Crustal accretion and dynamic feedback on mantle melting of a ridge centred plume: The Iceland case☆
Crustal accretion and dynamic feedback on mantle melting of a ridge centred plume: The Iceland case☆
复制标题
地壳增生和以山脊为中心的地幔柱熔化的动态反馈：冰岛案例â
DOI：
10.1016/j.tecto.2006.08.012
复制
发表时间：
2008
期刊：
影响因子：
2.9
通讯作者：
G. Marquart
中科院分区：
文献类型：
--
作者：
Schmeling;G. Marquart
地幔柱与洋脊相互作用的一个主要后果是增加了熔体的产生和相关的地壳生成。据报告，冰岛的地壳厚度高达20至40公里。地壳地震速度很高，必须用热效应或化学效应来解释。在本文的第一部分中，我们解决的问题是否提取熔融的羽下缓慢蔓延的山脊和沉积提取的玄武岩卷在表面产生的地幔熔融的动态反馈机制。为了研究这个问题，我们解决了对流方程的脊为中心的羽流与非牛顿流变学，包括熔化，熔体提取与沉积的冷地壳在表面的模型，并使用简化的方法压实。如果每一沉积玄武岩层的厚度小于大约1公里，那么冷地壳的假设是合理的。根据浮力通量的羽流，地壳厚度在10和40公里之间的建模，显示出特征的倾斜结构类似于裂谷向倾斜玄武岩层的东部和西部冰岛。比较由此产生的地壳厚度和岩浆生成速率与模型中，地壳沉积的动态效应已被抑制表明，熔体生成下的一个缓慢蔓延的脊大大阻尼的动态反馈机制，如果羽浮力通量超过400至600公斤/秒。根据观测到的冰岛地壳厚度，我们的模型预测羽流浮力通量为1140公斤/秒。在第二部分中，我们研究了冰岛地壳的吸积的热-力学模型更详细的基础上的Navier-Stokes方程，热输运和质量守恒方程，包括体积源。热的（1200 °C）熔融地壳物质在不同的地壳源区以恒定的速率注入新形成的地壳中：a）深而广泛的岩墙和岩床就位，包括地壳底侵作用，B）浅至中地壳水平的岩浆房，以及c）与火山中心相连的浅部裂隙群中的表面挤出物和侵入物。我们通过标记方法识别来自不同来源区域的材料。这些源区的相对优势各不相同，地壳结构也随之演变，显示出浅倾的上地壳层，倾角在10 °至15°之间。地壳热结构有冷壳（浅源区为主）和热壳（深源区为主）之分。我们使用地震活动最大深度的观测来限制650 °C等温线的深度，并使用下地壳的地震学推断来限制该地区的温度。最好的协议与我们的模型是实现地壳形成占主导地位的深岩墙和底侵相当大的影响岩浆房增生。
A major consequence of the interaction of a plume with an oceanic ridge is the enhanced melt production and associated crust generation. In the case of Iceland crustal thickness as large as 20 to 40 km has been reported. Crustal seismic velocities are high, and have to be explained by thermal or chemical effects. In the first part of the paper we address the question whether extraction of melt out of the plume beneath a slowly spreading ridge and deposition of extracted basalt volumes at the surface produces a dynamic feedback mechanism on mantle melting. To study this question we solve the convection equations for a ridge centred plume with non-Newtonian rheology including melting, melt extraction associated with deposition of cold crust at the surface of the model, and using a simplified approach for compaction. The assumption of cold crust is justified if the thickness of each deposited basaltic layer is less than roughly 1 km. Depending on the buoyancy flux of the plume, crustal thicknesses between 10 and 40 km are modelled, showing characteristic dipping structures resembling the rift-ward dipping basaltic layers of East- and Western Iceland. Comparing the resulting crustal thickness and magma generation rate with models in which the dynamic effect of crust deposition has been suppressed indicates, that melt generation beneath a slowly spreading ridge is considerably damped by the dynamic feedback mechanism if the plume buoyancy flux exceeds 400 to 600 kg/s. Based on the observed crustal thickness of Iceland our models predict a plume buoyancy flux of 1140 kg/s. In the second part we study the accretion of the Icelandic crust by a thermo-mechanical model in more detail based on the Navier–Stokes-, the heat transport and the mass conservation equations including volumetric sources. Hot (1200 °C) molten crustal material is injected into the newly forming crust with a constant rate at different crustal source regions: a) deep, widespread emplacement of dykes and sills including crustal underplating, b) magma chambers at shallow to mid-crustal level, and c) surface extrusions and intrusions in fissure swarms at shallow depth connected to volcanic centres. We identify the material from the different source regions by a marker approach. Varying the relative dominance of these source regions, characteristic crustal structures evolve, showing shallow dipping upper crustal layers with dip angles between 10 and 15°. The thermal structure of the crust varies between cold crust (shallow-source region dominating) and hot crust (deep-source region dominating). We use observations of maximum depth of seismicity to constrain the depth of the 650 °C isotherm and seismological inferences on the lower crust to constrain temperatures in that region. The best agreement with our models is achieved for crust formation dominated by deep dykes and underplating with a considerable influence of magma chamber accretion.
登录
查看更多内容
冰岛北部活动转换断层 Tjörnes 断裂带的地震构造分析
影响因子：
--
作者：
S. Rögnvaldsson;Agust Gudmundsson;R. Slunga
通讯作者：
R. Slunga
地幔柱的熔体生产率
DOI：
10.1098/rsta.1993.0010
发表时间：
1993
期刊：
Philosophical Transactions of the Royal Society of London. Series A: Physical and Engineering Sciences
影响因子：
--
作者：
R. White
通讯作者：
R. White
冰岛下方的地震异常延伸至地幔过渡带，但没有更深
DOI：
--
发表时间：
2000
期刊：
影响因子：
--
作者：
G. Foulger;M. J. Pritchard;B. Julian;J. R. Evans;R. Allen;G. Nolet;W. J. Morgan;B. Bergsson;P. Erlendsson;S. Jakobsdóttir;S. Ragnarsson;R. Stefánsson;K. Vogfjörd
通讯作者：
K. Vogfjörd
以山脊为中心的羽流的温度和融化，适用于冰岛。
影响因子：
2.8
作者：
T. Ruedas;H. Schmeling;G. Marquart;A. Kreutzmann;A. Junge
通讯作者：
A. Junge
冰岛东北部克拉夫拉裂谷期岩浆注入与板块分歧机制研究
DOI：
--
发表时间：
1985
期刊：
影响因子：
--
作者：
G. Marquart;W. Jacoby
通讯作者：
W. Jacoby