Weathering Conditions Evaluation of Banded Iron Formations of Bonito Mine (Northeastern Brazil) Based on Coupled Cluster-Correspondence Analysis

Authors

  • Helano Regis da Nóbrega Fonteles Universidade Federal do Ceará. Programa de Pós-graduação em Geologia, Avenida Mister Hull, s/n. Bloco 913. 60455-760. Fortaleza - CE, Brasil
  • Henrique Garcia Pereira Universidade de Lisboa, Instituto Superior Técnico, CERENA (Centro de Recursos Naturais e Ambiente), Avenida Rovisco Pais, 1. 1049-001. Lisboa, Portugal
  • César Ulisses Vieira Veríssimo Universidade Federal do Ceará. Programa de Pós-graduação em Geologia, Avenida Mister Hull, s/n. Bloco 913. 60455-760. Fortaleza - CE, Brasil

DOI:

https://doi.org/10.11137/2019_2_86_99

Keywords:

Itabirites, multivariate modeling, methodological strategy, weathering grades, Serra dos Quintos Formation

Abstract

This research was focused on weathering conditions regarding Banded Iron Formations (BIF) ore exploitation at Bonito Mine. The database is stemmed from an exhaustive drilling program at the mining site. Therefore, hundreds of iron ore samples were assayed for Fe2O3, SiO2, Al2O3, P and Mn grades, and qualitative geotechnical data such as weathering grades, physical ore type, voids, and coring depth levels were collected from drilling core samples. A previous petrographic study has shown that there are four BIF types: amphibolitic itabirites, martitic itabirites, hematitic itabirites, and magnetitic itabirites. In order to enhance this study, a multivariate model using geochemical and geotechnical data under a systemic approach was employed. This approach was conceived to account for the whole available information, both quantitative and qualitative, through the Correspondence Analysis and Cluster Analysis grounded appropriate methodology. This innovative strategy disclosed the presence of two groups of samples, denoted in the sequel Cluster 1 and Cluster 2. Cluster 1 is characterized by the Fe-poorer/High-Al BIF ores describing an association of magnetitic itabirites, martitic itabirites to amphibolitic itabirites which are conditioned to depths deeper than 70 meters and they usually stand as slightly weathered rocks or fresh rocks. Cluster 2 encompasses Fe-richer/Low-Al BIF ores composed of martitic, magnetitic and hematitic itabirites which are described as moderate to highly weathered porous friable ore materials. The proposed multivariate modeling strategy can deal with a wide range of miscellaneous geological issues.

Downloads

Published

2019-12-01

Issue

Section

Article