Hybrid multivariate typological model for the banded iron formations from the Bonito mine, Northeastern Brazil

Fonteles, Helano Regis da Nóbrega; Veríssimo, César Ulisses Vieira; Pereira, Henrique Garcia; Barbosa, Irla Gonçalves

doi:10.1016/j.apgeochem.2020.104779

Cited by 2 publications

(5 citation statements)

References 27 publications

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“…This ancillary information could improve the decision-making in mining planning. Fonteles et al (2020) proposed a typological model for itabirites from the Bonito mine. The thickness data is Anu.…”

Section: Discussionmentioning

confidence: 99%

“…Geociênc., 2022;45:40955 Group, described by Angelim, Medeiros and Nesi (2006) as a metasedimentary sequence formed by the following units: Serra dos Quintos Formation (BIFs, marble, ferruginous quartzite, amphibolite, and schist), Jucurutu Formation (primarily paragneiss, marble, quartzite, iron formations and metaconglomerate), Equador Formation (muscovitequartzite) and Seridó Formation (feldspathic mica schist) (Figure 2). The BIF rocks of the Serra dos Quintos Formation gather an assemblage of itabirites (proto-iron ore types) previously studied by Barbosa (2013), Fonteles et al (2019a), Fonteles, Pereira and Veríssimo (2019b) and Fonteles et al (2020).…”

Section: Lithostratigraphymentioning

confidence: 99%

“…A survey was performed throughout the entire databank to extract the available thickness data values (measured in meters) from drill core logs that intersected the BIF rocks (itabirites) pertained to the Serra dos Quintos Formation (Figure 1). Based on the typological model proposed by Fonteles et al (2020), three BIF types were pre-selected owing to their Fe 2 O 3 grades. Hematitic itabirites, magnetitic itabirites, and martitic itabirites represent BIF types with a 44.61% Fe 2 O 3 mean grade (Table 1).…”

Section: Thickness Datamentioning

confidence: 99%

“…The study area is located at the Bonito mine, Northeastern Brazil (Figure 1), where low-grade iron ore is constrained by the banded iron formations (itabirites), which were previously studied by Barbosa (2013), Fonteles et al (2019a) and Fonteles et al (2020). The regional mapping works by Van Schmus et al (2003), and Angelim, Medeiros and Nesi (2006) recognized the BIF rocks as a relevant lithotype in the Serra dos Quintos Formation owing to their geological significance.…”

Section: Introductionmentioning

confidence: 99%

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Geostatistical Mapping of Folded Itabiritic Rocks of the Bonito Mine, Northeastern Brazil

Fonteles¹,

Veríssimo

2022

Anu. Inst. Geociênc.

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Geological modeling is the primary task of any exploratory geological investigation, and it is performed even during the mine development. In the study area, the Serra dos Quintos Formation hosts banded iron formations represented by assorted itabirites. The database used in this work was exploited from a geological databank which was structured to gather data and information depicted from an exhaustive exploratory drilling program. A survey was performed throughout the entire databank to collect the available thickness data values (measured in meters) from drill core logs that intersected the itabirite. Since structural heterogeneities can occur within these rocks, this study aims to identify such features. Geostatistical estimation and simulation methods were employed to map folded itabiritic beds based on thickness data accurately. Kriging estimators are often used for practical reasons; however, sometimes, the estimates can be smoothed and do not represent the entire original data range. Simulation algorithms can yield several stochastic images, but local accuracy cannot always be guaranteed. Simulated annealing was performed by adjusting the global statistics and preserving the local accuracy. We demonstrated that the banded iron formations’ thicker areas might correspond to the antiform fold as the dominant tectonic feature in the study area. Finally, we show that the simulated thickness map discloses the thicker mineralized spots. Meanwhile, the thinner ones may unveil intrinsic structural heterogeneities mainly observed at the limbs of the Bonito fold, where intensive deformation within the itabiritic layer was higher than expected. Concerning the mining issues, information obtained from the simulated thickness map could provide ancillary data to improve mining planning in the study area.

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Section: Discussionmentioning

confidence: 99%

Section: Lithostratigraphymentioning

confidence: 99%

Section: Thickness Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Geostatistical Mapping of Folded Itabiritic Rocks of the Bonito Mine, Northeastern Brazil

Fonteles¹,

Veríssimo

2022

Anu. Inst. Geociênc.

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“…K-means clustering analysis allows the quick division of research objects into relatively homogeneous groups [55][56][57]. Fisher discriminant analysis, one of the most important multivariate statistical analysis methods, can summarize the common feature from various groups to obtain discriminant formulae, identifying the accuracy of clustering analysis [58].…”

Section: Ftirmentioning

confidence: 99%

The impact of trace metal cations and absorbed water on colour transition of turquoise

Wang

Guo

2021

R. Soc. open sci.

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Thirty-five gem-quality turquoise samples with various colours were investigated using energy-dispersive X-ray fluorescence spectroscopy, ultraviolet–visible spectroscopy, Fourier-transform infrared spectroscopy and scanning electron microscopy. Sample chemical and spectral analyses indicate that Fe 3+ contributes to green hue of turquoise, whose absorption band exhibits a bathochromic shift from 426 to 428 nm with increasing V content in the solid-solution series turquoise-chalcosiderite. V 3+ enhances absorption in the blue and orange regions, and Cr 3+ increases absorption in the green region, both of which are responsible for the vivid greenish yellow in faustite. Substitutions of Al by medium-sized trivalent cations (primarily Fe 3+ and V 3+ ) enhance polarity of the phosphate group (PO 4 ) 3− , resulting in strong absorption in the infrared spectra for analogues of turquoise. The reflectivity ratio ( R OH ) of the double absorption peaks at 781 and 833 cm −1 allows faustite to be distinguished from turquoise and chalcosiderite, with a value greater than 1, while V-rich faustite only has a single absorption peak at 798 cm −1 . An increasing amount of absorbed water contributes to blue chroma in turquoise and has a negative effect on lightness based on the CIE 1976 L * a * b * colour system. Loose turquoise with a low specific gravity tends to display greater colour differences with a significant decrease in lightness.

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Hybrid multivariate typological model for the banded iron formations from the Bonito mine, Northeastern Brazil

Cited by 2 publications

References 27 publications

Geostatistical Mapping of Folded Itabiritic Rocks of the Bonito Mine, Northeastern Brazil

Geostatistical Mapping of Folded Itabiritic Rocks of the Bonito Mine, Northeastern Brazil

The impact of trace metal cations and absorbed water on colour transition of turquoise

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