Search Results (21)

The Eastern Carpathians are thrust to the east and north over their Eastern European foreland, tectonically covering it over an area several hundred kilometers across. Information about the nature of the underthrust part of the Carpathian foreland can be obtained from the rock fragments preserved in the sedimentary successions of the Carpathian fold and thrust belt, specifically in the Outer Dacides and the Moldavides. Fragments of felsic rocks occurring within the sedimentary units of the Upper Cretaceous successions of the Moldavides have long been attributed to the Cuman Cordillera—an intrabasinal ridge in the Eastern Outer Carpathians. This work is the first complex geochemical and geochronological study on the exotic igneous clasts of the Cuman Cordillera. Igneous clasts from the southern part of the Moldavides (Variegated clay nappe/formation) are investigated here. They include mainly granites and rhyolites. Phaneritic rocks are composed of cumulus plagioclase, albite, amphibole and biotite, and intercumulus quartz and potassium feldspar, with apatite, magnetite, sphene, and zircon as main accessories, while the porphyritic rocks have a mineral assemblage similar to that mentioned above, displayed in a porphyritic texture with a usually crystallized groundmass. SHRIMP U-Pb zircon dating indicated the 583–597 Ma age interval for magma crystallization. Based on calcareous nannofossils, the depositional age of the investigated igneous clasts is Cenomanian to Maastrichtian, implying that the Cuman Cordillera was an emerged piece of land, herein an active source of sediments in the flysch basin for at least 40 Ma, from the Early Cretaceous (Aptian) to the Late Cretaceous (Maastrichtian). The intrusive and subvolcanic rocks show similar trends for trace and major elements, evincing their comagmatic nature. The enrichment in LILE and LREE relative to HFSE and HREE, as well as the element anomalies (e.g., negative Nb, Ta, and Eu and positive Rb, Ba, K, and Pb) suggest a convergent continental plate margin tectonic setting. Mineral chemistry suggests magma crystallization in relatively oxic conditions (magnetite series), during ascent within a depth of 15 km to 5 km. The igneous rocks attributed to the Cuman ridge display compositional and geochronological features similar to Brno and Thaya batholiths in the Brunovistulian terrane, which could be a piece of the Carpathian foreland not covered by the Tertiary thrusts. Our data confirm the non-Carpathian origin of the igneous clasts, revealing a Neoproterozoic history of the Carpathian foreland units, which include a Cadomian/Pan-African continental arc, exposed mainly during the Late Cretaceous as an intrabasinal island of the Alpine Tethys, traditionally known as the Cuman Cordillera. Full article

The İspir–Ahlatlı region in northeastern Türkiye, situated within the Eastern Pontides, hosts significant Miocene trachy-andesite volcanic rock exposures. This work seeks to elucidate their petrographic, geochemical, and isotopic compositions to enhance comprehension of their genesis and tectonic significance. Geochemistry reveals a transitional affinity, an enrichment in large-ion lithophile elements (LILEs), and a decrease in high-field-strength elements (HFSEs), suggesting a subduction-modified mantle source. Geochemical variations and fractional crystallisation trends indicate that the parental magma underwent significant differentiation, likely involving the fractionation of amphibole, clinopyroxene, and plagioclase. As supported by recent thermal modelling studies, the presence of intermediate volcanic rocks without associated bimodal suites in the study area may reflect elevated geothermal gradients and lithospheric delamination during post-collisional extension. The signatures indicated that the trachy-andesites originated in a post-collisional extensional environment after the closing of the Neo-Tethys Ocean and the ensuing tectonic reconfiguration of the Eastern Pontides. The reported geochemical traits correspond with post-collisional volcanic phases documented in various sectors of the Alpine–Himalayan orogenic system, such as the Eastern Pontides, the Iranian Plateau, and the Himalayan Belt, reinforcing the notion of a subduction-influenced mantle source. These findings increase the comprehension of magma formation in post-collisional settings and offer novel insights into the geodynamic context of the area. This research improves the understanding of post-collisional volcanic systems, their petrogenetic evolution, and their role in regional tectonic processes. Full article

In the Betic-Rif Cordilleras, recent works have evidenced the existence of well-developed Eocene (Ypresian-Bartonian) carbonate platforms rich in Larger Benthic Foraminifera (LBF). Contrarily to other sectors of the western Tethys, like the Pyrenean domain in the North Iberian Margin, where these platforms started in the early Ypresian (Ilerdian), in the Betic-Rif chains, the recorded Eocene platforms started in the late Ypresian (Cuisian) after a widespread gap of sedimentation including the Ilerdian time span. In this work, the Aspe-Terreros Prebetic section (External Betic Zone) is studied. An Eocene succession with gravity flow deposits consisting of terrigenous and bioclastic turbidites, as well as olistostromes with olistoliths, was detected. In one of these turbidites, we dated (with the inherent limitations when dating bioclasts contained by gravity flow deposits) the middle Ilerdian, on the basis of LBF, representing a vestige of a missing Illerdian carbonate platform. The microfacies of these turbidites and olistoliths rich in LBF have been described and documented in detail. The gap in the sedimentary record and absence of Ilerdian platforms in the Betic-Rif Cordillera have been related to the so-called Eo-Alpine tectonics (Cretaceous to Paleogene) and sea-level variations contemporarily with the establishment of shallow marine realms in the margins of the western Tethys. Full article

It is suggested that the occurrence of tectonic activity in the northern Nubian belts (Tell-Rif and Atlas systems) since the Late Pliocene can be interpreted as one of the processes that were produced in the central and western Mediterranean zones by the collision of the Adriatic continental promontory with the Anatolian–Aegean Tethyan system. Since then, the consumption of the residual low-buoyancy domains in the Mediterranean area was allowed by a major change in the plate mosaic and the related kinematics. The new tectonic setting started with the decoupling of a large portion of the Adriatic domain (Adria plate) from Nubia, through the formation of a long discontinuity crossing the Ionian domain (Victor Hensen–Medina fault) and the Hyblean–Pelagian domain (Sicily channel fault system). Once decoupled, the Adria plate underwent a clockwise rotation, at the expense of E–W shortening in the Hyblean–Pelagian domain and in the northern Nubian margin. The shortening in the Pelagian domain was accommodated by the northward escape of the Adventure wedge, which in turn caused the northward displacement of the eastern Maghrebian sector. The indentation of these structures into the Alpine–Apennine material lying east of the Corsica–Sardinia block induced an east to southeastward escape of wedges (southern Apennines and Calabria). This occured at the expense of the remnant Ionian Tethys oceanic domain and the thinned Adriatic margin. The extensional regime that developed in the wake of the migrating wedges led to the formation of the central and southern Tyrrhenian basins. In the northern Nubian belts, the westward push of the Adria–Hyblean–Pelagian domain has been accommodated by oroclinal bending, thrusting and uplifting across the Tell and Atlas belts. This geodynamic context might explain some features of the seismicity time pattern observed in the Tell system. Full article

This study employed 1D numerical pseudo models to examine the Upper Jurassic carbonate succession, focusing on the Mikulov Formation in the Vienna Basin region. It addresses the protracted and complex history of the Jurassic source rock play, revealing a transition from rapid syn-rift (>200 m/Ma) to slower post-rift sedimentation/subsidence of the overlying layers during extensional deformation (up to 120 m/Ma with a thickness of 1300 m). This provides valuable insights into the rift-to-drift stage of the central Alpine Tethys margin. The Mikulov marls exhibit characteristics of a post-rift passive margin with slow sedimentation rates. However, a crustal stretching analysis using syn-rift heat flow sensitivity suggested that thermal extension of the basement alone cannot fully explain the mid-Jurassic syn-rift stage in this segment of the Alpine Tethys. The sensitivity analysis showed that the mid-late Jurassic differential syn-rift sequences were exposed to slightly cooler temperatures than the crustal stretching model predicted. Heat flow values below 120 mW/m² aligned with measurements from deeply settled Mesozoic successions, suggesting cold but short gravity-driven subsidence. This may account for the relatively low thermal maturation of the primary source rock interval identified by the time-chart analysis, despite the complex tectonic history and considerable sedimentary burial. The post-Mesozoic changes in the compaction trend are possibly linked to the compressional thrusting of the Alpine foreland and postdating listric faulting across the Vienna Basin. Full article

The Yulong porphyry copper belt in eastern Tibet is located in the middle of Tethys–Himalayan metallogenic mega-province, which is one of the three major porphyry copper metallogenic mega-provinces. The Yulong copper belt belongs to the super porphyry copper belt and represents one of the most important copper mineralization prospecting areas in China. A significant quantity of research data shows that this study area belongs to the environment of intracontinental collision and compression, with a complex geological structure, magmatic rock development and excellent metallogenic geological background. However, because this area is located in an alpine and high-altitude area, it is difficult to carry out any traditional field geological surveys, and the existing studies of both prospecting and prediction are relatively weak. This study focused on information extraction for alteration minerals in the Yulong metallogenic belt and its surroundings based on multispectral data and hyperspectral data, establishing a spectral library of alteration minerals in this area. Based on Sentinel-1A radar data and Landsat-8 OLI color synthesis data, the linear structure of the study area was interpreted. On this basis, the information extraction results relating to alteration minerals obtained from multi-source remote sensing data, linear structure interpretation results and the geochemical exploration data of the study area were superimposed to comprehensively analyze the metallogenic geological conditions and mineralization characteristics in the area, establish remote sensing prospecting indicators there and optimize the potential areas for prospecting, providing technical support for the next step of prospecting and exploration in the area. Full article

Hyperextended rift systems are characterized by extreme crustal thinning and mantle exhumation associated with extensional detachment faults. These faults cut through thinned continental crust, reaching the underlying mantle and allowing for seawater to infiltrate and react with the crustal and mantle rocks. Hydrothermal fluid systems linked to detachment faults result in fluid–rock reactions occurring along the detachments, resulting in the breakdown and alteration of minerals, loss of elements and strain weakening in both mantle and crustal rocks. We present new geological observations and geochemical data from the modern Iberia and fossil Alpine Tethys Ocean Continent Transition and the West Pyrenean Mauléon hyperextended rift basin. We show evidence for a km-scale fluid flow along detachment faults and discuss the conditions under which fluid flow and mass transfer occurred. Convective fluid systems are of major importance for mass transfer between the mantle, crustal and marine reservoirs. We identified gains in Si, Mg, Fe, Mn, Ca, Ni, Cr and V along extensional detachment faults that we relate to channelized, hydrothermal crust- and mantle-reacted fluid systems migrating along detachments in the hyperextended continental crust. The observation that fault rocks of extensional detachment and syn-extensional sedimentary rocks are enriched in mantle-derived elements such as Cr, Ni and V enables us to define the pathways of fluids, as well as to estimate their age relative to detachment faulting and sedimentation. Because all three examples show a similar mass transport of elements along detachment systems at km-scale, we conclude that these examples are linked to convective fluid systems that may affect the thermal state of the lithosphere, as well as the rheology and chemistry of rocks in hyperextended systems, and may have implications for ore mineral exploration in hyperextended rift systems. Full article

We reassess the architecture and tectonic history of the Western Alps based on recent knowledge developed at rifted margins. First, we replace the main Alpine units of our study area into a synthetic rifted margin template based on diagnostic petrologic, stratigraphic, and structural criteria. We find that some units previously attributed to the internal part of the thick-crusted Briançonnais domain may rather derive from the thin-crusted Prepiemonte hyperextended domain. We assert that the Briançonnais and Prepiemonte domains were separated by a mega-fault scarp. Second, we revisit the Paleogeography of the Alpine Tethys, suggesting that the Briançonnais was a ribbon of little thinned continental crust between two overstepping en-échelon rift basins, namely the Valais domain to the northwest and the Piemonte domain to the southeast. We affirm that this uneven-margin architecture can explain most of the Western Alps’ complexity. In our kinematic model, convergence between Adria and Europe was mainly accommodated by strike-slip movements in the Western Alps until the late Eocene. Orogeny began with the reactivation of the mega-fault scarp between the Briançonnais and Prepiemonte domains, which we name Prepiemonte Basal Thrust. Once hard collision started, the main shortening stepped inboard into the Valais/Subbriançonnais domain along the Penninic Basal Thrust. Full article

Geological mapping, stratigraphic observations, and U/Pb dating allow reconstructing the pre-orogenic setting of the transition zone between the distal European passive margin and the Alpine Tethys in the southwestern Alps. Although convergent tectonics overprinted the syn-rift Jurassic tectonic features, our data document an articulated Jurassic physiography. From the distal European passive margin oceanward, we distinguished: the Dronero Unit (the southernmost Dora Maira massif), represents a continental margin composite basement wherein monometamorphic metasediments are interlayered with Late Permian (253.8 ± 2.7 Ma) metavolcanic rocks; the Sampeyre Unit, represents a structural high consisting of Lower Triassic Verrucano-facies siliciclastic metasediments unconformably sealed by Cretaceous calcschist bearing Globotruncana sp.; the Maira Unit, corresponds to a Middle Triassic platform succession detached from the Sampeyre Unit; the Grana Unit, corresponds to a Late Triassic–Late Jurassic platform to basin succession; the Queyras Schistes Lustrès Complex, represents the ocean basin succession. Tectonic slices of Cambrian (513.9 ± 2.7 Ma) metadiorite hosted in the Valmala Shear Zone, separating the Dronero Unit from the underlying (U)HP units of the Dora Maira massif, suggests a potential pre-Alpine activation of the shear zone. Full article

The Pieniny Klippen Belt (PKB) is located in the suture zone between the Central and Outer (Flysch) Carpathians. Its structure is an effect of prolonged processes of the Cretaceous–Miocene folding, thrusting and uplifting. In this zone, tectonic components of different ages and features, including strike-slip-bounded tectonic blocks, thrust units, as well as toe-thrusts and olistostromes, result in the present-day mélange characteristics of the PKB, where individual tectonic units are difficult to distinguish. In the PKB, both tectonic and sedimentary events triggered the mélange creation. The name “Klippen Belt” is derived from cliffs (German Klippen). These cliffs form harder, more erosion-resistant elements of the mélange, residing within less competent clastic deposits, sandstones, shales and marls that form flysch complexes. The cliffs often represent olistoliths, which glided down from elevated areas to the deeper basinal zones. Two olistostrome belts were distinguished. The older one resulted from subduction of the southern part of the Alpine Tethys, and the younger originated in response to the northward shift of the accretionary wedge. The other cliffs were placed within the surrounding clastic by tectonic deformational processes. The flower structure of the PKB was formed during the collision and strike-slip movement of the lithospheric plates. This structure is limited on both sides by deep-rooted faults. Several evolutionary stages could be distinguished in these areas. The rift-related stage is expressed by the opening of the Alpine Tethys that contains two major basins—Magura and Pieniny (Złatne) basins, separated by Czorsztyn Ridge. The reorganization of the Alpine Tethys basins and the development of the accretionary prism happened during the synorogenic stage. This process was initiated by the movement of the Central Carpathians. Thick flysch sequences with olistostromes were deposited in these basins. The Czorsztyn Ridge was destroyed during the late orogenic stages. Full article

This study investigates the Paleogene deep-water depositional system of the Gosau Group at Gams, Styria (Austria). The examined sections of the Danian to the Ypresian age (NP1–NP12) comprise sediments of the Nierental and Zwieselalm Formations. Four deep-water clastic facies assemblages were encountered: (1) pelagic marls with thin turbidites, (2) carbonate-rich turbidites, (3) carbonate-poor turbidites, and (4) marl-bearing turbidites; slump beds and mass flow deposits are common features in all facies assemblages. Based on heavy mineral, thin section, microprobe, and paleoflow analyses, provenance was from the surrounding Northern Calcareous Alps (NCA) rocks and exhuming metamorphic Upper Austroalpine units to the south. In addition, biogenic calcareous material was delivered by adjacent contemporaneous shelf zones. The sedimentary depocenter was situated at the slope of the incipient Alpine orogenic wedge, in frontal parts of the NCA, facing the subducting Penninic Ocean/Alpine Tethys. The evolution of the Gams Basin was connected to the eoalpine and mesoalpine orogeny and the adjunctive transpressional setting. The Gams deep-water depositional system is interpreted as an aggrading or prograding submarine fan, deposited into a small confined slope basin, positioned along an active continental margin, bound and influenced by (strike-slip) faults, related to crustal shortening. The development of the Gams slope basin and its infilling sequences was mainly dominated by tectonism and sediment supply, rather than by eustatic sea-level fluctuations. The basin was cut off during the Eocene due to renewed orogeny. A Quaternary analogue for the Upper Cretaceous to Paleogene basin setting of the Gams area is represented by the Santa Monica Basin in the California Continental Borderland. Full article

The Corno Alto–Monte Ospedale magmatic complex crops out at the eastern border of the Adamello batholith, west of the South Giudicarie Fault (NE Italy). This complex includes tonalites, trondhjemites, granodiorites, granites and diorites exhibiting an unfoliated structure suggesting passive intrusion under extensional-to-transtensional conditions. Major, minor elements, REE and isotopic analyses and geochemical and thermodynamic modelling have been performed to reconstruct the genesis of this complex. Geochemical analyses unravel a marked heterogeneity with a lack of intermediate terms. Samples from different crust sections were considered as possible contaminants of a parental melt, with the European crust of the Serre basement delivering the best fit. The results of the thermodynamic modelling show that crustal melts were produced in the lower crust. Results of the geochemical modelling display how Corno Alto felsic rocks are not reproduced by fractional crystallization nor by partial melting alone: their compositions are intermediate between anatectic melts and melts produced by fractional crystallization. The tectonic scenario which favored the intrusion of this complex was characterized by extensional faults, active in the Southalpine domain during Eocene. This extensional scenario is related to the subduction of the Alpine Tethys in the Eastern Alps starting at Late Cretaceous time. Full article

Tectonic activity in the Mediterranean area (involving migrations of old orogenic belts, formation of basins and building of orogenic systems) has been determined by the convergence of the confining plates (Nubia, Arabia and Eurasia). Such convergence has been mainly accommodated by the consumption of oceanic and thinned continental domains, triggered by the lateral escapes of orogenic wedges. Here, we argue that the implications of the above basic concepts can allow plausible explanations for the very complex time-space distribution of tectonic processes in the study area, with particular regard to the development of Trench-Arc-Back Arc systems. In the late Oligocene and lower–middle Miocene, the consumption of the eastern Alpine Tethys oceanic domain was caused by the eastward to SE ward migration/bending of the Alpine–Iberian belt, driven by the Nubia–Eurasia convergence. The crustal stretching that developed in the wake of that migrating Arc led to formation of the Balearic basin, whereas accretionary activity along the trench zone formed the Apennine belt. Since the collision of the Anatolian–Aegean–Pelagonian system (extruding westward in response to the indentation of the Arabian promontory) with the Nubia-Adriatic continental domain, around the late Miocene–early Pliocene, the tectonic setting in the central Mediterranean area underwent a major reorganization, aimed at activating a less resisted shortening pattern, which led to the consumption of the remnant oceanic and thinned continental domains in the central Mediterranean area. Full article

The composite Albian–Eocene orogenic wedge of the northern part of the Inner Western Carpathians (IWC) comprises the European Variscan basement with the Upper Carboniferous–Triassic cover and the Jurassic to Upper Cretaceous sedimentary successions of a large oceanic–continental Atlantic (Alpine) Tethys basin system. This paper presents an updated evolutionary model for principal structural units of the orogenic wedge (i.e., Fatricum, Tatricum and Infratatricum) based on new and published white mica ⁴⁰Ar/³⁹Ar geochronology and P–T estimates by Perple_X modeling and geothermobarometry. The north-directed Cretaceous collision led to closure of the Jurassic–Early Cretaceous basins, and incorporation of their sedimentary infill and a thinned basement into the Albian–Cenomanian/Turonian accretionary wedge. During this compressional D1 stage, the subautochthonous Fatric structural units, including the present-day higher Infratatric nappes, achieved the metamorphic conditions of ca. 250–400 °C and 400–700 MPa. The collapse of the Albian–Cenomanian/Turonian wedge and contemporary southward Penninic oceanic subduction enhanced the extensional exhumation of the low-grade metamorphosed structural complexes (D2 stage) and the opening of a fore-arc basin. This basin hemipelagic Coniacian–Campanian Couches-Rouges type marls (C.R.) spread from the northern Tatric edge, throughout the Infratatric Belice Basin, up to the peri-Pieniny Klippen Belt Kysuca Basin, thus tracing the south-Penninic subduction. The ceasing subduction switched to the compressional regime recorded in the trench-like Belice “flysch” trough formation and the lower anchi-metamorphism of the C.R. at ca. 75–65 Ma (D3 stage). The Belice trough closure was followed by the thrusting of the exhumed low-grade metamorphosed higher Infratatric complexes and the anchi-metamorphosed C.R. over the frontal unmetamorphosed to lowest anchi-metamorphosed Upper Campanian–Maastrichtian “flysch” sediments at ca. 65–50 Ma (D4 stage). Phengite from the Infratatric marble sample SRB-1 and meta-marl sample HC-12 produced apparent ⁴⁰Ar/³⁹Ar step ages clustered around 90 Ma. A mixture interpretation of this age is consistent with the presence of an older metamorphic Ph1 related to the burial (D1) within the Albian–Cenomanian/Turonian accretionary wedge. On the contrary, a younger Ph2 is closely related to the late- to post-Campanian (D3) thrust fault formation over the C.R. Celadonite-enriched muscovite from the subautochthonous Fatric Zobor Nappe meta-quartzite sample ZI-3 yielded a mini-plateau age of 62.21 ± 0.31 Ma which coincides with the closing of the Infratatric foreland Belice “flysch” trough, the accretion of the Infratatricum to the Tatricum, and the formation of the rear subautochthonous Fatricum bivergent structure in the Eocene orogenic wedge. Full article

Ophiolites of the Alpine belt derive from the closure of the Mesozoic Tethys Ocean that was interposed between the palaeo-Europe and palaeo-Adria continental plates. The Alpine orogeny has intensely reworked the oceanic rocks into metaophiolites with various metamorphic imprints. In the Western Alps, metaophiolites and continental-derived units are distributed within two paired bands: An inner band where Alpine subduction-related high-pressure (HP) metamorphism is preserved, and an outer band where blueschist to greenschist facies recrystallisation due to the decompression path prevails. The metaophiolites of the inner band are hugely important not just because they provide records of the prograde tectonic and metamorphic evolution of the Western Alps, but also because they retain the signature of the intra-oceanic tectono-sedimentary evolution. Lithostratigraphic and petrographic criteria applied to metasediments associated with HP metaophiolites reveal the occurrence of distinct tectono-stratigraphic successions including quartzites with marbles, chaotic rock units, and layered calc schists. These successions, although sliced, deformed, and superposed in complex ways during the orogenic stage, preserve remnants of their primary depositional setting constraining the pre-orogenic evolution of the Jurassic Tethys Ocean. Full article