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Dolomitization and dedolomitization in the Senonian chalk of Northern Ireland

Published online by Cambridge University Press:  01 May 2009

M. J. Wolfe
M. J. Wolfe
Affiliation:
Exploration and Production Research Division, B.P. Research Centre, Sunbury-on-Thames, Middlesex
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Summary

A dolomite locality in the Senonian chalk at Mullaghcarton shows a sequence of fabric variations between the unconformity with the Trias and a discontinuity surface marking the top of the basal beds. The four main variations are (1) xenotopic dolomite at the base, (2) hypidiotopic dolomite with zoned crystals and a calcite sealed intercrystalline porosity, (3) zoned dolomite rhombs scattered in a microspar micrite matrix, and at the top (4) micrite with rhombohedral pores. The xenotopic fabric is interpreted as being due to distant source dolomitization and the hypidiotopic fabric with zoned crystals to local source dolomitization. The dedolomitization phenomena are related to the mechanisms of dolomitization; for distant source dolomitization the dedolomitization fabric mimics the dolomite fabric, whereas for local source dolomitization the dedolomite regenerates the pre-dolomitization fabric.

Type
Articles
Information
Geological Magazine , Volume 107 , Issue 1 , January 1970 , pp. 39 - 49
Copyright
Copyright © Cambridge University Press 1970

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