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The study of widespread tephras in central Japan with special reference to the volcanic history of Norikura volcanic zone.

对日本中部广泛分布的火山灰的研究，特别涉及乘鞍火山带的火山历史。

基本信息

批准号：
62540579
负责人：
KOBAYASHI Takehiko
金额：
$ 0.83万
依托单位：
Toyama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1988
项目状态：
已结题

项目摘要

By means of tephrochronology, especially by widespread tephra layers from distant sources as Aira tn Ash layer(Abbr.:AT), Daisen Krayoshi Pumice layer(DKP), Volcanic ash layer of Aso 4, Kikai-Tozurahara Ash(K-Tz) and so on, the isolated volcanic products belonging to Norikura volcanic zone are correlated each other for the purpose of investigating volcanic evolution of the zone. The volcanic history of the zone is supposed to relate to quaternary tectonic movement, because the volcanoes of the zone align well on the N-S trend overllapping to one of the most active uplift-axis of central japan in quaternary time and paralleling to the northern part of the Itoigawa-Shizuoka tectonic zone.The tephrochronological research is effective in correlating the younger halves of Ontake and Tateyama volcanoes with their own numerous tephra layers, and tephra stratigraphy is not effective for Norikura, Yakedake and Washiba-Kumonotaira volcanoes and the older halves of the former two volcanoes.Norikura volcanic zone started about 0.7-0.6 Ma ago and the volcanism contnued for perhaps 0.3 ma based on radiometric age. After the long inactive period, the younger activity simultaneously took place about 0.1 Ma ago and the earlier stage of the activity erupted the most acidic products on each volcano. Magmatic activity lasted about 30,000 years ago on Ontake and Tateyama volcano. And continued more later on Norikura and Yakedake volcanoes. Recently the phreatic activities repeated the volcanic zone.To complete the study, we need the radiometric age data for the products on Norikura, Yakedake and Washiba-Kumonotaira volcanoes because they do not seem to have the extensive tephra layers.

通过火山灰年代学，特别是通过来自遥远来源的广泛火山灰层，如Aira tn Ash层（缩写：AT）、戴森浮岩层（DKP）、阿索4火山灰层、岐海-土冢原火山灰（K-Tz）等属于纪仓火山带的孤立火山产物进行了对比，以探讨该火山带的火山演化。该带的火山活动历史与第四纪构造运动有关，因为该地带的火山在南北走向上排列良好，与日本中部第四纪最活跃的隆起轴之一重叠，并与伊藤川的北方部分平行，火山灰年代学研究有效地将Ontake和Tateyama火山的年轻部分与它们自己的大量火山灰联系起来纪仓火山带形成于0.7- 0.6Ma，火山活动持续时间约为0.3Ma。在经历了长期的不活动期后，较年轻的火山活动同时发生，约在0.1Ma前，火山活动的早期喷发出酸性最强的产物。火山活动持续了大约30，000年前的Ontake和立山火山。后来在纪仓火山和屋岳火山继续进行。近年来，潜水活动在火山带中反复出现，由于纪仓火山、屋岳火山和鹫场熊之平火山似乎没有大面积的火山灰层，因此需要得到这些火山产物的放射性年龄数据。