Absolute time constraints on multistage tungsten enrichment and re-distribution processes in the Felbertal scheelite deposit (Eastern Alps)

• Applicants: Dr. Joachim Krause; Professor Dr. Bernhard Schulz
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 521637201

The Felbertal scheelite deposit at Mittersill/Austria is one of the largest tungsten mineralisations in the world. It is overall strata-bound, but described as a stockwork mineralisation with diffuse dissemination of scheelite in metabasites of the Early Paleozoic Habach Series in the Penninic Tauern Window in the Eastern Alps. Scheelite appears in (1) stratiform distribution in an Eastern Ore Zone (EOZ, former open pit), in (2) ore bodies related to orthogneisses with Carboniferous protolith ages in the Western Ore Zone (WOZ, underground operation), and in (3) the WOZ ore bodies K7 and K8 merely unrelated to the lithologies. Until now, four generations of scheelite can be distinguished by UV- and cathodoluminescence and variable Mo contents. Intense preliminary studies by SEM, EPMA and LA-ICP-MS show that the scheelite mineral chemistry is a principal recorder of a multistage evolution with magmatic, hydrothermal, metamorphic and deformational stages at changing physico-chemical conditions. A U-Pb dating of the scheelite generations in their variable spatial distribution domains by LA-ICP-MS will provide an important step to resolve the question about the primary source of the tungsten mineralisation and to constrain the time schedule of its further evolution in course of crystallisation-dissolution-reprecipitation (CDR), recrystallization and deformation processes. The Sm-Nd and Lu-Hf scheelite dating by MC-ICP-MS are secondary objectives, as they require comparably more preliminary studies. The tungsten element mobility, transport processes and partitioning, will be further evaluated by trace element analyses of epidote, amphibole, feldspars and mica by LA-ICP-MS in the scheelite-hosting amphibolites and orthogneisses.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2238: Dynamics of Ore-Metals Enrichment - DOME