Do sea level variations influence mid-ocean ridge magma supply? A test using crustal thickness and bathymetry data from the East Pacific Rise
Do sea level variations influence mid-ocean ridge magma supply? A test using crustal thickness and bathymetry data from the East Pacific Rise
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DOI：
10.1016/j.epsl.2020.116121
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发表时间：
2020-04-01
影响因子：
5.3
通讯作者：
Langmuir, Charles H.
中科院分区：
文献类型：
--
作者：
Boulahanis, Bridgit;Carbotte, Suzanne M.;Langmuir, Charles H.
最近的研究表明，更新世冰川循环引起的海平面升降波动影响洋中脊的地幔熔融和火山爆发，模型预测了与海平面变化有关的洋壳厚度和海底测深的变化。对海底测深的分析发现，在与1/23、1/41和1/80-1/120 ka（-1）的米兰科维奇周期一致的频率上存在大量的光谱能量。然而，其他研究强调需要进行地壳厚度观测来检验“海平面假说”。在这里，我们通过分析从三维多道地震调查中得出的独特水深和地壳厚度数据集，研究了大洋中脊岩浆活动中气候驱动的周期性假说。东太平洋海隆从9度42'到57' N。地壳厚度数据跨越最后类似的235万年的年龄，并揭示了三个轴平行区200-800米厚的地壳。这些厚地壳脊的幅度和间距，这是最突出的东翼的脊，是一致的海平面调制地幔熔融的预测。在较长持续时间（470 ka）的海底测深数据中，脊的间隔也很明显。这些数据集的光谱分析表明，峰值集中在1/80 ka（-1）和局部1/41 ka（-1）在东翼的测深和地壳厚度。西翼光谱结果显示地壳厚度在1/100 ka（-1）和1/41 ka（-1）附近出现间歇性峰值，测深数据中没有相干峰值频率。我们的属性之间的差异，东，西翼的影响，空间可变的不对称扩展和小的变化，吸积轨迹。观测到的半扩展速率主要是更快的东与小脊跳跃转移地壳从西侧。滞后的海平面和地壳厚度之间的相互关系表明，最大时，后者是滞后的类似45万年，这使厚地壳区与类似的100万年的时期，较低的海平面。地壳厚度也直接与海底测深进行比较，表明补偿地形的一个组成部分，海底RMS起伏占地壳厚度变化的10%至29%。然而，从可变的不对称扩张和海底断层活动继承的复杂性也是显而易见的，结果为地壳增生过滤器如何调节地壳和海底地形中岩浆供应变化的记录提供了新的见解，虽然对这些海脊记录的统计分析的意义受到现有地壳厚度数据集持续时间短和不对称扩张效应的限制，地壳厚度以类似于80-100 ka的时间尺度变化的新观测结果需要一种机制，海平面假说提供了一种合理的解释。(C)2020爱思唯尔B. V.保留所有权利。
Recent studies suggest that eustatic sea level fluctuations induced by glacial cycles in the Pleistocene influence mantle-melting and volcanic eruptions at mid-ocean ridges, with models predicting variations in oceanic crustal thickness and seafloor bathymetry linked to sea level change. Analyses of seafloor bathymetry have found evidence of significant spectral energy at frequencies consistent with Milankovic cycles of 1/23, 1/41, and 1/80-1/120 ka(-1). However, other studies emphasize the need for crustal thickness observations to test the "sea level hypothesis".Here we investigate the hypothesis of climate driven periodicity in mid-ocean ridge magmatism through analysis of a unique bathymetry and crustal thickness dataset derived from a 3D multi-channel seismic investigation of the East Pacific Rise from 9 degrees 42' to 57'N. Crustal thickness data spans the last similar to 235 ka in age and reveals three axis-parallel zones of 200-800 m thicker crust. The amplitude and spacing of these thick crust ridges, which are most prominent on the east flank of the ridge, are consistent with predictions of sea level modulated mantle melting. Similarly spaced ridges are apparent in the longer duration (470 ka) seafloor bathymetry data. Spectral analysis of these datasets shows peaks centered near 1/80 ka(-1) and locally near 1/41 ka(-1) on the east flank in both bathymetry and crustal thickness. West flank spectral results show intermittent peaks near 1/100 ka(-1) and 1/41 ka(-1) in crustal thickness and no coherent peak frequencies in bathymetry data. We attribute differences between the east and west flank to the impacts of spatially variable asymmetric spreading and small changes in the locus of accretion. Observed half spreading rates are dominantly faster to the east with small ridge jumps transferring crust from the west flank. Lagged cross-correlations between sea level and crustal thickness indicate a maximum when the latter is lagged by similar to 45 ka, which align thick crust zones with the similar to 100 ka periods of lower sea level. Crustal thickness is also directly compared with seafloor bathymetry, indicating a component of compensated topography with RMS relief at the seafloor of 10 to 29% of crustal thickness variations. However, complexity inherited from variable asymmetric spreading and seafloor faulting is also apparent, and results provide new insights into how the crustal accretion filter modulates the recording of magma supply variations in the crust and in seafloor relief.While the significance of the statistical analysis of these ridge records is limited by the short duration of the available crustal thickness dataset and effects of asymmetric spreading, the novel observations of crustal thickness varying at timescales of similar to 80-100 ka require a mechanism, and the sea level hypothesis provides a plausible explanation. (C) 2020 Elsevier B.V. All rights reserved.