Crustal flow beneath Iceland
Crustal flow beneath Iceland
复制标题
冰岛下方的地壳流
DOI：
10.1029/2004jb003592
复制
发表时间：
2005
影响因子：
--
通讯作者：
J. Maclennan
中科院分区：
文献类型：
--
作者：
S. Jones;J. Maclennan
[1] 理论和实验研究表明，当洋壳温度高于约 800°C 时，地壳厚度的变化会驱动较低的地壳流动。我们研究了冰岛下方地壳流的性质，其中零年龄地壳的厚度在 100 公里的距离内从 20 公里以下到 40 公里以上不等，几公里深度以下的温度超过 1000°C。我们使用具有与深度相关的粘度的二维通道流方程来模拟地壳流的区域特征。该模型预测了冰岛海岸零年龄地壳和离轴地壳之间观察到的地壳厚度衰减对比，以及随着板块远离裂谷轴而形成的急剧莫霍面台阶。随着板冷却增加粘度，这些特征被锁定到位。当固相线粘度为 1018 Pa·s 时，观测结果与模型预测最匹配，这与根据与冰川消融和板块边界过程相关的变形速率估计的粘度一致。地壳流的作用是消除脊-羽流相互作用的地壳厚度记忆，因此冰岛地壳厚度图既不能用于导出详细的羽流通量历史，也不能详细测试冰岛羽流中心相对于其他热点是否固定。冰岛下方的地壳流是一种异常清晰的例子，这种流被假设用来解释大陆现象，包括变质核复合体的折返以及在主要碰撞带中伸展地形和尖锐边缘高原地形中低角度脱离的相关发展。
[1] Theoretical and experimental studies indicate that when oceanic crust is hotter than about 800°C, variations in crustal thickness drive lower crustal flow. We investigate the nature of crustal flow beneath Iceland, where zero-age crust varies in thickness from under 20 km to over 40 km over a distance of 100 km and temperatures exceed 1000°C below depths of a few kilometers. We model the regional characteristics of crustal flow using the two-dimensional channel flow equation with depth-dependent viscosity. The model predicts the observed decay in crustal thickness contrasts between zero-age and off-axis crust on shore Iceland and development of a sharp Moho step as the plate moves away from the rift axis. These features become locked in place as plate cooling increases the viscosity. Observations are best matched by model predictions when the solidus viscosity is of order 1018 Pa s, in agreement with viscosity estimates from deformation rates associated with deglaciation and plate boundary processes. Crustal flow acts to erase the crustal thickness memory of ridge-plume interaction, so that maps of Icelandic crustal thickness can be used neither to derive a detailed plume flux history nor to test in detail whether the Iceland Plume center is fixed relative to other hot spots. Crustal flow beneath Iceland is an unusually clear example of the kind of flow postulated to explain continental phenomena including exhumation of metamorphic core complexes and associated development of low-angle detachments within extensional terrains and sharp-edged plateau topography in major collisional belts.