Mg end members but a mixed lattice
crystal, which contains approximately equal amounts of
CaCO 3 and MgCO 3 . The Ca
2+ and the Mg
2+ ions are
separated into individual monolayers, which are themselves separated by carbonate ion layers. Simple substitution of calcium ions by magnesium ions is not
possible and non-stoichiometry is very common. Usually, the wt% CaO:wt% MgO = 3:2. This is a very
important factor to be considered in the models of dolomitization, for simple substitution of Ca
2+ ions by Mg
2+
ions is not chemically feasible and dolomitization
models that propose this process are in error. Notwithstanding this, seawater is an ideal source of the Mg
2+
ions for dolomitization in reefal carbonates. Nucleation
of dolomite cannot be explained in terms of classical
equilibrium thermodynamics. Deelman (2008) proposes
that reaction kinetics that provide ongoing multiple fluctuations better explain dolomite formation. “The kinetic
hindrances to dolomite precipitation from seawater can
be overcome by evaporating seawater, diluting it, raising
the temperature or lowering the SO 4
2À content” (Tucker
and Wright, 1990). These authors as well as Deelman
(2008) provide a comprehensive, up-to-date account of
the complexities of dolomite formation, either as
a primary precipitate or as a secondary replacement of
a metastable precursor mineral. It was Deelman (1999)
who first explained how dolomite can form under
low temperatures and atmospheric conditions through
DOLOMITIZATION
321