Jakob Pamić

Geodynamic and petrogenetic evolution of Alpine ophiolites from the central and NW Dinarides: an overview

Abstract Dismembered ophiolites occur in the Dinaride Ophiolite Zone (DOZ) that is related to the open-ocean Tethyan realm, whereas highly dismembered ophiolites occur in the Vardar Zone (VZ) related to a back-arc basin. The ophiolites of DOZ are associated with a Jurassic olistostrome melange (DOZM), the youngest component of which are Tithonian limestone exotics and with the Mesozoic bed-to-bed Radiolarite Formation. Late Jurassic/Early Cretaceous to Late Cretaceous clastic sequences, comprising redeposited fragments of ophiolites, disconformably overlie the DOZM. Ophiolites of VZ are associated with tectonized ophiolite melange (VZM), the youngest component of which are Late Cretaceous–Paleogene limestone exotics. The VZM is associated with the Late Cretaceous–Paleogene flysch formation. Ophiolites of both the DOZ and the VZ are predominantly peridotite tectonites, represented mainly by fertile spinel lherzolite in the western and central part of DOZ and VZ, and by depleted harzburgites in their southeastern parts. Cumulate ultramafics and gabbros are subordinate and are in some places overlain by massive or sheeted dyke complexes, capped by metabasaltic pillow lavas. Metamorphic soles of ophiolites are represented by varieties of amphibolites with subordinate pyroxenite schists and scarce eclogites with ultramafic interlayers, which were progressively metamorphosed under P–T conditions of eclogite (?), granulite, amphibolite and greenschist facies. The according protoliths are cumulate gabbros in the DOZ, medium-grade bimineralic epidote–amphibolite facies amphibolites derived from diabase–dolerites, and low- to medium-grade metapelites and metapsammites. K–Ar and Sm–Nd measurements yield ages of 174±14–136±15 Ma on ophiolites from DOZ and 109.6±6.6–62.2±2.5 Ma on ophiolites from VZ. Basic petrological and geochemical features for all Dinaridic ophiolites and associated amphibolites are correlatively presented both for DOZ and VZ. Dinaridic ophiolites were generated in the Dinaridic Tethys over the period of about 150 Ma. The bulk of oceanic crust was generated during the Late Triassic to pre-Late Jurassic/Early Cretaceous when oceanic subduction processes, accompanied by DOZ ophiolite obduction onto the Apulian margin, started. Generation of the oceanic crust continued during the Cretaceous–Early Paleogene in a reduced Dinaridic Tethys under back-arc setting. Eocene closure of the Dinaridic Tethys was accompanied by the second emplacement of VZ ophiolites and the final structuration of the Dinarides and their uplift. At the end, geological and petrological similarities and dissimilarities of ophiolites from both DOZ and VZ are presented.

Geodynamic evolution of the northern Dinarides and the southern part of the Pannonian Basin

Abstract Most of the recent geodynamic interpretations of the Pannonian Basin focus on its relation to the formation of the Carpathians and the Alpine orogeny. However, also the Dinarides were severely affected by Neogene tectonics related to the formation of the Pannonian Basin. Especially in the northernmost Dinarides Neogene deformation played a very important role in the evolution of this mountain chain. Geological records clearly show evidence of two phases of plate convergence along the northern and eastern margins of the present-day Dinarides. At the end of the Jurassic the Dinaridic parts of the Tethys ophiolites were obducted onto the northeastern margins of the Apulian microplate. The second phase is documented in the central part of the northernmost Dinarides. It is genetically related to an ancient volcanic arc, as indicated by Late Cretaceous–Palaeogene trench sediments with blueschist olistolithes which are interlayered by basalt, rhyolites, pyroclastics, medium-pressure metamorphosed trench sediments, and associated synkinematic granitoids. In the northern part of the Dinarides subduction processes terminated with the Eocene compressional event which caused the uplift of the Dinarides. Numerous intramontane basins with shallow-marine, fluviatile and lacustrine deposits were generated during the Oligocene. Penecontemporaneous andesites which are found along the Drava and Sava depressions of the South Pannonian Neogene Basin can be correlated with the easternmost Periadriatic tonalites. However, observations do not indicate strike-slip faulting at that time in this area. The Neogene rift stage initiated the evolution of the Pannonian Basin. It is marked by extruded submarine trachyandesites of Karpathian age, Badenian basalts, andesites, dacites and rhyolites, and Pannonian alkali basalts, which are interlayered by coeval sedimentary rocks. Main evidence for the large-scale tectonic transport of large Dinaridic blocks into the Pannonian Basin area are the Periadriatic–Sava and Zagreb–Zemplen fault systems and subparallel faults. The late Sarmatian global sea-level drop which coincided with a compressional phase is regionally marked by an unconformity throughout the Pannonian Basin, as reported by Horvath (Horvath, F., 1995. Phases of compression during the evolution of the Pannonian Basin and its bearing on hydrocarbon exploration. Mar. Pet. Geol. 12 (8), 837-844). Due to thermal subsidence during the Pliocene more than 2000 m of lacustrine freshwater sediments were deposited in the South Pannonian Basin. The Pliocene compression phase can be observed in the Transdanubian zone and also south of the Mura and Drava rivers by south- and southwest-dipping reverse fault systems.

Triassic magmatism of the Dinarides in Yugoslavia

Abstract The Triassic magmatism of the Dinarides had a polyphase character. It took place during a period of about 50 Ma during the initial stages of the Mesozoic Wilson cycle. Their earliest phases might have been connected with rifting processes, and the subsequent ones preceeded directly the opening of the Dinaridic part of the Tethys and the formation of a spreading ridge. The Triassic magmatism is represented by basic, and more commonly by intermediate and acid plutonic and volcanic rocks with calc-alkaline affinity. The Triassic magmatic rock association can be correlated on major element evidence with calc-alkaline rocks of recent convergent plate margins. However, field relationships and the data on immobile trace elements indicate that lavas poured out over Triassic sediments on a carbonate platform which was underlain by rocks of the continental crust. The basic diversity of the Triassic magmatism of the Dinarides was influenced by partial melting. Other processes (crystallization, contamination and others) must have played a secondary role.

Eoalpine to Neoalpine magmatic and metamorphic processes in the northwestern Vardar Zone, the easternmost Periadriatic Zone and the southwestern Pannonian Basin

Abstract The occurrence of Eoalpine-Neoalpine, genetically different, granitoids and penecontemporaneous volcanics are characteristic for the Vardar Zone. These rocks are mostly associated with Late Cretaceous-Paleogene basinal sedimentary rocks underlain by ophiolites. The Late Cretaceous-Paleogene rocks were progressively metamorphosed under mediumpressure conditions and intruded by synkinematic Mesoalpine granitoids. The high-pressure blueschist metamorphism was related to a pre-Maastrichtian Eoalpine metamorphic event. Eoalpine and Mesoalpine magmatism and the related metamorphism of the Vardar Zone may have taken place along a magmatic arc, i.e., the subduction zone. The easternmost parts of the Periadriatic Zone are characterized only by Oligocene granitoids accompanied by penecontemporaneous volcanic rocks. Here, younger Alpine metamorphic phases only overprint and mylonitize older pre-Alpine formations. Most of the Mesoalpine granite plutonism both of the Vardar Zone and the easternmost area of the Periadriatic Zone was related to subsequent extension. The southwestern and southern parts of the Pannonian Basin contain the products of four pulses of Mesoalpine and Neoalpine synsedimentary volcanic activity (Egerian-Eggenburgian, Ottnangian-Carpathian, Badenian and post-Badenian) represented by predominant basalt-andesites, trachyandesites and trachydacites. This post-subduction volcanism was closely connected with the cyclic marine ingressions in the Pannonian Basin.

Age of amphibolites associated with alpine peridotites in the Dinaride ophiolite zone, Yugoslavia

Abstract Amphibolites associated with alpine peridotites in the Central Ophiolite zone in Yugoslavia have K-Ar ages of 160–170 m.y. These amphibolites and associated peridotites underwent deep-seated metamorphism prior to tectonic emplacement into the sedimentary-volcanic assemblage of the Dinarides. The alpine peridotites and associated local rocks of the ophiolite suite are interpreted as Jurassic oceanic crust and upper mantle.

Tertiary Volcanic Rocks from the Southern Pannonian Basin, Croatia

The Tertiary volcanic rocks of the southern part of the Pannonian Basin are related to a sequence of tectonic events that occurred along the northern margin of the Dinarides when subduction ceased and after uplift of the region in middle Eocene time. The oldest rocks are andesites and dacites erupted during an Egerian to Eggenburgian marine transpression phase. In early Miocene time (about 17 Ma), rifting started, probably caused by the rise of the mantle, resulting in E-W extension and strike-slip faulting leading to formation of the Pannonian Basin. The initial rifting was accompanied by trachyandesitic volcanism of Karpathian age, followed by Badenian-age (15 to 13 Ma) volcanic activity producing basalts, andesites, and dacites. During these volcanic phases the Pannonian Basin, or the Paratethys, probably was periodically connected with the Mediterranean Sea. The final period of volcanism (about 9 to 7 Ma) produced alkalic basalts and basalts and occurred in fresh-water environments. These volcanic roc...