We report a reanalysis of active‐source wide‐angle seismic data collected along the Greenland‐Iceland Ridge during the 1996 Seismic Investigation of the Greenland Margin (SIGMA) experiment. Interpreting the crustal structure of volcanic rifted margins has suffered from nonuniqueness because thick crust at the continent‐ocean transition may not be totally of igneous origin. In this regard, the Greenland‐Iceland Ridge presents a unique opportunity because, together with the Faroe‐Iceland Ridge, it is generally considered to constitute the Iceland hotspot track, and as such, the bulk of its crust may be considered to be of igneous origin. From 15 ocean‐bottom instruments deployed along a 290‐km‐long refraction transect, we collect 5,383 P g and 1,118 P m P travel times, and we use joint refraction and reflection seismic tomography with adaptive importance sampling to invert them to construct a two‐dimensional compressional wave speed (V _p ) model across the Greenland‐Iceland Ridge. Based on the covariation of crustal thickness and V _p , the western part of the transect may be almost entirely continental. Even the eastern part could include a significant fraction of preexisting continental crust. When considered together with the seismic structure of the Icelandic crust and its geochemical characteristics, our results suggest that the putative Iceland mantle plume could be considerably weaker than commonly assumed.

中文翻译：

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基于联合折射和反射地震层析成像的格陵兰-冰岛脊地壳结构

我们报告了对1996年格陵兰边缘的地震调查（SIGMA）实验中沿格陵兰-冰岛脊收集的主动源广角地震数据的重新分析。由于大陆-海洋过渡带的厚地壳可能并非完全是火成岩，因此解释火山裂谷边缘的地壳结构一直存在不唯一性。在这方面，格陵兰-冰岛山脊提供了独特的机会，因为它通常与法罗-冰岛山脊一起被认为是冰岛的热点路径，因此，其大部分地壳可能被认为是火成岩的。起源。从沿着290公里长的折射样条线部署的15台海底仪器中，我们收集到5,383 P g和1,118 P m P行进时间，我们使用联合折射和反射地震层析成像以及具有自适应重要性的采样方法将它们反转，以构建横跨格陵兰-冰岛脊的二维压缩波速度（V _p）模型。基于地壳厚度和V _p的协变，该断面的西部可能几乎是整个大陆。甚至东部也可能包含相当一部分先前存在的大陆壳。当与冰岛地壳的地震结构及其地球化学特征一起考虑时，我们的结果表明，假定的冰岛地幔柱可能比通常假定的要弱得多。