Actions and Perspectives of the Geological Service of Brazil in the Promotion of the Lithium Business in the Country

The Geological Survey of Brazil (CPRM) has been carrying out a prospective project called Assessment of the Lithium Potential in Brazil since 2012. The main goal is to improve the knowledge about the pegmatite-related lithium deposits in Brazil and their geological context. The first stage of the project (Paes et al., 2016) was carried out in the Jequitinhonha valley region located in northeastern Minas Gerais State (southeastern Brazil). This area belongs to the Eastern Brazilian Pegmatite Province and comprises 100% of the official lithium reserves of Brazil.

Since it is a prospective project, actions were taken to establish the critical conditions of the lithium mineralizations and also their prospecting guides. The main actions carried out included: (i) the creation of an adequate geologic map (1:100,000 scale) of the study area (17,750 km2); (ii) the petrographic and geochemical (whole-rock) study of Cambrian peraluminous granites of the S-type –Ąő≥4S Granitic Suite (lithium pegmatites are genetically related to –Ąő≥4S Granitic Suite); (iii) the study of contact and regional metamorphic mineralogy of the metasediments (Neoproterozoic) that host the pegmatites; (iv) field study of 45 lithium occurrences/deposits (20 unpublished until that time); (v) sampling of pegmatites, the soils derived from them and their host rocks for spectral study (ASTER images); (vi) processing and interpretation of Gamma ray spectrometry and magnetometric airborne surveys data; (vii) compiling of geological information on the mineral chemistry of pegmatites and geochemistry of the host rocks from the studied region, as well as on the use of geochemical prospecting of stream sediments to locate lithium deposits.

The applied methodology led to an improvement of geological models for the lithium deposits in the study area. This allowed to propose an exploratory model for the deposits that is based on the identification and mapping of the metallotects and prospecting guides for the mineralizations. Other relevant results include the identification of new areas with potential for discoveries of lithium deposits.

The second stage of the project started in 2017 and comprises the Borborema Pegmatite Province in Rio Grande do Norte and Paraíba States (northeastern Brazil). Other areas with lithium occurrences in Brazil are: (1) Solonópole region (Ceará State); (2) eastern Minas Gerais State; (3) São João Del Rei region (southern Minas Gerais State); (4) Itambé region (southern Bahia State); (5) southern Tocantins State and northeastern Goiás State; (6) northwestern Rio de Janeiro State and southeastern Minas Gerais State. The geological knowledge of these areas is heterogeneous, and all of them need additional studies focusing on the metallogenic aspects of the lithium pegmatites in order to evaluate their real potential for discovery of new deposits.

CPRM has great interest in creating scientific cooperation programs with international institutions concerning the prospecting and exploration of pegmatite-related lithium deposits. The exchange of technology and knowledge could approach many scientific subjects such as: (i) the use of different exploration tools for assessing the lithium potential of a region such as: whole-rock chemistry of granites; chemistry of minerals from granites; geochemistry of host rocks of pegmatites; chemistry of minerals from pegmatites; study of fluid inclusions in minerals from pegmatites; (ii) geochemical mapping and exploration geochemistry for lithium, concerning exploration data analysis (uni, bi and multivariate statistical analysis techniques), analytical and sampling methods, and the results of different geological matrixes (rock, soil, sediments and surface water/groundwater); (iii) the application of multivariate statistical analysis techniques by aggregating data from all airborne gamma-spectrometric, magnetometric, electromagnetic and multispectral or remote sensing hyperspectral data channels in pilot areas, in order to extract the maximum information contained in these data in large sampling populations for lithostructural cartography, detection of zones of hydrothermal alteration and favorability to the emplacement of pegmatitic bodies.

In recent years CPRM has developed a lithium ore spectral library that comprises up to 1000 spectral signatures of Li-pegmatite deposits (including mineralized veins, wall rock alteration and host rocks). This library can allow the spectral, mineralogical and compositional characterization of lithium deposits and also help the identification of mineralized bodies in remote sensing images.

Paes, V.J.C.; Santos, L.D.; Tedeschi, M.F.; Betiollo, L.M., 2016. Avaliação do potencial do lítio no Brasil: área do Médio Rio Jequitinhonha, Nordeste de Minas Gerais. Belo Horizonte: CPRM - Companhia de Pesquisa de Recursos Minerais. Disponível em http://www.cprm.gov.br.

Vin√≠cius Jos√© de Castro Paes, Eduardo Duarte Marques, Fernando Ant√īnio Rodrigues de Oliveira, M√īnica Mazzini Perrotta, Luana Duarte Santos
Serviço Geológico do Brasil - CPRM

Figure 1: spodumene (greenish)-rich pegmatite in a new area with potential for discovery of lithium deposits. Fazenda Bananal Artisanal Mining - Itinga Pegmatitic Field. Jequitinhonha valley region.

Figure 2: spodumene (white)-rich pegmatite in a new area with potential for discovery of lithium deposits. Severino Artisanal Mining - Itinga Pegmatitic Field. Jequitinhonha valley region.

Figures 3 and 4: spodumene (white)-rich pegmatite in a new area with potential for discovery of lithium deposits. Zué/Dim Artisanal Mining - Curralinho Pegmatitic Field. Jequitinhonha valley region.