| dc.creator | De Lima Pereira Silva G. | |
| dc.creator | Xavier R.P. | |
| dc.date | 1997 | |
| dc.date | 2015-06-30T14:50:34Z | |
| dc.date | 2015-11-26T15:09:32Z | |
| dc.date | 2015-06-30T14:50:34Z | |
| dc.date | 2015-11-26T15:09:32Z | |
| dc.date.accessioned | 2018-03-28T22:19:43Z | |
| dc.date.available | 2018-03-28T22:19:43Z | |
| dc.identifier | | |
| dc.identifier | International Geology Review. , v. 39, n. 8, p. 688 - 702, 1997. | |
| dc.identifier | 206814 | |
| dc.identifier | | |
| dc.identifier | http://www.scopus.com/inward/record.url?eid=2-s2.0-0031433824&partnerID=40&md5=b6a19af4d7d9d67493ab9d1093a9f4d9 | |
| dc.identifier | http://www.repositorio.unicamp.br/handle/REPOSIP/100332 | |
| dc.identifier | http://repositorio.unicamp.br/jspui/handle/REPOSIP/100332 | |
| dc.identifier | 2-s2.0-0031433824 | |
| dc.identifier.uri | http://repositorioslatinoamericanos.uchile.cl/handle/2250/1257841 | |
| dc.description | Carbonaceous units commonly host or are closely related to lode-gold mineralization in the mesothermal Fazenda Maria Preta (FMP) and Fazenda Canto (FC) deposits of the Paleoproterozoic Rio Itapicuru greenstone belt of northeastern Brazil. In these deposits, the carbonaceous matter occurs mainly as: (1) straight to anastomosing seams (Type I) along or transecting the rock fabric, or as stylolitic structures in quartz veins; (2) single grains composed of an agglomerate of highly anisotropic subgrains (Type II); or (3) single grains with a homogeneous internal texture (Type III), which are either enclosed in Type-I carbonaceous seams or disseminated in the rock matrix. Type-I carbonaceous matter commonly hosts or is overgrown by the gold-related sulfide paragenesis, particularly arsenopyrite, whereas both Type I and Type II enclose crystals of arsenopyrite or occur as inclusions and in sharp contact with the sulfide phases. The three morphological types of carbonaceous matter exhibit similar Raman spectral characteristics, with distinct D and O peaks at wave numbers between 1351 cm-1 and 1357 cm-1, and 1585 cm-1 and 1598 cm-1, respectively. In contrast to the FMP deposit, the carbonaceous matter of the FC deposit shows D peaks of higher intensities than the O peaks. The O peaks are accompanied by an additional disorder-induced band on the high wave number side (≈1622 cm-1), and the O/D peak intensity ratios are higher and the half-height O-peak widths smaller. These spectral parameters indicate that the carbonaceous matter in both deposits corresponds to some form of microcrystalline disordered graphitic material and defines a graphitization trend from the FMP to the FC deposit. The carbonaceous matter of the FMP deposit is isotopically lighter (δ13C = -23.3‰ to -30.8‰; x = -27.4 ± 1.8‰ relative to PDB) than the carbonaceous material of the FC (δ13C = -18.5‰ to -21.0‰, x = -19.7 ± 0.9‰). These δ13C values, together with the geologic evidence, point toward a primarily biogenic organic origin for the carbonaceous matter. The marked differences in the Raman spectral parameters and the δ13C values are interpreted as resulting from different degrees of thermal maturation of carbonaceous matter attained during the regional greenschist metamorphism and granite intrusions of the Rio Itapicuru greenstone belt. The δ13C compositions of CO2 resulting from the oxidation or hydrolysis of the carbonaceous matter, calculated by applying the equilibrium CO2-graphite fractionation, fall within the range -9.7‰ to -18.8‰ at 360 to 420°C (FMP deposit) and -6.0‰ to -10.0‰ at 390 to 455°C (FC deposit). These calculated δ13C values are lower than those obtained from primary fluid-inclusion CO2 in gold-bearing veins (-6.0‰ to -10.2‰ for the FMP deposit; -2.8‰ to -4.9‰ for the FC deposit) and imply that the thermal maturation process of the carbonaceous matter contributed little to changes in the chemistry and isotopic composition of the ore fluid. The presence of the carbonaceous matter may have been an important factor in gold deposition during fluid-carbon interaction, acting: (1) as a chemical trap, by reducing the f(O2) of the ore fluids or enhancing fluid immiscibility by adding small quantities of CH4 and N2 to the fluid phase; and/or (2) as a physical barrier, by adsorbing gold on its surface as activated carbon. Copyright © 1997 by V. H. Winston & Son, Inc. All rights reserved. | |
| dc.description | 39 | |
| dc.description | 8 | |
| dc.description | 688 | |
| dc.description | 702 | |
| dc.description | Alves Da Silva, F.C., Chauvet, A., Faure, M., Early Proterozoic orogeny (Transamazonian) and syntectonic granite emplacement in the Rio Itapicuru greenstone belt, Bahia, Brazil (1993) Comptes Rendus Acad. Sci. Paris, 316, pp. 1139-1146 | |
| dc.description | Beny-Bassez, C., Rouzaud, J.N., Characterization of carbonaceous materials by correlated electron and optical microscopy and Raman microspectroscopy (1985) Scan. Elec. Micros., (1), pp. 119-132. , 1985 | |
| dc.description | Childress, J.J., Hydrothermal vents - A case study of the biology and chemistry of a deep-sea hydrothermal vent of the Galapagos Rift: The Rose Garden in 1985 (1988) Deep-Sea Res., 35, pp. 1677-1849 | |
| dc.description | Cuesta, A., Dhamelincourt, P., Laureyns, J., Martinez-Alonso, A., Tascón, J.M.D., Raman microprobe studies on carbon materials (1994) Carbon, 32, pp. 1523-1532 | |
| dc.description | Demaison, G.J., Moore, G.T., Anoxic environments and oil bed genesis (1980) Amer. Assoc. Petrol. Geol. Bull., 6 (4), pp. 1179-1209 | |
| dc.description | Dissanayake, C.B., Rupasinghe, M.S., Gold-graphite association in granulite terrains - Implications for ore genesis (1991) Chem. Geol., 97, pp. 265-272 | |
| dc.description | Etter, D.C., Bjorlykke, A., Andersen, T., A fluid-inclusion and stable-isotope study of the Proterozoic Bidjovagge Au-Cu deposit, Finnmark, northern Norway (1994) Mineral. Deposita, 29, pp. 16-29 | |
| dc.description | Friedman, I., O'Neil, J.R., Compilation of stable isotope fractionation factors of geochemical interest (1977) Data of Geochemistry, 6th Ed., pp. KK1-KK12. , Fleischer, M., ed., Washington, DC, U.S. Geol. Surv. Prof. Paper 440-K | |
| dc.description | Galimov, E.M., Kodina, L.A., Bogacheva, M.P., Vlasova, L.N., Nature of the organic matter in hydrothermal sulfide ores and sediments in the Kebrit Basin, Red Sea (1996) Geochem. Int., 33, pp. 124-138 | |
| dc.description | Gatelier, J.P., Disnar, J.R., Organic matter and gold-ore association in hydrothermal deposits, France (1989) Appl. Geoch., 4, pp. 143-149 | |
| dc.description | Gorzhevskiy, D.I., On the role of organic matter in ore formation (1987) Int. Geol. Rev., 29, pp. 207-217 | |
| dc.description | Grassle, J.F., Hydrothermal vent animals: Distribution and biology (1985) Science, 229, pp. 713-717 | |
| dc.description | Groves, D.I., The crustal continuum model for late-Archaean lode-gold deposits of the Yilgarn Block, Western Australia (1993) Mineral. Deposita, 28, pp. 366-374 | |
| dc.description | Kishida, A., (1979) Caracterização Geológica e Geoquímica das Seqüências Vulcanossedimentares do Médio Rio Itapicuru, Bahia, 98p. , Unpubl. master's dissertation, Universidade Federal da Bahia, Salvador | |
| dc.description | Kishida, A., Riccio, L., Chemostratigraphy of lava sequence from the Rio Itapicuru greenstone belt, Bahia, Brazil (1980) Precamb. Res., 11, pp. 161-178 | |
| dc.description | MacDougall, G.J., Hancock, R.D., Gold complexes and activated carbon. A literature review (1981) Gold Bull., 14, pp. 138-153 | |
| dc.description | McKirdy, D.M., Powell, T.G., Metamorphic alteration of carbon isotopic composition in ancient sedimentary organic matter: New evidence from Australia and South America (1974) Geology, 2, pp. 591-595 | |
| dc.description | Mossman, D.J., Nagy, B., Davis, D.W., Hydrothermal alteration of organic matter in uranium ores, Elliot Lake, Canada: Implications for selected organic-rich deposits (1993) Geochim. et Cosmochim. Acta, 57, pp. 3251-3259 | |
| dc.description | Naden, J., Shepherd, T.J., Role of methane and carbon dioxide in gold deposition (1989) Nature, 342, pp. 793-795 | |
| dc.description | Nemanich, R.J., Solin, S.A., First- and second-order Raman scattering from finite-size crystals of graphite (1979) Phys. Rev., B20, pp. 392-401 | |
| dc.description | Oliveira, E.A.S., Soares, A.S.B., Santana, W.R., Fazenda Maria Preta gold deposits (1991) Brazil Gold '91: Field and Mine Trip to Gold Mineralizations of Northeastern Bahia, Brazil, pp. 35-41. , Fleischer, R., Sad, J. H. G., Fuzikawa, K., and Ladeira, E. A., eds., Belo Horizonte, Dept. Nac. Prod. Mineral | |
| dc.description | Parnell, J., Kucha, H., Landais, P., (1994) Bitumens in Ore Deposits, 600p. , Berlin, Springer Verlag, Soc. Geol. Appl. Min. Dep., Spec. Publ. no. 9 | |
| dc.description | Pasteris, J.D., Wopenka, B., Raman spectra of graphite as indicators of degree of metamorphism (1991) Can. Mineral., 29, pp. 1-9 | |
| dc.description | Rocha Neto, M.B., Geologia e recursos minerais do gréenstone belt do Rio Itapicuru, Bahia (1994) Série Arquivos Abertos 4, 32p. , Pedreira, A. J., ed., Salvador, Companhia Baiana de Pesquisa Mineral | |
| dc.description | Schidlowski, M., A 3,800-million-year isotopic record of life from carbon in sedimentary rocks (1988) Nature, 333, pp. 313-318 | |
| dc.description | Silva, M.G., A seqüência vulcanossedimentar do médio Rio Itapicuru, Bahia (1984) Geologia e Recursos Minerais do Estado da Bahia. Textos Básicos, 5, pp. 7-42. , Sá, P. V. S. V., and Duarte, F. B., eds., Salvador, Secretaria de Minas e Energia/Companhia de Produção Mineral | |
| dc.description | (1987) Geochemie, Petrologie und Tektonische Enturickleung Eines Proterozoischen Grunsteingurtels: Rio Itapicuru, Bahia, Brasilien, 141p. , Unpubl. Ph.D. thesis, University of Freiburg, Germany | |
| dc.description | Springer, J.S., Carbon in Archean rocks of the Abitibi belt (Ontario-Quebec) and its relation to gold distribution (1985) Can. Jour. Earth Sci., 22, pp. 1945-1951 | |
| dc.description | Taylor, G.H., Carbonaceous matter: A guide to the genesis and history of ores (1971) Soc. Mining Geol. Japan, Spec. Iss., 3, pp. 283-288 | |
| dc.description | Teixeira, J.B.G., Kishida, A., Marimon, M.P.C., Xavier, R.P., McReath, I., The Fazenda Brasileiro gold deposit, Bahia: Geology, hydrothermal alteration, and fluid inclusion studies (1990) Econ. Geol., 85, pp. 990-1009 | |
| dc.description | Valley, J.W., O'Neill, J.R., 13C/12C exchange between calcite and graphite: A possible thermometer in Grenville marbles (1981) Geochim. et Cosmochim. Acta, 45, pp. 411-419 | |
| dc.description | Wilson, G.C., Rucklidge, J.C., Mineralogy and microstructures of carbonaceous gold ores (1987) Mineral. Petrol., 36, pp. 219-239 | |
| dc.description | Wopenka, B., Pasteris, J.D., Structural characterization of kerogen to granulite-facies graphite: Applicability of Raman microprobe spectroscopy (1993) Amer. Mineral., 78, pp. 533-557 | |
| dc.description | Xavier, R.P., (1991) The Role of Microstructural and Fluid Processes in the Genesis of Gold-bearing Shear Zones: Fazenda Maria Preta Mine, Rio Itapicuru Greenstone Belt, Bahia, Brasil, 241p. , Unpubl. Ph.D. thesis, University of Southampton | |
| dc.description | Xavier, R.P., Foster, R.P., The role of carbonaceous shear bands in fluid flow and gold precipitation in the Fazenda Maria Preta mine, Bahia, northeast Brazil (1991) Gold '91: The Economics, Geology, Geochemistry, and Genesis of Gold Deposits, pp. 269-277. , Ladeira, E. A., ed., Rotterdam, Balkema | |
| dc.description | Xavier, R.P., Foster, R.P., Fallick, A.E., Alderton, D.H., Potential fluid reservoirs for mesothermal gold deposits in the Rio Itapicuru greenstone belt, Bahia, Brazil (1994) Comunicaciones, 45, pp. 13-22 | |
| dc.description | Yui, T.F., Huang, E., Xu, J., Raman spectrum of carbonaceous material: A possible metamorphic grade indicator for low-grade metamorphic rocks (1996) Jour. Metamor. Geol., 14, pp. 115-124 | |
| dc.description | Zimmerle, W., New aspects on the formation of hydrocarbon source rocks (1985) Geol. Rundsch., 74, pp. 385-416 | |
| dc.language | en | |
| dc.publisher | | |
| dc.relation | International Geology Review | |
| dc.rights | fechado | |
| dc.source | Scopus | |
| dc.title | The Gold-carbonaceous Matter Association In Lode Deposits Of The Rio Itapicuru Greenstone Belt, Northeastern Brazil | |
| dc.type | Artículos de revistas | |
