Geochemical Investigation of the Aegean Volcanic Arc

本野外研究的目的是通过火山挥发分地球化学方法和火山地貌方法研究爱琴海火山弧的岩浆活动。由于爱琴弧具有大陆板块俯冲的特征，与包括日本弧在内的大多数与大洋板块俯冲有关的火山弧不同，爱琴弧在弧火山作用的比较研究中占有重要地位。他们与一名希腊调查员一起对希腊的火山和地热地区进行了实地监测。2年监测的调查地点为火山前缘沿着Susaki、Methana、Aegina、Milos、Santrini、科斯和Nisylos火山，弧后地区的Lesbos和Ikaria岛以及Thermolipes和Edipusos地热战神。在各地进行了（1）火山气、火山气、温泉气等岩浆挥发性物质的野外调查，（2）温泉的野外调查，（3）火山地貌调查。我们在每个考察地点采集了气样和水样，带回日本进行化学和同位素分析，并对气样进行了^3He/^4He比值和CO_2 δ ^<13>C的测定。同时测定了水样的化学成分和氢氧同位素。结果表明，温泉沃茨多为陨石成因，气体中含有岩浆成因的氦和海相碳酸盐成因的碳。在完成对所采集样品的化学和同位素分析后，结合形态学研究成果，探讨大陆板块俯冲作用下岩浆挥发分的来源和释放机制。

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.