TDEM Survey at Shea Creek Uranium Deposit Utilising a Low-Temperature Superconductor SQUID

Smit, Jaco; Roux, T. Le

doi:10.3997/2214-4609-pdb.241.smit_paper1

Cited by 4 publications

(1 citation statement)

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“…However, they are often not disclosed or published by the clients. A number of them could be found in LeRoux and Macnae (2007), Terblanche (2008), Smit and LeRoux (2009), Webb and Corscadden (2009), Selfe (2009), Woods (2010), Rochlitz et al (2018), etc.…”

Section: State Of the Artmentioning

confidence: 99%

SQUIDs for magnetic and electromagnetic methods in mineral exploration

et al. 2022

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Research on quantum sensors for the detection of magnetic fields (quantum magnetometers) is one of the fast-moving areas of Quantum Technologies. Since there exist expectations about their use in geophysics, this work will provide a brief overview on the various developing quantum technologies and their individual state of the art for implementing quantum magnetometers. As one example, the developments on superconducting quantum interference devices, so-called SQUIDs as a specific implementation of a quantum magnetometer, are presented. In the course of this, SQUID instrument implementations and associated demonstrations and case studies will be presented. An airborne vector magnetometer with ultra-low noise ($$<10 \mathrm{fT}/\sqrt{\mathrm{Hz}}$$ < 10 fT / Hz ) and high dynamic range of $$>32 \mathrm{bit}$$ > 32 bit will be introduced which has the prospect to be applied for the magnetic method in parallel with electromagnetic methods such as passive audio-frequency magnetics or semi-airborne methods using active transmitters such as elongated grounded dipole sources. The according signals are separated in the frequency domain. A second implementation is an airborne full tensor gradiometer instrument will be discussed which has shown already a number of successful case studies and which turned into commercial operation in the past years. Besides the airborne instrument, a very successful implementation of quantum magnetometers is the SQUID-based receiver for the ground-based transient electromagnetic method. Today it is a mature technology which has been in commercial use for more than a decade and has led to a number of discoveries of conductive ore bodies. One case study will be presented which demonstrates the performance of this instrument. Finally, future prospects of using quantum magnetometers, including SQUIDs and new optically pumped magnetometers, in geophysical exploration will be discussed. Particular applications for both sensor types will be introduced.

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Section: State Of the Artmentioning

confidence: 99%

SQUIDs for magnetic and electromagnetic methods in mineral exploration

et al. 2022

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Capability of low-temperature SQUID for transient electromagnetics under anthropogenic noise conditions

et al. 2018

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Transient electromagnetics (TEM) is a well-established method for mineral, groundwater, and geothermal exploration. Superconducting quantum interference device (SQUID)-based magnetic-field receivers used for TEM have quantitative advantages and higher sensitivity compared with commonly used induction coils. Special applications are deep soundings with target depths [Formula: see text] and settings with conductive overburden. However, SQUIDs have rarely been applied for TEM measurements in environments with significant anthropogenic noise. We compared a low-temperature SQUID with a commercially available induction coil in an area affected by anthropogenic noise. We acquired four fixed-loop data sets with totally 61 receiver stations close to Bad Frankenhausen, Germany. The high sensitivity of the SQUID enables low noise levels, which lead to longer high-quality transient data compared with the induction coil. The effect of anthropogenic and natural noise sources is more critical for the coil than for the SQUID data. In the vicinity of the transmitter loop, systematic distortion of the coil signals occurs at early times, most probably caused by sferic interferences. We have developed 1D inversion results of both receivers that matched well in general. However, the SQUID-based models were more consistent and showed greater depths of investigation. This led to a superior resolution of deeper layers and even enabled a potential detection of thin conducting targets at up to a 500 m depth. Moreover, we find that the SQUID data inversion revealed multidimensional effects within the conductive overburden. In this regard, we applied forward modeling to analyze systematic differences between inversion results of SQUID and coil data. We determine that low-temperature SQUIDs have the potential to significantly improve the reliability of subsurface models in suburban environments. Nevertheless, we recommend combined application of both types of receivers.

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3D electromagnetic modeling of graphitic faults in the Athabasca Basin using a finite-volume time-domain approach with unstructured grids

Farquharson

Miehé

et al. 2021

GEOPHYSICS

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Uranium exploration in the Athabasca Basin, Canada, relies heavily on ground-based transient electromagnetic (TEM) surveys to target thin, steeply dipping graphitic conductors that are often closely related to the uranium ore deposits. The interpretation of TEM data is important in identifying the locations and trends of conductors in order to guide subsequent drilling campaigns. We present a trial-and-error modeling approach and its application to the interpretation of a data set acquired at Close Lake in the Athabasca Basin. The modeling process has two key tasks: building geo-electric models and computing their TEM responses. The modeling process is repeated with the geo-electric model being iteratively refined based on the match between three-component calculated and measured data from early to late times. To create geo-electric models, we first build a realistic geological model and discretize it using an unstructured tetrahedral mesh, with each mesh cell populated with appropriate resistivities. To calculate the TEM responses of the geo-electric model, we use a 3D finite-volume time-domain (FVTD) algorithm. We construct our initial model based on existing geologic information and drilling data. We show that this modeling process is flexible and can easily handle thin, steeply dipping conductive graphitic fault models with variable resistivities in the fault and background, and with topography. Our interpretation of the Close Lake data matches well with the trend and location of the main conductor as revealed by drilling data, and also confirms the existence of a smaller conductor which only caused noticeable anomalous responses in early-time horizontal-component data. The smaller conductor was suggested by previous electromagnetic data but was missed in a recent interpretation based on the modeling of only late-time vertical component data with plate-based approximate modeling methods.

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TDEM Survey at Shea Creek Uranium Deposit Utilising a Low-Temperature Superconductor SQUID

Cited by 4 publications

References 0 publications

SQUIDs for magnetic and electromagnetic methods in mineral exploration

SQUIDs for magnetic and electromagnetic methods in mineral exploration

Capability of low-temperature SQUID for transient electromagnetics under anthropogenic noise conditions

3D electromagnetic modeling of graphitic faults in the Athabasca Basin using a finite-volume time-domain approach with unstructured grids

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