A fluid inclusion and stable isotope study of 200 Ma of fluid evolution, Galway Granite, Connemara, Ireland

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doi: 10.1007/s004100050327
Authors:O'Reilly, C.; Jenkin, G. R. T.; Feely, M.; Alderton, D. H. M.; Fallick, A. E.
Author Affiliations:Primary:
University College, Galway, Ireland
Other:
Scottish Universities Research and Reactor Center, United Kingdom
Royal Holloway University of London, United Kingdom
Volume Title:Contributions to Mineralogy and Petrology
Source:Contributions to Mineralogy and Petrology, 129(2-3), p.120-142. Publisher: Springer International, Heidelberg-New York, International. ISSN: 0010-7999
Publication Date:1997
Note:In English. 117 refs.; illus., incl. 4 tables, geol. sketch map
Summary:Fluid inclusions in granite quartz and three generations of veins indicate that three fluids have affected the Caledonian Gallway granite. The earliest fluid was a H2O-CO2-NaCl fluid of moderate salinity (4-10 wt.% NaCl eq.) that deposited late-magmatic molybdenite mineralized quartz veins and formed the earliest secondary inclusions in granite quartz. Homogeneous quartz δ 18O across the batholith suggests that these quartz veins precipitated at high T (perhaps 600°C) and P (1-3 kbar) from magmatic fluids. The second fluid was a H2O-NaCl-KCl low-moderate salinity (0-10 wt.% NaCl eq.), moderate T (270-340°C), high δ D (-18 ± 0/00), low δ 18O (0.5-2.00/00) fluid of meteoric origin. This fluid forms the most common inclusion type in granite quartz and penetrated the batholith via quartz veins. The final fluid was a H2O-NaCl-CaCl2-KCl fluid with variable salinity (8-20 wt.% NaCl eq.), T (125-205°C), δ D (-17 to -450/00), δ 18O (-3 to +1.20/00), δ 13C (-19 to 00/00) and δ 34Ssulphate (13 to 230/00) that deposited veins with quartz, fluorite, calcite, baryte, galena, chalcopyrite, sphalerite and pyrite; these conditions are interpreted as the result of mixing of two fluid end-members, one a contemporaneous surface fluid (probably mixed meteoric water and evaporated sea-water) and the other a basinal brine derived from the adjacent Carboniferous sequence. [R.A.H.]
Sections:Geochemistry
Subsections:Igneous rocks
Subjects:Batholiths; Caledonian Orogeny; Chemical composition; Chlorite; Chlorite group; D/H; Fluid inclusions; Geologic thermometry; Granites; Hydrogen; Igneous rocks; Inclusions; Intrusions; Isotope ratios; Isotopes; Metagabbro; Metaigneous rocks; Metamorphic rocks; O-18/O-16; Oxygen; P-T conditions; Paleozoic; Plutonic rocks; Quartz veins; S-34/S-32; Sheet silicates; Silicates; Stable isotopes; Sulfur; Veins; Connemara; Europe; Galway Granite; Galway Ireland; Ireland; Western Europe
Abstract Numbers:99M/513
Record ID:1999008569
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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