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The analytical conditions including surface state, moisture effect, and device condition were investigated for
applying Short Wave Infrared (SWIR) spectroscopy to the field survey. Among the three surface state of samples (exposed surface, cutting face and powder), both spectra from the exposed surface and cutting face are almost identical whereas...
Citations
... Since VNIR-SWIR spectroscopy uses an analytical method for measuring the amount of reflected electromagnetic waves on a sample, reflectance changes in wavelength can be expected by the scattering phenomenon depending on the surface condition of the mineral. Kim et al. (2017) demonstrated that the natural and cutting surface have almost similar reflectance, and powder samples have the highest reflectance among them. In the powder condition, the reflectance was increased with decreasing grain sizes from 500 to 45 μm reviewed by Zaini et al. (2012). ...
... The minimum scan speed in SR-6500 is 100 milliseconds. Dark samples require longer acquisitions to discriminate low reflectance from background noise (Kim et al., 2017). ...
Mineral exploration focused on deeply concealed targets at depth requires effective techniques applicable in the field in order to identify ore-forming systems on a large scale and pathfinders to locate ore on a smaller scale. According to the rapid development of portable equipment in recent years, the importance of near real-time analysis in the field has been increasing by helping fast decision-making support before laboratory requests.Spectroscopic analysis using individual equipment has been widely used in the exploration of mineral resources, but it is rare to apply integrated data from several techniques to characterize “vectors”, which provide variations in lithology, geochemistry, mineralogy, and mineral chemistry. In addition, it is even rarer if the combination of spectral data is obtained from various portable instruments. Therefore, this study aims at reconciling geochemical data acquired from portable spectroscopic devices in order to determine the best geochemical information from each technique applied by combining the mineralogical and elemental information. Elemental and mineralogical data are provided in this study by six portable techniques: (i) elemental analyses such as XRF and LIBS for major, trace, and light elements, and (ii) mineralogical analyses such as Raman, VNIR-SWIR, MIR, and XRD to constrain rock-forming, ore, and alteration minerals. The final objective of this study is to identify vectors to the ore by applying the reconciled multi-spectral data obtained from the “real” sample in the Elvira volcanogenic massive sulfide (VMS) deposit. To achieve this, step-by-step procedures were carried out: (i) methodological understanding of each technique, (ii) establishment of a spectral database consisting of naturally monomineralic minerals, (iii) design of a decision tree to classify by mineral or mineral classes based on diagnostic bands, and mineral identification and quantification of (iv) carbonate and (v) phyllosilicate minerals (i.e., trioctahedral chlorites and dioctahedral micas), which are indicators of the target deposit.Several limitations of portable spectroscopy were confirmed based on the device itself and the geological environment in the Elvira deposit. Nevertheless, portable spectroscopy is effective in identifying the presence and compositional changes of various minerals from heterogeneous rock samples. Therefore, spectroscopic analysis on-site can be one of the vectoring tools to determine the implication for ore mineralization in hidden ore explorations.
