Transient electromagnetic response of the Teutonic Bore orebody

Abstract

Transient electromagnetic (TEM) measurements have been made with SIROTEM on four separate surveys over the Teutonic Bore orebody (Western Australia), both before mining operations began and subsequently during different stages of stripping overburden from the mineral deposit. In the late stage of the transient decay the target response was relatively free of the overburden and host‐rock response. Beyond ∼ 6 ms, the maximum anomalous response was a factor of 8 to 10 greater than the combined overburden and host‐rock response. Analog modeling with a copper plate in free space shows that the TEM response of the target consists of a single peak at early delay times, while at delay times beyond ∼ 4.2 ms, the response becomes a double‐peak anomaly with a low directly over the top of the plate. Mathematical modeling of the TEM response with a free‐space infinitely thin plate produces profile characteristics similar to those obtained by analog modeling beyond a delay time of ∼ 4.2 ms. Inversion of premining survey profiles in the delay time range 7.0 to 13.2 ms gives values of 82 m for target depth d, and 86 degrees for dip angle θ. These agree well with the values d = 86 m and θ = 82 degrees derived from drilling data. A target conductance value in the range 250 to 320 S is obtained from the TEM data, indicating that the massive sulfide target is highly conductive. Responses calculated for surveys made during overburden stripping are lower than corresponding field values at early delay times because of the absence of overburden response in the model measurements. At delay times beyond 8.5 ms, the model values are consistent with the field values. These results indicate that for a case similar to the Teutonic Bore orebody, where the maximum anomalous late‐time response is a factor of 8 to 10 times greater than the background response, important target parameters may be derived from free‐space models.

Bacterial communities associated with a mineral weathering profile at a sulphidic mine tailings dump in arid Western Australia

“…Full descriptions of the geology, mineralogy, weathering profile, gossan and other geochemical properties of the deposit are provided by Grieg (), Nickel (), Hallberg & Thompson (), Vaasjoki (), Buselli et al . () and Brown et al . ().…”

“…The fresh disseminated mineralisation is sphalerite (Zn-Fe-S), pyrite (Fe-S), chalcopyrite (Cu-Fe-S) and galena (Pb-S). Full descriptions of the geology, mineralogy, weathering profile, gossan and other geochemical properties of the deposit are provided by Grieg (1984), Nickel (1984), Hallberg & Thompson (1985), Vaasjoki (1985), Buselli et al (1986) and Brown et al (2002). The deposit was open-cut mined to a depth of about 140 m and then mined underground; commercial operation ceased in mid 1984.…”

Interpretation of time domain electromagnetic soundings near geological contacts

“…In some cases, however, a strong cortductor can _verwhelm the surface variation. An example of this type in given _n Figure 1.3, which shows a series of coincident-loop time profiles over the "Feutonic massive sulfide ore body m Western Australia (Buselli et 'al. 1986 properties of the ore body without severe distortion (presumably) from tile surface feature.…”

Small fixed‐loop transient electromagnetic in tunnel forward geological prediction

“…TEM is a geophysical method which can be used for detecting underground bodies by emitting a step‐pulse electromagnetic field and analysing the electromagnetic field produced by target induction. Various studies and fields have report the utilization of TEM, especially for mining and hydrogeological exploration (Buselli, Mccracken and Thorburn ; Danielsen et al . ; Mitsuhata et al .…”