Regional dolomitization of the Waulsortian limestone in southeastern Ireland; evidence of large-scale fluid flow driven by the Hercynian Orogeny

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doi: 10.1130/0091-7613(1998)026<0547:RDOTWL>2.3.CO;2
Authors:Hitzman, M. W.; Allan, J. R.; Beaty, D. W.
Author Affiliations:Primary:
Colorado School of Mines, Department of Geology and Geological Engineering, Golden, CO, United States
Allan Geological Analysis, United States
Chevron Petroleum Technology Company, United States
Volume Title:Geology (Boulder)
Source:Geology (Boulder), 26(6), p.547-550. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613
Publication Date:1998
Note:In English. 16 refs.; illus., incl. sect., 1 table, geol. sketch map
Summary:The Lower Carboniferous Waulsortian limestone has been affected by late diagenetic, regional burial dolomitization over an area of ∼7000 km2 extending 170 km northeastward from the Hercynian front. The dolostone is composed of two components: (1) a very fine crystalline replacive component, and (2) a coarse-crystalline, baroque component that fills vuggy porosity developed within the replacive dolostone. Fluid inclusions within the coarse-crystalline component of the regional dolostone indicate that the dolomitizing solutions were warm (∼100 °C) and moderately saline (10-13 wt% NaCl equivalent). The replacive dolomite displays systematic decreases in crystal size and degree of xenotopic texture northward. Both components of the regional dolostone display a regular northward increase in mean δ18O values; the replacive dolomite has 87Sr/86Sr values that decrease northward. These laterally variable characteristics suggest that regional dolomitization resulted from large-scale, north-directed fluid flow of heated brines developed in response to topographic uplift associated with collapse of the continental margin south of Ireland during the Hercynian (Variscan) orogeny.
Subsections:Sedimentary rocks
Subjects:Alkaline earth metals; C-13/C-12; Carbon; Carbonate rocks; Carbonatization; Carboniferous; Diagenesis; Dinantian; Dolomitization; Dolostone; Fluid inclusions; Geochemistry; Inclusions; Isotope ratios; Isotopes; Metals; O-18/O-16; Orogeny; Oxygen; Paleozoic; Sedimentary rocks; Sr-87/Sr-86; Stable isotopes; Strontium; Variscan Orogeny; Waulsortian facies; Europe; Ireland; Western Europe; Southeastern Ireland
Coordinates:N520000 N530000 W0070000 W0090000
Abstract Numbers:99M/589
Record ID:1998037038
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
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