Evidence for a deep mantle source for EM and HIMU domains from integrated geochemical and geophysical constraints
Evidence for a deep mantle source for EM and HIMU domains from integrated geochemical and geophysical constraints
复制标题
DOI：
10.1016/j.epsl.2017.11.052
复制
发表时间：
2018-02-15
影响因子：
5.3
通讯作者：
Konter, J. G.
中科院分区：
文献类型：
--
作者：
Jackson, M. G.;Becker, T. W.;Konter, J. G.
随着地质时期洋壳和陆壳(及相关沉积物)俯冲进入地幔，产生了具有不同地球化学特征的地幔区域，称为HIMU(高“Mu”，其中Mu=U-238/Pb-204)和EM(富集地幔)区域。热点熔岩中EM和HIMU地球化学特征的识别提供了俯冲地壳物质循环进入热点源区的证据。目前还不确定这些物质在地幔中的位置，一个关键的问题是，是否需要上涌的地幔热柱将具有EM和HIMU特征的地幔区域传输到热点下的浅地幔。因此，这项研究评估了海洋热区的极端EM和HIMU成分与这些热区之下存在(或不存在)受地震约束的地幔热柱之间的关系。我们根据全球地震横波速度模型绘制了三个现有的烟柱星表，这些烟柱星表显示了42个海洋热点下方是否存在烟柱。从每个热点中，我们选择了具有最高Pb206/Pb204组分和最低Nd143/Nd144组分的熔岩。我们发现，与地震定义的岩柱相关的热点比与岩柱无关的热点更有可能含有具有极端EM(ND-143/ND-144=20.0)成分的熔岩，但HIMU热点与岩柱的关联比EM热点更强。如果将极端EM和HIMU成分放在一起而不是分开考虑，则热柱与热点极端地球化学特征之间的关系的重要性将得到改善：来自地幔热柱的热点甚至比非热柱来源的热点更有可能表现出极端EM或极端HIMU特征。显著性检验还表明，具有极端EM或HIMU成分的热点更有可能与地幔热柱有关，而不是缺乏极端地球化学特征的热点。地震探测到的深部地幔热柱与热点地区极端EM或HIMU成分的存在之间的关系为这些地球化学域的深部地幔来源提供了证据。(C)2017爱思唯尔B.V.保留所有权利。
Subduction of oceanic and continental crust (and associated sediments) into the mantle over geologic time generates mantle domains with geochemically distinct signatures, referred to as HIMU (high "mu", where mu = U-238/Pb-204) and EM (enriched mantle) domains. Identification of EM and HIMU geochemical signatures in hotspot lavas provides evidence that subducted crustal materials are recycled into the source of hotspots. It remains uncertain where these materials are located in the mantle, and a key question is whether upwelling mantle plumes are required to transport mantle domains with EM and HIMU signatures to the shallow mantle beneath hotspots. Therefore, this study evaluates relationships between extreme EM and HIMU compositions at oceanic hotspots and the presence (or absence) of seismically-constrained mantle plumes beneath the hotspots. We draw on three existing plume catalogs based on global seismic shear-wave velocity models, and these plume catalogs indicate the presence or absence of a plume beneath each of 42 oceanic hotspots. From each hotspot, we select a lava with the highest Pb-206/Pb-204 composition and one with the lowest Nd-143/Nd-144 composition.We show that hotspots associated with seismically defined plumes show a greater likelihood of hosting lavas with either extreme EM (Nd-143/Nd-144 = 20.0) compositions than hotspots not associated with plumes, but HIMU hotspots show a stronger association with plumes than EM hotspots. The significance of the relationship between plumes and extreme geochemical signatures at hotspots improves if extreme EM and HIMU compositions are considered together instead of separately: hotspots sourced by mantle plumes are even more likely to exhibit extreme EM or extreme HIMU signatures than hotspots not sourced by plumes. The significance tests also show that hotspots with extreme EM or HIMU compositions are more likely to be associated with mantle plumes than hotspots that lack extreme geochemical signatures. A relationship between seismically detected deep mantle plumes and the presence of extreme EM or HIMU compositions at hotspots provides evidence for a deep mantle source for these geochemical domains. (C) 2017 Elsevier B.V. All rights reserved.