Proterozoic anticlockwise P-T path of the Lewisian Complex of South Harris, Outer Hebrides, NW Scotland

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Authors:Baba, S.
Author Affiliations:Primary:
Osaka City University, Department of Geosciences, Osaka, Japan
Volume Title:Journal of Metamorphic Geology
Source:Journal of Metamorphic Geology, 16(6), p.819-841. Publisher: Blackwell, Oxford, United Kingdom. ISSN: 0263-4929
Publication Date:1998
Note:In English. 81 refs.; illus., incl. 5 tables, geol. sketch maps
Summary:The Leverburgh belt and South Harris igneous complex experienced high-P granulite-facies metamorphism during the Palaeoproterozoic. Metamorphic history is determined from mineral textures and compositions in pelitic, quartzofeldspathic and mafic gneisses, especially in pelitic gneisses. Coarse-grained garnet in pelitic gneiss includes biotite and quartz in the inner core, sillimanite in the outer core, and is overgrown by kyanite; garnet in pelitic gneiss has a progressive increase in grossular content from outer core to rims; [6]Al/[4]Al ratio of clinopyroxene from mafic gneiss increases from core to rim; retrograde reaction coronas of cordierite and hercynite+ cordierite are formed between garnet and kyanite, and orthopyroxene + cordierite and orthopyroxene + plagioclase between garnet and quartz; a prograde P-T path is deduced from inclusion assemblages in garnet and from staurolite breakdown reactions to produce garnet + sillimanite and garnet + sillimanite + hercynite; and in sheared and foliated rocks, hydrous minerals such as biotite, muscovite and hornblende form a foliation, modifying earlier textures. The metamorphic history is divided into four stages: (M1) prograde metamorphism with increasing T; (M2) prograde metamorphism with increasing P; (M3) retrograde metamorphism during decompression; and (M4) retrograde metamorphism accompanied by shearing. Peak P-T conditions during M2 were 800 ± 30°C, 13-14 kbar and followed thrusting of continental crust over the belt during continent-continent collision. The inferred P-T path and tectonic history are different from those of the mainland Lewisian. [P.J.T.]
Sections:Petrology
Subsections:Metamorphism: regional, dynamic
Subjects:Crystal chemistry; Deformation; Facies; Geochemistry; Geologic barometry; Geologic thermometry; Gneisses; Granulite facies; Lewisian Complex; Lithogeochemistry; Metamorphic rocks; Metamorphism; Mineral assemblages; P-T conditions; P-T-t paths; Plate collision; Plate tectonics; Precambrian; Prograde metamorphism; Proterozoic; Tectonics; Textures; Upper Precambrian; Europe; Great Britain; Harris; Hebrides; Outer Hebrides; Scotland; United Kingdom; Western Europe
Coordinates:N573000 N580000 W0064500 W0071500
Abstract Numbers:99M/3299
Record ID:1998073304
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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