Whole rock Hafnium (Hf) isotope data for mid-oceanic ridge basalt (MORB) samples from the Reykjanes ridge, Arctic Ocean, Equatorial MAR, South MAR, SEIR. The Hf isotope results are not yet published but will contribute to the mantle characterisation efforts detailed in Béguelin et al. (2025) (https://doi.org/10.1029/2025GC012357). Mid-Ocean Ridge Basalt (MORB) glasses were crushed and sieved to ~600 µm. Chips were then hand-piked under a binocular microscope to remove alteration (only optically clear chips selected). Hf fractions were purified using the column chemistry protocol of Béguelin et al. (2017) and references therein (https://doi.org/10.1016/j.gca.2017.09.015). Hf isotope ratios were measured on a Nu Instruments Plasma II mass spectrometer equipped with an Aridus desolvating nebuliser, on 50 ppb solutions. Accuracy and precision were monitored with repeated measurements of the JMC-475 standard (reported in dataset). Scanning Electron Microscopy-Energy Dispersive Spectrometry (SEM EDS) and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) major and trace elements maps of eclogites from the Raspas complex (Ecuador). Samples were prepared as 1-inch epoxy mounts. Samples are described in John et al. (2010) (https://doi.org/10.1007/s00410-009-0427-0). The objective of this (present) work is to trace U, Pb and Th fluxes during subduction, as documented by obducted eclogites. Dataset includes SEM mapping of major elements with a Zeiss Sigma HD Field Emission Gun Analytical Scanning Electron Microscope (SEM) using energy dispersive X-ray spectroscopy (EDS). Elements measured are Fe, Ca, Cu, Ni, Mn, K, Na, Al, Mg, Ti, O, Cr, S, Si, P, Zr. Resolution is 25µm. Dataset also includes LA-ICP-MS mapping of trace elements using an Elemental Scientific ESL213 laser coupled to a Thermo Scientific iCap Q mass spectrometer. Elements measured are Rb, Sr, Mo, Cs, La, Yb, Pb, Th, U. Parameters: Raster spacing (resolution): 40µm, scan speed: 80 µm/s, rep rate: 20 Hz, fluence: 4.5 J/cm2, dwell time per element: 50 ms, injector: ESI dual concentric injector (DCI). SEM data are in weight %, LA-ICP-MS data are in µg/g (ppm). Data are unpublished, but further details can be found in the poster included with the dataset. Dataset was produced at the School of Earth and Environmental Sciences, Cardiff University, in the context of NERC grant NE/T012633/1 Mantle Circulation Constrained (MC2): A multidisciplinary 4D Earth framework for understanding mantle upwellings.