島根大学総合理工学部地球科学教室
ISSN:1343-9774
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Earth science reports of Shimane University 37
2020-03-25 発行

烏ヶ山溶岩ドームおよびそれに関連する火砕流堆積物の岩石学的・鉱物化学的研究

Petrology and mineral chemistry of the Karasugasen lava dome and associated pyroclastic flow deposits
Ito, Yutaka
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Description
The Karasugasen lava dome is part of the Daisen – Hiruzen Volcanic complex and was the source of a large number of Block and Ash flows. Products directly overlie the Aira Tanzawa tephra (AT), and the majority of erupted material is preserved in three voluminous lobes to the south and southeast of Mt Daisen. Dacitic magmas with adakitic characteristics were sourced from a large magma chamber in the shallow crust crystallizing between 4 and 12 km depth, at temperatures between 803 and 920 ˚C and oxygen fugacities of Δlog +1.7 to +1.8 above the NNO buffer. Cores of magnesium rich orthopyroxene phenocrysts are not in equilibrium with the host dacite and may be a rare evidence for insipient mafic replenishment of the voluminous magma chamber beneath the Daisen Volcanic complex.
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