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%0 Thesis
%A Sindern, Sven
%T Mineralogical, geochemical and geochronological studies in the Uralides and Variscides : contributions to the understanding of dynamic processes in collisional orogens
%I Rheinisch-Westfälische Technische Hochschule Aachen
%V Priv. Doz.
%C Aachen
%M RWTH-2016-09308
%P 1 Online-Ressource (B-E, 218 Seiten) : Illustrationen, Diagramme, Karten
%D 2014
%Z Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2016
%Z Habilitationsschrift, Rheinisch-Westfälische Technische Hochschule Aachen, 2014, Kumulative Habilitationsschrift
%X This thesis presents mineralogical, geochemical and geochronological studies in the Variscides and Uralides to elucidate the petrochemical history of dynamic orogenic processes. In combination with published data the results highlight significant differences between both orogens.Pre-orogenic (i.e. pre-Uralian) basement is incorporated to different degrees and in contrasting patterns in Variscides and Uralides. In the Variscides numerous different terranes were agglomerated in a complicated large scale bow-shaped pattern, whereas in the Uralides mainly the fragments of the longitudinally trending eastern margin of Baltica were incorporated. The Taratash Complex of the Middle Urals is an outstanding example of such fragments. This thesis delineates a succession of Palaeoproterozoic magmatic and amphibolite facies tectonometamorphic events (2.46 – 1.8 Ga) following Archean granulite facies metamorphism and granitoid formation (3.65 – 2.91 Ga) recorded in the rocks of the Taratash Complex. In the Uralides, pre-orogenic basement is restricted to the west of the Main Uralian Fault leading to a simple geometry compared to the Variscides. In both orogens, pre-Neoproterozoic rocks are only preserved in basement slivers, whereas remnants of Neoproterozoic magmatism and tectonism are abundant. For the southern Urals this is shown in a study of detrital zircon. Isotope signatures (U/Pb) of detrital zircon serve as geochemical indicator for the dynamic process of terrane accretion and for the transition from a passive to an active continental margin around 620 Ma, which affected large parts of the eastern margin of Baltica.The main suture lines and associated former subduction zones can well be traced in the Variscides (i.e. Rheic suture) and Uralides (i.e. Main Uralian Fault), although secondary suture lines in both orogens require further characterization for better understanding. Different to the Variscides, where high-pressure metamorphic rocks are known in all major terranes, such rocks are exclusively observed along the Main Uralian Fault in the Uralides. Lawsonite bearing mineral assemblages in rodingitized ultramafite of the Maksyutov Complex (Southern Urals) that are investigated in a part of this thesis are an example of such metamorphism related to the dynamic process of subduction.In contrast to the Variscides, which are characterized by large scale lithospheric reequilibration, the Uralides were not affected by significant orogenic collapse and postorogenic extension. This is also reflected in the preservation of prograde high-pressure/low-temperature metamorphic assemblages in the Maksyutov Complex (e.g. Lawsonite-bearing assemblages) and associated low-temperature pseudomorphs presented in this thesis. The lack of postorogenic extension highlights that the Uralides are characterized by a pronounced and isostatically equilibrated crustal root.During the Variscan orogenesis existing continental crust was extensively recycled. In contrast to this, large amounts of juvenile crust, which formed in magmatic arcs, are a characteristic feature of the Uralian orogen. Here, data are presented for the Valerianovka arc in the Transuralian zone, which is rarely addressed in the literature. It is shown that granitoids formed by mixing of slab-derived melts and melts generated in the crust. This result supports the model of an Andean type setting. Juvenile crust is particularly dominating in the Easturalian zone, where granitoids also formed after accretion of magmatic arcs. In this thesis it is demonstrated that the Borisov granite intruded in a first pulse of melt generation at 358 ± 23 Ma. Granitoid melt formation as well as high-temperature amphibolite facies metamorphic overprint of host rocks also reflect the dynamic process of crustal thickening during the Uralian orogeny. Variscides and Uralides also vary with respect to their crustal architecture. Major crustal units of the Variscan orogen have a subhorizontal orientation, whereas crustal scale structural boundaries in the Uralides are high angle fault zones. Such structural differences are in line with the observation that the Variscides experienced significant crustal shortening, whereas the Uralides were affected by lower degrees of shortening. This can be demonstrated in a comparison of the Rhenohercynian (Variscan) and the Westuralian foreland fold and thrust belts. Expulsion of hydrothermal fluids to the Variscan foreland during the dynamic process of orogenic compaction is investigated in this thesis applying various techniques. Enrichment of mobile components, such as Ba and NH4, in sedimentary rocks studied in the RWTH-1 well in Aachen (Germany) serves as geochemical indicator for palaeo fluid-flow. Illite mineralogy, fluid inclusion petrography and microthermometry as well as isotope geochemistry of fluid inclusions and vein minerals suggest that expulsion of metamorphic fluids at the Variscan front was a short termed (approx. 5000 y) process , which was affected by fracture opening during episodic seismic activity and which occurred at depths between 4500 and 8000 m and temperatures close to 400 °C. Both, Variscan and Uralian orogens were affected by post-Palaeozoic deformation, however Alpine reworking significantly obliterated Variscan structures, in particular in the southern part of the Variscides.
%F PUB:(DE-HGF)13
%9 Habil / Postdoctoral Thesis (Non-german Habil)
%U https://publications.rwth-aachen.de/record/674310