Triassic fluid mobilization and epigenetic lead-zinc sulphide mineralization in the Transdanubian Shear Zone (Pannonian Basin, Hungary)

An assemblage of alunite-supergroup minerals (ASM), rhabdophane-group minerals (RGM), goethite and associated clay minerals occurs in Permian A-type porphyritic microgranite in the eastern part of the Velence Hills, Hungary. The secondary sulfates/phosphates include jarosite, Pb-rich jarosite and alunite, corkite, hinsdalite and rhabdophane-(Ce), -(La) and -(Nd). Detailed electron probe microanalysis and Raman spectroscopy reveal a wide miscibility among RGM end-members and show a rhabdophane–tristramite–brockite solid solution with extensive compositional variation. Moreover, ASM show heterogeneous composition and complex substitution mechanisms within the alunite, beudantite and plumbogummite groups. The formation of this rare mineral assemblage reveals extensive remobilization of rare-earth elements (REE), Th, U, P, S, Fe and Pb under supergene conditions. Compositional variations and substitution trends of the RGM investigated indicate that Th, U, Ca and Pb are incorporated into the rhabdophane structure by a (Ca, Pb)2+ + (Th, U)4+ ↔ 2REE3+ substitution mechanism. Consequently, we suggest the following end-member formulae for RGM containing divalent and tetravalent cations: (Ca0.5Th0.5)PO4·H2O for brockite, (Pb0.5Th0.5)PO4·H2O for grayite and (Ca0.5U0.5)PO4·2H2O for tristramite. The ASM and RGM originated from total leaching of the primary magmatic REE, Th, U and P minerals in the microgranite [most probably allanite-(Ce), fluorapatite and possibly also xenotime-(Y)], together with input of Pb and S in low-temperature, acid sulfate solutions, connected with an adjacent Palaeogene andesite–diorite intrusion and the accompanying hydrothermal sulfide mineralization.

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“…Simplified geological map of the Velence Hills area modified after Horváth et al (2004) and Benkó et al (2010, 2014). …”

Section: Regional Geologymentioning

confidence: 99%

Minerals of the rhabdophane group and the alunite supergroup in microgranite: products of low-temperature alteration in a highly acidic environment from the Velence Hills, Hungary

et al. 2018

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“…For comparison purposes, fluid inclusion data for two Alpine-type epigenetic lead-zinc deposits in the Drau Range (Bleiberg, Mežica) [39], the Pb-Zn-fluorite mineralization of the Velence Mts. [6], and the primary fluid inclusions from Pécsely (green dots) are also shown. Fluid inclusions from Pécsely plot within the MVT field and overlap with data from Mežica, Bleiberg, and Velence Mts.…”

Section: Formation Conditions Of the Fluorite Veinsmentioning

confidence: 99%

“…Therefore, it is plausible to estimate that the hydrothermal fluids responsible for the fluorite mineralization were also interacting with those uranium rich zones and were enriched in hydrogen. However, a model favoring local conditions would be more acceptable regarding the origin of the gas content of the inclusions because fluid inclusions with similar gas content were not described from the Pb-Zn deposits along the PABL (see e.g., [6]). Fluorite and the host rocks at Pécsely have elevated uranium content; therefore, the presence of hydrogen in fluid inclusions could more probably be related to the in situ (within inclusion) radiolysis of water.…”

Section: The Origin Of H 2 In Fluid Inclusions Of Fluoritementioning

confidence: 99%

“…The phosphorite-bearing sedimentary horizons are cut by epigenetic fluorite veins. Fluorite and fluorite-base metal vein systems with economic significance in the past also occur in other parts of the Transdanubian terrain [6]. Therefore, the occurrence of the fluorite veins at Pécsely may have significance in a regional metallogenetic context.…”

Section: Introductionmentioning

confidence: 99%

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Epigenetic-Hydrothermal Fluorite Veins in a Phosphorite Deposit from Balaton Highland (Pannonian Basin, Hungary): Signatures of a Regional Fluid Flow System in an Alpine Triassic Platform

et al. 2021

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The middle Anisian extensional tectonics of the Neotethyan realm developed a small, isolated carbonate platform in the middle part of the Balaton Highland (western Hungary), resulted in the deposition of uranium-bearing seamount phosphorite on the top of the drowned platform and produced some epigenetic fluorite veins in the Middle Triassic sequence. The stable C-O isotope data of carbonates are shifted from the typical Triassic carbonate ranges, confirming the epigenetic-hydrothermal origin of veining. Primary fluid inclusions in fluorite indicate that these veins were formed from low temperature (85–169 °C) and high salinity NaCl + CaCl2 + H2O type (apparent total salinity: 15.91–22.46 NaCl wt%) hydrothermal fluids, similar to parent fluids of the Alpine-type Pb-Zn deposits. These findings indicate that the Triassic regional fluid circulation systems in the Alpine platform carbonates also affected the area of the Balaton Highland. This is also in agreement with the previously established palinspatic tectonic reconstructions indicating that the Triassic carbonate and basement units in the Balaton Highland area were a part of the Southern Alpine. Similar fluorite veining in phosphorite deposits is also known in the Southern Alpine areas (e.g., Monte San Giorgi, Italy). Raman spectroscopic analyses detected H2 gas in the vapor phase of the fluid inclusions and a defect-rich fluorite structure in violet to black colored growth zones. This unique phenomenon is assumed to be the result of interaction between the uranium-rich phosphorite and the parent fluids of the epigenetic fluorite veins.

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“…The mineralizations on the southern edge of the Thuringian Basin bear a number of similar features to numerous deposits and occurrences throughout post-Variscan Europe, such as deposits in France (Charef & Sheppard 1988;Munoz et al 1994Munoz et al , 2005McGaig et al 2000), Spain (Halliday and Mitchell 1984;Wickham & Taylor 1990;Canals and Cardellach 1993;Galindo et al 1994;Subías and Fernández-Nieto 1995;Johnson et al 1996;Crespo et al 2002;Piqué et al 2008), Sardinia (Muchez et al 2005;Boni et al 2009), Germany (Behr & Gerler 1987;Mertz et al 1989;Boness et al 1990;Lüders & Möller 1992;Meinel 1993;Hähnel et al 1995;Krahn & Baumann 1996;Meyer et al 2000;Zeh & Thomson 2000;Wagner & Lorenz 2002;Schwinn et al 2006;Baatartsogt et al 2007;Staude et al 2007Staude et al , 2011Wagner et al 2010), Poland (Leach et al 1996;Heijlen et al 2003;Schmidt-Mumm & Wolfgramm 2004), Slovakia (Hurai et al 2002(Hurai et al , 2008, Belgium (Slobodnik et al 1994), Hungary (Benkó et al 2014), Czech Republic (Kučera et al 2010), England …”

Section: Introductionmentioning

confidence: 99%

Fluid evolution and mineralogy of Mn-Fe-barite-fluorite mineralizations at the contact of the Thuringian Basin, Thüringer Wald and Thüringer Schiefergebirge in Germany

Majzlan¹,

Brey-Funke²,

Malz³

et al. 2016

Geologica Carpathica

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Numerous small deposits and occurrences of Mn-Fe-fluorite-barite mineralization have developed at the contact of the Thuringian Basin, Thüringer Wald and Thüringer Schiefergebirge in central Germany. The studied mineralizations comprise the assemblages siderite+ankerite-calcite-fluorite-barite and hematite-Mn oxides-calcite-barite, with the precipitation sequence in that order within each assemblage. A structural geological analysis places the origin of the barite veins between the Middle Jurassic and Early Cretaceous. Primary fluid inclusions contain water vapour and an aqueous phase with NaCl and CaCl 2 as the main solutes, with salinities mostly between 24-27 mass. % CaCl 2 eq. T h measurements range between 85 °C and 160 °C in barite, between 139 °C and 163 °C in siderite, and between 80 °C and 130 °C in fluorite and calcite. Stable isotopes (S, O) point to the evaporitic source of sulphur in the observed mineralizations. The S,C,O isotopic compositions suggest that barite and calcite could not have precipitated from the same fluid. The isotopic composition of the fluid that precipitated barite is close to the sea water in the entire PermoMesozoic time span whereas calcite is isotopically distinctly heavier, as if the fluids were affected by evaporation. The fluid evolution in the siliciclastic/volcanic Rotliegend sediments (as determined by a number of earlier petrological and geochemical studies) can be correlated with the deposition sequence of the ore minerals. In particular, the bleaching of the sediments by reduced Rotliegend fluids (basinal brines) could be the event that mobilized Fe and Mn. These elements were deposited as siderite+ankerite within the Zechstein carbonate rocks and as hematite+Mn oxides within the oxidizing environment of the Permian volcanic and volcanoclastic rocks. A Middle-Jurassic illitization event delivered Ca, Na, Ba, and Pb from the feldspars into the basinal brines. Of these elements, Ba was deposited as massive barite veins.

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Triassic fluid mobilization and epigenetic lead-zinc sulphide mineralization in the Transdanubian Shear Zone (Pannonian Basin, Hungary)

Cited by 6 publications

References 46 publications

Minerals of the rhabdophane group and the alunite supergroup in microgranite: products of low-temperature alteration in a highly acidic environment from the Velence Hills, Hungary

Minerals of the rhabdophane group and the alunite supergroup in microgranite: products of low-temperature alteration in a highly acidic environment from the Velence Hills, Hungary

Epigenetic-Hydrothermal Fluorite Veins in a Phosphorite Deposit from Balaton Highland (Pannonian Basin, Hungary): Signatures of a Regional Fluid Flow System in an Alpine Triassic Platform

Fluid evolution and mineralogy of Mn-Fe-barite-fluorite mineralizations at the contact of the Thuringian Basin, Thüringer Wald and Thüringer Schiefergebirge in Germany

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