Similar dyke thickness variation across three volcanic rifts in the North Atlantic region: Implications for intrusion mechanisms
Similar dyke thickness variation across three volcanic rifts in the North Atlantic region: Implications for intrusion mechanisms
复制标题
DOI：
10.1016/j.lithos.2006.03.030
复制
发表时间：
2006-11-01
期刊：
影响因子：
3.5
通讯作者：
Klausen, M. B.
中科院分区：
文献类型：
--
作者：
Klausen, M. B.
1935年基性岩墙的厚度已经通过细致的测绘记录下来，包括（1）东格陵兰沿海岩墙群，（2）冰岛东南部的一个灭绝裂谷带，（3）瑞典加里东山脉内的一个仰冲岩墙群段。在这三种情况下，几乎每一个堤坝的厚度沿着良好暴露和连贯的剖面段可以测量和分析。统计数据表明，堤坝厚度分布往往是负指数（即，在任何给定的段内，与对数正态相比，回归的逆指数系数表示更复杂的平均厚度。对于所有三个岩墙剖面，从较厚的岩墙沿着边缘的群到较窄的岩墙沿着其轴，平均厚度有类似的减少。此外，两个剖面内的横切关系表明，平均岩墙厚度随时间而减小。岩墙厚度的随机分布最有可能是由岩墙初始化决定的，在板块分离的恒定速率期间，岩墙在随机时间间隔释放差异应力。有人认为，堤坝的厚度不显着变化的深度范围内，这些堤坝群暴露，允许系统的空间和时间的平均堤坝厚度的变化与其他因素有关。结果主要涉及的深度下地壳岩浆水库，逐步上升到较浅的海拔下的活火山裂谷。作为一种替代方案，或与此模型相结合，应力集中对上升的波峰的地壳下岩浆库可能会增加平均频率的随机释放的差异应力，导致移动快速注入较薄的岩墙向群中心和时间。将平均岩墙厚度与地壳深度相关联，我最终得出了一个经验性的岩墙厚度/高度比，近似于2 x 10（-4），但厚度/长度比是可变的，以适应群的椭圆形表面轮廓。(C)2006年由Elsevier B. V.出版
The thicknesses of 1935 mafic dykes have been recorded through meticulous mapping across (1) the East Greenland coastal dyke swarm, (2) an extinct rift zone in SE Iceland and (3) an obducted dyke swarm segment within the Swedish Caledonides. In all three cases, the thickness of almost every dyke along well-exposed and coherent profile segments could be measured and analyzed. Statistics show that dyke thickness distributions more often are negative exponential (i.e., random) than log-normal within any given segment, with a regression's inverse exponential coefficient representing a more sophisticated average thickness. For all three dyke profiles, there is a similar decrease in average thickness from thicker dykes along the margin of the swarm to narrower dykes along its axis. Cross cutting relationships within two profiles, furthermore, suggest that the average dyke thickness decreased with time.The random thickness distribution of dykes is most likely governed by dyke initiations, releasing differential stresses at random time intervals during constant rates of plate separation. It is argued that the thickness of a dyke does not change significantly within the depth ranges that these dyke swarms are exposed, allowing systematic spatial and temporal changes in average dyke thicknesses to be related to other factors. Results are primarily related to the depth of an underlying sub-crustal magma reservoir, which progressively rose to shallower elevations beneath an active volcanic rift. As an alternative, or in conjunction with this model, stress concentrations towards the rising crest of a sub-crustal magma reservoir might increase the average frequency of randomly released differential stresses, leading to move rapid injections of thinner dyke toward swarm centres and with time. Correlating average dyke thicknesses to crustal depths, I end up with an empirical dyke thickness/height ratio of similar to 2 x 10(-4), yet variable thickness/length ratio in order to accommodate the elliptical surface outline of swarms. (C) 2006 Published by Elsevier B.V.