The calibration of a portable three-channel gamma-ray spectrometer for in situ analysis of thorium, uranium, and potassium is discussed. A method of regression analysis is suggested as the best means of including all of the data available from the calibration stations. Calibration indicates a nonlinear relation between count rates obtained in the field and concentrations in parts per million obtained from laboratory analysis. The range of radioelement content must be taken into consideration and appropriate sets of calibration constants applied. As an example of the method, calibration constants are calculated for a portable gamma-ray spectrometer using data for the Blind River uranium region of Ontario.
The McConnell nickel deposit is an elliptical amphibolite-biotite quartz diorite pod within the Sudbury Metabreccia that surrounds the main mass of the Sudbury Igneous Complex. The geometry of the deposit is tabular with a strike length of approximately 152 m and depth of 610 m. Various magnetic surveys were conducted in this study area. A regional aeromagnetic survey was conducted by the Ontario Geological Survey. A more detailed ground magnetics survey and borehole magnetic survey are used in the interpretation of the character of the causative body. Five boreholes which intersect the deposit at 40 m, 105 m, 135 m, 210 m, and 250 m provide good lithological control of the deposit with depth. Eight other boreholes used in this study did not have logged lithology, but all 13 holes were logged with gamma ray, density, spectral gamma-gamma, IP, resistivity, SP, magnetic susceptibility, temperature, and three-component magnetic field probes. Only the measurements of magnetic susceptibility and three-component magnetic field measurements and their interpretation will be discussed in this paper. Three-component magnetic vector surveys show different signatures for boreholes that pass through a magnetic source body, and for holes that are adjacent to the source body. Using inverse models of the surface magnetic data, values of magnetic susceptibility and magnetic remanence direction and intensity for the various lithological units are estimated. Modelling of the subsurface data reveals fine structure within the ore body and may be used to estimate the direction and distance to the magnetic bodies.
The desired output from a gamma‐ray logging system in mining applications is an accurate log of the quantitative distribution of radioelements with depth along the borehole. However, the measured log is not the desired output, but it may be visualized as the desired output modified by a series of low‐pass filters of various characteristics. These filters can be related to the distance interval over which each count is made (or the analog ratemeter time constant), the detector length, and the “geologic impulse response” (the response of a point detector to an infinitesimally thin layer of ore of a known grade). In effect, this means that the response due to thin beds is lower than expected, and the resolution will be reduced. An understanding of the nature and properties of these filters will aid in the proper evaluation of the log. To optimize the accuracy and resolution of quantitative uranium (or other radioelement) determinations, especially in thin beds and complex sequences, it is necessary to keep the counting interval short, and to compensate for the effect of the geologic impulse response. Although the effect of the geologic impulse response may be removed in any of several ways, the use of a simple inverse convolution operator as described here allows the data to be processed on‐line, essentially in real time, using a microprocessor or portable minicomputer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.