阿蘇カルデラ南西部の岩脈群のK-Ar年代

概要

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Aso is a large caldera volcano in Kyushu, Japan. Several dikes, which cut the Pre-Aso volcanic rocks, are exposed in the southwestern region of the caldera (ONO and WATANABE, 1985). The dikes, trending NE-SW and N-S, are composed of pyroxene andesite and hornblende andesite. Systematic relation between the rocks type and direction of the dikes is not observed. In this study, K-Ar ages have been determined on these dike rocks. The ages of dike rocks range from ca. 0.8 to 0.5 Ma, being consistent with the ages of the Pre-Aso volcanic rocks at the caldera wall. There are no significant relations between the ages and the rock type. Except for one sample with weak alteration, the dikes trending NE-SW are older than those of N-S, suggesting a change of direction of the maximum pressure axis of regional stress in the volcanism.
特定非営利活動法人日本火山学会の論文
1989-10-25