关键词: 瞬变电磁法, 三维正演, 有限体积法, 海底多金属硫化物, 各向异性

Abstract: Seafloor massive sulfide (SMS) deposits have emerged as a promising potential resource to address the growing global demand for precious metals, including copper, silver, and gold. The detection and assessment of these deposits are significantly challenging due to the rugged seafloor topography and complex depositional and mineralization environments. Particularly, the electrical anisotropy resulting from the orientation of mineral grains and veins poses additional challenges in interpreting electromagnetic detection data. To address these challenges, this study employs the mimetic finite-volume method  along with the backward Euler scheme to discretize the time-domain Maxwell equations. By utilizing the direct method solver PARDISO, we are able to solve the linear equation system, thereby facilitating a three-dimensional anisotropic forward simulation of the SMSs model. The primary objective of this research is to investigate the influence of the mound depositional environment on the transient electromagnetic response through forward simulation. Moreover, we conduct a detailed analysis of the effects stemming from the conductivity anisotropy of both  sedimentary surrounding rocks and SMSs, making comparisons among different electrical anisotropy models. The results demonstrate the significance of both the  sedimentary surrounding rocks anisotropy and the SMSs anisotropy in influencing the transient electromagnetic response. Additionally, our analysis reveals that the electrical anisotropy of the SMSs exerts a more pronounced impact on the electric field compared to the anisotropy of sedimentary surrounding rocks. Furthermore, we observe that horizontal anisotropy demonstrates a greater influence on the electric field than vertical anisotropy, as evidenced by the diverse electrical anisotropy models explored in this study.

Key words: transient electromagnetic method, three-dimensional forward modeling, finite-volume method, seafloor massive sulfides, anisotropy