Petrology and geochemistry of three Early Holocene eruptions from Makushin Volcano, Alaska
Petrology and geochemistry of three Early Holocene eruptions from Makushin Volcano, Alaska
复制标题
阿拉斯加莫库辛火山三次早期全新世喷发的岩石学和地球化学
作者：
J. Larsen;J. Schaefer;J. Vallance;O. Neill
阿拉斯加的Makushin成层火山在距今9292年至6215年之间产生了三次高爆炸性的安山质喷发。这些喷发被非正式地命名为CFE（“火山口形成喷发”）、Nateekin和Driftwood Pumice，它们在今天的荷兰港和乌纳拉斯卡市地区沉积了大量的火山灰沉降物。本研究的重点是研究这些喷发的地球化学和岩石学，以更好地了解Makushin火山的危害，安山岩岩石成因和喷发触发镁铁质补给过程。CFE、Nateekin和Driftwood浮石样本的范围从玄武安山岩到英安岩，但主要是安山岩（SiO2 = 55.6至63.5wt%）。CFE沉积物在组成上略微分层，顶部CFE样品比底部沉积物（58至60重量% SiO2）略微更镁铁质（55至60重量% SiO2）。不平衡的矿物成分和纹理的CFE，Nateekin，浮木浮石样品，结合两个辉石测温和富安斜长石微晶（An 80）发现只有在顶部的CFE存款，提供证据，重复镁铁质充注触发这些喷发，与以前的研究一致。我们比较了Makushin的地球化学数据与先前研究中Makushin火山区（MVF）的卫星喷口和火山锥的数据，以研究可能的遗传关系。地球化学数据和流纹岩熔体模型运行在地壳存储条件（2千巴，fO 2 = Ni-NiO，和1.5和3.5重量% H2O）表明，没有单一的母岩浆供应MVF卫星锥和Makushin火山。相反，两种成分混合模型更适合MVF地球化学阵列。我们的Makushin结果比较以及与模型的主要安山岩火山，需要镁铁质补给动员安山岩和触发喷发。
Makushin stratovolcano, Alaska, produced three, highly explosive, andesitic eruptions between ~ 9292 and 6215 yBP. Those eruptions are informally named the CFE (“crater-forming eruption”), Nateekin, and Driftwood Pumice, and they deposited significant tephra fallout in the present-day port of Dutch Harbor and City of Unalaska area. The focus of this study is to examine the geochemistry and petrology of those eruptions to better understand Makushin volcano hazards, andesite petrogenesis and eruption triggering by mafic recharge processes. The CFE, Nateekin, and Driftwood Pumice samples range from basaltic andesite to dacite but are predominantly andesitic (SiO2 = 55.6 to 63.5 wt%). The CFE deposits are slightly compositionally stratified, with the top CFE samples slightly more mafic (55 to 60 wt% SiO2) than the basal deposits (58 to 60 wt% SiO2). Disequilibrium mineral compositions and textures in the CFE, Nateekin, and Driftwood Pumice samples, combined with two pyroxene thermometry and An-rich plagioclase microlites (An80) found only in the top of the CFE deposits, provide evidence for repetitive mafic recharge triggering those eruptions, consistent with prior studies. We compare the Makushin geochemical data with data from select satellite vents and cones in the Makushin Volcanic Field (MVF) from prior studies, to examine possible genetic relationships. The geochemical data and Rhyolite-MELTS models run at crustal storage conditions (2 kbar, fO2 = Ni-NiO, and 1.5 and 3.5 wt% H2O) indicate that no single parental magma supplies the MVF satellite cones and Makushin volcano. Instead, two component mixing models better fit the MVF geochemical array. Our Makushin results compare well with models of predominantly andesitic volcanoes that require mafic recharge to mobilize the andesites and trigger eruptions.
DOI：
10.1098/rsta.2018.0298
发表时间：
2019-02-25
影响因子：
5
作者：
Edmonds, Marie;Cashman, Katharine V.;Jackson, Matthew D.
通讯作者：
Jackson, Matthew D.