Die Magnesitlagerstätte Sunk/Hohentauern und ihr geologischer Rahmen

Summary: The magnesite deposit of Sunk/Hohentauern.- The paper represents a comprehensive collection of available data of the sparry magnesite deposit of Sunk/Hohentauern (mine activities 1907 – 1991) and its geological surroundings. The deposit is situated in the Viséan Steilbachgraben Fm. of the structural base (Veitsch nappe) of the Upper Austroalpine Greywacke zone of the Eastern Alps (Styria/Austria). The deposit is one of the numerous sparry magnesite deposits/occurrences within the Veitsch nappe magnesite(talc)district of the Eastern Alps. This district is hosting the type localities of the Veitsch type magnesite deposits. The deposit and the Veitsch nappe were exclusively deformed and metamorphosed (greenschist metamorphic facies) during the Cretaceous Alpine orgenetic events followed by intensive Tertiary fault tectonics.
In the deposit the sparry magnesite (mostly pinolit magnesite = coarse grained, light elongated magnesite crystals in a dark graphitic matrix) is mainly bound to three layers (“Liegend-“, “Mittel-“ and “Hangendbank”). The host rocks are shallow marine carbonatic sediments (with corals, brachiopods) separated by clastic graphitic sediments. The individual magnesite bodies seem to be incorporated within in the Alpine tectonic fabric. In accordance to a 3-D model the magnesite layers of the open pit (dipping 30 – 40o to the NW) are changing to cylindric and lenticular geometries to the depth and much more shallow dippings by approaching the Middle-/Upper Austroalpine thrust plane.
We are far away from a genetic model including all relevant parameters. After a short review of genetic models for sparry magnesite deposits some constraints were discussed in relation to their importance for a genetic model of the Sunk/Hohentauern magnesite deposit.

Joannea Geol. Paläont. 3: 63-103 (2001)