Formation of the Archaean greenstone belt

Research Project

Project/Area Number	07640638
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Petrology/Mineralogy/Science of ore deposit
Research Institution	Nagoya University
Principal Investigator	HOSHINO Mitsuo Nagoya University, School of Informatics and Sciences, Associate Professor, 情報文化学部, 助教授 (40023626)
Co-Investigator(Kenkyū-buntansha)	SUGITANI Kenichiro Nagoya University, School of Informatics and Sciences, Research Associate, 情報文化学部, 助手 (20222052) ITO Masahiro Nagoya University, School of Informatics and Sciences, Professor, 情報文化学部, 教授 (70023603)
Project Period (FY)	1995 – 1996
Project Status	Completed (Fiscal Year 1996)
Budget Amount *help	¥2,300,000 (Direct Cost: ¥2,300,000) Fiscal Year 1996: ¥600,000 (Direct Cost: ¥600,000) Fiscal Year 1995: ¥1,700,000 (Direct Cost: ¥1,700,000)
Keywords	Kenya / Greenstone belt / Precambrian / Archaean / Thermal metamorphism / Granitoid / Metamorphic rocks / Craton
Research Abstract	1. EPMA analyzes of rock-forming-minerals in the thermally metamorphosed rocks EPMA analyzes are made on minerals in metavolcanics and metasediments. Chemical composition of amphiboles varies considerably even in a single metabasalt. This suggests that the equilibrium is not attained during the thermal metamorphism that took place in this area. 2. XRF bulk chemical analyzes XRF analyzes are made on granitoids and metavolcanics. Granitoids occur as batholiths and as stocks. They are petrographically classified into four types. Major element chemistry differs between rocks of different type and also differs between rock masses belonging to the same rock type. Each of the granitoid masses probably has a different history of its emplacement. 3. Conclusion The granitoids in the Archaean greenstone belt in Kenya emplaced in the shallow level of preexisting volcanic and sedimentary rocks. Thermal structures of the contact aureole depend on petrologic characteristics and shapes of the granitoid mass. The granitoid-greenstone association formed the upper part and the granitoid-high grade rock association formed the lower part in the Archaean Craton.