Growth history of garnet in pelitic schists of the Sanbagawa metamorphic terrain in central Shikoku

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Authors:Sakai, Chihiro; Banno, Shohei; Toriumi, Mitsuhiro; Higashino, Toshio
Author Affiliations:Primary:
Kyoto Univ., Dep. Geol. and Mineral., Kyoto 606, Japan
Ehime Univ., Dep. Earth Sci., Japan
Hakusan Nat. Conserv. Cent., Japan
Volume Title:Lithos
Source:Lithos, 18(2), p.81-95. Publisher: Elsevier, Amsterdam, International. ISSN: 0168-1648
Publication Date:1985
Note:In English. 1 p. refs.; illus. incl. 2 anal., 2 tables, geol. sketch maps
Summary:During the prograde metamorphism of the Sanbagawa metamorphic terrain, garnet has grown in the pelitic schists whilst maintaining surface equilibrium with coexisting minerals such as chlorite and epidote, etc. In the quartz-albite layer, it has grown euhedrally. In the micaceous layer, its crystal morphology varies according to the different minerals in contact and their different orientations. Garnet enclosed in or sandwiched between micas is always ellipsoidal, extended parallel to the basal planes of the micas. However, when the edge of a garnet has intruded at an acute angle into the micas, euhedral garnet has grown. It is concluded that the growth of garnet at the interface with micas ceased when the (110) surface of garnet came into contact with the basal plane of the micas in the tectonic c-axis direction. Other models, such as chloritization-resorption, pressure-solution, and mechanical- erosion or grinding, do not adequately explain the origin of the flattened garnet. During retrograde metamorphism, chloritization and resorption of garnets took place in the matrix, resulting in the rough and irregular surface of garnet, Garnets included in albite porphyroblasts have been largely unaffected by the retrograde metamorphism. [G.R.]
Subjects:Crystal growth; Garnet group; Metamorphic rocks; Metamorphism; Metapelite; Metasedimentary rocks; Mineralogy; Minerals; Nesosilicates; Orthosilicates; Paleozoic; Petrology; Retrograde metamorphism; Silicates; Asia; Far East; Japan; Sambagawa Belt; Shikoku
Abstract Numbers:86M/2161
Record ID:1987052992
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique
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