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Kinematic significance and time scales of geodynamic processes forming the Altai Orogenic Belt are addressed through structural and petrological analysis combined with zircon and monazite geochronology. The study area is composed of orogenic lower crust represented by a Devonian migmatite‐magmatite complex and orogenic middle and upper crust formed by an amphibolite‐facies Ordovician sedimentary sequence and a weakly to unmetamorphosed Devonian volcano‐sedimentary cover, respectively. The orogenic lower and middle crust were first affected by moderate thickening, which formed subhorizontal Barrovian metamorphic schistosity. This fabric was reworked by deep crustal melting and intrusion of granite sheets during horizontal extension at 400–380 Ma. Soon after, this horizontal fabric was affected by NW‐SE shortening generating crustal‐scale upright folding associated with subvertical flow of still partially molten orogenic lower crust. During this event, the orogenic lower and middle crust were tightly juxtaposed with upper crustal sedimentary rocks. The last event was related with a NE‐SW oriented convergence resulting in large‐scale folding and megafold interference pattern in the Permian at 280–273 Ma. Combined with existing regional data, our results allow proposing a Devonian tectonic switching from compression to extension and back to compression, as a response to variations of subduction dynamics between slab advance and retreat in a Pacific‐type suprasubduction system. The Permian folding was associated with the progressive northward exhumation of thermally softened crust. This tectonic evolution is in response to the indentation of the rigid Junggar arc domain into the weak Altai wedge. The Chinese Altai was affected by pre‐Devonian crustal thickening, Mid‐Devonian (400‐380 Ma) extension, and Late Devonian NW‐SE shorteningThe Devonian edifice was affected by NW‐SE zones of high‐temperature deformation and upright folding in the Permian at 280‐273 MaDevonian events reflect suprasubduction tectonic switching, while Permian folding indicates the Junggar‐Chinese Altai collision

In continental crust, rapid melt flow through macroscopic conduits is usually envisaged as the most efficient form of melt transport. In contrast, there is growing evidence that in hot continental crust, grain‐scale to meso‐scale porous melt flow may operate over long distances and over millions of years. Here, we investigate the dynamics of such porous melt flow by means of two‐dimensional thermo‐mechanical numerical models using the code ASPECT. Our models are crustal‐scale and describe the network of pores through which the melt flows by permeability that depends on the spacing of the pores. Our results suggest that assuming realistic material properties, melt can slowly migrate in the hot and thick continental crust through pores with a characteristic spacing of 1 mm or larger. Despite its low velocity (millimeters to centimeters per year), over millions of years, such flow can create large partially molten zones in the middle‐lower crust and significantly affect its thermal state, deformation, and composition. We examined the role of the permeability, melt and solid viscosities, the slope of the melting curve and temperature conditions. We obtained contrasting styles of melt distribution, melt flow, and solid deformation, which can be categorized as melt‐enhanced convection, growth of partially molten diapirs and melt percolation in porosity waves. Our numerical experiments further indicate that grain‐scale porous flow is more likely in rocks where the melt productivity increases slowly with temperature, such as in metaigneous rocks. Continental crust contains a significant proportion of rocks that can melt relatively easily. Geophysical methods that measure, for example, seismic velocities or electric conductivity revealed large partially molten regions in the continental crust. In addition, solidified melt pathways (veins, dykes) are often observed in rocks that were formerly in hot continental interiors. Usually, melt flow through macroscopic pathways is assumed to be the most efficient type of melt transport. However, several geological studies have shown that melt may flow through much finer (microscopic) pores, which form a network along boundaries of rock grains. The question arises, how efficient this microscopic melt flow is, and how it affects the properties of the continents. We address this issue using numerical models. According to our models, microscopic melt flow is very slow—melt moves millimeters to centimeters per year. Despite its low velocity, over millions of years, it forms large partially molten zones, significantly increases the temperature in the crust, changes its composition and softens it. The style of this process varies notably depending on the rock properties and temperature conditions. For example, in some models, kilometer‐sized melt batches move through nearly immobile rock, while in others, melt and rock both move together as a stirred mush. Numerical thermo‐mechanical models simulate porous melt flow through hot felsic continental crustMelt can propagate through pores with the spacing of 1 mm or larger with a velocity of millimeters to centimeters per year and form large partially molten zonesStyle of melt flow and solid deformation vary between melt‐enhanced convection, diapirism, and porosity waves depending on model parameters Numerical thermo‐mechanical models simulate porous melt flow through hot felsic continental crust Melt can propagate through pores with the spacing of 1 mm or larger with a velocity of millimeters to centimeters per year and form large partially molten zones Style of melt flow and solid deformation vary between melt‐enhanced convection, diapirism, and porosity waves depending on model parameters

During continental collision, a part of the lower‐plate material can be subducted, emplaced at the base of the upper plate, and eventually incorporated into its crust. This mechanism of continental‐crust transformation is called relamination, and it has been invoked to explain occurrences of high‐pressure felsic rocks in different structural positions of several orogenic systems. In the present study we reproduced relamination during continental collision in a thermomechanical numerical model. We performed a parametric study and distinguished three main types of evolution regarding the fate of the subducted continental crust: (i) return along the plate interface in a subduction channel or wedge, (ii) flow at the bottom of the upper‐plate lithosphere and subsequent translithospheric exhumation near the arc or in the back‐arc region (“sublithospheric relamination”), and (iii) nearly horizontal flow directly into the upper‐plate crust (“intracrustal relamination”). Sublithospheric relamination is preferred for relatively quick convergence of thin continental plates. An important factor for the development of sublithospheric relamination is melting of the subducted material, which weakens the lithosphere and opens a path for the exhumation of the relaminant. In contrast, a thick and strong overriding plate typically leads to exhumation near the plate interface. If the overriding plate is too thin or weak, intracrustal relamination occurs. We show that each of these evolution types has its counterpart in nature: (i) the Alps and the Caledonides, (ii) the Himalayan‐Tibetan system and the European Variscides, and (iii) pre‐Cambrian ultrahot orogens. Presented numerical models of continental subduction and collision reproduce the relamination process for a range of conditionsRelamination may occur directly into the crust for very weak overriding plates or through the overriding plate lithosphereDeep subduction and relamination through the overriding plate lithosphere is typical for quickly colliding young continents

Neoproterozoic to early Paleozoic accretionary processes of the Central Asian Orogenic Belt have been evaluated so far mainly using the geology of ophiolites and/or magmatic arcs. Thus, the knowledge of the nature and evolution of associated sedimentary prisms remains fragmentary. We carried out an integrated geological, geochemical, and zircon U‐Pb geochronological study on a giant Ordovician metasedimentary succession of the Mongolian Altai Mountains. This succession is characterized by dominant terrigenous components mixed with volcanogenic material. It is chemically immature, compositionally analogous to graywacke, and marked by significant input of felsic to intermediate arc components, pointing to an active continental margin depositional setting. Detrital zircon U‐Pb ages suggest a source dominated by products of early Paleozoic magmatism prevailing during the Cambrian‐Ordovician and culminating at circa 500 Ma. We propose that the Ordovician succession forms an “Altai sedimentary wedge,” the evolution of which can be linked to the geodynamics of the margins of the Mongolian Precambrian Zavhan‐Baydrag blocks. This involved subduction reversal from southward subduction of a passive continental margin (Early Cambrian) to the development of the “Ikh‐Mongol Magmatic Arc System” and the giant Altai sedimentary wedge above a north dipping subduction zone (Late Cambrian‐Ordovician). Such a dynamic process resembles the tectonic evolution of the peri‐Pacific accretionary Terra Australis Orogen. A new model reconciling the Baikalian metamorphic belt along the southern Siberian Craton with peri‐Pacific Altai accretionary systems fringing the Mongolian microcontinents is proposed to explain the Cambro‐Ordovician geodynamic evolution of the Mongolian collage system. The Mongolian Altai represents an Ordovician accretionary wedge riming the active margins of the northerly Precambrian blocksWestern margins of Mongolian Precambrian blocks switched from an Early Cambrian passive margin to a Late Cambrian‐Ordovician active oneThe Mongolian collage system and southern Siberia probably evolved from a peri‐Pacific subduction system in Cambro‐Ordovician

Granitoid magmatism and its role in differentiation and stabilization of the Paleozoic accretionary wedge in the Chinese Altai are evaluated in this study. Voluminous Silurian-Devonian granitoids intruded a greywacke-dominated Ordovician sedimentary succession (the Habahe Group) of the accretionary wedge. The close temporal and spatial relationship between the regional anatexis and the formation of granitoids, as well as their geochemical similarities including rather unevolved Nd isotopic signatures and the strong enrichment of large-ion lithophile elements relative to many of the high field strength elements, may indicate that the granitoids are product of partial melting of the accretionary wedge rocks. Whole-rock geochemistry and pseudosection modeling show that regional anatexis of fertile sediments could have produced a large amount of melts compositionally similar to the granitoids. Such process could have left a high-density garnet- and/or garnet-pyroxene granulite residue in the deep crust, which can be the major reason for the gravity high over the Chinese Altai. Our results show that melting and crustal differentiation can transform accretionary wedge sediments into vertically stratified and stable continental crust. This may be a key mechanism contributing to the peripheral continental growth worldwide. Ordovician accretionary wedge sediments in the Chinese Altai may be a viable source for Pacific-type Silurian-Devonian granitoidsMelting of accretionary wedge left behind granulitic residue that can explain gravity high over the Chinese AltaiMelting and crustal differentiation of the accretionary wedge sediments can transform oceanic material into stabilized continent

A characteristic association of crustal and mantle rocks is commonly used to decipher processes at the mantle- crust interface of HP-UHP collisional orogenic systems. Also, in the Variscan orogenic root of the Bohemian Massif (the Moldanubian Zone), high-pressure felsic granulites are often accompanied by spinel or garnet peridotites. This association was investigated using petrography, zircon geochronology and whole-rock geochemical data from the Náměšť Granulite Massif. The geochemical signature of the granulite is the same as for other Moldanubian occurrences, suggesting nearly isochemically metamorphosed felsic metaigneous rocks of Saxothuringian provenance. SHRIMP zircon dating yielded two main age maxima, at 395.2 ± 4.4 and 337.2 ± 1.7 Ma, reflecting an Early Devonian protolith and Visean HP metamorphism. As shown by Sr-Nd isotopic data, the variably refertilized harzburgite or depleted lherzolite was variously contaminated by mature crustal material resembling the studied granulites. To account for the origin of these HT-HP rock associations we suggest a new geotectonic model. An eastward continental subduction of Early Palaeozoic felsic metaigneous material of Saxothuringian origin was followed by its relamination at the bottom of the autochthonous lower crust. Ascending felsic granulites derived from the relaminated lower plate material sampled refertilized harzburgites originally formed in a backarc. The complete assemblage was subsequently exhumed, forming large, diapir-like bodies. [ABSTRACT FROM AUTHOR]

The Mongolian Altai Zone of the Central Asian Orogenic Belt has been traditionally interpreted as a mosaic of Paleozoic magmatic arcs, back‐arcs, and Precambrian continental terranes. In order to define its architecture and its tectonic evolution, three domains previously interpreted as terranes were investigated. The findings show that the Northern and Central domains are formed by a metamorphic sequence characterized by Barrovian S1 fabric transposed by recumbent folds and dominant sub‐horizontal amphibolite facies S2 schistosity. The latter is associated with the intrusions of late Devonian syntectonic granite sheets and anatexis in the south. The Southern domain is formed by early Permian migmatites and anatectic granites separated from the metamorphic envelope by amphibolite to green‐schist facies D3 shear zone cross‐cutting S2 fabrics. All domains have been reworked by E‐W upright folds associated with axial‐planar greenschist facies cleavage, reflecting the final mid‐Permian to Triassic D4 shortening. Lithological, geochemical, and U‐Pb zircon analyses of metasediments of all domains indicate that they are formed by Ordovician mature quartzite derived from Precambrian basement intruded by Cambrian‐Ordovician continental arc and Silurian immature graywacke which originated through erosion of an oceanic arc. Altogether, the whole sequence represents a fore‐arc basin in front of a migrating arc affected by thickening and late Devonian extension. The Southern domain is interpreted as an early Permian core complex amplified by mid‐Permian to Triassic compression. The apparent “terrane” architecture of the Mongol Altai Zone originated due to Devonian and Permian heterogeneous reworking of a giant Ordovician to Silurian fore‐arc basin. The Mongolian Altai Zone is an Ordovician to Silurian fore‐arc basin affected by Barrovian prograde metamorphismLate Devonian extension resulted in intrusion of sub‐horizontal, syntectonic granite sheets and partial melting in deep crustal levelsEarly Permian extension resulted in the formation of metamorphic core complex later amplified by regional mid‐Permian to Triassic compression The Mongolian Altai Zone is an Ordovician to Silurian fore‐arc basin affected by Barrovian prograde metamorphism Late Devonian extension resulted in intrusion of sub‐horizontal, syntectonic granite sheets and partial melting in deep crustal levels Early Permian extension resulted in the formation of metamorphic core complex later amplified by regional mid‐Permian to Triassic compression

In order to portray the main differences and similarities between the Northeastern Variscan segments (French Massif Central (FMC), Vosges, Black Forest and Bohemian Massif (BM)), we review their crustal-scale architectures, the specific rock associations and lithotectonic sequences, as well as the ages of the main magmatic and metamorphic events. This review demonstrates significant differences between the ‘Moldanubian’ domains in the BM and the FMC. On this basis we propose distinguishing between the Eastern and Western Moldanubian zones, while the Vosges/Black Forest Mountains are an intermediate section between the BM and the FMC. The observed differences are the result of, first, the presence in the French segment of an early large-scale accretionary system prior to the main Variscan collision and, second, the duration of Saxothuringian/Armorican subduction, which generated long-lived magmatic arc and back-arc systems in the Bohemian segment, while the magmatic activity in the FMC was comparably short-lived.

Palaeomagnetic investigations of the Corso-Sardinian block and Maures–Estérel show that there has been a change in their magnetic orientation during the Late Carboniferous–Early Permian period (305–280 Ma). This trend is interpreted in terms of a large-scale 90° clockwise rotation of the southern branch of the Variscan belt that matches the successive change in shortening directions revealed by structural geology. The evidence is based on existing structural studies of the fabrics of syntectonically emplaced granitoids partly based on the anisotropy of magnetic susceptibility, combined with a large database of isotopic ages. The chronological match between the palaeomagnetic and tectonic datasets is interpreted here as a result of large-scale dextral wrench movements in the lithosphere between the Gondwana and Laurussia supercontinents. This wrench deformation is regarded as a sequel to the dextral rotation of the northern branch of the Variscan belt during 330–315 Ma which terminated in frontal collision with Avalonia. The continuation of movement in the southern Variscan realm was due to shearing along the southern margin of the Avalonian block. An additional clockwise rotation is inferred to have taken place during the Triassic period. The age of this motion remains to be determined.Supplementary material:Palaeomagnetic and geochronological data from the Maures–Estérel, Corsica–Sardinia block presented in Figure 7 and discussed in the text are available at http://www.geolsoc.org.uk/SUP18742.

Geochronology, structural and anisotropy of magnetic susceptibility data from the northern Vosges batholith, which belongs to the Northern Vosges-Mid-German Crystalline Rise arc, show contrasting emplacement modes of southern granodiorites and northern granites. The ENE-WSW-trending fabrics of granodiorites (346-334 Ma) are parallel to the metamorphic cleavage affecting the host rocks developed during regional compression. The NNW-SSE-trending fabrics of younger granitoids (c. 330 Ma) reveal an extensional emplacement mode, associated with a normal shear zone separating the two magmatic suites. Palaeomagnetism shows that the switch from a compressive to an extensional regime coincides with a regional counterclockwise rotation. The 330-325 Ma extension is further supported by palaeomagnetic and seismic data indicating southeastward tilt of the whole batholith. Finally the system is rotated clockwise without any structural overprint. Data from the Early Carboniferous northern Vosges magmatic arc and remote Bohemian Massif suggest that this evolution is valid for the whole eastern branch of the European Variscan belt, for which the following model is proposed: (1) Late Devonian-Early Carboniferous east-west shortening of the Variscides above the Rhenohercynian subduction zone; (2) axial NNW-SSE shortening of the assembled Variscan orogen associated with (3) 'internal' sinistral rotation of inherited Rhenohercynian transform faults and shortening of intervening blocks; (4) east-west extension and dextral 'external' rotation of blocks between dextrally reactivated transforms. [ABSTRACT FROM AUTHOR]

The degree of the anisotropy of magnetic susceptibility (AMS) of basaltic rocks, as is known from the large AMS database of these rocks, is generally very low, while in more acidic volcanic rocks such as andesites, trachytes and phonolites, which have been investigated much less frequently, it is in general much higher. In the present study, the AMS of various volcanic rocks including trachytic and phonolitic rocks was investigated in the Tertiary volcanic region of the České středohoří Mts. Viscosities of the respective lavas were calculated from the chemical composition using the KWARE program. A rough correlation was found between the degree of AMS and lava viscosities, probably resulting from different mechanisms orienting the magnetic minerals. In basaltic lava flows this mechanism is traditionally considered to be of a hydrodynamic nature, in trachytic and phonolitic bodies it can also be represented by quasi-intrusive flows resembling, at least partially, ductile flow deformation. This is in agreement with the AMS data predicted by the viscous (liquid flow) and line/plane (ductile flow) models.

Background & aims: The risk for small bowel cancer (SBC) is significantly increased in hereditary nonpolyposis colorectal cancer (HNPCC). HNPCC-associated SBCs are poorly characterized. Methods: Thirty-two SBCs were characterized according to clinical, pathologic, and germline mutation data. Histomorphologic characteristics, microsatellite instability (MSI) testing, mismatch repair (MMR) protein expression, and frameshift mutations of 7 coding mononucleotide repeats were investigated in 17 SBCs. Results: Median age at diagnosis was 39 years. Fifty percent of SBCs were located in the duodenum. The Amsterdam criteria were fulfilled in 50% of patients; 45% of patients had no personal history of previous malignancies. Two patients had a positive family history for SBC. Pathogenic germline mutations were identified in 81%; high MSI was detected in 95% and loss of MMR protein expression in 89% of cases. TGFBR2, BAX, MSH3, MSH6, ACVR2, AIM2, and SEC63 frameshift mutations were detected in 69%, 59%, 59%, 35%, 82%, 56%, and 56%, respectively. An expansive growth pattern of the tumor border and an intense intratumoral lymphocytic infiltrate were present in 75%, respectively. Conclusions: HNPCC-associated SBC often manifests at a young age and may be the first disease manifestation. Endoscopy may detect 50% of tumors. Considering recent data on gastric cancer, we propose endoscopic screening of mutation carriers starting at 30 years of age because clinical criteria cannot define a high-risk group. In addition, our study shows that histopathologic criteria, MSI, and MMR immunohistochemistry are often similar to these features in HNPCC.

Presents a range of paleomagnetic, as well as structural and geochronological arguments, involving the rotations of the Eastern Variscides accommodated by dextral lithospheric wrenching. Geological setting of Bohemian Massif; Components of natural remanent magnetization; Magnetizations in early carboniferous plutons.

The Staré Město (SM) belt (NE margin of the Bohemian Massif) represents a preserved example of an intracontinental Cambro-Ordovician rift that has been shortened during the Variscan orogeny. The rifted sequence consists of gabbroic intrusions and a leptyno-amphibolite complex of Cambro-Ordovician protolith age. The latter suffered medium pressure, granulite facies, Cambro-Ordovician metamorphism associated with extension in a continental protorift. The Variscan tectonometamorphic event is manifested by convergent orogenesis with syn-convergent intrusion of a Carboniferous tonalitic sill, high temperature–medium pressure compressional deformation of gabbros and high temperature metamorphism of peridotites.

Intra-continental deformation of soft zones during continental collision requires weak continental lithosphere which is able to be shortened across considerable width during later convergence. This enables significant thickening with formation of an orogenic root. We have examined models with a history of lithospheric thinning by pure shear during an earlier phase of intra-continental extension with associated heating. Geologically this situation is appropriate to intra-continental rifts and back-arc basins.

Theoretical AMS was calculated from the phyllosilicate fabric determined by universal stage microscopy and X-ray pole figure goniometry in weakly magnetic rocks whose AMS is generally regarded as controlled by paramagnetic mineral fabric. Reasonable correlations between theoretical and measured AMS were found, but not perfect. A better correlation exists between theoretical AMS and measured paramagnetic component AMS.

Zusammenfassung Der Deckenbau am Ostrand der Böhmischen Masse erfolgte in zwei aufeinanderfolgenden Stadien, die sich sowohl in ihrer Kinematik als auch in ihrer Metamorphoseentwicklung deutlich voneinander unterschieden.

The behaviour of rigid triaxial ellipsoidal particles in slowly moving viscous flows has been studied by means of numerical solution of Jeffery's (1922) equations. The motion of a single particle as well as a multiparticle system evolution in the combined pure shear and simple shear flow was modeled. The development of a preferred orientation depends on particle axial ratios and the flow geometry. Stable fabrics are produced only for sufficiently high components of pure shear. For lower pure-shear components oscillating fabrics develop, periodic in the case of spheroidal (biaxial) particles and irregularly oscillating in the case of triaxial ones. The fabric symmetries may not directly reflect the flow geometry in the case of triaxial particles.

Abstract In the scope of a prospective multi-centre study after neoadjuvant combined chemotherapy (carboplatin, ifosfamide, etoposide, vindesine) and radiotherapy (45 Gy) 40 resection specimens of locally advanced non-small-cell lung cancer were analysed in order to establish reproducible pathological/anatomical results of tumour regression. Resection specimens of 28 squamous cell carcinomas and 12 adenocarcinomas were investigated using serial sections of the primary lesion. The mean age of the patients was 57 years. The results were compared to spontaneous regressive changes in a control group of 50 untreated non-small-cell lung cancers. Marked scarry fibrosis in the region of the former primary tumour, concentric foci of fresh tumour necroses and surrounding foam cell clusters with transition into vascular granulation tissue could be established as characteristic features of therapy-induced tumour regression, whereas untreated carcinomas revealed necroses with adjoining vital tumour tissue. Using a three-step regression system, 3 tumours could be classified as grade I (no or only slight tumour regression), 10 tumours as grade IIA (marked but incomplete tumour regression, more than 10% vital tumour tissue), 20 tumours as grade IIB (less than 10% vital tumour tissue) and 7 tumours as grade III (complete tumour regression without vital tumour tissue). After a median follow-up period of 32.3 months in patients with grade IIB or III tumour regression ("responders") the median survival time of 27.9 months was found to be significantly longer than in patients with grade I or IIA tumour regression ("non-responders") with a median survival period of 13.7 months (log-rank test, P=0.020). The resection specimens analysed, which were obtained 7 weeks (on average) after the end of radiochemotherapy, did not show specific changes due to preoperative therapy, but quite characteristic histological alterations in the former tumour area were registered, which had been induced by combined neoadjuvant radiation and chemotherapy. The grade of therapy-induced tumour regression could be shown to be a significant prognostic factor in non-small-cell lung cancer.

Phase equilibrium modelling of metagranitoids and metapelites in the MnO--Na2O--CaO--K2O--FeO--MgO--Al2O3--SiO2--H2O system was used to characterize Variscan and Alpine metamorphism in the crystalline basement of the Vepor Unit, West Carpathians. The calculated P--T conditions range between 570--670 °C and 6--8.5 kbar for the Variscan and 430--600 °C and 5--11 kbar for the Alpine event. These two events show contrasting metamorphic field gradients and P--T evolutions, indicating 22--27 °C km-1 during the retrograde Variscan metamorphism and 15--18 °C km-1 during the prograde Alpine metamorphism. The prograde Alpine metamorphism is associated with the Early Cretaceous overthrusting of the southern Gemer Unit, which resulted in apparently contemporaneous burial and horizontal ductile spreading of the underlying Vepor basement. The argon diffusion modelling was used to interpret the existing Variscan, Alpine and mixed 40Ar/39Ar cooling ages, and to constrain the T--t evolution and Alpine thermal overprint. Constructed Alpine metamorphic isograds and isotherms show horizontal P--T gradients resulting from heterogeneous exhumation of the deeper parts of the Vepor basement along two narrow belts during later folding. Here the structurally deeper metapelites form large-scale anticlinal cusp-like structures that separate structurally higher metagranitoids. [ABSTRACT FROM AUTHOR]