Response characteristics and detectability of pegmatitic rare-metal deposits using different grounded-wire configurations

Abstract

The differential electrical dipole (DED) and differentially normalized electromagnetic method (DNME) have a stronger transverse magnetic field than the horizontal electric dipole (HED) and, thus, have been successfully used for resource exploration in conductive ocean environments. However, which of these two is more suitable for the exploration of resistive targets on land, such as pegmatite veins and ore-related mafic and ultramafic intrusions in mineral deposits, remains unknown. Thus, we conduct a comparative study of the DED, DNME, and HED based on forward modeling and application to a field survey. The signal amplitude of the horizontal electric field measured using the DED and DNME is substantially weaker than that obtained via the HED with the same source length and transmitting current. The lateral variation in the horizontal electric field response observed via the DNME reflects the change in the shallow electrical structure, indicating the spatial distribution of pegmatite veins, as verified by the 3D simulation results and data obtained in a field survey of pegmatitic rare-metal deposits in Lushi County, China. The DED and DNME exhibit similar abilities for detecting resistive targets. Both methods show higher detectability than HED based on 3D synthetic modeling. Our results indicate that the DNME, with its higher responses and better lateral resolution, is a better choice in field surveys on land than the DED.