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首页> 外文期刊>Journal of Volcanology and Geothermal Research >A transition from strombolian to phreatomagmatic activity induced by a lava flow damming water in a valley
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A transition from strombolian to phreatomagmatic activity induced by a lava flow damming water in a valley

机译：山谷中熔岩流拦阻水引起的从暴发状到岩浆活动的转变

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The Golan Heights is a Plio-Pleistocene volcanic plateau. Cinder cones of Late Pleistocene age are very common in the eastern and northern Golan, while phreatomagmatic deposits are relatively rare and occur just in two structures — the maar of Birket Ram and the tuff ring of Mt. Avital. The complex of Mt. Avital includes two large cinder cones, a tuff ring with an elongated central depression and several basaltic flows, some of them breach the cinder cones. The (exposed) eruptive history of the complex includes (1) an early stage of basaltic lava flows, (2) strombolian activity and the buildup of the southern cinder cone, (3) a second stage of basaltic flows and the buildup of the northern cinder cone, and then a transition to (4) phreatomagmatic explosions. The phreatomagmatic deposits include surges, lapilli fallout deposits and coarse-grained lithic tuff breccias, which were found up to 200 m above the central depression. Basaltic and scoriaceous clasts are the main component of all deposits, while juvenile material is usually a minor component, almost absent in the lapilli deposits. It is suggested that the phreatomagmatic events in Mt. Avital were induced by the infiltration of water from a lake that existed in a nearby topographic low (Quneitra Valley). The lake was formed or significantly expanded at about 300 ka due to a lava flow that blocked the drainage of the valley to the west. The interlayering of tuff and scoria at the top of the northern cinder cone and the good preservation of a lava flow top breccia under the surges imply that the phreatomagmatic activity immediately followed and even coincided with the last stages of strombolian activity. It is suggested that the dry-wet transition was triggered by the effusion of the second stage lavas and the buildup of the northern cinder cone, which probably caused a reduction of pressure in the magmatic system and allowed the lake water an access to the magmatic system. The minimum age of the phreatomagmatic events is determined by a 54 ka Musterian site which lies directly on top of the tuff in the Quneitra Valley.
机译：戈兰高地是上新世-上新世的火山高原。晚更新世时期的煤渣锥在戈兰东部和北部很常见，而岩浆沉积则相对少见，仅出现在两个结构中-比克兰公岩和塔格环。至关重要的。山的复杂。 Avital包括两个大的煤渣锥，一个带拉长的中央凹陷的凝灰岩环和一些玄武岩流，其中一些突破了煤渣锥。该综合体的（暴露的）喷发历史包括（1）玄武岩熔岩流的早期阶段；（2）斯特伦伯活动和南部煤渣锥的聚集；（3）玄武岩流的第二阶段和北部的火山灰的聚集。煤渣锥，然后过渡到（4）吞噬岩爆。吞噬岩沉积物包括涌浪，青金石沉积物沉积物和粗粒岩性凝灰岩角砾岩，发现于中部凹陷上方200 m。玄武岩和胶质碎屑是所有沉积物的主要成分，而幼稚物质通常是次要成分，在lapilli沉积物中几乎不存在。建议在山中发生岩浆事件。生命是由附近地形低处（库尼特拉谷地）存在的一个湖中的水渗入引起的。由于熔岩流阻塞了山谷向西的排水，该湖在约300 ka处形成或显着扩张。北部煤渣锥顶部的凝灰岩和火山灰的夹层以及在浪涌作用下熔岩流顶部角砾岩的良好保存表明，岩浆岩浆活动立即发生，甚至恰好与连串活动的最后阶段重合。建议干湿过渡是由第二阶段熔岩的渗出和北部煤渣锥的堆积引起的，这可能导致岩浆系统压力降低，并使湖泊水进入岩浆系统。 。岩浆岩事件的最小年龄由一个54 ka的Musterian场地确定，该场地直接位于Quneitra谷的凝灰岩顶部。

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