Caracteriza??o de minerais pesados usados como indicadores de dep?sitos minerais na bacia hidrogr?fica do Ribeir?o Maynart, Sul do Quadril?tero Ferr?fero, MG.

Programa de P?s-Gradua??o em Evolu??o Crustal e Recursos Naturais. Departamento de Geologia. Escola de Minas, Universidade Federal de Ouro Preto.O estudo de minerais indicadores ? uma das mais antigas t?cnicas de explora??o mineral usadas no mundo. Os minerais indicadores s?o esp?cimes minerais encontrados em gr?os que s?o transportados em sedimentos cl?sticos e indicam a presen?a de afloramentos, ? montante do ponto de coleta da amostra, que cont?m esses minerais e s?o associados ? alguma mineraliza??o, altera??o hidrotermal ou litologia. Os minerais indicadores tem como caracter?stica propriedades f?sicas e qu?micas, como alta densidade, facilidade de preserva??o em ambientes de intemperismo qu?mico e f?sico acentuados e f?cil identifica??o visual, de modo que permite sua correla??o com um grande n?mero de dep?sitos minerais, tais como: ouro, diamante, Ni-Cu, EGP, dep?sitos de cobre p?rfiro, sulfetos maci?os e tungst?nio. Na por??o sul do Quadril?tero Ferr?fero, dentre os dep?sitos minerais conhecidos de ferro, mangan?s, ouro, Cu-Au-Sb, Hg-Sb e minerais raros como top?zio e eucl?sio, existe uma ocorr?ncia mineral de diamante reportada desde o per?odo colonial na bacia hidrogr?fica do ribeir?o Maynart que ? objeto de curiosidade cient?fica. Uma vez que a regi?o da bacia hidrogr?fica do ribeir?o Maynart encontra-se em um contexto geotect?nico favor?vel ? ocorr?ncia de fontes prim?rias diamant?feras, e em fun??o do estudo de minerais indicadores ser amplamente usado na pesquisa de fontes prim?rias diamant?feras, esse trabalho dedicou-se ao emprego das t?cnicas explorat?rias de identifica??o e caracteriza??o de minerais pesados usados como indicadores de dep?sitos minerais com ?nfase nos minerais associados ? fontes prim?rias diamant?feras. Por?m, tamb?m foram analisados minerais indicadores de dep?sitos de sulfetos maci?os e/ou de altera??o hidrotermal. Dentre os principais resultados foram identificados 34 esp?cimes minerais das quais 03 foram analisadas do ponto de vista qu?mico para determinar o ambiente de cristaliza??o e sua poss?vel correla??o com dep?sitos minerais conhecidos. Como mineral indicador de fonte prim?ria diamant?fera reconhecido na bacia hidrogr?fica do ribeir?o Maynart destaca-se o diops?dio, que foi classificado como diops?dio sub-c?lcico, derivado de um manto eclog?tico e/ou peridot?tico, encontrado como xenocristais em lampro?to. O diops?dio ? um mineral que se altera muito facilmente em ambientes de intemperismo qu?mico acentuado, portanto sua recupera??o em amostras de concentrados de bateia indica que esse mineral encontra-se muito pr?ximo ? fonte. Al?m do diops?dio, tamb?m foram estudados gahnita e oxicalciorom?ita. A gahnita ? um espin?lio zinc?fero que ocorre como mineral acess?rio em granitos e pegmatitos, em rochas metam?rficas de m?dio para alto grau, em dep?sitos de sulfetos maci?os metamorfizados e em placers como minerais pesados. A composi??o qu?mica dos cristais de gahnita encontradas nas amostras de minerais pesados coletados na bacia hidrogr?fica do ribeir?o Maynart sugere que elas estejam associadas a dep?sitos metamorfizados de sulfetos maci?os de zinco ou a rochas metassedimentares ricas em Fe-Al. A oxicalciorom?ita ? um titano-antimoniato extremamente raro, por?m com uma relativa abund?ncia na regi?o de Ouro Preto, especialmente no c?rrego Tripu? aonde a oxicalciorom?ita correlaciona-se a um dep?sito de cin?brio. Uma hip?tese para a forma??o da oxicalciorome?ta encontrada na bacia hidrogr?fica do ribeir?o Maynart ? a associa??o com o dep?sito de Au-Cu-Sb de Bico de Pedra. Outro ponto que merece ser destacado ? que a rela??o Sb-Hg, como ? encontrado no c?rrego Tripu?, pode ser verificada em dep?sitos vulcanog?nicos de sulfetos maci?os (VMS) de zinco. Portanto a ocorr?ncia de oxicalciorom?ita associada ? gahnita na bacia hidrogr?fica do ribeir?o Maynart pode estar relacionado ? um dep?sito de sulfeto maci?o de zinco.The study of indicator minerals is one of the oldest technique used for mineral exploration in the world. Indicator minerals are mineral specimens found in grains that are transported in clastic sediments and indicate the presence of outcrops, which contains these minerals and are associated with mineralization, hydrothermal alteration and lithology. The indicator minerals has physical and chemical properties, such as high density, preservation in chemical and physical weathering environments and easy visual identification which allows their correlation with a large number of mineral deposits, such as gold, diamond, Ni -Cu, PGE, porphyry copper deposits, massive sulphide and tungsten. In the southern portion of the Iron Quadrangle several minerals deposits are known, like iron, manganese, gold, Cu- Au- Sb, Hg - Sb and gemstones. However, there is a diamond occurrence reported since the colonial period in the basin of Maynart creek that is scientific curiosity object. Once the Maynart creek region is located in a favourable tectonic setting to the occurrence of diamondiferous primary sources, and due to the indicator mineral study is widely used in research of diamond primary sources, this work focused in the characterization of indicator mineral with emphasis on diamond indicator minerals. However, it was also analyzed indicator minerals of massive sulphide deposits and/or hydrothermal alteration. In total were identified 34 mineral specimens, that's 03 were analyzed from a chemical point of view to determine the crystallization environment and its possible correlation with known mineral deposits. As diamondiferous indicator mineral highlights the diopside which was classified as sub-calc diopside, derived from a eclogitic and/or peridotitic mantle found in xenocrysts of lamproite. Once the diopside is a mineral that is changed very easily in severe chemical weathering environments, their recovery in concentrated samples of panning, indicates that the mineral phase is very close to the source. Besides the diopside were also studied gahnite and oxicalcioromeite . The gahnite is a zinciferous spinel occurs as accessory mineral in granites and pegmatites, in medium to high grade metamorphic rocks and metamorphosed massive sulphide deposits and placers as heavy minerals. The chemical composition of gahnite found in the Maynart Creek suggests that they are associated with metamorphosed massive zinc sulfides deposits or rich Fe-Al metasedimentary rocks.The study of indicator minerals is one of the oldest technique used for mineral exploration in the world. Indicator minerals are mineral specimens found in grains that are transported in clastic sediments and indicate the presence of outcrops, which contains these minerals and are associated with mineralization, hydrothermal alteration and lithology. The indicator minerals has physical and chemical properties, such as high density, preservation in chemical and physical weathering environments and easy visual identification which allows their correlation with a large number of mineral deposits, such as gold, diamond, Ni -Cu, PGE, porphyry copper deposits, massive sulphide and tungsten. In the southern portion of the Iron Quadrangle several minerals deposits are known, like iron, manganese, gold, Cu- Au- Sb, Hg - Sb and gemstones. However, there is a diamond occurrence reported since the colonial period in the basin of Maynart creek that is scientific curiosity object. Once the Maynart creek region is located in a favourable tectonic setting to the occurrence of diamondiferous primary sources, and due to the indicator mineral study is widely used in research of diamond primary sources, this work focused in the characterization of indicator mineral with emphasis on diamond indicator minerals. However, it was also analyzed indicator minerals of massive sulphide deposits and/or hydrothermal alteration. In total were identified 34 mineral specimens, that's 03 were analyzed from a chemical point of view to determine the crystallization environment and its possible correlation with known mineral deposits. As diamondiferous indicator mineral highlights the diopside which was classified as sub-calc diopside, derived from a eclogitic and/or peridotitic mantle found in xenocrysts of lamproite. Once the diopside is a mineral that is changed very easily in severe chemical weathering environments, their recovery in concentrated samples of panning, indicates that the mineral phase is very close to the source. Besides the diopside were also studied gahnite and oxicalcioromeite . The gahnite is a zinciferous spinel occurs as accessory mineral in granites and pegmatites, in medium to high grade metamorphic rocks and metamorphosed massive sulphide deposits and placers as heavy minerals. The chemical composition of gahnite found in the Maynart Creek suggests that they are associated with metamorphosed massive zinc sulfides deposits or rich Fe-Al metasedimentary rocks. The oxicalcioromeite is an extremely rare titano-antimoniate, but has a relative abundance in Ouro Preto, like the Tripu? creek that oxicalcioromeite is associated with a deposit of cinnabar. One hypothesis for the formation of oxicalcioromeite found in the Maynart creek is the association with the Au-Cu-Sb "Bico de Pedra" Deposit. Another point that deserves to be highlighted is that the Sb-Hg relationship, as found in Tripu? creek, can be seen in zinc VMS deposits. Therefore the occurrence of oxicalcioromeite associated with gahnite in the samples of heavy minerals from Maynart creek may be related to a massive zinc sulfide deposit