Geochemical Investigation of the Aegean Volcanic Arc

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The purpose of this Field Research is to investigate magmatic activities in the Aegean volcanic arc by means of both geochemical approach of volcanic volatiles and volcano-geomorphological approach. Because the Aegean arc is characterized by the continental (African) plate subduction, in contrast to most of volcanic arcs including Japanese arcs related to oceanic plate subduction, this arc plays an important role for the comparative study of arc volcanism.Japanese investigators visited Greece during 19 August to 19 September, 1993, and 12 September to 14 October, 1994. They carried out field surveillance of volcanic and geothermal areas in Greece with a Greek investigator. Investigated places of two years' surveillance are Susaki, Methana, Aegina, Milos, Santrini, Kos and Nisylos volcanoes along the volcanic front, and Lesbos and Ikaria islands and Thermolipes and Edipusos geothermal ares in the back arc region. In each place, we carried out (1) firld survey of magmatic volatile materials such as volcanic gas, fumarolic gas and hot spring gas, (2) field survey of hot springs and (3) volcano-geomorphological survey. We collected gas samples and water samples in each investivated place and brought them back to Japan for chemical and isotope analyzes.For gas samples, ^3He/^4He ratio and delta^<13>C of CO_2 were determined. While, chemical composition and H and O isotope were determined for water samples. Preliminaty results show that most of hot spring waters are in meteoritic origin and that gas samples include magma-derived helium, and carbon in marine carbonate origin. After completing the chemical and isotope analyzes of collected samples, we will discuss the origin of magmatic volatiles and their release mechanism under the con nental plate subduction, in combination with morphological findings.