Fig. 3: ¹⁴³Nd/¹⁴⁴Nd measurements of samples.

a ¹⁴³Nd/¹⁴⁴Nd and ε_Nd plotted as a function of latitude. Black triangles = compilation of legacy analyses^17,30,31 (black triangles at 57.5^∘N = analyses for enriched seamount 14D¹⁶); pink/red diamonds and turquoise/blue circles with vertical bars = averaged and projected measurements for sites VSR-3/VSR-2 and VST-1/VST-2 (see ‘Methods’ for further details); vertical bars represent borehole range; dashed box = locus of axial measurements used to estimate average value of ε_Nd = 10.14 at the intersection of flowline and mid-oceanic ridge; vertical grey bar = onshore portion of Reykjanes Ridge on Reykjanes Peninsula. b ¹⁴³Nd/¹⁴⁴Nd and ε_Nd plotted as a function of distance from the ridge axis along the flowline and as a function of age, assuming a half-spreading rate of 1 cm/yr. Black triangle with vertical bar = average value for axial dredge samples located within the dashed box shown in (a), where the vertical bar represents the data range; turquoise/red/blue/pink circles/triangles/squares with vertical bars = values for VST-1/VSR-2/VST-2/VSR-3/FC sites, at each of which 10 downhole measurements were made (note that 2 values for Site FC, with very large uncertainties, are excluded here but included in Source Data); dashed line with labelled open red circles = calculated variation of ε_Nd as a function of distance/age, assuming a percentage increase of added pyroxenite melt component.