Geologia e caracterização tecnológica do minério de manganês da mina Córrego do Cocho, Itapira (SP)

Abstract

RESUMOTrês jazimentos de manganês e uma mina geneticamente resultantes da lateritização de gonditos (espessartita quartzitos) foram pesquisados. Estas concentrações encontram-se hospedadas em metassedimentos do Grupo Itapira (Paleoproterozoico) e apresentam recursos em torno de 2,0 x 10 6 Mt, com teor médio de 23% MnO 2 . Os principais minerais de minério são constituídos por criptomelana, pirolusita, litioforita, espessartita e psilomelana. O minério apresenta arranjos texturais dos mais variados, bem como se concentra em distintas frações granulométricas, quando benefi ciado e concentrado. O estudo permitiu defi nir variadas formas no contorno dos grãos associados a distintos arranjos texturais e, a associação do grau de liberação do minério aos mesmos. Empregaram-se ensaios por separação em líquido denso a fi m de caracterizar o miné-rio e seu grau de liberação, posto que a fração granulométrica mais fi na, (0,074 a 0,84 mm) era perdida no processo de benefi ciamento. Assim, o teor médio muito baixo no concentrado (28% MnO 2 ) se devia à perda para esta fração granulométrica (-0,074 mm), que contém teor elevado, próximo de 40% MnO 2 . Isto indica que seu emprego é adequado apenas para produção de fertilizantes (sulfato de manganês). Estudo comparativo com outras jazidas, principalmente a Mina de Caneleiras, em Ouro Fino (MG), indicou que o maior grau de liberação ocorre associado à granulação mais grossa (0,84 a 0,074 mm com teor de 38% em MnO 2 ), que permite seu emprego na indústria de ligas Fe-Si-Mn.Palavras-chave: Depósitos de manganês; Gonditos; Grupo Itapira; Grau de liberação; Tecnologia mineral; Sulfatos de manganês. ABSTRACTThe objects of this study are three manganese ore deposits and one mine derived from lateritic weathering of gondites (spessartine quartzites). These deposits are associated with Mn-rich garnet metasediments of the Itapira Group (Paleoproterozoic) and the reserves were estimated at approximately 2.0 x 10 6 tons with an average grade of 23% MnO 2 . The ore minerals are cryptomelane, pyrolusite, lithiophorite, spessartine and psilomelane. Several crystal shapes and textural characteristics were identifi ed in this study, which are related to the degree of liberation, as confi rmed by heavy media separation method. In this study, we determined the main characteristics of the liberation of manganese, which is concentrated in the fi ne grain-size fraction and is lost during ore dressing. Therefore, the low average content of MnO 2 (28%) is due to this loss, whereas at grain size of minus 0.074 mm, contents near 40% MnO 2 were observed. This suggests that the ore can be used for manufacturing manganese sulphate fertilizers. A comparative study with the ore deposits located at Ouro Fino (MG), mainly with the Caneleiras mine, showed that higher degree of liberation occurs in the coarse grain-size fractions (0.84 to 0.074 mm with MnO 2 content of 38%). As a consequence, the ore can be used for manufacturing Fe-Si-Mn alloys.

Geophysical characterization in aid for geological reconnaissance of Manganese occurrence

“…The manganese protomineral found in the Itapira Group is classified regarding the genesis in: silicate protomineral composed mainly of quartz and spessartite in approximately similar proportions, and calcium silicate, with quartz, spessartite, pyroxenes, amphiboles, plagioclase, carbonates and epidote (Angeli et al, 2011).…”

“…Therefore, the spacial extension of supergenic deposits is frequently much high when compared in dimension area to the primary deposits, which can in many cases, difficult to estimate mineral deposits dimensions in preliminary stages of mineral exploration. This paper presents and discuss a combined interpretation of geological and geophysical data obtained in an area that has a mineral occurrence of manganese described by Angeli et al (2011), in the region of Itapira, São Paulo state. The objective are order to evaluate surface dimensions of this occurrence and ore typology in its geological aspects, and the geophysical characterization of the ore and its continuity in subsurface.…”

Geophysical modeling of the manganese deposit for Induced Polarization method in Itapira (Brazil)

“…The Itapira Group, which hosts the manganese occurrences in the area, is an allochthonous metavolcano-sedimetary sequence, trusted over the older rocks of the Amparo Complex. The group is composed mainly by quartzites, schists, quartz schists, silimanite-garnet paragneisses and subordinated gondites (Wernick, 1976;Arthur, 1980;Veríssimo, 1991;Angeli et al, 2011). The rocks of the Itapira Group show a complex structural pattern, characterized by high angle dextral sense shear zones that are consistent with a transpressive deformation in a ductile to ductile-brittle regime.…”

“…A few lateritic manganese occurrences are found in the area, of which some of them have been studied in terms of their mineralogical and chemical composition, genesis and ore processing (Zanardo, 2003;Veríssimo, 1991;Angeli, 2011). The occurrences are arranged in a NNE-trend, coincident with the area main structural trend and separated from each other by a few hundreds of meters (Figure 2).…”

“…Two different types of protores are found in the deposits: silicate protore (essentially quartz and spessartite in equal proportions) and silicate-carbonate protore (rhodochrosite, rhodonite, pyroxenes and amphyboles in addition to quartz and spessartite). Graphite is found in both ore and protore, in amounts that can reach up to 10% (Veríssimo, 1991;Angeli et al, 2011). The mineralogy of the protore and the presence of graphite suggest a terrigeonous source for the metal and a meta-sedimentary origin for the manganese orebodies (Veríssimo, 1991).…”