Slip‐rate‐dependent melt extraction at oceanic transform faults
Slip‐rate‐dependent melt extraction at oceanic transform faults
复制标题
大洋转换断层处依赖滑移率的熔体提取
DOI：
10.1002/2014gc005579
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
L. Montési
中科院分区：
文献类型：
--
作者：
Hailong Bai;L. Montési
海洋转换断层和相关的洋中脊之间的地壳厚度差异可以用熔体迁移和提取过程来解释。慢滑转换断层的重力正异常比相邻的扩张中心多，表明转换域地壳相对较薄;而在中扩张脊和快扩张脊，转换断层的重力负异常比相邻的扩张中心多，表明转换域地壳较厚。我们提出了数值模型再现这些观察结果，并推断熔体可以提取在快速滑动变换，但不是在缓慢滑动的。熔体浸提被建模为三步工艺。(1)熔体通过浮力驱动的多孔流动垂直移动，多孔流动由近垂直溶解通道增强。(2)熔体在热边界层底部的低渗透性屏障内衬的解压缩通道中积聚并沿着该通道行进。(3)当熔体进入熔体提取区时，熔体被提取到表面。需要2-4 km的熔体提取宽度和15-20 km的熔体提取深度来拟合与延伸到上地幔的大洋板块边界相关的构造损伤。地质特征、地球化学信号和地震活动特征反映了快速滑动和缓慢滑动转换过程中不同程度的岩浆活动，支持了我们的结论。我们还限制了地壳水平岩墙扩展的最大横向距离约为50-70 km。
Crustal thickness differences between oceanic transform faults and associated mid‐ocean ridges may be explained by melt migration and extraction processes. Slow‐slipping transform faults exhibit more positive gravity anomalies than the adjacent spreading centers, indicating relative thin crust in the transform domain, whereas at intermediate‐spreading and fast‐spreading ridges transform faults are characterized by more negative gravity anomalies than the adjacent spreading centers, indicating thick crust in the transform domain. We present numerical models reproducing these observations and infer that melt can be extracted at fast‐slipping transforms, but not at slow‐slipping ones. Melt extraction is modeled as a three‐step process. (1) Melt moves vertically through buoyancy‐driven porous flow enhanced by subvertical dissolution channels. (2) Melt accumulates in and travels along a decompaction channel lining a low‐permeability barrier at the base of the thermal boundary layer. (3) Melt is extracted to the surface when it enters a melt extraction zone. A melt extraction width of 2–4 km and a melt extraction depth of 15–20 km are needed to fit the tectonic damages associated with oceanic plate boundaries that reach into the upper mantle. Our conclusions are supported by the different degrees of magmatic activities exhibited at fast‐slipping and slow‐slipping transforms as reflected in geological features, geochemical signals, and seismic behaviors. We also constrain that the maximum lateral distance of crust‐level dike propagation is about 50–70 km.
洛加切夫海山下方的地震间隙：超慢洋中脊融化聚焦的指标？
影响因子：
5.2
作者：
Schlindwein;A. Demuth;W. H. Geissler ;W. Jokat
通讯作者：
W. Jokat
影响因子：
5.3
作者：
Miller, Kevin J.;Zhu, Wen-lu;Gaetani, Glenn A.
通讯作者：
Gaetani, Glenn A.