# Electrical Conductivity Evidence for the Existence of a Mantle Plume Benath Tarim Basin
## 4 Discussion
### Evidence of the Mantle Plume Beneath Tarin  
At present, a few people have noticed the low velocity anomaly beneath the Tarin Basin. [PERSON] pointed out that this may indicate the existence of a mantle plume. One-dimensional conductivity inversion results show that there are obvious high conductivity anomalies in the upper mantle transition zone and the upper lower mantle in Tarim area. Compared with the results of previous seismic profiles (Figure 13), the author believes that the high conductivity anomaly beneath the Tarim Basin is reliable, and the high conductivity and low wave velocity indicate the existence of a temperature anomaly. The increase in electrical conductivity in the mantle is usually explained by an increase in the water content and/or an increase in temperature. The minerals in the mantle transition zone have a high water content, which can reach 2.0 wt% [45]. Since the significant increase in the water content in the transition zone is usually related to the dehydration of the detained plate, and there is no clear plate detention in the Tarim transition zone, it is necessary to explain the high conductivity anomaly in the mantle transition zone through the increase in temperature. In order to discuss the temperature characteristics of  
Figure 12: Inversion results of data containing different levels of noise. (**a**) The P-P diagram of the inversion results of the conductivity of the five layers at three noise levels, in which the circle, square, triangle, and cross correspond to \(\sigma_{1}\), \(\sigma_{2}\), \(\sigma_{3}\), \(\sigma_{4}\), \(\sigma_{5}\) in turn; (**b**) The final inversion model; the dashed lines corresponding to different colors are the reliability intervals. the transition zone in the Tarim Basin, this paper uses [PERSON] et al. 's high temperature and high pressure conductivity model  
\[\sigma=\sigma_{\text{OH}}\exp\left(-\frac{H_{\text{H}}}{\mathcal{R}T_{tr}}\right) +\sigma_{\text{OP}}\exp C_{w}\left(-\frac{H_{\text{P}}^{0}-\alpha C_{w}^{1/3}}{ \mathcal{R}T_{tr}}\right), \tag{12}\]  
for the petrophysical calculation of the transition zone [43][PERSON] The conductivity profiles of 150 K, 300 K, and 650 K above the global average temperature of the mantle transition zone are obtained; \(\sigma\) is the volume conductivity, \(C_{w}\) is the water content, \(\alpha\) is the geometric factor, \(\mathcal{R}\) is the Boltzmann constant, \(\mathcal{R}\) = 1.38 \(\times\) 10\({}^{-23}\) J/K, \(T_{\text{tr}}\) is the thermodynamic temperature; \(\sigma_{\text{OH}}\), \(\sigma_{\text{OP}}\) are the pre exponential factors, \(H\) is the activation enthalpy; the subscripts H and P are the electron jump conduction and proton conduction, respectively. The specific model parameters are shown in Table 2.  
The water content in the lower mantle is extremely low, not exceeding 20 ppm [46], and there are currently very few experiments on the conductivity mechanism of the water-bearing rocks there. Therefore, when explaining the causes of high conductivity anomalies in the lower mantle beneath the Tarim area, only the temperature factor is considered. In this paper, we use Formula (13) from [PERSON] et al. [47] for petrophysical calculations for the upper layer of the lower mantle:  
\[\sigma=\sigma_{0}\exp\left(-\frac{E_{\text{a}}+P\Delta V}{\mathcal{R}T}\right), \tag{13}\] \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Mineral** & \(\sigma_{\text{OH}}\)**(S/m)** & \(H_{\text{H}}\)**(eV)** & \(\sigma_{\text{OP}}\)**(S/m)** & \(H_{\text{P}}\)\({}^{0}\)**(eV)** & \(\alpha\) \\ \hline Wadsleyite & 399(311) & 149(10) & 7.74(4.08) & 0.68(3) & 0.02(2) \\ Ringwoodite & 838(442) & 1.36(5) & 27.7(9.6) & 1.12(3) & 0.67(3) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The parameter values used in the petrophysical model in Formula (18). Figure 13: Vertical cross-sections of P wave velocity perturbations along the profiles shown in Figure 1 [2]. The surface along the profile is shown at the top of the cross section.