Late Pleistocene and Holocene Caldera-Forming Eruptions of Okmok Caldera, Aleutian Islands, Alaska
Late Pleistocene and Holocene Caldera-Forming Eruptions of Okmok Caldera, Aleutian Islands, Alaska
复制标题
阿拉斯加阿留申群岛奥克莫克火山口的晚更新世和全新世火山喷发
DOI：
10.1029/172gm24
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
C. Nye
中科院分区：
文献类型：
--
作者：
J. Larsen;C. Neal;J. Schaefer;J. Beget;C. Nye
奥克莫克火山位于阿拉斯加阿留申岛弧中部，在过去约 12,000 年内发生了两次形成火山口的喷发。这项研究描述了这两次喷发的地层学、成分和岩石学。两次喷发最初都产生了少量的长英质岩浆，随后产生了大量的安山岩和玄武质安山岩。奥克莫克 I 号喷发在乌姆纳克岛产生了 >30 km 3 DRE 物质，奥克莫克 II 号喷发产生了约 15 km 3 的物质。然而，在这两次事件期间，此处未考虑的很大一部分物质被沉积到海洋中。奥克莫克 I 火山碎屑流沉积物包含与雪/冰相互作用的证据，特别是沿着火山口的北侧。尽管奥克莫克一号和二号喷发都涉及岩浆成分，但大量（>15km 3 ）富含挥发分的中镁铁质岩浆在浅地壳中的积累可能为灾难性喷发提供驱动力。与奥克莫克 II 相关的凝集沉积物表明，在火山口塌陷的同时，熔岩喷发充满活力，类似于新赫布里底群岛等镁铁质中型火山口形成沉积物的其他描述。
Okmok volcano, in the central Aleutian arc, Alaska, produced two caldera-forming eruptions within the last ∼12,000 years. This study describes the stratigraphy, composition, and petrology of those two eruptions. Both eruptions initially produced small volumes of felsic magmas, followed by voluminous andesite and basaltic andesite. The Okmok I eruption produced >30 km 3 DRE of material on Umnak Island, and Okmok II ∼15 km 3 . However, a significant proportion of material not accounted for here was deposited into the oceans during both events. The Okmok I pyroclastic flow deposits contain evidence for interaction with snow/ice, particularly along the northern flanks of the caldera. Although both Okmok I and II eruptions involved a phreatomagmatic component, the accumulation of a large volume (>15km 3 ) of volatile-rich, mafic-intermediate magma in the shallow crust may provide the driving force for the catastrophic eruptions. Agglutinate deposits associated with Okmok II indicate energetic lava fountaining simultaneous with caldera-collapse, similar to other descriptions of mafic-intermediate caldera-forming deposits such as in the New Hebrides.