Rothenberg scoria cone, East Eifel: a complex Strombolian and phreatomagmatic volcano
Rothenberg scoria cone, East Eifel: a complex Strombolian and phreatomagmatic volcano
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东埃菲尔的罗森伯格火山渣锥：一座复杂的斯特龙博利火山和热岩浆火山
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发表时间：
1989
期刊：
影响因子：
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通讯作者：
H. Schmincke
中科院分区：
文献类型：
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作者：
B. Houghton;H. Schmincke
Rothenberg Score锥体Eifel是由三个斯特龙博尔期和三个金云母岩浆喷发阶段交替形成的。火山喷发发生在一条600米长的裂缝上，从多达六个喷口喷发，形成了早期的凝灰岩环，然后是两个合并的蝎子锥。由于外部水的供应严重有限，斯特龙博勒火山作用在体积上占主导地位。岩浆/水的相互作用只发生在任何喷口喷发的开始阶段，当时流量很低，碎裂面低于地下水位。云雾岩浆矿床由分选较好的落层和少量涌浪沉积组成。它们含有幼年碎屑，具有广泛的泡孔和粒度，这意味着由云雾状爆炸抛出的物质组合具有相当大的不均一性。在任何喷口从云雾岩浆喷发到斯特龙博尔式火山喷发的转变是迅速和不可逆转的，即使在每个喷发期结束时喷发速度被推断为已经减弱，斯特龙博尔式火山作用仍然存在，因为当时正在生长的圆锥体中碎裂表面很高，水无法进入岩浆。Stronbolian沉积相对均一，分别由开放喷口喷发和喷口部分堵塞期间喷发的粗粒和细粒交替、分选良好的落层组成。斯特龙博利亚喷发的时间间隔总是在自由脱气岩浆的释放和脱气岩浆在喷口蓄积、生长锥体坍塌和碎屑通过喷口反复循环等过程之间保持微妙的平衡。Rothenberg锥体不稳定的明显证据保存在圆锥体内壁沉积物中的许多不整合中。斯特龙博利阶段的结束可能标志着向喷口供应的岩浆减少，并伴随着火山口中熔岩的积水和停滞。
Rothenberg scoria cone Eifel formed by an alternation of three Strombolian and three phreatomagmatic eruptive phases. Eruptions took place from up to six vents on a 600 m-long fissure, building an early tuff ring and then two coalescing scoria cones. Strombolian volcanism dominated volumetrically, as the supply of external water was severely limited. Magma/water interaction only occurred during the opening stages of eruption at any vent, when discharge rates were low and the fragmentation surface was below the water table. The phreatomagmatic deposits consist of relatively well-sorted fall beds and only minor surge deposits. They contain juvenile clasts with a wide range of vesicularity and grain size, implying considerable heterogeneity in the assemblage of material ejected by the phreatomagmatic explosions. the transition from phreatomagmatic to Strombolian eruption at any vent was rapid and irreversible, and Strombolian volcanism persisted even when eruption rates are inferred to have waned at the close of each eruptive phase as, by then, the fragmentation surfaces were high in the growing cones and water was denied access to the magma. The Strombolian deposits are relatively homogenous, consisting of alternating coarser- and finer-grained, well-sorted fall beds erupted during periods of open-vent eruption and partial blockage of the vent respectively. The intervals of Strombolian eruption were always a delicate balance between discharge of freely degassing magma and processes such as ponding of degassed magma in the vent, collapse of the growing cones, and repeated recycling of clasts through the vent. Clear evidence of the instability of the Rothenberg cones is preserved in numerous unconformities within deposits of the inner walls of the cones. The close of Strombolian phases was probably marked by a decreasing supply of magma to the vents accompanied by ponding and stagnation of lava in the craters.