Rock-Melt Interactions in Mantle Xenoliths from Two Intraplate Settings (Tariat, Mongolia and Kilbourne Hole, New Mexico)

Interactions between Earth’s lithospheric mantle and migrating melts contribute to mantle heterogeneity. Mantle xenoliths from Tariat, Mongolia, and Kilbourne Hole, New Mexico, record distinct melt-rock interactions. Tariat xenoliths (equilibrated at 930 – 950 ◦C) contain a pyroxenite vein formed by prolonged equilibration with Si-rich melts. Kilbourne Hole xenoliths (1050 – 1150 ◦C) show evidence of brief basaltic melt interactions. Mineral chemical profiles near melt interfaces exhibit elevated Mg in or- thopyroxene (Mg# > 90), Ti depletion in clinopyroxene, and elevated Cr in spinel (Cr# > 23), indicating localized melt depletion. Diffusion modeling and geospeedom- etry constrain melt-rock interaction timescales, spanning decades at Kilbourne Hole and thousands of years at Tariat.