Metamorphism of carbonaceous material in the Tono contact aureole, Kitakami Mountains, Japan

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Authors:Okuyama-Kusunose, Yasuko; Itaya, Tetsumaru
Author Affiliations:Primary:
Geol. Surv. Japan, Higashi, Japan
Other:
Okayama Univ. Sci., Japan
Volume Title:Journal of Metamorphic Geology
Source:Journal of Metamorphic Geology, 5(2), p.121-139. Publisher: Blackwell, Oxford, United Kingdom. ISSN: 0263-4929
Publication Date:1987
Note:In English. 51 refs.; illus. incl. sketch map
Summary:Optical and XRD studies of carbonaceous material in Palaeozoic sediment cut by a Cretaceous granite in this area of NE Japan revealed that metamorphic graphitization proceeded through two discontinuous changes: 1) optically anisotropic domains develop in the coaly phytoclast, and 2) ordered graphite crystallizes by decomposition of pre-existing carbonaceous materials. Coaly material disappears in the uppermost chlorite zone. Graphite appears in the upper chlorite zone and increases in abundance across the andalusite isograd to the cordierite isograd where all carbonaceous material has been converted to graphite. The d002 value decreases from 3.55 in the lower chlorite zone to 3.35 A in the sillimanite zone, with a corresponding increase in the crystallite size from 10 to >1000 A. The T of graphitization is at least 100°C higher than the T in the Sanbagawa and New Caledonia high-P metamorphic terrains, probably due to the slow reaction rate and short duration of contact metamorphism. [R.A.H.]
Subjects:Carbonaceous composition; Contact metamorphism; Geologic thermometry; Graphite; Graphitization; High temperature; Metamorphic rocks; Metamorphism; Metasedimentary rocks; Native elements; Optical properties; Petrology; Temperature; X-ray diffraction data; Asia; Far East; Honshu; Iwate Japan; Japan; Kitakami Mountains; Northeastern Japan; Organic residues; Tono contact aureole
Abstract Numbers:87M/6898
Record ID:1987063939
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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