Three-dimensional geometry of concentric intrusive sheet swarms in the Geitafell and the Dyrfjoll volcanoes, eastern Iceland
Three-dimensional geometry of concentric intrusive sheet swarms in the Geitafell and the Dyrfjoll volcanoes, eastern Iceland
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DOI：
10.1029/2011gc003527
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发表时间：
2011-07-28
影响因子：
3.5
通讯作者：
Gustafsson, Ludvik E.
中科院分区：
文献类型：
--
作者：
Burchardt, Steffi;Tanner, David C.;Gustafsson, Ludvik E.
对冰岛东部Geitafell和Dyrfjoll深侵蚀火山中的席状侵入体（倾斜席状和岩墙）进行了地表研究，以确定其岩浆源的位置、深度和大小。为了这个目的，倾斜片的测量方向投影在三维空间中，以产生片群几何形状的模型。对于Geitafell火山，大部分的表收敛到一个共同的焦点区域，直径至少为4至7公里，其位置与几个辉长岩体暴露在表面相吻合。假设这些辉长岩代表岩浆房的一部分，供给倾斜的席，源深度为2至4公里以下的古陆表面推导。第二个，年轻的一群陡倾岩席横切辉长岩和第一个岩群的成员。估计第二个震群的震源位于震群1震源的东南方向，低于目前的暴露水平，比第一个震群震源更深。对于Dyrfjoll火山，我们表明，表可以分为七个不同的子集，其中三个可以被解释为群。最突出的虫群是恩贾德维克片群，它向恩贾德维克山谷中位于古陆地表面以下1.5至4公里深处的一个数公里宽的区域聚集。两个额外的岩浆源被假定为位于东北和西南的主要来源。横切关系表明，同时期，以及连续活动的不同岩浆房，但没有一个可分辨的空间趋势。因此，Dyrfjoll火山是一个复杂的火山群的一部分，该火山群远远超出了研究区域，可以作为嵌套火山（如Askja）的化石模拟，而在Geitafell，席状群似乎起源于同一时间的一个焦点，从而定义了一个单一的中央火山复合体，如Krafla火山。
Sheet intrusions (inclined sheets and dykes) in the deeply eroded volcanoes of Geitafell and Dyrfjoll, eastern Iceland, were studied at the surface to identify the location, depth, and size of their magmatic source(s). For this purpose, the measured orientations of inclined sheets were projected in three dimensions to produce models of sheet swarm geometries. For the Geitafell Volcano, the majority of sheets converge toward a common focal area with a diameter of at least 4 to 7 km, the location of which coincides with several gabbro bodies exposed at the surface. Assuming that these gabbros represent part of the magma chamber feeding the inclined sheets, a source depth of 2 to 4 km below the paleoland surface is derived. A second, younger swarm of steeply dipping sheets crosscuts this gabbro and members of the first swarm. The source of this second swarm is estimated to be located to the SE of the source of Swarm 1, below the present-day level of exposure and deeper than the source of the first swarm. For the Dyrfjoll Volcano, we show that the sheets can be divided into seven different subsets, three of which can be interpreted as swarms. The most prominent swarm, the Njardvik Sheet Swarm, converges toward a several kilometers wide area in the Njardvik Valley at a depth of 1.5 to 4 km below the paleoland surface. Two additional magmatic sources are postulated to be located to the northeast and southwest of the main source. Crosscutting relationships indicate contemporaneous, as well as successive activity of different magma chambers, but without a resolvable spatial trend. The Dyrfjoll Volcano is thus part of a complex volcanic cluster that extends far beyond the study area and can serve as fossil analog for nested volcanoes such as Askja, whereas in Geitafell, the sheet swarms seem to have originated from a single focus at one time, thus defining a single central volcanic complex, such as Krafla Volcano.