Analysis of magnetotelluric (MT) data in the northern Appalachian region reveals various heterogeneities in lithospheric structure. By inverting a subset of the long-period Earthscope USArray MT data, we obtained a 3D electrical resistivity model that provides insights into the previously identified seismic low-velocity Northern Appalachian Anomaly (NAA). We compared the resistivity (inverse of conductivity) values with empirical conductivity models based on an olivine-orthopyroxene-clinopyroxene mantle mineral assemblage. Low-resistivity anomalies in the inverted model suggest an anomalously hot mantle in the northern and western edges of the NAA. Both in the north and west, resistivities in the uppermost mantle are sufficiently low to require a small fraction of partial melt. Additionally, we resolved a resistive feature in western New England that extends deep into the mantle lithosphere and is absent in seismic velocity models. We interpret this feature as dry and depleted lithospheric mantle. The observed heterogeneities in the lithosphere may reflect ongoing asthenospheric upwelling caused by combined effects of weakened lithosphere from past hotspot interactions and present edge-driven mantle convection.

Airborne geophysics is widely used in mineral exploration because it provides rapid collection of multiple types of geophysical data over large areas. The availability of multiphysics data is potentially useful because it can lead to a common earth model consistent with all available data and prior information. However, quantitative integration of regional-scale multiphysics airborne geophysical data is rarely reported in literature. We focused on an under-explored region of British Columbia between Williams Lake and Mackenize, namely, the QUEST Project area, where airborne gravity and magnetic data were available. We used a workflow consisting of two key components: joint inversion and geology differentiation. Joint inversion allows us to construct structurally similar physical property models. Geology differentiation classifies the jointly inverted physical property values into distinct classes and builds a 3D quasi-geology model that shows the spatial distribution of different geological units. Prior geological information from various sources is also used when performing geology differentiation. We applied the workflow to the airborne gravity and magnetic data from the Quesnel terrane in central British Columbia. We have successfully identified 9 different geological units. Our results allowed for a more detailed classification of the geology beneath a thick overburden of glacial sediments and we have also identified potential targets for future detailed surveys that are spatially correlated to known mineral deposits (Mount Milligan, Lorraine, Takla-Rainbow, and Kwanika deposits). Our work provides guidance for follow-up detailed surveys in the Quesnel terrane and highlights the benefits of integrated interpretation of multiphysics geoscientific data.