EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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2 resultados
Resultados da Pesquisa
Item Magmatic-hydrothermal fluids leaching older seafloor exhalative rocks to form the IOCG deposits of the Carajás Province, Brazil : evidence from boron isotopes.(2021) Melo, Gustavo Henrique Coelho de; Monteiro, Lena Virginia Soares; Hunger, Raphael Bianchi; Toledo, Poliana Iara Freitas; Xavier, Roberto Perez; Zhao, Xin-Fu; Su, Zhi-Kun; Moreto, Carolina Penteado Natividade; Jesus, Silvandira dos Santos Goes Pereira deThe notable group of iron oxide-copper–gold (IOCG) deposits at the Carajas Province (Amazonian Craton, Brazil) contain remarkable copper reserves due to a complex Neoarchean metallogenetic evolution. The overlay of diachronic hydrothermal-mineralizing events is revealed by two clusters of boron isotope compositions of hy- drothermal tourmaline obtained in IOCG deposits (Salobo, Igarap ́e Bahia, GT-46, Grota Funda and Furnas) with (i) high δ11B (+8.2 to +17.2‰) and (ii) low δ11B (+3.4 to +9.8‰) values. The isotopically heavy boron sig- natures, recorded in tourmaline cores, are inherited from the volcano-sedimentary sequences of the ca. 2.76 Ga Itacaiúnas Supergroup, which includes exhalative tourmaline and spilites formed in extensive exhalative systems prior to the IOCG formation. During the main IOCG event at ca. 2.55 Ga, the regional circulation of magmatic- hydrothermal boron-rich fluids originated tourmaline rims and new crystals with lower δ11B values. We describe the critical role of an older volcano-sedimentary as a source for boron and likely metals leached by magmatic- hydrothermal fluids to form the IOCG deposits of the Carajas ́ Province.Item The Santa Lúcia Cu-Au deposit, Carajás Mineral Province, Brazil : a Neoarchean (2.68 Ga) member of the granite-related copper-gold systems of Carajás.(2021) Hunger, Raphael Bianchi; Melo, Gustavo Henrique Coelho de; Xavier, Roberto Perez; Moreto, Carolina Penteado Natividade; Talavera, Cristina; Su, Zhi-Kun; Zhao, Xin-FuThe Santa Lúcia copper-gold deposit lies in the southeastern portion of the Carajás Mineral Province, along NW-SE splays of the Carajás Fault. The deposit is hosted by a rhyolitic subvolcanic rock, which is crosscut by pegmatite intrusions. The paragenetic evolution at Santa Lúcia encompasses an early stage of chlorite alteration, followed by potassic alteration with microcline, greisenization (quartz-muscovite-tourmaline), copper-gold ore precipitation, and late sericite and hematite vein formation/ fracture infill. Copper mineralization is dominantly represented by chalcopyrite-sphalerite-pyrrhotite-pentlandite-pyrite breccias, which are spatially associated with greisen alteration and characterized by the enrichment of light rare earth elements (LREE), Ni, Co, and Cr. The alteration types, mineralization styles, and ore assemblage suggest that the Santa Lúcia deposit could represent a member of the Paleoproterozoic (ca. 1.88 Ga) granite-related copper-gold systems of Carajás (e.g., the Breves and Estrela deposits). However, the in situ U-Pb analyses of ore-related monazite yield a weighted average 207Pb/206Pb age of 2688 ± 27 Ma, thereby constraining the timing of mineralization at Santa Lúcia to the Neoarchean. Moreover, tourmaline from the pegmatite and within the ore zones has a range of δ11B values from − 3.7 to − 0.6‰, therefore linked to a magmatic boron source. Collectively, these results indicate that the Santa Lúcia deposit is the first reduced magmatic-hydrothermal, iron oxide–poor system formed in the Neoarchean, coeval with the 2.72–2.68 Ga metallogenic event responsible for the genesis of important iron oxide copper-gold (IOCG) deposits in the Carajás Mineral Province.