Provenance and age constraints on Cretaceous bauxites in the Eastern Alps, Transdanubian Range and Western Carpathians

Abstract Constraining the timing, provenance and paleogeographic relationships of Cretaceous karst bauxites in the Austroalpine realm remains challenging due to their highly weathered, polygenetic nature and the general lack of datable fossils. X-ray diffraction (XRD) data show consistent boehmite–hematite assemblages in the Alpine deposits, whereas the Transdanubian bauxites (Alsópere, Iharkút) additionally contain gibbsite. Heavy mineral spectra are dominated by the ultrastable zircon–rutile–tourmaline assemblage, with subordinate kyanite, sillimanite and Cr-spinel pointing to contributions from medium- to high-grade metamorphic and ultramafic sources. Detrital zircon U–Pb spectra record mostly Proterozoic, Cadomian, Caledonian, Variscan, and Permian age components with regional contrasts. The Northern Calcareous Alps are dominated by Variscan ages, while Permian signatures are more prominent in the Transdanubian Range. Santonian (∼85 Ma) zircons at Kufstein reflect distal aeolian input from the Banatite magmatism. Zircon (U–Th)/He data reveal distinct low-temperature histories of the sources: Russbach contains a 90–75 Ma cooling signal reflecting Eoalpine metamorphic core complexes, whereas Jurassic–Early Cretaceous ages from Iharkút indicate sourcing from Upper Austroalpine units. Statistical comparisons confirm clustering among Santonian deposits but reveal heterogeneity in Albian and Turonian sites. The data indicate that Northern Calcareous Alps and Transdanubian Range bauxites formed from geographically distinct yet lithologically similar sources, with the rising central Austroalpine nappes acting as a topographic divide. The results refine the timing of bauxitization in the Alps, showing that some deposits, such as Russbach, are younger than previously thought, and that bauxitization was diachronous and largely controlled by tectonics during the Cretaceous.