Abstract
X-ray computed tomography (XCT) is becoming one of the most important techniques in the geosciences. The technique relies on linear attenuation coefficient differences in order to reveal the internal structure of the rocks. In this work, we present a new excel macro tool, called MXLAC, which is a data bank with an excel interface that uses density, X-ray energy and the mineral chemical formula to allow users to calculate mineral linear attenuation coefficients that can then be used to determine discrimination between mineral pairs. Elements within a mineral and specified by the chemical formula, determine how the X-ray beam is attenuated. Analysis of a variety of scanned mineral pairs with similar densities and attenuation coefficients indicates that an attenuation coefficient difference of greater than or equal to 6% at 45.5 keV effective X-ray energy is required for effective discrimination between two minerals using XCT with single energy scanning. This means that mineral pairs, such as quartz and pyrophyllite cannot be discriminated using the current XCT instruments due to the fact that the attenuation coefficient difference is less than 1.9% at 45.5 keV effective X-ray energy. Garnets and a variety of other minerals were used as examples to illustrate the importance of knowing the actual chemical formula of the mineral to demonstrate whether they can be partially or fully discriminated from each other.
Highlights
X-ray computed tomography (XCT) is a non-destructive technique that utilizes X-rays to image the 3D internal structure of a wide variety of materials [1,2,3]
The 40 minerals were picked to evaluate different mineral compositional complexity in terms of both the range of elements present in the mineral as well as the mineral structure. It includes minerals regarded as ore minerals, clay minerals, carbonates and end-member varieties of the same mineral
Scans with optimal image contrast. These attenuation coefficients can be utilised to optimise the X-ray scanning energy to discriminate minerals according to exact mineral compositions as well as density for proper quantification
Summary
X-ray computed tomography (XCT) is a non-destructive technique that utilizes X-rays to image the 3D internal structure of a wide variety of materials [1,2,3]. The ability of the technique to determine the mineral content, distribution of minerals, mineral texture, porosity and pore structure network, at a variety of scales, made it an attractive technique across diverse fields from petrology to palaeontology to minerals processing [2,8,9,10,11]. Micro and nano XCT has been used widely to characterize shale gas pore framework [12,13,14]. XCT has proven to be an important analytical technique for the analysis of drill cores, that lend themselves to analysis because of their uniform sample geometry. It has been proposed to combine XCT with grey level
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