Controls on the magmatic fraction of extension at mid-ocean ridges
Controls on the magmatic fraction of extension at mid-ocean ridges
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DOI：
10.1016/j.epsl.2020.116541
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发表时间：
2020-11-01
影响因子：
5.3
通讯作者：
Dublanchet, Pierre
中科院分区：
文献类型：
--
作者：
Olive, Jean-Arthur;Dublanchet, Pierre
洋中脊岩浆侵位所容纳的板块分离部分M被认为是海底扩张模式的主要控制因素，但控制M本身的因素却知之甚少。在这里，我们提出了一个简单的理论框架解释M的短期周期的地震和岩脉侵入相互作用，通过调制的应力状态的山脊轴。在我们的模拟中，岩石圈轴向厚度和浅的补充岩浆岩床中的压力增加速率是控制M的两个主要参数。结合合理的情况下增加的压力积累率和岩石圈厚度的减少，随着扩张速率的增加，我们的模型适当括号可用的测量M从缓慢，中间和快速扩张的山脊。我们的模型进一步表明，海底扩张的主要模式（拆离断层作用、对称断层作用和完全岩浆作用）之间的转变对应于岩石圈轴向厚度的阈值，并且慢速和超低海脊处M的巨大变化直接反映了热结构的轴向变化。更一般地说，这意味着自下而上的岩浆加热和自上而下的热液冷却之间的平衡完全决定了脆性岩石圈中岩浆侵入的时间平均速率，从而决定了形状类似于地球表面2/3的洋中脊断层的模式。(C)2020由爱思唯尔公司出版
The fraction M of plate separation accommodated by magma emplacement at mid-ocean ridges has been recognized as the main control on seafloor spreading modes, yet the factors that control M itself are poorly understood. Here we put forward a simple theoretical framework explaining M in terms of short-term cycles of earthquakes and dike intrusions interacting with one another by modulating the stress state of the ridge axis. Axial lithospheric thickness and the rate of pressure build-up in shallow, replenishing magma sills are the two main parameters controlling M in our simulations. Combined with plausible scenarios for the increase of pressure build-up rate and the decrease of lithospheric thickness with increasing spreading rate, our model appropriately brackets available measurements of M from slow, intermediate, and fast-spreading ridges. Our model further suggests that the transitions between major modes of seafloor spreading (detachment faulting, symmetric faulting, and fully-magmatic) correspond to thresholds in axial lithospheric thickness, and that the great variability in M at slow and ultraslow ridges directly reflects along-axis variability in thermal structure. More generally, this implies that the balance between bottom-up magmatic heating and top-down hydrothermal cooling fully determines the time-averaged rate of magmatic intrusions in the brittle lithosphere, and thus the modes of mid-ocean ridge faulting which shape similar to 2/3 of Earth's surface. (C) 2020 Published by Elsevier B.V.