Paragenesis of titanium-bearing accessories in pelitic schists of the Sanbagawa metamorphic belt,Central Shikoku,Japan |
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| Authors: | Tetsumaru Itaya Shohei Banno |
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| Institution: | (1) Institute of Mineralogy, Petrology, and Economic Geology, Tohoku University, 980 Sendai, Japan;(2) Department of Earth Sciences, Kanazawa University, 920 Kanazawa, Japan |
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| Abstract: | In pelitic schists of the Sanbagawa metamorphic belt, sphene, rutile, and ilmenite occur as discrete grains, in composite aggregates, and as inclusions in garnets. Textural relationships, disposition of inclusions in garnet, and the compositions of ilmenites suggest that the titanium-bearing accessories stable at the peak metamorphic conditions were as follows: sphene in the chlorite zone, sphene plus rutile in the garnet zone, and ilmenite in the highest grade of the belt, the biotite zone. Rutile appears in the garnet zone as a consequence of Ca incorporation into garnet and a progressive increase in
.Retrograde reactions were responsible for the composite aggregates of rutile, sphene and ilmenite and these must be carefully evaluated before prograde relationships between titanium-bearing accessories can be properly understood. |
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