Diferenças Entre os Depósitos Auríferos do Grupo Aguapei (Estado de Mato Grosso) e os Clássicos Exemplos de Ouro em Conglomerados

Gold prospects in the Aguapeí Folded Belt are situated in the southwestern portion of the Amazon Craton, within the Alto Guaporé Province, southwestern state of Mato Grosso. The mineralizations are mainly concentrated in the Pau-a-Pique Deposit (south), Lavrinha Region (central), and São Vicente Mine (north). Gold ore comprises quartz veins and disseminations in the low-grade metamorphic metassedimentary rocks from the Aguapeí Group. This stratigraphic unit was strongly deformed by the Sunsás-Aguapeí Orogeny (1.28-0.95 Ga). The Aguapeí gold deposits differ in their petrography, chemistry, structural aspects and age from world classic gold deposits associated with coarse clastic sedimentary sequences (Witwatersrand, Jacobina, Tarkwa, etc.). This study discusses the main differences between Aguapeí gold deposits and the classic worldwide deposits hosted by conglomeratesGold prospects in the Aguapeí Folded Belt are situated in the southwestern portion of the Amazon Craton, within the Alto Guaporé Province, southwestern state of Mato Grosso. The mineralizations are mainly concentrated in the Pau-a-Pique Deposit (south), Lavrinha Region (central), and São Vicente Mine (north). Gold ore comprises quartz veins and disseminations in the low-grade metamorphic metassedimentary rocks from the Aguapeí Group. This stratigraphic unit was strongly deformed by the Sunsás-Aguapeí Orogeny (1.28-0.95 Ga). The Aguapeí gold deposits differ in their petrography, chemistry, structural aspects and age from world classic gold deposits associated with coarse clastic sedimentary sequences (Witwatersrand, Jacobina, Tarkwa, etc.). This study discusses the main differences between Aguapeí gold deposits and the classic worldwide deposits hosted by conglomerates

Nova unidade litoestratigráfica registra glaciação ediacarana em Mato Grosso: formação Serra Azul

A new succession of diamictites and siltstones was found above post-Marinoan carbonates from the Araras Group in the northern Paraguay Belt (Brazil), in discontinuous outcrops. This new stratigraphic unit, named Serra Azul Formation in this work, has a variable thickness reaching up to 300 meters. The diamictites were deposited in the first 70 m and present glacial evidences, while the siltstones represent the upper part of the succession and show some sandstone layers towards the top of the succession. This glacial record is the youngest Neoproterozoic glacial event that has been found on South America and probably is related to Gaskiers Glaciation (582 Ma).Uma nova sucessão de diamictitos e siltitos foi encontrada acima dos carbonatos pós-Marinoanos do Grupo Araras, na porção norte da Faixa Paraguai, em afloramentos descontínuos. Esta nova unidade estratigráfica é denominada Formação Serra Azul neste trabalho, possui espessura muito variável, de 60 a 300 m. Na seção tipo, os diamictitos foram depositados nos primeiros 70 m e possuem evidências glaciais, como clastos polimíticos facetados e estriados, enquanto que os siltitos ocorrem ao longo do restante da sucessão, sendo intercalados por camadas de arenito no topo. Este registro glacial é o primeiro encontrado na América do Sul que pode estar relacionado à Glaciação Gaskierana (582 Ma)

STRUCTURAL, STRATIGRAPHIC AND METALLOGENETIC ASPECTS OF THE PARAGUAY FOLD AND THRUST BELT: IMPLICATIONS FOR GOLD MINERALIZATION AND COLLAGE OF THE GONDWANA: Aspectos estruturais, estratigráficos e metalogenéticos do Cinturão de Dobramentos e de Cavalgamento Paraguai: implicações para a mineralização do ouro e colagem do Gondwana

ABSTRACT - Paraguay Belt occupies the western portion of the Tocantins Province, surrounding the Southeast of the Amazonian Craton and the eastern border of the Rio Apa Block, suggesting continuity with Tucavaca Belt in Bolivia. The rocks of the Paraguay belt were initially deposited in a glaciomarine environment in sites proximal to the cratonic area and deeper marine under the influence of turbidite flows in distal sites (Cuiabá Group, Bauxi and Puga Formation). The cap carbonates, thick limestone and dolostone succession of the Araras Group and siltstones and diamictites of the Serra Azul Formation related to Glaskiers glaciation overlay these diamictites (related to Marinoan glaciation). On the top there are terrigenous sediments of the Alto Paraguay Group, represented by sandstones of Raizama and claystones of Diamantino formations, respectively. The belt can be divided into three distinct structural zones: The Internal Domain is comprised of turbidite and glaciogenic sequences. Glaciogenic rocks on the base and carbonaceous and terrigenous sediments on the top occur in the External Domain. Horizontal platformal cover on the Amazonian Craton rocks are characterized by open folds. Structural studies allowed characterization of continuous deformational phases: the main deformational phase generated regional inverse folds with a NE-SW trend and fan geometry. Several regionally widespread lode-type gold deposits related to four types of the quartz veins were identified: type 1 is in concordance to bedding, type 2 is parallel to Sn, type 3 is parallel to Sn+2, and vertical Type 4 (Au-rich) is orthogonal to Sn. Late deformation developed in the Cuiabá region, recorded the closure of the ocean and the invertion where the hydrothermal fluids are the responsible for the orebodies formation. Keywords: Paraguay Belt, Structural, Stratigraphy, Metalogenesis.RESUMO – O Cinturão do Paraguai ocupa a porção oeste da Província do Tocantins, ao redor do sudeste do Cráton Amazônico e a leste do Bloco Rio Apa e aparenta ter continuidade com o Cinturão Tucavaca na Bolivia. As rochas do cinturão do Paraguai foram inicialmente depositadas em um ambiente glaciomarino em locais próximos à área cratônica (Formação Puga) e marinhos mais profundos sob a influência dos fluxos de turbidito em locais distais (Grupo Cuiabá e Formação Bauxi). Os carbonatos de topo e dolomitos do Grupo Araras e siltitos e diamictitos da Formação Serra Azul provavelmente estão relacionados à glaciação Glaskiers que cobrem os diamictitos relacionados à glaciação Marinoana. No topo, existem sedimentos terrestres do Grupo Alto Paraguai, representados por arenitos da Formação Raizama e arenitos da Formação Diamantino. O cinturão pode ser dividido em três zonas estruturais distintas: O Domínio Interno é constituído por turbiditos e sequências glaciogênicas. Rochas glaciogênicas na base e sedimentos carbonáticos no topo ocorrem no domínio externo. Outros sedimentos com dobras abertas ocorrem na área do Cráton da Amazônia e é caracterizado como uma cobertura platformal. Os estudos estruturais sugerem fases deformacionais contínuas, sendo a principal fase deformacional responsável pela formação de dobras inversas vergência NE-SW e geometria tipo fan. Foram identificados vários depósitos de ouro do tipo filão relacionados a quatro tipos de veios de quartzo: o tipo 1 é paralelo ao acamamento; o tipo 2 é paralelo ao Sn; o tipo 3 é paralelo ao Sn + 2; e o tipo 4 é ortogonal a Sn, sendo o mais enriquecido em Au. As deformações desenvolvidas na região de Cuiabá registraram a deposição em ambiente marinho e inversão tectônica, onde os fluidos metamórficos são os responsáveis pelas mineralizações. Keywords: Cinturão Paraguay, Estrutural, Estratigrafia, Metalogêne

Diferenças Entre os Depósitos Auríferos do Grupo Aguapei (Estado de Mato Grosso) e os Clássicos Exemplos de Ouro em Conglomerados

Gold prospects in the Aguapeí Folded Belt are situated in the southwestern portion of the Amazon Craton, within the Alto Guaporé Province, southwestern state of Mato Grosso. The mineralizations are mainly concentrated in the Pau-a-Pique Deposit (south), Lavrinha Region (central), and São Vicente Mine (north). Gold ore comprises quartz veins and disseminations in the low-grade metamorphic metassedimentary rocks from the Aguapeí Group. This stratigraphic unit was strongly deformed by the Sunsás-Aguapeí Orogeny (1.28-0.95 Ga). The Aguapeí gold deposits differ in their petrography, chemistry, structural aspects and age from world classic gold deposits associated with coarse clastic sedimentary sequences (Witwatersrand, Jacobina, Tarkwa, etc.). This study discusses the main differences between Aguapeí gold deposits and the classic worldwide deposits hosted by conglomeratesGold prospects in the Aguapeí Folded Belt are situated in the southwestern portion of the Amazon Craton, within the Alto Guaporé Province, southwestern state of Mato Grosso. The mineralizations are mainly concentrated in the Pau-a-Pique Deposit (south), Lavrinha Region (central), and São Vicente Mine (north). Gold ore comprises quartz veins and disseminations in the low-grade metamorphic metassedimentary rocks from the Aguapeí Group. This stratigraphic unit was strongly deformed by the Sunsás-Aguapeí Orogeny (1.28-0.95 Ga). The Aguapeí gold deposits differ in their petrography, chemistry, structural aspects and age from world classic gold deposits associated with coarse clastic sedimentary sequences (Witwatersrand, Jacobina, Tarkwa, etc.). This study discusses the main differences between Aguapeí gold deposits and the classic worldwide deposits hosted by conglomerates

New Lithostratigraphic Unit Records an Ediacaran Glaciation in Mato Grosso State, Brazil: Serra Azul Formation

A new succession of diamictites and siltstones was found above post-Marinoan carbonates from the Araras Group in the northern Paraguay Belt (Brazil), in discontinuous outcrops. This new stratigraphic unit, named Serra Azul Formation in this work, has a variable thickness reaching up to 300 meters. The diamictites were deposited in the first 70 m and present glacial evidences, while the siltstones represent the upper part of the succession and show some sandstone layers towards the top of the succession. This glacial record is the youngest Neoproterozoic glacial event that has been found on South America and probably is related to Gaskiers Glaciation (582 Ma)

Mineralization typology and mineral chemistry of the Pb-(Zn) Ranchão deposit, internal zone of the Paraguay Belt, Mato Grosso, Brazil

Located about 50 km southeast of the city of Cuiabá, the Pb-(Zn) Ranchão deposit is hosted by Neoproterozoic meta-diamictites of the Cuiabá Group (Coxipó Formation, Mata-Mata Member), inner zone of the Paraguay Belt. The deeply deformed host rocks underwent greenschist regional metamorphism, as well as contact metamorphism as a result of the intrusion of São Vicente Granite. This work presents the geologic, petrographic, and mineral chemistry characterization of the Ranchão deposit lead-zinc ore, seeking to unravel the metallogenic processes that formed the sulfide concentrations. The mineralizations are mainly composed of galena, pyrite, and sphalerite, and occur as breccia, veins, and disseminations. The sulfides are associated with host rock hydrothermal alterations, one early, pre-mineralization (with quartz-sericita and calcite), and other late, postore phase (with calcite and chlorite). The most significant concentrations of ore minerals are structured through N60-70W and N80-85W faults, in which the ore, as breccia, is found. Chlorite geothermometry point to temperatures from 120 to 190°C for late hydrothermal fluids. The features indicate a meso to epithermal system associated with mineralization, which affected meta-diamictites previously metamorphosed by the São Vicente Granite. These results represent a perspective for exploration of similar mineralizations in Cuiabá region and other meta-sedimentary folded belts with similar features.Localizado cerca de 50 km a sudeste da cidade de Cuiabá, o depósito de Pb-(Zn) Ranchão é hospedado por metadiamictitos neoproterozoicos do Grupo Cuiabá (Formação Coxipó, Membro Mata-Mata), zona interna da Faixa Paraguai. As rochas hospedeiras encontram-se intensamente deformadas e foram submetidas a metamorfismo regional na fácies xisto verde e de contato (fácies hornblenda hornfels), resultante da intrusão do Granito São Vicente, de idade cambriana. Este trabalho apresenta a caracterização geológica, petrográfica e de química mineral das mineralizações plumbo-zincíferas do depósito Ranchão, visando compreender os processos metalogenéticos responsáveis pelas concentrações de sulfetos. As zonas mineralizadas, compostas majoritariamente de galena, pirita e esfalerita, ocorrem como brechas, veios e disseminações. Os sulfetos estão associados a alterações hidrotermais das rochas hospedeiras, uma precoce, pré-mineralização (com quartzo-sericita e calcita), e outra tardia, pós-mineralização (com calcita e clorita). As maiores concentrações de minério seguem estruturas com orientação N60-70W e N80-85W, correspondentes às zonas de falhas que contêm o minério brechado. Cálculos geotermométricos indicam temperaturas entre 120 e 190°C para os fluidos hidrotermais tardi a epigenéticos, responsáveis pela formação da clorita. Os dados obtidos do depósito apontam para uma mineralização associada a um sistema meso a epitermal, que afetou diamictitos, previamente convertidos em hornfels pelo contato com o Granito São Vicente. Esses resultados representam uma perspectiva para prospecção de mineralizações similares na Baixada Cuiabana e em outras faixas metassedimentares dobradas com características similares

Fluid inclusions study on quartz from a magmatic-hydrothermal system in the Papagaio Artisanal Mining District, Alta Floresta Gold Province, Mato Grosso state, Amazon Craton

O garimpo aurífero do Papagaio, localizado em Paranaíta, Mato Grosso, insere-se no setor noroeste da Província Aurífera de Alta Floresta, sul do Cráton Amazônico. Está hospedado em dacito porfirítico inicialmente afetado por alteração potássica, sobreposta por forte alteração sericítica pervasiva e, por fim, por alteração propilítica. O minério é representado pela paragênese pirita + calcopirita + esfalerita ± galena ± calcocita ± covelita e ocorre associado a sistemas de veios de quartzo e stockworks que truncam os setores de alteração potássica e sericítica. Estudos de inclusões fluidas dos veios mineralizados e estéreis presentes no garimpo permitiram identificar três grupos de inclusões fluidas: tipo I) inclusões aquocarbônicas; tipo II) aquosas bifásicas; tipo III) aquosas tri a multifásicas. Nos veios mineralizados houve a crepitação das inclusões do Tipo I a 325ºC. Foram encontradas temperaturas de homogeneização de 115,1 a 216,2ºC e salinidades entre 0,5 a 24,0% para as inclusões do Tipo II. Nos veios estéreis, as inclusões do Tipo II resultaram em temperaturas de homogeneização total entre 135,9 e 190,3ºC e salinidades de 26,0 a 30,2%. No Tipo III a homogeneização total ocorreu entre 323,2 e  402,9ºC com salinidade superior a 40,0%. Portanto, fluidos de elevada temperatura e salinidade com características de origem magmática tiveram um papel essencial na formação das zonas mineralizadas do garimpo. Nesse contexto, a colocação de corpos subvulcânicos teria sido essencial na gênese da mineralização aurífera do Papagaio, pois teria servido como fonte de calor, fluido e metais para a instalação de um sistema magmático-hidrotermal profundo, relacionado ao ambiente dos depósitos do tipo pórfiro e intrusion-related gold systems (IRGS).The Papagaio artisanal gold mining in Paranaíta, Mato Grosso, Brazil, is located in the northwest sector of Alta Floresta Gold Province, in the southern Amazon Craton. Mineralization is hosted in porphyritic dacite initially affected by a potassic alteration that is superimposed by a strong pervasive sericitic alteration and, finally, by propylitic alteration. The ore paragenesis consists of pyrite + chalcopyrite + sphalerite ± galena ± chalcocite ± covellite that is located in a quartz veins systems and stockworks that cuts hydrothermal potassic and sericitic alteration zones. Studies of fluid inclusions of the mineralized and barren veins present in the mining identified three groups of fluid inclusions: type I) aqueous-carbonic inclusions; type II) aqueous biphasic inclusions; type III) aqueous tri- to multiphase inclusions. In the mineralized veins, the type I inclusions decrepitated at 325ºC. Type II inclusions have homogenization temperatures of 115.1 to 216.2ºC and salinities of 0.5 to 24.0%. In the barren veins, type II inclusions yielded total homogenization temperatures between 135.9 and 190.3ºC and salinities of 26.0 to 30.2%. In type III inclusions, the total homogenization was between 323.2 and 402.9ºC with salinity greater than 40.0%. Therefore, high-temperature and high-salinity fluids with characteristics of magmatic origin had essential role in the formation of the mineralized zones of the artisanal mining. In this context, the placement of subvolcanic bodies would have been indispensable for the genesis of the gold mineralization at Papagaio. These subvolcanic bodies would have served as a source of heat, fluid, and metals for the development of a deep magmatic-hydrothermal system, possibly associated with the environment of the porphyry and intrusion-related gold systems (IRGS).