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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
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Diagenetic products such as micritization, cementation, chemical compaction and dolomitization were observed in the formation and point toward the role of groundwater and meteoric water during the burial of sediments.
The ooid grains feature diagenetic replacive dolomitization and dissolution vugs.
8b), and (3) transformation of minerals from the clay fraction into hematite during early diagenesis preceding dolomitization. The presence of pyrite, sphalerite, and siderite (in small amounts) in carbonate rocks is also supported by the absence of [Fe.sub.2][O.sub.3total]-FeO correlation in carbonate rocks (Fig.
However, heterogeneities in the substrate, made by bioturbating infauna, may play a more important role in dolomitization than has been previously considered.
It is possible that the silica was derived from the host rock during early diagenesis late in the Permian Period, however, this is difficult to ascertain because of the extensive dolomitization of the rock body.
In the Lisheen area the Waulsortian has been affected by both regional and hydrothermal dolomitization which obscures many of the original sedimentary features.
This interpretation is based on isotope data [9], which shows slight shifts in [delta][sup.18]O relative to dolomite, elevated fluid inclusion temperatures of dedolomite [19, 28], and the absence of any signs of meteoric exposure after initial dolomitization [9, 25].
Kiipli (1983) noted a link between the dolomitization of the Pae Member (and occasionally lithologies below and above) and fracture zones.
The OS layers have only locally slightly changed in the diagenetic processes, whereas the barren limestone interlayers are strongly enriched with MgO and depleted of CaO that is caused by diagenetic dolomitization.