Silica mobility and fluid movement during metamorphism of the Connemara schists, Ireland

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Authors:Yardley, B. W. D.; Bottrell, S. H.
Author Affiliations:Primary:
Univ. Leeds, Dep. Earth Sci., Leeds, United Kingdom
Volume Title:Metamorphic styles in young and ancient orogenic belts
Volume Authors:Pattison, David R. M., editor; Ghent, E. D.; Gordon, T. M.
Source:Journal of Metamorphic Geology, 10(3), p.453-464; Metamorphic styles in young and ancient orogenic belts, Calgary, AB, Canada, Aug., 1990, edited by David R. M. Pattison, E. D. Ghent and T. M. Gordon. Publisher: Blackwell, Oxford, United Kingdom. ISSN: 0263-4929
Publication Date:1992
Note:In English. 35 refs.; illus. incl. 3 tables, sects., geol. sketch maps
Summary:Quartz veins in a wide range of metasediment types in the upper amphibolite facies rocks of Connemara attest to wide migration of silica but, contrary to common assumptions, there is clear evidence that these veins do not primarily result from movement of fluid to regions of lower P-T down the regional geothermal gradient. Under amphibolite-facies conditions, a dilute chloride fluid moving down T has the potential to alter 60 g of plagioclase to muscovite for each gram of vein quartz precipitated, while cooling over the T interval from 650 to 500 degrees C. The oxygen isotopic composition of matrix quartz varies between different rock types but for each type, closely matches that of the vein quartz. The results demonstrate the importance of local segregation processes in the formation of veins, and suggest that fluid convection cells were not developed during metamorphism on a scale larger than the individual sedimentary formations, if at all. [R.M.F.P.]
Subjects:Amphibolite facies; C-13/C-12; Carbon; Facies; Framework silicates; Geochemistry; Hydrodynamics; IGCP; Isotopes; Metamorphic rocks; Metamorphism; O-18/O-16; Oxygen; P-T conditions; Petrology; Quartz; Schists; Silica; Silica minerals; Silicates; Stable isotopes; Veins; Connemara; Europe; Galway Ireland; Ireland; Western Europe
Abstract Numbers:92M/4463
93M/4964
Record ID:1992021554
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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