Late Triassic basin and ore deposit formation in the north-western Tethyan realm

The aim of the proposed project is to clarify the Late Triassic basin and ore deposit formation in the framework of the geodynamic history of the north-western Tethyan realm in time and space during and after the drowning/demise of the Middle to early Late Triassic (Wetterstein) carbonate platforms. In order to get precise information about the tectonic regime in Late Triassic time it is necessary to analyse A) the basinal depositional setting as well as new basin formation and their relation to tectonic motions, and B) the formation ages of different ore mineralizations in the Palaeozoic to Triassic rocks. Following contrasting models for the Late Triassic tectonic exists: 1) extensional, due to further rifting in the Neotethyan realm or as precursor of the opening of the later Piemont/Penninic Ocean, 2) strike-slip, related to the early extension in the Piemont/Penninic realm. A third model (3), strike-slip movements probably combined with compressional structures, related to the closure of the Palaeotethys Ocean, is until now not discussed. This unexplored tectonic event affected the deeper continental crust as well as the overlying non-metamorphic Late Carboniferous to Triassic sedimentary cover. The Late Triassic motions are expressed in the sedimentary successions and correlate with several isochron formation ages of ore deposits as result of ascending mineralized fluids along fault zones associated with high heat flow in the deeper crust. The first thermochronological dataset indicate a metasomatic mineralization of Palaeozoic to Triassic rocks due to infiltrating of residual brines in Late Triassic times. To solve these questions I plan: A) Biostratigraphic dating and facies analysis of the sedimentation pattern in these basins combined with breccia analysis. B) Geochemical fluid characterization and age dating of the formation of the ore deposits. C) Reconstruction of the cooling history of the mineralizations by using Conodont (U-Th)/He thermochronology. This seems especially for carbonatic ore deposits a very helpful tool. A) to C) should result in a better understanding of the mineralization and basin forming processes and that will lead to a more convincing palaeogeographic reconstruction of the north- western Neotethyan realm. The best targets to carry out the proposed investigations are the Eastern Alps, the eastern part of the Southern Alps, the units in the northern Pannonian realm, and the Gemeric units in the southern Western Carpathians. A better understanding of the Late Triassic palaeogeography and geodynamic history will be in future a helpful tool in the exploration of unknown ore deposits. It will have a great impact in understanding the formation of mineralizations in mountain chains.

The Late Triassic carbonatic passive continental margin successions facing the Neotethys Ocean to the east of the Eastern and Southern Alps, the Western Carpathians and the Dinarides are characterized by recently reevaluated important tectonic motions. Tectonic started after the Mid-Carnian drowning/demise of the Wetterstein Carbonate Platform. The reasons are controversial discussed: A) Extensional, due to an early rifting pulse of the later Alpine Atlantic Ocean, and probably with contemporaneous strike-slip movements; B) an extensional/rifting pulse in the north-western Tethyan realm; or 3) strike-slip tectonics combined with compression/mountain building process related to the closure of the Palaeotethys and uplift of an orogen. An expression of this tectonic is the formation of new basins and ore deposits. Best possibilities to solve the open question provide investigations on sedimentary sequences from the open-marine outer shelf to the interior shelf with carbonate platforms; only there is a most complete sedimentary record reserved. High resolution age dating in combination with sedimentological and geochemical studies allow detailed reconstructions of the Late Triassic oceanographic and geodynamic history. The most important new results of the project are:The overall tectonic regime changed in Late Triassic times. Three stages were recognized: I) After the early Middle Carnian demise of the Wetterstein Carbonate Platform, differences in the overall tectonic regime can be distinguished by the palaeogeographic position and are expressed as a) late Middle Carnian drowning of the platform by siliciclastics, triggered by sea-level rise, b) long lasting uplift of the platform and Late Carnian flooding, due to rapid subsidence and most probably triggered by extension. II) A period of relative tectonic quiescence in the time span latest Carnian to late Early Norian, with a short lasting event around or shortly after the Carnian/Norian boundary, and III) the onset of strike-slip movements in the Middle Norian by culminating the late Middle Norian and rapidly decreasing intensity in the early Rhaetian. First expression of tectonics related to the extension in the Penninic realm is in the Early Jurassic.Differences in the tectonic regime are expressed in sedimentological and geochemical characteristics in the hemipelagic sedimentary successions. Shifts in stable O- and C-isotopes seem to be coupled with shifts in the concentration of transition metals and light rare earth elements indicating climate changes and erosion of ophiolitic or deeper continental crustal material, which can be correlated with sea-level changes, platform evolutions and sedimentation processes in the newly formed basins.The concentration of transition metals and light rare earth elements in the sedimentary successions depends on the sedimentation rates and on the redox environment in the sediment. Salinar bottom currents and bacteria activity have a great impact on stable isotope excursions and element enrichment.Summarizing, the results yield an important step forward for the A) understanding of the Late Triassic geodynamic evolution of the north-western Tethys domain, and B) provide new insights in the triggering factors for oceanographic circumstances and element enrichment. A combination of established methods provide new possibilities to test actually controversial discussed models for mass extinctions (eg., ocean acidification), climate changes or the enrichment of metal ions due to bacterial activity.