Search

In oblique collision settings, parallel and perpendicular components of the relative plate motion can be partitioned into different structures of deformation and may be localized close to the plate boundary, or distributed on a wider region. In the Southern Alps of New Zealand, it has been proposed that one-third of the regional convergence is distributed in a broad area along the Southern Alps orogenic wedge. To better document and understand the regional dynamics of such systems, reliable markers of the horizontal tectonic motion over geological time scales are needed. River networks are able to record a large amount of distributed strain and they can thus be used to reconstruct the mode and rate of distribution away from major active structures. To explore the controls on river resilience to deformation, we develop an experimental model to investigate river pattern evolution over a doubly-vergent orogenic wedge growing in a context of oblique convergence. We use a rainfall system to activate erosion, sediment transport and river development on the model surface. At the end of the experiment, the drainage network is statistically rotated clockwise, confirming that rivers can record the distribution of motion along the wedge. Image analysis of channel time-space evolution shows how the fault-parallel and fault-perpendicular components of motion decrease toward the fault and impose rotation to the main trunk valleys. However, rivers do not record the whole imposed rotation rate, which suggest that the natural lateral channel dynamics can alter the capacity of rivers to act as passive markers of deformation. [ABSTRACT FROM AUTHOR]

Varying amounts of gold mineralisation is occurring in all young and active collisional mountain belts. Concurrently, these syn-orogenic hydrothermal deposits are being eroded and transported to form placer deposits. Local extension occurs in convergent orogens, especially oblique orogens, and facilitates emplacement of syn-orogenic gold-bearing deposits with or without associated magmatism. Numerical modelling has shown that extension results from directional variations in movement rates along the rock transport trajectory during convergence, and is most pronounced for highly oblique convergence with strong crustal rheology. On-going uplift during orogenesis exposes gold deposits to erosion, transport, and localised placer concentration. Drainage patterns in variably oblique convergent orogenic belts typically have an orogen-parallel or sub-parallel component; the details of which varies with convergence obliquity and the vagaries of underlying geological controls. This leads to lateral transport of eroded syn-orogenic gold on a range of scales, up to > 100 km. The presence of inherited crustal blocks with contrasting rheology in oblique orogenic collision zones can cause perturbations in drainage patterns, but numerical modelling suggests that orogen-parallel drainage is still a persistent and robust feature. The presence of an inherited block of weak crust enhances the orogen-parallel drainage by imposition of localised subsidence zones elongated along a plate boundary. Evolution and reorientation of orogen-parallel drainage can sever links between gold placer deposits and their syn-orogenic sources. Many of these modelled features of syn-orogenic gold emplacement and varying amounts of orogen-parallel detrital gold transport can be recognised in the Miocene to Recent New Zealand oblique convergent orogen. These processes contribute little gold to major placer goldfields, which require more long-term recycling and placer gold concentration. Most eroded syn-orogenic gold becomes diluted by abundant lithic debris in rivers and sedimentary basins except where localised concentration occurs, especially on beaches. [ABSTRACT FROM AUTHOR]

The Chinese Altai in the Central Asian Orogenic Belt is characterized by the occurrence of kyanite- and andalusite-type metamorphic zones. However, the tectonic setting associated with these metamorphic zones is still debated. Here we present structural observations from the southern Chinese Altai (Aletai area), where a relict kyanite zone occurs within an andalusite-type metamorphic zonal sequence of sillimanite, andalusite-sillimanite, andalusite-staurolite, staurolite-garnet and biotite. We document two major phases of folding in this area. The earlier structures (D 1 ) developed synchronously with kyanite growth and are represented by an axial planar fabric of tight folds. D 1 fabric is mostly obliterated by later deformation, but is inferred to be penetrative as indicated by a profound intersection lineation (L 21 ). The second generation of deformation (D 2 ) is associated with superimposed F 2 folds and a dominant axial planar foliation (S 2 ) with ~ NW–SE orientation. Microstructural observations show that D 2 structures are associated with the andalusite-type metamorphic series, which is characterized by an early-D 2 occurrence of sillimanite, staurolite-garnet and biotite zonal sequence overprinted by the late-D 2 growth of andalusite. Combining with previous metamorphic data, we consider that these two folding events (D 1 and D 2 ) correspond with the development of kyanite- and andalusite-type metamorphic zones, respectively, which records the burial and exhumation history of metamorphic rocks possibly in response to Devonian-Carboniferous accretion/collision and Permian transpressional tectonics. The latter was associated with oblique convergence between the Chinese Altai and the intra-oceanic arc system of the East/West Junggar. [ABSTRACT FROM AUTHOR]

The rheology of décollement materials fundamentally constrains the kinematic evolution and tectonic architecture of orogenic belts. In this paper, we present the result of an experimental program designed for investigating, by sandbox analog modeling, the impact of the spatial distribution of décollement rheology underneath an inner carbonate platform-basin-outer carbonate platform paleogeographic architecture undergoing traspressional deformations. Our models indicate that viscous décollements at the base of both platforms favor the outward propagation of deformation, duplexing in the Inner Platform (that faces the wedge toe), and deep burial of basinal sediments. On the other hand, frictional rheologies favor internal shortening in the basin, strong uplift and limited burial. Application of experimental results to better constrain the late Cretaceous tectonic evolution of the NW Zagros is discussed. [ABSTRACT FROM AUTHOR]

Zagros Folded and thrust Belt (ZFTB) is a Cenozoic mountain belt in SSW of Iran and northeast of Arabia that resulted from closure of Neo-Tethys and collision between Arabia passive margin and Central Iran active margin. At this tectonic grain of Alp-Himalayan chain, change of the tectonic regime, degree of basement involvement, and character of accommodation of the deformation, in time and space, has been under debate. The results show that the deformation along the Zagros is not uniformly accommodated. Although the researchers have already paid attention to basement involvement in addition to the sedimentary cover rocks, little has been shown on the role of the basement's rigidity and lower crust's rheology on the deformation pattern along and across the belt. This study tries to address these questions in terms of inversion of slip vector of basement earthquakes, measurement of fault-slip data on the cover rocks, geomorphic and field observations, and existing geodetic and gravity data, with especial focus on Dezful embayment and surrounding area. The results show the Dezful embayment plays an indenter role. It, with the other reentrants, changes the obliquity of Arabian plate convergence, facilitates the escape of the upper crust toward free mechanical boundaries in salients, controls the slip-rate of Zagros Main Recent Fault at the rear of the belt and contributes in forming Zagros Fold-and-Thrust Belt as an orocline. The viscous lower crust helps the strain partitioning by providing a ductile shear base under the rigid upper crust. [ABSTRACT FROM AUTHOR]

Knowledge of the crustal structure is important for understanding the tectonic framework and geological evolution of southeastern China and adjacent areas. In this study, we integrated the datasets from the TAIGER (TAiwan Integrated GEodynamic Research) and ATSEE (Across Taiwan Strait Explosion Experiment) projects to resolve onshore-offshore deep crustal seismic profiles from the Wuyi-Yunkai orogen to the Taiwan orogen in southeastern China. Three seismic profiles were resolved, and the longest profile was 850 km. Unlike 2D and 3D first arrival travel-time tomography from previous studies, we used both refracted and reflected phases (Pg, Pn, PcP, and PmP) to model the crustal structures and the crustal reflectors. In total, data from 40 shots, 2 earthquakes, and approximately 1,950 stations were used; 15,612 arrivals were selected among three transects. Using these data, we determined the complex crustal evolution since the Paleozoic era , involving the closed Paleozoic rift basin in central Fujian, the Cenozoic extension due to the South China Sea opening beneath the coastline of southern Fujian, and the on-going collision of the Taiwan orogen. The shape of the Moho, which also reflects the crustal evolution, can be summarized as follows: ~ 30 km deep to the west of Fujian, deepening toward central Fujian (~ 35 km), becoming shallower toward the Taiwan Strait (~ 28 km), deepening again toward the mountain belt of Taiwan (~ 42 km), and becoming shallower toward the Pacific Ocean (~ 10 km). [ABSTRACT FROM AUTHOR]

Recent drilling of the first Collisional Orogeny in the Scandinavian Caledonides scientific borehole (COSC-1) near Åre, Sweden permitted a laboratory investigation of seismic anisotropy on high metamorphic grade and highly deformed core samples. The 2.5 km deep borehole crosscuts the amphibolite-grade Lower Seve Nappe and intersects a high-strain shear zone in the lowermost 800 m. Measurements of ultrasonic compressional ( V p ) and shear ( V s ) velocities are conducted at room temperature and pressures ranging from room conditions up to 260 MPa on six core sections that represent the most abundant lithologies in the borehole. The core sections consist of two amphibolites, a calc-silicate gneiss, a felsic gneiss, an amphibole-rich gneiss, and a garnet-bearing micaschist from the shear zone. Three mutually perpendicular samples were taken to characterize the anisotropy induced by the clear foliation and lineation. The intrinsic (crack-free velocities) V p 0 and V s 0 in the direction perpendicular to foliation ranges from 5.51 to 6.67 km/s and 3.31 to 4.13 km/s, respectively. In the direction parallel to foliation the V p 0 and V s 0 ranges from 6.31 to 7.25 km/s and 3.53 to 4.35 km/s, respectively. V p anisotropy ranges from 3% in the calc-silicate gneiss to 19% in the micaschist. In the upper crustal seismic reflection survey around the COSC-1 borehole, reflection coefficient analysis suggests that reflectors occur due to impedance contrast between commonly occurring amphibolites and gneisses in the upper 1800 m and the micaschists below. When extrapolated to mid-crustal levels the analysis indicates that both rock types can produce reflection coefficients between adjacent lithologies in excess of 0.1. Similarities in lithologies, shear zone thickness, and reflectivity pattern in the Central Scandinavian Caledonides compared to other orogens (e.g., the Himalaya) demonstrate the importance of these measurements as a proxy for in-situ strongly anisotropic shear zones in the middle crust. [ABSTRACT FROM AUTHOR]

In this study we analyze a ~ 300 km long segment of the Alpine-Carpathian orogen using novel outcrop data and regional seismic profiles from the West Carpathians to unravel the kinematics and timing of Eocene to Late Miocene deformation of the fold-thrust belt. Comparison with data from the Eastern Alps and the Vienna Basin leads to an updated tectonic model for the Paleogene and Neogene of the Alpine-Carpathian transition, which includes three stages: (1) Eocene to Early Oligocene NNW-directed foreland-propagating thrusting. Thrusts are directed perpendicular to the strike of the European foreland in the Outer West Carpathians (OWC) and sub-parallel to thrusts observed in the Eastern Alps west of the Vienna Basin. (2) Continued Late Oligocene to Early Miocene NNW-directed foreland-propagating thrusting simultaneous with sinistral strike-slip reactivation of former nappe boundaries in the hinterland of the active thrusts. This deformation corresponds to the early stage of eastward lateral extrusion of the Eastern Alps. The ENE-striking sinistral faults in the OWC are kinematic equivalents of the SEMP fault system in the Eastern Alps, which was active at the same time. The latest stage of thrusting is characterized by SSE-directed out-of-sequence thrusts in the hinterland of the OWC and the reactivation of Variscan basement thrusts in the European foreland as SSE-directed backthrusts. (3) Formation of (N)NE-striking sinistral strike-slip faults which are kinematically linked to (N)NE-directed out-of-sequence thrusts post-dating NNW-directed thrusting. The sinistral faults formed coeval with the opening of the Vienna pull-apart basin during the Middle to Late Miocene stage of lateral extrusion. Unlike proposed in previous studies the West Carpathians do not appear to be affected by Oligocene to Early Miocene crustal-scale wrenching of the Pieniny Klippen Belt. Our data show that the deformation of the PKB is in line with the Eocene to Late Miocene tectonic evolution reconstructed for the OWC. [ABSTRACT FROM AUTHOR]

Devonian sandstones in the Shanyang area crop out in the southern part of the Qinling Orogenic Belt. Geochemical analyses show that the sandstones are enriched in Zr and have high Th/U and Rb/Sr ratios indicating the sandstones underwent repeated recycling. Zircon, tourmaline, apatite, rutile and anatase are the predominant heavy minerals while minor minerals include spinel, pyroxene, ilmenite and magnetite. The mineral compositions of detrital tourmaline grains indicate that the alkali compositional subgroup dominates; schorl and dravite are the main tourmaline species. A tourmaline composition environment discrimination diagram shows that about 70% grains are consistent with metapelite, metapsammite, and calc-silicates sources and about 30% of grains are from granitoids and associated pegmatites, and aplites. Metamorphic and granitic rocks in the Qinling Complex area are potential provenance. Overall data from geochemistry, heavy minerals and tourmaline chemistry suggests the Devonian sandstones were extensively recycled in a foreland basin setting rather than at a passive continental margin. [ABSTRACT FROM AUTHOR]

The sources of ancient zircons and the tectonic attributions and origins of metamorphic complexes in Phanerozoic accretionary orogens have long been difficult issues. Situated between the Tianshan and Inner Mongolia orogens, the Beishan orogenic collage (BOC) plays a pivotal role in understanding the accretionary processes of the southern Central Asian Orogenic Belt (CAOB), particularly the extensive metamorphic and high-strained complexes on the southern margin. Despite their importance in understanding the basic architecture of the southern CAOB, little consensus has been reached on their ages and origins. Our new structural, LA-ICP-MS zircon U-Pb and Hf isotopic data from the Baidunzi, Shibandun, Qiaowan and Wutongjing metamorphic complexes resolve current controversial relations. The metamorphic complexes have varied lithologies and structures. Detrital zircons from five para-metamorphic rocks yield predominantly Phanerozoic ages with single major peaks at ca. 276 Ma, 286 Ma, 427 Ma, 428 Ma and 461 Ma. Two orthogneisses have weighted mean ages of 294 ± 2 Ma and 304 ± 2 Ma with no Precambrian inherited zircons. Most Phanerozoic zircons show positive εHf (t) values indicating significant crustal growth in the Ordovician, Silurian and Permian. The imbricated fold-thrust deformation style combined with diagnostic zircon U-Pb-Hf isotopic data demonstrate that the metamorphic rocks developed in a subduction-accretion setting on an arc or active continental margin. This setting and conclusion are supported by the nearby occurrence of Ordovician-Silurian adakites, Nb-rich basalts, Carboniferous-Permian ophiolitic mélanges, and trench-type turbidites. Current data do not support the presence of a widespread Precambrian basement in the evolution of the BOC; the accretionary processes may have continued to the early Permian in this part of the CAOB. These relationships have meaningful implications for the interpretation of the tectonic attributions and origins of other metamorphic complexes in Central Asia and other ancient accretion-dominated orogens. [ABSTRACT FROM AUTHOR]

Recent studies have documented marine turbidites with syn-sedimentary deformation features in the central Sulu orogenic belt of eastern China. These units preserve essential information on the Late Mesozoic evolution of the Sulu orogenic belt. Referred to as the Baxiandun Formation, the turbidites exhibit similar lithologic characteristics to nearby units such as the Lingshandao Formation that have been well studied even though precise geochronologic constraints are lacking for a more precise correlation. This study reports detrital zircon U Pb age data that correlate the Baxiandun Formation turbidites of the central Sulu orogenic belt to the Early Cretaceous Lingshandao Formation. We also report Al-in-hornblende emplacement depth estimates for granitic intrusions of the Sulu orogenic belt's Laoshan mountain. A sharp contact between the Laoshan granites and the marine Baxiandun Formation indicates that the Baxiandun basin rapidly subsided to the emplacement depth of the Laoshan plutons. Lateral correlation among the marine turbidites, the Lingshandao and Baxiandun Formations, combined with information established by previous studies indicates initiation of transpressional tectonics at 122–121 Ma. Transpression ceased with the emplacement of the Laoshan granites, whose A1-type composition indicates a return to extensional tectonics at ca. 111 Ma. [ABSTRACT FROM AUTHOR]

The Tananao Schist Belt is a low-pressure metamorphic complex comprised of three lithological units of marble, schist formation, and granite, in ascending order of proportion. Previous studies have found that the schist formation was formed during the Mesozoic. However, there is a lack of geochronological data to corroborate the schist protolith and metamorphic ages. In this study, we have used U Pb zircon geochronology to provide a time frame for the creation of the schist formation and metamorphism, as well as a new tectonic model. Twenty-three schist and eleven meta-magmatic samples were used for U Pb dating by LA-ICP-MS. Results from the youngest peak age of detrital zircon indicate that the schist formed in a new depositional age of 120–110 Ma and, therefore, is different from the previously estimated age of the Paleozoic-Mesozoic. Additionally, the block-in-matrix schist indicates an age that ranges from 270 to 80 Ma and was inferred from the chaotic deposits to be a metamorphic mélange. The Tananao Schist Belt appears to represent an arc-trench system that formed during the Cretaceous in the South China Block margin. Moreover, the youngest U Pb age of 80 Ma from the leucogranite dike and schist, constrains the upper age limit for a metamorphism that is younger than the previously accepted age of 100–90 Ma. The contact layer between Permian-Triassic marble and the overlying early Cretaceous schists remains a chloritoid bed that is, therefore, considered to be a paleosol at the unconformity, which formed over an extended duration of 60 ± 30 Ma. The stratigraphic contact indicates a long period of erosion during the Jurassic and suggests that a tectonic event occurred. However, we propose that two important metamorphic events took place prior to, and following, the schist formation during the Jurassic and late Cretaceous orogenic events. [ABSTRACT FROM AUTHOR]

Due to the Mesozoic multi-plate convergence, prominent continental marginal tectonic belts were formed in East Asia. The significant intra-continental magmatic events in the interior of East Asia were also closely related to the subduction of the surrounding oceans. Therefore, clarifying the subduction-related mantle dynamics during the Mesozoic super-convergence in East Asia is critical in understanding the crust-mantle interactions and the episodic tectono-magmatism. In this study, we obtain the subduction-related dynamic topography by coupling global mantle flow and plate reconstruction motions to capture the evolution scenarios in 200–90 Ma. Our modeling results are as follows: (1) In the Early Jurassic, the East Asian continental margin breakup is closely related to the mantle-driven dynamic topography. The offshore dynamic subsidence dominates the continental breakup. (2) The closure of the Paleo-Tethys Ocean and the subduction of the Bangonghu-Nujiang Ocean contribute to the southward migration of the dynamic topography. Concurrently, the continuous subduction of the Paleo-Pacific Plate leads to the onshore dynamic uplift, which results in subduction-related orogenesis in eastern East Asia. The dynamic uplift does not massively progress westward in Mainland China, suggesting that extensive intra-continental compressional deformation results from tectonic uplift rather than mantle-induced dynamic uplift. (3) The regression of the dynamic subsidence zone since 130 Ma marks the start of the topographic collapse in the East Asian continental margin through the back-arc extension. (4) The alternating compression-extension scenarios are identified in the main compressional and extensional stages, respectively, showing that dynamic topography is closely related to the evolution of the marginal tectonic belts in eastern East Asia. In conclusion, the subduction-related dynamic topography systematically reveals the deep dynamics involved in the formation, evolution, and collapse of the marginal tectonic belts in East Asia and is of great significance in understanding the related mantle dynamics during the Late Mesozoic. • We obtain the Late Mesozoic subduction-related dynamic topography models in East Asia. • Subduction-related dynamic topography can reveal the episodic evolution of the marginal orogenic belts of eastern East Asia. • Tectonic uplift is the primary driver of Late Mesozoic intracontinental deformation in South China. [ABSTRACT FROM AUTHOR]

The Qinling orogenic belt and surrounding areas are a junction zone in Central China that connects the North China craton, Yangtze craton and northeastern Tibetan plateau. This area is in a key position within the more general framework where there is eastward extrusion of the Tibetan plateau and westward subduction of the Pacific plate. There is an ongoing scientific debate on how these two main processes are driving the geodynamic evolution of the Qinling orogenic belt and surrounding areas. Specific mechanisms have been proposed, such as lower crustal flow, crustal shortening and big mantle wedge tectonics. Knowledge of the seismic velocity structure helps us understand how these two driving forces affect the tectonic blocks of the study area, as well as test how well the proposed mechanisms to fit the regional velocity structure. For this purpose, a high-resolution P-wave velocity model of the crust and uppermost mantle was obtained by inverting arrival times from local earthquakes that occurred in the Qinling and surrounding region. Our three-dimensional (3D) model suggests that crustal channel flow cannot exist in the whole Qinling orogenic belt, and the localized low-velocity zone generated by the horizontal compressive stress caused by the collision of the Indian and Eurasian plates, is a possible explanation for the growth of the northeastern Tibetan plateau. The contrast in seismic velocities found under the east-Qinling and the west-Qinling orogenic belts implies a different response of these two terranes to the eastward extrusion of the Tibetan plateau. Our velocity model points to relatively stable structural features in the east-Qinling and the Weihe graben, while a low-velocity anomaly in the uppermost mantle of the southernmost Ordos plateau suggests that the lithosphere of the southern Ordos plateau is undergoing destruction. • High-resolution P-wave velocity model that includes independent Moho data. • Different response of west- and east-Qinling to the eastward extrusion of the TP. • The southern Ordos plateau is likely undergoing destruction. [ABSTRACT FROM AUTHOR]

The timing and mechanism of the combination between the South China Block (SCB) and the Indochina Block (IB) are controversial. Three ophiolitic mélange zones (Ailaoshan, Song Ma, and Song Chay) have been proposed as suture zones within this collisional orogen. However, the relationships among the three corresponding tectonic belts are unclear. In this study, we present detailed structural data for the three tectonic belts. The bulk architectures of the Ailaoshan, Song Ma, and Song Chay belts correlate well with one another. This similarity is also revealed by our new zircon U Pb geochronological results from the Song Ma and Song Chay ophiolites. The regional deformation age is constrained to between 250 and 240 Ma by our new muscovite 40Ar/39Ar ages, and the medium-low temperature conditions are revealed by the quartz c-axis fabric. Considering the transformation effect of the Cenozoic large-scale sinistral strike-slip of the RRF and DBF, the Early Mesozoic Ailaoshan, Song Ma, and Song Chay suture zones should represent different segments of the same belt. Based on this hypothesis, we compiled the ages of the magmatism in this region, which allows us to propose an evolutional model as follows: i) ∼380–310 Ma continental rifting and subsequent Ailaoshan–Song Ma–Song Chay ocean spreading as a branch of the Paleo-Tethys, ii) ∼310–250 Ma oceanic subduction coeval with continental-arc magmatism, iii) ∼250–240 Ma continental collision, iv) ∼240–220 Ma post-collisional extension. • The linkage between Ailaoshan, Song Ma, and Song Chay tectonic belts was discussed. • The 40Ar/39Ar ages reveal deformation age in the Song Chay belt between 250 and 240 Ma. • Regional geochronological works constrain the evolution of Eastern Paleo-Tethys. • Rifting-ocean spreading: 380–310 Ma, subduction: 310–250 Ma, collision: 250–240 Ma. [ABSTRACT FROM AUTHOR]

The subduction dynamics and deformation style have been classically understood under a vision of trench-orthogonal plate convergence. We perform 3-D upper mantle-scale analog models to further understand the dynamics of subduction systems and overriding plate strain distribution under varying convergence angles and in the presence or absence of intraplate inherited weak zones. The laboratory experiments show that whatever the obliquity of convergence, the subduction dynamics is largely influenced by the interaction of the slab with the 660 km discontinuity. The slab geometry alternates between stages of slab shallowing and steepening, which are accompanied by alternating periods of shortening and stretching (or moderate shortening) of the overriding plate, respectively. As convergence departs from being orthogonal and in the absence of an intraplate inherited weak zone, strain within the overriding plate shifts from pure shear to sub-simple shear. When a lithospheric-scale weak zone is introduced along the forearc-arc interface and under trench-oblique convergence, the strain is partitioned and the forearc develops sliver motion - and independent deformation - from the rest of the overriding plate. The forearc evolution is characterized by a three-step history: (i) detachment and oceanward motion, (ii) advancing motion toward the continent, and, (iii) accretion that can ultimately lead to underthrusting of the forearc. Decreasing slab dip increases the interplate force, resulting in larger stresses applied on the intraplate fault separating the forearc sliver from the continent. Hence, models show that because larger compression increases the coupling between the forearc and the plate, it does not favor sliver motion. • We perform upper mantle-scale subduction experiments in the laboratory to assess the trench-oblique plate convergence. • Some subduction experiments were modeled with a weak zone to investigate the role of inheritance on sliver tectonics. • The overriding plate strain shift from pure-shear to sub-simple shear when convergence departs from orthogonal to oblique. • Sliver tectonics only is developed when the overriding plate is embedded with a weak zone, simulating an inherited structure. • The experimental results yield new insights to evaluate the evolution of subduction-related orogens with sliver block. [ABSTRACT FROM AUTHOR]

The final collisional orogenesis in accretionary orogens is crucial for reconstructing the whole orogenic circle and understanding the material and energy recycling along convergent margins. However, it is always not straightforward to be addressed, particularly when the final suturing following the ocean closure occurred softly, for instance, the Central Asian Orogenic Belt (CAOB). In this study, a comprehensive dataset of detrital zircon U-Pb ages and Hf isotopes for the Middle Permian to Middle Jurassic foreland sediments from the Linxi region, southeastern CAOB, is synthesized. We observed multiple abrupt changes in sedimentary provenance over time from this dataset: (1) the ca. 275 Ma sediments (Upper Zhesi Fm.) were entirely sourced from the local NAO, whereas the ca. 270–258 Ma sediments (Middle-Upper Linxi Fm.) received an additional detritus contribution from the northern NCC, (2) the ca. 257–236 Ma sediments (Lower-Middle Xingfuzhilu Fm.) returned to a pure NAO source, but the slightly postdated ca. 227 Ma sediments (Upper Xingfuzhilu Fm.) show provenance affinities of both NAO and northern NCC, (3) the ca. 171 Ma sediments (Middle Xinmin Fm.) were exclusively derived from the Late Paleozoic to Early Mesozoic magmas in the NAO and northern NCC with no Early Paleozoic and Precambrian detritus. The above episodic shifts in sedimentary provenance observed in the Linxi region, in conjunction with other regional geological evidence, provide key constraints on the pre- to post-collisional evolution in the southeastern CAOB, including the transition from waning subduction to initial collision, subsequent slab break-off and intracontinental contraction, and the post-collisional extension before the superposition of the Paleo-Pacific tectonic regime. Our results show that understanding the spatio-temporal changes of sedimentary provenance of the foreland basins systems during the plate convergence and orogenic evolution can aid in exploring the final collisional dynamics and evolutionary history in ancient accretionary orogens. • Foreland deposition brings insight into collisional dynamics in accretionary orogens. • Detrital U-Pb-Hf data reveal episodic changes of sedimentary provenance in Linxi. • First arrival of northern NCC detritus to the frontal NAO by ca. 270 Ma. [ABSTRACT FROM AUTHOR]

The morpho-tectonic evolution of the Tibetan Plateau is controlled by complicated interactions between tectonic uplift and surface erosion. The Gangdese batholith in the southern Lhasa terrane is a key orogenic belt for exploring the complicated morpho-tectonic evolution of the Tibetan Plateau. In this contribution, we apply apatite fission track (AFT) thermochronology to constrain the thermo-tectonic evolution of the central segment of the Gangdese batholith. Twenty-four granitoid samples were collected from both river valleys (e.g., the Yarlung and Xiang Rivers) and from the internal batholith areas located farther from river drainage (and/or local faults) networks. All samples exhibit Miocene AFT ages between ∼19.9 and ∼ 6.1 Ma. Inverse thermal history modeling results reveal that the central Gangdese batholith underwent a two-stage accelerated basement cooling in the Miocene. The first cooling stage took place during the late Oligocene to middle Miocene (∼25–15 Ma), this period of moderate to rapid basement cooling coincides with activity along the Gangdese thrust and Great Counter thrust system, and the Oligocene-Miocene delamination of the Lhasa lithosphere and concomitant asthenosphere upwelling. These tectonic processes acted as first-order control on regional basement uplift, denudation and exhumation. Second, a middle-late Miocene (∼14–5 Ma) rapid cooling is widely recognized in the whole Gangdese batholith. We suggest that this middle-late Miocene cooling is due to exhumation in response to tectonic and surface erosion processes such as N-S normal faults and enhanced river incision induced by the intensification of Asian monsoon. Finally, in combination with published low-temperature thermochronological and paleoaltimetry data, it is deduced that the present-day low-relief landscape of the southern Lhasa terrane resulted from a long-term balance between intense regional tectonic activity and surface erosion. • The central Gangdese experienced a two-stage rapid cooling during the late Oligocene - Miocene. • Current topography in southern Tibet was a result of an intricate balance between tectonic activity and surface erosion. • An updated model for the morpho-tectonic evolution of the central Gangdese belt is put forward. [ABSTRACT FROM AUTHOR]

Low Strain Rate regions (LSRrs), i.e., areas undergoing tectonic deformation at rates of 1 mm/yr or less, often host important cities and highly vulnerable anthropogenic assets, and due to their subdued topography and relatively infrequent seismicity, are often considered low seismic hazard areas. Despite this, infrequent but high-magnitude earthquakes in such regions suggest that identifying active structures in the LSRr is one of the primary challenges for both the scientific community and modern societies. In such regions, one of the main issues in identifying active faults is the lack of valuable outcrop data due to erosional/sedimentation rates overwhelming the fault deformation, causing the hidden morphological signature of the tectonic structures. This work proposes a multidisciplinary approach designed to detect active geological structures and their related deformation in such areas. Our approach consists of quantitative morphotectonic, offshore and onshore tectonostratigraphic and GNSS joint analyses. To test this approach, we selected as a natural laboratory the partially offshore northern Sicilian LSRr (southern Italy) in the coastal sector located between the two major cities of Palermo and Termini Imerese. This area includes the compressional structures of the northern sector of the Apennine-Maghrebian fold and thrust belt, presently accommodating the slow Africa-Europe plate convergence. The main results we achieved are 1) new evidence of active tectonic deformation in this region; 2) the 3D modelling of two NNW-trending active faults; 3) the slip rate of a segment of the westernmost of the two detected faults; 4) a newly recorded relative GNSS velocity field; 5) a new morphotectonic map and morphotectonic evolution model of the study area. Our multidisciplinary approach allowed us to shed new light on the active tectonic framework of a slowly deforming area that crosses the physical limit of the coastline. • A land-to-sea approach for identifying active faults in low strain rate regions • Active faulting evidence along the northern Sicilian continental margin • New relative GNSS deformation field in the study area • 3D active fault geometric and kinematic parametrisation • Landscape morphotectonic evolution model [ABSTRACT FROM AUTHOR]

The Calabrian Arc subduction complex, in the northern Ionian Sea, is facing directly the westward subducting Apulian Swell, a sliver of continental crust covered by about 8 km of Mesozoic and Tertiary carbonates. Deformation patterns of this southernmost foreland segment of the Adria plate, analized from marine geological/geophysical data include: 1) flexure/bending, under the load of the advancing Calabrian Arc wedge; 2) buckling in response to compression of the surrounding orogens (southern Apennines, Dinarides-Hellenides); and 3) roll-back and eastward retreat of the slab. In this work, a reprocessed dataset of marine seismic reflection profiles is used to determine the interplay between these tectonic processes during progressive advancement of the Calabrian Arc wedge since Pliocene times. Our analysis indicates that the wedge is presently affected by compressive tectonics along several fore-thrusts, forming an imbricate fan system. Conversely, the Apulian Swell affected by inherited and rift-related Permo-Triassic normal faults, shows transpressive and positive tectonic inversions and, in its southern portion, the effects of the Hellenic fold/thrust belt shortening. The interference between the Calabrian Arc and the Hellenic chain plays an important role in controlling the tectono-stratigraphic evolution of the Apulian Swell, which underwent bending and roll-back during a pre-middle Pliocene stage followed by buckling processes. Active extension observed in the hinge zone of the Apulian Swell between Calabrian Arc and the Hellenides might suggest recent reactivation of flexure and retreat. • The response of a subducting plate trapped between two converging orogenic wedge is investigated. • The interference of Calabrian Arc (CA) and Hellenic chain plays an important role in defining the tectono-stratigraphic evolution of the Apulian Swell (AP) in Central Mediterranean Sea. • The advancement of the CA wedge and the Hellenides transmitted compressive stress to the foreland, leading to a tectonic inversion of previous Mesozoic faults. • Compressive deformation at the AP-CA wedge contact zone suggests that the west-dipping AP is already part of the orogenic wedge. • Compressive tectonics is active also in the central sector of the AP implying that collisional tectonics can be propagated over long distances from plate boundaries. [ABSTRACT FROM AUTHOR]

The Paleo-Asian Ocean eventually closed along the Solonker Suture Zone during the Late Permian and Early Triassic, before the collision between the Siberian Craton and the North China Craton (NCC) formed the eastern Central Asian Orogenic Belt (CAOB). In this paper, Magnetotelluric (MT) profile data across the south-eastern CAOB and the northern margin of the NCC are explored to image the two-dimensional resistivity structure of the region. According to the resistivity model, a north-dipping conductive layer to the north of the Xilinhot fault and a south-dipping conductive layer to the south of the Linxi fault are revealed. The two conductors are interpreted as evidence of the late-stage low-angle bidirectional subduction of the Paleo-Asian Ocean, which constrains the northern and southern deep boundaries of the Solonker Suture Zone. Another couple of mantle conductors with opposite dipping angles are revealed under the Solonker Suture Zone and Bainaimiao Belt, which are interpreted as evidence of the early-stage high-angle bidirectional subduction of the Paleo-Asian Ocean. Compared with the results from previously reported MT profiles in this area, the subduction angle becomes more gentle from west to east. The difference of convergence rate between the NCC and the Siberian Craton is considered to be the major cause of the closure difference along the strike. The northern margin of the NCC has a conductive lower crust, which may result from the magma underplating or crust-mantle decoupling, as it is imaged to be connected with the south-dipping conductive layer beneath the Solonker Suture Zone. [ABSTRACT FROM AUTHOR]

To understand the post-orogenic tectonics related to collision between the North China Craton (NCC) and the South China Block (SCB), the Northern Sulu massif is a representative area. It experienced a complex evolution marked by exhumation of ultra-high-pressure metamorphism rocks, migmatization, and alkaline magmatism in the Latest Triassic, and felsic magmatism in the Late Jurassic. In this contribution, we carried out a combined study including structural analysis, anisotropy of magnetic susceptibility (AMS), and gravity survey on the Northern Sulu massif. According to our structural analysis, it is interpreted as an extensional dome, exhibiting dominantly SE-dipping foliations in its east and center and NW-dipping ones closer to its northwestern margin, NW-SE mineral and stretching lineations, and top-to-the-NW kinematics. The Latest Triassic pyroxene syenite has dominantly SE-dipping mesoscopic/magnetic foliations, NW-SE magnetic lineations, and wedge shape at depth, and the Latest Triassic quartz syenite has variable magnetic fabric. Considering geometric relations of plutons and country rocks, the former is a " syn -kinematic" pluton, while the latter post-dates the regional tectonics, constraining the timing of the top-to-the-NW shearing at 220–210 Ma. Compared with the syn-orogenic tectonic events, the Latest Triassic ductile deformation points to a NW-SE extension related to lithospheric delamination. Late Jurassic isotropic monzogranite is characterized by "onion-skin" magnetic foliations with NE-SW trending magnetic lineations, and NE- or SW-ward decrease of thickness at depth. On the basis of regional understanding, we link its emplacement with the Late Jurassic NE-SW extensional tectonics attributed to the oblique subduction of the Paleo-Pacific plate. Such two episodes of crustal extensions with magmatism reformed the crustal architecture of the SE-margin of the NCC, which considerably facilitated stress-transmission from plate-boundary to intraplate during the development of subsequent Late Mesozoic intracontinental deformations. • Recognition of syn - to post-tectonic syenite precisely constrains timing of ductile deformation. • Multidisciplinary study reveals two episodes of extension in Sulu UHP orogen at Mesozoic. • Crustal extension weakening crust helped subsequent intracontinental deformations. [ABSTRACT FROM AUTHOR]

The mantle lithospheric structures beneath the northeastern Tibetan Plateau (NETP) and adjacent areas provide critical information about the role of the mantle lithosphere in the lateral growth of the plateau. In this study, we construct a comprehensive image of the lithospheric structure across the NETP and western North China Craton (NCC) using the S-wave receiver function method based on the dense seismic array of ChinArray II. We detect one or multiple negative conversions at the depth ranging from 80 to 200 km across most of the study region, which is associated with the seismic lithosphere-asthenosphere boundary (LAB) or mid-lithospheric discontinuity (MLD) within the lithospheric mantle. The main features include that the Beishan Block, West Qinling Orogen, and Qilian Orogen present a relatively shallow LAB at a depth range of 120–140 km, while the Longxi Basin and Alashan Block have the similar lithospheric structure with a deep LAB at depth > 150 km and some MLDs within the lithospheric mantle. We find that the Qilian Orogen in the western NETP overlying a thin mantle lithosphere has been significantly elevated, whereas the Longxi Basin in the eastern NETP with a thick mantle lithosphere lacks both high elevations and significant crustal thickening. It implies that the thick mantle lithosphere beneath the eastern NETP and western NCC likely prevents the plateau from invading the Longxi Basin, while the thin mantle lithosphere across the western NETP and Beishan Block favors outward growth of the Qilian Orogen. Our seismic images provide new insights into the lithospheric heterogeneities and their roles in the lateral growth of the Tibetan Plateau. • Comprehensive lithospheric structures across the northeastern Tibetan Plateau are imaged by S receiver functions. • The results show thin mantle lithosphere in the Qilian and West Qinling Orogens and thick one beneath the Longxi Basin. • Lateral growth of the plateau is likely to occur within blocks with weak mantle lithosphere and be inhibited by rigid ones. [ABSTRACT FROM AUTHOR]

Major geophysical elements of the Deniliquin multiple-ring feature, a spatially distinct buried structure in mainland southeast Australia, suggest it represents the deep-seated root zone of a large impact structure from which the upper levels, including the original crater, central uplift and associated breccia, have been eroded. Principal features include (A) a multiple ring total magnetic intensity (TMI) pattern; (B) a central quiet magnetic zone; (C) circular Bouguer gravity patterns; (D) an underlying mantle Moho rise about 10 km shallower than under the adjacent Tasman Orogenic Belt; (E) radial faults associated with magnetic and demagnetized anomalies. The minimum radius of the TMI ring is ~260 km, including a central circular quiet magnetic zone about ~120 km in radius. In the east the feature is faulted against the Early Paleozoic Lachlan Orogenic belt whereas in the west it deflects the northwest and northeast trending Early Cambrian ~525–514 Ma Kanmantoo Group. An interpretation of the Deniliquin multiple-ring feature in terms of an orocline is inconsistent with the discontinuity between the feature and surrounding regional structural trends. Limits on the age of the Deniliquin feature are defined by the onset of the Adelaide fold belt at 514 +/− 5 Ma (Foden et al., 1999) and the ~427–417 Ma age of intrusive Silurian granites. Basement drill cores within the Deniliquin multiple-ring feature show Boehm lamellae but did not reveal shock metamorphic textures. Based on its multiple-ring structure, structural distinction from surrounding regional structural trends, occurrence of a central quiet magnetic zone, an underlying shallower Moho and radial faults associated with magnetic bodies, we suggest the Deniliquin multiple-ring feature may represent the deep seated root zone of a large impact structure. • Geophysical elements of the Deniliquin >500 km diameter-large multiple ring feature in southeast Australia are consistent with those of large impact structures. This includes a symmetrical multiple ring pattern, radial dykes, a central quiet magnetic core and an underlying mantle dome. • The Deniliquin feature likely predates ~428–417 Ma Silurian granites but postdates the 514 ± 4 Ma-old Cambrian Kanmantoo Group. • A near-analogous structure is been reported from the of the deeply eroded basement core of the ~300 km-large Vredefort impact, where shock metamorphic features are restricted. • No direct petrographic shock metamorphic textures were identified to date in drill cores of the Deniliquin feature. However the deep crustal level exposed renders it possible the crater and central uplift containing shock textures have been eroded. [ABSTRACT FROM AUTHOR]

Ever since the Mesozoic era, the eastern segment of the Central Asian Orogenic Belt (CAOB) has been significantly affected by the subduction of the Pacific plate. In order to better understand the subduction effect of the Pacific plate at different distances, we set up 65 magnetotelluric stations to acquire a three-dimensional inversion resistivity structure. The results illustrate that: there are three large-scale high-conductivity anomalies C1, C2 and C3 affecting the crust and mantle of the eastern segment of the Central Asian Orogenic Belt. The high-conductivity anomaly C1 extends from the surface to the asthenosphere and is connected with C2, which exists in the asthenosphere below the Xing'an block. The high-conductivity anomaly C3 under the Songliao block extends downward from the surface to the asthenosphere. We interpret that these anomalies are caused by aqueous fluid and partial melting based on petrophysical analysis. In the light of the high-temperature high-pressure theory, the estimated water content and melting fraction of C3 is considerably higher than that of C2. We infer that the lateral heterogeneity of the fluid-related properties is caused by the variable distance to the Western Pacific subduction zone. The C3 anomaly is located above the stagnant plate and controlled by the medium-distance effects of Pacific plate subduction, which have been influenced by intense dehydration and seriously transforming. The C2 anomaly is located at the end of the stagnant plate and controlled by the long-distance effects of Pacific plate subduction with slight dehydration and transformation. • There exist high conductivity anomalies at crust-mantle scale in the eastern segment of the Central Asian Orogenic Belt. • It is speculated that the underlying cause of high conductivity anomalies is the aqueous fluid and partial melting. • The heterogeneity of fluid-related can be ascribed to the difference in distance of the Pacific plate subduction. [ABSTRACT FROM AUTHOR]

The India-Asia collision processes are under current debate, mainly due to the large variations of the pre-collision position of the southern margin of Asia, in the range of 10–30°N. To resolve this uncertainty, we report new paleomagnetic data of the Xigaze forearc basin sediments from the Zhongba Cuojiangding area. Characteristic remanent magnetizations (ChRMs) were obtained from the upper Cretaceous Qubeiya Formation (Fm) and the early Eocene Jialazi Fm. Both mean directions passed the fold test and also passed the reversal test. An elongation-inclination analysis for all the Jialazi Fm ChRM directions yielded an unflattened mean inclination of 41.6°, with 95% confidence limits between 36.0° and 49.0° (f = 0.76), consistent with the Qubeiya Fm results. The overall mean direction for the Qubeiya Fm is D = 334.8°, I = 42.7°, k = 11.8, α 95 = 6.7°, n = 42 in stratigraphic coordinates, corresponding to a paleolatitude of 24.8°N and a paleopole at 67.1°N, 347.5°E with A 95 = 7.1°. The tilt-corrected mean direction, combined with published data, for the Jialazi Fm is D = 340.5°, I = 41.6°, k = 8.7, α 95 = 5.2°, n = 87, corresponding to a paleolatitude of 23.9°N and a paleopole at 71.6°N, 340.0°E with A 95 = 5.0°. Our updated results indicate a paleolatitude of ~24°N for the Xigaze forearc basin during 70–50 Ma, suggesting that a significant Greater Asia is very unlikely, and strongly supporting a two-stage model for the India-Asia collision with a ~ 55 Ma initial collision of India with an equatorial intra-oceanic arc in the northern hemisphere low latitude followed by the collision between India-plus-arc and Asia in late Eocene. [Display omitted] • The Xigaze forearc basin was located at ~24°N during 70–50 Ma. • The Asian crustal shortenings are 600 ± 800 km (70 Ma) and 700 ± 600 km (50 Ma). • Our new data strongly support a ~ 55 Ma intra-oceanic arc-continent collision. [ABSTRACT FROM AUTHOR]

A high resolution crustal model of the eastern Qinling belt and central North China Craton (central NCC) is obtained along a N–S trending profile (corridor) by joint inversion of surface wave and receiver function. The NCC is one of the oldest cratons on Earth and the Qinling belt is the suture zone between the NCC and South China block (SCB). The Qinling belt is characterized by low crustal velocity (< 3.6 km/s) as well as low bulk Vp/Vs ratio (1.66–1.8), suggesting that the mid- to lower crust is predominantly felsic in composition, which could be the consequence of removal of mafic root by delamination in the past. The quartz-rich hence mechanically weak crust beneath the Qinling belt could be responsible for the strain focusing and significant reactivation since the Cretaceous. Beneath the central NCC, a ~ 10 km thick high-velocity layer (3.9–4.1 km/s) is observed just above the Moho, consistent with the regional high bulk Vp/Vs ratio (> 1.8). The forward gravity modeling supports the presence of a high-density layer (3.05 g/cm 3 ) at the base of the crust beneath the central NCC. We propose that the high velocity in the lowermost crust beneath the central NCC is most likely due to the repeated mafic underplating, which also results in high crustal Vp/Vs ratio and is responsible for the rapid crustal uplift during the late Mesozoic. [ABSTRACT FROM AUTHOR]

Using a simple solution to the heat conduction equation, I show how, at the end of an orogenic event, the relaxation of isotherms from a syn-orogenic advection-dominated geometry to a post-orogenic conduction-dominated geometry leads to the creation of a thick iso-age crustal layer. Subsequent erosion of this layer yields peculiar age-elevation profiles and detrital age distributions that cannot be easily interpreted using traditional techniques. I illustrate these points by using a simple analytical solution of the heat equation as well as a transient, three-dimensional numerical model. I also demonstrate that the age of the end of an orogenic event is so strongly imprinted in the thermochronological record that it erases most of the information pertaining to the orogenic phase itself and the subsequent isostatically-driven exhumation. The concept is used to explain two thermochronological datasets from the Himalayas and demonstrate that their most likely interpretation involves the sudden interruption of extremely fast exhumation accommodated by movement along the South Tibetan Detachment in the Higher Himalayas around 15 Ma. [ABSTRACT FROM AUTHOR]

The Cantabrian orocline is a large structure that bends the Variscan orogen of Western Europe in NW Iberia. The extensively studied kinematics of its core, the foreland of the orogen, indicates that the structure is secondary, i.e. acquired after the formation of the orogenic edifice. However, the extent of the Cantabrian orocline away from its core is under debate. In this paper we study the kinematics of the Cantabrian orocline beyond the foreland. We collected and analyzed samples from the northern and central parts of the Truchas syncline, which provides new data within the hinterland of the orogen in NW Iberia. The analysis of 320 samples shows a late Carboniferous remagnetization with an E to NE declination and shallow downward inclinations. These results suggest a counter-clockwise rotation of ~ 60° and peri-equatorial but still southern hemisphere latitude for Iberia during the uppermost Carboniferous–Early Permian. This rotation fits with the expected kinematic evolution of the Truchas syncline if it indeed was part of the Cantabrian orocline. [ABSTRACT FROM AUTHOR]

We present results of a paleomagnetic study from Carboniferous forearc basin rocks that occur at both limbs of the Texas Orocline (New England Orogen, eastern Australia). Using thermal and alternating field demagnetizations, two remanence components have been isolated from rocks sampled from the Emu Creek terrane, in the eastern limb of the orocline. A middle-temperature Component M is post-folding and was likely acquired during low-temperature oxidation at 65–35 Ma. A high-temperature Component H is pre-folding, but its comparison with the paleomagnetic data from coeval rocks in the northern Tamworth terrane on the other limb of Texas Orocline does not indicate rotations around a vertical axis, as expected from geological data. A likely explanation for this apparent discrepancy is that Component H postdates the oroclinal bending, but predates folding in late stages of the 265–230 Ma Hunter Bowen Orogeny. The post-Kiaman age of Component H is supported by the presence of an alternating paleomagnetic polarity in the studied rocks. A paleomagnetic study of volcanic and volcaniclastic rocks in the Boomi Creek area (northern Tamworth terrane) revealed a stable high-temperature pre-folding characteristic remanence, which is dated to c. 318 Ma using U–Pb zircon geochronology. The new paleopole (37.8°S, 182.7°E, A 95 = 16.2°) is consistent with previously published poles from coeval rocks from the northern Tamworth terrane. The combination of our new paleomagnetic and geochronological data with previously published results allows us to develop a revised kinematic model of the New England Orogen from 340 Ma to 270 Ma, which compared to the previous model, incorporates a different orientation of the northern Tamworth terrane at 340 Ma. [ABSTRACT FROM AUTHOR]

The Taiwan mountain belt is generally thought to develop above a through-going basal thrust confined to within the sedimentary cover of the Eurasian continental margin. Surface geology, magnetotelluric, earthquake hypocenter, and seismic tomography data suggest, however, that crustal levels below this basal thrust are also currently being involved in the deformation. Here, we combine seismic tomography and earthquake hypocenter data to investigate the deformation that is taking place at depth beneath south-central Taiwan. In this paper, we define the basement as any pre-Eocene rifting rocks, and use a P-wave velocity of 5.2 km/s as a reference for the interface between these rocks and their sedimentary cover. We found that beneath the Coastal Plain and the Western Foothills clustering of hypocenters near the basement-cover interface suggests that this interface is acting as a detachment. This detachment is located below the basal thrust proposed from surface geology for this part of the mountain belt. Inherited basement faults appear to determine the geometry of this detachment, and their inversion in the Alishan area result in the development of a basement uplift and a lateral structure in the thrust system above them. However, across the Shuilikeng and the Chaochou faults, earthquake hypocenters define steeply dipping clusters that extend to greater than 20 km depth, above which higher velocity basement rocks are uplifted beneath the Hsuehshan and Central ranges. We interpret these clusters to form a deeply penetrating, east-dipping ramp that joins westward with the detachment at the basement-cover interface. It is not possible to define a basal thrust to the east, beneath the Central Range. [ABSTRACT FROM AUTHOR]

The Curie surface interpreted from magnetic data through spatial frequency domain techniques is used to provide information on the thermal structure of Borborema Province. The Borborema Province is part of the neoproterozoic collision of an orogenic system situated between the São Francisco-Congo and São Luís-West Africa cratons, which formed the Gondwana Supercontinent. The Curie surface of Borborema Province varies from 18 to 59 km, which reveals the complexity in the crustal composition of the study area. The thermal structure shows different crustal blocks separated by the main shear zones, which corroborates the evolution model of allochthonous terranes. The Curie surface signature for the west portion of Pernambuco Shear Zone may indicate processes of mantle serpentinization, once the Curie isotherm is deeper than Mohorovic discontinuity. In this region, the amplitude of Bouguer anomaly decreases, which corroborates long wavelength anomaly observed in the magnetic anomaly. We interpreted this pattern as evidence of the Brasiliano-Pan-Africano's subduction/collision event. Earthquakes in the region are concentrated mainly in shallow Curie surface regions (less resistant crust) and in transition zones between warm and cold blocks. We calculated the horizontal gradient of the Curie depth to emphasize the signature of contact between the thermal blocks. These regions mark possible crustal discontinuities, and have high correlation with orogenic gold occurrence in the study area. [ABSTRACT FROM AUTHOR]

Stratigraphic analyses document climatic and tectonic controls on the filling of a Late Triassic to early Middle Jurassic (T 3 –J 2 ) basin that developed on top of a young orogenic belt in southeastern South China. About 2700 m of Carnian to Bajocian sedimentary rocks is documented in the Meizhou region, Guangdong Province. The Carnian to Rhaetian sequence is characterized by deltaic facies that are succeeded by Hettangian fluvial, shallow marine and volcaniclastic facies, and by Sinemurian to early Toarcian interdistributary bay and floodplain facies. The late Toarcian to Bajocian sequence comprises proximal alluvial to lacustrine facies that changed upwards to fluvial facies. Fossil assemblages indicate that climatic conditions changed from tropical/subtropical warm humid, to temperate humid, and then to hot arid through the Late Triassic to the Middle Jurassic. Climatically induced changes (e.g., in precipitation, vegetation and erosion) exerted a strong influence on sediment supply, whereas tectonics played a dominant role in stratigraphic evolution, accommodation generation, sedimentation pattern and volcanism. Tectonostratigraphic analysis shows that the T 3 –J 2 basin was initiated on an orogenic belt during late-stage orogeny, and evolved into shallow-marine and volcanic environments and then back to terrestrial facies during the post-orogenic stage. This was followed by regional uplift and the development of a basin-and-range province. The order of these events is similar to that of the central Rocky Mountains, western North America during the Palaeogene. The Mesozoic basin of South China and the Eocene basins of the central Rocky Mountains highlight the importance of subduction-related subsidence above young and broad orogens. [ABSTRACT FROM AUTHOR]

The North Patagonian fold-thrust belt (41°–44° S) is characterized by a low topography, reduced crustal thickness and a broad lateral development determined by a broken foreland system in the retroarc zone. This particular structural system has not been fully addressed in terms of the age and mechanisms that built this orogenic segment. Here, new field and seismic evidence of syntectonic strata constrain the timing of the main deformational stages, evaluating the prevailing crustal regime for the different mountain domains through time. Growth strata and progressive unconformities, controlled by extensional or compressive structures, were recognized in volcanic and sedimentary rocks from the cordilleran to the extra-Andean domain. These data were used to construct a balanced cross section, whose deep structure was investigated through a thermomechanical model that characterizes the upper plate rheology. Our results indicate two main compressive stages, interrupted by an extensional relaxation period. The first contractional stage in the mid-Cretaceous inverted Jurassic–Lower Cretaceous half graben systems, reactivating the western Cañadón Asfalto rift border ~ 500 km away from the trench, at a time of arc foreland expansion. For this stage, available thermochronological data reveal forearc cooling episodes, and global tectonic reconstructions indicate mid-ocean ridge collisions against the western edge of an upper plate with rapid trenchward displacement. Widespread synextensional volcanism is recognized throughout the Paleogene during plate reorganization; retroarc Paleocene-–Eocene flare up activity is interpreted as product of a slab rollback, and fore-to-retroarc Oligocene slab/asthenospheric derived products as an expression of enhanced extension. The second stage of mountain growth occurred in Miocene time associated with Nazca Plate subduction, reaching nearly the same amplitude than the first compressive stage. Extensional weakening of the upper plate predating the described contractional stages appears as a necessary condition for abnormal lateral propagation of deformation. [ABSTRACT FROM AUTHOR]

Together with the Araguaia and Brasília belts, the Paraguay belt forms in central Brazil, the Tocantins Province that is one of the largest orogens of western Gondwana. The Corumbá area occupies the site where the northern and southern parts of the Paraguay belt form, together with the Chiquitos-Tucavaca aulacogen (stretching E–W in the adjacent Bolivian territory) an R-R-R basin system opened-filled in the ~ 700/650–540 Ma interval within the Amazon-Rio Apa paleo-continent. The sedimentary (volcanic) rocks of the Jacadigo and Corumbá Groups found around the Corumbá city record part of the Neoproterozoic–Cambrian passive margin precursor of the Paraguay belt. Our pioneer structural analysis reveals that these rocks experienced progressive deformation (phases D 1 –D 2 –D 3 ) and low-grade metamorphism during the Brasiliano Cycle (540–513 Ma). The crystalline basement was also involved, according to structural data and K–Ar ages in the literature. The paleo-passive margin was thickened during the D 1 –D 2 deformation and was lately shortened (D 3 ) in two orthogonal directions, SE–NW (D 3P ) and SW–NE (D 3T ). Developed co-axially and verging to NW, D 1 –D 2 –D 3P structures record the closure of the basin precursor of the Paraguay belt, whereas D 3T structures seem related to the inversion of the aulacogen. Although the tectonic transport to NW, as observed in the Corumbá area, matches the reported transport of Paraguay belt's supracrustal rocks towards the eastern margin of the Rio Apa block and Araguaia belt's rocks towards the Amazon craton, the transport direction is opposite in other parts of the Paraguay belt. Our comprehensive discussion of these facts brings to light profound regional implications. [ABSTRACT FROM AUTHOR]

Receiver functions from a temporary deployment of 25 broadband stations along a north–south transect through Central Australia are used to retrieve crustal and uppermost mantle structural constraints from a combination of different methods. Using H–K stacking as well as receiver function inversion, overall thick crust with significant thickness variation along the profile (40 to ≥ 55 km) is found. Bulk crustal v p / v s values are largely in the felsic to intermediate range, with the southernmost stations on the Gawler Craton exhibiting higher values in excess of 1.8. A common conversion point (CCP) stacking profile shows three major discontinuities of the crust–mantle boundary: (1) a two-sided Moho downwarp beneath the Musgrave Province, which has previously been associated with the Neoproterozoic to early Cambrian Petermann Orogeny, (2) a Moho offset along the Redbank Shear Zone further north attributed to the Middle to Late Paleozoic Alice Springs Orogeny, and (3) another Moho offset further north, located at the boundary between the Davenport and Warramunga Provinces, which has not been imaged before. In all cases, the difference in crustal thickness between the two sides of the offset is > 8–10 km. Unlike the two southern Moho offsets, the northernmost one does not coincide with a prominent gravity anomaly. Its location and the absence of known reactivation events in the region make it likely that it belongs to a Proterozoic suture zone that marks a previously unknown block boundary within the North Australian Craton. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt is a gigantic tectonic collage of numerous accreted terranes. However, its geodynamic evolution has been hotly debated primarily due to incomplete knowledge on the nature of these enigmatic terranes. This work presents new detrital zircon U–Pb and Hf isotopic data to constrain the crustal nature and origin of the Russian Altai, a critical segment of Altai-Mongolian terrane. The youngest zircon 206 Pb/ 238 U ages of 470 Ma constrain that the Terekta Formation, previously envisaged as Precambrian basement, was actually deposited after the Middle Ordovician. As for the three more sedimentary sequences above the Terekta Formation, they have youngest zircon 206 Pb/ 238 U ages of 425 Ma, 440 Ma and 380 Ma, respectively, indicating their depositions likely in the Late Silurian to Devonian. From all analyses, it is noted that many zircon U–Pb ages cluster at ca. 520 Ma and ca. 800 Ma, and these zircons display oscillatory zoning and have subhedral to euhedral morphology, which, collectively, suggests that adjacent Neoproterozoic to Paleozoic igneous rocks were possibly dominant in the sedimentary provenance. Additionally, a few rounded Archean to Mesoproterozoic zircon grains are characterized by complex texture, which are interpreted as recycling materials probably derived from the Tuva–Mongolian microcontinent. Precambrian rocks have not been identified in the Russian Altai, Chinese Altai and Mongolian Altai so far, therefore, Precambrian basement may not exist in the Altai-Mongolian terrane, but this terrane probably represents a large subduction–accretion complex built on the margin of the Tuva–Mongolian microcontinent in the Early Paleozoic. Multiple episodes of ridge–trench interaction may have caused inputs of mantle-derived magmas to trigger partial melting of the newly accreted crustal materials, which contributed to the accretionary complex. During accretionary orogenesis of the CAOB, formation of such subduction–accretion complex is likely ubiquitous, indicating continental crust growth by both lateral accumulation and vertical basaltic injection. [ABSTRACT FROM AUTHOR]

Using Lg-wave Q tomography, we construct a broadband crustal attenuation model for the Middle East. The Q Lg images reveal a relationship between attenuation and geological structures. Strong attenuation is found in the continental collision orogenic belt that extends from the Turkish and Iranian plateau to the Pamir plateau. We investigate the frequency dependence of Q Lg in different geologic formations. The results illustrate that Q Lg values generally increase with increasing frequency but exhibit complex relationships both with frequency and between regions. An average Q Lg value between 0.2 and 2.0 Hz, Q Lg (0.2–2.0 Hz), may be a critical index for crustal attenuation and is used to infer the regional geology. Low-Q Lg anomalies are present in the eastern Turkish plateau and correlate well with low Pn-velocities and Cenozoic volcanic activity, thus indicating possible partial melting within the crust in this region. Very strong attenuation is also observed in central Iran, the Afghanistan block, and the southern Caspian Sea. This in line with the previously observed high crustal temperature, high-conductivity layers, and thick marine sediments in these areas, suggests the high Lg attenuation is caused by abnormally high tectonic and thermal activities. [ABSTRACT FROM AUTHOR]

The Qinling–Dabie–Sulu orogen is the most prominent Phanerozoic orogenic belt in China. The discovery of ultra-high pressure (UHP) minerals in zircon inclusions suggests that the crust was subducted to deeper than 120 km into the mantle and then exhumed to shallow crustal. Recently, low temperature thermochronology has been applied to constrain the final exhumation of Dabie Shan, while there are few studies describing the Cenozoic exhumation history of the Sulu belt. Here we report some (U–Th)/He ages for various lithologies from Sulu Orogenic belt and its northern part-Jiaobei terrane. The single grain He ages range between 18 and 154 Ma, and most of the samples having large intra-sample age scattering. Several reasons such as invisible U/Th-rich inclusions, grain size effect, slow cooling rate, and zonation of parent nuclide or radiation damage effect may account for this dispersion. For all samples, the pattern of the single grain age data exhibits a peak at ~ 45 Ma which is consistent with the borehole fission-track age pattern in adjacent Hefei Basin. Both (U–Th)/He and fission track ages of the Sulu area suggest an enhanced exhumation/cooling in Early-Middle Eocene in the southern part of Tan-Lu fault zone. This enhanced cooling event coincides with rapid subsidence of North China Basin and rapid uplift of its surrounding reliefs, which indicates basin-mountain coupling. This Eocene event is widespread in central China and could be far-field consequence of India–Asia collision. The convergence rate between Pacific Plate and Eurasia decreased substantially during early Tertiary and reached a minimum in Eocene (~ 30–40 mm/yr) while at the same time the collision between India and Asia was completed. Therefore, the Cenozoic exhumation history of the Sulu Orogenic Belt was a combined result of far-field effect of India–Asia collision and declined subduction rate of the Pacific Plate under Eurasia. [ABSTRACT FROM AUTHOR]

Our recent Foliation Intersection Axes (FIAs) data from porphyroblasts in a metapelitic sequence, exposed south of the Indus suture of the NW Himalaya, revealed a fascinating relationship between the trends of three FIA sets versus the plate motion of India since its collision with the Kohistan–Ladakh Arc. The established FIA trend sequence, ESE–WNW (set 1), E–W (set 2) and NNE–SSW (set 3), matches successive vectors of relative India–Asia plate movement between magnetic anomalies 25–22 (55–50 Ma), 21–20 (48–44 Ma) and 13–8 (36–29 Ma), on the premise that FIAs develop normal to the direction of bulk crustal shortening. The correlation allows us to precisely model the pressure (P)–temperature (T) path followed by this portion of the NW Himalayan orogen from 55 to 29 Ma. Representative samples preserving FIA sets in garnet porphyroblasts are modeled in the chemical system MnNCKFMASH using THERMOCALC. A steep continuous P–T path is obtained from garnet porphyroblasts for sample preserving FIA set 1 that brackets metamorphic conditions during early NNE–SSW shortening (anomalies 25–22) between 0.4–0.87 GPa and 495–535 °C (M1 metamorphism). Garnets preserving FIA set 2 revealed 0.46–0.8 GPa and 507–565 °C (M2 metamorphism) during N–S (anomalies 21–20) shortening. Subsequent ESE–WNW shortening parallel to the orogenic arc (anomalies 13–8) peaked at 0.9 to 1 GPa and 595 ± 19 to 618 ± 28 °C (M3 metamorphism) and was followed by high-temperature/low-pressure conditions of 0.8 ± 0.2 GPa at 747 ± 32 °C that accompanied north-side-down decompression (M4 metamorphism) after 29 Ma. The M3 and M4 P–T estimates are based on average P–T conditions of garnet inner rim with the matrix mineral phases, which we suspect may not be in equilibrium due to later reactivation of the matrix foliation. The orthogonal orientation of FIA 1 and the NNE movement of India between anomalies 25 and 22 (55–50 Ma) suggest that the Indian plate collided with the Kohistan–Ladakh Arc around this time. [ABSTRACT FROM AUTHOR]

Tectonic models for the evolution of the Patagonian orogenic curve were evaluated using analog experiments that considered either a rotational or a non-rotational orogenic backstop, combined with a basement promontory on the foreland cratonic margin. Five different kinematic configurations were used, aiming to evaluate the influence of the Río Chico Arc as a rigid obstacle on the evolution of the Fuegian thrust–fold belt. Rotations, strains and displacement fields obtained from each analog experiment were compared with the structural geology known from the Fuegian thrust–fold belt, in order to appraise the tectonic models that are more consistent with the natural structure. The push of a counterclockwise rotational backstop, combined with the buttressing effect of a foreland promontory, seem of major importance in controlling the final structure and map-view shape of the thrust wedge. [ABSTRACT FROM AUTHOR]

The tectonic setting of the southeastern Central Asian Orogenic Belt (CAOB) during the Late Paleozoic has been debated for many years. Provenance analysis of Permo-Carboniferous sedimentary rocks can effectively address this issue. In this study, eight sandstone samples were collected for zircon U–Pb and Lu–Hf isotopic analyses combined with petrographic analysis. Framework petrography and zircon morphology suggest that the samples were from recycled orogen of an igneous origin. Carboniferous rocks, with a significant age peak at 432 Ma and ε Hf (t) values of − 9.0 to 13.6, were mainly derived from Early to Mid-Paleozoic magmatic rocks and deposited in a piedmont zone, namely, the margin of an inland sea. Permian rocks, mostly with age peaks at 445 Ma and/or 280 Ma and ε Hf (t) values of − 25.2 to 11.4, dominantly originated from a pre-existing Early to Mid-Paleozoic magmatic arc and Late Paleozoic igneous rocks. These rocks formed in restricted basins of the piedmont and intermountain zones. Based on zircon spectral discrimination, sedimentary environmental analysis, and previous studies, this study supports the interpretation that the southeastern CAOB entered stages of extension and rifting during the Late Paleozoic. In the end, this study proposes a tectonic-paleogeographic reconstruction to explain the tectonic evolution of the southeastern CAOB and the exhumation–transportation–deposition processes between the basins and ranges developed in this orogen. [ABSTRACT FROM AUTHOR]

The process of flat-slab subduction results in complex deformation of overlying forearcs, yet how this deformation decays with distance away from the zone of underthrusting is not well understood. In south central Alaska, flat-slab subduction of the Yakutat microplate drives shortening and rock uplift in a broad coastal orogenic belt. Defined limits of the zone of underthrusting allow testing how orogenesis responds to the transition from flat-slab to normal subduction. To better understand forearc deformation across this transition, apatite (U–Th)/He low temperature thermochronometry is used to quantify the exhumation history of the Kenai Mountains that are within this transition zone. Measured ages in the northern Kenai Mountains vary from 10–20 Ma and merge with the exhumation pattern in the Chugach Mountains to the northeast, where high exhumation occurs due to flat-slab-related deformation. In the southern Kenai Mountains, however, ages increase to 30–50 Ma across a transition near Seward, Alaska, above the zone from flat-slab to normal subduction. These ages are relatively old in comparison to ages determined in other studies in southern Alaska and suggest minimal exhumation. Furthermore, transitions in topographic expression of the coastal orogen also occur at the margin of Yakutat underthrusting. These observations suggest that either deformation associated with flat-slab subduction requires tens of kilometers to decay with distance away from the zone of underthrusting, or that orogenesis in the Kenai Mountains is driven by a distinct tectonic cause. A potential driver of deformation is underplating of thick sediments, specifically the Surveyor Submarine Fan, along the Aleutian Megathrust, analogous to the tectonic mechanism responsible for the emergence of the Kodiak Island forearc. If correct, this may represent a recent tectonic transition in the region, given the minimal exhumation of the rugged Kenai Mountains despite the presence of an erosion-conducive glacial climate. [ABSTRACT FROM AUTHOR]

Early Paleogene granitoids in Southern Lhasa subterrane have been widely investigated and many petrogenesis and geodynamic models have been proposed in the past few years. However, contemporaneous granitoids in the Motuo tectono-magmatic belt, southeast Lhasa terrane, are still limitedly studied. Here we present the petrology, zircon U–Pb geochronology, whole-rock geochemistry, and Sr–Nd–Hf isotope data of the Damu and 52 K quartz–monzonite in the Motuo area. LA-ICP-MS U–Pb zircon dating shows that they have magma crystallization ages of 49 and 69 Ma, respectively. The Damu quartz–monzonite (SiO 2 = 63.76–68.33 wt.%) is high-K calc-alkaline (K 2 O = 2.54–4.02 wt.% with K 2 O/Na 2 O = 0.59–1.09) and metaluminous to weakly peraluminous (A/CNK = 0.99–1.07). The 52 K quartz–monzonite (SiO 2 = 61.12–66.12 wt.%) shows slightly higher K 2 O contents (3.80–5.28 wt.% with K 2 O/Na 2 O = 1.03–1.45) and metaluminous series (A/CNK = 0.96–1.00). The analyzed samples are characterized by high Ba (850–2573 ppm), Sr (534–986 ppm) contents, and fractionated REE patterns ((La/Yb) N = 22–72 and (Sm/Yb) N = 4.55–8.24). These geochemical features are comparable with those of high Ba–Sr granite. They display weakly evolved Sr–Nd–Hf compositions (whole-rock ( 87 Sr/ 86 Sr) 0 = 0.7068 to 0.7086, ε Nd ( t ) = − 4.20 to − 3.41, and zircon ε Hf ( t ) = − 5.2 to − 0.9). Geochemical and Sr–Nd–Hf isotopic data reflect that the Damu and 52 K quartz–monzonite represent residual magma from AFC processes of lithospheric mantle-derived mafic melts. The over-thickened lower crust in the eastern Lhasa terrane had been delaminated during ca. 83–70 Ma, which led to the replacement of ancient lithospheric mantle by the juvenile lithospheric mantle. The juvenile mantle wedge in the study area was suspected to be metasomatized by melts that were derived from the foundering arc root, rather than the subducted sediments. Thus, the early Paleogene high Ba–Sr magmas from the SE Lhasa terrane may provide evidence for recycling of continental lithosphere by density destruction. [ABSTRACT FROM AUTHOR]

The Andean orogenic belt, located in the Central Andes “Pampean flat-slab” segment in northern Chile (27–29°S), is composed of two major tectonic regions: the Coastal Cordillera and the Frontal Cordillera. To understand their internal tectonic styles, history of growth and the shortening absorbed by the upper crustal structure of this segment, we combined regional geological mapping data, new ages obtained from radiometric U–Pb dating, and a semibalanced and restored cross-section 225.18 km in length. The results as shown in the previous Mesozoic extensional fault systems, established in northern Chile by the Gondwana breakup, have played a fundamental role in the orogenic buildup. The central structure is characterized by an asymmetric basin (Upper Cretaceous–Paleocene) confined by a doubly vergent fault system composed of inverted faults related to the edges of the Mesozoic Chañarcillo and Lautaro Basins. The U–Pb geochronological data obtained from synorogenic volcano-sedimentary deposits and the angular unconformities recorded between the Cenozoic geological units have revealed that the compressive deformation in this segment started at around ~ 80 Ma by tectonic inversion in the eastern Coastal Cordillera and western Frontal Cordillera, however, the presence of Paleocene and Miocene synorogenic successions at the footwall of the basement reverse faults of the Frontal Cordillera suggests a migration of Andean deformation from the west to the east during the Paleocene–Miocene by propagation of ramps involving inherited basement highs. The pre-compression restoration makes it possible to estimate 40.94 km of minimum shortening, concentrated by inversion anticlines and fault-controlled basement highs across the Frontal Cordillera. [ABSTRACT FROM AUTHOR]

Fold–thrust belts along convergent margins around the world host major ore deposits. The origin of such ore deposits is commonly episodic and so are the temporal and spatial variations in deformation styles in these fold–thrust belts. Here we focus on the Marañón Fold–Thrust Belt (MFTB) of the Peruvian Andes, and demonstrate a link between the spatio-temporal distribution of ore deposits and thick-skinned tectonics. We present low-temperature thermochronology results from the MFTB that document the uplift/exhumation history and timing of thick-skinned tectonics and vergence reversal. Our results suggest that the thermal history of the MFTB involved two discrete intervals of opposed-vergence, large-scale crustal deformation since the Late Cretaceous. An early interval, at ~ 80–20 Ma, was associated with folding and east-vergent thin-skinned tectonics, and was followed by west-vergent thick-skinned deformation at ~ 20–0 Ma. Furthermore, our findings suggest that thick-skinned contraction was coincident with increased focusing of mineralising fluids and ore deposition in the MFTB during the early Miocene, and in the mid-Miocene both mineralisation and deformation were enhanced by subduction of the Nazca Ridge underneath the South American Plate. [ABSTRACT FROM AUTHOR]

The Tasmanides of eastern Australia record much of the Phanerozoic tectonic development of the retreating Pacific-Australia plate boundary and are an oft-cited example of an orogen that has undergone “tectonic mode switching.” To begin to constrain the timing of exhumation of basement rocks that are now exposed in portions of the NE Tasmanides, we measured apatite and zircon (U–Th)/He ages from the Thomson Orogen and overlying Paleozoic strata in the back-arc of the New England Orogen in NE Australia. Zircon (U–Th)/He ages from basement samples (including those recovered from boreholes at depths of up to 1.1 km) are characterized by large inter- and intra-sample variability and range from approximately 180 Ma (Early Jurassic) to 375 Ma (Late Devonian). (U–Th)/He zircon ages from several individual samples are negatively correlated with effective uranium (eU), a pattern that is also true of the dataset as a whole, suggesting that variations in U and Th zoning and radiation damage are partially responsible for the age variability. The oldest zircon (U–Th)/He cooling ages coincide with the formation of regionally extensive Late Devonian–early Carboniferous back-arc basins, suggesting that Late Devonian extension played a significant role in exhumation of parts of the northern Thomson Orogen. Apatite (U–Th)/He ages from a basement sample and a late Permian sandstone in the overlying Bowen Basin, which are also marked by intra-sample variability and age–eU correlations, span from the Early Cretaceous through Oligocene, in general agreement with previous apatite fission track data. In conjunction with observations of key geologic relationships and prior K–Ar and 40 Ar/ 39 Ar data, our results suggest four overall phases in the thermal history of the northern Thomson Orogen: (1) Cambrian–early Silurian metamorphism during the Delamerian and Benambran Orogenies; (2) protracted cooling during the Late Devonian through mid-Permian that likely resulted from extensional exhumation; (3) Permian–Triassic reheating during burial beneath thick sedimentary basins; and (4) Cretaceous and Paleogene cooling during uplift and erosion. [ABSTRACT FROM AUTHOR]

The origin and tectonic setting of Precambrian sequences in the Central Asian Orogenic Belt (CAOB) have been debated due to a lack of high resolution geochronological data. Answering this question is essential for the understanding of the tectonic framework and Precambrian evolution of the blocks within the CAOB. Here we reported LA-ICP-MS detrital zircon U–Pb ages and in-situ Hf isotopic data for Neoproterozoic sedimentary cover in the northern Yili Block, an important component of the CAOB, in order to provide information on possible provenance and regional tectonic evolution. A total of 271 concordant U–Pb zircon ages from Neoproterozoic sedimentary cover in the northern Yili Block define three major age populations of 1900–1400 Ma, 1300–1150 Ma and 700–580 Ma, which are quite different from cratons and microcontinents involved in the CAOB. Although it is not completely consistent with the local basement ages, an autochthonous provenance interpretation is more suitable. Some zircon grains show significant old Hf model ages (T DM C ; 3.9–2.4 Ga) and reveal continental crust as old as Paleoarchean probably existed. Continuous Mesoproterozoic zircon age populations exhibit large variations in the εHf(t) ratios, suggesting the long-time involvement of both reworked ancient crust and juvenile material. Similar Mesoproterozoic evolution pattern is identified in many continental terranes involved in the CAOB that surround the Tarim Craton. Based on our analysis and published research, we postulate that the northern Yili Block, together with Chinese Central Tianshan, Kyrgyz North Tianshan and some other microcontinents surrounding the Tarim Craton, once constituted the continental margin of the Tarim Craton in the Mesoproterozoic, formed by long-lived accretionary processes. Most of the late Neoproterozoic zircons exhibit significant positive εHf(t) ratios, suggesting the addition of juvenile crust. It is consistent with the tectonic event related to the East Africa Orogen in the Arabian-Nubian Shield and the northern Tarim Craton, indicating the affinity between them in Gondwana. [ABSTRACT FROM AUTHOR]

The core of the Alpine orogen in the Eastern Alps (Tauern Window) experienced a change from orogen-normal shortening and post-nappe doming to predominantly orogen-parallel extension and tectonic unroofing during late Oligocene to Miocene northward indentation of the Adriatic Microplate. A new 147 Sm/ 144 Nd isochron age of 25.7 ± 0.9 Ma on a garnet-bearing assemblage from the lowest nappe complex forming a dome in the eastern part of the Tauern Window indicates that high temperatures related to post-nappe Barrovian-type metamorphism overlapped in time with the onset of doming. New 87 Rb/ 87 Sr biotite ages from this same complex combined with previously published 87 Rb/ 87 Sr white mica ages suggest that doming and exhumation began no later than 28 Ma immediately in front of indenting Austroalpine crustal blocks, then migrated laterally to the ESE during rapid exhumation and orogen-parallel stretching beginning at about 23 Ma. Rapid cooling ended at approximately 17 Ma in the footwall of the Katschberg Normal Fault, which delimits the eastern margin of the Tauern Window. A similar pattern of migrating doming, orogen-parallel extension and cooling is recognized in the western part of the Tauern Window, where rapid exhumation began at about 20 Ma, some 2–3 Ma later than in the eastern part. This difference in the onset of rapid exhumation as well as the overall migration of doming from the center to the ends of the Tauern Window are attributed to fragmentation of the aforementioned Austroalpine blocks along the leading edge of the main Adriatic indenter (Southern Alps) as this indenter advanced to the north. [ABSTRACT FROM AUTHOR]

Zircon U–Pb dating and whole-rock geochemical data for Carboniferous–Permian (meta-) sedimentary sequences, igneous rocks, and Precambrian amphibolite in the eastern Xing-Meng Orogenic Belt (XMOB) were used to constrain the final stage evolution and the position of closure of the Paleo-Asian Ocean (PAO). Detrital zircons from Late Paleozoic strata range in age from Archean to Late Paleozoic, with major age groups at ~ 1.0–0.7 Ga and ~ 0.5–0.25 Ga in the northern part and at ~ 2.7–2.5 Ga, ~ 2.1–1.8 Ga, and ~ 0.5–0.25 Ga in the southern part of the XMOB. Striking changes in zircon age distribution patterns indicate inputs to these strata were separated by the Paleo-Asian Ocean (PAO) in the Late Paleozoic. The PAO closed along the Solonker–Linxi suture. The Late Paleozoic formation ages (~ 346 Ma, ~ 303 Ma, and ~ 269 Ma) of the igneous rocks with arc-like geochemical features south to the PAO, together with previously published data on the regional igneous rocks and ophiolites, indicate double-side subduction of the PAO in the Late Paleozoic. [ABSTRACT FROM AUTHOR]