Three-dimensional thermomechanical modeling of oceanic spreading initiation and evolution
Three-dimensional thermomechanical modeling of oceanic spreading initiation and evolution
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DOI：
10.1016/j.pepi.2012.10.007
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发表时间：
2013-01-01
影响因子：
2.3
通讯作者：
Gerya, Taras V.
中科院分区：
文献类型：
--
作者：
Gerya, Taras V.
这项工作采用了高分辨率的三维热力学数值模式的初始海洋扩张，研究成核和长期演变的脊转换扩展模式。欧拉-拉格朗日粘塑性模型允许大的应变和帐户板块冷却热传导和热液循环，以及部分熔融的软流圈和洋壳生长的岩浆吸积。数值实验表明，海洋扩张模式强烈依赖于扩张中心的初始偏移量和断裂愈合速率的大小。得到了三种不同的长期扩展模式：（1）脊变换模式，（2）单脊模式和（3）中间板扩展中心模式。洋脊转换的海洋扩张模式从40-60公里的适度初始偏移逐渐形成，并在板块解体后数百万年完全确立。此外，在简单分析的基础上，论证了洋脊转换系统是一种长期的板块生长样式，它通常不同于初始的板块裂陷样式。脊转换系统的几何形状是由几何要求（180度旋转对称的开放空间占用），同时吸积和位移的新板块材料内的两个偏移扩展中心连接的持续流变弱转换故障。根据这些要求，大洋转换断层的特征展布平行取向是唯一热力学一致的稳态取向。数值试验的结果与自然界中观测到的初始和成熟的脊转换系统进行了比较。(C)2012 Elsevier B. V.保留所有权利。
This work employs high-resolution 3D thermomechanical numerical models of the incipient oceanic spreading to investigate nucleation and long-term evolution of ridge-transform spreading patterns. The Eulerian-Lagrangian visco-plastic model allows for large strains and accounts for plate cooling by both heat conduction and hydrothermal circulation as well as for partial melting of the asthenosphere and oceanic crust growth by magmatic accretion. According to the numerical experiments, the oceanic spreading pattern depends strongly on the initial offset of spreading centers and the magnitude of fracture healing rate. Three different characteristic long-term spreading modes are obtained: (I) ridge-transform patterns, (2) single ridges and (3) spreading centers with an intermediate plate. Ridge-transform oceanic spreading patterns form gradually from moderate initial offsets of 40-60 km and become fully established several million years after the plate breakup. Moreover, it is demonstrated on the basis of simple analyses that the ridge-transform system is a long-term plate growth pattern that is generally different from an initial plate rifting pattern. Geometry of the ridge-transform system is governed by geometrical requirements (180 degrees rotational symmetry for open space occupation) for simultaneous accretion and displacement of new plate material within two offset spreading centers connected by a sustaining rheologically weak transform fault. According to these requirements, the characteristic spreading-parallel orientation of oceanic transform faults is the only thermomechanically consistent steady state orientation. Results of numerical experiments compare well with both incipient and mature ridge-transform systems observed in nature. (C) 2012 Elsevier B.V. All rights reserved.