Does a Shallow Magma Reservoir Exist in the Wudalianchi Volcanic Field? Constraints From Magnetotelluric Imaging

Abstract

We obtain new images of the 3D resistivity structure of the Wudalianchi volcanic field (WVF). No low-resistivity structure is found beneath Laoheishan and Huoshaoshan volcanoes in the WVF, which challenges the hypothesis of one or more magma reservoirs in the upper crust of this region. We observe a low-resistivity body beneath Weishan volcano; however, estimated magma emplacement rates conflict with the observed volume of that body. Due to the relatively low geothermal gradient and surface heat flow in the area, magma would cool rapidly and could not be sustained for a long time unless new magma was regularly introduced into the system, but our observations do not support this scenario. We suggest that the magma in the WVF mainly originates from the mantle or the base of the crust with little crustal residence, and that the low-resistivity body in the upper crust is likely due to saline aqueous free fluids.