Abstract
Abstract In the Permian rhyodacite quarry at Zalas near Krakow, southern Poland, thallium-bearing Mn oxides occur in a small fault zone cutting Middle Jurassic sandy limestone poorly encrusted by an oxidized polymetallic mineralization. The encrustation comprises sulphides (pyrite, chalcopyrite, chalcocite, covellite, galena, marcasite), native bismuth, hematite, goethite, cuprite, mottramite, iodargyrite, unrecognized Cu sulphates and Bi oxychlorides as supergene minerals, barite and rare tiny grains of gold. It is most likely connected with rejuvenation of Early-Paleozoic faults during the Alpine orogeny on the Oligocene–Miocene boundary. Rare Tlbearing Mn oxides occur in an outside zone of the encrustations, filling small fractures and voids in limestone forming the fault breccia. Tl contents, reaching 20.82wt% as Tl2O, exceed by more than two orders of magnitude those reported in similar minerals before, making the oxides unique on a world scale. The Tl-bearing Mn oxides from Zalas reflect intensive weathering of an older Tl-bearing sulphide mineralization in an arid climate, involving saline fluids delivered to the groundwater system as the nappe structure of the Carpathians was developing during the Sava tectonic phase Oligocene/Miocene boundary.
Highlights
In-situ fossil, preglacial-oxidized, polymetallic mineralization at Zalas in the Krakow area, southern Poland, found in a breccia coming from a small fault zone exposed by mining works in 2005
In the Permian rhyodacite quarry at Zalas near Krakow, southern Poland, thallium-bearing Mn oxides occur in a small fault zone cutting Middle Jurassic sandy limestone poorly encrusted by an oxidized polymetallic mineralization
The Tl-bearing Mn oxides from Zalas reflect intensive weathering of an older Tl-bearing sulphide mineralization in an arid climate, involving saline fluids delivered to the groundwater system as the nappe structure of the Carpathians was developing during the Sava tectonic phase Oligocene/Miocene boundary
Summary
In-situ fossil, preglacial-oxidized, polymetallic mineralization at Zalas in the Krakow area, southern Poland, found in a breccia coming from a small fault zone exposed by mining works in 2005. Unauthenticated Download Date | 2/2/17 12:01 PM sulphides and their supergene products as well as Mn oxides, which, in some cases, contain significant Ca, Ba, Pb, Co, Ni and Tl contents (Gołębiowska et al 2010). A link between weathering-stage Mn oxides and thallium is well known in Tl geochemistry (Critteden et al 1962; Schmiermund 2008; Kabata-Pendias 2011), this discovery is of world significance due to unusually high Tl contents reaching 20.82wt% as Tl2O. About 50 species are known and none is a Mn oxide. They comprise sulphides, arseno- or antimono-sulphides, mainly related to the epithermal stage of hydrothermal activity. The compositions of the Tl-bearing Mn oxides from the oxidation zone at Zalas are discussed in order to evaluate the reasons for such atypically-high Tl concentrations in some of the oxides
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