The role of aqueous silica concentration in controlling the mineralogy during high temperature contact metamorphism: A case study from Fuka contact aureole, Okayama, Japan
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Accession number;04A0874358
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| Title;The role of aqueous silica concentration in controlling the mineralogy during high temperature contact metamorphism: A case study from Fuka contact aureole, Okayama, Japan |
| Author;
SATISH-KUMAR M
(Shizuoka Univ., Shizuoka, Jpn)
YOSHIDA Y
(Shizuoka Univ., Shizuoka, Jpn)
KUSACHI I
(Okayama Univ., Okayama, Jpn)
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Journal Title;J Mineral Petrol Sci
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Journal Code:G0150B
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ISSN:1345-6296
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VOL.99;NO.5;PAGE.328-338(2004)
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| Figure&Table&Reference;FIG.7, TBL.4, REF.27 |
| Pub. Country;Japan |
| Language;English |
| Abstract;The contact aureole at Fuka, Okayama, Japan is peculiar for the occurrence of extensive high-temperature skarn resulting from the intrusion of Mesozoic monzodiorite into Paleozoic marine limestone. The occurrence is also notable for the finding of ten new minerals, of which five are calcium-boron-bearing minerals, and scores of other rare minerals. Skarn formation at Fuka can be classified into three major types 1. Grossular-vesuvianite-wollastonite endoskarn, 2. Gehlenite-exoskarns, and 3. Spurrite-exoskarns. Grossular-vesuvianite-wollastonite endoskarn forms a narrow zone (few centimeter width) separating the exoskarn and the igneous intrusion. It is also found, developed independently, along contacts of the younger basic intrusive dykes and limestone in the region. The gehlenite-exoskarns, in most cases, are spatially associated with igneous intrusion and are extensive (decimeter to meter thick). However, exceptions of independent gehlenite dikes are also observed. Retrogression of the gehlenite endoskarns results in the formation of hydrogrossular and/or vesuvianite. Accessory phases include schrolomite and perovskite. The predominantly monomineralic spurrite-exoskarn was formed in the outer zone of the gehlenite-skarn parallel to the contact as well as independent veins, dikes and tongues. The spurrite-exoskarn may extend tens of meters. Spurrite coexists with tilleyite or rankinite, although larnite is absent. Idiomorphic gehlenite and vesuvianite are the most common accessory phases observed. Retrograde hydration of spurrite to foshagite, scawtite and hillebrandite is commonly observed as veins and alteration zones within the spurrite exoskarn. Petrogenetic grids were constructed using "THERMOCALC" for the observed mineral assemblage in the spurrite skarn. Mineral-fluid equilibrium in the CaO-SiO2-CO2 system was computed, considering the metasomatic input of aqueous silica.... (author abst.) |
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