Electrical conductivity of metasomatized lithology in subcontinental lithosphere

Abstract A plausible origin of the seismically observed mid-lithospheric discontinuity (MLD) in subcontinental lithosphere is mantle metasomatism. The metasomatized likely to stabilize hydrous phases such as amphiboles. existing electrical conductivity data on amphiboles vary significantly. hornblendite much higher than that tremolite. Thus, if truly represents amphibole varieties MLD regions, then it will cause high anomalies at depths. However, this inconsistent with magnetotelluric observations across Hence, better understand discrepancy and evaluate whether could be caused by metasomatism, we determined a natural rock sample. sample consists ~87% diopside pyroxene, ~9% sodium-bearing tremolite amphibole, ~3% albite feldspar. We collected ~3.0 GPa, i.e., depth relevant MLD. also spanned temperature range between 400 1000 K. found increases temperature. dependence exhibits two distinct regimes. At low temperatures <700 K, dominated conduction solid state. >775 increases, aqueous fluids due partial dehydration. main distinction current study prior studies or amphibole-bearing rocks sodium (Na) content assemblage. Moreover, Na leads conductivity. Pargasite edenite are most common mantle, our Na-bearing closest analog these Comparison results constrains abundance depths <1.5%. Such low-modal proportion only reduce seismic shear wave velocity 0.4–0.5%, which significantly lower reduction 2–6%. might challenging explain both simultaneously.