Mineralogy and genesis of the Pb-Zn-Sb-Ag vein H32A in the Příbram uranium (Czech Republic)

database, nuove specie, discrediti,
ridefinizioni, classificazioni, ecc.
Avatar utente
Marco E. Ciriotti
Messaggi: 31582
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy

Mineralogy and genesis of the Pb-Zn-Sb-Ag vein H32A in the Příbram uranium (Czech Republic)

Messaggio da Marco E. Ciriotti » dom 24 set, 2023 9:16

Prossima pubblicazione.

▪ Dolníček, Z., Ulmanová, J., Sejkora, J., Knížek, F., , Škácha, P. (2023): Mineralogy and genesis of the Pb-Zn-Sb-Ag vein H32A in the Příbram uranium and base-metal district, Bohemian Massif, Czech Republic. Ore Geology Reviews, 162, (in press).

A detailed paragenetic, electron microprobe, fluid inclusion and S,C,O-isotope study was conducted on Pb-Zn-Sb-Ag mineralization of the vein H32A, Háje deposit, Příbram uranium and base-metal district, Czech Republic. The vein is hosted by folded Neo-Proterozoic sandstones and siltstones of the Teplá-Barrandian unit in exo-contact of the Central Bohemian Plutonic Complex of the Variscan age (354–335 Ma). The ore zone is close to a crustal-scale tectonic zone dividing two distinctly different basement blocks of the Bohemian Massif. A rich mineral assemblage consisting of 44 mineral phases formed during two major mineralization stages (siderite-sulphidic and calcite-sulphidic) widespread in the Příbram area. A complex history of the vein is evidenced from the presence of seven mineralization sub-stages and widespread repeated metasomatic replacement and dissolution of older vein during younger mineralizing events. The vein is dominated by carbonates (especially siderite-rhodochrosite, less frequently dolomite-ankerite-kutnohorite, rarely calcite), minor constituents are quartz, illite-muscovite, and chamosite (locally with up to 1.52 apfu Sb, 0.53 apfu Zn and 0.38 apfu Pb). Ore minerals are dominated by Ag-poor galena. The Fe-poor sphalerite, pyrrhotite, löllingite, arsenopyrite, Pb-Sb, Pb-Sb-Ag and Cu-Ag-Sb sulphosalts are subordinate phases and dyscrasite, native antimony and native arsenic are accessories. The fluid inclusion study revealed the wide ranges of homogenization temperatures (210–<100 °C) and salinities (0.0–30.5 wt% NaCl eq.) of exclusively aqueous fluid inclusions. General decrease of both parameters occurred during evolution of the vein. Sulphur isotope disequilibrium was found between co-existing galenas and sphalerites. The calculated fluid δ13C values range between −9.0 and −12.3 ‰ V-PDB, implying for a well-mixed source of carbon, or its significant re-cycling during processes of dissolution-reprecipitation of vein carbonates. The calculated fluid δ18O values are highly positive for early siderite (+7.2 to +9.6 ‰ V-SMOW), and near-zero for later dolomites and calcites (−2.9 to +3.2 ‰ V-SMOW). The siderite fluids likely represent deeply circulated waters, which underwent a significant isotope exchange with hot crustal rocks. Late low-salinity fluids were likely sourced from the Permian partly evaporated freshwater piedmont basins. The high-salinity Ca-Na-Cl brines rarely recorded in secondary fluid inclusions hosted by late calcite likely represent either local “shield brines” or basinal brines of marine provenance. The study site covers a metallogenetically significant portion of the Late Variscan fluid history within an active crust-scale tectonic zone hosted by basement of the Bohemian Massif. A pronounced Ag enrichment of this vein is mainly caused by widespread occurrence of inclusions of late-stage Ag minerals (dyscrasite) in the vein, which form rich concentrations in the shallower parts of the Háje deposit.

NdR: Articolo approcciato in maniera molto interessante. Quando si ha un WDS a portata di mano si può avere un sacco di informazioni certe in più...
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»


Chi c’è in linea

Visitano il forum: Bing [Bot] e 10 ospiti