Transient electromagnetic profiles across gold-mineralisation zones in central Victoria

Magnetotelluric survey for undercover structural mapping, Central Victoria

“…The latter of these methods, the use of additional short-period data to resolve the near surface structure, is the scheme which we have implemented here; specifically using data from the overlaying TEM transect (TEM results presented in Dennis et al 2010). The phenomenon of the static offset occurs in situations where there exists a surficial heterogeneity situated in the vicinity of an MT sounding site at depths less than approximately 1.5 skin depths of the highest frequency (Spies 1989).…”

“…Based on a linearised leastsquares fit with smoothness regularisation for 2-D inversions, both algorithms incorporate the finite-element method for forward modelling in the inversion stage, but adopt two different schemes to determine the regularisation parameters, these are: Akaike Basian Information Criteria (Uchida 1993) and Active Constraint balancing (Yi et al 2003;Lee et al 2009). Following the completion of the TEM transect (Dennis et al 2010) and applying statics corrections to the dataset, the original 2-D sections were used as an a priori guide for generating new models. Produced using the WinGLink 1 software package for MT data (distributed by Geosystem SRL) comprehensive details of the inversion routine implemented are available in Rodi & Mackie (2001).…”

“…This preliminary overlap shows that significant correlation exists between areas of high seismic reflectivity and contrasting electrical response to the regional average. Galvanic distortion or static shift of MT data however, is a well documented problem (Sternberg et al 1988;Pellerin & Hohmann 1990;Meju 1996;Simpson & Bahr 2005); thus, after the completion of a coinciding near surface Transient Electromagnetic (TEM) profile (Dennis et al 2010), static shift corrections were applied to the (Bendigo line 2) MT dataset, allowing a more accurate conclusion to be drawn from the resulting section.…”

Transient electromagnetic surveys for the measurement of near-surface electrical anisotropy

“…1 for conceptual geology), including the Heathcote Fault on its western margin and the Mount William Fault defining its eastern lower margin (Edwards et al, 1998). Maintaining their reference numbers from the previous regional TEM survey (Dennis et al, 2010), sites 38 and 39 (site 39 situated within the 4 km wide greenstone belt and site 38 located~3 km further east) were selected following an analysis of the site coincident MT data (Dennis et al, 2011), indicating a near-surface anisotropic response (MT apparent resistivity curves presented by Fig. 3).…”