Zr-bearing minerals as indicators for the polymetamorphic evolution of the eastern, lower Austroalpine nappes (Stubenberg Granite contact aureole, Styria, Eastern Alps, Austria) P. Tropper a, ⁎ , D. Harlov b , E. Krenn c , F. Finger c , D. Rhede b , F. Bernhard d a Faculty of Geo-and Atmospheric Sciences, Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, A-6020 Innsbruck, Austria b GeoForschungsZentrum Potsdam, Telegrafenberg, D-14473 Potsdam, Germany c Division of Mineralogy and Material Sciences, University of Salzburg, Hellbrunnerstrasse 34, A-5020 Salzburg, Austria d Fasangasse 11, A-8073 Feldkirchen, Austria Received 23 November 2005; accepted 7 July 2006 Available online 17 August 2006 Abstract Contact metamorphism during emplacement of the Permian Stubenberg Granite has led to the formation of the assemblage forsterite + calcite + titanian clinohumite ± phlogopite ± chlorite in the adjacent marbles. During intrusion of the granite, veins, rich in Ti, Zr, REE, and actinides (U+Th) formed. These veins show a distinct mineralogical zoning-sequence with four zones. Going from the center of the vein to the margin, these zones include the assemblages (1) geikielite + baddeleyite + zirconolite + apatite + calcite + chlorite ± magnetite ± pyrrhotite assemblage, (2) calcite + chlorite, (3) forsterite + titanian clinohumite + chlorite + calcite ± phlogopite and (4) calcite ± forsterite. Baddeleyite is always replaced by zirconolite, possibly via the model reaction baddeleyite + 2 geikielite + 3 calcite + CO 2 = zirconolite + 2 dolomite. Zirconolite (Zirc I) shows a strong internal oscillatory zoning and distinct overgrowths (Zirc II), which have a different chemical composition. The chemical variation between the cores (Zirc I) and the rims (Zirc II) can be explained by using the substitutions: Me 5+ +Me 2+ = Ti 4+ +Me 3+ and REE 3+ +Me 5+ +Me 2+ =Ca 2+ + 2Ti 4+ . In contrast to zirconolite from metacarbonates associated with contact aureoles, these analyses show elevated Nb contents of up to 4.5 wt.% Nb 2 O 5 and unusually high W contents of 1–2 wt.% WO 3 . A strong Eo-Alpine metamorphic overprint led locally to the formation of the assemblage chlorite + dolomite + calcite + ilmenite ± zirconolite II ± geikielite + Fe-sulfides. Late zircon grew locally, presumably as the last Zr-bearing mineral in the carbonates which formed during Permian contact metamorphism. The Zr-mineral sequence baddeleyite–zirconolite–zircon implies an increasing a(SiO 2 ) and fCO 2 during the growth of these minerals. Electron- microprobe dating of zirconolite (Zirc I) yields a weighted average age of 263 ± 16 Ma and indicates that the HFSE-and REE-rich assemblages formed during the Permian emplacement of the Stubenberg granite. As a result of the subsequent high-P Eo-Alpine metamorphic overprint (111 ± 15 Ma), HFSE and REE were locally re-mobilized leading to dissolution of Zirc I and reprecipitation of the REE and Nb-rich overgrowths of Zirc II. © 2006 Elsevier B.V. All rights reserved. Keywords: Zirconolite; Baddeleyite; Contact metamorphism; Austroalpine; Eo-Alpine metamorphism; Eastern Alps Lithos 95 (2007) 72 – 86 www.elsevier.com/locate/lithos ⁎ Corresponding author. E-mail address: Peter.Tropper@uibk.ac.at (P. Tropper). 0024-4937/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.lithos.2006.07.008