High-temperature to ultrahigh-temperature metamorphism related to multiple ultrapotassic intrusions: evidence from garnet-sillimanite-cordierite kinzigite and garnet-orthopyroxene migmatites in the eastern part of the Moldanubian Zone (Bohemian Massif)
Abstract: The garnet-sillimanite-cordierite kinzigite from Petrovice, Jihlava Pluton, Moldanubian Zone, Czech Republic has a hyperaluminous chemical composition. Its mineral assemblage consisting of garnet and prismatic sillimanite I, relics of cordierite, hercynite, rutile I, ilmenite and quartz, retrograde minerals — cordierite II, fibrolitic sillimanite II and Ti-rich biotite and leucocratic portions with abundant K-feldspar, quartz and plagioclase which closely matches a restite. The prograde part of the reaction history was virtually obliterated and the mineral reactions: (1) Crd+Hrc=Grt+Sil; (2) Hrc+Qtz=Grt+Sil; (3) Grt+Sil+Qtz+L=Crd+Bt; (4) Grt+L=Crd+Bt+Qtz; (5) Grt+Crd+L=Bt+Sil; (6) Crd+L=Bt+Sil+Qtz took place during cooling. The relic assemblages cordierite+hercynite and hercynite+quartz, which represent a peak of metamorphism, are stable for P~0.5 GPa at T>~900 ºC. The P-T conditions determined by geothermobarometry yield: T=900±40 ºC (garnet–ilmenite) and P=0.73–0.49 GPa (spinel–garnet); concentrations of Zr in rutile I enclosed in garnet and sillimanite I yielded T=840–970 ºC. We assume, on the basis of the hyperaluminous chemistry and mineral assembly that the garnet-sillimanite-cordierite kinzigite from Petrovice is a restite, where a large portion of melt was lost from the rock. The sequence of mineral reactions, and garnet composition with low and constant Ca in the profile across the grain, indicate an isobaric cooling path. A moderate heat input from the Jihlava Pluton, manifested by garnet-orthopyroxene-cordierite migmatites developed at the direct contact of durbachites, supported by a local but large heat input of gabbro–monzogabbro associated directly with kinzigites seem probable heat sources. The chemical U-Pb ages of monazite 319±24 Ma from kinzigite, 329.8±9.5 Ma from garnet-orthopyroxene migmatites, and 335.8±6.9 Ma from gabbros are very close to U-Pb ages of zircon 335.2±0.5 Ma from durbachites (Kotkova et al. 2003). They suggest a Variscan age of the HT (to UHT) metamorphism and support affiliation to the durbachite intrusions.
The Mississippian in the Central and Eastern Taurides (Turkey): constraints on the tectonic setting of the Tauride-Anatolide Platform
Abstract: Data from the Mississippian tectono-stratigraphic units in the Tauride-Anatolide Platform, Central and Eastern Taurides, reveal that this region underwent incipient back-arc extension during the Variscan orogeny, but that rifting failed, leaving a basin floored with highly extended continental crust. The stratigraphy of several tectono-stratigraphic units, the Geyik Daği, Aladağ, and Bolkar Daği Units were studied in detail in the Sultan Daği and Hadim areas in the Central and Eastern Taurides. In the Sultan Dağ area, the Geyik Daği Unit contains shelf-type (shallow) marine clastics and carbonates of the Middle-Upper Mississippian Gökdere Member of the Harlak Formation, overlain by shales and basic volcanic/volcaniclastic rocks of the Kuz Member of the formation. The Mississippian age rocks in the Aladağ Unit around Hadim are characterized by quartzarenites and carbonates of coastal to shallow shelf environment. The Bolkar Daği Unit in the Hadim area includes inner shelf-type recrystallized limestones, dolomites and oolitic limestones. To the north of Konya, however, Middle Mississippian formations of the Bolkar Daği Unit include metamorphosed olistostromal deposits with Silurian–Upper Devonian olistoliths, which were generated in an extensional basin with back-arc type bimodal volcanism. In the Cataloturan Nappe of the Bolkar Daği Unit, in the Eastern Taurides, the Mississippian is represented by a basin/slope-toe- type succession with an alternation of lithic tuffs, radiolarian cherts and pelagic limestones. It grades into Upper Mississippian shallow-marine carbonates. The data presented suggest the presence of a north-facing system with slope (Cataloturan) aborted rift basin (Konya-Bolkar Daği) inner shelf (Hadim-Bolkar Daği) coastal shelf (Hadim-Aladağ) and shallow-shelf (Sultan Daği-Geyik Daği) along the northern margin of the Tauride-Anatolide Platform during the Mississippian.
Sedimentary rock record and microfacies indicators of the latest Triassic to mid-Cretaceous tensional development of the Zliechov Basin (Central Western Carpathians)
Abstract: The Zliechov Basin was situated inside the Austroalpine–West Carpathian shelf fragment detached from the Paleoeuropean margin at the end of the Triassic. Information about changes of clastic support, bathymetry, benthic organism colonization etc. were recorded during microfacies correlation of sequences analysed in detail. Comparison of individual developmental stage models constructed by plotting of these data into paleogeographic schemes indicates paleogeographic and geodynamic changes in the Zliechov Basin evolution in the regime of continuous Jurassic to middle Cretaceous extension. This development is illustrated on the basis of two developmental stages. The uppermost Triassic stage preceded rifting in the Fatric area, when the depocentre of sedimentation was located in the southern part of the arising basin. Rifting culminated during the Early/Middle Jurassic and continued during the Late Jurassic and Early Cretaceous, when a large basin originated with complex bottom morphology, affected by normal faults.
North Aegean sedimentary basin evolution during the Late Eocene to Early Oligocene based on sedimentological studies on Lemnos Island (NE Greece)
Abstract: From the Late Eocene to Early Oligocene (NP18–NP21), submarine fan deposits and shelf deposits were accumulated on Lemnos Island, Greece. These sediments, with shelf deposits overlying the submarine fans, were deposited in a broad basin, which, in this time interval was gradually restricted in space. Colour, texture, thickness, grain size and sedimentary structures were used for the detailed sedimentological analysis of the turbidite deposits, in order to identify the sub-environments and the processes which control the growth of the submarine fan. This analysis demonstrates the classification of the sediments as a sand-rich submarine fan, which was constructed under the simultaneous interaction of progradation and aggradation and shows a main paleocurrent direction from SSW to NNE. The flow types that control the depositional processes of the submarine fans were grain flows, debris flows and low, medium- and high-density turbidity currents. The evolution of depositional environments outlined above indicates a progressive relative sea-level fall, and in relation to the lowstand conditions, during this time space (NP18–NP21), with no significant sea-level fluctuations, it could establish a theory that the studied area was mostly influenced by regional tectonic activity and less by eustatic sea-level changes.
Miocene dextral transpression along the Csesznek Zone of the northern Bakony Mountains (Transdanubian Range, western Hungary)
Abstract: The authors performed geological mapping and microtectonic measurements around the Csesznek Zone in the northern Bakony Mts, Transdanubian Range, Hungary. As a result of structural observations a new structural-geological map was created for this area. Four tectonic phases were separated by the analysis of stress field. The oldest tectonic event detected in the research area was defined by a WNW–ESE compression and we attribute a Middle Eocene to the earliest Miocene (50–18 Ma) timing to this phase. On the basis of structural measurements and regional considerations we can tentatively separate two deformational events in the late Early to Middle Miocene (18–11 Ma) time span. The older “syn-rift phase” (18–14.5 Ma) is characterized by NE–SW tension and the younger phase is marked by NNW–SSE compression and perpendicular tension. This strike-slip-type stress field with transpressional character formed or reactivated the main dextral faults and associated overturned en echelon folds and thrusts in the Csesznek Zone. The latest, Late Miocene to Pliocene(?) extensional deformational phase (11–3? Ma) segmented the range with normal faults. The newly recognized transpressional character of the Csesznek Zone indicates that a short syn-rift event of the western Pannonian Basin was followed by widespread transpression, as it was also described in other parts of the Transdanubian Range. This transpression can be connected to basin inversion in the easternmost Alps, and important contractional deformation in the eastern Southern Alps, and northernmost Dinarides. The intensity of this transpression was declining to the NE, where the extensional deformation prevailed and was influenced by the subduction still going on along the Eastern Carpathian thrust front.
Paleostress investigation and kinematic analysis along the Telegdi Roth Fault (Bakony Mountains, western Hungary)
Abstract: The Telegdi Roth Fault, a major WNW–ESE fault in the Transdanubian Range, western Hungary is analysed. Fault striation data suggest that the fault and its neighbourhood experienced polyphase brittle deformation from the Senonian, mainly during the Tertiary. The first phase is an Albian–Cenomanian NW–SE thrusting, generating conjugate thrust faults. Then a major sinistral shear due to E–W maximum horizontal stress direction occurred. This main sinistral shear along the Telegdi Roth Fault appears to have occurred between the Senonian and the Early Eocene. This second tectonic event was followed by a dextral strike-slip movement along the fault, due to WNW–ESE maximum horizontal stress. This third movement probably took place from the Middle Eocene to Early Miocene (Eggenburian). Later (after a possible counterclockwise rotation of the Alcapa Unit in the Ottnangian) the deformation detected in the vicinity of the Telegdi Roth Fault was connected to a tensional phase which is characterized by a WSW–ENE minimal stress axis. This movement took place probably in the late Early and early Middle Miocene (Ottnangian to middle Badenian). Related structures are normal and sinistral faults which cut across the Telegdi Roth Fault. The last, fifth identified phase is marked by WNW–ESE minimal horizontal and NNE–SSW maximum horizontal stress directions. The suggested age interval for these deformations is late Middle and Late Miocene (late Badenian to Pannonian). The topographical expression of the main fault and neotectonic observations suggest a probable Quaternary reactivation as well.
Displacements registered around the 13 March 2006 Vrbove earthquake M=3.2 (Western Carpathians)
Abstract: Information is given about the micro-displacement monitoring network in the Dobra Voda epicentral area, where regular monitoring started in May 2004 and an earthquake occurred on 13 March 2006. The measurement is carried out with the use of verified, stable and sensitive 3D crack gauges TM71 produced by GESTRA Sedlonov, Czech Republic. All the gauges installed across significant tectonic structures in this earthquake zone registered displacements pertinent to the said last earthquake. The results obtained within the Dobra Voda (W Slovakia) monitoring network are analysed in view of the 13 March 2006 earthquake. The measurements indicated remaining sinistral strike-slip displacements in the Dobra Voda fault zone, as well as active subsidence of the Pannonian Basin. Moreover, the measurements indicated even more detailed data about the fault movement development during the instability process developing before and after the earthquake.