PEG2009 PRE-SYMPOSIUM FIELD TRIP GUIDE: EASTERN BRAZILIAN PEGMATITE PROVINCE (MINAS GERAIS)

Abstract

Pegmatite gemstones became officially known in the Brazil history since the last decades of the 17th century, when green tourmalines were found in the central-northeastern Minas Gerais region by Fernão Dias Paes Leme, one of the most famous leaders of Brazilian colonizers. Later, pioneer naturalists and geologists of the 19th century first decades, such as von Eschwege, von Spix & von Martius and Saint-Hilaire, referred to pegmatite gem deposits and/or trading of coloured gems in regions of the Araçuaí, Jequitinhonha, Doce and Mucuri river valleys. However, only in the 20th century, particularly during and after the Second World War, pegmatites became important mineral deposits in Brazil owing to efforts to increase the production of mica, beryl and quartz for the USA military industry. This mining development was accompanied by pioneer geologic studies and several new mineral specimens were discovered. Accordingly, the Brazilian pegmatite populations were grouped into the Eastern, Northern and Southern Brazilian pegmatite provinces. These provinces were defined mainly based on the geographical distribution of pegmatites, because at that time Brazil lacked geological maps even for a regional approach. This guide was elaborated for a pre-symposium field trip held before 2009 PEG - 4th International Symposium on Granitic Pegmatites, and focused on different aspects of pegmatites located in three important districts of the Eastern Brazilian Pegmatite Province (EBPP), namely São José da Safira, Conselheiro Pena and Araçuaí pegmatite districts. The field trip included from primitive garimpos for mineral exploitation to a very organized mine, showing pegmatites with different mineral (beryl, phosphate, spodumene or tourmaline) specializations that are related to distinct geologic settings and genetic conditions. A visit to a quarry for dimension stone on a pegmatite body was also scheduled. This guide also presents a synthesis on the geologic setting of the main EBPP pegmatite districts and their main features, followed by brief descriptions of the field trip stops. Those were the Ipê Pegmatite in Governador Valadares town, Sapucaia Pegmatite in the town of Galileia, Boa Vista and Cigana Pegmatites in the town of Conselheiro Pena, K2 Ornamental Pegmatite Quarry in Itinga town, CBL Spodumene Mine in Araçuaí town, Água Santa Mine and a pegmatite swarm which occurs along a road cut of the BR-342, both located in the town of Coronel Murta.