A 5000-year record of multiple highly explosive mafic eruptions from Gunung Agung (Bali, Indonesia): implications for eruption frequency and volcanic hazards
A 5000-year record of multiple highly explosive mafic eruptions from Gunung Agung (Bali, Indonesia): implications for eruption frequency and volcanic hazards
复制标题
DOI：
10.1007/s00445-015-0943-x
复制
发表时间：
2015-07-01
影响因子：
3.5
通讯作者：
Herrin, Jason S.
中科院分区：
文献类型：
--
作者：
Fontijn, Karen;Costa, Fidel;Herrin, Jason S.
公元1963年阿贡火山爆发是印度尼西亚世纪最重要的火山爆发之一，无论是就其爆炸性（火山爆炸性指数（VEI）为4+）还是因喷发期间排放约650万吨二氧化硫而产生的短期气候影响而言。由于阿贡有一个显着的潜力，以产生更多的富硫的爆炸性喷发在未来，并在2007年和2011年之间报告的地球物理动荡之后，我们调查了晚全新世火山灰地层记录，使用地层测井，地球化学和地质年代学分析。我们发现，阿贡有一个VEI的平均喷发频率>= 2-3喷发每世纪。晚全新世喷发记录主要是玄武安山质喷发，产生火山碎屑流和火山碎屑密度流。大约25%的喷发与1963年的事件相似或更大，这包括1843年的前一次喷发（估计为VEI 5，与之前估计的VEI 2相反）。后者代表了阿贡火山喷发的化学演化程度最高的产物（安山岩）之一。在晚全新世，更激烈的爆炸活动的时期交替与背景喷发率类似的其他俯冲带火山的时期。所有喷发产品在阿贡显示纹理复杂的矿物组合，主要由斜长石，单斜辉石，斜方辉石和橄榄石，表明经常性的开放系统的岩浆分异过程。我们建议，爆发的岩浆是玄武岩浆反复侵入玄武安山岩安山岩储层的结果，产生混合体玄武安山岩组成有限的成分变化。
The 1963 AD eruption of Agung volcano was one of the most significant twentieth century eruptions in Indonesia, both in terms of its explosivity (volcanic explosivity index (VEI) of 4+) and its short-term climatic impact as a result of around 6.5 Mt SO2 emitted during the eruption. Because Agung has a significant potential to generate more sulphur-rich explosive eruptions in the future and in the wake of reported geophysical unrest between 2007 and 2011, we investigated the Late Holocene tephrostratigraphic record of this volcano using stratigraphic logging, and geo-chemical and geochronological analyses. We show that Agung has an average eruptive frequency of one VEI >= 2-3 eruptions per century. The Late Holocene eruptive record is dominated by basaltic andesitic eruptions generating tephra fall and pyroclastic density currents. About 25 % of eruptions are of similar or larger magnitude than the 1963 AD event, and this includes the previous eruption of 1843 AD (estimated VEI 5, contrary to previous estimations of VEI 2). The latter represents one of the chemically most evolved products (andesite) erupted at Agung. In the Late Holocene, periods of more intense explosive activity alternated with periods of background eruptive rates similar to those at other subduction zone volcanoes. All eruptive products at Agung show a texturally complex mineral assemblage, dominated by plagioclase, clinopyroxene, orthopyroxene and olivine, suggesting recurring open-system processes of magmatic differentiation. We propose that erupted magmas are the result of repeated intrusions of basaltic magmas into basaltic andesitic to andesitic reservoirs producing a hybrid of bulk basaltic andesitic composition with limited compositional variations.