Mapping the mantle transition zone beneath Hawaii from Ps receiver functions: Evidence for a hot plume and cold mantle downwellings
Mapping the mantle transition zone beneath Hawaii from Ps receiver functions: Evidence for a hot plume and cold mantle downwellings
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DOI：
10.1016/j.epsl.2017.06.033
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发表时间：
2017-09-15
影响因子：
5.3
通讯作者：
Laske, Gabi
中科院分区：
文献类型：
--
作者：
Agius, Matthew R.;Rychert, Catherine A.;Laske, Gabi
夏威夷是热点火山活动的典型例子。经典的地幔柱理论认为，地幔柱从地核-地幔边界垂直上升到地表。然而，最近有人提出，烟柱的路径可能更复杂。确定夏威夷地幔柱地震异常的确切轨迹已被证明具有挑战性。我们确定了P-to-S （Ps）接收函数，利用陆地和海底地震仪记录的波形来阐明夏威夷群岛下410和660公里深度的地幔不连续，并对海底数据进行了新的倾斜和相干性校正。我们的三维深度迁移图提供了地幔过渡带不连续性的横向分辨率增强。410断裂带的特点是在夏威夷中部下方有一个加深的区域，周围有一个凸起的肩部。在660不连续面，岛屿的北部和南部为浅层地形，而西部和东部为深部地形异常。过渡带的厚度在横向上以13公里的深度变化：在夏威夷中北部较薄，在马蹄形特征上较厚。我们推断，在660公里深的地方，在410公里深的夏威夷中部，一个广阔的或可能是双重的上升流区域汇聚成一个单一的羽流。随着地幔柱上升得更远，最上层的地幔融化和流动导致冷物质向下涌，直至地幔柱周围至少410公里处。在其他背景下，这一结果支持复杂的羽流动力学，包括可能的非垂直羽流路径和邻近的地幔下沉。(C) 2017作者。Elsevier B.V.出版
Hawaii is the archetypal example of hotspot volcanism. Classic plume theory suggests a vertical plume ascent from the core-mantle boundary to the surface. However, recently it has been suggested that the plume path may be more complex. Determining the exact trajectory of the Hawaiian plume seismic anomaly in the mantle has proven challenging. We determine P-to-S (Ps) receiver functions to illuminate the 410- and 660-km depth mantle discontinuities beneath the Hawaiian Islands using waveforms recorded on land and ocean-bottom seismometers, applying new corrections for tilt and coherence to the ocean bottom data. Our 3-D depth-migrated maps provide enhanced lateral resolution of the mantle transition zone discontinuities. The 410 discontinuity is characterised by a deepened area beneath central Hawaii, surrounded by an elevated shoulder. At the 660 discontinuity, shallow topography is located to the north and far south of the islands, and a deep topographic anomaly is located far west and east. The transition zone thickness varies laterally by 13 km depth: thin beneath north-central Hawaii and thick farther away in a horseshoe-like feature. We infer that at 660-km depth a broad or possibly a double region of upwelling converges into a single plume beneath central Hawaii at 410-km depth. As the plume rises farther, uppermost mantle melting and flow results in the downwelling of cold material, down to at least 410 km surrounding the plume stem. This result in the context of others supports complex plume dynamics including a possible non-vertical plume path and adjacent mantle downwellings. (C) 2017 The Author(s). Published by Elsevier B.V.