Fe3+-rich augite and high electrical conductivity in the deep lithosphere

CaSiO3 Perovskite May Cause Electrical Conductivity Jump in the Topmost Lower Mantle

“…For conduction in the low-T regime of CaSiO 3 perovskite, the activation energy is 95-100 kJ/mol. This value is identical to that of proton conduction reported for OH-bearing nominally anhydrous silicate minerals, e.g., olivine, pyroxenes, wadsleyite, and ringwoodite (e.g., Huang et al, 2005 ;Wang et al, 2006 ;Yang, 2012 ;Yang & McCammon, 2012 ;Yoshino, Manthilake, et al, 2008). We thus suggest that the low-T regime of our samples is dominated by proton conduction due to small amounts of OH groups incorporated during the annealing stage as mentioned above.…”

“…Laboratory electrical conductivity measurements of mantle minerals provide useful information about the physical and chemical properties of the Earth's interior by comparing geophysically observed data with experimentally obtained conductivities of minerals. This topic has drawn increasing attention in the past decade as demonstrated by extensive studies on the electrical behavior of mantle minerals such as olivine, pyroxenes, wadsleyite, ringwoodite, bridgmanite, majoritic garnet, and ferropericlase, and the results have fruitfully improved our knowledge about the structure and geodynamics of the deep Earth (Huang et al, 2005;Katsura et al, 1998;Wang et al, 2006;Xu, McCammon, et al, 1998;Yang, 2012;Yang & McCammon, 2012;Yoshino, Manthilake, et al, 2008;Yoshino, Nishi, et al, 2008;Yoshino et al, 2011Yoshino et al, , 2016. Magnetotelluric depth soundings have detected an electrical conductivity jump by 1.5-2 orders of magnitude from~600 to 800 km depth, corresponding roughly to the topmost lower mantle (e.g., Civet et al, 2015, Constable & Constable, 2004Olsen, 1999).…”

Electrical conductors in Archean mantle—Result of plume interaction?

“…Other evidence for charge carrier transport comes from the 827±6Ma Gairdner Dyke Swarm, cross‐cutting the Gawler Range Volcanics, which displays sub‐ophitic augites [ Wingate et al , ] enriched in iron (5%–12% total FeO). Lab measurements on single‐crystal augites show a 1–3 magnitude increase in electrical conductivity compared to dry olivine, further enhanced through common inclusion of <200 to 1800 ppm H 2 O [ Yang and McCammon , ].…”

The link between electrical conductivity anomalies and rheological boundaries

“…New results from the Gawler Craton see a similar feature underlying the surface expressions of the Gawler Range Volcanics and the Hiltaba Suite (Thiel and Heinson, 2013). Hydrogen in the crustal lattice of olivine is held accountable for reducing the resistivity in this case, but iron in the Hiltaba related mineralisation and augites in the Gairdner Dyke Swarm suggests that there may be a contribution to conductivity enhancement from iron as well (Yang et al, 2012).…”