# Electrical Conductivity Evidence for the Existence of a Mantle Plume Benath Tarim Basin
## 1 Introduction  
The Tarim Basin is located in the western part of China. Since 50-60 Ma, the India/Asia collision has resulted in strong uplift, shortening, and strike slip deformation around the Tarim Basin, resulting in the formation of a complex ringed mountain system [1]. The movement of the deep mantle is one of the important factors affecting the activity of the top crust. In a large number of seismic profiles, it is found that there is a large-scale transverse low velocity anomaly beneath the Tarim Basin [2, 3]. [PERSON] pointed out that this may indicate the existence of a mantle plume [4]. A mantle plume, first proposed by [PERSON] [5, 6], is a columnar body produced in the thermal boundary layer of the mantle, driven by buoyancy anomalies and upwelling of deep mantle material [7, 8]. [PERSON] believes that the mantle plume originated from the core-mantle boundary at 2900 km or the seismic discontinuity at about 660 km [9]. The diameter of the mantle plume can be up to hundreds of kilometers, and it has an abnormally high temperature. This localized high temperature anomaly can cause a dramatic increase in electrical conductivity in the transition zone and the lower mantle. Therefore, this renders us an opportunity to use the geomagnetic depth sounding (GDS) method to explore the possible existence of the mantle plume by studying the conductivity model of the mantle transition zone beneath Northwest China [10]. The electrical conductivity of the deep part of the earth, especially in the range of 410-1600 km, can be effectively reflected by the variation with periods of the C-response of GDS [11]. This parameter is estimated from the horizontal and vertical magnetic field data recorded by geomagnetic stations [12, 13]. The intensity of the induced magnetic field is affected by the conductive convective fluid in the core and the mantle, crust,ionosphere, magnetosphere, and ocean current systems and changes over time [14,15]. Therefore, by investigating the changes in the intensity of the surface magnetic field, the internal conductivity of the earth at different depths can be obtained, from which the physical and chemical characteristics and the dynamic mechanisms in Earth's interior can be resolved [16,17]. Inversion is the key to convert C-responses to electrical conductivity profiles. For instance, [PERSON] et al. used stochastic optimization and model exploration techniques to perform one-dimensional inversion of geomagnetic depth sounding, and combined with experimental data of temperature, pressure, and the water content, they obtained temperature information of the mantle transition zone in Europe and Africa [18]. [PERSON] et al. carried out a one-dimensional inversion of the smooth model based on the geomagnetic data obtained by the global smoothing constraint technique and obtained the water content distribution of the mantle transition zone in eastern China [19]. These one-dimensional inversion results perfectly show the conductivity characteristics of the deep part of the earth, and can provide estimations of temperature and the water content in transition zones. However, these study areas are far from Tarim area. The global GDS inversion may reflect the conductivity characteristics beneath Tarim area, for example, using the three-dimensional nonlinear conjugate gradient method, the first electrical conductivity image of mantle transition zone was obtained by [PERSON] et al. [20], but they focused the high conductivity structure of the mantle beneath NE China, while [PERSON] et al. paid more attention to the electrical conductivity in the transition zone beneath Europe and Africa by using the limited memory quasi-Newton method [21,22]. Nonetheless, due to the sparse data set used, the resolution of the electrical structure beneath Tarim area is very low. In this paper, we try to invert the GDS response in Tarim area by the non-heuristic algorithm of simulated annealing (SA) to provide a new reference for studying the deep electrical conductivity structure beneath the Tarim area.