Exploration vectoring from the white mica spectral footprint in the atypical auriferous Lavra Velha deposit, San Francisco Craton, Brazil

Medina, Carlos Martín; Ducart, Diego Fernando; Passos, Josué Souza; Oliveira, Leandro Rocha de

doi:10.1016/j.oregeorev.2021.104438

Cited by 3 publications

(2 citation statements)

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“…Spectral indices are established by recognizing spectral gradients, i.e., the contrast of high and low reflectance in specific wavelength positions that demark a certain mineral to target. This procedure is observed in case studies of different deposits or prospects in the literature, such as Tappert et al (2011), Yang et al (2011), Prado et al (2016, Mesquita et al (2019), andMedina et al (2021), mainly for estimating the mineral abundance of specific mineral groups based on the depth of diagnostic absorption features or using spectral arithmetic. In this research, we analyzed the spectral responses of each lithotype and alteration zone (Fig.…”

Section: Spectral Indices To Target Exploratory Sitesmentioning

confidence: 99%

“…Spectral technologies appear as a powerful tool for exploration projects with already observed success mainly in metalliferous systems, such as VHMS, orogenic, SEDEX, and IOCG deposits (Tappert et al 2011, Fresia et al 2017, Lampinen et al 2019, Naleto et al 2019, Ross et al 2019, Medina et al 2021. The spectral technologies, such as reflectance and imaging spectroscopy, appear as advanced remote sensing data for detailed and rapid analysis of alteration minerals, including their distribution, and the definition of spectral indices as vectoring tools to locate proximal ore sites (Bedell et al 2009).…”

Section: Introductionmentioning

confidence: 99%

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Spectral characterization of the Umbuzeiro Doce skarn target (Brazil): insights for the exploration of a W-Mo-gemological vesuvianite system

et al. 2022

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The Umbuzeiro Doce skarn target in the Seridó Belt (NE Brazil) was studied using reflectance spectroscopy and petrography. Interpretation of the 61 reflectance spectra obtained in the study established the following zones: marble zone, with diagnostic absorption features at 2,340 and 2,475 nm (C-O); tremolite marble zone, with main absorption at 1,393 (OH − ) and 2,313 nm (Mg-OH); garnet-vesuvianite zone, with the main absorption at 2,215 nm (OH − ); diopside-hornblende zone, marked by a broad absorption at 1,153 nm (Fe 2+ ); late wollastonite zone, which lacks a diagnostic spectral signature; and a local violet vesuvianite-bearing marble, characterized by potential gemological vesuvianite marked by Cr 3+ absorption features (~548 and 680 nm). Centimeter-sized molybdenite aggregates occur at the interface of the marble and calc-silicate alteration zones. Spectral indices were produced to automate identification of potential zones to explore Mo, W, and gemological vesuvianite. Indices for the zones of marble, tremolite marble, garnet-vesuvianite, diopside-hornblende and violet vesuvianite were produced and tested. This methodology appears as a powerful exploratory guide for Mo, W, and violet vesuvianite occurrences or deposits that show a mineral zoning like the Umbuzeiro Doce target.

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Section: Spectral Indices To Target Exploratory Sitesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spectral characterization of the Umbuzeiro Doce skarn target (Brazil): insights for the exploration of a W-Mo-gemological vesuvianite system

et al. 2022

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New near-mine prospecting approach using multivariate analysis and reflectance spectroscopy to define surface footprint: A case study of the Pequizão Gold Deposit, Crixás Greenstone Belt, Central Brazil

Santos

Silva

Toledo

et al. 2023

Journal of Geochemical Exploration

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Advances for the Exploration of Tectonic-Magmatic-Related Emerald Deposits Using a High-Resolution Spectral Approach: Unraveling the Spectral Footprint of the Paraná Deposit (NE Brazil)

de Araújo Neto,

Andressa Carrino,

de Lira Santos

et al. 2024

Economic Geology

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This study unravels the spectral footprint of the Paraná deposit, northeastern Brazil, and provides strategies for emerald exploration in mafic- and/or ultramafic-hosted deposits using point spectral data and hyperspectral imaging. Potential host rocks (phlogopite and actinolite-phlogopite schists) were discriminated from other associated lithotypes after petrography and whole-rock geochemistry, using binary MgO versus Al2O3 and PC1 versus PC3 diagrams. Spectrally, phlogopite schist is marked by Fe-OH absorption at ~2,250 nm and Mg-OH absorptions at ~2,330 and ~2,388 nm. When actinolite is present, a shoulder at ~2,296 nm is recorded, and the first Mg-OH absorption feature is shifted to ~2,315 nm. Emerald crystals have their spectral signature attenuated in the presence of phlogopite. In a 5% emerald and 95% schist mixture simulation, two emerald absorption features are recognizable at ~1,150 (H2O absorption) and ~2,155 nm. The emerald indices EI1, EI2, and EI3 were chosen for the automated identification of emeralds in the Paraná samples based on the features at ~1,150, ~1,460, and ~2,155 nm. For the host schists, three indices were provided (MIdepth, MIratio, and ACI) considering the Mg-OH features of phlogopite and actinolite, allowing automated distinction between potential mineralized and other associated rocks of the Paraná deposit. Our results show that, operating in high-resolution mode (pixels of ~1 mm), imaging spectroscopy can detect the presence and characterize emerald in handpicked samples and drill cores based on chromium- and iron-derived absorption features in the visible to near infrared range. It thus represents a swift, reliable, nondestructive, and relatively cost-effective method for exploring for emerald and, potentially, other gems.

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Exploration vectoring from the white mica spectral footprint in the atypical auriferous Lavra Velha deposit, San Francisco Craton, Brazil

Cited by 3 publications

References 44 publications

Spectral characterization of the Umbuzeiro Doce skarn target (Brazil): insights for the exploration of a W-Mo-gemological vesuvianite system

Spectral characterization of the Umbuzeiro Doce skarn target (Brazil): insights for the exploration of a W-Mo-gemological vesuvianite system

New near-mine prospecting approach using multivariate analysis and reflectance spectroscopy to define surface footprint: A case study of the Pequizão Gold Deposit, Crixás Greenstone Belt, Central Brazil

Advances for the Exploration of Tectonic-Magmatic-Related Emerald Deposits Using a High-Resolution Spectral Approach: Unraveling the Spectral Footprint of the Paraná Deposit (NE Brazil)

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