The eastern, passive margin of the North American continent is more heterogeneous than originally envisioned. Imaged by teleseismic body wave arrivals, both compressional V_p and shear V_sh, the lithospheric mantle of the stable, eastern North America contains rapid and large wave speed variations from the fast, older interior toward the slower, margin structures along the continental edge. At multiple regions at the continental edge, wave speeds indicate the presence of a small amount of melt, <1%–2%. Melt assessments were computed using a suite of mineralogical/petrological models to convert V_p and V_sh into absolute temperatures and melt fraction. Moreover, along the Atlantic margin, wave speeds are lower than expected for a previously rifted margin. Within the continent interior, wave speeds in the mantle lithosphere vary spatially at wavelengths, suggesting strong compositional and mineralogical influence likely a result of later stage alteration from volatile rich fluids.

中文翻译：

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北美东部的体波速度结构

北美大陆的东部被动边缘比最初设想的更加多样化。北美东部稳定的岩石圈地幔由远震体波到达（压缩V _p和剪切V _sh）成像，从大陆的较快内部向较慢的边缘结构包含了快速而大的波速变化。在大陆边缘的多个区域，波速表明存在少量熔体，<1％–2％。使用一套矿物学/岩石学模型计算熔体评估值以转换V _p和V _sh进入绝对温度和熔融分数。此外，沿着大西洋边缘，波速比以前裂谷的边缘要低。在大陆内部，地幔岩石圈中的波速在空间上随波长变化，表明强烈的成分和矿物学影响可能是由于富集挥发性流体在后期进行的改变所致。