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  • Author or Editor: Jakob †Pamić x
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Three Internal Dinaridic tectonostratigraphic units are included in the PANCARDI domain; 1) the Bosnian Flysch, composed of the Liassic to Berriasian Vranduk Subgroup and the Albian to Maastrichtian Ugar Subgroup, originating on the passive Tethyan margin, 2) the Dinaride Ophiolite Zone, made up of the Radiolarite Formation, ophiolite included within the Jurassic olistostrome mélange, and a Cretaceous overstep sequence, partly with Urgon-type(?) signatures, and 3) the Sava-Vardar Zone, composed of Cretaceous-Early Paleogene flysch, locally with subduction-related basalt-rhyolites, a Paleogene, very low to medium-grade metamorphic sequence originating from the Cretaceous-Paleogene flysch, Paleogene tectonized ophiolite mélange, Eocene syncollisional granitoid occurrences and Oligocene postcollisional ones, accompanied by coeval shoshonite and andesite. All these formations occur as allochthonous blocks within two segments of the southern and western Pannonian Basin. 1) In the adjoining Tisia-Dinarides segment, the Sava-Vardar Zone lithologies occur both at the surface and in the subsurface of the Pannonian Basin, as the result of postorogenic Dinarides-Tisia interaction. Those located in the basement were uplifted during the Oligocene wrench faulting, which controlled the initial development of the Sava and Drava depressions. Those found at the surface were emplaced during the Pliocene phase of strike-slip faulting. 2) More common are Internal Dinaridic fragments sandwiched within the Alps-Dinarides-Tisia (e.g. Carpathians) triple junction area, e.g. the Zagorje-Bükk-Meliata Zone. In its southwestern Sava Subzone occur fragments of the Bosnian Flysch Zone and Sava-Vardar Zone, represented by a Paleogene tectonized ophiolite mélange, Cretaceous-Paleogene flysch and postcollisional andesite-shoshonite. The northeastern Bükk-Meliata Subzone is composed of a Jurassic ophiolite mélange correlative to the Dinaride Ophiolite Zone, which in its Slovakian part is thrust by Triassic, mainly carbonate formations. The accompanying Mónosbél Flysch can be correlated with the Vranduk Subgroup of the Bosnian Flysch. The displacement of the Internal Dinaridic formations can only partly be explained by Tertiary escape (extrusion) tectonics.

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Permo-Triassic rift-related magmatism in the Dinarides produced an intrusive gabbro-diorite-syenite-granite formation and an extrusive basalt-andesite-dacite formation with abundant pyroclastic rocks. They are spatially and genetically related to Late Permian to Norian rift-related sedimentary formations of the Adriatic-Dinaridic carbonate platform (ADCP). The volcanic and pyroclastic rocks are interlayered with fossiliferous sediments that range between the Late Permian and Middle Norian; the plutonic rocks, which are intrusive into Late Paleozoic and Scythian-Anisian sediments, have radiometric ages ranging between 262 and 212 Ma. Based on major and trace element contents, rocks of the Permo-Triassic magmatic association originated by fractional crystallization from primitive alkalic basalt to olivine tholeiite melts. Volcanic rocks were affected by strong ocean-hydrothermal metamorphism. Initial 87Sr/86Sr ratio of 0.703 and d18O of 5.6‰ of the most primitive rocks indicate an upper mantle origin. Most initial 87Sr/86Sr ratios range between 0.704-0.707, indicating a slight degree of crustal contamination. The Permo-Triassic igneous rocks of the Dinarides represent a specific and autonomous paleorift-related association, which cannot be correlated with the magmatic associations either from recent oceans or with alkali rocks from the Cenozoic African rift and Permian Oslo graben.

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The Dinaridic Alpine ophiolites can be divided into two groups: 1) those of the Jurassic Dinaride Ophiolite Zone (DOZ) and 2) those of the Cretaceous-Early Paleogene (?) Sava-Vardar Zone (SVZ). However, geologically and petrologically they have so far been treated as a whole, and their geotectonic setting has not been reliably established. We have investigated ophiolite terranes from both regions in order to determine their tectonic setting. Our comparison is based on trace element data and characteristic elemental ratios correlated with ophiolite settings in recent oceans. We show that the DOZ tectonite peridotites are enriched in LREE and have high Ti/V ratios (up to 23), whereas the SVZ mantle rocks are LREE-depleted and have low Ti/V ratios (1-4). The DOZ cumulate gabbros and peridotites are characterized by increased Ni content and high Ba/Sr ratio, positive Eu anomalies and lower Cr# of spinels, comparable with MORB cumulates. The SVZ cumulates do not show a positive Eu anomaly and are characterized by higher concentrations of V, Zr and Y, and higher K/Nb, Ti/Zr, Zr/Sm ratios, which correlate with those from some recent back-arc settings. Essential differences between DOZ and SVZ basaltic rocks are as follows: high-Ti vs. low-Ti ophiolites: Ti/V = 20-50 vs. <20; higher Mg#, Ni, Cr, Nb and Ta vs. higher Rb and Ba; elemental ratios of Sr/Zr, Ti/Zr, Y/Nb, Zr/Nb, Th/Nb, Th/Ta, La/Nb, La/Ta and Sm/Hf are similar to those from recent back-arc settings. These geochemical data confirm the earlier geologic model of Pamić et al. (2002). These contrasting geochemical signatures are the result of different geochemical processes taking place in two different settings: a) MORB along an accretionary plate margin underlain by oceanic upper mantle, and b) BARB along a supra-subduction zone characterized by an obducting upper mantle wedge underlain by subducted oceanic crust, which was a source of fluids.

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The Internal Dinarides include ten larger allochthonous pre-Alpine complexes, similar in many respects to those in the Eastern Alps, Carpathians and Rhodopes. The Dinaride Paleozoic complexes consist mainly of Devonian to Permian formations and are commonly associated with abundant Triassic sediments. In addition, the largest Paleozoic complexes contain subordinate Cambrian-Ordovician formations. The best developed Early Paleozoic complex, which occurs in western Macedonia, is composed of fossiliferous Cambrian metasediments with ophiolites and fossiliferous Ordovician metasediments, interlayered with subordinate metavolcanics and intruded by coeval Ordovician granitoids (461-465 Ma) that were overprinted during the Variscan and Alpine tectonogeneses. It is underthrust by Variscan formations and overthrust by Neoproterozoic Pelagonide formations. Parts of the Paleozoic Drina-Ivanjica complex are composed of fossiliferous Cambrian-Ordovician metasediments containing metamafics and metatuff that were overprinted by Early Cretaceous metamorphism. In the Mid-Bosnian Schist Mts, formations of presumed Cambrian- Ordovician age characteristically consist of gneiss and amphibolite, which can be compared to the Oetztal complexes of the Eastern Alps. Dinaridic Cambrian-Ordovician formations from all three areas were metamorphosed during the late Ordovician deformation under P-T conditions of greenschist and, to a lesser extent, epidote-amphibolite facies (400-500 °C and 4-5 Kbar). Based on geochemical data, Ordovician bimodal volcanics and granitoids indicate a geotectonic setting comparable to recent back-arc basins.

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