Multi-stage tectonics and metallogeny associated with Phanerozoic evolution of the South China Block: A holistic perspective from the Youjiang Basin

Laser-induced breakdown spectroscopy (LIBS) and principal component analysis (PCA) were applied to the classification of LIBS spectra from gold ores prepared as pressed pellets from pulverized bulk samples. For each sample, 5000 single-shot LIBS spectra were obtained. Although the gold concentrations in the samples were as high as 7.7 µg/g, Au emission lines were not observed in most single-shot LIBS spectra, rendering the application of the usual ensemble-averaging approach for spectral processing to be infeasible. Instead, a PCA approach was utilized to analyze the collection of single-shot LIBS spectra. Two spectral ranges of 21 nm and 0.15 nm wide were considered, and LIBS variables (i.e., wavelengths) reduced to no more than three principal components. Single-shot spectra containing Au emission lines (positive spectra) were discriminated by PCA from those without the spectral feature (negative spectra) in a spectral range of less than 1 nm wide around the Au(I) 267.59 nm emission line. Assuming a discrete gold distribution at very low concentration, LIBS sampling of gold particles seemed unlikely; therefore, positive spectra were considered as data outliers. Detection of data outliers was possible using two PCA statistical parameters, i.e., sample residual and Mahalanobis distance. Results from such a classification were compared with a standard database created with positive spectra identified with a filtering algorithm that rejected spectra with an Au intensity below the smallest detectable analytical LIBS signal (i.e., below the LIBS limit of detection). The PCA approach successfully identified 100% of the data outliers when compared with the standard database. False identifications in the multivariate approach were attributed to variations in shot-to-shot intensity and the presence of interfering emission lines.

https://journals.sagepub.com/doi/pdf/10.1177/0003702819881444

Laser-Induced Breakdown Spectroscopy and Principal Component Analysis for the Classification of Spectra from Gold-Bearing Ores:

Effect of laser irradiance and wavelength on the analysis of gold- and silver-bearing minerals with laser-induced breakdown spectroscopy

The processing of refractory gold-containing concentrates by hydrometallurgical methods is becoming increasingly important due to the depletion of rich and easily extracted mineral resources, as well as due to the need to reduce harmful emissions from metallurgy, especially given the high content of arsenic in the ores. This paper describes the investigation of the kinetics of HNO3 leaching of sulfide gold-containing concentrates of the Yenisei ridge (Yakutia, Russia). The effect of temperature (70–85 °C), the initial concentration of HNO3 (10–40%) and the content of sulfur in the concentrate (8.22–22.44%) on the iron recovery into the solution was studied. It has been shown that increasing the content of S in the concentrate from 8.22 to 22.44% leads to an average of 45% increase in the iron recovery across the entire range temperatures and concentrations of HNO3 per one hour of leaching. The leaching kinetics of the studied types of concentrates correlates well with the new shrinking core model, which indicates that the reaction is regulated by interfacial diffusion and diffusion through the product layer. Elemental S is found on the surface of the solid leach residue, as confirmed by XRD and SEM/EDS analysis. The apparent activation energy is 60.276 kJ/mol. The semi-empirical expression describing the reaction rate under the studied conditions can be written as follows: 1/3ln(1 − X) + [(1 − X)−1/3 − 1] = 87.811(HNO3)0.837(S)2.948e−60276/RT·t.

/pdf/leaching-kinetics-of-sulfides-from-refractory-gold-1v5q9ojvhn.pdf

Leaching Kinetics of Sulfides from Refractory Gold Concentrates by Nitric Acid

Texture and geochemistry of pyrite from the Jinya, Nakuang and Gaolong gold deposits in the Youjiang Basin: implications for basin-scale gold mineralization

Gold in the Jinya Carlin-type deposit, assaying 6.27 g/t Au, was characterized using a comprehensive mineralogical and analytical approach which includes optical microscopy and several advanced microbeam techniques. Each gold carrier was quantified independently. Gold in the Jinya ore occurred as microscopic gold and submicroscopic gold. Submicroscopic gold, primarily in the form of solid solution gold, was carried mainly by arsenopyrite (accounting for 77% of the gold assay), and to a lesser extent (~16%) in arsenic-rich fine-grained and microcrystalline pyrite. Native gold accounted for 6% of the gold assay. Gold carried in cinnabar and rock minerals is insignificant . Gold deportment shows that (1) arsenopyritization and pyritization can be used as indication of mineralizatio n for the further exploration in the Jinya district, and (2) gold in sulfide s is not amenable to direct cyanidation, but can be recovered by flotation of a sulfide concentrate and then cyanidation with a pretreatment process.

/pdf/gold-in-the-jinya-carlin-type-deposit-characterization-and-4hvwlss1fd.pdf

Gold in the Jinya Carlin-type Deposit: Characterization and Implications

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Gold in the Jinya Carlin-type Deposit: Characterization and Implications