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Monogenetic Near‐Island Seamounts in the Galápagos Archipelago
Geochemistry, Geophysics, Geosystems ( IF 4.480 ) Pub Date : 2020-11-06 , DOI: 10.1029/2020gc008914
D. M. Schwartz 1 , V. D. Wanless 1 , S. A. Soule 2 , M. D. Schmitz 1 , M. D. Kurz 3
Affiliation  

Rarely have small seamounts on the flanks of hotspot derived ocean‐island volcanoes been the targets of sampling, due to sparse high‐resolution mapping near ocean islands. In the Galápagos Archipelago, for instance, sampling has primarily targeted the subaerial volcanic edifices, with only a few studies focusing on large‐volume submarine features. Sampling restricted to these large volcanic features may present a selection bias, potentially resulting in a skewed view of magmatic and source processes because mature magmatic systems support mixing and volcanic accretion that overprints early magmatic stages. We demonstrate how finer‐scale sampling of satellite seamounts surrounding the volcanic islands in the Galápagos can be used to lessen this bias and thus, better constrain the evolution of these volcanoes. Seamounts were targeted in the vicinity of Floreana and Fernandina Islands, and between Santiago and Santa Cruz. In all regions, individual seamounts are typically monogenetic, but each seamount field requires multigenerational magmatic episodes to account for their geochemical variability. This study demonstrates that in the southern and eastern regions the seamounts are characterized by greater geochemical variability than the islands they surround but all three regions have (Sr‐Nd‐He) isotopic signatures that resemble neighboring islands. Variations in seamount chemistry from alkalic to tholeiitic near Fernandina support the concept that islands along the center of the hotspot track undergo greater mean depths of melting, as predicted by plume theory. Patterns of geochemical and isotopic enrichment of seamounts within each region support fine‐scale mantle heterogeneities in the mantle plume sourcing the Galápagos hotspot.

中文翻译:

加拉帕戈斯群岛的近海孤岛海山

由于海洋岛屿附近稀疏的高分辨率地图,很少有热点热点海岛火山两侧的小海山成为采样的目标。例如,在加拉帕戈斯群岛,采样主要针对空中火山岩,只有少数研究着眼于大容量海底特征。限于这些大型火山特征的采样可能会显示选择偏见,可能会导致岩浆和烃源过程的角度偏斜,因为成熟的岩浆系统支持混合和火山堆积,这覆盖了岩浆的早期阶段。我们演示了如何使用加拉帕戈斯群岛火山岛周围的卫星海山进行更精细的采样,以减轻这种偏差,从而更好地限制这些火山的演化。海山的目标是在Floreana和Fernandina群岛附近以及圣地亚哥和圣克鲁斯之间。在所有地区,单个海山通常都是单生的,但是每个海山场都需要多代岩浆事件,才能说明它们的地球化学变异性。这项研究表明,在南部和东部地区,海山的地球化学变异性大于其所环绕的岛屿,但所有三个区域都具有(Sr-Nd-He)同位素特征,类似于邻近的岛屿。费尔南迪纳附近海盐化学变化从碱性到富勒特质都支持这样一个概念,即沿热流道中心的岛屿经历了更大的平均融化深度,如羽流理论所预测的那样。
更新日期:2020-12-14
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