Caracteriza????o metalog??nica da Jazida Aur??fera Satinoco, Concei????o do Par??/MG

Autor: Riveros, Andr??s Hernando Z??rate
Přispěvatelé: David, Marta Edith Vel??squez, Salazar, Carlos Alejandro, Nascimento, Rielva Solimairy Campelo do, Xavier, Roberto Perez
Jazyk: portugalština
Rok vydání: 2014
Předmět:
Zdroj: Biblioteca Digital de Teses e Dissertações da UFAM
Universidade Federal do Amazonas (UFAM)
instacron:UFAM
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No. of bitstreams: 1 Disserta????o - Andr??s H Z Riveros.pdf: 7865960 bytes, checksum: 0f87630d48c333d2901830046a8e84e1 (MD5) Previous issue date: 2014-10-07 CNPq - Conselho Nacional de Desenvolvimento Cient??fico e Tecnol??gico In the Pitangui region, extreme NW in the Quadril??tero Ferr??fero-MG, meta-volcano-sedimentary rocks outcrop, characteristics of a greenstone belt sequence type contained in the Group Nova Lima (Rio das Velhas Supergroup), which host the auriferous deposit Satinoco. Conventional petrographic and SEM analysis, of the host rock, of hydrothermal alteration zones, and of mineralized rock as well as specific chemical analysis in pyroxene, garnet, amphibole, feldspar, chlorite and sulphides were performed to characterize the metallogenic evolution of the mineralizing processes in Satinoco and determine the equilibrium conditions during prograde metamorphism, of the metamorphic peak and retro-metamorphism. The metamorphic peak paragenesis is marked by mineral associations almandine ?? biotite ?? hornblende ?? grunerita-cummingtonite, hornblende ?? plagioclase and by pyroxene recrystallization. The mineral association combined with mineral chemistry revealed evidence of metamorphism in conditions of facies amphibolite with temperature of 663 oC to 717 oC (geothermometer plagioclase - amphibole), as well as pressure on roughly 9 Kbares (Al-Amphibole). The tectonometamorphic events may have occurred during the Neo-Archean to the Proterozoic generating two dominant Sn foliation and Sn+1 of crenulation and transpressive transcurrent structures activation. To these structures, hydrothermal processes and polymetallic mining of orogenic type were linked which generated deposition the auriferous ore of Satinoco. The ore mineral is docked as discontinuous bodies arranged in transpressive shear zone with orientation of 306??-315??/45??-60??E. The mineralization in Satinoco is arranged stratigraphically within the basal sequences of the Nova Lima Group, structurally controlled in the direction NW-SE, hosted on metapiroxenite at the base and mica-amphibole schist at the top, and associated with areas of hydrothermal alteration. Minerals derived from fluid - host rocks interactions were associated with processes of silicification, sulfidation, chloritization, epidotization, carbonation, sericitization, and uralitization. Such effects are spatially distributed according to the shear zone deformation. The auriferous ore geneses is related to two pulses of mineralizing fluids: i) sulphides of Fe, As, Cu, Zn, Pb, and ii) a second generation of sulfides of Fe, As, Au, Cu. According to the chlorite composition characteristics, it was formed in a temperature between 390 oC and 457 oC. These temperatures would be indicative of chemical equilibrium conditions during retrograde metamorphism that reached greenschist facies metamorphic, and of the conditions under which acted hydrothermal processes derived from the fluids percolation during ore genesis, reaching greenschist metamorphic facies. We postulate that the auriferous deposit in Satinoco has metallogenetic features of epigenetic type, similar to the deposits of orogenic gold type, comparable to the metallogenetic features of other exploited deposits in the Quadril??tero Ferr??fero, which are considered largest deposits. Na regi??o de Pitangui extremo NW do Quadril??tero Ferr??fero (MG), afloram rochas metavulcanossedimentares, caracter??sticas de uma sequ??ncia tipo greenstone belt contidas no Grupo Nova Lima (Supergrupo Rio das Velhas), as quais hospedam a jazida aur??fera Satinoco. An??lises de petrografia convencional e MEV, da rocha encaixante, de zonas de altera????o hidrotermal, da rocha mineralizada, assim como, an??lises qu??micas pontuais em pirox??nio, granada, anfib??lios, feldspatos, clorita e sulfetos foram realizadas para caracterizar a evolu????o metalogen??tica dos processos mineralizantes em Satinoco e determinar as condi????es de equil??brio durante o pico metam??rfico e do retrometamorfismo. A parag??nese do pico metam??rfico est?? marcada pelas associa????es minerais almandina ?? biotita ?? grunerita-cummingtonita ?? hornblenda, hornblenda ?? plagiocl??sio. A associa????o mineral revelou evid??ncias de metamorfismo em condi????es de f??cies anfibolito, com temperatura do pico metam??rfico de 663 oC at?? 717oC (Geoterm??metro plagiocl??sio ??? anfib??lio) e press??o em aproximadamente 9 Kbares (Al-Anfib??lio). Eventos tectonometam??rficos geraram duas folia????es: Sn dominante e Sn+1 de crenula????o e ativa????o de estruturas transcorrentes transpressivas. A estas estruturas, foram vinculados processos hidrotermais e de minera????o polimet??lica de tipo orogen??tico que gerou a deposi????o do min??rio aur??fero Satinoco. O min??rio forma corpos descont??nuos dispostos em zona de cisalhamento transpressiva com atitude 306??-315?? / 45??-60??NE. A mineraliza????o em Satinoco se disp??e estratigraficamente dentro das sequ??ncias basais do Grupo Nova Lima, estruturalmente controlada na dire????o NW-SE, hospedado em metam??ficas-ultram??ficas na base e mica-anfib??lio xisto no topo, e associada a zonas de altera????o hidrotermal. Minerais derivados da intera????o fluido - rocha encaixante foram associados a processos de silicifica????o, sulfeta????o e cloritiza????o, epidotiza????o, carbonata????o, sericitiza????o e uralitiza????o. Tais efeitos se distribuem espacialmente paralelos ?? deforma????o vinculada ?? zona de cisalhamento. A g??nese do min??rio aur??fero se relaciona a dois pulsos de fluidos mineralizantes: i) sulfetos de Fe, As, Cu, Zn, Pb, e ii) uma segunda gera????o de sulfetos de Fe, As, Au, Cu. Segundo as caracter??sticas de composi????o da clorita, est?? se formou em temperatura variando entre 390 oC e 457 oC. Estas temperaturas seriam indicativas das condi????es de equil??brio qu??mico durante o metamorfismo retr??grado que atingiu a f??cies metam??rfica xisto verde, e das condi????es nas que atuaram os processos hidrotermais derivados da percola????o de fluidos durante a g??nese do min??rio. Postulamos que a jazida aur??fera em Satinoco tem caracter??sticas metalogen??ticas de tipo epigen??tica, similares ??s dos dep??sitos tipo orogenic gold, compar??veis ??s fei????es metalogen??ticas de outros dep??sitos explorados no Quadril??tero Ferr??fero, de grande porte.
Databáze: OpenAIRE
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