The effect of reaction overstep on garnet microtextures in metapelitic rocks of the Ilesha schist belt, SW Nigeria

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doi: 10.1093/petrology/44.6.967
Authors:Zeh, A.; Holness, M. B.
Author Affiliations:Primary:
Universitat Wurzburg, Mineralogisches Institut, Wurzburg, Federal Republic of Germany
University of Cambridge, United Kingdom
Volume Title:Journal of Petrology
Source:Journal of Petrology, 44(6), p.967-994. Publisher: Oxford University Press, Oxford, United Kingdom. ISSN: 0022-3530
Publication Date:2003
Note:In English. 47 refs.; illus., incl. 7 tables, geol. sketch map
Summary:Various pan-African aged assemblages containing garnet, staurolite, andalusite, sillimanite, cordierite, biotite, muscovite, chlorite, magnetite, quartz, plagioclase and ilmenite indicate peak metamorphism at 590°C at 5 kbar followed by retrogression to 550°C at 3 kbar. The absence of compositional zonation in garnet shows garnet grew at constant P-T-X in equilibrium with associated minerals but it did not begin growing until an overstep of T of ∼ 80°C had taken place and rapid chlorite and muscovite dehydration occurred. 'House of cards' internal textures of biotite and quartz inclusions in the garnet are well illustrated. Garnet resorption with prograde staurolite- and retrograde andalusite-forming reactions also occurred. EPMA of the minerals listed above are given. [B.E.L.]
Subsections:Metamorphism: regional, dynamic
Subjects:Effects; Garnet group; Metamorphic rocks; Metamorphism; Metapelite; Metasedimentary rocks; Mineral assemblages; Nesosilicates; Orthosilicates; Retrograde metamorphism; Silicates; Africa; Nigeria; West Africa; Ilesha Belt; Microtextures; Southwestern Nigeria
Coordinates:N073000 N074000 E0045000 E0043500
Abstract Numbers:03M/4860
Record ID:2003058968
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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