scholarly journals Quantitative Mineral Mapping of Drill Core Surfaces I: A Method for µXRF Mineral Calculation and Mapping of Hydrothermally Altered, Fine-Grained Sedimentary Rocks from a Carlin-Type Gold Deposit

2020 ◽  
Author(s):  
Rocky D. Barker ◽  
Shaun L.L. Barker ◽  
Siobhan A. Wilson ◽  
Elizabeth D. Stock
Keyword(s):  
Gold Deposit ◽  
Sedimentary Rocks ◽  
Potassium Feldspar ◽  
Ore Deposits ◽  
Drill Core ◽  
Raster Data ◽  
X Ray ◽  
Fine Grained ◽  
Core Samples ◽  
Wavelength Dispersive Spectrometry

Abstract Mineral distributions can be determined in drill core samples from a Carlin-type gold deposit, using micro-X-ray fluorescence (µXRF) raster data. Micro-XRF data were collected using a Bruker Tornado µXRF scanner on split drill core samples (~25 × 8 cm) with data collected at a spatial resolution of ~100 µm. Bruker AMICS software was used to identify mineral species from µXRF raster data, which revealed that many individual sample spots were mineral mixtures due to the fine-grained nature of the samples. In order to estimate the mineral abundances in each pixel, we used a linear programming (LP) approach on quantified µXRF data. Quantification of µXRF spectra was completed using a fundamental parameters (FP) standardless approach. Results of the FP method compared to standardized wavelength dispersive spectrometry (WDS)-XRF of the same samples showed that the FP method for quantification of µXRF spectra was precise (R2 values of 0.98–0.97) although the FP method gave a slight overestimate of Fe and K and an underestimate of Mg abundance. Accuracy of the quantified µXRF chemistry results was further improved by using the WDS-XRF data as a calibration correction before calculating mineralogy using LP. The LP mineral abundance predictions were compared to Rietveld refinement results using X-ray diffraction (XRD) patterns collected from powders of the same drill core samples. The root mean square error (RMSE) for LP-predicted mineralogy compared to quantitative XRD results ranges from 0.91 to 7.15% for quartz, potassium feldspar, pyrite, kaolinite, calcite, dolomite, and illite. The approaches outlined here demonstrates that µXRF maps can be used to determine mineralogy, mineral abundances, and mineralogical textures not visible with the naked eye from fine-grained sedimentary rocks associated with Carlin-type Au deposits. This approach is transferrable to any ore deposit, but particularly useful in sedimentary-hosted ore deposits where ore and gangue minerals are often fine grained and difficult to distinguish in hand specimen.

scholarly journals Drill-Core Mineral Abundance Estimation Using Hyperspectral and High-Resolution Mineralogical Data

2020 ◽  
Vol 12 (7) ◽  
pp. 1218
Author(s):  
Laura Tuşa ◽  
Mahdi Khodadadzadeh ◽  
Cecilia Contreras ◽  
Kasra Rafiezadeh Shahi ◽  
Margret Fuchs ◽  
...  
Keyword(s):  
Machine Learning ◽  
High Resolution ◽  
Ore Deposits ◽  
Machine Learning Algorithms ◽  
Training Data ◽  
Support Vector ◽  
Drill Core ◽  
Data Types ◽  
Mineralogical Characterization ◽  
Core Samples

Due to the extensive drilling performed every year in exploration campaigns for the discovery and evaluation of ore deposits, drill-core mapping is becoming an essential step. While valuable mineralogical information is extracted during core logging by on-site geologists, the process is time consuming and dependent on the observer and individual background. Hyperspectral short-wave infrared (SWIR) data is used in the mining industry as a tool to complement traditional logging techniques and to provide a rapid and non-invasive analytical method for mineralogical characterization. Additionally, Scanning Electron Microscopy-based image analyses using a Mineral Liberation Analyser (SEM-MLA) provide exhaustive high-resolution mineralogical maps, but can only be performed on small areas of the drill-cores. We propose to use machine learning algorithms to combine the two data types and upscale the quantitative SEM-MLA mineralogical data to drill-core scale. This way, quasi-quantitative maps over entire drill-core samples are obtained. Our upscaling approach increases result transparency and reproducibility by employing physical-based data acquisition (hyperspectral imaging) combined with mathematical models (machine learning). The procedure is tested on 5 drill-core samples with varying training data using random forests, support vector machines and neural network regression models. The obtained mineral abundance maps are further used for the extraction of mineralogical parameters such as mineral association.

scholarly journals The Pb-Zn (Ba) Nonsulfide Mineralizations at Bou Caïd (Ouarsenis, Algeria): Mineralogy, Isotope Geochemistry, and Genetic Inferences

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 687
Author(s):  
Hassina Louha ◽  
Giuseppina Balassone ◽  
Abdelhak Boutaleb ◽  
Maria Boni ◽  
Michael M. Joachimski ◽  
...  
Keyword(s):  
Energy Dispersive Spectrometry ◽  
Isotope Geochemistry ◽  
Sedimentary Rocks ◽  
Ore Deposits ◽  
X Ray Diffraction ◽  
X Ray ◽  
Metal Carbonates ◽  
Carbon And Oxygen Isotope ◽  
Geochemical Analyses ◽  
Isotope Analyses

The ore deposits of Bou Caïd (Ouarsenis, Algeria) occur in Jurassic and Cretaceous sedimentary rocks. The barite and Pb-Zn (Fe, Cu, and F) ore deposits of Bou Caïd belong to vein- and karst-type. The mineralization is represented in the whole area by a mixture of barite (currently still exploited) and nonsulfides consisting of hemimorphite, smithsonite, cerussite, hydrozincite, and Fe-oxy-hydroxides, with remnants of galena and sphalerite in variable proportions. Mineralogical and geochemical analyses were carried out on the Bou Caïd nonsulfides. Several samples representing nonsulfide mineralization (Grand Pic and at Srâa Abdelkader) were subjected to a multidisciplinary analytical approach, using optical microscopy (OM), powder X-ray diffraction (PXRD), Scanning Electron Microscopy with Energy Dispersive Spectrometry (SEM-EDS). Nonsulfide mineralization consists of a mixture of hemimorphite, hydrozincite, smithsonite, cerussite, and Fe-oxy-hydroxides, often with zebra-like textures. In the proposed paragenetic scheme, covellite and chalcocite are followed by cerussite, jarosite, smithsonite, and hydrozincite. Then, hemimorphite crystallizes, accompanied by mimetite, traces of malachite and clay minerals (also Zn-bearing), precipitate. Fe-(Mn)-oxy-hydroxides can form during various phases of the supergene stage. Small amounts of late barite can be related to partial remobilization and occur as reprecipitation products. Stable isotope analyses were performed on the calcites and metal carbonates of the supergene ores. Carbon and oxygen isotope values of smithsonite and hydrozincite were comparable to published supergene Zn carbonate data. The isotope values of the Bou Caïd calcites fell both into the hydrothermal carbonate and in the supergene fields.

scholarly journals The Albitization of K-Feldspar in Organic- and Silt-Rich Fine-Grained Rocks of the Lower Cambrian Qiongzhusi Formation in the Southwestern Upper Yangtze Region, China

Minerals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 620 ◽  
Author(s):  
Min ◽  
Zhang ◽  
Li ◽  
Zhao ◽  
Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Lower Cambrian ◽  
Mineral Assemblage ◽  
Sedimentary Rocks ◽  
Pore Filling ◽  
X Ray ◽  
Fine Grained ◽  
Diagenetic Processes ◽  
Rock Structure ◽  
Scanning Electron

The albitization of K-feldspar is a common diagenetic process that has thus far received little attention and is not fully understood in fine-grained sedimentary rocks. To better understand the albitization of K-feldspar, studies in organic- and silt-rich fine-grained rocks of the lower Cambrian Qiongzhusi Formation in the southwestern Upper Yangtze region, China, were carried out via X-ray diffractometry (XRD) and field emission scanning electron microscopy (FE-SEM). The results show that five types of albitized K-feldspar textures have developed: microcrystal albite replacement, irregular blocky replacement along margins, cleavage planes or microcracks of K-feldspars, complete pseudomorphic replacement, albite overgrowth, and albite pore filling. Organic- and silt-rich fine-grained rocks differ from sandstones and mudstones in terms of the rock structure and mineral assemblage, which results in differences in the textures and degree of albitization of K-feldspar. Illitization of clay has an impact on the albitization of K-feldspar. In provenance analyses using feldspar, fine-grained rocks, especially those that underwent mesogenesis, should be treated with caution because detrital feldspars have been destroyed. Theoretically, the albitization of K-feldspar could increase the porosity of reservoirs, although, from our observations, most of the related secondary pores are cancelled out or became isolated pores due to other diagenetic processes (compaction, cementation, etc.) in organic- and silt-rich fine-grained rocks.

Portable X-Ray Fluorescence Analyzers and their use in an Underground Exploration Program for Tin

1979 ◽  
Vol 23 ◽  
pp. 19-25
Author(s):  
Mark W. Springett
Keyword(s):  
Mining Industry ◽  
Analytical Techniques ◽  
Drill Core ◽  
Current Interest ◽  
X Ray ◽  
Core Samples ◽  
South West ◽  
Surface Exploration ◽  
Fluorescence Analyzer ◽  
South West England

In 1968 Consolidated Gold Fields commenced exploration below adit level at the Wheal Jane tin prospect in south-west England. During the surface exploration program the relatively recently introduced Portable X-ray Fluorescence Analyzer (“P.I.F.“) had been used for semi-quantitative scanning of drill core and for providing preliminary assays for tin on prepared core samples. The P.I.F. was introduced to the mining industry in 1965 (Bowie et. al. (1) and had originally been equipped specifically for tin analysis due to the current interest in tin exploration, the difficulties of chemically assaying for tin and the suitability of tin to X-ray analytical techniques. The instrumentation and principals of operation have been described by Bowie (1,2). At Wheal Jane the need to obtain rapid analyses to help control underground development and difficulties in visually recognizing the tin mineralization made the prospect an excellent testing ground for the practical aspects of the instrument.

Direct Observation of Crystalline Ordering In Naturally Graphitized Carbon Produced by Low Grade Metamorphism

1977 ◽  
Vol 35 ◽  
pp. 162-163
Author(s):  
Thomas R. McKee ◽  
Peter R. Buseck
Keyword(s):  
Crystallite Size ◽  
Sedimentary Rocks ◽  
Carbonaceous Material ◽  
Low Grade ◽  
X Ray ◽  
Graphitized Carbon ◽  
Transmission Electron ◽  
Heat Treated ◽  
Commercial Carbon ◽  
Metamorphic Zone

Sediments commonly contain organic material which appears as refractory carbonaceous material in metamorphosed sedimentary rocks. Grew and others have shown that relative carbon content, crystallite size, X-ray crystallinity and development of well-ordered graphite crystal structure of the carbonaceous material increases with increasing metamorphic grade. The graphitization process is irreversible and appears to be continous from the amorphous to the completely graphitized stage. The most dramatic chemical and crystallographic changes take place within the chlorite metamorphic zone.The detailed X-ray investigation of crystallite size and crystalline ordering is complex and can best be investigated by other means such as high resolution transmission electron microscopy (HRTEM). The natural graphitization series is similar to that for heat-treated commercial carbon blacks, which have been successfully studied by HRTEM (Ban and others).

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