In the mining district “Karth” south of Wiener Neustadt, Lower Austria, gold was mined by hydraulic methods during the Roman period. The placer gold occurs in the Loipersbacher Rotlehmserie (Loipersbach Formation), which is composed of clay and embedded coarse gravel layers. Heavy-mineral analysis (SEM) indicates the influence of greenschist to amphibolite facies metamorphic basement units. The composition of the Mn-rich garnet is similar to that in fractionated pegmatites in the Upper Austroalpine nappe system. The morphological properties (optical microscopy) of gold particles and their chemical composition (SEM, EMPA, LA-ICP-MS) were investigated. Most of the particles are equant, sub-angular to sub-rounded, and clearly flattened with folded edges, which indicate distal primary gold mineralization. On the surface, the fineness of the gold grains is very high, in polished sections the zoning between Ag-rich core and desilvered rim is obvious. The comparison of chemical signatures shows clear differences between the gold from Karth and that from the Feistritz and Mur rivers; gold from the Mürz river is similar to Karth. Due to the comparable composition of the Tauern gold and the probable flow direction of paleo-rivers, this mineralization must be taken into consideration as a source of the gold in the Karth. However, the influence of local and regional mineralization or a combination of these possibilities cannot be excluded.
|Translated title of the contribution
|Composition of gold and associated minerals in the Roman gold mining district Karth, Lower Austria
|Published - 2020
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