MATE: an analysis tool for the interpretation of magnetotelluric models of the mantle

Interpretation of electrical conductivity anomalies observed in magnetotelluric models provides an important opportunity to understand the nature of the lithospheric mantle and its dynamics. Over the course of the last two decades, a great number of experimental petrology studies have been carried out which can be utilized to construct electrical conductivity distribution models for a given composition and geotherm. We have developed an open-source software (MATE, Mantle Analysis Tool for Electromagnetics) with an easy-to-use graphical interface that creates such theoretical models. The program is developed in such a way that additional effects and models can be added very easily. To investigate the conductivity distribution of the cratonic mantle, a series of experiments was made. Results indicate that it is of utmost importance to analyze the magnetotelluric models using accurate compositions, water distributions, and geometric models. Hence, using only olivine conductivity models can lead to erroneous interpretations of both conductivity and estimated water content. Analysis of the potential causes for conductive anomalies shows that the upper and lower lithospheric mantle can be interpreted separately with the transition between them at 75–125 km. Conductive anomalies in the upper lithospheric mantle (<1,000 Ωm) are likely to be explained by the existence of well-connected minor phases associated with metasomatic fluids, whereas in the lower lithospheric mantle, hydration and/or well-connected minor phases (e.g., phlogopite or amphibole) can explain conductive anomalies.