Pacific geoid anomalies revisited in light of thermochemical oscillating domes in the lower mantle
Pacific geoid anomalies revisited in light of thermochemical oscillating domes in the lower mantle
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DOI：
10.1016/j.epsl.2011.03.040
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发表时间：
2011-06
影响因子：
5.3
通讯作者：
C. Cadio;I. Panet;A. Davaille;M. Diament;L. Métivier;O. Viron
中科院分区：
文献类型：
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作者：
C. Cadio;I. Panet;A. Davaille;M. Diament;L. Métivier;O. Viron
法属波利尼西亚上空的大地水准面低压先前被解释为与紧邻岩石圈下方的低粘度区域相关的上地幔上升流的特征。我们在这里提出使用新的高质量卫星重力数据和流体力学约束的替代解释。因此，我们讨论了中太平洋热点高度集中的起源，这仍然存在争议。使用小波分析的 GRACE 任务的卫星重力数据使我们能够更好地表征法属波利尼西亚的大地水准面低点和莱恩群岛链以东 600 公里处的大规模正大地水准面异常。我们证明了大地水准面异常与热化学振荡穹顶一致，并且在此假设下对它们的密度对比和上限深度进行了限制。中太平洋地幔在其发展的不同阶段将包含两个热化学不稳定性：一个上升的穹顶（较轻），大约从宇宙微波背景一直延伸到南太平洋超级涌流下方的过渡区，其顶部是产生短暂热点链的次生羽流，以及位于莱恩群岛链以东 600 公里区域下方的下地幔中的下沉穹顶（较致密）。板块重建进一步表明，后者也可能在 35 年产生了南莱恩群岛。前和沙茨基高地 140 M.y.以前，当它处于上升阶段时，南太平洋圆顶可能创造了达尔文海隆 100 年。之前在同一类型的事件中。
The geoid low over French Polynesia has been previously interpreted as the signature of an upper mantle upwelling associated with a low-viscosity zone located immediately below the lithosphere. We propose here an alternative explanation using new high-quality satellite gravity data and fluid mechanics constraints. We thus discuss the origin of the high concentration of hotspots in the Central Pacific, which is still debated. Satellite gravity data from the GRACE mission analyzed with wavelets allow us to better characterize the geoid low on French Polynesia and the large-scale positive geoid anomaly 600 km east of the Line Islands chain. We show that the geoid anomalies are consistent with thermochemical oscillating domes and we bring constraints on their density contrast and their upper limit depth under this hypothesis. The Central Pacific mantle would contain two thermochemical instabilities at different stages of their development: a rising dome (lighter) extending approximately from the CMB up to the transition zone beneath the South Pacific Superswell, toped by secondary plumes that generate short-lived hot spot chains, and a sinking dome (denser) in the lower mantle beneath the area located 600 km east of the Line Islands chain. Plate reconstructions further show that the latter could also have generated the Southern Line Islands 35 M.y. ago and Shatsky Rise 140 M.y. ago when it was in its ascending phase, while the South Pacific dome probably created Darwin Rise 100 M.y. ago in a same type of event.