Dolomitization

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dolomitization

[‚dō·lə·məd·ə′zā·shən]
(geology)
Conversion of limestone to dolomite rock by replacing a portion of the calcium carbonate with magnesium carbonate.

Dolomitization

 

the process of enriching calcareous silt (sediment) or limestone with dolomite through the substitution of MgCO3 for part of the CaCO3. There are two types of dolomitization: diagenetic, which occurs in silt during the process of its conversion into sedimentary rock, and epigenic, which occurs in already solidified limestone. Epigenic dolomitization is caused by the action of subterranean waters enriched with magnesium, as they pass through strata of dolomite, ultrabasic igneous rock, and so forth. A complete substitution of dolomite for the calcite rarely oc-curs with these secondary limestone changes. Usually dolomitized limestones are formed.

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Pore-water trapped in limestone may promote dolomitisation (Kupecz and Land, 1991) because these waters are typically Ca-enriched and their molar Ca/Mg ratio increases with increasing temperature (Kupecz and Land, 1991).
Land (1985) concluded that seawater is the only widely-available fluid having sufficient magnesium to cause massive dolomitisation, and diagenetic dolomitisation of calcite-rich carbonates requires large volumes of water to supply the required Mg (Land, 1992).
The diagenetic processes that have affected the Arab-D reservoir include dolomitisation, leaching and recrystallisation, cementation, compaction and fracturing.
1993): The evolution of the Middle Triassic (Muschelkalk) carbonate ramp in the SE Iberian Ranges, eastern Spain: sequence stratigraphy, dolomitisation pro cesses and dynamic controls.
The shale and claystone MgO and CaO content was low; the samples thus did not indicate associated carbonates or dolomitisation.