Eruptive history of Middle Sister, Oregon Cascades, USA–Product of a late Pleistocene eruptive episode
Eruptive history of Middle Sister, Oregon Cascades, USA–Product of a late Pleistocene eruptive episode
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美国俄勒冈喀斯喀特中姐妹火山的喷发历史——晚更新世喷发事件的产物
DOI：
10.1130/ges01638.1
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发表时间：
2018
期刊：
影响因子：
2.5
通讯作者：
W. Hildreth
中科院分区：
文献类型：
--
作者：
A. Calvert;J. Fierstein;W. Hildreth
新的绘图，地球化学和氩地质年代学阐明了一个简短的，显着的事件设置在一个基性岩段的喀斯喀特弧。中间的妹妹是在35公里的时候建造的。晚更新世的一幕，从镁铁质，中间，和火山喷发相邻的主要流纹岩南姐妹。在三个姐妹篇火山群50 ka之前的喷发完全是镁铁质（<57重量%的SiO2），和几个玄武安山岩熔岩流可以追溯到中间姐妹或前身火山（150 ka之前）。熔岩流在Middle Sister喷发50-37 ka，其外围化学成分多样，有丰富的玄武安山岩，高硅流纹岩流，以及流纹岩和镁铁质岩浆混合产生的安山岩。在此期间，也在南姐妹山爆发了丰富的流纹岩和流纹英安岩。喷发活动在37-27 ka的中姐妹山暂停，但在南姐妹山继续大量的英安岩和安山岩熔岩。中间的姐妹爆发镁铁质，中间，和熔岩流27-15 ka，然后停止喷发。计算得出的整个三姐妹篇火山群的喷发速率翻了两番，从约0.2到约0.8立方千米/千年。在50 - 15 ka之间，主要是由于集中在中部和南部姐妹篇的喷发，该集群现在已经恢复到其适度的喷发输出，主要是远离成层火山。火山群的时间-体积结果进行比较，其他良好的映射，以及过时的成层火山的研究。几乎所有的中心都记录了类似的喷发量行为，长期的相对恒定的产出被大量喷发的短暂事件打断。除了三个姐妹篇，其中两个中心（山。马扎马、火山口湖、俄勒冈州和安第斯山脉南部的普耶韦/科顿考勒）记录了与大量喷发事件相关的显著成分变化。
New mapping, geochemistry, and argon geochronology illuminate a brief, remarkably silicic episode set in a mafic segment of the Cascade arc. Middle Sister was constructed during a 35-k.y. episode in the late Pleistocene from mafic, intermediate, and silicic eruptions adjacent to the primarily rhyolitic South Sister. Eruptions in the Three Sisters volcanic cluster prior to 50 ka were exclusively mafic (<57 wt% SiO2), and several basaltic andesite lava flows can be traced to Middle Sister or a predecessor volcano (prior to 150 ka). Lava flows erupted 50–37 ka at Middle Sister and on its periphery were chemically diverse, with abundant basaltic andesite, a high-silica rhyolite flow, and an andesite produced from mixing of a rhyolite and mafic magma. Abundant rhyolite and rhyodacite erupted in this interval also at South Sister. Eruptive activity paused at Middle Sister 37–27 ka but continued at South Sister with large volumes of dacite and andesite lavas. Middle Sister erupted mafic, intermediate, and silicic lava flows 27–15 ka and then ceased to erupt. Calculated eruptive rates for the entire Three Sisters volcanic cluster quadrupled from ~0.2 to ~0.8 km3/k.y. between 50 and 15 ka, largely owing to the eruptions focused at Middle and South Sisters, and the cluster has now returned to its modest eruptive output, mainly away from the stratovolcanoes. Time–volume results for the volcanic cluster are compared to studies of other well-mapped, well-dated stratovolcanoes. Nearly all centers record similar eruptive-volume behavior with long histories of relatively constant output punctuated by short episodes of voluminous eruptions. In addition to the Three Sisters, two of these centers (Mt. Mazama, Crater Lake, Oregon, and Puyehue/Cordon Caule in the southern Andes) record significant compositional changes associated with the voluminous eruptive episodes.