Study on Mantle Origin Magnesian Andesite from the Southern Pacific Region.
| Project/Area Number |
63041068
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| Research Category |
Grant-in-Aid for Overseas Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Field Research |
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| Research Institution | Aichi University of Education |
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Principal Investigator |
URANO Hayaomi Aichi Univ. of Education, Dpt. of Earth Sciences, Professor., 教育学部, 教授 (50023990)
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| Co-Investigator(Kenkyū-buntansha) |
P.M. Black オークランド大学, 地質学部, 教授
鮫島 輝彦 オークランド大学, 地質学部, 客員研究員
KURODA Naoshi Shizuoka Univ., Inst. of Geosciences, Professor., 理学部, 教授 (60021903)
SHIRAKI Keiichi Yamaguchi Univ., Dpt. of Mineralogical Sciences and Geology, Assoc. Professor., 理学部, 助教授 (60144911)
SUGIURA Tsutomu Aichi Univ. of Education, Dpt. of Chemistry, Professor., 教育学部, 教授 (60023991)
SAMESHIMA Teruhiko Univ. of Auckland, Geology Dpt., Emeritus Professor.
BLACK P.M. Univ. of Auckland, Geology Dpt., Professor.
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| Project Period (FY) |
1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥5,000,000 (Direct Cost: ¥5,000,000)
Fiscal Year 1988: ¥5,000,000 (Direct Cost: ¥5,000,000)
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| Keywords | Boninite / Magnesian Andesite / New Caledonia / New Zealand / Island Arc / Andesite / Volcanic Rocks / 超苦鉄質岩 |
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| Research Abstract |
In New Caledonia boninites have been found in Nepoui on the west coast and Col d' Amieu in the central mountains. New occurrences of boninites were found as breccias on the Rouge River and on the serpentinite hill of Kiwanis. The latter contains abundant clinoenstatite phenocrysts. The clinoenstatite has Mg values of 90-88 ; Mg values of the orthopyroxene are 87 and those of pigeonite 70. The Col d' Amieu boninite contains augite and pseudomorphs after clinoenstatite. A metagabbro with pumpellyite and prehnite occurs below the boninite. Overlying the boninite is an olivine basalt having augite and plagioclase. The volcanic rocks of the Basaltic formation consist mainly of olivine basalts containing occasionally orthopyroxene.
In New Zealand magnesian andesites have been found in the Tertiary Wairakau andesites and in the Quaternary Taupo and Kiwitahi volcanic belts. A large amount of magnesian andesite occurs in the Tongariro volcanic centre. Magnesian andesites were collected from Poutu damsite, Mahuia Rapids, Pukeonake and Ohakune. Samples from Poutu damsite contain abundant pyroxene crystals up to 1 cm across. These magnesian andesites may have been formed by accumulation of olivine and pyroxene phenocrysts. An electron probe study was made on constituent minerals in amagnesian andesite from White Island. Olivine shows normal zoning ranging from Fo 92.1 to Fo 82.9, while clino-and ortho-pyroxenes, as well as plagioclase, show reverse zoning. Mg values in the cores of clinopyroxene are 78.7-75.2 and those in the rims 83.9-79.7. The orthopyroxene cores have Mg values of 76.6 to 73.8 and the rims Mg values of 81.6 to 70.3. The compositional gap between olivine and pyroxene cores suggests that these minerals have not crystallized from a common, single magma. The White Island magnesian andesite would be a mixing product of high-Mg magma with low-Mg, high-Si one.
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Report
(1 results)
Research Products
(12 results)
