Bulletin Mineralogie Petrologie

Dolníček Zdeněk, Nepejchal Miroslav, Kapusta Jaroslav, Ulmanová Jana, Fojt Bohuslav

Ročník 26, číslo 1 (2018), strana 12-27

orogenic gold deposits, shear zone, gold, electrum, chlorite, delessite, monazite, xenotime, Staré Město Crystalline Complex

Placers after extensive old mining of alluvial gold occur in the Andělské údolí Valley near Staré Město pod Sněžníkem. However, nothing is known about primary gold mineralization in this area. New detailed investigation resulted in the discovery of three types of primary gold mineralization hosted by an up to 5 m thick NE-SW trending shear zone cutting mica schists and gneisses of the Staré Město Unit. The first type of Au mineralization is represented by small pyrite-rich lenses enclosed in mylonite. These lenses are dominated by Au-As-bearing pyrite containing also inclusions of galena, chalcopyrite, sphalerite and tetrahedrite, with ore minerals hosted by fine-grained matrix composed of muscovite, quartz and chamosite. The second type of Au mineralization is large quartz “blasts” hosted by mylonite. Small grains of As-bearing pyrite and arsenopyrite (both containing Au) are enclosed sporadically in quartz “blasts”. The third (and youngest) type of gold mineralization is tiny steep NW-SE trending chlorite-dominated veinlets containing also native gold, xenotime and monazite. Gold sheets reaching up to 0.5 mm in size belong to electrum (fineness ranges between 663 and 830 w/w, i.e. 51.7 to 72.8 at. % Au, which is comparable to composition of alluvial gold). The composition of both chlorite (delessite) and alteration phyllosilicates in wall rock adjacent to chlorite veinlets (illite-smectite) are anomalous when compared with typical orogenic vein gold mineralizations, probably due to low temperatures of precipitation (probably below ca. 200 °C). We interpret small lenses of Au-bearing pyrite mineralization as well as Au-bearing quartz “blasts” to be the boudins of earlier mineralizations, which were incorporated into the mylonite during tectonic evolution of the host shear zone. The gold-bearing chlorite veinlets are considered to be the product of remobilization of gold from both older mineralizations, which took place during late evolution of the host shear zone. With respect to spatially very restricted occurrence of gold mineralization, we do not presuppose some significant fluid-mediated transport of gold from a deep source. All three newly recognized types of Au mineralization have not been reported in the wider area yet.

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Bayliss P (1975) Nomenclature of the trioctahedral chlorites. Can Mineral 13: 178-185

Buhl G (1938) Die Geschichte des Bergbaues im Mährisch-Altstädter Bezirk. Bergland-Bezirksbücher, Bd. 3. Hohenstadt

Buchholz P, Oberthür T, Lüders V, Wilkinson J (2007) Multistage Au-As-Sb mineralization and crustal-scale fluid evolution in the Kwekwe District, Midlands Greenstone Belt, Zimbabwe: a combined geochemical, mineralogical, stable isotope, and fluid inclusion study. Econ Geol 102: 347-378

Cathelineau M (1988) Cation site occupancy in chlorites and illites as a function of temperature. Clay Miner 23: 471-485

Crispini L, Federico L, Capponi G, Talarico F (2011) The Dorn gold deposit in northern Victoria Land, Antarctica: Structure, hydrothermal alteration, and implications for the Gondwana Pacific margin. Gondw Res 19: 128-140

Deer WA, Howie RA, Zussman J (1962) Rock-forming minerals. Vol. 3: sheet silicates. John Wiley. New York

Demange M, Pascal M-L, Raimbault L, Armand J, Forette MC, Serment R, Touil A (2006) The Salsigne Au-As-Bi-Ag-Cu deposit, France. Econ Geol 101: 199-234

Dora ML, Randive KR (2015) Chloritisation along the Thanewasna shear zone,Western Bastar Craton, Central India: Its genetic linkage to Cu-Au mineralisation. Ore Geol Rev 70: 151-172

Fojt B, Čuluunbaatar N, Hladíková J, Kopa D (1992) Paragenetická studie rudního výskytu u Starého Města pod Sněžníkem. Čas Slez Muzea (A) 41: 239-257

Fojt B, Dolníček Z, Hoffman V, Škoda R, Trdlička Z, Zeman J (2007) Paragenetická charakteristika ložisek Zn-Pb rud v širším okolí Horního Města u Rýmařova (Nízký Jeseník). Acta Mus Moraviae, Sci geol 92: 3-57

Fojt B, Hladíková J, Kalenda F (2001) Zlaté Hory ve Slezsku, největší rudní revír v Jeseníkách. Část 2. Acta Mus Moraviae, Sci geol 86: 3-51

Fuertes-Fuente M, Cepedal A, Lima A, Dória A, dos Anjos Ribeiro M, Guedes A (2016) The Au-bearing vein system of the Limarinho deposit (northern Portugal): Genetic constraints from Bi-chalcogenides and Bi-Pb-Ag sulfosalts, fluid inclusions and stable isotopes. Ore Geol Rev 72: 213-231

Groves DI, Goldfarb RJ, Gebre-Mariam M, Hagemann SG, Robert F (1998) Orogenic gold deposits: A proposed classification in the context of their crustal distribution and relationship to other gold deposit types. Ore Geol Rev 13: 7-27

Hagemann SG, Brown PE (1996) Geobarometry in Archean lode-gold deposits. Eur J Mineral 8: 937-960

Hanke R (1942) Bergbau im Landkreis Mähr.-Schönberg. - Teẞtal. Mitteilungen für Heimatkunde im Landkreis M.-Schönberg. Beilage zum „Nordmähr. Grenzboten“, M. Schönberg. 3: 4

Jowett EC (1991) Fitting iron and magnesium into the hydrothermal chlorite geothermometer. GAC/MAC/SEG Joint Annual Meeting (Toronto, May 27-29, 1991), Program with Abstracts 16: A62. Toronto

Klein EL, Harris C, Giret A, Moura CAV (2007) The Cipoeiro gold deposit, Gurupi Belt, Brazil: Geology, chlorite geochemistry, and stable isotope study. J South Amer Earth Sci 23: 242-255

Klein EL, Ribeiro JWA, Harris C, Moura CAV, Giret A (2008) Geology and fluid characteristics of the Mina Velha and Mandiocal orebodies and implications for the genesis of the orogenic Chega Tudo gold deposit, Gurupi Belt, Brazil. Econ Geol 103: 957-980

Malec J, Kavalír J, Jansa J (1990) Zlato a doprovodné minerály z oblasti Jeseníků. MS, Ústav nerostných surovin, Kutná Hora

Maydagán L, Franchini M, Impiccini A, Lentz D (2016) Phyllosilicates geochemistry and distribution in the Altar porphyry Cu-(Au) deposit, Andes Cordillera of San Juan, Argentina: Applications in exploration, geothermometry, and geometallurgy. J Geoch Explor 167: 83-109

Melka K (1965) Návrh na klasifikaci chloritových minerálů. Věst Ústř Úst Geol 40: 23-27

Moura MA, Botelho NF, Olivo GM, Kyser TK (2006) Granite-related Paleoproterozoic, Serrinha gold deposit, southern Amazonia, Brazil: hydrothermal alteration, fluid inclusion and stable isotope constraints on genesis and evolution. Econ Geol 101: 585-605

Műcke A, Fojt B, Skácel J (2006) The Malé Vrbno magnetite occurrence of the Velké Vrbno Unit, Czech Republic: petrology, mineralogy, geochemistry and genesis. Chem Erde Geochem 66: 109-128

Murzin VV, Varlamov DA, Palyanova GA (2017) Conditions of formation of gold-bearing magnetite-chlorite-carbonate rocks of the Karabash ultrabasic massif (South Urals). Russ Geol Geophys 58: 803-814

Nepejchal M, Dolníček Z, Fojt B (2017) Výskyt zlata v regionu Starého Města pod Sněžníkem (Česká republika). Bull Mineral Petrolog 25: 33-42

Pecina V, Aichler J, Adamová M, Buriánková K, Čurda J, Hanžl P, Holásek O, Hrouda F, Chlupáčová M, Krejčí Z, Kočandrle J, Manová M, Nekovařík Č, Opletal M, Šalanský K, Večeřa J, Žáček V (2000) Vysvětlivky k základní geologické mapě. - ČGÚ Praha

Pouchou J, Pichoir F (1985) „PAP“ j(rz) procedure for improved quantitative microanalysis. In: Armstrong JT (ed): Microbeam Analysis. 104-106. San Francisco Press. San Francisco.

Reyes AG (1990) Petrology of Philippine geothermal systems and the application of alteration mineralogy to their assessment. J Volcanol Geotherm Res 43: 279-309

Rieder M, Cavazzini G, D´yakonov YS, Kamenetskii VAF, Gottardi G, Guggenheim S, Koval´ PV, Mueller G, Neiva AMR, Radoslovich EW, Robert JL, Sassi FP, Takeda H, Weiss Z, Wones DR (1998) Nomenclature of micas. Canad Mineral 36: 905-912

de Siqueira Corrêa R, Oliveira CG, Vidotti RM, da Silva Souza V (2015) Regional-scale pressure shadow-controlled mineralization in the Príncipe Orogenic Gold Deposit, Central Brazil. Ore Geol Rev 71: 273-304

Skácel J (1988) Rudné hornictví v okolí Starého Města. Sev Morava 55: 47-51

Skácel J (2008) K problému původu zlata ve starých rýžoviskách v Rychlebských horách a na Staroměstsku. Čas Slez Muz (A) 57: 179-184

Skácel J, Pecina V (1990) Staré báňské práce na drahé a barevné kovy u Starého Města p. Sněžníkem. Čas Mineral Geol 35: 203-208

Steiner A (1968) Clay minerals in hydrothermally altered rocks at Wairakei, New Zealand. Clays Clay Miner 16: 193-213

Zachariáš J, Novák T (2009) Gold-bearing quartz veins of the Bělčice ore district, Bohemian Massif: evidence for incursion of metamorphic fluids into a granodiorite body and for isothermal mixing between two types of metamorphic fluids. J Geosci 54: 57-72

Zhu Y, An F, Tan J (2011) Geochemistry of hydrothermal gold deposits: A review. Geosci Front 2: 367-374

Zoheir BA (2012) Controls on lode gold mineralization, Romite deposit, South Eastern Desert, Egypt. Geosci Front 3: 571-585

Zoheir BA, Akawy A (2010) Genesis of the Abu Marawat gold deposit, central Eastern Desert of Egypt. J Afr Earth Sci 57: 306-320

Zoheir BA, El-Shazly AK, Helba H, Khalil KI, Bodnar RJ (2008) Origin and evolution of the Um Egat and Dungash orogenic gold deposits, Egyptian Eastern Desert: evidence from fluid inclusions in quartz. Econ Geol 103: 405-424