# Electrical Conductivity Evidence for the Existence of a Mantle Plume Benath Tarim Basin
## 4 Discussion
### Evidence of the Mantle Plume Beneath Tarin
White dots show the earthquakes that occurred within a 50-km radius from each profile. The velocity perturbation scale is shown at the bottom. The dashed black lines denote the 410 km and 660 km discontinuities. The red dots are a projection along latitude. where \(\sigma\) is the lower conductivity, \(\sigma_{0}\) is the pre-referential factor, \(\sigma_{0}\) = 74 S/m; \(E_{a}\) and \(\Delta V\) are the activation energy and activation volume, respectively, where \(E_{a}\) = 0.7 eV, \(\Delta V\) = \(-\)0.55 \(\pm\) 0.01 cm\({}^{3}\)/mol. The values of temperature T and pressure P at different depths in the lower mantle can be found in [48]. According to Formula (12), the conductivity of the lower mantle is calculated at normal temperature, +150 K, +300 K, and +650 K, as shown in Figure 14. At the 660 km interface at the top of the lower mantle, the global average temperature is about 1925 K [43], and the electrical conductivity under the four stations around the Tarm area corresponds to the electrical conductivity after the temperature rises by 150-450 K. This shows that the temperature at the top of the lower mantle in the Tarm area has increased by at least 150 K.  
It is shown in Figure 1 that the geomagnetic stations we use are distributed near the seismic profile. Figure 13 is the vertical section of the primary wave velocity disturbance corresponding to the profile. The seismic profile is from [PERSON]'s article. It can be seen that there is an obvious low velocity anomaly at 410 km below the Tarm Basin; there is a high conductivity anomaly at 410-520 km in the one-dimensional conductivity profile of WUS station, which almost coincides with the seismic profile; and there is a good corresponding relationship between the two. We speculate that the temperature of WUS station is higher than the global average of 300 K. The WEQ/HOQ station is far from the high temperature anomaly body accumulated at the interface of 410 km, which makes the temperature increase by only 150 K. The location of the 660 km interface penetrated by the rising hot matter may be close to the WMQ station, which is the reason why the conductivity and temperature of WMQ are higher than those at the other three stations in the range of 520-660 km. The four stations have high conductivity anomalies at the top of the lower mantle. Combined with the banded low velocity anomaly at the top of the lower mantle in Figure 13, it is speculated that due to the influence of the greater resistance of the 660 km interface, the thermal material will accumulate at the top of the lower mantle and will have a larger area, and even the thermal material will appear below the HOQ and WEQ stations. According to the high conductivity of the upper part of the lower mantle obtained by our one-dimensional geomagnetic depth inversion, combined with the low velocity anomaly obtained by previous seismic methods, it is inferred that there is a high temperature upwelling beneath the Tarm Basin, which is hindered by the 660 km interface and accumulates at the top of the lower mantle, and upwelling occ  
Figure 14: Conductivity at 660–900 km. The global average conductivity profile is from [11]. Four orange dashed lines represent the conductivity corresponding to increasing temperatures. near WMQ and then accumulates at the 410 km interface. Moreover, the accumulation of hot material at 410 km can also be seen under Hainan volcano [3]. Therefore, the inversion results can be used as electrical evidence to speculate that there may be mantle plumes beneath the Tarim Basin.