Crustal magma plumbing system beneath the Quaternary volcanic area (northern Hainan Island, China) revealed by magnetotelluric data

Abstract Magma plumbing system in active volcano can transport and store magmas, which is a key element for hazard assessment. The Quaternary volcano cluster of northern Hainan Island, an active volcano area in China, has been associated to a mantle plume. However, certain details such as the pathway of the ascent of magma and its storage in the crust remain unclear. In this work, a 68 km long magnetotelluric profile was deployed including 33 broadband sounding sites across the volcanoes to study the crustal magma plumbing system. Data were inverted using a three-dimensional scheme to image the resistivity structure beneath profile. The resistivity model shows a well-developed shallow low-resistivity zone in the west of Changliu-Xiangou Fault corresponding to the Fushan depression, two high conductors in the depths of ~5–12 km, and a relatively low resistivity layer in the lower crust and uppermost mantle. The conductors in the middle-upper crust were preferably attributed to the accumulation of fluids transported via conduits, while the deeper conductive layer could be ascribed to the presence of crystal mushes. The obtained resistivity structure supports that the crustal magma system of northern Hainan Island is in a state of stability at present, whereas the secular monitoring is still necessary.