ALBERT

Description: We have carried out radioelemental ( 232 Th, 238 U, 40 K), petrological and geochemical analyses on granitoids and gneisses covering major rock formations of the Bundelkhand craton, central India. Our data reveal that above characteristics are distinct among granitoids (i.e. pink, biotite and grey granitoids) and gneisses (i.e. potassic and sodic types). Pink granitoid is K-feldspar-rich and meta-aluminous to per-aluminous in character. Biotite granitoid is meta-aluminous in character. Grey granitoid is rich in Na-feldspar and mafic minerals, granodiorite to diorite in composition and meta-aluminous in character. Among these granitoids, radioelements (Th, U, K) are highest in pink granitoid (45.0 ± 21.7 ppm, 7.2 ± 3.4 ppm, 4.2 ± 0.4 %), intermediate in biotite granitoid (44.5 ± 28.2 ppm, 5.4 ± 2.8 ppm, 3.4 ± 0.7 %) and lowest in grey granitoid (17.7 ± 4.3 ppm, 4.4 ± 0.6 ppm, 3.0 ± 0.4 %). Among gneisses, potassic-type gneisses have higher radioelements (11.8 ± 5.3 ppm, 3.1 ± 1.2 ppm, 2.0 ± 0.5 %) than the sodic-type gneisses (5.6 ± 2.8 ppm, 1.3 ± 0.5 ppm, 1.4 ± 0.7 %). Moreover, the pink granitoid and the biotite granitoid have higher Th/U (6 and 8, respectively) compared to the grey granitoid (Th/U: 4), implying enrichment of Th in pink and biotite granitoids relative to grey granitoid. K/U among pink, biotite and grey granitoids shows little variation (0.6 × 10 4 , 0.6 × 10 4 , 0.7 × 10 4 , respectively), indicating relatively similar increase in K and U. Therefore, mineralogical and petrological data along with radioelemental ratios suggest that radioelemental variations in these lithounits are mainly related to abundances of the radioactive minerals that have formed by the fractionation of LILE from different magma sources. Based on present data, the craton can be divided into three distinct zones that can be correlated with its evolution in time and space. The central part, where gneisses are associated with metavolcanics of greenstone belt, is characterized by lowest radioelements and is the oldest component. The southern part, dominated by pink granitoid, is characterized by highest radioelements and is the youngest part. The northern part, dominated by grey and biotite granitoid, is characterized by moderate radioelements.

Description: Dykes in the Strudengau area (SW Moldanubian Zone, Austria) can be mineralogically divided into lamprophyres (spessartites and kersantites) and felsic dykes (granite porphyries, granitic dykes and pegmatoid dykes). Geochemical analyses of 11 lamprophyres and 7 felsic dykes show evidence of fractional crystallization. The lamprophyres are characterized by metaluminous compositions, intermediate SiO 2 contents and high amounts of MgO and K 2 O; these rocks have high Ba (800–3000 ppm) and Sr (250–1000 ppm) contents as well as an enrichment of large-ion lithophile elements over high field strength elements, typical for enriched mantle sources with variable modifications due to fractionation and crustal contamination. This geochemical signature has been reported from durbachites (biotite- and K feldspar-rich mela-syenites particularly characteristic of the Variscan orogen in Central Europe). For most major elements, calculated fractionation trends from crystallization experiments of durbachites give an excellent match with the data from the Strudengau dykes. This suggests that the lamprophyres and felsic dykes were both products of fractional crystallization and subsequent magma mixing of durbachitic and leucogranitic melts. Rb–Sr geochronological data on biotite from five undeformed kersantites and a locally deformed granite porphyry gave cooling ages of c. 334–318 Ma, indicating synchronous intrusion of the dykes with the nearby outcropping Weinsberger granite (part of the South Bohemian Batholith, c. 330–310 Ma). Oriented matrix biotite separated from the locally deformed granite porphyry gave an Rb–Sr age of c. 318 Ma, interpreted as a deformation age during extensional tectonics. We propose a large-scale extensional regime at c. 320 Ma in the Strudengau area, accompanied by plutonism of fractionated magmas of syncollisional mantle-derived sources, mixed with crustal components. This geodynamic setting is comparable to other areas in the Variscan belt documenting an orogenic wide extension by the end of the Carboniferous.

Description: Dolomitization of relatively thick carbonate successions occurs via an effective fluid circulation mechanism, since the replacement process requires a large amount of Mg-rich fluid interacting with the CaCO 3 precursor. In the western end of the Neotethys, fault-controlled extensional basins developed during the Late Triassic spreading stage. In the Buda Hills and Danube-East blocks, distinct parts of silica and organic matter-rich slope and basinal deposits are dolomitized. Petrographic, geochemical, and fluid inclusion data distinguished two dolomite types: (1) finely to medium crystalline and (2) medium to coarsely crystalline. They commonly co-occur and show a gradual transition. Both exhibit breccia fabric under microscope. Dolomite texture reveals that the breccia fabric is not inherited from the precursor carbonates but was formed during the dolomitization process and under the influence of repeated seismic shocks. Dolomitization within the slope and basinal succession as well as within the breccia zones of the underlying basement block is interpreted as being related to fluid originated from the detachment zone and channelled along synsedimentary normal faults. The proposed conceptual model of dolomitization suggests that pervasive dolomitization occurred not only within and near the fault zones. Permeable beds have channelled the fluid towards the basin centre where the fluid was capable of partial dolomitization. The fluid inclusion data, compared with vitrinite reflectance and maturation data of organic matter, suggest that the ascending fluid was likely hydrothermal which cooled down via mixing with marine-derived pore fluid. Thermal gradient is considered as a potential driving force for fluid flow.

Description: LA-MC-ICP-MS U–Pb zircon ages and whole-rock geochemical data obtained from volcanic rocks erupted in the northern margin of Gondwana provide new insights on the polyphase magmatic evolution of the NW Iberian domain during the establishment of passive margin conditions in Lower Paleozoic times. The U–Pb data show crystallization ages of ca. 455 Ma for two calc-alkaline rhyolites sampled in the Upper Parautochthon of the eastern Galicia—Trás-os-Montes Zone (GTMZ) and for an intraplate basalt intruded into Middle Ordovician slates of the autochthonous series of the Central Iberian Zone (CIZ). Together with previous data, the ages obtained reveal a periodic magmatic activity across the northern Gondwana margin during the Lower Paleozoic, which is comparable to that observed in NE Iberia and in other massifs of the Mediterranean realm. Both geochronological and geochemical data reinforce paleontological and stratigraphic evidences for paleogeographic proximity between these domains and contribute to the recognition of extensional-related magmatism along the northern margin of Central Gondwana associated with the opening of the Rheic Ocean.

Description: Extrusion by Poiseuille flow and simple shear of hot lower crust has been deciphered from large hot orogens, and partial-slip boundary condition has been encountered in analogue models. Shear heat and velocity profiles are deduced from a simplified form of Navier–Stokes equation for simple shear together with extrusive Poiseuille flow and slip boundary condition for Newtonian viscous rheology. A higher velocity at the upper boundary of the shear zone promotes higher slip velocity at the lower boundary. The other parameters that affect the slip are viscosity and thickness of the shear zone and the resultant pressure gradient that drives extrusion. In the partial-slip case, depending on flow parameters (resultant pressure gradient, density and viscosity) and thickness of the shear zone, the velocity profiles can curve and indicate opposite shear senses. The corresponding shear heat profiles can indicate temperature maximum inside shear zones near either boundaries of the shear zone, or equidistant from them.

Description: The Kağızman-Tuzluca Basin is located in the northeastern Anatolia, to the east of the intersection point (near Karlıova) of the major North and East Anatolian Fault systems. This intermontane basin displays a thick sequence (over 2000 m) of mostly terrestrial deposits represented by repetitive alternations of the lake and fluvial environments ranging from ?Late Eocene/Oligocene to Middle/? Late Miocene. A marine incursion only mappable in the southeastern margin of the basin deposited limestones and sandy limestones rich in marine mollusks and nummulites, in particular N. fichteli that constrain an Early Oligocene age for this marine unit (Kağan Fm). The terrestrial basin-fill deposits show different thicknesses throughout the basin due to irregular bottom topography and tectonic configuration of the basin margins. The thickest deposits were accumulated along the different margins of the basin, which received high quantities of siliciclastics from meandering river, alluvial and coastal fans, fan delta/Gilbert-type delta and wave-worked fluvial delta. Climate changes have also driven the development of lake environments during distinct depositional periods. Siliciclastic-dominated overfilled lakes (Halıkışlak and Kızılkaya formations) and chemical-dominated underfilled lakes (Turabi and Tuzluca formations) were formed. They have been also classified as “Newark-type” and “Fundy-type” lakes, respectively. Fluvial systems evolved from high-energy meandering rivers deposited under humid climate (Güngören Formation) to low-energy meandering rivers resulted from arid and semiarid climates (Çincavat Formation). The transitional intervals from ephemeral river-dry mudflat (Çincavat Formation) to saline pan/lake (Tuzluca Formation) indicate wadi-sand flat-playa fluvial systems. The chronostratigraphic constrains of the entire sequence remain poor and so far solely based on vertebrate fossil assemblages. The evaporitic Tuzluca Formation would be Middle Miocene in age due to its stratigraphic position over the Çincavat Formation.

Description: New data from the Mw 5.4 earthquake on 17 November 2014 in the vicinity of Athens and its seismic electric signal (SES) precursor confirm patterns of criticality in the pre-seismic region during the last preparatory phase. In detail, the stress drop of the main shock and the lead time of the associated SES are interconnected through a power law with an exponent a  = 0.327 falling in the range of critical exponents for fracture. We note that this exponent is derived from a large amount of data and successfully passes the z -score statistical test. This fact supports the hypothesis that upon the emission of the SES the pre-focal area enters a critical stage where nonlinear dynamic processes dominate.

Description: The area of contact between Precambrian and Phanerozoic Europe in Poland has complicated structure of sedimentary cover and basement. The thinnest sedimentary cover in the Mazury-Belarus anteclize is only 0.3–1 km thick, increases to 7–8 km along the East European Craton margin, and 9–12 km in the Trans-European Suture Zone (TESZ). The Variscan domain is characterized by a 1- to 2-km-thick sedimentary cover, while the Carpathians are characterized by very thick sediments, up to c. 20 km. The map of the basement depth is created by combining data from geological boreholes with a set of regional seismic refraction profiles. These maps do not provide data about the basement depth in the central part of the TESZ and in the Carpathians. Therefore, the data set is supplemented by 32 models from deep seismic sounding profiles and a map of a high-resistivity (low-conductivity) layer from magnetotelluric soundings, identified as a basement. All of these data provide knowledge about the basement depth and of P-wave seismic velocities of the crystalline and consolidated type of basement for the whole area of Poland. Finally, the differentiation of the basement depth and velocity is discussed with respect to geophysical fields and the tectonic division of the area.

Description: In the Hellenides of northern Greece, the Kassandra–Sithonia and Central Chalkidiki ophiolites constitute the Vardar suture zone against the Serbo-Macedonian margin of Eurasia. The mafic-intermediate to acid members in the crustal section of the Kassandra–Sithonia ophiolites have N- and E-MORB signatures compatible with an origin in a back-arc spreading center. The MORB mantle source has received subduction zone input from the nearby Paikon arc system as revealed by LILE and LREE enrichments. A diorite from the Gerakini complex presumably belonging to the Central Chalkidiki ophiolites shows more enriched HFSE and REE patterns relative to MORB and Na-rich character compared to the Kassandra–Sithonia ophiolites. The Sithonia ophiolite crystallization spans from 159 to 149 Ma, and the Gerakini complex diorite crystallized at 173 Ma as derived from new U–Pb zircon geochronology. The main cluster of Permo-Carboniferous, a small cluster of Neoproterozoic–Cambrian and few Proterozoic, Ordovician, Devonian, Triassic and Middle Jurassic inherited zircons derive from the Serbo-Macedonian margin units. Thus, a Late Jurassic ca. 10 Ma lasting igneous accretion of the Kassandra–Sithonia back-arc crust within the eastern Vardar zone is now well constrained and corroborated by Berriasian–Early Valanginian supra-ophiolite cover limestones. Instead of an affinity to the Central Chalkidiki ophiolites, the Gerakini diorite exhibits chemical similarity to the Chortiatis arc magmatic suite of the Circum-Rhodope belt within the eastern Vardar zone. The Gerakini diorite predates the Sithonia ophiolite in which the Chortiatis arc suite supplied Middle Jurassic inherited zircons. The Chortiatis arc compared with arc-related Evros ophiolites of the Circum-Rhodope belt in Thrace region shows the same 173–160 Ma life span and tectonic setting, implying the extension of the arc systems across the north Aegean Sea. Based on these new temporal constraints, a tectonic scenario of Jurassic subduction settings and arc/back-arc systems development in the Maliac and Vardar oceanic basins is proposed that also accounts for continental magmatism in the Serbo-Macedonian margin of Eurasia.

Description: This is the first study presenting major and trace elemental data from the Mesoproterozoic Hongshuizhuang Formation shales in Yanshan basin, North China, in order to reconstruct its provenance and chemical weathering history. The shales are strongly depleted in Na 2 O and Sr and enriched in Y and transition metal elements relative to upper continental crust. Low Zr concentrations and various discriminant plots (e.g., Th/Sc–Zr/Sc and Al 2 O 3 –TiO 2 –Zr) indicate insignificant mineral sorting or recycling of these shales. The rocks show light rare earth element (REE) enrichment (La/Yb CN  = 3.99–6.92), flat heavy REE, and significantly negative Eu anomalies (Eu an  = 0.57–0.68) in chondrite-normalized REE patterns, similar to post-Archean Australian average shales. The fairly uniform REE patterns and trace element ratios indicate that the Hongshuizhuang Formation shales were derived from a felsic source area with granodiorite as the dominant contributor. Mixing calculations suggest a mixture of 30 % granite porphyry, 5 % basalt, and 65 % granodiorite as the possible source of the shales, also supporting that granodiorite was the predominant source. Intense chemical weathering of the source terrain is indicated by high values of the premetasomatized chemical index of alteration, plagioclase index of alteration, Rb/Sr, a strong positive correlation between TiO 2 and Al 2 O 3 , depletion of CaO, Na 2 O, and Sr, and mineral compositions. Such strong chemical weathering suggests a warm and wet paleoclimate, perhaps due to high atmospheric CO 2 and CH 4 concentrations, and a near-equatorial location of the North China Craton in the Columbia supercontinent at 1.4 Ga.

Description: Here we present a detailed investigation into the geochemistry and the excavational/depositional processes involved in the maar-diatreme forming Finca la Nava (FlN) eruption in south-central Spain. Bulk rock compositions of hand-picked juvenile fragments indicate derivation of the FIN magma from a garnet-bearing mantle source, which has subsequently been overprinted in bulk rock samples by incorporation of a combination of spinel-bearing peridotites and upper-crustal lithics (i.e. quartzites and slates). The dominating phenocryst assemblage with clinopyroxene, olivine, amphibole and phlogopite points to the classification of the juvenile magma as being olivine melilititic in composition. Ascent through the lithosphere was rapid as indicated by the calculations of settling rates of mantle peridotites (~0.8 m s −1 ). The original magma fragmentation level in the conduit was probably relatively shallow carrying mainly juvenile pyroclasts (~60 %) intermixed with accidental crustal lithics (~35 %) and mantle xenoliths (〈5 %) to the surface. The shapes of individual pyroclasts are sub-rounded to rounded and with highly variable vesicularities (5–45 %). This fact, in combination with abundant fine-grained material in the beginning of the eruption, indicates that both magmatic and phreatomagmatic fragmentation processes may have played important roles in forming the FIN maar. A relatively constant increase in quartzitic fragments from ~35 to 〈60 % with increasing stratigraphic height in the FIN deposits further indicates that the crater area successively widened during the eruption, which resulted in an increased recycling of quartzitic fragments. This eruption scenario, with the formation of a diatreme at depth, is also consistent with the absence of layers dipping inwards into the crater area.

Description: Deccan basaltic glass is associated with the differentiation centres of the vast basaltic magmas erupted in a short time span. Its suitability as a radioactive waste containment chiefly depends on alteration behaviour; however, detailed work is needed on this glass. Therefore, the basaltic glass was treated under hydrothermal-like conditions and then studied to understand its alteration. Moreover, comparison of these results with the naturally altered glass is also documented in this paper. Solutions as well as residue obtained after glass alteration experiments were analysed. Treated glass specimens show partial to complete release of all the ions during alteration; however, abundant release of Si and Na ions is noticed in case of almost all the specimens and the ionic release is of the order of Na 〉 Si 〉 K 〉 Ca 〉 Al = Mg 〉 Fe 〉 Mn 〉 Ti. Scanning electron images of the altered residue show morphologies of smectite, montmorillonite and illite inside as well as outside of the secondary layers, and represent paragenesis of alteration minerals. It has been noticed that the octahedral cation occupancies of smectite are consistent with the dioctahedral smectite. The secondary layer composition indicates retention for Si, Al, and Mg ions, indicating their fixation in the alteration products, but remarkably high retention of Ti, Mn and Fe ions suggests release of very small amount of these elements into the solution. By evolution of the secondary layer and retention of less soluble ions, the obstructive effect of the secondary layer increases and the initial constant release rate begins slowly to diminish with the proceeding time. It has been found that devitrification of glass along the cracks, formation of spherulite-like structures and formation of yellowish brown palagonite, chlorite, calcite, zeolite and finally white coloured clays yielded after experiments that largely correspond to altered obsidian that existed in the natural environment since inception ~66 Ma ago.

Description: In the central Upper Rhine Graben (URG), several major oil fields have been sourced by Liassic Black Shales. In particular, the Posidonia Shale (Lias ε, Lower Toarcian) acts as excellent and most prominent source rock in the central URG. This study is the first comprehensive synthesis of Liassic maturity data in the URG area and SW Germany. The thermal maturity of the Liassic Black Shales has been analysed by vitrinite reflectance (VR r ) measurements, which have been verified with T max and spore coloration index (SCI) data. In outcrops and shallow wells (〈600 m), the Liassic Black Shales reached maturities equivalent to the very early or early oil window (ca. 0.50–0.60 % VR r ). This maturity is found in Liassic outcrops and shallow wells in the entire URG area and surrounding Swabian Jura Mountains. Maximum temperatures of the Posidonia Shale before graben formation are in the order of 80–90 °C. These values were likely reached during Late Cretaceous times due to significant Upper Jurassic and minor Cretaceous deposition and influenced by higher heat flows of the beginning rift event at about 70 Ma. In this regard, the consistent regional maturity data (VR r , T max , SCI) of 0.5−0.6 % VR r for the Posidonia Shale close to surface suggest a major burial-controlled maturation before graben formation. These consistent maturity data for Liassic outcrops and shallow wells imply no significant oil generation and expulsion from the Posidonia Shale before formation of the URG. A detailed VR r map has been created using VR r values of 31 wells and outcrops with a structure map of the Posidonia Shale as reference map for a depth-dependent gridding operation. Highest maturity levels occur in the area of the Rastatt Trough (ca. 1.5 % VR r ) and along the graben axis with partly very high VR r gradients (e.g. well Scheibenhardt 2). In these deep graben areas, the maximum temperatures which were reached during upper Oligocene to Miocene times greatly exceed those during the Cretaceous.

Description: This paper deals with the provenance analysis of the Neogene foreland basin sediments of the Siwalik Group in the Nepal Himalaya. This study adopts the techniques of the optical petrography and detrital zircon U–Pb ages from two river sections: the Koshi Nadi in eastern Nepal and the Surai Khola in western Nepal Himalaya. The optical petrography data and resulting QFL plot show a “recycled orogeny” field for the studied sandstone samples, indicating northern lithotectonic units; Tethys Himalaya, Higher Himalaya and Lesser Himalaya as the source of the foreland basin sediments. The detrital zircon geochronological data set has clearly revealed that the cluster ages are younger than ~1000 Ma; however, the older grains (〉1000 Ma) are significantly fewer. The obtained age spectrum is similar to the Tethys Himalaya and the upper Lesser Himalaya, but the lower Lesser Himalayan rocks were not distinct, which indicates that sediments in the Neogene foreland basin of the Nepal Himalaya were primarily sourced from the Tethys Himalaya and upper Lesser Himalaya. The minor subordinate scattered peaks that roughly correspond to the age of the Higher Himalaya and lower Lesser Himalaya may indicate that a lower proportion of the sediments might have a link with the Higher Himalaya and lower Lesser Himalaya. Therefore, the provenance of the Siwalik Group in the Nepal Himalaya might have witnessed a mixed type of provenance similar to the northwestern Himalaya.

Description: Evidence of rifting and continental break-up to form the S Neotethys is found within the volcanic-sedimentary Koçali Complex. This is a folded, thrust-imbricated succession that includes lavas, volcaniclastic sediments, pelagic carbonates, radiolarites and manganiferous deposits. Interbedded ribbon cherts contain radiolarians of Late Triassic to Late Jurassic age. The lower part of the succession of Mid?-Late Triassic age (Tarasa Formation) is dominated by enriched mid-ocean ridge basalt (E-MORB). The overlying Late Triassic to Mid-Jurassic interval (Konak Formation) is characterised by intercalations of ocean island basalt and E-MORB. Taking account of structural position, the basalts erupted within the outer part of a continent–ocean transition zone. Continental break-up probably occurred during the Late Triassic (Carnian–Norian). Early to Mid-Jurassic lavas and volcaniclastic sediments record volcanism probably after continental break-up. In addition, the Karadut Complex is a broken formation that is located at a relatively low structural position just above the Arabian foreland. Pelagic carbonates, redeposited carbonates and radiolarites predominate. Radiolarians are dated as Early to Mid-Jurassic and Late Cretaceous in age. The pelagic carbonates include planktic foraminifera of Late Cretaceous age. The Karadut Complex resulted from the accumulation of calcareous gravity flows, pelagic carbonate and radiolarites in a relatively proximal, base-of-slope setting. After continental break-up, MORB and ophiolitic rocks formed within the S Neotethys further north. Tectonic emplacement onto the Arabian platform took place by earliest Maastrichtian time. Regional interpretation is facilitated by comparisons with examples of Triassic rifting and continental break-up in the eastern Mediterranean region and elsewhere.

Description: A portion of the Kosi River in the outer Kumaun Lesser Himalaya is characterized by wide river course situated south of the Ramgarh Thrust, where huge thickness (~200 m) of the landslide deposits and two to three levels of unpaired fan terraces are present. Brittle normal faults, suggesting extensional tectonics, are recognized in the Quaternary deposits and bedrocks as further supported by surface morphology. Trending E–W, these faults measure from 3 to 5 km in length and are traced as discontinuous linear mini-horst and fault scarps (sackungen) exposed due to cutting across by streams. Active normal faults have displaced the coarsely laminated debris fan deposits at two sites located 550 m apart. At one of the sites, the faults look like bookshelf faulting with the maximum displacement of ~2 m and rotation of the Quaternary boulders along the fault plane is observed. At another site, the maximum displacement measures about 0.60 cm. Thick mud units deposited due to blocking of the streams by landslides are observed within and above the fan deposit. Landslide debris fans and terrace landforms are widely developed; the highest level of fan is observed ~1240 m above mean sea level. At some places, the reworking of the debris fans by streams is characterized by thick laminated sand body. Along the South Almora Thrust and Ramgarh Thrust zones, the valleys are narrow and V-shaped where Quaternary deposits are sparse due to relatively rapid uplift across these thrusts. Along the South Almora Thrust zone, three to four levels of fluvial terraces are observed and have been incised by river exposing the bedrocks due to recent movement along the RT and SAT. Abandoned channel, tilted mud deposits, incised meandering, deep-cut V-shaped valleys and strath terraces indicate rapid uplift of the area. Thick mud sequences in the Quaternary columns indicate damming of streams. A ~10-km-long north–south trending transverse Garampani Fault has offset the Ramgarh Thrust producing tectonic landforms.

Description: A 3D imaging of S-velocity for the Arabian Sea crust and upper mantle structure is presented in this paper, determined by means of Rayleigh wave analysis, for depths ranging from zero to 300 km. The crust and upper mantle structure of this region of the earth never has been the subject of a surface wave tomography survey. The Moho map performed in the present study is a new result, in which a crustal thickening beneath the Arabian Fan sediments can be observed. This crustal thickening can be interpreted as a quasi-continental oceanic transitional structure. A crustal thickness of up to 20 km also can be observed for the Murray Ridge system in this Moho map. This crustal thickening can be due to that the Murray Ridge System consists of Indian continental crust. This continental crust is extremely thinned to the southwest of this region, as shown in this Moho map. This area can be interpreted as oceanic in origin. In the depth range from 30 to 60 km, the S-velocity presents its lower values at the Carlsberg Ridge region, because it is the younger region of the study area. In the depth range from 60 to 105 km of depth, the S-velocity pattern is very similar to that shown for the previous depth range, except for the regions in which the asthenosphere is reached, for these regions appear a low S-velocity pattern. The lithosphere–asthenosphere boundary (LAB), or equivalently the lithosphere thickness, determined in the present study is also a new result, in which the lithosphere thickness for the Arabian Fan can be estimated in 60–70 km. The lower lithospheric thickness observed in the LAB map, for the Arabian Fan, shows that this region may be in the transition zone between continental and oceanic structure. Finally, a low-velocity zone (LVZ) has been determined, for the whole study area, located between the LAB and the boundary of the asthenosphere base (or equivalently the lithosphere–asthenosphere system thickness). The asthenosphere-base map calculated in the present study is also a new result.

Description: Metagabbros and gabbros in the Ablah-Shuwas belt (western Saudi Arabia) represent part of significant mafic magmatism in the Neoproterozoic Arabian Shield. The metagabbros are Cryogenian, occasionally stratified and bear calcic amphiboles (hornblende, magnesio-hornblende and actinolite) typical of calc-alkaline complexes. These amphiboles suggest low pressure (~1–3 kbar), high \(f_{{{\text{O}}_{2} }}\) and crystallization temperature up to 727 °C, whereas it is 247–275 °C in the case of retrograde chlorite. Rutile and titanite in metagabbros are Fe-rich and replace Mn-bearing ilmenite precursors at high \(f_{{{\text{O}}_{2} }}\) . On the other hand, younger gabbros are fresh, layered and comprised of olivine gabbro and olivine–hornblende gabbro with an uppermost layer of anorthositic gabbro. The fresh gabbros are biotite-bearing. They are characterized by secondary magnetite–orthopyroxene symplectitic intergrowth at the outer peripheries of olivine. The symplectite forms by deuteric alteration from residual pore fluids moving along olivine grain boundaries in the sub-solidus state. In fresh gabbros, ortho- and clinopyroxenes indicate crystallization at 1300–900 and 800–600 °C, respectively. Geochemically, the Cryogenian metagabbros (~850–780 Ma) are tholeiitic to calc-alkaline in composition and interpreted as arc-related. Younger, fresh gabbros are calc-alkaline and post-collisional (~620–590 Ma, i.e., Ediacaran), forming during the late stages of arc amalgamation in the southern Arabian Shield. The calc-alkaline metagabbros are related to a lithospheric mantle source previously modified by subduction. Younger, fresh gabbros were probably produced by partial melting of an enriched mantle source (e.g., garnet lherzolite).

Description: The Palaeoproterozoic (2.0–1.8 Ga) Svecokarelian orogen in central Sweden consists of a low-pressure, predominantly medium-grade metamorphic domain (central part of Bergslagen lithotectonic unit), enclosed to the north and south by low-pressure migmatite belts. Two periods of metamorphism (1.87–1.85 and 1.83–1.79 Ga) are known in the migmatite belts. In this study, new U–Th–Pb ion microprobe data on zircon and monazite from twelve samples of locally migmatized gneisses and felsic intrusive bodies determine both protolith and metamorphic ages in four sample areas north of Stockholm, inside or immediately adjacent to the medium-grade metamorphic domain. Two orthogneiss samples from the Rimbo area yield unusually old protolith ages of 1909 ± 4 and 1908 ± 4 Ma, while three orthogneisses from the Skutskär and Forsmark areas yield more typical protolith ages between 1901 ± 3 and 1888 ± 3 Ma. Migmatized paragneiss samples from this and two earlier studies contain a significant detrital component sourced from this 1.9 Ga magmatic suite. They are interpreted to be deposited contemporaneously with or shortly after this magmatism. Migmatization of the paragneiss at Rimbo was followed by intrusion of leucogranite at 1846 ± 3 Ma. Even in the other sample areas to the north (Hedesunda-Tierp, Skutskär and Forsmark), metamorphism including migmatization is constrained to the 1.87–1.85 Ga interval and penetrative ductile deformation is limited by earlier studies in the Forsmark area to 1.87–1.86 Ga. However, apart from a metamorphic monazite age of 1863 ± 1 Ma, precise ages were not possible to obtain due to the presence of only partially reset recrystallized domains in zircon, or highly discordant U-rich metamict and altered metamorphic rims. Migmatization was contemporaneous with magmatic activity at 1.87–1.84 Ga in the Bergslagen lithotectonic unit involving a mantle-derived component, and there is a spatial connection between migmatization and this magmatic phase in the Hedesunda-Tierp sample area. The close spatial and temporal interplay between ductile deformation, magmatism and migmatization, the P – T metamorphic conditions, and the continuation of similar magmatic activity around and after 1.8 Ga support solely accretionary rather than combined accretionary and collisional orogenic processes as an explanation for the metamorphism. The generally lower metamorphic grade and restricted influence of the younger metamorphic episode, at least at the ground surface level, distinguishes the central part of the Bergslagen lithotectonic unit from the migmatite belts further north and south.

Description: The Serbo-Macedonian Massif (SMM) represents a composite crystalline belt within the Eastern European Alpine orogen, outcropping from the Pannonian basin in the north to the Aegean Sea in the south. The central parts of this massif (south-eastern Serbia) consist of the medium- to high-grade Lower Complex and the low-grade Vlasina Unit. Outcrop- and micro-scale ductile structures in this area document three major stages of ductile deformation. The earliest stage D 1 is related to isoclinal folding, commonly preserved as up to decimetre-scale quartz–feldspar rootless fold hinges. D 2 is associated with general south-eastward tectonic transport and refolding of earlier structures into recumbent metre- to kilometre-scale tight to isoclinal folds. Stages D 1 and D 2 could not be temporally separated and probably took place in close sequence. The age of these two ductile deformation stages was constrained to the Variscan orogeny based on indirect geological evidence (i.e. ca. 408-ca. 328). During this period, the SMM was involved in a transpressional amalgamation of the western and eastern parts of the Galatian super-terrane and subsequent collision with Laurussia. Outcrop-scale evidence of the final stage D 3 is limited to spaced and crenulation cleavage, which are probably related to formation of large-scale open upright folds as reported previously. 40 Ar/ 39 Ar thermochronology was applied on hornblende, muscovite, and biotite samples in order to constrain the age of tectonothermal events and activity along major shear zones. These 40 Ar/ 39 Ar data reveal three major cooling episodes affecting the central SMM. Cooling below greenschist facies conditions in the western part of the Vlasina Unit took place in a post-orogenic setting (extensional or transtensional) in the early Permian (284 ± 1 Ma). The age of activity along the top-to-the-west shear zone formed within the orthogneiss in the Božica area of the Vlasina Unit was constrained to Middle Triassic (246 ± 1 Ma). This age coincides with widespread extension related to the opening of the Mesozoic Tethys. The greenschist facies retrogression in the Lower Complex probably occurred in the Early Jurassic (195 ± 1 Ma), and it was related to the thermal processes in the overriding plate above the subducting slab of the Mesozoic Tethys Ocean.

Description: What dynamic processes the South China-Indochina collision had gone through is still a pending problem. Our recent investigations identified a Late Triassic gabbroic intrusion in Mengdong village and several granitic plutons near Wana village, Yunnan province (SW China). Both have underwent strong metamorphism and been altered to amphibolite and granitic gneiss, respectively. We carried out SIMS and LA-ICPMS zircon U–Pb dating for the amphibolites and granitic gneisses, respectively. Dating results yield weighted mean 206 Pb/ 238 U ages of 221.5 ± 5.3 Ma for the amphibolites and 224.0 ± 1.8 and 235.4 ± 0.6 Ma for the granitic gneisses. The amphibolite samples have low Mg # (41.7–42.8), high TiO 2 (~3.7 wt%) and Na 2 O (Na 2 O/K 2 O = 1.89–2.68) contents and depleted Sr–Nd isotopic compositions [( 87 Sr/ 86 Sr) i  = 0.707647 and ε Nd ( t ) = +1.17]. They exhibit OIB-like REE patterns and spidergrams, with strongly enriched LREE contents, insignificant Eu anomalies (Eu* = 0.99–1.03) and moderate negative Sr anomalies (Sr* = 0.46–0.56). The protolith gabbro of the Mengdong amphibolites is derived from low-degree partial melting of a homogeneous OIB-type mantle source in the garnet stability field and experienced significant fractionation of olivine, clinopyroxene and plagioclase during magma evolution. The Wana samples are strongly peraluminous (A/CNK 〉 1.1) and K-enriched (K 2 O/Na 2 O = 2.93–3.63). They show enriched Sr–Nd isotopic compositions with ( 87 Sr/ 86 Sr) i  = 0.718589–0.719754 and ε Nd ( t ) = −11.34 to −10.92. The Wana plutons are typical S-type granite and product of the dehydration melting of meta-sedimentary rocks. We summarized Late Triassic age data in the literature along the South China-Indochina suture zone and recognized a significant Late Triassic magmatic flare-up. In combination with previous studies on the Late Triassic HP–UHP metamorphic rocks, we proposed that during the Late Triassic the South China-Indochina suture zone had transformed into post-collisional setting, and accompanied slab break-off triggered the OIB-type asthenospheric mantle upwelling and provided the heat source for the Late Triassic magmatic flare-up.

Description: A tectonothermal study of the northeastern sector of the Cantabrian zone (Ponga-Cuera and Picos de Europa units) using the conodont color alteration index (CAI) and Kübler index (KI) methods shows a variation from diagenetic to anchizonal conditions. The latter are illustrated in geological maps and cross sections. The greater part of the studied area has CAI values lower than 2, caused by two long periods of burial separated by a compressive interval (corresponding to the Variscan deformation), in which thrusts were the dominant structures. Tectonic superimposition was balanced by intense and fast erosion and had little effect on the CAI values. In contrast, a high thermal gradient was produced in the southern outcrops that led to recognize the transition between diagenetic and anchizonal conditions through CAI values near the basal thrust of the Picos de Europa unit. The diagenesis/anchizone boundary appears a little further south through the determination of the Kübler index in phyllosilicate minerals (KI = 0.42). CAI isograds cut the Variscan structures as a consequence of a thermal episode that occurred near the Carboniferous–Permian boundary at the beginning of an extensional regime. The thermal source was located further south, in the adjacent Pisuerga-Carrión unit. Alterations in the CAI values, as well as dolomitization and ore deposits, locally resulted from Permian–Mesozoic hydrothermal activity. Microtextural analysis of the conodonts allowed us to relate several types of apatite overgrowth to diagenetic conditions and recrystallization to anchizonal ones, whereas dissolution was common during hydrothermalism. Alpine deformation hardly produced any changes in the previous thermal pattern, but was responsible of the northwards tilting of the structure and CAI isograds.

Description: The magmatic evolution of the Variscan Albtal pluton, Schwarzwald, SW Germany, is explored using detailed textural observations and the chemical composition of plagioclase and biotite in both granite and its mafic magmatic enclaves (MMEs). MMEs probably formed in a two-step process. First, mafic magma intruded a granitic magma chamber and created a boundary layer, which received thermal and compositional input from the mafic magma. This is indicated by corroded “granitic” quartz crystals and by large “granitic” plagioclase xenocrysts, which contain zones of higher anorthite and partly crystallized from a melt of higher Sr content. Texturally, different plagioclase types (e.g. zoned and inclusion-rich types) correspond to different degrees of overprint most likely caused by a thermal and compositional gradient in the boundary layer. The intrusion of a second mafic magma batch into the boundary layer is recorded by a thin An 50 zone along plagioclase rims that crystallized from a melt enriched in Sr. Most probably, the second mafic intrusion caused disruption of the boundary layer, dispersal of the hybrid magma in the granite magma and formation of the enclaves. Rapid thermal quenching of the MMEs in the granite magma is manifested by An 30 overgrowths on large plagioclase grains that contain needle apatites. Our results demonstrate the importance of microtextural investigations for the reconstruction of possible mixing end members in the formation of granites.

Description: Indentation of rigid blocks into rheologically weak orogens is generally associated with spatiotemporally variable vertical and lateral block extrusion. The European Eastern and Southern Alps are a prime example of microplate indentation, where most of the deformation was accommodated north of the crustal indenter within the Tauern Window. However, outside of this window only the broad late-stage exhumation pattern of the indented units as well as of the indenter itself is known. In this study we refine the exhumational pattern with new (U–Th–Sm)/He and fission-track thermochronology data on apatite from the Karawanken Mountains adjacent to the eastern Periadriatic fault and from the central-eastern Southern Alps. Apatite (U–Th–Sm)/He ages from the Karawanken Mountains range between 12 and 5 Ma and indicate an episode of fault-related exhumation leading to the formation of a positive flower structure and an associated peripheral foreland basin. In the Southern Alps, apatite (U–Th–Sm)/He and fission-track data combined with previous data also indicate a pulse of mainly Late Miocene exhumation, which was maximized along thrust systems, with highly differential amounts of displacement along individual structures. Our data contribute to mounting evidence for widespread Late Miocene tectonic activity, which followed a phase of major exhumation during strain localization in the Tauern Window. We attribute this exhumational phase and more distributed deformation during Adriatic indentation to a major change in boundary conditions operating on the orogen, likely due to a shift from a decoupled to a coupled system, possibly enhanced by a shift in convergence direction.

Description: One of the striking features that characterise the late stages of the Variscan orogeny is the development of gneiss and migmatite domes, as well as extensional Late Carboniferous and Permian sedimentary basins. It remains a matter of debate whether the formation of domes was related to the well-documented late orogenic extension or to the contractional tectonics that preceded. Migmatization and magmatism are expected to predate extension if the domes are compression-related regional anticlines, but they must both precede and be contemporaneous with extension if they are extensional core complexes. In the Montagne Noire area (southern French Massif Central), where migmatization, magmatism and the deformation framework are well documented, the age of the extensional event was unequivocally constrained to 300–290 Ma. Therefore, dating migmatization in this area is a key point for discriminating between the two hypotheses and understanding the Late Palaeozoic evolution of this part of the Variscan belt. For this purpose, a migmatite and an associated anatectic granite from the Montagne Noire dome were dated by LA-ICP-MS (U–Th–Pb on zircon and monazite) and laser probe 40 Ar- 39 Ar (K–Ar on muscovite). Although zircon did not record any Variscan age unequivocally related to compression (380-330 Ma), two age groups were identified from the monazite crystals. A first event, at ca. 319 Ma (U–Th–Pb on monazite), is interpreted as a first stage of migmatization and as the emplacement age of the granite, respectively. A second event at ca. 298–295 Ma, recorded by monazite (U–Th–Pb) and by the muscovite 40 Ar- 39 Ar system in the migmatite and in the granite, could be interpreted as a fluid-induced event, probably related to a second melting event identified through the syn-extensional emplacement of the nearby Montalet leucogranite ca. 295 Ma ago. The ages of these two events post-date the Variscan compression and agree with an overall extensional context for the development of the Montagne Noire dome-shaped massif. Comparison of these results with published chemical (EPMA) dating of monazite from the same rocks demonstrates that the type of statistical treatment applied to EPMA data is crucial in order to resolve different monazite age populations.

Description: In the Iglesiente region, the Cabitza and Monte Argentu Formations are separated by an angular unconformity known as the Sardic unconformity. This is related to an early Ordovician mild compressional phase, known as the “Sardic phase”. The pelitic samples from the structurally lower Cabitza Formation consist of alternating reddish phyllosilicate-rich and whitish phyllosilicate-poor, sialic layers, whose S 0 bedding plane is parallel to a pre-Variscan S 1P schistosity overprinted by the Variscan S 1V schistosity. Pelitic samples from the Monte Argentu Formation are characterized by a Variscan S 1V axial plane schistosity. Samples from the two formations consist of quartz and phyllosilicates. The latter are potassic white mica, chlorite, paragonite, locally kaolinite, and pyrophyllite. The illite crystallinity values determined for the Cabitza samples are 0.25–0.31, with an average of 0.29; meanwhile, the Monte Argentu samples produce values of 0.33–0.38, with an average of 0.35. The chlorite crystallinity and b 0 of potassic white mica values show greater heterogeneity in the Cabitza than the Monte Argentu samples. The b 0 values and P–T pseudosections allow us to confirm that there is no significant difference in the P–T metamorphism conditions between the Cabitza and Monte Argentu samples. The Iglesiente region, which is considered to be the rift zone behind the Middle Ordovician Sarcidano–Barbagia volcanic arc, underwent the “Sardic phase”, giving rise to E–W folds. These were first overprinted by weak E–W, and then by stronger N–S-oriented Variscan deformation events.

Description: In this discussion, we evaluate the field, chemical, sedimentary, structural and metamorphic data related to the Kulidzhik area tectonic proposal.

Description: Symmetric structures in ductile shear zones range widely in shapes and geneses. Matrix rheology, its flow pattern, its competency contrast with the clast, degree of slip of the clast, shear intensity and its variation across shear zone and deformation temperature, and degree of confinement of clast in shear zones affects (independently) the degree of symmetry of objects. Kinematic vorticity number is one of the parameters that govern tail geometry across clasts. For example, symmetric and nearly straight tails develop if the clast–matrix system underwent dominantly a pure shear/compression. Prolonged deformation and concomitant recrystallization can significantly change the degree of symmetry of clasts. Angular relation between two shear zones or between a shear zone and anisotropy determines fundamentally the degree of symmetry of lozenges. Symmetry of boudinaged clasts too depends on competency contrast between the matrix and clast in some cases, and on the degrees of slip of inter-boudin surfaces and pure shear. Parasitic folds and post-tectonic veins are usually symmetric.

Description: The Mundwara alkaline plutonic complex (Rajasthan, north-western India) is considered a part of the Late Cretaceous–Palaeogene Deccan Traps flood basalt province, based on geochronological data (mainly 40 Ar/ 39 Ar, on whole rocks, biotite and hornblende). We have studied the petrology and mineral chemistry of some Mundwara mafic rocks containing mica and amphibole. Geothermobarometry indicates emplacement of the complex at middle to upper crustal levels. We have obtained new 40 Ar/ 39 Ar ages of 80–84 Ma on biotite separates from mafic rocks and 102–110 Ma on whole-rock nepheline syenites. There is no evidence for excess 40 Ar. The combined results show that some of the constituent intrusions of the Mundwara complex are of Deccan age, but others are older and unrelated to the Deccan Traps. The Mundwara alkaline complex is thus polychronous and similar to many alkaline complexes around the world that show recurrent magmatism, sometimes over hundreds of millions of years. The primary biotite and amphibole in Mundwara mafic rocks indicate hydrous parental magmas, derived from hydrated mantle peridotite at relatively low temperatures, thus ruling out a mantle plume. This hydration and metasomatism of the Rajasthan lithospheric mantle may have occurred during Jurassic subduction under Gondwanaland, or Precambrian subduction events. Low-degree decompression melting of this old, enriched lithospheric mantle, due to periodic diffuse lithospheric extension, gradually built the Mundwara complex from the Early Cretaceous to Palaeogene time.

Description: New in situ electron microprobe monazite and white mica 40 Ar/ 39 Ar step heating ages support the proposition that the Odenwald–Spessart basement, Mid-German Crystalline Zone, consists of at least two distinct crustal terranes that experienced different geological histories prior to their juxtaposition. The monazite ages constrain tectonothermal events at 430 ± 43 Ma, 349 ± 14 Ma, 331 ± 16 Ma and 317 ± 12 Ma/316 ± 4 Ma, and the 40 Ar/ 39 Ar analyses provide white mica ages of 322 ± 3 Ma and 324 ± 3 Ma. Granulite-facies metamorphism occurred in the western Odenwald at c. 430 and 349 Ma, and amphibolite-facies metamorphism affected the eastern Odenwald and the central Spessart basements between c. 324 and 316 Ma. We interpret these data to indicate that the Otzberg–Michelbach Fault Zone, which separates the eastern Odenwald–Spessart basement from the Western Odenwald basement, is part of the Rheic Suture, which marks the position of a major Variscan plate boundary separating Gondwana- and Avalonia-derived crustal terranes. The age of the Carboniferous granulite-facies event in the western Odenwald overlaps with the minimum age of eclogite-facies metamorphism in the adjacent eastern Odenwald. The granulite- and eclogite-facies rocks experienced contrasting pressure–temperature paths but occur in close spatial proximity, being separated by the Rheic Suture. As high-pressure and high-temperature metamorphisms are of similar age, we interpret the Odenwald–Spessart basement as a paired metamorphic belt and propose that the adjacent high-pressure and high-temperature rocks were metamorphosed in the same subduction zone system. Juxtaposition of these rocks occurred during the final stages of the Variscan orogeny along the Rheic Suture.

Description: Highly restitic rocks from the Antananarivo Block in northern Madagascar are investigated in this study in order to unravel processes of H 2 O-rich biotite formation in HT rocks. Polyphase metamorphism and melt migration occurred at 0.6 GPa and 850 °C. Biotite remains stable together with orthopyroxene and makes up to 45 vol% of the rock. In addition, three well-characterised and delimited microdomains having different textural, chemical and petrological characteristics are preserved. Thermodynamic models using the specific bulk compositions of the domains are in agreement with petrological observations. These rocks provide evidence that the lower crust may be strongly heterogeneous, locally associated to the formation of hydrous restites controlled by episodes of melt production and melt escape. This has significant consequences for understanding of the lower crust.

Description: The paleogeography and basin type of Upper Triassic flysch (Langjiexue Group) in the eastern Himalayan Orogen are disputed. In order to shed new light on the flysch’s origin, we applied different sedimentological methods. Assemblages of heavy minerals and clastic components of sandstones were utilized to determine the primary depositional composition. Heavy mineral indices, S/M ratios (thickness of sandstone + siltstone “S” versus slate/mudrock “M”), and paleocurrent data were combined to reveal the sediment dispersal pattern and the location of the source areas. In the analyzed sandstones, heavy minerals such as zircon, rutile, tourmaline, apatite, and anatase are most common, and zircon is predominant (most over 60 %). ZTR values range from 60 to 98 % and systematically increase southward. As a provenance-sensitive parameter, RuZi values vary in large magnitude and are significantly higher in both the east and west (〉20 %) than in the center. The majority of S/M ratios decrease from north to south, suggesting an overall decrease in grain size to the south. Paleocurrent directions vary between 120° and 270° (main vector 205°, and 185° after 20° counterclockwise correction), displaying a radial-curved pattern. Variable heavy mineral assemblages indicate different sources, and the sandstones fall in the “recycled” and “mixed-arc orogeny” fields of Dickinson triplots, together supporting the view of multiple sources. Results of the ZTR values, S/M ratios, and paleocurrent directions illustrate a dispersal pattern, corresponding to a submarine fan system. The provenance and submarine fan dispersal pattern along with the basin configuration (deep basin with oceanic affinities) suggest that the Langjiexue Group accumulated in a remnant basin between Lhasa, Greater India, and Australia, where the sediments dispersed into the basin toward the developing orogen/suture zone and not away from the orogen, challenging the provenance direction for the traditional remnant basin model.

Description: This study presents new whole-rock elemental and isotopic data for the basalts from the Zhaotong area, located in the intermediate zone of the ~260 Ma Emeishan large igneous province (ELIP). The Zhaotong basalts belong to high-Ti series with TiO 2 from 2.93 to 5.26 % and Ti/Y from 519 to 974. The parental magma was subjected to minor crustal contamination as indicated by slight Nb–Ta depletion (Nb/La: 0.72–1.10). Meanwhile, the relatively invariable Sr–Nd isotopes (ε Nd ( t ): −0.74 to +2.86, mostly +1.10 to +2.86; ( 87 Sr/ 86 Sr) i : 0.7050–0.7072) and the light rare earth elements (LREE) enrichment (La/Yb: 10.3–19.1) of the basalts prefer a mantle plume origin. A garnet-dominated peridotite mantle source was further suggested on the basis of the REE distribution patterns and high Sm/Yb and high La/Yb ratios. This study further confirms the geochemical zoning of the high-Ti basalts in the ELIP, which is in accordance with both the spatial distribution and the thickness of the basalts. The high-Ti basalts in the intermediate and outer zones of ELIP (e.g., Zhaotong and Guizhou) share similar Sr–Nd isotopic and elemental compositions, suggesting that they originated directly from the Emeishan mantle plume. By contrast, the high-Ti basalts in the inner zone (e.g., Longzhoushan and Binchuan) have variable compositions, indicating a rather heterogeneous mantle source possibly involved with subcontinental lithospheric mantle (SCLM) components.

Description: Massive, fine-grained metavolcanic rocks of the Çamlıca metamorphic unit exposed in the Biga Peninsula, northwestern Anatolia, have provided new Carboniferous ages and arc-related calc-alkaline petrogenesis constraints, suggesting that the Biga Peninsula was possibly involved in the Variscan orogeny. The metavolcanic rocks are mainly composed of metalava and metatuff and have the composition of andesite. Chondrite-normalized REE patterns from these rocks are fractionated (La N /Yb N  ~ 2.2 to 8.9). Europium anomalies are slightly variable (Eu/Eu* = 0.6 to 0.7) and generally negative (average Eu/Eu* = 0.68). The metavolcanic rocks have a distinct negative Nb anomaly and negative Sr, Hf, Ba, and Zr anomalies. These large negative anomalies indicate crustal involvement in their derivation. Tectonic discrimination diagrams show that all metavolcanic rocks formed within a volcanic arc setting. Zircon ages (LA-ICP-MS) of two samples yield 333.5 ± 2.7 and 334.0 ± 4.8 Ma. These ages are interpreted to be the time of protolith crystallization. This volcanic episode in the Biga Peninsula correlates with other Variscan age and style of magmatism and, by association with a collisional event leading to the amalgamation of tectonic units during the Variscan contractional orogenic event. Carboniferous calc-alkaline magmatism in the Sakarya Zone is ascribed to arc-magmatism as a result of northward subduction of Paleo-Tethys under the Laurasian margin. Geochemical and U–Pb zircon data indicate that the Sakarya Zone is strikingly similar to that of the Armorican terranes in central Europe. The Biga Peninsula shows a connection between the Sakarya Zone and the Armorican terranes.

Description: The petroleum system of the Upper Rhine Graben (URG) comprises multiple reservoir rocks and four major oil families, which are represented by four distinct source rock intervals. Based on geochemical analyses of new oil samples and as a review of chemical parameter of former oil fields, numerous new oil–source rock correlations were obtained. The asymmetric graben resulted in complex migration pathways with several mixed oils as well as migration from source rocks into significantly older stratigraphic units. Oldest oils originated from Liassic black shales with the Posidonia Shale as main source rock (oil family C). Bituminous shales of the Arietenkalk-Fm. (Lias α) show also significant source rock potential representing the second major source rock interval of the Liassic sequence. Within the Tertiary sequence several source rock intervals occur. Early Tertiary coaly shales generated high wax oils that accumulated in several Tertiary as well as Mesozoic reservoirs (oil family B). The Rupelian Fish Shale acted as important source rock, especially in the northern URG (oil family D). Furthermore, early mature oils from the evaporitic-salinar Corbicula- and Lower Hydrobienschichten occur especially in the area of the Heidelberg-Mannheim-Graben (oil family A). An overview on potential source rocks in the URG is presented including the first detailed geochemical source rock characterization of Middle Eocene sediments (equivalents to the Bouxwiller-Fm.). At the base of this formation a partly very prominent sapropelic coal layer or coaly shale occurs. TOC values of 20–32 % (cuttings) and Hydrogen Index (HI) values up to 640–760 mg HC/g TOC indicate an extraordinary high source rock potential, but a highly variable lateral distribution in terms of thickness and source rock facies is also supposed. First bulk kinetic data of the sapropelic Middle Eocene coal and a coaly layer of the ‘Lymnäenmergel’ are presented and indicate oil-prone organic matter characterized by low activation energies. These sediments are considered as most important source rocks of numerous high wax oils (oil family B) in addition to the coaly source rocks from the (Lower) Pechelbronn-Schichten (Late Eocene). Migration pathways are significantly influenced by the early graben evolution. A major erosion period occurred during the latest Cretaceous. The uplift center was located in the northern URG area, resulting in SSE dipping Mesozoic strata in the central URG. During Middle Eocene times a second uplift center in the Eifel area resulted in SW-NE-directed shore lines in the central URG and contemporaneous south-southeastern depocenters during marine transgression from the south. This structural setting resulted in a major NNW-NW-directed and topography-driven migration pattern for expelled Liassic oil in the fractured Mesozoic subcrop below sealing Dogger α clays and basal Tertiary marls.

Description: The NNE-trending Upper Rhine Graben (URG) of the European Cenozoic Rift System developed from c. 47 Ma onwards in response to changing lithospheric stresses in the northwestern foreland of the Alps. The composite graben structure consists of three segments, each c. 100 km long and 30–40 km wide, but flares to c. 60 km near its southern and to c. 80 km near its northern termination. Normal faulting induced a total extension of 5–8 km of the 1–2 km thick Mesozoic sedimentary Franconian platform and underlying Variscan basement rocks. However, distribution of an up to 3.5 km thick sedimentary graben fill and cumulative displacements near Eastern and Western Main Border fault systems suggest that subsidence of the graben floor and shoulder uplift created strong cross-sectional asymmetries. Cumulative W-down displacements 〉3 km along strongly segmented transfer faults in the east contrast with E-down displacements 〈3 km and major monoclinal “block fields” in the west. Both location and asymmetry of the URG appear to be related to lithospheric shear zones that originated within the central parts of the Variscan orogen between c. 330 and 315 Ma. Following pervasive deformation, HT/LP regional metamorphism and emplacement of granodioritic-granitic plutons a c. 50-km-thick orogenic crust were thinned to an about 30-km-thick two-layered crust above a reconsolidated and relatively planar crust-mantle boundary (Moho). In the URG area extensional thinning of the crust appears to have occurred mainly along a composite NNE-striking and mainly W-down “East Rhine Detachment”, which is partly exposed along the Wehratal, Omerskopf, Otzberg and other mylonitic-cataclastic shear zones in the basement of the eastern graben shoulder. These shear zones probably extend into lower crustal levels, where they are revealed as gently W-dipping seismic reflectors beneath and west of the URG. Major W-down displacements probably account for the mapped abundance of high-grade metamorphic basement rocks on the eastern graben shoulder in contrast to the predominantly low-grade metamorphic to unmetamorphosed sedimentary-volcanic rocks exposed on the western shoulder. Although between c. 310 and 270 Ma NE-trending Permocarboniferous volcanic-sedimentary basins of the URG area subsided along upper crustal faults that mimic the trend of Variscan faults, initial broad lithospheric cooling from c. 270–200 Ma led to subsidence of a distinctly NNE- to SSW-oriented embayment that was probably underlain by thinner Palaeozoic crust in the area of the NNE-trending East Rhine Detachment. After re-emergence of the platform above sea level in late Mesozoic times, the deep-reaching W-dipping “extensional defects” of the East Rhine Detachment exerted a primary lithospheric scale control on both location and cross-sectional asymmetry of the Cenozoic graben structure. NE- and NW-striking, strongly altered and more shallow rooted Permocarboniferous or Mesozoic faults exerted secondary upper crustal controls on transfer faults and the accommodation zones near the terminations and segment boundaries of the URG. Deep crustal to upper lithospheric asymmetries continue to influence the neotectonic setting of the URG, such as westward rising earthquake hypocentres. Seismic activity along the URG appears to be part of a 〉600 km long zone that delimits the trailing edge of a SW-moving lithospheric block. In the URG area, NE–SW-oriented seismic anisotropy at sublithospheric depths of c. 60–80 km suggest active mantle flow in this direction as a possible driving force for the reactivation of pre-graben lithospheric shear zones.

Description: New Ar–Ar muscovite and Rb–Sr biotite age data in combination with structural analyses from the Apuseni Mountains provide new constraints on the timing and kinematics of deformation during the Cretaceous. Time–temperature paths from the structurally highest basement nappe of the Apuseni Mountains in combination with sedimentary data indicate exhumation and a position close to the surface after the Late Jurassic emplacement of the South Apuseni Ophiolites. Early Cretaceous Ar–Ar muscovite ages from structurally lower parts in the Biharia Nappe System (Dacia Mega-Unit) show cooling from medium-grade conditions. NE–SW-trending stretching lineation and associated kinematic indicators of this deformation phase (D1) are overprinted by top-NW-directed thrusting during D2. An Albian to Turonian age (110–90 Ma) is proposed for the main deformation (D2) that formed the present-day geometry of the nappe stack and led to a pervasive retrograde greenschist-facies overprint. Thermochronological and structural data from the Bihor Unit (Tisza Mega-Unit) allowed to establish E-directed differential exhumation during Early–Late Cretaceous times (D3.1). Brittle detachment faulting (D3.2) and the deposition of syn-extensional sediments indicate general uplift and partial surface exposure during the Late Cretaceous. Brittle conditions persist during the latest Cretaceous compressional overprint (D4).

Description: The basal and intermediate decollements play an important role in structural style of fold-and-thrust belts. The decollement units, or different mechanical stratigraphy within the rock units, are not uniform throughout the ZFTB and show a strong spatial variation. The Lurestan region with varied thickness of the intermediate decollement in its northern and southern parts is one of the most important parts of the Zagros fold-and-thrust belt, regarding its hydrocarbon exploration–extraction projects. Thickness variation of the intermediate decollement in different parts of the Lurestan region allows us to address its role on folding style. Based on scaled analogue modeling, this study outlines the impact of thickness and facies variation of sedimentary rocks in the northern and southern parts of this region on folding style. Two models simulated the mechanical stratigraphy and its consequent different folding styles of the northern and southern parts of the region. In the models, only thickness of the intermediate decollement (thick and thin) for the northern and southern parts of the Lurestan region was varied. Detached minor folds above the intermediate decollement were created in response to the presence of the thicker intermediate decollement, northern part of the study area, which consequently deformed complexly and disharmonically folded, in contrast to polyharmonic folding style in the section, compared to polyharmonic folding style in the southern part, where thin intermediate decollement exists. The model results documented that thickness variation of intermediate decollement levels could explain complex and different folding styles in natural examples which must be taken into account for hydrocarbon exploration throughout these areas.

Description: The structure of a ~250-m-long asymmetrical pull-apart basin developed in carbonate rocks at the Galilee heights, Israel, is herein analyzed. The reconstruction of the basin geometry is based on detailed mapping and LiDAR measurements of fault scarps. The architecture of faults is then used as a boundary condition for calculating the stress pattern in the vicinity of the basin, using a dislocation model. The basin is found to be an asymmetrical V-shaped structure bordered by two longitudinal oblique right-lateral strike–slip faults. The strike of one of the faults is bent at the eastern edge of the basin, generating a transverse boundary fault which joins the second boundary fault orthogonally. The overall lateral displacement is smaller than the basin length, and no transverse or diagonal fault is observed in the western end of the basin. The deformation around the basin is mostly displayed by fractures. Yet, folds and fault branches are observed near the tips of the boundary faults and near kink points of fault segments. Stress analysis obtained by the three-dimensional model is in general agreement with the orientation of fractures and location of high deformation regions in and around the basin. Based on our observations, we present a conceptual model which demonstrates the development of asymmetric basins in releasing bends and sheds light on the structures of similar large pull-apart basins.

Description: The Huangshan orogenic-type gold deposit in Zhejiang of SE China occurred in quartz–pyrite veins. It is hosted by phyllonite that underwent greenschist-facies metamorphism along a large Jiangshan–Shaoxing tectonic belt with a NE–SW direction. Trace elemental characteristics, ore-forming process and invisible gold on different forms of pyrite and quartz are studied. The Au associated pyrite can be classified into two categories; recrystallized pyrite and euhedral pyrite. The precipitation of invisible Au on pyrite is mainly derived by Co and Ni with AuHS 2 − complex in the mineralizing fluids in different events. The XPS results revealed that valence states of Au 3+ replaced 2Fe 2+ in the pyrite and Au 0 replaced Si 4+ in the quartz structure. The electron paramagnetic resonance and trace elemental results suggested that the element pairs of Ge–Li–Al in quartz and Mn–Co–Ni in pyrite have distinct impurities as identified. A fluid inclusion study showed that the auriferous quartz is characterized by low-saline and CO 2 -rich fluids. Coexistence of the type I–type III inclusions and same range of homogenization temperature with different mode are evidences of immiscible fluid process. The temperature–pressure values of ca. 250 °C/1250 bar and ca. 220 °C/780 bar for gold precipitation have been calculated by intersection of coexisting fluids during the entrapment. The Huangshan orogenic-type gold deposit may be associated with the Wuyi–Yunkai orogeny during the early Paleozoic, including an upper–mid greenschist-facies metamorphism (450–420 Ma). All the features suggest that the Huangshan gold deposit is probably a product linking with the early Paleozoic orogeny in South China.

Description: The Cuonadong dome exposes in east-southern margin of the North Himalayan gneiss domes (NHGD), which is reported first time in this study. The Cuonadong dome is located at the southern part of the Zhaxikang ore concentration area, which is divided into three tectono-lithostratigraphic units by two curved faults around the dome geometry from upper to lower (or from outer to inner): the upper unit, middle unit and lower unit, and the outer fault is Nading fault, while the inner fault is Jisong fault. The Cuonadong dome is a magmatic orthogneiss and leucogranite mantled by orthogneiss and metasedimentary rocks, which in turn are overlain by Jurassic metasedimentary and sedimentary rocks. The grades of metamorphism and structural deformation increase towards the core, which is correspondence with the Ridang Formation low-metamorphic schist, tourmaline granitic–biotite gneiss, garnet–mica gneiss and mylonitic quartz–mica gneiss. The Cuonadong dome preserves evidences for four major deformational events: firstly top-to-S thrust (D 1 ), early approximately N–S extensional deformation (D 2 ), main approximately E–W extensional deformation (D 3 ), and late collapse structural deformation (D 4 ) around the core of the Cuonadong dome, which are consistent to three groups lineation: approximately N–S-trending lineation including L 1 and L 2 , E–W trending L 3 , and L 4 with plunging towards outside of the dome, respectively. The formation of the Cuonadong dome was probably resulted from the main E–W extensional deformation which is a result of eastward flow of middle or lower crust from beneath Tibet accommodated by northward oblique underthrusting of Indian crust beneath Tibet. The establishment of the Cuonadong dome enhanced the E–W extension of the NHGD, which is further divided into two structural dome zones according to the different extensional directions: approximately N–S extensional North Himalayan gneiss domes (NS-NHGD) and E–W extensional North Himalayan gneiss domes (EW-NHGD). The NS-NHGD developed by a dominantly N–S contraction and locally extensional regime and keep a close relationship to the South Tibetan Detachment System, whereas the EW-NHGD formed by an E–W extensional deformation along the north–south-trending rifts.

Description: Meso- to Neoproterozoic magmatic events are widespread in the Yangtze Block. The geochronology and tectonic significance of the Shennongjia Group in the Yangtze Block are still highly controversial. An integrated geochronology and geochemistry approach provides new insights into the geochronological framework, tectonic setting, magmatic events, and basin evolution of the northern Yangtze Block. Our new precise sensitive high-resolution ion microprobe U–Pb data indicate a deposition age of 1180 ± 15 Ma for the Shicaohe Formation subalkaline basaltic tuff that is geochemically similar to modern intracontinental rift volcanic rocks. The integration of available geochemical data together with our new U–Pb ages indicates the Shicaohe Formation subalkaline basaltic tuff formed ca. 1180 in a continental rift-related setting on a passive continental margin. The Shennongjia Group is topped by the Zhengjiaya Formation volcanic sequence, indicating arc-related igneous events at 1103 Ma. The transition of the late Mesoproterozoic tectonic regime from intracontinental extension to convergence occurred between ca. 1180 and 1103 Ma in the northern Yangtze Block. Tectonic evolution in the Neoproterozoic led to accretion along the northern margin of the Yangtze Block. These results provide geochronological evidence, which is of utmost importance for reconfiguration of the chronostratigraphic framework and for promoting research on Mesoproterozoic strata in China, thereby increasing understanding of magmatic events and basin evolutionary history in the northern Yangtze Block.

Description: The Kashmir Basin Fault is located in the Jammu and Kashmir region of Kashmir Basin in NW Himalaya, India. It is a classic example of an out-of-sequence thrust faulting and is tectonically active as observed from multiple geological evidences. Its geomorphology, structure and lateral extent indicate significant accommodation of stress since long, which is further supported by the absence of a large earthquake in this region. It seems this fault is actively accommodating some portion of the total India–Eurasia convergence, apart from two well-recognised active structures the Medlicott–Wadia Thrust and the Main Frontal Thrust, which are referred in Vassallo et al. (Earth Planet Sci Lett 411:241–252, 2015 ). This requires its quantification and inclusion into slip distribution scheme of NW Himalaya. Therefore, it should be explored extensively because this internal out-of-sequence thrust could serve major seismic hazard in KB, repeating a situation similar to Muzaffarabad earthquake of Northern Pakistan in 2005.

Description: The Chohar Gonbad-Gugher-Baft ophiolite mélange, located along the major Baft and Shahr-e-Babak fault zones, southeast Iran, represents remnants of Neo-Tethyan oceanic lithosphere. This mélange contains blocks of harzburgite, dunite, lherzolite, basalt, and other ophiolite-related lithologies tectonically mixed with and embedded in a serpentinite matrix. Field, petrographic, and geochemical data show that peridotites in this mélange belong to the upper mantle. They seem to have undergone up to ~20 % partial melting in a supra-subduction zone setting, based on their spinel Cr# values (0.21–0.53). Chemical compositions and textures in the serpentinites indicate that they were partially hydrated during emplacement and further mobilized diapirically to the surface. The different deformation stages occurred in an accretionary wedge environment. Petrographic evidence shows that the first serpentinization event produced mesh-textured serpentinites formed under static conditions in an ocean floor environment (Nain-Baft ocean crust), where the initial lizardite, bastite, and chrysotile veins formed. Plastic deformation occurred due to the subduction of Nain-Baft oceanic lithospheric beneath the central Iranian microcontinent, with antigorite-bearing flare-textured serpentinites produced. During progressive exhumation of the Nain-Baft ophiolite mélange, the serpentinites were affected by ductile, ductile–brittle, and brittle deformation, respectively. Accretion and resultant diapirism are the most important processes in the emplacement of serpentinite, which is a consequence of hydration of the ocean crust. In this example, late-stage emplacement via thrusting occurred along the northern extent of the southern Sanandaj–Sirjan zone (S–SZ).

Description: In the northern Variscan French Massif Central, the Sioule metamorphic series exposes from top to bottom the tectonic superposition of the Upper Gneiss Unit (UGU), Lower Gneiss Unit (LGU), and Para-autochthonous Unit (PAU). The nappe stacking developed throughout two prograde syn-metamorphic events: D 1 is a top-to-the-SW shearing coeval with a probable Devonian migmatization and D 2 is a top-to-the-NW shearing event. Both events were completed before the unconformable deposition of the undeformed and unmetamorphosed “Tufs anthracifères” formation, dated at ca 330 Ma (Late Visean). Furthermore, the UGU experienced a high-pressure metamorphism ascribed to a D 0 event during which eclogite or granulite crystallized in several parts of the UGU. Monazite U–Th–Pb and zircon U–Pb SIMS datings were carried out in order to constrain the ages of these D 0 , D 1 , and D 2 tectono-metamorphic events. These new geochronological results are placed in a P–T-t diagram constructed for the UGU, LGU, and PAU. Monazite sampled in UGU, LGU, and PAU rocks yields similar 365–350 Ma ages consistent with the D 2 event dated in other places of the French Massif Central. A zoned monazite grain from a granulitic paragneiss yields 416 ± 15 and 362 ± 14 Ma ages interpreted as those of the D 0 and D 2 events, respectively. Zircon from the same granulitic paragneiss yields SIMS ages at 343 ± 2 and 328 ± 2 Ma that are interpreted as recrystallization processes associated with post-thickening thermal events, possibly recording the onset of orogenic collapse of the Northern Massif Central. It is worth to note that neither monazite nor zircon recorded the D 1 event.

Description: Jifeng ophiolitic mélange (ultramafic rocks, meta-basalts and gabbros) crops out in the northern segment of the Great Xing’an Range, the eastern segment of the Central Asian Orogenic Belt, which marks the closure of the Xinlin–Xiguitu Ocean associated with the collision between the Erguna block and Xing’an block. In order to investigate the formation age and magma source of the Jifeng ophiolitic mélange, the gabbros from newly discovered the Jifeng ophiolitic mélange are studied with zircon U–Pb ages, whole-rock geochemistry and zircon Hf isotopes. Zircon U–Pb dating from the ophiolitic gabbros yields U–Pb age of 647 ± 5.3 Ma, which may represent the formation age of the ophiolitic mélange. The gabbros display low SiO 2 , TiO 2 , K 2 O contents, high Na 2 O, LREE contents and indistinctive REE fractionation [(La/Yb) N  = 1.97–2.98]. It shows an E-MORB-like affinity, while the element concentrations of the Jifeng samples are lower than that of E-MORB. More importantly, Nb displays negative anomaly in comparison with Th, which shows a transitional SSZ-type ophiolite signature. Moreover, the ε Hf ( t ) values of ~647 Ma zircons in the gabbros range from +8.4 to +13.4, and the corresponding Hf single-stage ages ( T DM1 ) are between 687 and 902 Ma, which is obviously older than the crystallization age of 647 Ma. These geochemical features can be explained as melts from the partial melting of a depleted mantle source meta-somatized by fluids derived from a subducted slab. Accordingly, we conclude that the Jifeng ophiolitic mélange is probably related to transitional SSZ-type ophiolite and developed in an intra-oceanic subduction, which indicates that an ocean (the Xinlin–Xiguitu Ocean) existed between the Erguna block and Xing’an block. The Ocean’s formation might be no later than the Neoproterozoic (647 Ma), and it was closed in the Late Cambrian because of the collision between the Erguna block and Xing’an block.

Description: In the course of studying the gold-bearing heavy mineral spectrum of sediments from the upper Rhine River, a distinct suite of detrital grains comprising platinum-group minerals (PGM), cassiterite, columbite-group minerals and uraninite was identified and investigated using conventional and modern analytical methods. This study aimed to characterize the selected mineral groups mineralogically and geochemically in order to identify possible source areas and to reconstruct different aspects of the complex sedimentary history of the Rhine River sediments. The PGM assemblage is dominated by grains of Ru–Os–Ir alloys (~70 %), followed by Pt–Fe alloys, sperrylite and rare other PGM. Accordingly, this PGM assemblage represents highly mature, physically and chemically extremely resistant compounds which may have experienced and survived repeated reworking during their sedimentary history. Pt–Fe alloys and sperrylite may originate from various sources; however, the predominant Ru–Os–Ir alloy grains point to an origin from ophiolite sequences of unknown age (but likely pre-Alpine; Variscan or older). The exact locations of the primary sources and the complex, prolonged sedimentary history of the detrital PGM with possibly multiple intermittent storages remain unknown. Detrital cassiterite grains were dated by the U–Pb method using LA-ICP-MS. The age dates of cassiterite largely overlap with zircon age distributions by peaking distinctly at ca. 325 Ma (majority of ages), thereby implying a predominantly Variscan age of the cassiterite grains and possible derivation from mineralization in the Black Forest area. Columbite-group minerals are dominantly tapiolite originating from pegmatites. Rare uraninite grains attest that this mineral experienced rapid erosion, transport and deposition in a reducing environment.

Description: The analysis of 2D seismic and well data provides new insights into the late Eocene to earliest Oligocene dynamics along the southern border of the North Sea area, Belgium. From the start of the Priabonian onwards, the northwestern part of the Campine Basin and the London–Brabant Massif to its west experienced subsidence and developed into a shallow trough. Simultaneously, several other southern North Sea basins, including the central and eastern part of the Campine Basin and the Roer Valley Graben, were inverted by what is generally referred to as the Pyrenean inversion phase. Inversion caused broad flexural uplift and minor reverse fault movements. The characteristics of inversions in the southern North Sea basins are very similar to each other and to those described for a phase of intraplate stress relaxation. The results of this study therefore suggest that the Pyrenean inversion phase was triggered by a regional stress relaxation that started around the Bartonian/Priabonian boundary and ended before the onset of the Oligocene.

Description: The 2008 M w 7.9 Wenchuan earthquake formed two coseismic surface rupture zones with the trend of N35°E, known as the Beichuan–Yingxiu rupture and the Pengguan rupture. The Beichuan–Yingxiu rupture is the principle one with abundant fault gouge development along its length. In the exploratory trench at the Saba village along the Beichuan–Yingxiu rupture, the new fault gouge zone is only ~3 mm wide, which suggests that fault slip was constrained in a very narrow zone. In this study, we thus carried out detailed microstructural and mineral component analysis on the oriented fault gouge samples from the Saba exploratory trench to understand their features and geological implication. The results show that different microstructures of localized brittle deformation can be observed in the fault gouges, including Y-shear, R1-shear, R2-shear, P-shear as well as tension fracture, bookshelf glided structure and so on. These microstructures are commonly recognized as the product of seismic fault slipping. Furthermore, within the area between two parallel Y-shears of the fault gouge, a few of microstructures of distributed ductile deformations were developed, such as P-foliation, elongation and asymmetrical trailing structure of detrital particles. The microstructure features of fault gouges implicate the thrust movement of the fault during the Wenchuan earthquake. In addition, the fault gouge has less quartz and feldspar and more clay than the surrounding rocks, which indicates that some quartz and feldspar in the surrounding rocks were transformed into clay, whereas the fault gouge has more illite and less illite/montmorillonite mixed layers than the surrounding rocks, which shows that the illite/montmorillonite mixed layer was partly converted into illite due to temperature increasing induced by coseismic fault slipping friction (also being affected partly by the chemical action of solutions). Such microstructures features and mineral component changes recorded the information of fault slip and provide criterions for discussing the genesis of fault gouge and recognition of the direction of fault movement.

Description: The Băiţa metallogenic district in the Bihor Mountains is a historically important mining area in Romania. Uranium mining took place between 1952 and 1998 from various deposits, but very little is known about the geology and mineralogy of these deposits. In this paper, we describe geology and mineralogy of uranium mineralization of the Avram Iancu uranium mine from waste dump samples collected before complete remediation of the site. Texturally and mineralogically complex assemblages of nickeline, cobaltite–gersdorffite solid solution, native Bi, Bi-sulfosalts, molybdenite, and pyrite–chalcopyrite–sphalerite occur with uraninite, “pitchblende,” and brannerite in most of the ore samples. The association of nickel, cobalt, and arsenic with uranium is reminiscent of five-element association of vein type U–Ni–Co–Bi–As deposits; however, the Avram Iancu ores appear to be more replacement-type stratiform/stratabound. Avram Iancu ore samples contain multistage complex, skarn, uranium sulfide, arsenide assemblages that can be interpreted to have been formed in the retrograde cooling stages of the skarn hydrothermal system. This mineralizing system may have built-up along Upper Cretaceous–Paleogene “Banatite” intrusions of diorite-to-granite composition. The intrusions crosscut the underlying uraniferous Permian formations in the stacked NW-verging Biharia Nappe System. The mineralization forms stacked, multilayer replacement horizons, along carbonate-rich lithologies within the metavolcanic (tuffaceous) Muncel Series. Mineral paragenesis and some mineral chemistry suggest moderate-to-high 〈450, i.e., 350–310 °C, formation temperatures for the uranium sulfide stage along stratigraphically controlled replacement zones and minor veins. Uranium minerals formed abundantly in this early stage and include botryoidal, sooty and euhedral uraninite, brannerite, and coffinite. Later and/or lower-temperature mineral assemblages include heterogeneous, complexly zoned arsenide–sulfarsenide solid solutions associated with minute but abundant uranium minerals. Within the later arsenide–sulfarsenide mineral assemblage, there is great variation in Ni, Co, and S content with generally increasing arsenic content. Uranium minerals in this late-stage assemblage include very fine euhedral uraninite and brannerite inclusions in arsenide–sulfarsenide minerals. Native bismuth and Bi-sulfosalt krupkaite are observed in this As–S-rich assemblage strongly associated with cobaltite.

Description: Balkassar is an important hydrocarbon producing area of the Potwar Plateau, Pakistan. Two-dimensional seismic reflection data of the area revealed tectonically controlled, distinct episodes of (1) normal faulting in the basement followed by (2) reverse faulting in the cover sequence. Himalayan orogeny and associated diapirism of the Precambrian Salt Range Formation have produced many salt-cored anticlines in the Potwar Plateau, and one such salt-cored anticline is present in the Balkassar. This anticline has NE–SW-oriented axis, and both the SE and NW limbs are bounded by reverse faults. The basement normal faults indicate Jurassic rifting and splitting of Pangaea. We interpret reverse faults with dip angles of about 60°–75° in the cover sequence, having both hinterland and foreland vergence. Both NW- and SE-dipping faults are present in contrast to the only southward-directed thrusts of previous models. Duplexes and triangle zones, which are common in the northern part of the Potwar Plateau, are not developed in the Balkassar area due to comparatively less crustal shortening in the area. The present interpretation can help in understanding the complex structures in other parts of the Potwar Plateau for hydrocarbons exploration and also in deformed foreland basins worldwide that display similar characteristics but are considered to be dominated by low-angle thrust tectonics.

Description: The Mirandola anticline represents a buried fault-propagation fold which has been growing during Quaternary due to the seismogenic activity of a blind segment belonging to the broader Ferrara Arc. The last reactivation occurred during the May 2012 Emilia sequence. In correspondence with this structure, the thickness of the marine and continental deposits of the Po Plain foredeep is particularly reduced. In order to better define the shallow geometry of this tectonic structure, and hence its recent activity, we investigated in a depth range which is intermediate between the surficial morphological observations and seismic profiles information. In particular, we carried out numerous passive seismic measurements (single-station microtremor) for obtaining the horizontal-to-vertical spectral ratio. The results of a combined analysis of the peak frequency and its amplitude nicely fit the available geological information, suggesting that this low-cost geophysical technique could be successfully applied in other sectors of wide morphologically flat alluvial plains to investigate blind and completely buried potential seismogenic structures.

Description: The Misajé granitic pluton, emplaced between 569 and 560 Ma in an amphibolitic and gneissic host rock, comprises four petrographic units namely biotite-hornblende granite (BHG), granodiorite (Gd), biotite granite (BG), and leucocratic granite (LG). Four major tectonic events have been described in the studied area: a D 1 -early tectonic event, responsible of the E–W flat foliation which has been progressively transposed by a D 2 tectonic event. A D 2 event has developed heterogeneous simple shear in a dextral transpressive context with moderate to strong dipping NE–SW striking foliation; a D 3 tectonic event has lead to a sinistral N–S ductile shear characterized by N- to ENE-striking foliation and E–W strike-slip shear corridors and a D 4 tectonic event that developed N–S dextral ductile strike-slip deformation. The magnetic study of the pluton, based on the AMS parameters, reveals the coexistence of both paramagnetic (dominated by iron-bearing silicates; 54 % of sites) and ferromagnetic (due to the occurrence of PSD and MD grains of magnetite or other ferromagnetic minerals; 46 % of sites) behaviors. Magnetic foliation shows best poles at 55/82 for the whole pluton, 95/32 in BHG, and 273/83 in BG, and the magnetic lineation trends are mostly NNE–SSW with best lines at 210/8, 198/19, and 36/3, respectively. The trend of the magnetic lineation in BG indicates an S-shape trajectory, suggesting a sinistral sense of shear motion along discrete E–W corridors situated at the northern and southern ends. Kinematic indicators in BG point to a sinistral sense of shear, suggesting its emplacement during the D 3 event. The close relationship between K 1 and K 3 points to a syn-kinematic emplacement and crystallization of the Misajé granitic pluton during the Pan-African event, and the tectonic evolution of the study area is considered to be coeval with the tectonic evolution of the trans-Saharan Pan-African belt of eastern Nigeria.

Description: A 1445-km 2 high-resolution 3D seismic reflection dataset is used to analyze the Permian large igneous province in the subsurface of the Tazhong area in the central Tarim Basin in northwestern China. Constrained by the synthetic seismograms of four wells, the top and base of the igneous rocks were identified in the seismic data. Seven large volcanic craters, each 〉10 km 2 in area, have been discovered via the application of coherency and amplitude attributes. The thickness and volume of the igneous rocks were obtained by time–depth transformation. In the study area, all of the igneous rocks, with thicknesses from 120 to 1133 m, were formed by eruptions in the Early Permian. These events produced huge erupted volumes (178 km 3 ) and multiple closely spaced volcanic edifices (〈13 km). These features suggest that the study area may be the part of the eruptive center of the Permian igneous rocks in the Tarim Basin.

Description: The Villarroya Basin in Northern Spain contains one of the classic Villafranchian localities of Europe and allows about 100 m of sediments to be explored by magnetostratigraphic techniques. Besides, the occurrence of some other macro- and micro-mammifera fossils becomes Villarroya in one of the most important Villafranchian localities of Southern Europe. Therefore, we have sampled two sections (one contains the classic locality) to shed some light on its chronostratigraphy. Detailed stepwise demagnetization has revealed primary and reliable directions (carried by magnetite and hematite) in more than 250 samples and allows us building a robust local polarity scale. The correlation with the geologic time scale locates the local sequence along the Gauss and Matuyama chrons. A Réunion chron (C2r.1n) equivalent age (2.128–2.148 Ma) is here proposed for the Villarroya fossil locality since it is clearly located above the Gauss/Matuyama boundary (very well defined in the magnetostratigraphic section) and displays normal polarity. This correlation implies a new age assignment for the classic paleontological fossil locality of Villarroya and a Last Appearance Datum of Hipparion sensu lato in Western Europe significantly younger than previously established. Taking into account this new dating, the Hipparion and Equus horses could have coexisted in Europe up to the complete extinction of Hipparion in early Matuyama times.

Description: The Río Guanajibo fold-and-thrust belt (RGFT), composed of Cretaceous serpentinite and volcano-sedimentary rocks, represents the deformation front of a contractional event in SW Puerto Rico during the Paleogene. Previous studies inferred structural and stratigraphic relationships from poorly exposed outcrops. New road cuts exposed the Yauco (YF) and El Rayo Formations (ERF) providing insights on the deformation of the hanging wall and footwall. We described the nature and orientation of faults and folds and analyzed the kinematic indicators to characterize the deformation. The YF occurs in the hanging wall and shows a sequence of folded, medium-bedded mudstone and thinly bedded shale and sandstone. Major folds strike NW–SE and are gentle with steeply inclined axial planes and sub-horizontal fold axes. Minor folds are open with moderately inclined axial planes and gently to moderately inclined SE-plunging fold axes. NW–SE striking reverse and thrust faults cut layers and show movement to the SW. Steep left-lateral faults strike NW–SE and NE–SW, and smaller right-lateral strike-slip faults strike NNE–SSW. At the footwall, the ERF consists of bioclastic limestone and polymictic orthoconglomerates and paraconglomerates. Reverse and strike-slip faults cut along lithological contacts. Results suggest that the hanging wall and footwall accommodated strain along preexisting weaknesses, which are dependent on lithology and sedimentary structures. The kinematic analysis suggests that shortening in the NE–SW direction was partitioned between folding and interlayer shortening, accommodated by flexural slip, and reverse and left-lateral faults that resulted from contraction. The RGFT represents the Paleogene back arc deformation of a bivergent thrust system.

Description: Anatolia’s high-pressure metamorphic belts are characterized in part by a Neotethyan stratigraphic succession that includes a mid-Cretaceous hemi-pelagic marble sequence. This unit contains, towards its stratigraphic top, dm-to-m-long radiating calcitic rods forming rosette-like textures. Here, we refer to these features as “Rosetta Marble”. The remarkable textural similarity of non-metamorphic selenite crystals and radiating calcite rods in the Rosetta Marble strongly suggests that these textures represent pseudomorphs after selenites. Metamorphosed hemi-pelagic limestones, dominated by Rosetta selenite pseudomorphs, are alternating with siliceous meta-sediments containing relictic radiolaria tests. This stratigraphic pattern is indicative of transient phases characterized by evaporites precipitated from basinal brines alternating with non-evaporative hemi-pelagic deposition from normal-marine seawater. The regional distribution of Rosetta Marble exposures over 600 km is indicative of basin-scale evaporitic intervals. High-pressure, low-temperature metamorphism of these rocks is witnessed by Sr-rich (up to 3500 ppm), fibrous calcite pseudomorphs after aragonite and isolated aragonite inclusions in quartz. Peak metamorphic conditions of 1.2 GPa and 300–350 °C are attested by high-Si white mica thermobarometry. The Rosetta Marble case example examines the potential to unravel the complete history from deposition to diagenesis and metamorphism of meta-sedimentary rocks.

Description: Geophysical data allowed the construction of a ~250-km-long lithospheric-scale balanced cross section of the southern Black Sea margin (Espurt et al. in Lithosphere 6:26–34, 2014 ). In this paper, we combine structural field data, stratigraphic data, and fault kinematics analyses with the 70-km-long onshore part of the section to reconstruct the geodynamic evolution of the Central Pontide orogen. These data reveal new aspects of the structural evolution of the Pontides since the Early Cretaceous. The Central Pontides is a doubly vergent orogenic wedge that results from the inversion of normal faults. Extensional subsidence occurred with an ENE-trend from Aptian to Paleocene. We infer that the Black Sea back-arc basin also opened during this period, which was also the period of subduction of the Tethys Ocean below the Pontides. As in the Western Pontides, the Cretaceous–Paleocene subsidence was interrupted from Latest Albian to Coniacian time by uplift and erosion that was probably related to a block collision and accretion in the subduction zone. The restoration of the section to its pre-shortening state (Paleocene) shows that fault-related subsidence locally reached 3600 m within the forearc basin. Structural inversion occurred from Early Eocene to Mid-Miocene as a result of collision and indentation of the Pontides by the Kırşehir continental block to the south, with 27.5 km (~28 %) shortening along the section studied. The inversion was characterized by NNE-trending shortening that predated the Late Neogene dextral escape of Anatolia along the North Anatolian Fault and the modern stress field characterized by NW-trending compression within the Eocene Boyabat basin.

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Franconian Basin in NE Bavaria is a region of gravity low between the Bohemian Massif in the east and the Kraichgau Terrane in the west. Borehole measurements have identified the northern part of the Franconian Basin as a regional geothermal anomaly and new heat flow calculations give values of  〉 100 mW/m〈sup〉2〈/sup〉. Distinct negative Bouguer anomalies observed in this basin are modeled as granitic intrusions in the Saxothuringian basement that underlies the Permo-Mesozoic units. The interpretation of gravity gradients, in combination with the filtering of gravity data, gives the possible depth constraints of the intrusive bodies. The resulting depths were cross-checked using microstructural studies of quartz veins in the basement rocks (at 〉 1341 m depth). The quartz shows structures typical for low-temperature plasticity and we infer a deformation temperature of ca. 300 °C. This indicates a considerable pre-Permian uplift of at least 7 km for parts of the Saxothuringian basement and supports depth estimates from gravity data. The heat supply of granitic intrusions by radiogenic decay is modeled considering several scenarios for the geological conditions recovered by the Obernsees borehole (model for conductive heat transfer). The 1390 m-deep drillhole is in a marginal position to the most-pronounced negative Bouguer anomaly. It could be shown that the Saxothuringian basement, including heat-producing granites (heat production rates: 4–6 μW/m〈sup〉3〈/sup〉), covered by the insulating sedimentary rocks (1.35 km of Permian to Lower Jurassic units), can account for the enhanced geothermal gradient (38 °C/km) that were measured in the borehole.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The timing and mechanisms of collapse of the middle and western segments of the Lhasa–Qiangtang orogenic belt in central Tibet are poorly constrained. Here, we report whole-rock geochemical, and zircon U–Pb age and Hf-isotopic data for the Asa-intrusive rocks located at the southern edge of the northern Lhasa subterrane. The Asa-intrusive rocks include the Namujeler granite porphyry (NGP), the Gernicamdro granodiorite porphyry (GGDP), and the Neeze granodiorite porphyry (NGDP). The NGP and GGDP have adakitic geochemical characteristics, such as high Sr (317–511 ppm), Sr/Y (57.8–96.8), and (La/Yb)〈sub〉N〈/sub〉 (13.1–16.0), and low Y (4.68–5.49 ppm) and heavy rare-earth element contents (e.g., 0.44 ≤ Yb ≤ 0.57 ppm). In situ zircon U–Pb dating of three samples yielded Late Cretaceous ages (NGP = 88.7 Ma; GGDP = 89.7 Ma; NGDP = 90.1 Ma). Zircon εHf(〈em〉t〈/em〉) values vary over a wide range (NGP = − 11.5 to + 9.3; GGDP = + 4.6 to + 7.6; NGDP = − 21.2 to + 7.6). Our results suggest that the Asa adakitic rocks (NGP and GGDP) are most likely generated by partial melting of thickened mafic lower crust under a garnet-bearing amphibolite facies. The presence of the Asa adakitic rocks indicates that the crust beneath the Lhasa–Qiangtang collision zone had experienced thickening and the crustal thickness remains quite large (〉 40 km) at ca.90 Ma. On the basis of evidence from the Asa-intrusive suite and coeval igneous rocks, along with some stratigraphic and tectonic constraints, we proposed that the middle and western segments of the Lhasa–Qiangtang orogenic belt was collapsed by lithospheric delamination during the early Late Cretaceous (ca. 94–82 Ma), and the thickened lithospheric keel did not delaminate as a wholly, it delaminated piece by piece. From east to west, the time of the lithospheric delamination is getting younger.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Variscan Rand Granite as defined in this paper is a deformed I-type biotite granite that intruded along the southern-to-southeastern margin of the Central Schwarzwald Gneiss Complex. Former K-feldspar megacrysts (now porphyroclasts) of this K–Mg-rich alkali-calcic granite frequently show zonal crystallographic arrangement of mineral inclusions and are enclosed in a matrix of plagioclase, K-feldspar, quartz, biotite, apatite, zircon, and magnetite. Minor sphene and allanite are mostly altered. K-feldspar is orthoclase with perthitic exsolutions. Myrmekite is common and typically replaces marginal K-feldspar. Both feldspars show cataclastic and incipient ductile deformation that took place within the stability field of biotite (≥ 400 °C) as proven by grey varieties of Rand Granite with stable biotite. At most places, however, the Rand Granite shows a reddish colour, caused by late-stage chloritization of biotite and formation of hematite within K-feldspar. Furthermore, plagioclase became partially altered to sericite. This hydrothermal alteration took place at temperatures below the stability of biotite (〈 400 °C). In situ ion probe U–Pb dating on zircon gave a concordant age of 330.9 ± 4.8 Ma (2〈em〉σ〈/em〉), interpreted as the intrusion age of the Rand Granite. A large number of younger concordant to slightly discordant zircon ages between 309 and 90 Ma are interpreted to be due to episodic Pb loss during hydrothermal alteration. The Rand Granite apparently does not contain zircon domains older than the intrusion age and, furthermore, shows relatively high Zr contents (247–358 µg/g). These characteristics suggest high magma temperatures of at least 850–900 °C. The granitic magma most probably resulted from remelting of K-rich mafic to intermediate rocks in the middle crust at H〈sub〉2〈/sub〉O-undersaturated conditions. Low Sr/Y ratios suggest a garnet-free residuum, which is only possible at pressures below ~ 0.9 GPa.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This research presents an integrated study of 2D seismic reflections and calibrated well data to outline the structural development of the Gorgan Plain on the border of the South Caspian hydrocarbon basin, in the Alborz and Kopeh-dagh ranges of northeast Iran. Eight seismic horizons, including two unconformities, have been identified, ranging in age from Early Jurassic to Quaternary. Analysis and interpretation of geophysical data provide an understanding of the structural geology of the Gorgan Plain, crucial for investigation of structural traps. Seismic interpretation indicates structural features such as deep reverse listric faults (inverted normal faults) for older formations; strike-slip and normal faults in younger sequences; dome and basin interference patterns of folding for all the top formations. Well data demonstrate the occurrence of a disconformity at the base of Upper Cretaceous beds and an angular unconformity at the base of Paleogene. Evidence identified in well and seismic-reflection data proves a complex pattern of tectonic phases since the Early Jurassic. It seems reasonable to suppose that these structural patterns are related to a change in direction of tectonic compression, which in turn has produced structural hydrocarbon traps in crests of domes in the Gorgan area.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Helanshan Tectonic Belt and its environs within the northwestern Ordos Terrane, western North China Craton, have been envisaged as aulacogen or plate boundary separating the Alxa Massif from the Ordos Block during Cambrian. However, it conflicts with geological and geophysical facts. This study presents integrated stratigraphic, sedimentary and geochronological data from the Cambrian strata in the northwestern Ordos Terrane to constrain the Cambrian tectonic evolutionary process of the western North China Craton. The Cambrian successions comprise, in ascending order, evaporite platform facies, restricted-open platform facies and evaporite platform facies, featuring a vertical transgression–regression sequence. An eastward-shoaling paleogeography was documented, evidenced by shallow-water dolomite layers enriched in the east and the detritus derived from northeast. Ages of detrital zircons span from 2566 to 1649 Ma with predominant two peaks around 2500 and 1850 Ma, suggesting these Cambrian detritus were sourced from the Archean–Paleoproterozoic rocks in the Yimeng highland. Comparable fossil associations and unified paleogeography system supported that there was no Cambrian plate boundary in the northwestern Ordos Terrane, implying the Alxa Massif was part of the North China Craton during the Cambrian. The westward-deepening facies differentiation with low-angle topography contradicts with the tectonic model of “Helan aulacogen”. In combination with the relatively low subsidence rate and rare magmatic–metamorphic activities, we argue that the Cambrian shallow marine system in the western North China Craton was the continent-ward extension of passive continental margin basin system related to the spreading of the Paleo-Asian Ocean.〈/p〉

Description: 〈p〉In the online published article, Figs. 4 and 12 were published incorrectly. The correct figures are given below.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The nature of the warm climates of the Cretaceous has been enigmatic since the first numerical climate models were run in the late 1970s. Quantitative simulations of the paleoclimate have consistently failed to agree with information from plant and animal fossils and climate sensitive sediments. The ‘cold continental interior paradox’ (first described by DeConto et al. in Barrera E, Johnson C (eds) Evolution of the Cretaceous Ocean/climate system, vol 332. Geological Society of America Special Paper, Boulder, pp 391–406, 1999), has been an enigma, with extensive continental interiors, especially in northeast Asia, modeled as below freezing in spite of plant and other evidence to the contrary. We reconsider the paleoelevations of specific areas, particularly along the northeastern Siberian continental margin, where paleofloras indeed indicate higher temperatures than suggested by current climate models. Evidence for significant masses of ice on land during even the otherwise warmest times of the Cretaceous is solved by reinterpretation of the δ〈sup〉18〈/sup〉O record of fossil plankton. The signal interpreted as an increase in ice volume on land is the same as the signal for an increase in the volume of groundwater reservoirs on land. The problem of a warm Arctic, where fossil floras indicate that they never experienced freezing conditions in winter, could not be solved by numerical simulations using higher CO〈sub〉2〈/sub〉 equivalent greenhouse gas concentrations. We propose a solution by assuming that paleoelevations were less than today and that there were much more extensive wetlands (lakes, meandering rivers, swamps, bogs) on the continents than previously assumed. Using ~ 8 × CO〈sub〉2〈/sub〉 equivalent greenhouse gas concentrations and assuming 50–75% water surfaces providing water vapor as a supplementary greenhouse gas on the continents reduces the meridional temperature gradients. Under these conditions the equatorial to polar region temperature gradients produce conditions compatible with fossil and sedimentological evidence.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉High-resolution 3D seismic P-wave velocity model of Poland (Grad et al., Tectonophysics 666:188–210, 2016) and corrected for paleoclimate heat flow map (Majorowicz and Wybraniec, Int J Earth Sci 100(4):881–887, 2011) gridded to a common mesh are used together with four independent thermal models of the crust and upper mantle to calculate heat flow variation with depth and geotherms. Heat flow at Moho depth are calculated and mapped and both confirm large variability with an elevated mantle heat flow (circa 30–40 mW/m〈sup〉2〈/sup〉) in the Paleozoic Platform which is some 10–20 mW/m〈sup〉2〈/sup〉 higher than Moho heat flow in the north-eastern and south-eastern Poland which belong to a variety of tectonic terranes (the oldest Precambrian Craton, younger Cadomian, Trans-European Suture Zone, Carpathians). Temperatures calculated for the crust show consistent pattern: higher temperatures beneath the Paleozoic Platform and lower temperatures beneath the Precambrian and Cadomian units. At 10 km depth this difference is about 150 °C, about 300 °C at 20 km depth, and about 400 °C at 50–60 km. Assuming the calculated isotherm 580 °C as Curie temperature the magnetic crust thickness was determined as 5–10 km only beneath the Polish Basin, circa 20 km in Carpathians, circa 30 km in Sudetes, and 35–40 km beneath the Precambrian and Cadomian units. Such a thick magnetic crust results from a great depth of Curie temperature, thick crystalline crust, and thin sediments. Mantle heat flow variability is mainly correlating with measured surface heat flow and influences geotherms. Calculated thermal LAB depth follows patterns of heat flow and Moho heat flow variability through Poland with thinnest lithosphere in the high surface heat flow and high mantle heat flow areas. Comparison of this thermal LAB depth estimates with seismic data based LAB depth shows general coincidences when Precambrian Craton vs Paleozoic Platform are considered along the P4 seismic experiment data model (circa 190 km depth vs some 90 km depth, respectively). However, significant differences exist in many areas and especially for the SE Poland when compared with map for the whole of Poland compiled from other seismic reported data.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Koltonik et al. (Int J Earth Sci 107:2645–2669, 2018) evidence that the Late Devonian siliciclastic rocks from the Rheno-Hercynian Zone, in Germany, derived from Baltica and Scandinavian Caledonides. This finding together with what is known about the provenance of the Pulo do Lobo and South Portuguese zones, in Portugal and Spain, reinforces the probability that Late Devonian basins may have been sourced from distinct terranes placed along the Variscan suture. Our comment intends to underline changes in the provenance of the Late Devonian basins along the active margin of Laurussia, and also, to improve the correlation model for the Variscan tectonic units from SW Iberia and Germany.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉U–Pb ages of zircons recovered from Pliocene pyroclastic deposits in northern part of the Cenozoic intra-Carpathian back-arc basin (Pannonian Basin) span the interval from Pliocene (2.2 Ma) to Paleoproterozoic (Orosirian–Rhyacian, 1850–2115 Ma). The scattered U–Pb ages reflect eruption ages of the host basaltic volcanic centres, two episodes of post-Eocene magmatic crustal growth, and the possible tectonic affiliation, provenance and age of the subjacent basement or the sedimentary basin detritus sampled by the basaltic magma. The youngest zircons define the maximum ages of phreatomagmatic eruptions during the Late Miocene–Pliocene extension. These zircons are distinguished from older zircons by Zr/Hf (40–90) and Th/U ratios (0.5–4.5) as well as super-chondritic 〈em〉ε〈/em〉Hf(〈em〉t〈/em〉) values ranging from + 7 to + 14, indicating mantle-derived parental magmas. The locally increased Th/U ratios (up to 8) accompanied by Zr/Hf 〉 60 are diagnostic of evolved phonolite parental melt. Hence, the youngest zircons can be interpreted as antecrysts, originating from evolved melts cogenetic with the host alkali basalts. In contrast, older zircons represent xenocrysts scavenged by the uprising basalt from surrounding rocks. Subordinate Eocene–Early Oligocene (29–38 Ma) sub-group of zircon xenocrysts is coincidental with the magmatism and volcanism along the Periadriatic lineament and the middle-Hungarian zone. The Early Miocene (18 Ma) cluster is coeval with the deposition of the Bükk Mountains felsic ignimbrite correlated with the onset of the back-arc extension that triggered Miocene sedimentation within the Pannonian Basin. The Eocene–Early Oligocene zircons have been likely scavenged from pyroclastic and ash-fall deposits of the Palaeogene retroarc basin subjacent to the Miocene basin infilling. Sub-chondritic 〈em〉ε〈/em〉Hf(〈em〉t〈/em〉) values between − 2.5 and − 8 in the Eocene–Early Miocene zircons attest their crystallization from subduction-related felsic-to-intermediate melts containing large amounts of recycled crustal material. Palaeozoic–Proterozoic zircons create a heterogeneous population with variable trace element abundances and 〈em〉ε〈/em〉Hf(〈em〉t〈/em〉) values. The determined age clusters are reminiscent of some basement units cropping out recently in Central Western Carpathians. Zircon Hf isotope data indicate recycling of up to 3.4 Ga old mafic crust and also the presence of 2 Ga old juvenile mafic crust. These units had either underlain the northern part of the Pannonian Basin during Pliocene or had been exposed during the deposition of Miocene clastic sediments. The absence of Mesoproterozoic, Grenvillian zircons (0.9–1.8 Ga) in the pre-Cenozoic population of zircon xenocrysts is provisionally interpreted as indicating the evolution of the zircon source area within the west-African Craton.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The present work is aimed at reviewing the state of the art of the studies centered on the pre-collisional and collisional, Variscan evolution of the eastern Southern Alps. The main focus is on the Carnic Alps, a geologically spectacular and extremely complex area, which has been a major subject of study for structural geologists, stratigraphers, and paleontologists for more than a century. After decades of field studies aimed at unveiling the birth and evolution of this belt, the tectonic and geodynamic interpretations proposed for almost a century by two different groups of authors remain substantially different. German-speaking authors, over the decades, have consistently proposed a scenario marked by a mature, Devonian passive margin, which later on evolved into an active Mississippian continental margin; the following collisional phase resulted in an accretionary wedge that, in its evolution, might be compared to those generated by Variscan events outside the Alpine domain. On the contrary, Italian authors have mainly put forward a pre-collisional setting dominated by wrench-fault tectonics, followed by the formation of a large, collisional thrust-and-fold belt, arc-shaped in plan view. We illustrate the results accomplished so far and discuss the interpretations formulated by the two different research schools; our review provides a chance to compare the different interpretations and, at the same time, prompts the need for new and targeted data collection in the area.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Three cliff-forming outcrops of the Dhruma Formation representing the carbonate platform in the Hafirat Nisha district west of Riyadh, Saudi Arabia, were investigated to identify and understand the microfacies variability in a carbonate ramp setting. An integrated approach including detailed field investigations, petrographic, biofacies, and micropaleontological analyses was used to construct a model of the depositional environments of the investigated outcrop sections. The depositional model indicates that the identified lithofacies were predominantly deposited in outer ramp, middle ramp, inner ramp, and lagoonal settings. The presence of the benthic foraminifera 〈em〉Redmondoides lugeoni〈/em〉 and 〈em〉Nautiloculina oolithica〈/em〉 and the trace fossil 〈em〉Thalassinoides〈/em〉 indicates deposition in shallow-water environments and the prevalence of warm climatic conditions during the Middle Jurassic. The occurrences of calcareous and agglutinated benthic foraminiferal species 〈em〉Pseudomarssonella maxima〈/em〉, 〈em〉Siphovalvulina variabilis〈/em〉, 〈em〉Timidonella sarda〈/em〉, 〈em〉N. oolithica〈/em〉, 〈em〉R. lugeoni〈/em〉, 〈em〉Praekurnubia crusei〈/em〉, 〈em〉Paleopfenderina salernitana〈/em〉, 〈em〉Haurania deserta〈/em〉, 〈em〉Siphovalvulina〈/em〉 spp., 〈em〉Lenticulina〈/em〉 sp., 〈em〉Textulariopsis〈/em〉 sp., and 〈em〉Amijella amiji〈/em〉 imply that our studied sections are situated within the Dm-2 to Dm-5 biozones (Bajocian to early Bathonian). This is also supported by the calcareous nannofossil assemblages that show a Bajocian to early Bathonian age. The depositional sequences indicate a shift in the depositional environment from low-energy lagoonal with intermittent shoal complexes in the D2 and D3 Units to predominantly shoal complex and open-marine settings in the D4 Unit, suggesting a seaward shift towards the top of the D4 Unit. The interpreted depositional settings are similar to those previously documented in the subsurface equivalent, Faridah reservoir. This indicates that the investigated D2〈strong〉–〈/strong〉D4 Units outcrops are excellent analogues of the subsurface reservoir.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Intra-Sudetic Basin, a ~ 12 km deep Variscan intramontane basin, has the best preserved post-orogenic sedimentary record available at the NE margin of the Bohemian Massif. Apatite fission track (AFT) analyses have been performed on 16 sedimentary and volcanic samples of Carboniferous to Cretaceous age from the Intra-Sudetic Basin to improve understanding of the post-Variscan thermal evolution. AFT central ages range from 50.1 ± 8.8 to 89.1 ± 7.1 Ma (Early Eocene to Coniacian), with 13 of them being Late Cretaceous. The mean track length values range from 12.5 ± 0.4 to 13.8 ± 0.5 (except for one sample 14.4 ± 0.2) µm. This relatively short mean track length together with the unimodal track length distributions and rather low standard deviation (0.8 to 1.7 µm) in most samples indicate a long stay in the partial annealing zone during slow cooling. However, in the northern part of the Intra-Sudetic Basin, samples show a wider track length distribution (standard deviation of 1.8 to 2.1 µm) that could indicate a more complex thermal evolution possibly related to Mesozoic reheating. Vitrinite reflectance data combined with thermal models based on the AFT results indicate that the Carboniferous strata reached maximum palaeotemperatures in the latest Carboniferous to Early Permian time, corresponding to a major coalification event. The second phase of temperature rise occurred due to Late Mesozoic sedimentary burial, but it had no influence on maturation of the Carboniferous organic matter. Final cooling phase in the Late Cretaceous–Paleogene was related to tectonic inversion of the Intra-Sudetic Basin, which occurred after deposition of a significant thickness of Cenomanian–Turonian sediments. Thermal modelling demonstrates that ~ 4 km thick cover of Upper Cretaceous sediments is required to obtain a good match between our AFT data and modelled time–temperature paths. This outcome supports a significant amount of Late Cretaceous–Paleogene inversion within the Variscan belt of Central Europe.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study presents extensive new field, petrographic, and whole-rock major and trace element and Sm–Nd and Pb isotope data for the Neoarchean megacrystic anorthosite-bearing Bird River Sill, spatially associated Neoarchean supracrustal rocks of the Bird River greenstone belt, and the Mesoarchean Maskwa Lake TTG Batholith I, Manitoba, Canada. Field observations indicate that the 2743 Ma Bird River Sill was emplaced into the Northern Lamprey Falls Formation in an oceanic setting and subsequently intruded by the ca. 2725 Ma Maskwa Lake Batholith II. The Northern Lamprey Falls Formation is in fault contact with the overlying Peterson Creek Formation, which in turn is unconformably overlain by the Bird River Formation. The peridotites of the Bird River Sill were subjected to intense alteration and ductile shearing, resulting in the redistribution of many major and trace elements and resetting of their Sm–Nd and U–Th–Pb isotopic systems. The gabbro, leucogabbro, and anorthosite units of the sill largely retain their primary igneous textures and minerals, REE and HFSE compositions, and Sm–Nd and Pb isotope signatures. These geochemical and petrographic data indicate that these units of the Bird River Sill crystallised from a hydrous, Ca- and Al-rich tholeiitic magma that fractionated from a hydrous primitive arc tholeiitic parental magma. The major and trace element geochemistry and initial 〈em〉ε〈/em〉〈sub〉Nd〈/sub〉 values of the Bird River Sill (+ 0.53 to + 4.72) and the Northern Lamprey Falls Formation (+ 1.40 to + 2.66) of the Bird River greenstone belt crystallised from parental magma batches that were derived by partial melting of variably-depleted mantle sources. High-magnesian andesites from the Bird River Formation formed by partial melting of subducting oceanic crust and/or slab sediments and subsequent interaction with sub-arc mantle peridotite, whereas the Peterson Creek Formation dacites and Maskwa Lake TTG Batholith I tonalites formed by partial melting of juvenile lower arc crust. The major and trace element geochemistry of the Bird River Sill and greenstone belt and the Maskwa Lake TTG Batholith I, and geological relationships and lithological associations point to a transition from continental arc to continental back-arc magmatism along the southern active margin of the North Caribou terrane at ca. 2743 Ma, resulting in the formation of the Maskwa Lake microcontinent that occurred prior to subsequent continental arc magmatism along the southern margin of this microcontinent. Combined field observations and geochemical data indicate that the Bird River Sill and Bird River greenstone belt are a dismembered Archean subduction-related ophiolite that marks a suture zone between the Winnipeg River subprovince and the Maskwa Lake microcontinent.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The sedimentary instability dynamics occurring over time throughout the isolated Galicia Bank (Atlantic Ocean, NW Iberian Peninsula) have been studied using a sedimentological and geotechnical approach featuring a quantitative assessment of slope stability under different scenarios, including earthquake activity. The erosion of the scarps in the Galicia Bank includes the continuous development of small instabilities evacuated along gullies and channels or deposited on slopes. These deposits may be subsequently mobilized, evolving into new sedimentary gravity flows (e.g., turbidity flow). The studied sediments consist mostly of poorly to very poorly sorted sands and silts transported by turbidity currents and occasionally by debris flow processes. The sediments in the study area identified as normally consolidated and located on gently sloping areas (gradients less than 5°) may become unstable if low-magnitude seismic events occur (PGA 〈 0.12). Even under static conditions, they could become unstable if they are located on slopes of 〉 10° without any trigger other than oversteepening. In contrast, overconsolidated sediments may remain stable under static conditions and may become unstable on slope gradients 〉 10° when earthquakes occur with the maximum peak ground acceleration (PGA = 0.34). The sedimentological and geotechnical models presented herein are complementary approaches that can be utilized to understand the long-term sedimentary instability dynamics observed within the study area. Such results are critical for better understanding sedimentary models of the dismantling processes of deep seamounts located far away from continental sedimentary inputs.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper discusses the facies sequence character for sandstone rocks of the subsurface upper Middle Devonian and Upper Devonian Ravendale Interval in the Bancannia Trough, western Darling Basin. The integration of multiple correlation techniques (recognition of changes in core and cutting facies, electrofacies and lithostratigraphic-facies associations) has helped define an internal stratigraphic correlation framework for the Ravendale Interval. This provides a powerful tool for understanding the distribution of the lithostratigraphic architectural controls on reservoir potential. This study has re-evaluated the stratigraphic boundaries of the Ravendale Interval (bottom and top) using marked changes in gamma-ray and sonic log characteristics, and depth estimates of the boundaries were derived from the wireline log data in the Bancannia South-1, Bancannia North-1 and Jupiter-1 wells. The internal stratigraphy of the Ravendale Interval consists of 20 facies and 19 subfacies that define 4 facies associations (FA). These facies associations are characterised as facies association-A (FAA), a braided channel-fill system; facies association-B (FAB), a meandering channel-fill system; facies association-C (FAC), a multistory fluvial channel-fill complex system, and facies association-D (FAD), a meandering channel delta system. The Ravendale Interval has been subdivided into five wireline log lithostratigraphic units (RI1, RI2, RI3, RI4 and RI5, in ascending order) in the three available wells. Use of the suggested wireline log lithostratigraphic unit correlations versus facies association of the Ravendale Interval has the potential to refine existing stratigraphic sequence schemes and, given the higher resolution and more detailed correlation, may significantly improve subsurface sedimentological framework relationships in lithostratigraphic unit reconstructions. Wireline log correlations indicate that potentially productive sand-rich units of the major Ravendale Interval in the Bancannia Trough can be correlated over large distances, suggesting significant continuity into lightly drilled and undrilled areas, and aid in the prediction of potential hydrocarbon-bearing reservoirs within the Darling Basin region.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉U–Pb dating, Hf-isotope, and trace-element studies on two detrital zircon samples from sandstone interlayers in the Upper Jurassic conglomerates of the Southern coast of the Mountainous Crimea provide new information on the primary crystalline complexes from which those conglomerates were sourced. The U–Pb age spectra of studied zircons suggest that they were most likely sourced from the (meta)sedimentary complexes of the Eastern and Western Pontides blocks and the Dobrogea platform. In particular, a close similarity of the Precambrian age spectra with the detrital zircons from Late Neoproterozoic–Late Paleozoic (meta)sedimentary complexes of the Dobrogea block provides strong supporting evidence for the affinity between the Pre-Mesozoic basement of the Crimea and the Dobrogea platform. The zircons in the first sample were recycled through Dobrogea sedimentary complexes and originated from terranes with Amazonia affinities, while zircons in the second sample were recycled through the Taurides and originated from terranes related to northeastern Africa and Arabia. The strong similarity of the Precambrian parts of the age spectra of the Dobrogea complexes and the sample K15-007 suggests a resemblance of the Crimea’s Pre-Mesozoic foundation and the Dobrogea platform. Initial analytical data are provided in Electronic Supplementary Materials A (ESM A). Descriptions of measurement parameters, methodologies, and constants used to process primary analytical data and some processing results are reported in ESM B (Figs. B1–B8). Schemes of locations within Balkans–Anatolia–Black Sea–Caucasus region the crystalline complexes with Jurassic, Triassic, Permian–Carboniferous, as well as Late Neoproterozoic–Cambrian and Ordovician–Devonian ages are in ESM C (Figs. C1, C3–C5).〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Understanding the exhumation of middle to lower crustal rocks is of utmost importance to unravel intracrustal mass transfer processes during orogenic build-up. The Figueira de Castelo Rodrigo–Lumbrales Anatectic Complex (FCR–LAC) is located within the autochthonous terrane of the Variscan Central Iberian Zone and is an example of the association between S-type granites and migmatites. The anatectic complex contacts to the north and south with low-grade metamorphic units through the Huebra and Juzbado–Penalva do Castelo shear zones, respectively. Integration of new U–Pb zircon and apatite age data allowed us to obtain Variscan crystallization ages, inherited zircon ages and unprecedented cooling rates for different facies of the FCR–LAC granites. The zircon crystallization ages mostly cluster around 313–317 Ma for the syn-tectonic granites, whereas the dated late-tectonic granite provided an age of 300 Ma. The cooling rates range from 13 to 35 °C Ma〈sup〉−1〈/sup〉, which implies fast exhumation (0.3–0.84 mm a〈sup〉−1〈/sup〉) and shallow emplacement (ca. 8 km deep), compatible with exhumation facilitated by large crustal-scale shear zones. Inherited zircon in the granites reveals melting of Cadomian metasediments (650–550 Ma), Upper Cambrian–Lower Ordovician (495–470 Ma) metaigneous rocks (Ollo de Sapo formation) and of minor older components, suggesting protolith affinity with the Northern Domain of the Central Iberian Zone.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The mid-Langhian (“Badenian”) flooding fully reconnected the semi-isolated Central Paratethys realm with the Mediterranean and, thereby, drastically changed the middle Miocene paleogeography of Central Europe. Due to the scattered stratigraphic record and scarcity of independent age constraints in some areas, the precise age and underlying mechanism are still debated. We present integrated chronostratigraphic data from five sections in the eastern part of the system to reconstruct the flooding event distal from the strait to the Mediterranean. By applying modern Mediterranean biochronology (planktonic foraminifera and calcareous nannofossils), supplemented by an 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar age on a tuff, we demonstrate that the widespread open marine settings in the NW Transylvanian Basin were definitely installed after 14.9 Ma (MMi4d biozone), and in most areas before 14.4 Ma. In the marginal study area in the SE Carpathian Foredeep, fully marine conditions likely set in slightly later (14.6–14.4 Ma). There, short-lived marine incursions into the brackish environment occurred since the latest Burdigalian (“pre-flooding phase”). The new ages overlap with the flooding in the majority of the Central Paratethys (~ 14.9–14.4 Ma), and with marine overflow into the Black Sea (14.85 Ma). We suggest that the transgression was driven by subsidence of the Pannonian Basin, by creating accommodation space and diminishing barriers between sub-basins, but was likely enhanced by a global sea-level rise. Finally, we speculate that the scarcity of all calcareous material in the SE Carpathian Foredeep before the mid-Langhian flooding might be related to pulses of nutrient-rich brackish and low pH water from the neighboring Black Sea Basin.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Late Quaternary paleoclimate records from arid regions help us understand the response of ecological systems to natural climate change to place recent changes in a longer-term perspective. In this research, a biogeochemical analysis of a sediment core from Lake Ebinur, Xinjiang, allowed us to infer the climate and environmental changes in the late Quaternary in arid northwestern China. The combined lipid biomarkers and bulk biogeochemical properties (TOC, 〈em〉δ〈/em〉〈sup〉13〈/sup〉C〈sub〉org〈/sub〉) revealed moderately wet conditions from 34 to 28 ka, favoring the growth of terrestrial vegetation. The subsequent period from 28 to 13 ka was dominated by aquatic plants, algae and microbes, indicating cold and dry conditions. Ameliorated regional moisture conditions were deduced from the higher carbon preference index (CPI) and from 〈em〉δ〈/em〉〈sup〉13〈/sup〉C〈sub〉org〈/sub〉 values from 13 to 3.6 ka. The optimum climate conditions occurred from 9 to 5 ka. Several climatic events also exist in the Lake Ebinur records with a wide distribution into other regions. Our biogeochemical-based paleoclimate and paleoenvironmental reconstruction is generally synchronous with sedimentary records from mid-latitude Eurasia and the NGRIP ice core record, which probably has a certain linkage with the 45°N summer insolation. We propose that summer insolation conditions in the northern hemisphere might have an impact on the climate and environmental changes in arid northwestern China in the late Quaternary.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The increased aridification of Central Asia during the Miocene coincides in time with lake formations and the evolution of playa environments in the region. However, Miocene continental climate dynamics and the forcing of aridification are still not well constrained. Neogene lacustrine mudflat deposits in the Ili Basin in southeast Kazakhstan provide a well-exposed paleoclimate archive. Here, we present a detailed rock magnetic study of a middle Miocene playa cycle deposited in a closed basin. We use high-resolution rock magnetic parameters, lithological studies and geochemistry to reconstruct the playa environment and the depositional conditions. The rock magnetic mineralogy of the playa cycle is controlled by hematite and two fine-grained magnetite phases. Increased magnetic concentrations occur during dry mudflat conditions, with a lower groundwater table and increased aridity. The underlying processes controlling the observed variation in magnetic concentrations are a complex interplay of diagenetic processes during and after deposition. The data support an authigenic origin of both magnetite phases, one formed before and the other after sediment consolidation. Early diagenetic formation of fine-grained magnetite by microbial activity is followed by post-depositional formation of a secondary fine-grained magnetite phase. The rock magnetic results such as magnetic concentration-dependent parameters, ARM/SIRM and s-ratio indicate a sensitive record of (ground) water availability and aridity changes in the Ili Basin. We suggest that they can serve as an effective proxy for detailed paleo-environment reconstruction of playa evolution, not only in the middle Miocene Ili Basin but also in comparable floodplain/playa lake settings.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Shear fractures that close under compressive stress regime were described by previous workers. Here, we show the existence of hinge-parallel shear-opening mode fractures at a certain depth within an anticline structure, through core observations, Formation Micro Imager (FMI) log interpretations and production data. Studied reservoir is a tight sandstone body of Cretaceous age, which is emplaced in KS2 Anticline, with depth ranging between 6000 and 8100 m. We explore the mechanism of hinge-parallel shear fractures by stereographic technique and backtilting, as well as show field evidences for opening displacements. These shear fractures mainly consist of vertical tension set, moderate-dipping shear set, steeply dipping shear set and sub-horizontal shear set. Crosscutting relationships and surface textures suggest that although the moderate-dipping shear set is older and maybe sealed by cements, it may have been opened by local stress due to outer-arc extension through folding. Calcite bridges with rhombohedral structures may support fracture walls helping them to remain open in case of compressive stress. Our work documents shear fracture openings in the anticline at depth, and fluid flow in subsurface reservoirs.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Alamos Complex is a metamorphosed volcano-sedimentary sequence exposed south of the late Paleozoic Ouachita–Marathon–Sonora orogen in northwestern Mexico, which in turn, is regarded as a continuation of the Alleghenian–Variscan mountain chain. Mineral assemblages in metavolcanic rocks indicate greenschist facies metamorphism. Thermobarometric studies yield an average metamorphic temperature of 380 °C, whereas andalusite in metapelites indicates pressure less than 0.4 ± 0.05 GPa. The main deformation phase generated pervasive foliation, which in turn was isoclinal to close folded and a second axial planar cleavage was developed. Metavolcanic rocks of the Alamos Complex can be separated in two suites: (1) an anorogenic suite, similar to enriched middle ocean basalts (E-MORB) in the Tesia region, and (2) an orogenic suite, characteristic of volcanic-arc setting in the Mocuzari region. U–Pb detrital zircon geochronology of one sample from Tesia yielded a maximum depositional age averaging 395 ± 28 Ma. One sample from the Mocuzari region yielded a maximum depositional age averaging 1104 ± 24 Ma, with the largest peak at 1428. A clastic sequence correlated with the Middle Triassic–Lower Jurassic Barranca Group, nonconformably cover the Alamos Complex. The basal conglomerate of that group yields a maximum depositional age averaging 372 ± 23 Ma. Accordingly, the Alamos Complex must be in part deposited after the early Devonian time and before the Middle Triassic. The main sources of detritus for the complex are the Meso- and Paleoproterozoic rocks of southwestern Laurentia, whereas the main source of detritus for the Barranca Group is the Rio Fuerte Formation exposed ~ 100 km south of the study area. The metamorphic event is ascribed to the late Paleozoic collision of Gondwanan blocks against the southern margin of Laurentia.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Changning-Menglian Belt in western Yunnan, China, has been considered for decades as a remnant of Paleo-Tethys in this region. However, the understanding of the geological evolution of the belt remains sketchy and incomplete. As a significant component of the stratigraphic successions in the eastern part of the belt, the siliciclastic Nanduan Formation preserved essential information of the developing history of the belt. Petrologic studies of the formation show that it was deposited in a neritic environment. The increase of mudstone beds and decrease of grain size of sandstones upwards suggest a gradual deepening of sedimentary environment. Petrographic and geochemical characteristics of sandstones show that they were derived from mature continental provenance and deposited in a passive continental margin setting. Detrital zircon ages of the formation range from 362 to 3685 Ma. The youngest detrital zircon age (362.2 ± 5.5 Ma) confines the deposition age of the sandstones to being younger than the latest Devonian. Dominant age populations of ca. 950 Ma and ca. 550 Ma can be correlated with the magmatic events that occurred in Eastern Ghats-northern Prince Charles (India–Antarctica) (ca. 950 Ma) and Pan-African orogens (Australia–India) (ca. 550 Ma), which are considered, therefore, to be the main provenance of the Nanduan Formation. These results let us consider that the Nanduan Formation and the underlying Lancang Group were formed on the margin of the Baoshan-Shan Block (therefore, autochthonous), and the Carboniferous‒Permian limestones of seamount resemblance, the oceanic bedded cherts, and basic and ultra-basic igneous rocks in the central zone of the belt are overthrusted slices (allochthonous).〈/p〉

Description: Previous palaeomagnetic studies have allowed the recognition of a distinctive area of Neotethyan oceanic rocks, including the Troodos ophiolite in Cyprus and the Hatay ophiolite to the east in southern Turkey, that underwent 90° of anticlockwise rotation between Late Cretaceous (Campanian) and Early Eocene time. The southern and western boundaries of this rotated Troodos–Hatay microplate have been inferred to lie within, or adjacent to, zones of deformed oceanic and continental margin rocks that are now exposed in southern and western Cyprus; however, the northern boundary of the microplate remains undefined. Relevant to this problem, palaeomagnetic data are presented here from basaltic lavas exposed along the Kyrenia Range, mostly from Late Cretaceous (Maastrichtian) sites and one Eocene site. A positive inclination-only fold test demonstrates that remanences are pre-deformational in age, and positive conglomerate tests show that magnetic remanences were acquired before Late Eocene–Early Oligocene time, together suggesting that primary magnetizations are preserved. Data from the eastern Kyrenia Range and the Karpas Peninsula (the easternmost extension of the Kyrenia Range) document significant relative tectonic rotation between these localities, with no rotation in the eastern range versus 30° of anticlockwise rotation of the Karpas Peninsula. Unfortunately, palaeomagnetic sites from the western Kyrenia Range did not yield tectonically interpretable magnetization directions, probably due to complex poly-phase thrusting and folding, and the central range also yielded no interpretable data. However, the available palaeomagnetic data are sufficient to demonstrate that the Kyrenia terrane underwent a separate rotation history to the Troodos–Hatay microplate and also implies that the northern boundary of the Troodos–Hatay microplate was located between the Troodos ophiolite and the Kyrenia Range. The former microplate margin has since been overridden and concealed by two phases of southwards thrusting and folding of the Kyrenia Range units (Mid-Eocene; latest Miocene–earliest Pliocene). The likely cause of the anticlockwise rotation affecting the Karpas Peninsula, and by implication the curvature of the Kyrenia Range as a whole, relates to regional late-stage subduction and diachronous continental collision. The Southern Neotethys sutured in SE Turkey during the Early Miocene, whereas a relict ocean basin remained further west in the easternmost Mediterranean, allowing a remnant N-dipping subduction zone to retreat southwards and so induce the present-day arcuate shape of the Kyrenia Range.

Description: The Sikouzi Section is located towards the northern limits of the East Asian summer monsoon, providing the opportunity of placing the stratigraphic record into the context of the East Asian summer monsoon history. We present here the results of the details of the sedimentology of the Neogene succession of the section and use these to provide insights into the evolving history of the East Asian summer monsoon. The record is marked by a strongly expressed early Miocene lacustrine phase. A well-defined evaporate bed defines the top of the lacustrine succession, marking the onset of more arid conditions during the middle Miocene. The overlying succession is dominated by a series of alluvial packages, extending into the late Pleistocene with varying stratigraphic architectures and including a subordinate lacustrine component. Given the regional setting, the onset of drier conditions during the middle Miocene must relate to a downturn of summer monsoon activity. We focus on the question: what ‘forced’ this palaeoclimate event? Earlier biostratigraphic work places the explanation of this change into the context of the global-scale middle Miocene climate reorganisation. Here we explore this question in the context of regional-scale climate dynamics and propose that the onset of drier conditions over the study area was a response to atmospheric subsidence driven by circulation changes related to the growth of the Tibetan Plateau.

Description: Palaeomagnetic studies of the Neogene–Quaternary rocks of Anatolia have been mostly interpreted in the light of its westward escape as a result of the collision between the Arabian and Eurasian plates along the Bitlis–Zağros suture during the Neotectonic period. However, within the collision zone, in East Anatolia, palaeomagnetic data are not available. In order to help understand the deformational history of Eastern Anatolia during the Neotectonic period, we have carried out a palaeomagnetic study of Miocene–Quaternary volcanic rocks from 100 sites, selected on the basis of their geographical position and known age. The results indicate that the study area can be divided into five principal tectonic blocks, based on earthquake activity and the rotation that the blocks underwent. These blocks are the Van Block (VB), the Kars Block (KB), the Anatolian Block (AB), the Pontide Block (PB), and the Arabian Block (ARB). The largest counterclockwise (CCW) tectonic rotations were encountered in the AB and PB, whereas the largest clockwise (CW) rotations were recorded in the VB. The sinistral East Anatolian Fault and the Erzurum Fault Zone form the present boundary of these two contrasting, CW and CCW-rotating domains. Both the AB and the PB exhibit similar amount of rotation until the Quaternary, during which the AB rotated 13° CCW while the PB remained stable. The Quaternary rotation of the AB is attributed to the activity of the North Anatolian Fault. The KB shows the smallest amount of CW rotation during all of the time intervals studied. All of the blocks studied indicate an acceleration in the amount of rotations during the Quaternary, which was preceded by a period of relative tectonic stability during the Late Pliocene. Following the collision of the Arabian Plate with the Eurasian Plate during the Mid-Miocene, the crust was initially thickened by thrusting and folding. This was followed by lateral extrusion and differential rotation of the crustal blocks during Late Miocene–Pliocene in response to ongoing indentation of the Arabian Plate. Our data show that strike-slip faults that commonly separate wedge-shape crustal blocks are the most significant means of accommodating the tectonic escape and rotation of crustal blocks in East Anatolia. Delamination of the lower crust and the lithospheric mantle may have contributed to the deformation by thermally weakening the crust.