Brian Minty

Minty Geophysics

In January 2017 the largest airborne magnetic, radiometric and elevation survey in South Australia’s history began in the Gawler Craton. The aim of the South Australian Government is to use the survey as an opportunity to achieve best practice in relation to the coordination, landholder liaison, reporting and quality control of the survey, in tande...

222Rn is a naturally occurring noble gas produced via alpha decay of 226Ra and it is the only gaseous daughter product of the decay chain of 238U, a radioisotope present in the majority of soils and rocks. 222Rn is almost chemically inert, it exhales into the atmosphere and migrates by diffusion and convection: as it runs out mainly through radioac...

In January 2017 the largest airborne magnetic, radiometric and elevation survey in South Australia’s history began in the Gawler Craton. The aim of the South Australian Government is to use the survey as an opportunity to achieve best practice in relation to the coordination, landholder liaison, reporting and quality control of the survey, in tande...

In this paper, we present the results of an $~$5-h airborne gamma-ray survey carried out over the Tyrrhenian Sea in which the height range (77-3066) m has been investigated. Gamma-ray spectroscopy measurements have been performed using the AGRS_16L detector, a module of four 4L NaI(Tl) crystals. The experimental setup was mounted on the Radgyro, a...

Rn is a noble radioactive gas produced along the ²³⁸U decay chain, which is present in the majority of soils and rocks. As ²²²Rn is the most relevant source of natural background radiation, understanding its distribution in the environment is of great concern for investigating the health impacts of low-level radioactivity and for supporting regulat...

We review recent developments in the processing of airborne gamma-ray spectrometric data that facilitate the detection of ever more subtle radioelement anomalies. These have application to the search for strategic minerals, often after the primary geological feature has been identified from airborne magnetics. The recent developments include improv...

We present a new method for the inversion of airborne gamma-ray spectrometric line data to a regular grid of radioelement concentration estimates on the ground. The method incorporates the height of the aircraft, the 3D terrain within the field of view of the spectrometer, the directional sensitivity of rectangular detectors, and a source model com...

Many countries have significant coverage of publicly funded airborne magnetic and gamma-ray spectrometric surveys that are available to explorers as precompetitive information to encourage exploration. However, individual surveys are generally small, and after decades of data acquisition, explorers are faced with the problem of how to effectively c...

Radioelement ratios are useful for mapping subtle variations in radiometric signatures in map data. But the conventional method for calculating radioelement ratios has the significant limitation that if just one of the radioelements comprising the ratio has a small spread of concentration estimates relative to its mean, then it will not contribute...

The Radiometric Map of Australia shows the distribution of potassium (% K), uranium (ppm eU) and thorium (ppm eTh) over Australia. A suite of image enhancement and data integration techniques can be used to enhance the value of these data for both mineral exploration and environmental mapping. Gradient-enhanced ternary and pseudo-colour image enhan...

Geoscience Australia and the Australian State and Territory Geological Surveys have systematically surveyed most of the Australian continent over the past 40 years using airborne gamma-ray spectrometry to map potassium, uranium and thorium elemental concentrations at the Earth's surface. However, the individual surveys that comprise the national ga...

Airborne gamma-ray spectrometry is a passive remote sensing technique that measures the natural emission of gamma-ray radiation from the upper 30cm of the earth's surface. The principle gamma-ray emitting isotopes used in airborne geophysical surveys are 40K, and the 232Th and 238U decay series. These are used to estimate potassium, thorium and ura...

The usefulness of geophysics in hydrogeological studies depends on the existence of a contrast in one or more physical properties that can be measured by appropriately applying a geophysical method. Available properties where measurable contrasts might exist include electrical conductivity, radioactivity, magnetic susceptibility, bulk density, seis...

The effect of emanation radon is shown to be a significant problem for estimating uranium concentration from ground-based gamma-ray spectrometric surveys. Radon gas (a daughter product in the U238 decay series) escapes from rocks and soils near the Earth?s surface into the lower atmosphere. Under early morning, still-air conditions, radon concentra...

In stable cratonised crust, the measured surface heat flow (qs) approximates the sum of the “deep” heat flux due to mantle convection (qm), and the heat flow contribution of predominantly “shallow” crust-hosted radiogenic heat production (qc). Archaean terrains worldwide are characterised by low and relatively uniform qs values (30–50 mW m⁻²), and...

The first part of the paper presents a method for frequency domain deconvolution of airborne gamma‐ray surveys using a Wiener filter. A geometrical detector model is used to model gamma‐ray detection, with aircraft movement simply incorporated by a multiplicative term. The method requires estimation of the autocorrelation functions governing both s...

Guidelines to radioelement mapping using gamma-ray spectrometry data

Three hypotheses are tested for the pre-conditioning of airborne gamma-ray spectra to improve the accuracy of principal component-type (PC) spectral noise-reduction methods. First, I show that the distribution of the input variables (channel count rates) has little effect on the accuracy of the noise-reduction methods. Second, if there are insuffic...

Regional compilations of airborne magnetic data are becoming more common as national databases grow. Grids of the magnetic survey data are joined together to form geological province‐scale or even continental‐scale compilations. The advantage of these compilations is that large tectonic features and geological provinces can be better mapped and int...

The first part of the paper presents a method for frequency domain deconvolution of airborne gamma-ray surveys using a Wiener filter. A geometrical detector model is used to model gamma-ray detection, with aircraft movement simply incorporated by a multiplicative term. The method requires estimation of the autocorrelation functions governing both s...

Statistical methods for removing noise from multichannel spectra are now routinely applied in gamma-ray spectrometry. The two methods in common use are the Noise Adjusted Singular Value Decomposition (NASVD) method and the Maximum Noise Fraction (MNF) method. These methods use a principal component (PC) type analysis to extract the dominant spectra...

Dickson and Taylor (1998) evaluated the NASVD (Noise Adjusted Singular Value Decomposition, Hovgaard, 1997) and MNF (Maximum Noise Fraction, Green et al., 1988; Lee et al., 1990) methods for reducing noise in gamma-ray spectra. They showed (Table 1) that the MNF method is far more effective at reducing noise than the NASVD method. This result is su...

Older airborne gamma-ray spectrometric survey data were often presented in units of counts per second. These data values are dependent on survey and equipment parameters such as detector volume, survey height, and the window energy limits used to measure the gamma radiation. Thus, data values on adjacent surveys may not be directly comparable. This...

A calibration range is an easily navigable strip of land that is used to measure the response of an airborne spectrometer system to changes in aircraft altitude (height attenuation coefficients), and to sources of known concentration (sensitivity coefficients). This paper describes the selection and assessment of an airborne gamma-ray spectrometric...

Adequate background correction is a crucial step in processing airborne gamma-ray spectrometric data because any errors are amplified during subsequent processing procedures. Two multichannel models for the estimation of atmospheric radon background are proposed. The spectral-ratio method uses the relative heights of uranium (U) series photopeaks t...

The conventional approach to the processing of airborne gamma-ray spectrometric data is to first sum the observed spectra over three relatively broad energy windows. These three window count rates are then processed to obtain estimates of the potassium (K), uranium (U), and thorium (Th) elemental abundances. However, multichannel spectra contain ad...

Noise-adjusted singular value decomposition (NASVD) is a spectral component analysis procedure for the removal of noise from gamma-ray spectra. The procedure transforms observed spectra into orthogonal spectral components. The lower-order components represent the signal in the original observed spectra, and the higher-order components represent unc...

The data need to be corrected for dead time, energy drift, and background radiation before being inverted to elemental count rates. The elemental count rates are then corrected for variations in the terrain clearance of the detector and reduced to elemental concentrations in the ground. Statistical errors in the raw data are propagated by the data...

The interpretation of gamma-ray spectrometric data requires an understanding of the underlying physics of the method, and an insight into the data acquisition, system calibration, and data processing and presentation procedures. The shape and intensity of a measured airborne gamma-ray spectrum is a complex function of many variables. Source thickne...

The conventional processing of airborne gamma-ray spectrometric data uses 3 broad energy windows to estimate the ground concentrations of K U and Th. This thesis investigates the potential for using the full gamma-ray spectrum in an attempt to increase the amount of information currently extracted from airborne gamma-ray data. The observed spectrum...

In the last few years, the use of airborne gamma-ray spectrometry for geological mapping and mineral exploration has shown considerable growth. With this growth there has developed an increasing need to standardise the airborne measurements so that they will be independent of survey parameters. This paper describes the various calibration and proce...

A new method for determining the optimum channel combinations for reducing the number of channels of data for multichannel airborne gamma-ray spectrometry is developed. The concept of 'generalised' channels, which are the summation of one or more 12 keV data channels that are not necessarily contiguous in the spectrum is introduced. The method uses...

A simple method has been developed for separating the gamma radiation due to ¹³⁷Cs from that due to natural sources using conventional 4-channel airborne gamma-ray spectrometry. The method uses the fact that whilst the ¹³⁷Cs photopeak falls within the conventional total-count window, it occurs well below the three windows used to monitor naturally...

We have developed a new technique for estimating airborne gamma-ray spectrometric backgrounds. The background comes from three sources, namely aircraft, cosmic and atmospheric (radon) radiation. The aircraft and cosmic components are independently estimated by suitable calibration and the monitoring of a 3-6 MeV "cosmic' channel. Multichannel obser...

A simple technique is described for removing residual levelling errors from aeromagnetic data. These residual errors have a distinct spectral signature and are easily removed from a grid of the data using existing directional grid-filtering methods. The filtered grid is then used to correct the located data. The method can not distinguish between l...

Standard radioactive sources of known element abundances are essential for the calibration of airborne gamma-ray spectrometers. The conventional approach to calibration has been the determination of 3-channel stripping ratios and sensitivity constants from large airport calibration pads, and a well calibrated test strip, respectively. However, cali...

Thesis (M.A.)-Universiteit van Pretoria, 1982.