Integrated volcanologic and petrologic analysis of the 1650AD eruption of Kolumbo submarine volcano, Greece
Integrated volcanologic and petrologic analysis of the 1650AD eruption of Kolumbo submarine volcano, Greece
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DOI：
10.1016/j.jvolgeores.2013.10.004
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发表时间：
2014-01-01
影响因子：
2.9
通讯作者：
Nomikou, Paraskevi
中科院分区：
文献类型：
--
作者：
Cantner, Kathleen;Carey, Steven;Nomikou, Paraskevi
科伦坡海底火山位于希腊圣托里尼岛东北7公里处的爱琴海，最后一次喷发是在公元1650年。海底和地面的爆炸活动持续了大约四个月，导致在火山口上部壁上形成了厚的（约250米）高度分层的浮石沉积物，以及分布在整个爱琴海南部的大量浮石筏。火山喷发柱从地面喷出的地下火山灰沉降物远至土耳其。远程操作车辆（ROV）视频观测从北部和西南部的火山口壁的横断面已被用于创建1650 AD矿床的地层序列。岩石学和地球化学分析表明，大部分矿床由白色、高泡状、稀疏斑岩、含黑云母流纹岩浮石组成。由斜长石为主的熔融包裹体测定的喷发前挥发物含量中值为6.5%。这对应于喷发前的储存压力约为200兆帕，或者假设含氢岩浆的深度约为6公里。将Kolumbo样品的天然玻璃成分和矿物组合与改良单倍花岗岩系统中其他类似成分流纹岩岩浆的实验结果进行比较，支持了压力和总挥发性的估计。火山爆发前的温度根据斜长石-熔体地热测量计算为750℃。科伦坡岩浆的高挥发物含量和大量地面喷发羽流的历史记录表明，这次爆发是由初级挥发物脱气驱动的。从历史记载和沉积地层可以推断出三个活动阶段；最初的海底喷发，在此期间火山碎屑物质积聚，喷口变浅；海底/陆上混合喷发羽流产生大量沉降物的过渡阶段；最后的水下喷发减弱。沉积过程包括海底沉降物、火山碎屑密度流和碎屑分离的复杂相互作用，这些相互作用与从海底到地面羽流的过渡有关，产生了高度分层的浮石层序。这是第一次研究在相对较浅的(
Kolumbo submarine volcano, located 7 km northeast of Santorini, Greece in the Aegean Sea, last erupted in 1650 AD. Submarine and subaerial explosive activity lasted for a period of about four months and led to the formation of thick (similar to 250 m) highly stratified pumice deposits on the upper crater walls as well as extensive pumice rafts that were dispersed throughout the southern Aegean Sea. Subaerial tephra fallout from eruption columns that breached the surface occurred as far east as Turkey.Remotely operated vehicle (ROV) video observations from transects of the northern and southwestern crater walls have been used to create stratigraphic sequences of the 1650 AD deposits. Petrographic and geochemical analyses reveal that the bulk of the deposits consists of white, highly vesicular, sparsely porphyritic, biotite-bearing rhyolite pumice. Pre-eruption volatile contents determined from plagioclase-hosted melt inclusions yield a median value of 6.5 wt.%. This corresponds to a pre-eruption storage pressure of similar to 200 MPa, or a depth of similar to 6 km assuming a H2O-saturated magma. Comparison of the natural glass compositions and mineral assemblage of the Kolumbo samples with experimental results on other rhyolite magmas of similar composition in the modified haplogranite system supports the pressure and total volatile estimates. Pre-eruption temperature was calculated as 750 degrees C based on plagioclase-melt geothermometry.The high volatile content of the Kolumbo magma and historical accounts of substantial subaerial eruption plumes suggest that the explosive eruption was driven by primary volatile degassing. Three phases of activity can be inferred from historical accounts and deposit stratigraphy; an initial submarine eruption during which time the vent became shallower as pyroclastic material accumulated, a transitional phase with substantial fallout from a hybrid submarine/subaerial eruption plume, and a final subaqueous phase as the eruption waned. Depositional processes included a complex interplay of submarine fallout, pyroclastic density currents, and clast segregation associated with the transition from submarine to subaerial plumes, producing a highly stratified pumiceous sequence. This is the first study of the in situ pyroclastic deposits of a well-documented silicic submarine explosive eruption in the relatively shallow (