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Abstract: The Xuefengshan Belt, characterized by large-scale fold and thrust structures and widespread granites, is a key area to decipher the tectonic evolution of the South China block. In this belt, two magmatic episodes are recorded by Early Paleozoic and Early Mesozoic granites. In this paper, we carried out precise SIMS zircon U and in situ Lues measurements on these granitic plutons. Our study indicates that the Early Paleozoic and the Early Mesozoic granites are late-orogenic products of the Early Paleozoic orogen and the Middle Triassic Xuefengshan orogen, respectively. In the Xuefengshan Belt, the Early Paleozoic event is poorly registered, since this area corresponds to the outer zone of the early Paleozoic orogen. The Silurian–Early Devonian granites are late-orogenic plutons emplaced after the main tectonic and metamorphic stage in the Wuyi–Baiyun–Yunkai belt, coeval with a widespread, subsequent extensional event in eastern and southern South China. On the other hand, Triassic granites are formed in an intracontinental environment with weakly to strongly peraluminous signatures. Zircon Uresented here, associated with a summary of newly acquired data in the same region, suggest that the emplacement of anatectic granites occurred around 225–215Ma, not in a rather wide range of ca. 245–200Ma. In situ zircon εHf(t) values indicate a crust-derived source without a mantle-derived input for the two generations of granites. Combining our data with recent studies, we infer that the central area of the South China block has experienced two tectonothermal events: the Early Paleozoic magmatism developed as a result of the collapse of the Early Paleozoic orogen, while these Early Mesozoic granites can be the late-orogenic products of the intracontinental Xuefengshan orogen, most likely manifesting the far field effect by the subduction of the Paleo-Pacific ocean plate at the southeastern margin of the South China block. [Copyright &y& Elsevier]

Abstract: This paper reports whole-rock Sr–Nd and zircon U–Pb and Hf isotopic compositions, as well as major and trace element data, for the granodiorites and their mafic microgranular enclaves (MMEs) in the Tuokesalei area, northwestern Chinese Altai. The granodiorites are characterized by peraluminous compositions (A/CNK=1.01–1.45), with relatively high SiO2 (64.4 to 70.9wt.%) and low MgO (0.75 to 1.97wt.%) contents. These rocks possess low total rare earth element (REE) contents (67–187ppm) with weakly negative Eu anomalies and mantle-like whole-rock Nd–Sr isotopic compositions (εNd(t)=+2.5 to +4.5; (87Sr/86Sr)i =0.7038 to 0.7048) and zircon εHf(t) values (+5.93 to +12.9). The MMEs contain abundant magmatic amphiboles and needle-like apatites, have low SiO2 (51.7 to 54.3wt.%) and high MgO (2.86 to 3.75wt.%) and REE contents (162–298ppm), and are characterized by moderately negative Eu anomalies (Eu/Eu*=0.40–0.60) and slightly depleted to enriched LREE ((La/Nd)N =0.74–1.41) and flat HREE ((Gd/Yb)N =1.16–1.39) patterns. The MMEs have whole-rock Nd–Sr isotopic compositions (εNd(t)=+2.6 to +2.7, (87Sr/86Sr)i =0.7034–0.7050) similar to those of the host granodiorites. Their similarities in crystallization age, mineral assemblage and isotopic composition document that the MMEs may represent an early crystallized phase, which was broken into pieces and brought to the shallow level during the host magma ascent and emplacement. Their precursor magmas were probably derived from an oceanic lithospheric mantle, which was characterized by pronounced Nd–Ta depletions. Mineral compositions of MMEs suggest that amphibole was a major early fractional mineral, which effectively differentiated the mantle-derived basaltic liquids to silica-rich melts. Zircon U–Pb dating yielded an age of 313±5Ma for the host granodiorites and 313±13Ma for their MMEs. The geochemical data of this study records an important episode of magmatism in an environment transitional from a subduction-related regime to a post-tectonic extension. Results of this study suggest that the accretionary orogenic process did not completely terminate until the Late Carboniferous to Permian in this region. [Copyright &y& Elsevier]

Abstract: This paper attempts to review the descriptions on the genetic series of neotectonic forms in Eurasia. Morphotectonically, the Eurasian continental block exhibits a radial-concentric pattern consisting of four kinds of tectonic units: platforms, rejuvenated and youthful mobile belts, and the continent-ocean transition zones. Vast areas of young and ancient platforms, such as Siberia, have experienced slow-rate Late-Cenozoic uplift and little interior deformation. The youthful orogenic belts are clustered into the giant Alpine-Himalayan megabelt. The rejuvenated mountain belts are characterized by a variety of structural-morphological types of orogens, such as domelike uplifts, block uplifts and intermountain basins. The continent-ocean transition zones in Eastern Asia, including marginal rifts and extensional basins, are resulted from interaction between the continental block and Pacific Ocean and Philippine Sea since the Late Cenozoic. One of the conspicuous features of Eurasia is that most areas lie in the largest geoid depression of the Earth, and the NS trending Uralian-Oman lineament expresses a break on the geoid slope, implying a relationship to deep structure, including density inhomogeneities, downward to the core-mantle interface. Besides, the Eurasian continent fully demonstrates morphotectonic and recent geodynamic features of the Northern Hemisphere of the Earth, just in contrast to that of the Southern Hemisphere. It is best to view the surface morphotectonics and deep structure of the Earth as a geodynamic ensemble which has spawned the large-scale geomorphic features on the surface. [Copyright &y& Elsevier]

Abstract: This paper presents U–Pb ID-TIMS geochronological data from granitoids in the Hafafit area in the Central and South Eastern Desert, Egypt. It dates several Neoproterozoic magmatic pulses and metamorphic events, and constrains one episode of U, Nb and Ta mineralisation along the Nugrus Shear Zone, part of the Eastern Desert Shear Zone, to 608±1Ma. The data testify to the localized nature of deformation in the Eastern Desert, illustrating that previous subdivisions of granitoids into “Older” and “Younger” based on field criteria are inadequate. With robust ages from granitoids in the Meatiq, El Sibai and El Shalul areas the new ages indicate 6 pulses of magmatism and/or metamorphism at (1) 705–680, (2) c. 660, (3) 635–630, (4) 610–604, (5) 600–590 and (6) c. 540Ma. Most pulses are defined by ages from granitoids in both gneiss windows/domes and in the overlying eugeoclinal allochthon; the two tiers represent different crustal levels of related rocks. We propose that pulses 1–3 are syn-orogenic, pulses 4 and 5 reflect exhumation of mid-crustal gneisses along the Eastern Desert Shear Zone, whereas the final pulse post-dates the East African orogeny. Based on available data we propose that the tectono-magmatic evolution above applies to the entire Eastern Desert. [Copyright &y& Elsevier]

Understanding of seismicity and seismotectonics of Delhi and adjoining areas is essential as these areas lie in the seismic zone IV and are geologically confined to the Delhi Fold Belt (DFB), juxtaposed to the Himalayan Frontal Thrust Fold Belt. Owing to the set-up, seismicity in this area is ascribed to the Himalayan Thrust System and activation of DFB Fault Systems. Considerably improved instrumental seismic monitoring in this area and data analysis had resolved three regions of pronounced seismicity that lie close to Sonepat, Rohtak and western part of the NCT Delhi, attributed to activation of various portions of the fault systems of the DFB. Based on seismic telemetry network data, the seismicity pattern analysis revealed that the Mahendragarh Dehradun Sub-Surface Fault (MDSSF) and Delhi Sargodha Ridge (DSR) are the two major zones of structural importance for the nucleation of seismicity in this region. These revelations were corroborated with the fault plane solution of the earthquakes. The dominant mechanism in nucleation of seismicity in DFB is the thrust with minor strike slip. The seismicity and seismotectonics of Delhi and adjoining areas endemic to activation of DFB is reviewed and presented in this paper. [ABSTRACT FROM AUTHOR]

The western Lucretili Mts. in the central Apennines (Latium, Italy) have been recently re-mapped in great detail and are the subject of combined stratigraphic, sedimentological and structural investigations. In this paper, we present a new stratigraphic interpretation of the Jurassic paleogeography of western Lucretili Mts., where a rift-derived intrabasinal paleo-high of the Alpine Tethys has been identified for the first time by means of facies analysis and biostratigraphic dating. Recognised facies associations, combined with dated stratigraphic sections, allow to define the morphology of the structural paleo-high and to identify the associated gravity-driven deposits (olistoliths) accumulated in the surrounding basin. Furthermore, we investigated the modes of interaction between Jurassic extensional structures and the subsequent contractional patterns developed during the Tertiary mountain building. In detail, the role played during Apennines tectonics by the paleo-escarpments bounding the paleo-high and by the surrounding olistoliths has been analysed. The paleo-escarpments either acted as focussing features for ENE-directed frontal thrust ramp localisation and were offset with small shortening amounts or reactivated as NNE striking high angle transpressional faults or preserved the original geometries as a result of variable orientation of paleo-escarpments with respect to the Neogene compressive stress field (with ENE oriented sigma1). Newly formed ENE striking tear faults connect these either inherited or neo-formed discontinuities. This complex stratigraphic and structural pattern is substantially different from the previous interpretations of this portion of the central Apennines based on a hypothesised layer-cake stratigraphy deformed by neo-formed Neogene thrusts. This contribution strengthens the importance of integrating facies analyses and structural investigations to detect the influence of pre-orogenic structures on compressive structural patterns, in an area where commercial seismic lines are not available and cannot help in reconstructing the subsurface geometries. [ABSTRACT FROM AUTHOR]

The North Xinjiang region (NW China) is an important part of the Central Asia Orogenic Belt, situated at the junction of Siberia, Tarim and Kazakhstan plates. It is an area characterized by multiple stages of Phanerozoic continental growth, during which several porphyry and epithermal systems were formed. The relationship of these mineral systems to the geodynamic evolution of the region has not yet been well understood. In this paper, we list the main geological characteristics of 21 significant epithermal precious and base metal deposits in North Xinjiang, and classify them into high-sulfidation and low-sulfidation styles, with the latter being predominant. We have selected seven epithermal deposits representing different styles formed under different tectonic regimes and discuss their geology and geochemistry in some detail. The deposit-scale geology and geochemistry of epithermal systems in North Xinjiang are essentially similar to those in other parts of the world. All epithermal deposits in North Xinjiang are hosted in volcanic rocks with ages ranging from Devonian to Triassic, with the Early Carboniferous volcanic sequences being the most important, followed by the Permian and Triassic. The Devonian-Early Carboniferous host rocks belong to the calc-alkaline series that developed in pre-collisional arc-back-arc basin systems; whereas the Permian-Triassic host volcanic rocks of shoshonite series formed in post-subduction regimes. Available isotopic ages of these epithermal systems cluster in two periods: Early Carboniferous (>320 Ma) and Late Carboniferous-Triassic (320-220 Ma), reflecting two metallogenic episodes that occurred during subduction-related accretion and post-subduction collision regimes, respectively. Accordingly, three groups of epithermal deposits in North Xinjiang can be recognized as (1) pre-collisional deposits without or with negligible collisional-related modification, (2) deposits formed in collision regime and (3) ore systems strongly overprinted by fluid flow in post-subduction collision regime. [ABSTRACT FROM AUTHOR]

Abstract: The assembly of the Corsica–Sardinia Batholith (C–SB) coincides with final shaping of the Variscan belt and represents a key structure to unravel the feedbacks between partial melting, rheology and the evolution of collisional orogens. This paper presents a model for the genesis of the Arzachena pluton (AZN), one of the major calc-alkaline massifs of the C–SB, based on U–Pb zircon dating, thermobarometry and structural analysis. Major and trace element compositions indicate that AZN has hybrid characteristics between that of typical S- and I-type granites, that could be explained in terms of incremental melting of a heterogeneous crustal source made of metatexites and Ordovician calc-alkaline granitoids. Growth of the pluton started around 320–315Ma with the emplacement at middle crustal level (0.37–0.4GPa) of granodioritic melts within narrow, conjugate, NW–SE sinistral and E–W dextral shear zones. The main growth stage (311+6/−4Ma) is marked by emplacement of large volumes of monzogranitic melts that induced a local decrease of the crustal strength expressed by horizontal channel flow driven by the gravity. Finally (307.6±3.5Ma), leucogranites emplaced within radial and peripheral dilatant fractures developed during the cooling of the main body. The transition from magmatic to sub-magmatic and HT-solid state fabric observed throughout AZN indicates that deformation plays a non-trivial role during the growth of the magmatic system. Restoring the position of the Corsica–Sardinia block to early Permian coordinates allow to recast the birth of the C–SB in a consistent geodynamic framework that conciliates the development of conjugates strike-slip structures, the oroclinal bending of the chain and the thermal relaxation. This study indicates that the C–SB had an active role during post-orogenic extension rather than being just a consequence of it. [Copyright &y& Elsevier]

Abstract: Alpine orogens in the central Mediterranean region have revealed the concomitance of crustal extension in back-arc domain and crustal shortening in frontal domain. Quantitative data of deformation in the frontal orogenic wedges are necessary to understand how the shortening-extension pair evolves in terms of structures, orogenic transport, timing, and exhumation rate. This paper deals with kinematics and ages of the frontal thrust systems of the Calabria-Peloritani Arc (Italy) exposed in the eastern Sila Massif. We first present structural fieldwork, onshore and offshore well log data, and new apatite fission-track (AFT) thermochronology. Then, we describe the structural architecture of the studied area as an ENE-verging stacking of thrust sheets involving basement units and syn-orogenic sediments. The AFT study documents that thrust sheets entered the partial annealing zone from 18Ma to 13Ma. This Early-Middle Miocene thrusting phase was coeval with exhumation of high-pressure/low temperature metamorphic rocks in the hinterland of the orogen (Coastal Chain area), mainly driven by top-to-the-W extensional tectonics. Opposite kinematic shear senses (contractional top-to-the-E and extensional top-to-the-W) and different exhumation rates (slow in the frontal, more rapid in the hinterland) are framed in a tectonic scenario of a critically tapered orogenic wedge during the eastward retreating of the Apennine slab. [Copyright &y& Elsevier]

Abstract: This paper presents the first report on the occurrence of eclogite from the Kumon range of the Western province in Myanmar, which is in the southeastern extension of the Himalayan orogenic belt. The eclogite is mainly composed of omphacite, garnet, hornblende/edenite/katophorite/taramite, biotite, quartz, and rutile. The garnet grains in the eclogite usually show textures of barrier reef, atoll, and table reef types, and have a wide compositional range of Alm58–70Sps1–2Prp9–16Grs14–31. Omphacite grains that occur as garnet inclusions and as isolated crystals in the matrix have similar compositions of Jd34–45 and Jd37–44, respectively. Lesser amounts of jadeitic clinopyroxene (Jd21–38), phengite, biotite, albite, and quartz occur in the lagoon of barrier reef and atoll garnet grains. The matrix omphacite is partly replaced by symplectite of sodic clinopyroxene of Jd20–29 and albite. The lower limits of the pressure/temperature during the eclogite stage, which are defined by the assemblage of garnet, omphacite (Jd40–45), and quartz, are 1.2–1.3GPa/530–615°C. The finding of eclogite from Myanmar suggests the possibility of a wide occurrence of high-pressure metamorphic rocks in the ophiolite zone along the southeastern extension of the Indus-Yarlung Zangbo suture in Myanmar and Indochina. [Copyright &y& Elsevier]

Abstract: Seismic reflection profiles crossing the area bounded by the M. Kumeta Ridge and the M. Maranfusa-M. Galiello-Rocca Busambra morphostructural feature (central-western Sicily) were used to constrain the deep structural setting of the Sicilian–Maghrebian fold-and-thrust belt (FTB). By integrating seismic, field and well data, we attempted to correlate outcropping and deep-seated contractional structures, shedding light on the internal geometries of the thrust system. Results of the new seismostratigraphic analysis presented in this paper reveal structural variations along the tectonic edifice. This suggests dividing the study area into two sectors: the western sector is characterized by foreland-verging thrusts comparable to the already known structural model of the chain, conversely in the easternmost sector duplexes and hinterland-verging structures, here highlighted for the first time, prevail. In fact, the main carbonate relief of this area (Rocca Busambra Ridge) appears as the outcropping part of a thick tectonic pile bounded on its northern side by a high-angle backthrust, while at depth a blind southern verging (i.e. forelandward) thrust can been recognized; this structural setting suggests that underthrusting of the buried S-verging carbonate body induced the N-verging (i.e. hinterlandward) dislocation of the overlying units. On the whole, this structure can be interpreted as a triangle zone, where the outcropping relief represents a passive-roof duplex bounded, on its northern side, by the high-angle backthrust deeply connected with a low-angle décollement layer. The recognized backthrust appears as the product of a deep-seated tectonic activity, that played a key role for the upper thrust-sheet emplacement. [Copyright &y& Elsevier]

Ophiolites are fragments of the ancient oceanic lithosphere formed at constructive plate margins or transforming divergent plates. Through extensive thrust faults, these bodies or part of them are emplaced into the continental crust, inside rock piles of orogenic belts, in solid state, but these bodies can be relatively warm. The possible environments which produce oceanic lithosphere include meso-oceanic ranges, basins related to juvenile island arcs and retro-arc basins. Ophiolites of the Phanerozoic age are abundant in orogenic belts around the world whilst Precambrian oceanic remnants are less common and are distributed mainly in Finland, Canada, Morocco, Saudi Arabia, Egypt, Russia, Brazil and China. Several registers of Precambrian oceanic remnants of different ages were recognized in Brazil. Most of these bodies are situated in Brazilian orogenic belts and they register the consumption of the Neoproterozoic oceans. This paper aims to synthetize the main information about ophiolitic sequences, bringing a brief review of concepts and classifications along the 200-year use of this term. [ABSTRACT FROM AUTHOR]

The Permian Kalatongke Ni-Cu deposits in the Central Asian Orogenic Belt are among the most important Ni-Cu deposits in northern Xinjiang, western China. The deposits are hosted by three small mafic intrusions comprising mainly norite and diorite. Its tectonic context, petrogenesis, and ore genesis have been highly contested. In this paper, we present a new model involving slab window magmatism for the Kalatongke intrusions. The origin of the associated sulfide ores is explained in the context of this new model. Minor amounts of olivine in the intrusions have Fo contents varying between 71 and 81.5 mol%, which are similar to the predicted values for olivine crystallizing from coeval basalts in the region. Analytic modeling based on major element concentrations suggests that the parental magma of the Kalatongke intrusions and the coeval basalts represent fractionated liquids produced by ∼15% of olivine crystallization from a primary magma, itself produced by 7-8% partial melting of depleted mantle peridotite. Positive ε values (+4 to +10) and significant negative Nb anomalies for both intrusive and extrusive rocks can be explained by the mixing of magma derived from depleted mantle with 6-18% of a partial melt derived from the lower part of a juvenile arc crust with a composition similar to coeval A-type granites in the region, plus up to 10% contamination with the upper continental crust. Our model suggests that a slab window was created due to slab break-off during a transition from oceanic subduction to arc-arc or arc-continent collision in the region in the Early Permian. Decompression melting in the upwelling oceanic asthenosphere produced the primary magma. When this magma ascended to pond in the lower parts of a juvenile arc crust, it underwent olivine crystallization and at the same time triggered partial melting of the arc crust. Mixing between these two magmas followed by contamination with the upper crust after the magma ascended to higher crustal levels formed the parental magma of the Kalatongke intrusions. The parental magma of the Kalatongke intrusions was saturated with sulfide upon arrival primarily due to olivine fractional crystallization and selective assimilation of crustal sulfur. Sulfide mineralization in the Kalatongke intrusions can be explained by accumulation of immiscible sulfide droplets by flow differentiation, gravitational settling, and downward percolation which operated in different parts of the intrusions. Platinum-group element (PGE) depletion in the bulk sulfide ores of the Kalatongke deposits was due to depletion in the parental magma which in turn was likely due to depletion in the primary magma. PGE depletion in the primary magma can be explained by a relatively low degree of partial melting of the mantle and retention of coexisting sulfide liquid in the mantle. [ABSTRACT FROM AUTHOR]

The Cap-Chat mélange is a regional-scale dismembered unit that occurs close to the Quebec Appalachian front. The mélange records early (D1, Taconian) and late (D3, Acadian) regional deformations. The greater degree of disruption of the mélange compared with surrounding units is due to the superimposition of D2 structures that are rare outside the mélange. D2 structures include both layer-extensional features such as block disruption along shear zones and faults and layer-contractional features such as folds that record the transtensional collapse of the Taconian orogenic wedge along a rheologically weak deformation zone. The Cap-Chat mélange is interpreted as the westernmost remnant of a zone of mechanical decoupling in the upper crust, which allows normal or transtensional faulting in the inner parts of the orogen. This paper presents evidence that beyond the general complexity of mélange units, geological observations may still contribute to unraveling their tectonic history and that transtensional reactivation of original thrust faults is a viable mechanism in the frontal parts of orogens. [ABSTRACT FROM AUTHOR]

Abstract: The Tarim Block is an important tectonic unit to understand the Proterozoic tectonic framework of the Central Asian Orogenic Belt and the supercontinent Rodinia. The granitic, dioritic, gabbroic intrusive rocks and volcanic–volcanoclastic rocks are widely distributed in the Quruqtagh domain of NE-Tarim. The precise ages of these rocks and their tectonic implications in this part of the world are not well understood. This paper reports geochronological data of gabbro, diorite and granitic rocks from Quruqtagh. LA ICPMS U–Pb zircon ages suggest that numerous of gabbroic and granitic rocks were mainly crystallized at ca. 800Ma. New geochronological data from the magmatic zircons of gabbro, granite and paragneiss can be preliminarily divided into four groups, which are (1) 2469±12Ma or 2470±24Ma, (2) 933±11Ma to 1048±19Ma, (3) 806±8Ma, 798±7Ma, 799±24Ma, 698±51Ma (lower intercept age of the paragneiss), and (4) 1930Ma (upper intercept age of the paragneiss), respectively. These age data are consistent with four tectono-thermal events that took ever place in the Tarim Block. The 93 U–Pb age data (seven for average Concordia age from seven igneous plutons, 86 for xenocrystic and metamorphic ones) from eight samples can be divided into four evolutionary stages: 2360–2550Ma (peak of 2510Ma), 1800–2020Ma (peak of 1870Ma), 860–1140Ma (peak of 920Ma) and 680–840Ma (peak of 800Ma), respectively. The age peak of 2500Ma, consistent with characteristic period of a global building-continent event, indicates that the late Neoarchean–early Paleoproterozoic magmatism had been ever taken place in Tarim. Two peaks at 1870Ma and 920Ma, being two assembly periods of the middle Paleoproterozoic Columbia and the Neoproterozoic Rodinia supercontinents, suggest that Tarim had connections with both Columbia and Rodinia, whereas structural evidence of these two events is absent in Tarim. Notable peak of 800Ma is interpreted as a response to the break-up of Rodinia supercontinent. The geological indicators of break-up such as Neoproterozoic granite, bimodal igneous rocks, composite magmatic flow, basic dyke swarm and continental rift type basins are well developed, followed by a large-scale of late Neoproterozoic glacier event. Four stages of magmatism mentioned above constitute major events in the Precambrian evolution of Tarim and Central Asian. These data, combining with previous U–Pb ages from igneous rocks, provide a significant line of evidence for understanding the Rodinia evolution of Tarim and the relationships with South China, east India and east Antarctica, Lesser and Great Himalaya blocks in Proterozoic. A primary reconstruction of the Tarim Block, connecting it with South China, east India and east Antarctica, Lesser and Great Himalaya blocks, is finally proposed. [Copyright &y& Elsevier]

Abstract: The NWW-striking Qinling Orogen formed in the Triassic by collision between the North China and Yangtze Cratons. Triassic granitoid intrusions, mostly middle- to high-K, calc-alkaline, are widespread in this orogen, but contemporaneous intrusions are rare in the southern margin of the North China Craton, an area commonly considered as the hinterland belt of the orogen. In this paper, we report zircon U–Pb ages, elemental geochemistry, and Sr–Nd–Hf isotope data for the Laoniushan granitoid complex that was emplaced in the southern margin of the North China Craton. Zircon U–Pb dating shows that the complex was emplaced in the late Triassic (228±1 to 215±4Ma), indicating that it is part of the post-collisional magmatism in the Qinling Orogen. The complex consists of, from early to late, biotite monzogranite, quartz diorite, quartz monzonite, and hornblende monzonite, which span a wide compositional range, e.g., SiO2 =55.9–70.6wt.%, K2O+Na2O=6.6–10.2wt.%, and Mg# of 24 to 54. The biotite monzogranite has high Al2O3 (15.5–17.4wt.%), Sr (396–1398ppm) and Ba (1284–3993ppm) contents and relatively high La/Yb (mostly 14–30) and Sr/Y (mostly 40–97) ratios, but low Yb (mostly 1.3–1.6ppm) and Y (mostly14–19ppm) contents, features typical of adakitic rocks. The quartz monzonite, hornblende monzonite and quartz diorite have a shoshonitic affinity, with K2O up to 5.58wt.% and K2O/Na2O ratios averaging 1.4. The rocks are characterized by strong LREE/HREE fractionation in chondrite-normalized REE pattern, without obvious Eu anomalies, and show enrichment in large ion lithophile elements but depletion in high field strength elements (Nb, Ta, Ti). The biotite monzogranite (228Ma) has initial 87Sr/86Sr ratios of 0.7061 to 0.7067, ε Nd(t) values of −9.2 to −12.6, and εHf(t) values of −9.0 to −15.1; whereas the shoshonitic granitoids (mainly 217–215Ma) have similar initial 87Sr/86Sr ratios (0.7065 to 0.7075) but more radiogenic ε Nd(t) (−12.4 to −17.0) and εHf(t) (−14.1 to −17.0). The Sr–Nd–Hf isotope data indicate that the rocks were likely generated by partial melting of an ancient lower continental crust with heterogeneous compositions, as partly confirmed by the widespread presence of early Paleoproterozoic inherited zircons. Mafic microgranular enclaves (MMEs), characterized by fine-grained igneous textures and an abundance of acicular apatites, are common in the Laoniushan complex. Compared with the host rocks, they have lower SiO2 (48.6–53.7wt.%) and higher Mg# (51–56), Cr (122–393ppm), and Ni (24–79ppm), but equivalent Sr–Nd isotope compositions, indicating that the MMEs likely originated from an ancient enriched lithospheric mantle. The abundance of MMEs in the granitoid intrusions suggest that magma mixing plays an important role in the generation of the Laoniushan complex. Collectively, it is suggested that the Laoniushan complex was a product of post-collisional magmatism related to lithospheric extension following slab break-off. Formation of the adakitic and shoshonitic intrusions in the Laoniushan complex indicates that the Qinling Orogen had evolved into a post-collisional setting by about 230–210Ma. [Copyright &y& Elsevier]

Abstract: The Beishan orogen is situated in the southern margin of the Central Asian Orogenic Belt (CAOB). It is connected with the Tianshan orogen to the west and the Mongolia-Xing’anling orogen to the east. This orogen exhibits a well-preserved Neoproterozoic to Late Paleozoic sequence containing ophiolites, accretionary complexes and eclogites. In this paper we provide new geochronological data for eclogites and their country paragneiss to constrain the tectonic evolution of the Beishan orogen. U–Pb zircon dating of eclogites yielded two concordant ages, 886±4Ma for the cores and 465±10Ma for the rims. The zircon cores display bright luminescence with homogeneous or planar/sector zoning, intermediate Th/U ratios (0.17–0.47), and HREE-enriched patterns with negative Eu anomalies (Eu/Eu* =0.16–0.58). These features, coupled with their formation temperatures of 680–710°C, suggest that the core age represents the time of an earlier upper amphibolite facies metamorphic episode. By contrast, the zircon rims have dark luminescence with homogeneous or fir-tree zoning, low Th/U ratios (<0.02), and flat HREE distributions with small or no negative Eu anomalies (Eu/Eu* =0.55–1.16). Thus, the rim age reflects the time of the eclogite facies metamorphism. The occurrence of tiny inclusions of garnet, omphacite and rutile in the zircon rims is consistent with the above age interpretation. In addition, the mineral inclusions and host zircons yielded P–T conditions of 660°C and >12 kbar for the eclogite facies metamorphism. On the other hand, zircon dating of a paragneiss near the eclogite produced two major groups of ages, ca. 1450Ma for a magmatic event and ca. 900Ma for a metamorphic event. It seems that eclogites and their country rocks have suffered the same earlier metamorphic episode. Based on the available age data obtained for eclogites, ophiolites and granitoids from the Beishan area, a tectonic scenario can be constructed as follows. The ca. 1000Ma oceanic crust representing by protoliths of the eclogites was involved in Early Neoproterozoic orogenesis to have formed a microcontinental block. During the Early Paleozoic, island arcs and microcontinental blocks were progressively accreted to the northern margin of the Tarim craton (Dunhuang block). This was followed by the closure of Paleoasian Ocean and final amalgamation between the Tarim craton and Kazakhstan block in the Late Paleozoic. [Copyright &y& Elsevier]

This paper presents a synthetic view of the geodynamic evolution of the Zagros orogen within the frame of the Arabia–Eurasia collision. The Zagros orogen and the Iranian plateau preserve a record of the long-standing convergence history between Eurasia and Arabia across the Neo-Tethys, from subduction/obduction processes to present-day collision (from ~ 150 to 0 Ma). We herein combine the results obtained on several geodynamic issues, namely the location of the oceanic suture zone, the age of oceanic closure and collision, the magmatic and geochemical evolution of the Eurasian upper plate during convergence (as testified by the successive Sanandaj–Sirjan, Kermanshah and Urumieh–Dokhtar magmatic arcs), the P–T–t history of the few Zagros blueschists, the convergence characteristics across the Neo-Tethys (kinematic velocities, tomographic constraints, subduction zones and obduction processes), together with a survey of recent results gathered by others. We provide lithospheric-scale reconstructions of the Zagros orogen from ~ 150 to 0 Ma across two SW–NE transects. The evolution of the Zagros orogen is also compared to those of the nearby Turkish and Himalayan orogens. In our geotectonic scenario for the Zagros convergence, we outline three main periods/regimes: (1) the Mid to Late Cretaceous (115–85 Ma) corresponds to a distinctive period of perturbation of subduction processes and interplate mechanical coupling marked by blueschist exhumation and upper-plate fragmentation, (2) the Paleocene–Eocene (60–40 Ma) witnesses slab break-off, major shifts in arc magmatism and distributed extension within the upper plate, and (3) from the Oligocene onwards (~ 30–0 Ma), collision develops with a progressive SW migration of deformation and topographic build-up (Sanandaj–Sirjan Zone: 20–15 Ma, High Zagros: ~12–8 Ma; Simply Folded Belt: 5–0 Ma) and with partial slab tear at depths (~10 Ma to present). Our reconstructions underline the key role played by subduction throughout the whole convergence history. We finally stress that such a long-lasting subduction system with changing boundary conditions also makes the Zagros orogen an ideal natural laboratory for subduction processes. [ABSTRACT FROM AUTHOR]

Abstract: The Tianyu mafic–ultramafic intrusion is one of many important sulfide-bearing mafic–ultramafic intrusions in the eastern Tianshan terrane located in the southern margin of the Central Asian Orogenic Belt in north Xinjiang, NW China. The origin of sulfide mineralization in these intrusions, their relationship with Permian basalts and A-type granites, and the geodynamic setting of the bimodal magmatism in the region are controversial. In this paper we use zircon U–Pb age, Hf–Sr–Nd–Os isotope and lithophile–chalcophile trace element constraints from the Tianyu mafic–ultramafic intrusion to address these important issues. The U–Pb age of zircon from the Tianyu intrusion determined by SIMS is 280±2Ma. This confirms that the Tianyu intrusion is coeval with most sulfide-bearing mafic–ultramafic intrusions and some basalts and A-type granites in the Tianshan region. Similar to coeval basalts in the nearby Tuha basin, the Tianyu intrusive rocks are characterized by negative Nb anomaly and elevated εNd values varying between −1 and +4.6. The negative Nb anomaly in the Tianyu intrusion is not as pronounced as in the coeval A-type granites but the εNd values for these bimodal rocks are similar. The εHf values of zircon from the Tianyu intrusion are positive, varying between 3 and 8. These values suggest that the parental magma of the Tianyu intrusion was dominated by melt derived from a depleted source mantle. The γOs values of pyrrhotite from the Tianyu intrusion are high, ranging from 725 to 995, which can be modeled by selective assimilation of sulfide from the lower and upper crusts. Negative Pt anomaly is present in relatively sulfide-rich samples such as semi-massive and massive sulfide ores but not in sulfide-poor samples, which is more consistent with the effect of post-magmatic hydrothermal alteration than the original signature of the parental magma. The results of modeling using the compositions of selected disseminated sulfide samples suggest that the parental magma of the Tianyu intrusion was depleted in all PGE, which is consistent with previous sulfide segregation at depth. Our data and modeling results support the model of decompression melting of upwelling asthenosphere due to slab break-off during a transition from oceanic subduction to arc–arc or arc–continent collision in the Permian. Decompression melting of the upwelling asthenosphere in the region produced mafic magma. Partial melting in the lower parts of a juvenile arc crust due to mafic magma underplating produced granitic melts. Mixing of the mafic magma with a small amount of granitic melts at depth followed by contamination with the upper crust at a higher level formed the parental magma of the Tianyu intrusion. PGE depletion in the parental magma of the Tianyu intrusion can be attributed to sulfide segregation associated to the first stage of crustal contamination at depth. We suggest that the formation of sulfide ores in the intrusion was related to the second stage of crustal contamination in the upper crust. [Copyright &y& Elsevier]

Abstract: The structure of the Lower–Middle Ordovician Tuloi and Karasa Formations, which occur widely in northeastern Gorny Altai, has been studied. A bed-by-bed description of a new section of the boundary sediments between these stratigraphic units has been given. The graptolite, trilobite, and brachiopod assemblages typical of the Tuloi and Karasa Formations have been analyzed. Graptolite zones and subzones have been recognized, which permit correlating the stratotype and key sections of these local stratigraphic units with the stages of the International Stratigraphic Chart (ISC). The Karasa Formation occupies a considerably larger stratigraphic volume than presumed: It spans the late Arenig and the entire Llanvirn (including the Llandeilo) of the British standard, which is used in Russia (=Upper Dapingian–Darriwilian of the new Ordovician standard in the ISC). Finally, the paper discusses the suggested changes in the names of regional stratigraphic units (horizons) in the Ordovician stratigraphic chart of the western Altai–Sayan fold belt. [Copyright &y& Elsevier]

The Austroalpine nappe systems in SE-Switzerland and N-Italy preserve remnants of the Adriatic rifted margin. Based on new maps and cross-sections, we suggest that the complex structure of the Campo, Grosina/Languard, and Bernina nappes is inherited largely from Jurassic rifting. We propose a classification of the Austroalpine domain into Upper, Middle and Lower Austroalpine nappes that is new because it is based primarily on the rift-related Jurassic structure and paleogeography of these nappes. Based on the Alpine structures and pre-Alpine, rift-related geometry of the Lower (Bernina) and Middle (Campo, Grosina/Languard) Austroalpine nappes, we restore these nappes to their original positions along the former margin, as a means of understanding the formation and emplacement of the nappes during initial reactivation of the Alpine Tethyan margin. The Campo and Grosina/Languard nappes can be interpreted as remnants of a former necking zone that comprised pre-rift upper and middle crust. These nappes were juxtaposed with the Mesozoic cover of the Bernina nappe during Jurassic rifting. We find evidence for low-angle detachment faults and extensional allochthons in the Bernina nappe similar to those previously described in the Err nappe and explain their role during subsequent reactivation. Our observations reveal a strong control of rift-related structures during the subsequent Alpine reactivation on all scales of the former distal margin. Two zones of intense deformation, referred to as the Albula-Zebru and Lunghin-Mortirolo movement zones, have been reactivated during Alpine deformation and cannot be described as simple monophase faults or shear zones. We propose a tectonic model for the Austroalpine nappe systems that link inherited, rift-related structures with present-day Alpine structures. In conclusion, we believe that apart from the direct regional implications, the results of this paper are of general interest in understanding the control of rift structures during reactivation of distal-rifted margins. [ABSTRACT FROM AUTHOR]

Abstract: It is well accepted that the North China Craton formed by assembly of the Eastern and Western blocks along the Trans-North China Orogen, with cratonization in the Paleoproterozoic (∼1.85Ma). However, there is controversy about the formation of the Eastern and Western blocks themselves, especially the timing of cratonization of the Eastern Block. The Jiao-Liao-Ji orogenic belt is the most important Paleoproterozoic Orogenic belt in the Eastern Block and consists mainly of the North and South Liaohe Groups and the Liaoji Granitoids. The timing of metamorphism of the Liaohe Group is the key to understanding the evolution of the Eastern Block of the North China Craton. Because the isotope systematics of metamorphic minerals can be used to date parts of the prograde thermal histories of metamorphic belts, dating of minerals, such as garnet and staurolite has the distinct advantage that time information can be related directly to the pressure–temperature-deformation history recorded by the same mineral. In this paper we present results of precise 207Pb/206Pb stepwise-leaching (PbSL) dating of garnet and staurolite from the metasedimentary rocks of the south Liaohe Group. The primitive Pb and radiogenic Pb are selectively extracted from garnet and straurolite by leach steps and determined by multiple collector (MC-) ICP-MS. The garnet and staurolite record two groups of 207Pb/206Pb ages, at 1.93–1.91Ga and ∼1.86Ga, respectively. These constrain the time of peak metamorphism of the Liaohe Group during collision between the Longgang Block in the north and the Liaonan (Nangrim) Block in the south and a subsequent post-collisional event, respectively. Our data for the South Liaohe Group and previously published data for the Liaoji Granite, combined with key lithological, structural and metamorphic information, indicate that the cratonization of the Eastern Block of the North China Craton occurred at 1.93–1.91Ga. [Copyright &y& Elsevier]

Abstract: We have found a new source of information about what lies beneath the Kalahari sands. The Kheis and Rehoboth Provinces of southern Africa were thought to be underlain by either an ~1800Ma orogenic belt, or a northern branch of the ~1200Ma Namaqua–Natal Province. Glacial diamictites of the Permocarboniferous Dwyka Group exposed at Rietfontein west of the Kalahari sands carry cobbles plucked from the bedrock by the ice sheet which covered the Gondwana supercontinent about 300Ma ago. Despite altered mineralogy, the cobbles are not severely altered geochemically. Their normative mineral compositions give classifications as trondhjemites and granites, supported by rare earth element diagrams. Microbeam U–Pb zircon dating of the granitic cobbles shows that they contain no evidence of crustal growth or orogeny at either 1800 or 1200Ma. Rather they testify to the presence of 2500 to 2900Ma Archaean trondhjemitic and granitic crust beneath the Kalahari, with a lesser ~2050Ma granite component. The pebble assemblages from the diamictites we sampled lack the diagnostic banded iron formation (BIF), stromatolitic limestone and other supracrustal pebbles which characterise diamictites derived from the Kaapvaal Craton, thus we envisage shorter transport distances and derivation from the region now beneath the Kalahari sands. Three of the Archaean granite cobbles have unusual less-than-mantle zircon oxygen isotope values around +3 (δ18O VSMOW), which may reflect interaction of their source with high-temperature, originally meteoric water before melting to produce the granites. The mafic cobbles described in a companion paper are much younger and are related to intrusions of the 1.1Ga Umkondo Large Igneous Province, probably located on the Kalahari Line or Rehoboth Province. Five trondhjemitic granites from the westernmost outcrops of the Kaapvaal Craton were dated, the oldest being 3061±9Ma and four others between 2882±7Ma and 2854±7Ma, reflecting the cratonisation of the Kimberley Terrane. Four of the Archaean Dwyka cobbles we dated are younger than the 2.7Ga Kaapvaal cover sequence and are thus too young to be derived from the craton. All the Dwyka cobbles described here are most likely derived from either the Rehoboth Province or the Kalahari Line with origins from the Kheis Province, Kaapvaal Craton, or further afield considered unlikely. We envisage the Rehoboth Province to consist of an Archaean core supplemented by Palaeoproterozoic granitoids, which was joined to the Kaapvaal Craton at an early stage of crustal development and played an important role during later tectonic events. This has important implications not only for the tectonic framework and assembly of Southern Africa, but also for exploration for diamonds and other ore deposits. [Copyright &y& Elsevier]

Abstract: The middle Medjerda valley belongs to the Tellian zone of Tunisia; it behaves as a post-orogenic basin where surface structural indices are almost completely absent. It is noteworthy to recall that Alpine and Atlasic tectonic prints are well expressed on both sides of this basin. This paper presents an integrated study comprising geology and gravity data. Subsurface geological modeling was based on gravity data interpretation including the complete Bouguer anomaly, upward continuation, residual and derivatives. 2.5D gravity modeling was essential for subsurface geometric features characterization. In spite of its sub-horizontal and smooth topography and the low density of the homogenous Quaternary series covering the area, well contrasted and variable gravity responses are observed reflecting the heterogeneities of the geological substratum. The enhanced horizontal gravity gradient confirms structural systems that are already evidenced by surface geology. It supports, also, the presence of new masked fault systems. The main structural features inferred are (i) NW directed Grabens located at Mellegue and S. ez Zaouam depressions, (ii) Triassic diapirs associated to NE thrust faults of El Merdja, Bousalem, Ben Bechir and Mjez el Assa. These structures are generally covered by the Quaternary series. The presence of both distensive and compressive structures within a compressive regime is explained by the solicitation of preexisting fault systems in the area. During the NW directed shortening occurred at the Upper Miocene age, the geodynamic evolution of Northern Tunisia was dominated by strike-slip thrust movements through the reactivation of deep major inherited faults: e.g. (i) the dextral EW oriented fault system of Ghardimaou-Thibar, and (ii) the sinister NS accident of Dehmani–Bousalem–Ras Rajel. These accidents shaped the Medjerda basin and contribute to its complex geological architecture. [Copyright &y& Elsevier]

In a recent work, Dey et al. (Environ Earth Sci 59:353-361, ) presented some new observations on the southern part of one of the anticlinal ridges of Tripura, viz. the Baromura range. The work incorporated a number of irregularities and misinterpretations that need to be addressed to avoid future confusion. The present article critically reviews Dey et al.'s paper to bring out its inaccuracies. [ABSTRACT FROM AUTHOR]

This paper presents the results of Sm-Nd isotopic-geochemical and U-Pb geochronological studies of metamorphic (Ilikan Sequence) and associated igneous rocks from the Ilikan lithotectonic zone (terrane) located in the Dzhugdzhur-Stanovoi Superterrane from the Central Asian Foldbelt. The Nd model age, T(DM), of metamorphic rocks from the Ilikan Sequence is 2.6-3.2 Ga pointing to the likelihood that the lower boundary of their protolith formation probably does not exceed 2.6 Ga. The age of detrital zircons from metasedimentary rocks of the Ilikan Sequence is 2700-2900 Ma, which absolutely agrees with Sm-Nd isotopic-geochemical results. The U-Pb zircon age of metagabbro that intruded the rocks of the Ilikan Sequence and underwent high-temperature amphibolite metamophism with subsequent structural transformations is 2635 ± 4 Ma. The obtained results allow us to conclude that the age of the Ilikan Sequence is 2630-2700 Ma. All this gives grounds to state that the Dzhugdzhur-Stanovoi Superterrane in the Central Asian Foldbelt was formed due to amalgamation of non-Siberian terranes as is assumed for the Argun, Bureya, and Mamynskii terranes of the Amur Superterrane from the Central Asian Foldbelt. [ABSTRACT FROM AUTHOR]

Abstract: This paper discusses the exhumation history of Palaeoproterozoic high-grade units from the Lapland Granulite Belt (northern Finland) through a reappraisal of previous structural and metamorphic data and a new structural analysis. The Lapland Granulite Belt is located between two cratons (Inari Craton and South Lapland Craton). It is marked by a major thrusting event associated with the development of an inverse metamorphic gradient within the underlying Tanaelv and Karasjok Belts. The review of published metamorphic data combined with our new structural analysis suggests that the exhumation history of the Lapland Granulite Belt was accommodated by the development of coeval basal thrusting and early normal-sense shear-zones, and later by distributed erosion. We propose also that the early exhumation stages of the Lapland granulite unit were associated with heating of both the overlying Inari Craton and the underlying South Lapland Craton. The occurrence of coeval thrusts and normal-sense shear-zones combined with the important role of distributed erosion during the final exhumation stages suggest that this Palaeoproterozoic collisional belt may represent an intermediate stage between ultra-hot accretionary orogens involving weak lithospheres and modern orogens involving stiff lithospheres (mixed-hot orogen of ). Our analysis emphasizes that the transition between ancient-type orogens and modern-type ones was gradual in space and time, being firstly dependent on the thermal and rheological state of the sub-continental lithospheric mantle of the lithospheres involved in compression. [Copyright &y& Elsevier]

Abstract: This paper proposes a new method for 3D finite strain analysis. This method utilizes a Mohr circle construction combined with stereographic projection of the geometry of no finite longitudinal strain and with the strain ratio on the XZ-plane of the finite strain ellipsoid. The method is described using numerical examples and then it is tested by applying it to the deformed Deh Vazir conglomerate in the southwestern part of the Sanandaj-Sirjan HP-LT metamorphic belt, within the Zagros orogenic belt in Iran. The results of this method compare well with previous finite strain measurements using strain ratios on three principal planes of finite strain. Calculation of finite strain from strain ratios on the XY and YZ principal planes is advantageous when preparation of 3 perpendicular sections is difficult or impossible. [Copyright &y& Elsevier]

Abstract: This paper presents the results of a detailed and fully integrated pressure–temperature–time-deformation (P–T–t-D) study of the country rocks around Venetia Mine in the Central Zone of the Limpopo Belt, South Africa. Detailed structural mapping around Venetia Mine delineates four deformation events (D1–D4). Relict S1 comprises quartzofeldspathic bands in biotite gneiss and amphibolite. S2, defined by biotite in biotite schist, gneissic banding in biotite gneiss, long axes of quartzofeldspathic augen, and the long axes of amphibolite lenses/boudins, is axial planar to F2. F3 occurs predominantly at the contacts between biotite gneiss and biotite schist, forming open to closed, upright to inclined, E-W- to ENE-trending, shallowly plunging folds. D4, which was constrictional-prolate in nature, refolded S1, S2, F2 and F3. F4 folds and an L4 mineral lineation, defined predominantly by sillimanite in metapelitic schist, plunge moderately NE to NNE and overprint all previous fabrics. Poles to refolded S2 foliations show a characteristic great circle distribution. In turn, the pole to this great circle coincides with the orientation of L4. Such patterns are also found in the Avoca, Bellevue and Ha-Tshansi sheath folds in the Central Zone, albeit that the plunge of the lineations at Venetia are predominantly NE-wards, rather than SW-wards. The moderately NE- to NNE-plunging F4 sheath folds and L4 lineations accord with the NE-SW trend of sheath folds and associated mineral elongation lineations observed elsewhere in the Central Zone. However, PbSL dating of syntectonic garnets constrain the minimum and maximum age of D2 and D4 structures respectively to c. 2037–2040 +/− 22Ma. The metamorphism developed in metapelitic lithologies is characterized by peak amphibolite facies conditions of ∼6.5kbar and 680°C. Pseudosection modelling of growth zoning in garnet provides evidence of a prograde pressure and temperature increase from ∼5kbar at 600°C to ∼6–6.5kbar at 650–680°C, which is interpreted to be a consequence of tectonic thickening. Collectively, the integrated P–T–t-D data unequivocally demonstrates that the country rocks around Venetia experienced a structural–metamorphic event in the palaeoproterozoic. Coupled with published data we suggest a simple two-fold tectonic model, which involves the Central Zone as separate terrane docking with the Kaapvaal during the Neoarchean and later, during the Palaeoproterozoic this Central Zone-Kaapvaal amalgam collides with the Zimbabwe Craton. [Copyright &y& Elsevier]

Abstract: Gavilgarh-Tan Shear Zone (GTSZ) – a map-scale ductile shear zone occurring in the southern part of the Central Indian Tectonic Zone (CITZ), contains many important clues to the tectonics of this important Proterozoic mobile belt of central India, which is yet controversial and hotly debated. Data from structural mapping, microstructural study and kinematic analyses of the GTSZ have been presented in this paper which clearly implies that GTSZ is mainly represented by a wrench-dominated transpressional shear zone with sinistral shear sense. Analysis of lineation patterns shows that, while horizontal stretching dominated within the ductile shear zone, rocks on either side (north and south) of it stretched vertically, with a transition zone of simultaneous horizontal and vertical stretching in between these two domains. A general transpressional strain has thus been partitioned into wrench- and pure shear-dominated domains at large scale. Further strain partitioning also took place at the outcrop scale. Geochemistry of the granitoids occupying the shear zone and its surrounding area indicates continental collision set-up, which supports the structural model. On the basis of earlier proposed tectonic models, and limited geochronological data available, of the southern part of CITZ, it is suggested here that an oblique collision, and final suturing, between the northern (Bundelkhand Craton) and southern (Bastar Craton) terrains within the CITZ around ∼1100Ma, have been partly accommodated by partitioned transpression along GTSZ and its surrounding gneiss–granitoid terrain. More intensive geochronological constraint of the collision event from both northern and southern side are however lacking at present. [Copyright &y& Elsevier]

Abstract: Reconstructions of the Cambrian–Silurian tectonic evolution of eastern Gondwanaland, when the Australian Tasmanides and Antarctic Ross Orogen developed, rely on correlation between structural elements in SE Australia and Northern Victoria Land (NVL), Antarctica. A variety of published models exist but none completely solve the tectonic puzzle that is the Delamerian–Lachlan transition in the Tasmanides. This paper summarizes the understanding of Cambrian (Delamerian) to Silurian (Lachlan) geological evolution of the eastern Tasmanides, taking into account new deep seismic data that clarifies the geological connection between Victoria and Tasmania — the ‘Selwyn Block’ model. It evaluates previous attempts at correlation between NVL, Tasmania and Victoria, and presents a new scenario that encompasses the most robust correlations. Tasmania together with the Selwyn Block is reinterpreted as an exotic Proterozoic microcontinental block – ‘VanDieland’ – that collided into the east Gondwanaland margin south of western Victoria, and north of NVL in the Late Cambrian, perhaps terminating the Delamerian Orogeny in SE Australia. Subsequent north-east ‘tectonic escape’ of VanDieland in the Early Ordovician explains the present-day outboard position of Tasmania with respect to the rest of the Delamerian orogen, the origin of the hiatus that separates the Delamerian and Lachlan orogenic cycles in Australia, and how western Lachlan oceanic crust developed as a ‘trapped plate-segment’. The model establishes a new structural template for subsequent Lachlan Orogen development and Mesozoic Australia–Antarctica separation. [Copyright &y& Elsevier]

Abstract: In this paper we present a review of mineral systems in northern Xinjiang, NW China, focussing on the Tianshan, West and East Junggar and Altay orogenic belts, all of which are part of the greater Central Asian Orogenic Belt (CAOB). The CAOB is a complex collage of ancient microcontinents, island arcs, oceanic plateaux and oceanic plates, which were amalgamated and accreted in Early Palaeozoic to Early Permian times. The establishment of the CAOB collage was followed by strike-slip movements and affected by intraplate magmatism, linked to mantle plume activity, best exemplified by the 250 Ma Siberian Traps and the 280 Ma Tarim event. In northern Xinjiang, there are numerous and economically important mineral systems. In this contribution we describe a selection of representative mineral deposits, including subduction-related porphyry and epithermal deposits, volcanogenic massive sulphides and skarn systems. Shear zone-hosted Au lodes may have first formed as intrusion-related and subsequently re-worked during strike-slip deformation. Intraplate magmatism led to the emplacement of concentrically zoned (Alaskan-style) mafic–ultramafic intrusions, many of which host orthomagmatic sulphide deposits. A huge belt of pegmatites in the Altay orogen, locally hosts world-class rare metal deposits. Roll-front, sandstone-hosted U mineralisation completes the rich mineral endowment of the northern Xinjiang terranes. [Copyright &y& Elsevier]

The Thompson Nickel Belt marks the boundary between the Archean Superior Province and the Trans-Hudson Orogen in Canada. It comprises Archean gneisses, and Paleoproterozoic rocks with metasediments and metavolcanites (Ospwagan Group) and intrusions. The gneisses are frequently migmatitic and host numerous pegmatites. The western belt boundary is a fault contact with the Kisseynew Domain of the Reindeer Zone. In the south, the transition zone between the belt and the Kisseynew Domain comprises granitoids and a detrital sequence (Grass River Group), part of which grades into turbidites in the Kisseynew Domain. The eastern belt boundary is a diffuse zone where the Archean east-west (E-W) structural trend changes into the north-northeast (NNE) trend of the belt. This paper presents U-Pb ages for granitoids and 207Pb/206Pb detrital zircon ages from the Ospwagan and Grass River groups. Ages and a comparison of events in the belt and in the eastern Reindeer Zone have major implications. The change from stable platform deposits to syn-tectonic filling and emplacement of mafic intrusions in the Ospwagan Group are attributed to the convergence between the Reindeer Zone and the Superior Province at 1891-1885 Ma. At ca. 1850 Ma, continuing convergence led to drowning of marginal basins of the Superior craton and to the development of a transpressive regime in the belt, the onset of which could be as old as ca. 1885 Ma. Metamorphic ages of 1818-1785 record closure of the Kisseynew basin and crustal thickening. Collision of the new continental block with the Superior Province was accommodated by transpression until 1750-1720 Ma. La ceinture de Thompson est située entre le Craton archéen du Supérieur et l'orogène paléoprotérozoïque du Trans-Hudson, au Canada. Elle comprend des gneiss archéens souvent migmatitiques, et des roches paléoprotéroïques, métasédiments et métavolcanites (Groupe Ospwagan), et intrusions. A l'ouest, une zone de faille marque le contact entre la ceinture et le domaine Kisseynew de la Zone de Reindeer. Vers le sud, cette zone de transition entre la ceinture et le domaine Kisseynew comprends des granitoïdes et une séquence détritique (Groupe Grass River), qui passe graduellement aux turbidites du domaine Kisseynew. Sur la bordure orientale de la ceinture, le grain structural E-W du Craton archéen se réoriente dans le grain NNE de la ceinture. Cet article présente des âges U-Pb pour différents granitoïdes et des âges 207Pb/206Pb pour les zircons détritiques des groupes Ospwagan et Grass River. Les âges et une comparaison des événements affectant la ceinture et l'est de la zone Reindeer ont des implications importantes. Dans le groupe Ospwagan, le passage de dépôts de type plate-forme à des dépôts syn-tectoniques, et l'intrusion de roches basiques, sont attribuées à la convergence entre la zone Reindeer et le Craton du Supérieur vers 1891-1885 Ma. Vers 1850 Ma, la convergence conduit à l'enfouissement des bassins de la marge du Craton et à un régime transpressif pouvant avoir débuté dès ca. 1885 Ma. La fermeture du bassin de Kisseynew et l'épaississement crustal sont enregistrés par des âges de métamorphisme entre 1818 et 1785 Ma. Le régime transpressif se poursuit jusqu'à ca. 1750-1720 Ma. [ABSTRACT FROM AUTHOR]

The development of metamorphic core complexes (MCC) corresponds to a mode of lithospheric continental stretching that follows collision. In most of the models that explain the formation of the MCC, high thermal gradients are necessary to weaken the lower crust and to induce its ascent. Such models fail to explain the exhumation of high pressure-low temperature metamorphic rocks in metamorphic core complex structures as observed in the Cycladic Blueschists in the Aegean domain. Besides, account for the lithological crustal stratification induced from collision has never been tested. In this paper, we use fully coupled thermomechanical modelling to investigate the impact of structural heritage and initial thermal gradient on the behaviour of the post-orogenic continental lithosphere. The models are designed and validated by petrological, structural and time data from the Cyclades. As a result, high thermal gradients (Moho temperature higher than 800°C) are neither necessary nor always sufficient to induce the development of a metamorphic core complex. At the contrary, the rheological layering of the crust inherited from collision is a first-order parameter controlling the development of extensional structures in post-orogenic settings. 'Cold' MCC can develop if the crust is made of a strong nappe thrust on top of weaker metamorphic cover and basement units, as observed in the Cyclades. [ABSTRACT FROM AUTHOR]

The Yunnan-Tibet Railway, currently under construction, crosses five altered rock zones in the Sanjiang orogenic belt, southwestern China. They are mainly montmorillonitized rock zones formed by hydrothermal alteration. Based on field investigation and laboratory tests, this paper presents the geological characteristics and engineering properties of the altered rocks encountered during the construction of the railway. Being characterized by a high montmorillonite content, high degree of alteration, high physico-chemical activity and high swelling potential, these rocks always lead to engineering geological problems. The concept of 'alteration coefficient' is put forward; the greater the alteration coefficient, the higher the alteration degree and swelling potential. Countermeasures are proposed to tackle the engineering problems during tunnel construction caused by the altered rock. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a structural and stratigraphic analysis of the foreland-fold-belt of the Eastern Venezuelan Basin and the main conclusions about shale tectonic mechanisms in the area. The deformation of the foreland-fold-belt has been investigated analyzing the growth strata architecture preserved on the structure fold limbs. Three contractional episodes are proposed for the Eastern Venezuelan Basin: 1) Oligocene to middle Miocene, 2) late Miocene to Pliocene and 3) Pleistocene. The first episode produced contractional listric faults inside the shale and long displacement blind thrusts in the underlying Cretaceous units. The second episode produced the deformation of the Cenozoic strata into overlapping east-west-trending, convex northward anticlines that covers more than 200 kilometers in length and 40 kilometers wide, break-through normal faults product of a high sedimentary load that overcomes contraction and the formation of short-displacement blind thrusts in the underlying Cretaceous units. The last episode is related to an oblique compression and the formation of high angle extensional faults with dextral movement and NW-SE strike. The role of the shale tectonics in the evolution implies that shale deforms in two stages: 1) folding and 2) normal faulting of the crest of the anticline (Break through normal faulting). Folding controlled the sediment distribution during most of the Neogene strata, while the normal faulting of the anticlines represent basin potential for hydrocarbon. The best potential hydrocarbon plays in the basin are related to oblique-collision restricted basins and controlled by break-through normal faults and the presence of NW-SE strike faults that connect the HC source with the reservoirs. Results from this research imply that the role of sedimentation is fundamental for the overburden sand distribution and tectonic constrain of the folds. [ABSTRACT FROM AUTHOR]

The Beishan orogenic collage is located in the southernmost part of the Altaids, and connects the Southern Tien Shan suture to the west with the Solonker suture to the east. The orogen was previously regarded as early Paleozoic in age in contrast to the surrounding southern Altaid collages, which are Late Paleozoic or even Early Mesozoic. This paper reviews the tectonic units of the Beishan orogen, which along a north-south traverse consists of several arcs and ophiolitic mélanges. These tectonic units were thrust imbricated and overprinted by strike-slip faulting during Permian-Triassic times, and the youngest strata involved in the deformation are Permian. Stitching plutons are Late Permian in age. Peaks of magmatic-metamorphictectonic activity, and paleomagnetic and paleogeographic data indicate that the Beishan orogenic collage evolved by development of several, Early to Mid-Paleozoic arcs in different parts of the Paleoasian Ocean. The Late Paleozoic collage is characterized by three active continental margins or island arcs that are separated by two ophiolitic mélanges. The northernmost active margin is represented by the Queershan arc, which may have lasted until the Permian. The Shibanshan unit is the southernmost, subduction-related continental arc along the northern margin of the Dunhuang block. In the Late Carboniferous to Permian the eastern end (promontory) of the Tarim Craton probably collided with the Chinese eastern Tien Shan arc, forming a new active continental margin, which interacted with the Beishan Late Paleozoic archipelago, generating a complicated subduction-accretionary orogen; this is suggested to be one of the last phases in the development of the long-lived Altaid accretionary orogenesis. The new model for this orogen bridges the gap between the western and eastern ends of the southern Altaids. The modern Timor-Australia collision zone with its many surrounding arcs is an appropriate analog for the Altaids in the Late Paleozoic. [ABSTRACT FROM AUTHOR]

Methods of rock mechanics and mechanical testing are a suitable supplement to tectonic analysis and structural reconstruction in areas where structures are not clearly visible. Rock mechanics enhances tectonic research of young non-deep eroded orogenic belts, where past lithostatic stress acquired quite similar values to present-day ones. This paper focusses on cross-section balancing in frontal parts of nappes of the Outer Western Carpathians. [ABSTRACT FROM AUTHOR]

Abstract: The NNW-trending tectonic grain of the eastern Yilgarn Craton (EYC) was established as a result of predominantly ENE–WSW directed extension (D1 and D3) and E(ENE)–W(WSW) (D2, D4) to NE–SW directed (D5) contraction. The result has been a succession of NNW-striking temporally discrete fabric elements, which can be difficult to interpret reliably at any single location. Despite this, many past workers interpreted the NNW-striking fabric as the result of only one regional contractional event, and used it as a marker for correlating structural events across the region. In order to unravel the complexity, this paper presents a new sixfold (D1–D6) deformation nomenclature based on >10,000 new mesoscale structural observations, including their kinematic analysis and cross-cutting relationships. These mesoscale data were referenced with regional 3D map patterns, stratigraphic-magmatic-metallogenic considerations, and deep seismic reflection images. This integrated geodynamic-architectural approach is applicable to solving structural-event histories in other polydeformed terrains. Gold mineralisation occurred during the first five events, but was particularly concentrated from D3 onwards. The D3 event marked the most profound change in the tectonic evolution of the EYC, with changes in greenstones, granites and tectonic mode (lithospheric extension and core complexes), with the first significant gold deposited within extensional shear zones that dissect the crust. Later contraction (D4) was imposed at a high angle to the previously established anisotropic architecture. The outcome was the creation of a new dynamic permeability framework, which resulted in gold mineralisation during NNW-striking sinistral strike-slip faulting and associated thrusting. A further stress switch (D5) further modified the architecture resulting in N- to NNE-striking dextral strike-slip faulting, and the final period of gold mineralisation, before late-stage extension (D6). [Copyright &y& Elsevier]

This paper presents detailed SHRIMP zircon U–Pb chronology, mineral chemistry, major and trace element, and Sr–Nd–Hf isotope geochemistry of the Datong pluton and its quenched enclaves from the western Kunlun orogen, northwest China, in an attempt to achieve a better understanding on the origin of diverse arc magmas. The Datong host granitoids are intermediate to acid in composition (SiO = 57.5 ~ 73.1 wt.%), and exhibit high-K calc-alkaline to shoshonitic affinities. The quenched enclaves are silica-rich ultrapotassic rocks. Detailed SHRIMP zircon U–Pb dating indicates that the Datong pluton was emplaced in Ordovician time (473.4–447.7 Ma), which places the Datong pluton in an active continental margin setting, rather than a syn-collision setting of Early Silurian age. The Datong host granitoids were derived by partial melting of subducted sediments, with the subsequent melt interacting with the overlying mantle wedge during its ascent. Partial melting of the veined mantle wedge hybridized by sediment-derived melts generated the silica-rich ultrapotassic magma, which was injected into the Datong granitoid magma chamber and quenched, resulting in enclaves hosted by granitoids. This contribution provides evidence that arc magmas can be derived directly by partial melting of subducted sediments, which is helpful to further understand the origin of diverse arc magmas. [ABSTRACT FROM AUTHOR]

Abstract: The paper discusses the spatiotemporal and genetic relationships of hydrothermal Co mineralization in the Altai–Sayan orogen with mafic, alkaline mafic, and granitoid magmatism on the basis of isotopic, geochemical, and geochronological investigations. Four stages of Co mineralization have been distinguished for this region: Early Devonian (D1), Late Devonian–Early Carboniferous (D3–C1), Permo-Triassic (P2–T), and Early Cretaceous (K1). They correspond to periods of large-scale mafic magmatism. Isotopic (Pb, Sr, He) and geochemical studies have shown that Co mineralization is genetically related to mafic and granitoid magmatism. Also, these studies have confirmed that Co deposits are formed with the participation of mantle fluids and are related to chambers of mafic and alkaline mafic melts. Besides, it has been found that ore originated both from magmatic sources and host rocks. A pulsed facies endogenic zonation has been established for Co deposits, Co-bearing ore clusters, and zones with high-temperature Co–As and low-temperature Ni–Co–As mineralization. It has been first established that ores at hydrothermal Co deposits are rich in Pt and Pd. [Copyright &y& Elsevier]

This paper presents the results of two-dimensional (2-D) numerical modeling that reconstructs the thermal evolution and the flow of fluid in a collisional overthrust setting with syn-metamorphic magmatism. The goal of the study is to explore the relationships between regional metamorphism and magmatic activity. Our results demonstrate the strong effects that syn-metamorphic magmatism exerts on the thermal structure of the thickened crust. Magmatic intrusions in the form of repetitive sills of mafic or intermediate-felsic compositions introduced at different levels in the thickened crust section may produce Buchan and Barrovian-type metamorphic sequences, as well as rocks in the granulite facies of metamorphism. The peak temperatures in crustal rocks around intrusions are increased by more than 100 °C from their values for the non-magmatic case; the timescales of peak temperature attainment in rocks at short distances from the intrusions are only 1 Myr or less. The peak temperature attainment is synchronous within the different metamorphic zones over the depth range of up to 20 km. These features differ strongly from those in the overthrust model without magmatism, characterized by broad thermal peaks spanning 5 to 10 Myr and non-synchronous attainment of peak conditions for rocks at different depths, with ∼5 Myr delay for every 10 km of depth (exhumation rate = 1 mm yr-1). The specific peak metamorphic mineral assemblages that develop in model rock of metapelitic composition as a result of magmatism are largely controlled by the depth of magma emplacement: intrusion into the lower plate of the overthrust zone leads to the development of amphibolite facies mineral assemblages in the staurolite, kyanite and garnet-biotite (without chlorite) zones, as well as considerable volumes of granulite facies rocks. Emplacement of intrusions at mid crustal depths of 15 to 35 km produces minerals of low-pressure/high-temperature (LP/HT) metamorphic zones, such as cordierite-biotite-K-feldspar, in addition to staurolite, kyanite, and sillimanite zones. When mid-crustal magmatism is initiated at earlier times in the model thrust exhumation history, the LP/HT metamorphic zones may not be preserved in the crustal section due to surface erosion. All of the models predict extremely steep, approximately isobaric Metamorphic Field Temperature Gradients (MFTGs) around the edges of the intrusions and along the contacts of thick isolated sills. In some cases, the transition from chlorite to sillimanite zones of metamorphism at the side of the magmatic region may take place in less than 1 km. The magmatism-related MFTGs stand in contrast to the regional metamorphic gradients produced by crustal thickening that form at the flanks of the overthrust zone distal to the magmas. Here, the transition from the chlorite zone to high-grade mineral assemblages takes place over 20 to 40 km, and the pressure of peak temperature attainment increases by as much as 0.3 GPa from low to high grade. [ABSTRACT FROM AUTHOR]

We investigate the material fluxes in space and time as a result of exhumation and erosion processes at the ongoing Yakutat-North American collision in southeast Alaska. Many thermochronologic studies using a variety of sampling strategies are challenged by the widespread ice cover that limit field observations and accessibility. This paper reviews new and published low-temperature thermochronological data from southeast Alaska to give a comprehensive interpretation of the exhumation patterns through time and how they are influenced by surface processes and climate change. We find that the southeastern margin of Alaska was exhumed and eroded long before the late Miocene-Pliocene Yakutat collision, but since the beginning of the subduction of the Yakutat lithosphere in the Oligocene/early Miocene. Today there is a distinct pattern of exhumation in southeast Alaska with a localized very rapid and deep-seated exhumation at the Yakutat plate corner (St. Elias syntaxis), where strike slip motion changes to convergence. Exhumation is also rapid, but less deep along the dextral Fairweather fault, and in the evolving fold and thrust belt. We present a re-interpretation of the exhumation pattern in the fold and thrust belt and suggest that mass transport by exhumation is parallel to the observed active thrust faults and oblique to the suture zone and orogenic strike. The locus of most rapid exhumation migrated from northwest to southeast with Recent exhumation occurring near the St. Elias syntaxis. Exhumation of the Chugach terrane rocks is still active, however to a lesser degree than on the south side of the orogen where precipitation rates are much higher. The Wrangellia terrane to the north has experienced little exhumation and has essentially formed the backstop for terrane accretion in southeast Alaska since the Early Cretaceous. Apatite U-Th/He ages give the first evidence that rocks of the Wrangell Range have only been recently uplifted and eroded as a consequence of the continuing Yakutat collision. In general the thermochronology in southeast Alaska reveals that climate variations across the region as well as changes through time have a limited influence on the pattern of erosion and that the location of deep exhumation is primarily influenced by tectonic processes. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the mineralogical effects of hydrothermal alteration at depth in fractures in granite. A fracture accompanied by an alteration halo and filled with clay was found at a depth of 200m in a drill core through Toki granite, Gifu, central Japan. Microscopic observation, XRD, XRF, EPMA and SXAM investigations revealed that the microcrystalline clays consist of illite, quartz and pyrite and that the halo round the fracture can be subdivided into a phyllic zone adjacent to the fracture, surrounded by a propylitic zone in which Fe-phyllosilicates are present, and a distinctive outer alteration front characterized by plagioclase breakdown. The processes that result in these changes took place in three successive stages: 1) partial dissolution of plagioclase with partial chloritization of biotite; 2) biotite dissolution and precipitation of Fe-phyllosilicate in the dissolution pores; 3) dissolution of K-feldspar and Fe-phyllosilicate, and illite precipitation associated with development of microcracks. These hydrothermal alterations of the granite proceed mainly by a dissolution–precipitation process resulting from the infiltration of hydrothermal fluid along microcracks. Such infiltration causes locally high mobility of Al and increases the ratio of fluid to rock in the alteration halo. These results contribute to an understanding of how granitic rock becomes altered in orogenic fields such as the Japanese island arc. [Copyright &y& Elsevier]

This paper reports sensitive high resolution ion micro-probe U-Pb zircon ages for the 'Huoqiu Group' and granitoids of the Early Precambrian basement in the Huoqiu area, southeastern margin of the North China Craton. The 'Huoqiu Group' is similar in rock association and metamorphism to the khondalite series, apart from it containing considerable amounts of banded iron formation. All detrital zircons from the 'Huoqiu Group' meta-sedimentary rocks are 3.0 Ga and 2.75 Ga, without any 2.5 Ga and younger ones, as is commonly found in Paleoproterozoic khondalite series in other areas of the North China Craton. In the Huoqiu area, 2.75 Ga and 2.56 Ga granitoids have also been identified. This basement assemblage underwent strong metamorphism during the late Paleoproterozoic (∼ 1.84 Ga) tectonothermal event that is widely developed in the North China Craton. Thus the formation time of the 'Huoqiu Group' can be constrained between 2.75 and 1.84 Ga in terms of detrital and metamorphic zircon ages. It is considered, combined with regional data, that there may be a Paleoproterozoic collision orogen extending in a NWW-SEE direction to the southern margin of the North China Craton. [ABSTRACT FROM AUTHOR]

Abstract: Until now, no satisfactory geodynamic model has been delivered concerning the three main West African orogens: Panafrican 1 (Bassaride belt), Panafrican 2 (Rokelide belt) and Hercynian (Mauritanide belt). However, since the last synthetic paper (), new geological, geophysical and geochronological data, from the Moroccan Sahara to Sierra Leone, allow us to propose a new geodynamical model. It includes the two Panafrican events in a single model very similar to the present western Pacific margin. An old “West African Neoproterozoic ocean” (WANO) was limited by a set of island arcs separated from the West African craton by a series of “back arc basins”. The closure of this first round of back arc basins around 650 Ma led to the Bassaride belt (Panafrican 1). Then the WANO was subducting underneath the island arcs (between 650 and 550 Ma) meanwhile a new generation of “back arc basins” opened to the east between the arcs and the craton margin. The closure of the WANO and associated island arcs and back arc basins (550 to 500 Ma) led to the Rokelide belt (Panafrican 2). The Hercynian structures involving a Palaeozoic cover (made with continental material) associated to a “greeenschist facies” metamorphism is ascribed to an intracontinental belt. [Copyright &y& Elsevier]

Neoproterozoic-lower Palaeozoic successions in the Brasiliano fold belts are described and a brief synthesis of these terranes is presented in order to erect a tectonic framework for this region. Tectonic events that occurred around the Rio de La Plata craton were diachronous and reflected successive stages of the Brasiliano orogenic cycle. They took place in mobile belts that constituted part of the Gondwana supercontinent. The most thoroughly investigated Neoproterozoic sections are located in the eastern and southeastern regions of Uruguay. The Dom Feliciano Belt shows a tectonic evolution from back-arc to foreland basin characterized by fold-and-thrust, thick-skinned belts developed during the Brasiliano/Pan-African orogenic cycle. The most conspicuous features were late-tectonic high-K calc-alkaline granitoids, HT-LP metamorphism, significant displacements along shear zones, and post-tectonic granitoids. The final stage was characterized by post-collisional basins (molassic sequences) and extensional magmatism related to a phase of crustal stretching. Several lithotectonic units are present as basement inliers in the Dom Feliciano Belt: these include a low-to-medium metamorphic grade sequence (the Zanja del Tigre Formation), granitoids and gneisses (the Campanero Unit), high-grade basement of the Cerro Olivo Complex (Palaeoproterozoic or Neoproterozoic), and a low-metamorphic grade orogenic belt (the Rocha Formation). This paper provides a simplified tectonic map of eastern Uruguay, which we use to describe tectonic evolution from Precambrian to early Palaeozoic time. [ABSTRACT FROM AUTHOR]

Geological studies indicate that the southeastern Sanandaj–Sirjan Zone, located in the southeastern Zagros Orogenic Belt, is subdivided transversally into the Esfahan–Sirjan Block with typical Central Iranian stratigraphic features and the Shahrekord–Dehsard Terrane consisting of Paleozoic and Lower Mesozoic metamorphic rocks. The Main Deep Fault (Abadeh Fault) is a major lithospheric fault separating the two parts. The purpose of this paper is to clarify the role of the southeastern Sanandaj–Sirjan Zone in the tectonic evolution of the southeastern Zagros Orogenic Belt on the basis of geological evidence. The new model implies that Neo-Tethys 1 came into being when the Central Iran Microcontinent split from the northeastern margin of Gondwana during the Late Carboniferous to Early Permian. During the Late Triassic a new spreading ridge, Neo-Tethys 2, was created to separate the Shahrekord–Dehsard Terrane from Afro–Arabian Plate. The Zagros sedimentary basin was formed on a continental passive margin, southwest of Neo-Tethys 2. The two ophiolitic belts of Naien–Shahrebabak–Baft and Neyriz were developed to the northeast of Neo-Tethys 1 and southwest of Neo-Tethys 2 respectively, related to the sinking of the lithosphere of the Neo-Tethys 1 in the Late Cretaceous. It can be concluded that deposition of the Paleocene conglomerate on the Central Iran Microcontinent and Pliocene conglomerate in the Zagros Sedimentary Basin is directly linked to the uplift generated by collision. [ABSTRACT FROM AUTHOR]

The Montagna dei Fiori has received attention by geologists through the past decades because of both its Jurassic stratigraphy and its complex present-day structure. The latter is the result of multiple phases of deformation, from the Early Jurassic, during the rift phase, which led to the opening of the Tethyan Ocean, to compression in Neogene, linked with the evolution of the Apennines fold and thrust belt. In this paper, we present a new stratigraphic interpretation of the Jurassic palaeogeography, based on a new geological mapping project in the area. Using this new stratigraphy, we constructed two forward models of the Montagna dei Fiori fault-related fold, using a combination of different kinematic models. We followed two different approaches: the first model was constructed manually starting from the construction of a balanced cross section and its restoration, followed by a definition of the main steps for the forward model; the second was constructed using 2DMove (Midland Valley), starting from a simplified version of the same stratigraphy and using the same main steps imposed in the other section. [ABSTRACT FROM AUTHOR]

The Prague Synform (Ordovician to Devonian) was folded and thrusted during the Variscan orogeny. This paper is focused on one of these thrusts: the Ockov Fault. The creation of a stratigraphic separation diagram and detailed study of new tunnel exposures has brought about the recognition of the eastern prolongation of the fault, as well as its flat-ramp-flat geometry and thrusting nature. [ABSTRACT FROM AUTHOR]