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The Qilian Orogenic belt is one of the typical orogenic belts globally and a natural laboratory for studying plate tectonics. Many researchers have studied the ophiolite and high pressure and ultra-high pressure metamorphic rocks in the Qilian orogen and obtained valuable achievements. However, a hot debate exists on the basement property, the distribution of ophiolite, and the boundaries of tectonic units. Large-scale high-precision aeromagnetic surveys have recently been conducted in the Qilian Orogenic belt and adjacent areas. In this study, we are trying to analysis the tectonic framework of the Qilian Orogen using 1:500, 000 aeromagnetic data. The results provide geophysical perspectives for studying the structural framework and deformation of this area. According to the aeromagnetic ΔT anomaly map, the central and Southern Qilian have the same magnetic anomaly feature that noticeably differs from the North Qilian Orogenic belt and the Qaidam Block. This result indicates that the central and Southern Qilian have a unified magnetic basement and differ from the North Qilian orogenic belt and Qaidam Block. The map shows the distribution of ophiolite in the North Qilian orogenic belt. Linear magnetic anomalies represent the ophiolites because the mafic–ultramafic rocks usually have high magnetic susceptibility. The ophiolite belts are continuously distributed in the western part of North Qilian orogenic belt and have a large scale. However, the scale of the ophiolite belt and the outcropping of mafic–ultramafic rocks reduces when they pass through Qilian County to the east. The results indicate differences in the evolution process between the eastern and western parts of North Qilian, with Qilian County as the transition zone. This study also systematically defines the geophysical boundaries of the Qaidam Block, Qilian Block, North Qilian Orogenic belt, and Alxa block. It is proposed that the sinistral displacement of the Altun Fault is adjusted and absorbed by the series of NE-trending faults in the Qilian orogen and merge into the Longshoushan–Gushi Fault. The extension of the North Qilian Orogenic belt is strengthened by the neotectonics movement along the shearing direction, which separated the North Qilian Orogenic belt into several segments and formed a series of northeast-trending faults. [ABSTRACT FROM AUTHOR]

Interpretation and inversion of P-T (Pressure-Temperature) paths of high-pressure (HP) and ultrahigh-pressure (UHP) metamorphic rocks are critical to understanding the subduction and exhumation histories of an orogen. The Sulu orogen constitutes the eastern part of the Dabie-Sulu orogen, in which, HP metamorphic rocks are relatively poorly as studied compared to the well-documented UHP metamorphic rocks. This study presents the P-T paths of HP eclogites constructed by petrography, mineral chemistry, and pseudosection modelling by using the GeoPS software within the MnNCFMASKHTO (Mn-CaO-FeO-MgO-Al2O3-SiO2-K2O-H2O-TiO2-O2) system. Sample 19LR70–1 mainly consists of omphacite, garnet, quartz, minor rutile, ilmenite, and amphibole. Sample 19LR71–1 is mainly composed of omphacite, garnet, kyanite, and accessory minerals of rutile and amphibole. These two eclogite samples recorded clockwise P-T paths with peak P-T conditions of P ≥ 21.3 kbar, T ≥ 755°C and P ≥ 23.0 kbar, T ≥ 871°C, respectively. Well-correlated U-Pb ages and trace element data show that the protoliths of eclogites were 655–699 Ma and 676–754 Ma, the metamorphic ages were 212–232 Ma, and the time of partial melting were 221–225 Ma. Combined with regional geological data, we conjectured that before 240 Ma, the South China plate was subducted to the North China craton; subsequently, at 240–220 Ma, HP eclogite facies metamorphism occurred at a depth of 60–70 km. This was followed by the exhumation of these HP metamorphic rocks, coupled with concurrent partial melting, around 220–200 Ma. [ABSTRACT FROM AUTHOR]

High‐temperature–low‐pressure metamorphism is commonly associated with intermediate to felsic magmatism in continental orogenic belts. The heat budgets and transfer mechanisms responsible for such elevated temperatures and partial melting of the upper crust are uncertain. The Trois Seigneurs massif, French Pyrenees, preserves a structurally continuous record of Variscan high‐temperature–low‐pressure metamorphism through a sequence of upper‐to‐mid‐crustal Paleozoic metasedimentary rocks. Conventional thermobarometry and phase equilibria calculations show that metamorphic conditions span ~2.5 kbar, 575°C to suprasolidus conditions of ~6 kbar, 700°C. Peak temperatures depend strongly on depth: temperature gradients of 50–60°C/km are present through the uppermost 12 km of the section; deeper portions (12–20 km) define restricted temperature conditions of ~650–700°C. The lowest‐grade metamorphic rocks preserve the largest spread in monazite 206Pb*/238U dates, from c. 325–285 Ma, while the spread in dates is restricted to c. 305–290 Ma in the highest‐grade rocks. Within this spread, each sample yields a well‐defined population of monazite 206Pb*/238U dates with peaks at c. 305 Ma in the andalusite schists, 295 Ma in the sillimanite schists, and 300 Ma in the migmatite sample. Monazite trace‐element compositions capture a systematic change with decreasing date and increasing metamorphic grade, including a more negative Eu‐anomaly and decreasing Sr concentrations, consistent with co‐crystallizing feldspar; increasing HREE and Y contents, consistent with xenotime breakdown; and decreasing Th/U, reflecting increasing U content during breakdown of inherited zircon. Zircon rims from a granite unit that formed via partial melting of the Paleozoic sedimentary package yields a 206Pb/238U‐207Pb/235U concordia age of 304.1 ± 3.73 Ma. These rims have trace‐element compositions reflecting cogenetic apatite and zircon growth during granite formation. Zircon from a calc‐alkaline granodiorite intrusion preserves a 40 Ma record of melt‐related activity in the lower crust that preceded the regional thermal climax. We interpret these petrochronological data to show that the Trois Seigneurs field gradient including andalusite schist and biotite granite samples represents a genuine geotherm through Variscan orogenic crust during the regional thermal climax at 305 Ma. When combined with constraints from other Pyrenean massifs, the form of the geotherm is consistent with a thermal scenario in which heat is advected to the upper crust by intermediate‐composition magmas generated in the lower crust. A simple thermal model for this process indicates that anatexis in the upper crust may plausibly occur within 10 Ma of the initiation of the lower‐crustal melting. Such a thermal scenario, however, requires focusing of melt through a fertile lower crust and an elevated Moho heat flux. We suggest that this process may have controlled the attainment of high‐temperature–low‐pressure metamorphic conditions along the Variscan belt and may currently be operating in zones of post‐orogenic continental extension. [ABSTRACT FROM AUTHOR]

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SE Anatolia is witnessing the final stage of the Wilson Cycle, where a continental collision between the Tauride–Anatolide block and Arabian platform occurred, and a 1.5 km Eastern Tauride mountain chain formed. We present new low-temperature thermochronology (LTT) ages, including eight apatite fission track (AFT) and seven apatite and zircon U-Th-Sm/He (AHe, ZHe) ages, for the metamorphic rocks from the Nappe Zone of the Southeast Anatolian Orogenic Belt. The ZHe ages vary from 51.2 ± 0.7 Ma to 30.4 ± 0.6 Ma, the AFT ages range from 33.1 ± 1.6 Ma to 18.1 ± 0.9 Ma, and the AHe ages range from 23.6 ± 2.5 Ma to 6 ± 1.9 Ma. The LTT data show a continuous slow uplift of the region. However, the thermal modeling results suggest an Eocene and middle–late Miocene fast uplift of the region. Similar to our results, the LTT studies along the SAOB show that the vertical movements initiated during the Eocene period have continued in a steady-state regime to recent times. The Eocene epoch is identified by arc–back-arc setting in the region, whereas the Miocene epoch is marked by the continental collision. Within this tectonic framework, vertical movements on the overriding plate are controlled by both extensional and compressional tectonics. The LTT data obtained along the SAOB show fingerprints of thrust propagation from north to south. [ABSTRACT FROM AUTHOR]

Granulites and eclogites are useful for revealing the thermal and tectonic evolution of orogens. Early Palaeozoic granulites and associated eclogites in the East Kunlun Orogenic Belt (EKOB) display contrasting metamorphic age. Such asynchronous granulite–eclogite associations have rarely been reported, and the geological significance of their existence remains to be further explored. In this study, petrological and geochronological techniques were used to investigate two felsic and two mafic granulites collected from the Qingshuiquan area in the eastern section of the EKOB. These rocks record similar P–T paths, which are characterized by a peak stage within suprasolidus and high‐pressure (HP) granulite facies conditions (750–832°C and 10.1–12.0 kbar), followed by an initial decompression and cooling stage to subsolidus conditions (600–748°C and 6.5–8.6 kbar), and then a stage of further retrogression under greenschist facies conditions. The protoliths to these granulites are of volcanic and sedimentary origin and suggested to be a component of the continental basement unit. Metamorphic P–T paths indicate that these rocks experienced peak metamorphism at a depth of ~40 km, then cooling and uplift to a depth of ~25 km, and eventually experienced low‐grade retrogression at shallow crustal levels. Cathodoluminescence images and compositional data demonstrate that the zircons in these rocks are of metamorphic origin and they crystallized at or near peak conditions. SIMS U–Pb dating of representative zircon grains yield concordant metamorphic ages of c. 490–520 Ma, with a peak value of 505 Ma on the probability density curve. These ages are similar to other 480–530 Ma ages typically retrieved from EKOB granulites and associated rocks, and are markedly older than the 400–450 Ma ages retrieved from eclogites and their host rocks. The HP granulites and eclogites of the EKOB do not show overprinting relationships. Such asynchronous characteristics imply that the two rock types formed in distinct tectonic settings and at different stages of a protracted subduction–collision process. The studied granulites are suggested to have formed in the root of a continental arc during a stage of Proto‐Tethys Ocean subduction. The formation of the eclogites could be attributed to subsequent deep continental subduction. [ABSTRACT FROM AUTHOR]

Exhumed (ultra)high-pressure ([U]HP) metamorphic rocks are markers of paleosubduction zones and can provide crucial implications for the geodynamic evolution of subduction-exhumation. A variety of (U)HP metamorphic rocks from many collisional orogens have commonly documented a lowpressure high-temperature overprint, which appears to indicate a pervasive geodynamic process behind (U)HP metamorphic rock exhumation. A good case study of garnet amphibolite and associated garnet-biotite gneiss with an unambiguous low-pressure high-temperature overprint in the Xixia-Xiaguan area of the North Qinling Orogen, central China, provides a significant opportunity to uncover this geodynamic process. A detailed study of petrography, mineral chemistry, and phase equilibria modeling suggests that the investigated garnet amphibolite and garnet-biotite gneiss have jointly experienced multistage exhumation processes with near-isothermal decompression from the (U)HP eclogite facies (26.8-29.0 kbar/740-775 °C) to the mediumpressure (MP) amphibolite facies (8.7-10.0 kbar/740-775 °C), subsequent remarkable near-isobaric heating to the low-pressure (LP) granulite facies (6.8-8.2 kbar/832-835 °C), followed by final decompression and cooling to the LP amphibolite facies (5.8-6.8 kbar/740-757 °C). U-Pb age dating of zircons from the garnet amphibolite and garnetbiotite gneiss yielded metamorphic ages of ca. 500 Ma, 450 Ma, and 400 Ma, which we consider to represent (U)HP eclogite-facies, LP granulite-facies, and late LP amphibolite-facies metamorphism, respectively. According to the regional geology and the metamorphic history we have determined, this multistage exhumation process of twostep exhumation stages delimited by a phase of LP near-isobaric heating was associated with slab rollback. Accordingly, we propose a tectonic model of exhumation driven by slab rollback for the geodynamic evolution of (U)HP metamorphic rock exhumation in the North Qinling Orogen. Additionally, a combination of previous studies and our new results suggests that exhumation driven by slab rollback appears to be a fundamental mechanism for the (U)HP metamorphic rock exhumation within collisional orogens. [ABSTRACT FROM AUTHOR]

Sparse eclogite exposure in accretionaryto-collisional orogens cannot only reveal the sites of ancient subduction zones and plate boundaries, but also elucidate the multistage tectonic evolution in the Wilson cycle. The southern part of the Dora-Maira Massif in the Western Alps is well known for its ultrahigh-pressure (UHP) rocks and contains small occurrences of petrographically distinct types of eclogite. Due to the lack of detailed geochronological and geochemical data on these rocks, the nature of their protolith and related geodynamic setting has remained unknown. In the current study, 33 samples from 13 localities were studied by wholerock major- and trace-element analysis, and a selection of the samples were studied using Sr-Nd-Hf isotopes, as well as high-resolution elemental mapping and U-Pb geochronology of zircon. According to macroscopic appearance, petrography, chemical composition, and principal-component analysis of multielements, two major types are distinguished. Light-colored eclogite is phengite-rich, commonly foliated, bears kyanite and quartz/coesite, shows relatively high MgO, K2O, SiO2, εNd(t) (-2.2 to +1.4), and εHf(t) (+3.5 to +7), with a protolith geochemically similar to an enriched-type mid-oceanic-ridge basalt (E-MORB). Dark eclogite generally is massive, rutile-rich, shows higher values of Ti, Fe, P, Nb, and Zr, εNd(t) values between -2.8 and -0.8, εHf(t) values between -6.1 and -3.2, with an oceanic island basalt (OIB)-type protolith composition. Magmatic zircon cores, which are characterized by steep heavy rare earth element (HREE) patterns and negative Eu anomalies, yield consistent protolith ages of ca. 253-252 Ma in both eclogite types. Metamorphic zircon domains with flat HREE patterns and insignificant Eu anomalies yield a younger mean age of ca. 34 Ma, which is the age commonly assigned to eclogite-facies UHP metamorphism. Considering the various geochemical signatures of E-MORB-to OIB-like eclogites and the regional tectonic evolution, their protolith is best explained as rocks, which crystallized from rift-related basaltic magma, associated with the break-up of the Pangea Supercontinent that eventually resulted in the birth of the Piemonte-Liguria Ocean (Alpine Tethys Ocean) between the future Eurasia and Adria plates. Therefore, the UHP eclogites in the Dora-Maira Massif likely fingerprint a multi-stage tectonic evolution from divergent (continental extension, rifting) to convergent (subduction zone) plate boundary, corresponding to the beginning and end of a Wilson cycle. Incidentally, they reveal that mafic rocks in the Alpine basement units may not be polymetamorphic, but may actually consist of post-Variscan products that underwent only Alpine metamorphism. [ABSTRACT FROM AUTHOR]

Detrital zircon provenance analysis plays a key role in reconstructions of past tectonic and sedimentary environments. However, non-unique (or even erroneous) interpretations can be introduced due to the inherent limitations of both zircon provenance analysis (fertility bias, recycling) and those of single-proxy provenance systems in general. Apatite crystallizes in a wider range of lithologies than zircon, and can thus facilitate more detailed source reconstructions. In this study, detrital apatite analysis of Cryogenian to Ordovician sandstones in the Cathaysia Block was carried out in comparison with detrital zircon data for a better understanding of the source-sink process on the northern margin of Gondwana. In contrast to the abundant Grenvillian (1300-900 Ma) detrital zircons of igneous origin, detrital apatites show major Pan-African (650-500 Ma) age peaks that are mostly derived from metamorphic rocks (52%-72%). The apatite data show that the Cathaysia Block mainly received detritus from western Australia and India during the late Neoproterozoic to early Paleozoic, with much lower affinities to East Antarctica and the terranes of Iran-Turkey. Provenance variations include a shift with time in the major age populations from ca. 900 Ma to 600 Ma with a decrease in metamorphic apatite (from 72% to 52% of all grains) in the late Cryogenian, an increase in high-grade metamorphic apatite (from 27% to 56%) in the late Ediacaran-Cambrian, and an increase in igneous apatite (from 33% to 45% of all grains) in the Early Ordovician. In contrast, detrital zircon data could only reveal the source change in the late Ediacaran. These provenance switches were likely caused by the unroofing of Pan-African orogens (640-490 Ma) and subsequent erosion of their exposed cores, due to the rapid uplift of source rocks formed in the Pan-African orogens during the Gondwana assembly. [ABSTRACT FROM AUTHOR]

Observations over the last few decades from a number of orogenic systems have highlighted the possible importance of tectonic exhumation, i.e., ductile thinning and normal faulting, in exhuming rocks once buried in high-pressure conditions. Taiwan is one of the few active orogens in the world where rocks that once experienced high-pressure metamorphism (> 50 km) are exposed at the Earth's surface, providing a natural laboratory for advancing our understanding of exhumation processes. We integrate previously published studies of the Taiwan orogen with new structural, geochronological, and fluid inclusion microthermometry data to argue that tectonic extrusion and structural thinning played a critical role in exhuming the metamorphic core of the orogen until very recently, ca. 0.7 Ma. We propose a two-stage process for exhuming the high-pressure metamorphic rocks of the Yuli Belt: an initial stage where exhumation is driven primarily by pressure gradients in a subduction channel and a second stage that is initiated as an orogen-parallel regional-scale strike-slip zone, the Tailuko shear zone, is offset by an orogen-normal strike-slip zone. The offset generates an extensional bend that is filled with extruding high-pressure rocks as the upper crust is structurally thinned. Evidence for tectonic thinning comes primarily from a low-angle penetrative foliation that records significant vertical shortening and a suite of sub-vertical late-stage, mineral-filled veins. Isotopic dating indicates that the second stage started ca. 2.4–3.1 Ma and ended at ca. 0.7 Ma when the northern Backbone Range orocline started to form. We propose the low-angle foliation formed in the footwall of a regional-scale extensional shear zone that rooted to the east, beneath the forearc. Combined tectonic and erosional processes may have limited the topographic growth of the orogen from ~3.0 to < 1.0 Ma. [ABSTRACT FROM AUTHOR]

The Eastern Taurides, which form the imbrication and nappe zone in the northernmost part of the Arabian platform, are located within the Southeastern Anatolian Orogenic Belt. In the present study, spectral enhancement methods such as band ratioing, minimum noise fraction (MNF), relative band depth (RBD), and supervised classification were applied to ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) images of metamorphic massifs, ophiolites, and sedimentary rocks outcropping in the western part of the Eastern Taurides (Göksun, Afşin, and Ekinözü regions). With these methods, the aim was to distinguish geological units from each other accurately. In the study area, arid climatic conditions with relatively poor vegetation, allowing for precise visual interpretations, play a significant role. Vegetation and water bodies were also masked before these procedures. In the Göksun, Afşin, and Ekinözü regions, metamorphic rocks of phyllite, schist, and gneiss types, which underwent metamorphism during the Upper Cretaceous and Eocene periods, are observed. The geologically dominant minerals in these rocks include silica, mica (muscovite, phengite, biotite), chlorite (clinochlore, chamosite), kaolinite, and carbonates (calcite, dolomite). These rocks are accompanied by ophiolitic, volcanic/volcano-sedimentary, and plutonic igneous rocks. Due to geological events during the closure of the Neotethys Ocean and continental collision in the area, it became evident that the lithological diversity from various rock groups was reflected in the ASTER images, in addition to field observations. Image processing analyses applied to the ASTER sensor images, rich in short-wave infrared (SWIR) and thermal infrared (TIR) bands on the Terra platform, revealed distributions of clay, sulfate, carbonate, iron oxide, and silica minerals. The highest geological differentiation potential was observed through ASTER 643 (RGB) and ASTER 13,12,10 (RGB) false-color composites, as well as ASTER 456 (RGB) minimum noise fraction (MNF) analyses and, especially, relative band depth processes. Relative band depth processes were employed to identify epidote-chlorite-amphibole, calcite-chlorite-amphibole, alunite-kaolinitepyrophyllite, muscovite, and silica minerals. The application of these processes revealed lithologies that strongly feature these minerals. Specifically, the goal was to differentiate rock units containing kaolinite, muscovite, phengite, chlorite, and epidote minerals belonging to AlOH and FeOH groups and elucidate their compositions. Moreover, rocks containing primarily quartz and feldspar were distinguished using ASTER TIR bands. The obtained data revealed that mineralogical and corresponding lithological spatial distributions, as depicted by ASTER images, could play a crucial role in geological mapping, particularly in regions where mapping is challenging due to geographical conditions. [ABSTRACT FROM AUTHOR]

The Qinling Orogenic Belt (QOB) is a composite orogenic belt located between the North China Craton (NCC) and the South China Block (SCB), and formed as a result of multiple episodes of collision and accretion. Although the tectonic history of the QOB has been extensively studied and reviewed, the evolution of the belt remains controversial. This contribution mainly reviews the geological, geochemical, and geochronological data of all the Early Palaeozoic intrusive and volcanic rocks of different genetic types in different tectonic units of the QOB and investigates their tectonic implications, together with the records of sediments, fossils and metamorphic rocks, to synthesize a new model for the Early Palaeozoic tectonic framework of the QOB. The QOB contains four discrete tectonic units (from north to south): the southern margin of the NCC, the North Qinling Terrain (NQT), the South Qinling Terrain (SQT), and the northern margin of the SCB. The Kuanping Ocean (represented by the Kuanping suture between the NQT and NCC) was a long-lived ocean rather than a backarc basin. Southward subduction of the Kuanping oceanic slab probably had begun before the Neoproterozoic and continued until the closure of the oceanic basin during the Early Palaeozoic. The subsequent retreat of the subducting slab caused the exhumation of deeply subducted arc volcanic rocks, forming high-pressure – ultrahigh-pressure metamorphic rocks at 500 My and the Erlangping backarc basin later. The closure of this basin and the subsequent collision between the NQT and NCC occurred at ca. 440 Ma. The Shangdan Ocean was a proto-Tethyan Ocean that had existed as early as the Neoproterozoic, the oceanic slab eventually underwent northward subduction towards the NQT at ca. 520 Ma, and this ocean closed by ca. 420 Ma. Marginal rifting and tectonic extension within the northern margin of the SCB formed the Mianlue oceanic basin during the Early Devonian. The complex interactions between the four discrete tectonic units within the QOB also led to the multiple-phase Early Palaeozoic metamorphic events, with the closure of the Kuanping, Erlangping, and Shangdan oceanic basins resulting in the HP – UHP and granulite- and amphibolite-facies metamorphism occurred at ca. 500, ca. 440, and 420 Ma, respectively. [ABSTRACT FROM AUTHOR]

The Nianzi granite unit, which includes the Nianzi, Xiaolianghou and Xiawopu granitic intrusions, is a significant component of the northern part of the North China Craton (NCC) and is situated in the Yanshan fold and thrust belt (YFTB). However, there is still debate regarding the tectonic evolutionary history of the YFTB during the late Permian to Triassic period, specifically regarding the timing of subduction and collision between the NCC and the Paleo‐Asian Ocean. The Nianzi granite unit exhibits unique petrological, geochronological and geochemical signatures that shed light on the tectonic evolutionary history of the YFTB. This study presents detailed petrology, whole‐rock geochemistry, together with Sr‐Nd isotopic, zircon U‐Pb dating and Lu‐Hf isotopic data of the granites within the Nianzi granite unit. Our findings demonstrate that the granites primarily consist of subhedral K‐feldspar, plagioclase, quartz, minor biotite and hornblende, with accessory titanite, apatite, magnetite and zircon. Zircon U‐Pb dating indicates that the Xiaolianghou granite was emplaced at 247.5 ± 0.62 Ma. Additionally, the adakitic characteristics of the Nianzi, Xiawopu and Xiaolianghou granitic intrusions, such as high Sr and Ba contents and high ratios of Sr/Y and (La/Yb)N, combined with negative Sr‐Nd and Lu‐Hf isotopes (87Sr/86Sr)i = 0.705681–0.7057433, εNd(t) = –21.98 to –20.97, zircon εHf(t) = –20.26 to –9.92), as well as the I‐type granite features of high SiO2, Na2O and K2O/Na2O ratios, enriched Rb, K, Sr and Ba, along with depleted Th, U, Nb, Ta, P and Ti, suggest that the Nianzi granitic unit was mainly derived from the partial melting of a thickened lower crust containing hydrous, calc‐alkaline to high‐K calc‐alkaline, mafic to intermediate metamorphic rocks. In light of these parameters, we further integrate our data with previous studies and conclude that the Nianzi granitic unit was generated in a post‐collisional extensional environment during the Early Triassic. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt was characterized by a long-lived accretionary history from Neoproterozoic to Paleozoic, followed by a collisional phase of orogeny in the latest Paleozoic with the closure of the Paleo-Asian Ocean. However, Ni-Cu sulfide mineralization associated with mantle-derived mafic magmas in the Central Asian Orogenic Belt was relatively short-lived. Thus, the coherence between the protracted accretionary and collisional history of the Central Asian Orogenic Belt and the transient Ni-Cu sulfide-bearing mafic magmatism is difficult to understand. We investigated both Ni-Cu sulfidebearing and sulfide-barren mafic intrusions along a major suture zone of the Irtysh Shear Zone within the Central Asian Orogenic Belt to understand the origin of shortlived Ni-Cu sulfide mineralization in the context of the collision of two arc systems of the Chinese Altai and the East Junggar regions. Zircon U-Pb dating results for the Ni-Cu sulfide-bearing mafic intrusions show that they were only emplaced briefly from 290 Ma to 280 Ma after subduction terminated (ca. 312 Ma), substantially earlier than Ni-Cu sulfide-barren mafic intrusions (ca. 274--271 Ma). Zircons from all Ni-Cu sulfide-bearing/barren mafic intrusions yield arithmetic mean δ18O values ranging from 6.0 to 7.4‰, higher than the typical mantle value (~5.3‰), which indicates their derivation from a metasomatized mantle with inherited subduction signatures. The δ11B values of the rocks from these intrusions range from -17.2‰ to -2.3‰, significantly lower than those of typical volcanic arcs (up to +18‰), which suggests that the metasomatic components in the mantle source were dominated by sediment melts rather than fluids. The pressure calculated using amphibole thermobarometry shows that the parental magmas of the Ni-Cu sulfide-bearing mafic intrusions were emplaced shallower than those of Ni-Cu sulfide-barren mafic intrusions. This is supported by the fact that the country rocks of the Ni-Cu sulfidebearing mafic intrusions are shallow crustal lithologies of sedimentary rocks, whereas the country rocks of the barren intrusions are relatively deeper crustal lithologies of high-grade metamorphic rocks and granites. Olivine from the Ni-Cu sulfide-barren intrusions has forsterite (Fo) contents ranging from 51.1 mol% to 76.2 mol% and Ni from 196 ppm to 1312 ppm. These values are much lower than those of the Ni-Cu sulfide-bearing intrusions (Fo = 72.6-79.4 mol%; Ni = 1022-1925 ppm), which indicates that the parental magmas of the barren intrusions may have experienced extensive olivine crystallization. Notably, the emplacement of the Ni-Cu sulfide-bearing mafic intrusions (290-280 Ma) coincidently overlapped with a transient period of orogen-parallel extension (ca. 295-280 Ma) in response to the collision of the Chinese Altai and East Junggar. Syn-collisional extension may lead to the rapid ascent and emplacement of mantle-derived mafic magmas at a shallower crustal level, preventing significant loss of Ni from olivine crystallization at depths, and thus providing metal-rich mafic magmas for potential Ni-Cu sulfide mineralization. Our results highlight that syn-collisional extension is an essential geodynamic mechanism that controls the emplacement of Ni-Cu sulfide-bearing mafic intrusions in orogenic belts. [ABSTRACT FROM AUTHOR]

Metamorphic rocks encode invaluable information on the burial and exhumation history of rocks that is critical to our understanding of orogens. In this work, zircon U--Pb dating, pseudosection, and garnet zoning modeling were performed on samples from the North Altyn area, SE Tarim Craton, NW China. Zircon U--Pb geochronological data indicate that the peak metamorphism occurred at ca. 2.0 Ga. Pseudosection isopleth thermobarometry using garnet growth zoning of the sample from the northern part of the North Altyn area (Kalatashtagh) reveals a decompression and heating path to a peak temperature of 735 °C and 0.74 GPa under the equilibrium crystallization model. The preservation of growth zoning under high temperature requires relatively rapid cooling. In contrast, garnet from the southern part of the North Altyn area (Aktashtagh) preserves diffusion zoning. Metamorphic peak occurs at 670-735 °C and 0.67-0.73 GPa, which suggests a high dT/dP-type metamorphism. Diffusion zoning modeling suggests an extremely slow cooling rate of 1-5 °C/m.y., which indicates prolonged (~100 m.y.) crustal residence time at high temperature. This requires a long-term heat supply, most likely from radiogenic heat from buried sediments or heat conducted from the asthenosphere. The high dT/dP and slow cooling rate, combined with extensive crustal anatexis from previous studies, indicate that the late Paleoproterozoic North Altyn Orogen is a long-lived hot orogen rather than a subduction--accretionary complex. We propose a tectonic model that involves a ca. 2.1-2.0 Ga arc--back-arc system in the SE Tarim Craton. The back-arc basin was subsequently closed by northward underthrusting due to arc--arc/ continental collision at ca. 2.0-1.95 Ga during the integration of the Tarim Craton into the Columbia/Nuna supercontinent. [ABSTRACT FROM AUTHOR]

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Through detailed drill-core description, petrography, cathodoluminescence imaging, and geochemistry analysis, sedimentary deposits with a high content of volcanogenic components (27.6%) were discovered in the Shanxi Formation of the Daniudi Gas Field, Ordos Basin. The volcanogenic components include volcanogenic quartz, lava fragments (dominated by rhyolite fragments), tuff fragments, and tuffaceous matrix. In addition, at least two volcanic ash layers were discovered. Although the metamorphic rocks of the Precambrian succession in the ancient land of Yin Mountain are usually considered the primary source of the Shanxi formation, it is most likely that the volcanogenic components were derived from intermediate-acid volcanic materials that accumulated in the Daqingshan area during the Late Carboniferous to Early Permian. Those volcanogenic components are mainly transported by flowing water rather than by air from origin to basin. In addition, the accumulation of volcanic materials in the Daqingshan area was controlled by volcanic eruptions occurring solely in this area, rather than by the Inner Mongolia Orogenic Belt. Those volcanic eruptions were related to the southward subduction of the Paleo-Asian Ocean Plate beneath the northern margin of the North China Plate in the Late Carboniferous to Early Permian. The active continental margin related to the subduction of the Paleo-Asian Ocean Plate lasted at least until the Early Permian, and the closure of the Paleo-Asian Ocean must have occurred later than the Early Permian. [ABSTRACT FROM AUTHOR]

The China Central Orogenic System (CCOS), extending in an east-west direction in the middle part of China, is composed of the Early Paleozoic Altyn-North Qilian-North Qaidam-East Kunlun-North Qinling-North Tongbai orogens in the west and the Late Paleozoic to Early Mesozoic South Tongbai-Hong'an-Dabie-Sulu orogens in the east. They were produced by oceanic subduction and continental subduction/collision during the closure of the Proto-Tethys and the Paleo-Tethys oceans, respectively. Different types of metamorphic rocks with various ages are extensively exposed in these orogens, and they were produced at different geothermal gradients in different stages during the tectonic evolution of convergent continental margins, making them ideal targets to reconstruct the spatiotemporal evolution of the Eastern Tethys tectonic domain. In this article, an integrated study of metamorphic temperature (T)-pressure (P)-time (t) records is presented for metamorphic rocks along the CCOS, aiming to ascertain the change of metamorphic T/P ratios in both time and space, and then shed light on the tectonic evolution of the East Tethys tectonic domain in association with the thermal state change of convergent continental margins. The results indicate that despite the difference in metamorphic ages, metamorphic rocks in different orogens show a common trend with clockwise P-T-t paths. With respect to plate convergence for subduction and collision, regional metamorphism is categorized into three stages: (1) an early convergent stage, corresponding to low T/P Alpine-type blueschist- to eclogite-facies high-P to ultrahigh-P metamorphism; (2) a later convergent stage, corresponding to the medium T/P Barrovian-type medium-P amphibolite to high-P granulite-facies metamorphism; and (3) a post-convergent stage, corresponding to the high T/P Buchan-type low-P amphibolite to MP granulite-facies metamorphism. Nonetheless, a few metamorphic rocks only record a two-sage metamorphic evolution, with an early Barrovian-type high-P granulite-facies metamorphism and a late Buchan-type low-P granulite-facies metamorphic overprinting. In modern convergent plate margins, Alpine-type metamorphism mainly occurs in the stages of oceanic subduction and continental collision, Barrovian-type metamorphism takes pace in both stages of crustal thickening during continental hard collision and slab exhumation when continental subduction zones have evolved from compressional to extensional regimes, and Buchan-type metamorphism occurs in intracontinental rifting stage after the plate convergence. Therefore, the tectonic evolution of convergent continental margins can be reconstructed by combining metamorphic T/P ratios with their corresponding metamorphic facies series and metamorphic timing of metamorphic rocks. Based on the reported metamorphic rocks of different types and ages along the CCOS, it appears that the continental subduction/collision occurred at 500–490 Ma in the Altyn-North Qinling-North Tongbai orogens but 450–430 Ma in the North Qaidam-East Kunlun orogens, and the intracontinental rifting occurred at 460–450 Ma in the Altyn-North Qinling-North Tongbai orogens but 410–400 Ma in the North Qaidam-East Kunlun orogens, respectively, in the western Proto-Tethys domain. For the eastern Paleo-Tethys domain, in contrast, the continental subduction/collision occurred at 250–220 Ma and post-collisional intracontinental rifting occurred at 140–120 Ma. Furthermore, metamorphic evolution from low T/P ratios in the subduction/collision stage to high T/P ratios in the intracontinental rifting stage needs 40–60 Myr in the Proto-Tethys domain but about 110 Myr in the Paleo-Tethys domain. For the two different orogenic domains, therefore, the convergent continental margins underwent a common tectonic evolution from warm collision/cold subduction to hot rifting, which starts from continental subduction/collision characterized by the formation of medium-P amphibolite to high-P granulite facies series or high-P to ultrahigh-P eclogite facies series in compressional regimes, through exhumation of the deeply subducted crustal rocks, and terminates with intracontinental rifting featured by high-T to ultrahigh-T granulite facies series in extensional regimes. [ABSTRACT FROM AUTHOR]

Geological, mineralogical, and petrological observations are reported for hornfels-like fine-grained granular mafic rocks in the Early Paleozoic Olkhon collisional orogen (West Baikal area, Russia). The rocks are composed of orthopyroxene, clinopyroxene, amphibole, plagioclase, and ilmenite; some samples also contain olivine, phlogopite, spinel, and titanomagnetite (Opx+Cpx+Amp+Pl+Ilm±Ol±Bt±Spl±Ti-Mag). There are three occurrences of these rocks in the area: a 500 m × 1000 m field in the Shirokaya Valley, another occurrence within the Tazheran Massif (a complex of igneous and metamorphic rocks), and dismembered dikes on the southern margin of the Birkhin gabbro intrusion. The Shirokaya field is located between two 500 Ma intrusions of the Birkhin gabbro; the Tazheran occurrence coexists with syenite, including nepheline syenite, subalkaline gabbro, and marble protrusions; and the dismembered dikes coexist with carbonates and display progressive alteration of dolerite through typical granular varieties. The dikes associated with granite and marble veins mark a part of a large arc-shaped shear zone that traverses the whole intrusive body produced by rotation of a rigid gabbro block during the peak of tectonic deformation at 470–460 Ma. All three occurrences of the hornfels-like rocks lack any evident source of heat that would be responsible for the thermal alteration of the igneous protolith. We hypothesize that the precursor, subvolcanic dolerite, may have undergone autometamorphism maintained by self-generated heat. Mafic magma intruded during high-rate strike–slip faulting, which caused rapid recrystallization of magmatic minerals and produced the observed metamorphic structures. Proceeding from the controversy in the formation mechanisms, with a heat source required for hornfels but lacking from the sampled occurrences of hornfels-like rocks, we suggest identifying the latter as beerbachite, though the term has mostly fallen into disuse. The reason is that the Olkhon rocks we study have a mineralogy, structure, and texture that are perfectly identical to those of beerbachites described in publications from the first half of the 20th century. [ABSTRACT FROM AUTHOR]

On the southwestern margin of the North Patagonian Massif (Argentina), there is a NW–SE trending belt consisting of igneous and metamorphic rocks that is named the Central Patagonian Igneous Metamorphic Belt. It defines the boundary between the mentioned massif and southern Patagonia (including the Deseado Massif). It is debatable whether this belt belongs to an orogen generated by accretion or collision and whether it was created in a single event or over the course of several events. Paleogeographic reconstructions were conducted to answer this query, confirming that there are tectonic processes involved in two events: the Chanic (Devonian) and the Gondwanan (late Carboniferous–early Permian) events. They show a movement of South America toward the SW during which an accretionary orogen was built during the Chanic event between ca. 400 Ma and ca. 360 Ma. Later, the paleogeographic reconstructions show an abrupt change in the movement of South America; it is proposed that due to this movement, the previously built orogen collapsed between ca. 360 Ma and ca. 330 Ma. During the Gondwanan event, the subduction surrounding Pangea in the Patagonian belt caused plutonic emplacement in the already-existing orogen structures and paleogeographic reconstructions depict South America with a movement toward the northeast, which involves a displacement due to a slab pull from the northern Paleotethys Ocean boundary. It is further supported that lateral displacement between Gondwana domains brought forth by this slab pull is what led to the assembly between the North Patagonian Massif and southern Patagonia. [ABSTRACT FROM AUTHOR]

The NE‐trending Jiangnan orogenic belt has experienced multi‐tectonic episodes since the Mesozoic separates the Yangtze Block in the north‐west from the Cathaysia Block in the south‐east. The Taqian–Fuchun thrust zone in north‐east Jiangxi Province is located in the eastern Jiangnan orogenic belt. It is considered as an essential unit to understand the geometry, kinematics and dynamics of the Mesozoic nappe structures in the eastern Jiangnan orogenic belt and an ideal region to reveal the Mesozoic tectonic evolution in South China. Here, we present new detailed structural data coupled with zircon U–Pb and apatite fission‐track dating studies, establishing a four‐stage deformation history and describing the geometry, kinematics, ages and dynamic background. The Middle–Late Triassic NW–SE compression event (D1, 243–226 Ma) is mainly characterized by regional angular unconformity between the Lower and Upper Triassic and asymmetric folding of the underlying strata. The associated regional NW–SE shortening was related to the intercontinental collision. The Middle–Late Jurassic NW–SE compression event (D2, 175–160 Ma) is characterized by the angular unconformity between the Middle Jurassic and Cretaceous and the SE‐vergent imbricate nappe structures. The shortening has been associated with the NW‐ward subduction of the Paleo‐Pacific Plate. The Late Jurassic–Cretaceous NW–SE extension event (D3, 160–67 Ma) includes the transition stage from compression to extension (160–145 Ma) and the intensive extension stage (145–67 Ma). The former is characterized by the development of the extensional detachment structures and intermediate‐acid magmatism, while the latter is characterized by the development of Cretaceous extensional sedimentary basins and A‐type granites. This extension was correlated to the slab roll‐back of the Paleo‐Pacific Plate. The Paleocene–Eocene compression event (D4, 67–35 Ma) is manifested by the thrusting of metamorphic rocks in the Shuangqiaoshan Group to the Cretaceous red beds. This shortening possibly originated from the collision between the India and Eurasian Plates. This study provides new constraints on the Mesozoic structural style and establish a reliable geochronological framework of the Mesozoic tectonic evolutions of the eastern Jiangnan orogenic belt. [ABSTRACT FROM AUTHOR]

Linte region, located within the Adamawa-Yade domain of the Central African Fold Belt (CAFB), is associated with the Pan-African orogeny in Cameroon. Magmatic (granular texture and suborientation of euhedral to subhedral feldspar crystals), sub-magmatic (intragranular fractures filled with quartz), and mostly solid-state (internal deformation, exsolution, and dynamic and static recrystallization) microstructures indicate that magmatic and metamorphic rocks of the Linte area were subjected to analogous tectonic manifestations during the Pan-African orogeny. Magmatic, sub-magmatic, and solid-state microstructural analyses combined with the existing age record reveal three phases of local deformation, namely Dn, Dn+1, and Dn+2, which can be correlated with regional D1 to D4 deformation phases of the CAFB. The Dn (ca. 660–600 Ma) marks the crystallization phase accompanied by magmatic and sub-magmatic microstructures. It is related to the regional D1-D2 deformation. The Dn+1 (ca. 600 Ma) represents a compressive tectonic setting related to the regional D3. The Dn+2 (ca. 598 Ma), initiated during D3, represents a transpressive tectonic combined with brittle deformation, and marked by sinistral and dextral shearings episodes, grading into the regional D4 stage. Collectively, microstructures recorded in the Linte igneous rocks can be correlated with the regional tectonic events, including crustal thickening, and successively sinistral wrench and regional dextral shear movements during the Pan-African orogeny in Cameroon. [ABSTRACT FROM AUTHOR]

Accretionary and collisional orogeny are often accompanied by the disturbance of the geothermal gradient, leading to high-temperature metamorphism. High-temperature metamorphic rocks are significant in their ability to help the reconstruction of the thermal histories of orogenic belts. The Tianshan Orogenic Belt, at the southwest margin of the Central Asian Orogenic Belt, is a record of the long-term subduction–collision–post-collision orogenic process that has taken place in the Phanerozoic Eon. Here, we report the discovery of mafic granulites in the Muzhaerte area, SW Tianshan. Petrographic observation reveals that the mafic granulites underwent two metamorphic stages. The peak mineral assemblage of the first stage is dominated by clinopyroxene + orthopyroxene + plagioclase + quartz + hornblende (hb1) ± biotite, and the post-peak mineral assemblage of the second stage is dominated by clinopyroxene + plagioclase + quartz + hornblende (hb2) + biotite. The calculated results obtained from the two-pyroxene thermobarometers and the Al-in-hornblende barometer for the mafic granulites indicate that the metamorphic conditions of mafic granulites are 760–860 °C, <0.39–0.41 Gpa. The mafic granulites recorded a high-grade granulite facies thermal metamorphic event with the highest temperature limit currently recorded in the Central Tianshan Block. [ABSTRACT FROM AUTHOR]

Melt inclusions (MIs) in high‐temperature metamorphic rocks provide a unique window into crustal anatexis in collisional orogenic belts and have been widely used to characterize compositions of anatectic melts as well as melting mechanisms. In this study, MIs hosted by peritectic garnet were for the first time identified in an Al2SiO5‐free graywacke‐type paragneiss from the Namche Barwa Complex, the Eastern Himalaya, Southeast Tibet. These MIs occur as nanogranites in the rims of porphyroblastic garnet, exhibit negative crystal shapes with an average diameter of ~12 μm and consist of a mineral assemblage of biotite + quartz + plagioclase + K‐feldspar ± muscovite. Re‐homogenization experiments of these nanogranites were conducted at a pressure of 1.5 GPa and temperatures of 800°C, 850°C and 900°C and produced homogeneous glasses at 850°C. The homogenized glasses are strongly peraluminous and calc‐alkalic in composition, with 66.43–71.31 wt.% SiO2, 12.64–15.06 wt.% Al2O3, high alkaline (5.41–7.22 wt.%) and low ferromagnesian (2.72–4.46 wt.%) contents. They are lower in silica and CaO but higher in K2O compared with MI produced by fluid‐present melting of metasedimentary rocks, thus indicating fluid‐absent melting. These glasses are also characterized by enrichment of large ion lithophile elements (particularly Cs and Rb), depletion of Ba and Sr, low contents of light rare earth elements (3.6 to 33.7 ppm), high Rb/Sr ratios (6.19–37.3) and low Nb/Ta ratios (2.55–18.7). In combination with phase equilibrium modelling, these compositional features suggest that a sequential dehydration melting of muscovite and biotite was responsible for the production of MI during prograde metamorphism of the studied paragneiss. By compiling MI data published in the literature, we show that dehydration melting of metasedimentary rocks from the Himalayan orogen can produce initial melts with various peraluminous and granitic compositions. [ABSTRACT FROM AUTHOR]

The Eastern Pontides Orogenic Belt (EPOB), geographically corresponding to the northeastern part of Turkey hosts several different types of mineralizations that are closely related to Late Mesozoic-Early Cenozoic arc magmatism. Of these, Zarani gold mineralization, which is located in the southern part of the EPOB occurs as quartz-carbonate veins/veinlets within the Pulur metamorphic massif of Paleozoic age. Mineral textures indicate low-temperature vein-type mineralization. Gold mainly occurs in quartz and pyrite. The presence of calcite, dolomite, and sericite in the mineralization indicates near neutral pH conditions of ore-forming fluid. Geochemical analyses of chlorites in the quartz-carbonate veins reveal a temperature of ore formation at 140-297 °C, which is compatible with those obtained from fluid inclusions in the mineralized quartz (i.e. 132-226 °C). The average salinity value obtained from fluid inclusions is 4.32% NaCl equiv. O and H isotope values range from -6.03? to +1.47? and from -60? to -119?, respectively, indicating a mixture of magmatic and meteoric fluids. Mixing is also evidenced by the XFe analytical data of hydrothermal chlorites associated with ore-forming gangue minerals. Gold precipitation in Zarani mineralization is caused by boiling. The occurrence of mineralization within quartz-carbonate vein/veinlets in metamorphic host rocks, the mineral paragenesis with near-neutral pH conditions of the ore-forming low salinity fluids and the H-O isotopic data imply that the Zarani gold mineralization is an orogenic type epithermal mineralization that may be related to deeply buried Early Cenozoic felsic intrusions, produced by subduction-induced processes in the southern part of the EPOB. [ABSTRACT FROM AUTHOR]

The Yanshan intraplate tectonic belt is a tectonic-active area in the central part of the North China Craton that has undergone long-term orogenic evolution. Detailed studies on magmatic activity and metamorphism of this belt are significant for restoring its orogenic thermal evolution process. The Fangshan pluton in the Zhoukoudian area within this tectonic belt is a product of the late Mesozoic Yanshan event. However, there is a lack of detailed research on the metamorphic evolution history of the ancient terrane surrounding the Fangshan pluton subjected to contact thermal metamorphism. To further constrain the metamorphic P–T evolution of contact metamorphism associated with the Fangshan pluton, we collected rock samples in the andalusite–biotite contact metamorphic zone of the Fangshan pluton, and conducted petrographic investigations, geochemical and mineral composition analysis, and phase equilibrium modeling. The phase equilibrium modeling in the MnO–Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–O system indicates that the peak mineral assemblages of andalusite–biotite schists are pl + q + mu + bi + and ± kfs + ilm + mt, formed at 550 to 610 °C, 1 to 3.5 kbar, and the peak mineral assemblage of garnet–andalusite–cordierite–biotite schists is gt + pl + q + bi + and + cord + ilm + mt, formed at 580 to 620 °C, 1.5 to 2.1 kbar. Therefore, we believe that the rocks in the andalusite biotite contact metamorphic zone of the Fangshan pluton underwent low pressure and medium temperature metamorphism, with the peak metamorphic conditions of about 550–610 °C, <3.5 kbar. The results show that the rocks in contact with the thermal metamorphic zone were rapidly heated by the heat released by the Fangshan pluton, and after reaching the peak metamorphic temperature, they were cooled down simultaneously with the cooling of the rock mass, defined in a nearly isobaric P–T trajectory. [ABSTRACT FROM AUTHOR]

The Central Qilian terrane (CQT) of the northern Tibetan Plateau played a key role in the tectonic evolution of the Proto‐Tethyan Ocean in the Tethysides, but its formation and tectonic attribution have been hotly debated. Here, we report the discovery of eclogites and HP mafic granulites in the Beidahe Complex of the western CQT. These occur as blocks of various sizes within a sequence of metavolcanic–sedimentary rocks, exhibiting typical a 'block‐in‐matrix' and thrust imbrication structure. The eclogite facies metamorphic rocks preserve distinct mineral assemblages and textures corresponding to prograde, peak, and retrograde metamorphism. By combining phase equilibrium modelling with SHRIMP and LA‐ICPMS U–Pb dating of metamorphic zircon, sphene, and rutile, the Late Neoproterozoic–Cambrian (c. 553–516 Ma) eclogite facies peak with low thermal gradients of 10–14°C/km, Cambrian (c. 515–506 Ma) post‐peak decompression and Ordovician (c. 495–455 Ma) cooling histories for these metabasic rocks have been restored. These constitute hairpin‐type clockwise pressure–temperature–time (P–T–t) paths depicting in detail the sequence of deep subduction and subsequent exhumation in Central Qilian during the Late Neoproterozoic to Early Palaeozoic. Our new findings suggest that the CQT represents a Japan‐type arc‐accretionary system that formed as a result of the North Qilian oceanic plate, one of the major branches of the Proto‐Tethys Ocean, being subducted southward. Eclogites in the Beidahe Complex in western CQT offer the earliest (c. 553 Ma) metamorphic record of subduction in the Qilian orogen, indicating that the North Qilian Ocean commenced subducting southward prior to the Late Neoproterozoic. [ABSTRACT FROM AUTHOR]

The Tethys domain preserves one of the largest continent‐continent collisional orogenic belts on Earth. This belt can be divided into the Proterozoic to Palaeozoic Proto‐Tethyan orogenic belt, Late Palaeozoic to Triassic Palaeo‐Tethyan orogenic belt and Triassic to Cenozoic Meso‐ and Neo‐Tethyan orogenic belts. The Tethyan metallogenic domain, representing one of the three major metallogenic domains in the world, extends more than 10,000 km from east to west and has developed world‐class ore belts, such as the South‐east Asia tin ore belt, Sanjiang metallogenic belt in South‐west China, Gangdese–Pakistan–Iran porphyry copper belt and South‐east Europe epithermal gold belt. The geology of the Tethys domain has been studied for more than 100 years and many important advances have been made recently, although scientific issues remain controversial. This thematic section of Geological Journal contains 10 articles focusing on the formation of rocks and ore deposits, including petrology and geochemistry of magmatic, metamorphic and sedimentary rocks, and the formation mechanism of mineral deposits in the Eastern Tethyan Realm. These articles reflect new progress in related studies and provide important reference for future studies. [ABSTRACT FROM AUTHOR]

The Bayan Har Basin is an important part of the Tethys tectonic in the Tibet Plateau. There are various conjectures regarding the basement and tectonic attributes of the Bayan Har Basin. Based on the aeromagnetic anomaly characteristics in the Bayan Har Basin, the structural units and fault system are derived, and the basement composition and structural attributes are discussed in this paper. We draw the following conclusions: (1) The Bayan Har Basin and its adjacent regions can be divided into five magnetic structural units, consisting of the southern Tarim Block, the Qiangtang Block, the western Yangtze Block, the Qinling–Qiliang–Kunlun Orogenic Belt and the Bayan Har Basin. (2) The Muztagh–Kunlun–A'nyêmaqên suture zone and the Xijir Ulan–Yushu–Jinsha River suture zone are the basic frameworks of the north–south division of the basin. (3) The basement in the eastern Bayan Har Basin is composed of Proterozoic metamorphic rocks, and the basement in the western and central basin is composed of Meso–Neoproterozoic metamorphic rocks. (4) The Triassic tectonic attribute of the Bayan Har Basin may be foreland basin. [ABSTRACT FROM AUTHOR]

In western Greece is the Pindos Foreland Basin, a geological depression that contains approximately 2500 m of mainly Upper Eocene to Lower Oligocene submarine fans deposits. Despite the extensive stratigraphic and structural research that has defined the basin as a foreland basin that developed adjacent to Pindos Orogen, the impact of orogenic history and erosion on sedimentation has not been evaluated. This study investigates the origin and tectonic setting of the central Pindos Foreland Basin using new provenance data. Petrographic and geochemical analyses suggest that the succession was primarily sourced by sedimentary, felsic, and intermediate igneous, and low-grade metamorphic source rocks. The geochemical analysis reveals that the sediments are immature and have undergone little to moderate weathering, and low degrees of sediment recycling and sorting. A secondary mafic source with high Cr and Ni contents and high Cr/V ratios. The provenance data indicate that Pindos Orogen represents the source region and agree with the existing sedimentological and palaeocurrent research. The Pindos sedimentary and Pelagonian volcano-sedimentary units, mixed with a mafic source (Pindos ophiolitic units) and low grade metamorphics produce the observed chemical and petrographic variance. Multidimensional discrimination diagrams suggest sediment sources from a collisional setting and confirm the active continental edge setting. The provenance data display an up-section increase in lithic fragments, recording the growing history of the Pindos orogen and the gradual exhumation of the source regions. This study offers an example of the sedimentary provenance trend in an evolving pro foreland basin. [ABSTRACT FROM AUTHOR]

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The past 40 years have been a golden age for eclogite studies, supported by an ever wider range of instrumentation and enhanced computational capabilities, linked with ongoing developments in thermobarometry and geochronology. During this time, we have made robust estimates of pressure–temperature (P – T) conditions; determined ages related to the prograde, metamorphic peak and retrograde stages; and calculated time-integrated rates of cooling and exhumation for eclogites and related rocks, including blueschists, from orogenic belts worldwide. Improvements to single mineral thermometers and new developments in elastic barometry using inclusions of one mineral in another (e.g. quartz and/or zircon in garnet), coupled with ongoing innovations in petrochronology and diffusion modelling, presage a new age for eclogite studies in which detailed quantification of metamorphic conditions and timescales will be linked to an improved understanding of processes at all scales. Since the turn of the century, numerical modelling of subduction zone and rock exhumation processes has become increasingly important. As a result, subduction and exhumation are quite well understood, but the volume of continental crust subducted to and returned from mantle conditions and the amount lost to the mantle are largely unknown. We have generated sufficient data to investigate the spatiotemporal distribution of metamorphism and secular change but not without controversy in relation to the rare occurrence of orogenic eclogites and the absence of blueschists prior to the late Neoproterozoic and the emergence of plate tectonics on Earth. Since the turn of the century, the assumption that metamorphic pressure is lithostatic has come under increasing scrutiny. Whether local variations in stress extrapolate to the crustal scale and, if so, whether the magnitude of the calculated deviations from lithostatic pressure can be generated and sustained in mechanically heterogeneous rock units remains contentious. Could the paradigm of subduction of continental lithosphere to mantle depths be simply an artefact of the lithostatic assumption? Fluid cycling in subduction zones and understanding the role of fluids in the generation of intermediate-depth earthquakes remain important topics of current research. Dry (H 2 O-absent) conditions are unlikely around the peak of ultrahigh-pressure (UHP) metamorphism or during exhumation, due to dehydroxylation of nominally anhydrous minerals and breakdown of hydrous minerals at P – T conditions in the realm of supercritical fluid and hydrous melt. Indeed, the presence of melt may be necessary to facilitate the exhumation of HP and UHP tectonometamorphic rock units. Finally, our ability to interrogate inclusions in superdeep diamonds should lead to a better understanding of how the deep interior and surface are linked in the context of Earth as a fully coupled system. [ABSTRACT FROM AUTHOR]

The formation ages and tectonic features of the Bulunkuole Complex (BKC) is critical for understanding the geological evolution of the western section of the West Kunlun Orogenic Belt (WKOB), and they are also critical for understanding the metallogenic background of the Taxkorgan Iron Belt. In this paper, we report new geochemical and in situ zircon U–Pb isotopes data for the most southwestern iron-bearing formation of the BKC. The petrography and sedimentation ages of the BKC reveal that the main part of the BKC was emplaced in the Early to Late Cambrian period as a giant accretionary wedge formed during the Proto-Tethys Ocean south-southwestward subduction. The high-pressure metamorphic rocks located at the margin of the Kangxiwa Fault should be further disintegrated from the Cambrian BKC to form a Triassic accretionary complex. Geochemical characteristics indicate that the metasedimentary rocks of the Cambrian BKC derived predominantly from the regional contemporary intermediate to felsic source rocks, and deposited in the fore-arc basin. Provenance studies further demonstrate that the detrital materials were mainly sourced from the Gondwana-affinity terranes, Mazar Terrane as well as the volcanic and magmatic rocks produced during the Tethys subduction. The metamorphism of the Cambrian BKC occurred at ca. 200 Ma in the western section of the WKOB. Proto-Tethys Ocean did not close until 230 Ma, possibly during the Early Mesozoic (200–180 Ma). [ABSTRACT FROM AUTHOR]

High Ba-Sr granitic rocks are widespread in Phanerozoic orogenic systems, and their petrogenesis is important for revealing the evolutionary process of the Proto-Tethys Ocean in the North Qilian orogenic belt. This paper presents a combination of zircon U-Pb age, whole-rock major and trace element concentrations, and Sr-Nd-Hf isotopic data for Caowa high Ba-Sr dioritic intrusion from the eastern part of the North Qilian orogenic belt, aiming to decipher its petrogenesis and tectonic setting. LA-ICP-MS zircon U-Pb dating yield an emplacement age of 450 ± 2 Ma for the Caowa intrusion, indicating a magmatic activity of the Late Ordovician. The Caowa quartz diorites contain moderate contents of SiO2, MgO, Mg#, and resultant high concentrations of Na2O + K2O, Fe2O3T, and Al2O3, displaying calc-alkaline and metaluminous characteristics. The studied samples have relatively elevated Ba (up to 1165 ppm) and Sr (561 to 646 ppm) contents, with obvious enrichment in LILEs (e.g., Ba, Th, U) and depletions in HFSEs (e.g., Nb, Ta, Ti), resembling those of typical high Ba-Sr granitoids in subduction zones. Together with enriched Sr-Nd isotopic composition [(87Sr/86Sr)i = 0.7082–0.7086, εNd(t) = −5.1 to −4.9], and the wide ranges of zircon εHf(t) values (−13.2 to +8.5), it suggests that these high Ba-Sr quartz diorites were derived from a mixture magma source between the ancient crust materials and the enriched lithospheric mantle metasomatized by fluid released from subducted oceanic crust or sediment. Taking into account the ophiolites, high pressure metamorphic rocks, and arc magmatic rocks in the region, we infer that due to the influence of the northward subduction of the Qilian Proto-Tethys Ocean, the Laohushan oceanic crust of the North Qilian back-arc basin was subducted during the Late Ordovician and resulted in extensive metasomatism of lithospheric mantle by fluids derived from oceanic crust or sediments, and the Caowa high Ba-Sr quartz diorites were generated in the process of crust–mantle interaction during the Late Ordovician. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) contains many microblocks, and their Precambrian basement origin and crustal evolution are disputed. This study focuses on the geochronology of metamorphic complexes from the Shuangsheng area, southeastern Inner Mongolia. Combined with regional geological data, we discuss the tectonic attribution of the metamorphic complexes and provide geochronological evidence for regional crustal evolution and tectonic affinity. From the Shuangsheng area, the Pingandi metamorphic complex and Baolige metamorphic complex are composed of greenschist–amphibolite facies metamorphic intrusive rocks and metamorphic supracrustal rocks, mainly including tremolite rock, chlorite rock, actinolitite (gneissic) plagioamphibolite, actinolitite schist, marble, and feldspar quartzite. Zircon U-Pb geochronology analysis of actinolitite and plagioamphibolite suggests that there were two intermediate-acid magmatic events (2500–2400 Ma and 2050–1980 Ma), one basic magmatic event (1860 Ma), and three metamorphic events (1930–1890 Ma, 1815–1785 Ma and 1740–1730 Ma). Based on comparisons with the regional Precambrian chronological spectrum, geotectonically, Precambrian geological records from the Shuangsheng area should belong to the basement of the Bainaimiao Arc Terrane (BAT). Each segment of the BAT shows consistent Precambrian chronological frameworks, which indicates that the BAT has a unitive Precambrian basement. The basement underwent crustal growth during 3.0–2.4 Ga and 2.1–1.4 Ga and multistage crustal reconstruction between 2.75 and 0.55 Ga, which is different from the crustal evolution of the North China Craton, northeast Gondwana continent, and Tarim Craton. In the early Palaeozoic, the Precambrian material provided varying source contributions to the arc crust of the BAT through crust–mantle interaction. [ABSTRACT FROM AUTHOR]

Whether the northern margin of the North China Craton (NCC) was a continental arc or in a lithospheric extensional setting during the Carboniferous is the primary divergence among different tectonic models about the terminal evolutionary history of the southeastern Central Asian Orogenic Belt (CAOB). The Alxa block is the western segment of the northern NCC and contiguous to the southeastern CAOB, and therefore the tectonic setting of the Carboniferous magmatic intrusions in this block can shed light on this controversy. In this contribution, new zircon U–Pb ages, elemental geochemistry, and Sr-Nd isotopes are presented for thirteen Late Carboniferous (~318–300 Ma) magmatic intrusions in the southwestern Alxa block. Among them, seven calc-alkaline I-type granites and one aluminous A2-type granite were probably generated by the partial melting and crystallization differentiation of various crustal sources (perhaps including earlier orogenic materials) under different temperature conditions. Four quartz diorites and one hornblende gabbro may be the partial melts of subduction-modified basaltic lower crust sources and sub-continental lithospheric mantle sources, respectively. According to the integration of the new results and regional geological correlations, the Alxa block and the southeastern CAOB were most likely in a uniform tectonic regime during the Carboniferous. At that time, this region was characterized by the lithospheric extension-related magmatic rock associations, the increasing mantle inputs over time, the clockwise P–T paths of high temperature-low pressure metamorphic rocks, and the transgression sedimentary sequences. All these lines of evidence suggest an intra-continental lithospheric extensional setting rather than a continental arc setting for the southeastern CAOB during the Carboniferous. [ABSTRACT FROM AUTHOR]

The discrepancy of geothermal gradients predicted by numerical modeling and recorded by peak metamorphic conditions of exhumed high/ultrahigh pressure (HP/UHP) metamorphic rocks triggers many uncertainties on the thermal structure of subduction zones, which is especially significant for continental subduction zones. Well‐constrained prograde P‒temperature (T) paths of HP/UHP rocks reflect the change in P–T conditions during continental subduction and are insusceptible to later processes, making them robust recorders of the thermal structure of subduction zones. To make a reliable estimation of the thermal structure of a continental subduction zone, the prograde P–T paths of three low (L)T‒UHP eclogites in the Dabie orogen were robustly constrained using a multiple thermobarometry method. The results demonstrate that these eclogites underwent three stages of metamorphic evolution during continental subduction from epidote amphibolite‐facies at ∼450°C–470°C/11–13 kbar, through amphibole eclogite‐facies at 585°C–600°C/17–19 kbar, to peak UHP eclogite‐facies at 600°C–630°C/27–29 kbar, indicating a low and continuously changing geothermal gradient from ∼12°C/km at lower crust depth (40 km) to 10°C/km at depth of 60 km and to ∼6°C/km at sub‐arc depth (100 km). The consistency of this result and the average thermal gradient recovered by peak metamorphic conditions of exhumed HP/UHP metamorphic rocks of continental origin suggests that the continental subduction zones may have a common thermal structure characterized by strongly concave upward geothermal gradient. A comparison of the results of this study and analytical models shows that shear heating may play a crucial role in the thermal evolution of continental subduction zones. Plain Language Summary: Subduction zones are important sites for material cycles, volcanic and seismic activity, and metallogenesis. The thermal structure (change of temperature with depth) is considered to place a first‐order control on these processes. By measurement of surface heat flow on the active subduction zones combined with formal modeling the thermal structure, thermal structure of oceanic subduction zones has been well constrained. In contrast, the thermal structure of continental subduction zones is far from clear as its geophysical information is usually modified by later continental collision. Metamorphic evolution paths of exposed rocks preserve complete information on the change of temperature and pressure with time, making it a reliable recorder of the thermal structure of a paleo‐continental subduction zone. In this contribution, we carried out a detailed petrological study to trace the metamorphic paths of ultrahigh pressure eclogites in the Dabie orogen, China and then recover the thermal structure of the continental subduction zone. The results demonstrate that the target rocks record a continuously decreasing thermal gradient with depth. Combining the results of this and previous studies, we suggested that the continental subduction zones have a common thermal structure characterized by varied thermal gradients from 10 to 12°C/km at crustal depth to 6–7°C/km at sub‐arc depth. Key Points: Prograde P–T paths of the ultrahigh pressure eclogites in the Dabie orogen are robustly constrained by a multi‐thermobarometry methodThe target eclogites record a decreasing thermal gradient with depth from ∼12°C/km at 40 km to 10°C/km at 60 km to ∼6°C/km at 100 kmContinental subduction zones may share a common thermal structure with strongly concave upward geothermal gradient [ABSTRACT FROM AUTHOR]

The results of U–Th–Pb geochronological studies of zircons from metamorphic rocks of the Amur group of the Synchuga Block of the Jiamusi continental massif are given. It is shown that garnet–biotite–sericite schists of the Amur group have a primary sedimentary origin. The lower depositional age of the protolith can be determined by the age of the youngest zircons from a group with Neoproterozoic ages of ~832 Ma. The upper age boundary of the protolith, apparently, corresponds to the age of metamorphic zircons of ~533 Ma. Thus, the schists of the Amur group of the Synchuga Block are Neoproterozoic in age rather than Early Precambrian, as was accepted earlier. [ABSTRACT FROM AUTHOR]

Unravelling the architecture and evolution of orogenic wedges are often hampered by the presence of strongly deformed large‐scale nappes made by homogeneous metasedimentary rocks lacking diagnostic metamorphic phases. Involving nappes or tectonic units which occupy most of the chain, reconstructing the thermal architecture of the hinterland–foreland transition zone of collisional belts represents a key point to comprehend the orogenic wedge tectonics. This work provides new thermal data from Raman Spectroscopy on Carbonaceous Material (RSCM) carried out in the low‐grade metamorphic rocks of the hinterland–foreland transition zone in the Variscan belt of Sardinia. The obtained TRSCM highlighted a temperature difference, from ~470–440°C down to ~440–380°C, for the internal and external nappes, respectively. We propose that both nappes experienced syn‐nappe greenschist‐facies metamorphism with different TRSCM, further heating localized along the tectonic boundary in between, that is the Barbagia Thrust (BT), and finally, post‐nappe stacking regional‐scale folding, that deformed the TRSCM spatial distribution and drove the present‐day thermal architecture. [ABSTRACT FROM AUTHOR]

The present research aims to explicate the tectonics of the northwest Himalayas, Pakistan, based on integrated gravity, magnetic and earthquake data. The raw gravity and magnetic data were processed, and seven isoanomaly maps were prepared for qualitative interpretation, whereas a gravity model was prepared along the selected profile for quantitative interpretation. The local earthquake data have also been used to identify the various seismogenic layers in the subsurface and to understand how seismicity relates to regional structural features. Three northwest‐trending thick‐skinned blind basement faults are identified from the present study, namely the Indus Kohistan Seismic Zone (IKSZ), Bagh Basement Fault and Hazara Lower Seismic Zone. The IKSZ is the tectonically most active among them and responsible for the 2005 Kashmir earthquake (Mw = 7.6) and 1974 Pattan earthquake (Mw = 6.2) in the region. The present study also delineated the prominent location of the Main Central Thrust in which the high‐grade metamorphic rocks of Higher Himalayan Crystalline thrust over low‐grade metamorphic rocks of Lesser Himalayas along this thick‐skinned fault. The field evidence such as ductile deformation, zone of inverted metamorphism, and brittle deformation also confirm this location. The sharp bending of the crystalline crust, as well as deep basement just south of Kohistan Island Arc (KIA), indicate that the high density and susceptibility rocks of this arc thrust on the leading margin of the Indian Plate along the Main Mantle Thrust. This thrust fault is a major suture zone separating the KIA in the north from the Indian Plate in the south. The other faults in the region exist in the sedimentary/meta‐sedimentary wedge and are thin‐skinned. It is inferred from the current investigation that the study area exhibits a composite style of deformation. Moreover, the gravity model combined with earthquake data suggested the existence of multiple décollement zones below the Hazara‐Kashmir Syntaxis. The model envisaged an increase in the thickness of the Indian Plate continental crust in the northeast direction. [ABSTRACT FROM AUTHOR]

Serpentinites of the mantle wedge were identified from a composite oceanic–continental subduction zone that occurs as the Hong'an orogen in east–central China. They were comprehensively investigated by an integrated approach of whole-rock major and trace elements, mineral major and trace elements, whole-rock and olivine O isotopes, and phase equilibrium modeling as well as zircon U–Pb ages, trace elements, and Hf-O isotopes. These serpentinites show high Mg# and MgO/SiO2 ratios but low Al2O3/SiO2 ratios as well as low Ti contents, resembling those from the mantle wedge rather than the subducting oceanic slab. Petrographic observations were combined with CIPW norm calculations to suggest that the protoliths of these serpentinites are refractory peridotites in the mantle wedge. Whole-rock and mineral compositions indicate that these serpentinites experienced multiple episodes of metamorphism and metasomatism during the tectonic development from oceanic subduction in the Carboniferous to continental collision in the Triassic. The enrichments of Th, U, light rare earth elements and high field strength elements in the whole rock and the finding of zircon inside them indicate their formation through metasomatism of the mantle wedge peridotites by subducting crust-derived fluids. The ca. 310 Ma zircon domains exhibit positive ε Hf(t) values of 4.5 to 19.1 and variable δ18O values similar to those of oceanic-type eclogites in the Hong'an orogen but different trace element compositions, indicating their formation through metasomatism by fluids from the subducting Paleotethyan oceanic crust. The ca. 430 Ma zircons exhibit U–Pb ages, trace elements and Hf-O isotopes similar to those of the protolith magmatic zircons in the oceanic-type eclogites. The older zircon domains also exhibit similar element and isotope compositions to inherited zircons from the high- to ultrahigh-pressure metamorphic rocks in the Hong'an orogen. Thus, these relict zircons would be physically transferred into the serpentinites by metasomatic fluids originating from the subducting Paleotethyan oceanic crust. High Th/U ratios for the ca. 310 Ma zircons imply their formation through the metasomatic reaction rather than direct precipitation from the subducting oceanic crust-derived fluids. The metasomatic zircons of Triassic age show negative ε Hf(t) values of −16.0 to −2.7, indicating their formation through metasomatic overprinting by deeply subducting continental crust-derived fluids in the continental subduction channel during the Triassic continental collision. In this context, the mantle wedge peridotites were first metasomatized in the Carboniferous by the subducting oceanic crust-derived fluids. Afterwards, part of the metasomatized peridotites were off-scrapped into the oceanic subduction channel, where they were hydrated by further subducting oceanic crust-derived fluids to form antigorite serpentinite at forearc depths. The antigorite serpentinite was carried to deeper depths during subsequent continental subduction and underwent dehydration there. This gave rise to metamorphic olivine with extremely high Fo values of 96.7 to 97.6 and higher MnO but lower NiO contents than common mantle olivine. The coexistence of lizardite, brucite and magnesite in the serpentinites indicates their retrograde processes of serpentinization and carbonation on the subsurface. Therefore, the present observations and interpretations of orogenic serpentinites provide insights into the multistage fluid metasomatism at different depths during the tectonic transition from oceanic subduction to continental collision. [ABSTRACT FROM AUTHOR]

Granulite is in general a key metamorphic rock that can be used to understand the tectonic architecture and evolutionary history of an orogenic belt. The Qingshuiquan mafic granulite in the East Kunlun orogenic belt, northern Tibetan Plateau, occurs as tectonic boudins together with lower-grade ophiolitic mélange assemblages within an amphibolitefacies crystalline basement. In this study, we investigated the geochemistry, geochronology, mineralogy, and phase modeling of the Qingshuiquan mafic granulite. Based on mineralogical observations and microstructures, three mineral assemblage generations were distinguished: an assemblage found as inclusions within garnet and amphibole comprising clinopyroxene + plagioclase + amphibole + quartz + ilmenite + rutile (M1); an inferred peak assemblage of garnet + clinopyroxene + plagioclase + amphibole + quartz + ilmenite ± orthopyroxene (M2) in the matrix; and a retrograde assemblage of amphibole and biotite coronae (M3) around clinopyroxene or orthopyroxene. Thermobarometric calculations and phase equilibrium modeling constrained a clockwise pressure-temperature (P-T) path for the Qingshuiquan mafic granulite with peak T conditions of 830-860 °C at 8.0-9.5 kbar. Prior to the peak T conditions, a pressure maximum of ~11 kbar at ~800 °C was recorded by rutile, ilmenite, and clinopyroxene inclusions in garnet and amphibole. The retrograde path was defined by a decompression segment followed by final cooling. The whole-rock geochemical results indicated that the protolith of the Qingshuiquan mafic granulite was similar to present-day enriched mid-oceanridge basalt (E-MORB) displaying low total rare earth element (REE) concentrations and a slight enrichment of light REEs, as well as flat high field strength element patterns in the primitive mantle-normalized trace-element diagram. Geochronologic results revealed that the protolith crystallization age of the mafic granulite is 507 ± 3 Ma, and the timing of granulite-facies metamorphic overprint is 457-455 Ma. This evidence, taken together with results from previous studies, indicates that the protolith of the Qingshuiquan mafic granulite can be interpreted as basaltic rocks of Proto-Tethys oceanic crust that experienced a first high-pressure granulite-facies imprint followed by subsequent decompression and granulite-facies overprint at slightly lower P and slightly higher T. This granulitefacies metamorphism can be attributed to the subduction of Proto-Tethys oceanic crust, which also generated numerous contemporaneous subduction-related magmatic rocks in the East Kunlun orogenic belt. [ABSTRACT FROM AUTHOR]

Extensive crustal anatexis is common during the decompressional exhumation of deeply subducted continental crust and the delamination of a collision‐thickened orogenic lithosphere, indicating that determining the timing of partial melting can provide insights into the possible tectonic evolution during orogenic processes. An integrated study of petrology, zirconology and whole-rock geochemical compositions from migmatites and pegmatites in the Nageng, Langmuri and Wulonggou area of the East Kunlun Orogenic Belt, is presented in this study. The protoliths of these migmatites include Tonian sedimentary rocks and ca. 440 Ma arc-related dioritic rock. Together with previous studies, an extensive crustal anatexis event recorded by anatectic zircons occurred after ca. 410 Ma. In addition, hafnium isotope analyses indicate that the anatectic zircons may or may not inherit their Hf isotope compositions from protolith zircons during partial melting, depending on whether or not the garnet Hf contributes to the Hf budget of anatectic melt. Thus, the most reasonable method to trace the source of granite is to compare the Hf isotope composition of anatectic zircon in migmatite and magmatic zircon in contemporaneous granite. By such method, anatectic melt produced by migmatites in this study could account for both penecontemporaneous A- and I-type granites with high magmatic zircon εHf(t) values and S-type granites with low magmatic zircon εHf(t) values. As the extensive crustal anatexis is later than both metamorphic peak and amphibole-facies retrogression of high-pressure and ultrahigh-pressure (HP-UHP) metamorphic rocks, it is reasonable that post-collision orogenic collapse of the collision‐thickened orogenic lithosphere as a result of delamination and asthenospheric upwelling occurred after ca. 410 Ma, which is also supported by contemporaneous granulite-facies metamorphism, molasse deposition, and magmatic events including Xiarihamu mafic-ultramafic intrusions, A-type granites, and mafic dykes formed in the continental rifting setting. [ABSTRACT FROM AUTHOR]

The Trans-North China Orogen is a major Neoarchean Paleoproterozoic collisional orogenic belt above the North China Craton, formed due to prolonged and complex processes. Even though many Neoarchean-Paleoproterozoic magmatic and metamorphic activities have been reported, due to the Huozhou Complex's small outcropping range, little attention has been paid to the origin of various igneous rocks of the Huozhou Complex in the center of the Trans-North China Orogen. The Huozhou Complex, located south of the Lüliang, Wutai, and Hengshan complexes, is an important window into the Early Precambrian structure and evolution of the North China Craton. Its magma and metamorphism are crucial to understanding the development of the structural evolution of the Trans-North China Orogen. The Huozhou metamorphic complex area exposes a range of Precambrian metamorphic rocks, among which the most extensively dispersed is felsic biotite plagioclase gneiss. In this study comprehensive geological field survey, micropetrology, chronology, geochemistry, and Hf isotope analysis were carried out for the Qinggangping and Anziping gneiss in the north of the Huozhou Complex. The results show that the magmatic zircon age of the Qinggangping gneiss is 2196 ± 14 Ma, and its protolith is I-type granite, formed by partial melting of igneous rocks in the absence of weathering. Its source is mainly the juvenile crust from depleted mantle dating 2431–2719 Ma, with a small amount of mantle-derived material. The Anziping gneiss has a metamorphic zircon age of 1931 ± 13 Ma with an S-type granite protolith belonging to peraluminous granite. The Anziping gneiss is formed by recycling pre-existing crustal components at 2613–2848 Ma. A minor quantity of mantle-derived magma is also introduced to the crust simultaneously. The samples of Qinggangping gneiss and Anziping gneiss show the characteristics of obvious negative Nb, Ti, and P elements in the spider diagram of primitive mantle standardization. This implies that the rocks have the characteristics of magmatic rocks in an island arc or subduction environment, which could have formed in the tectonic environment of the continental margin arc. [ABSTRACT FROM AUTHOR]

High-pressure metamorphic rocks occur as distinct belts along subduction zones and collisional orogens or as isolated blocks within orogens or mélanges and represent continental materials that were subducted to deep depths and subsequently exhumed to the shallow crust. Understanding the burial and exhumation processes and the sizes and shapes of the high-pressure blocks is important for providing insight into global geodynamics and plate tectonic processes. The South Beishan orogen of northwestern China is notable for the exposure of early Paleozoic high-pressure (HP), eclogite-facies metamorphic rocks, yet the tectonism associated with the HP metamorphism and mechanism of exhumation are poorly understood despite being key to understanding the tectonic evolution of the larger Central Asian Orogenic System. To address this issue, we examined the geometries, kinematics, and overprinting relationships of structures and determined the temperatures and timings of deformation and metamorphism of the HP rocks of the South Beishan orogen. Geochronological results show that the South Beishan orogen contains ca. 1.55–1.35 Ga basement metamorphic rocks and ca. 970–866 Ma granitoids generated during a regional tectono-magmatic event. Ca. 500–450 Ma crustal thickening and HP metamorphism may have been related to regional contraction in the South Beishan orogen. Ca. 900–800 Ma protoliths experienced eclogite-facies metamorphism (~1.2–2.1 GPa and ~700–800 °C) in thickened lower crust. These HP rocks were subsequently exhumed after ca. 450 Ma to mid-crustal depths in the footwall of a regional detachment fault during southeast-northwest–oriented crustal extension, possibly as the result of rollback of a subducted oceanic slab. Prior to ca. 438 Ma, north-south–oriented contraction resulted in isoclinal folding of the detachment fault and HP rocks. Following this contractional phase in the middle Mesozoic, the South Beishan orogen experienced thrusting interpreted to be the response to the closure of the Tethyan and Paleo-Asian Ocean domains. This contractional phase was followed by late Mesozoic extension and subsequent surface erosion that controlled exhumation of the HP rocks. [ABSTRACT FROM AUTHOR]

The Chengdu plain westward to the Songpan-Ganzi fold belt is a transition zone from basin to plateau. The region has huge undulation and fall, strange and steep terrain, severe river undercutting and erosion, frequent tectonic activities, and strong internal and external dynamics, resulting in frequent earthquakes and numerous geological hazards. The article uses Sentinel-1A data covering the whole region and ALOS-2 data in key areas for InSAR technology processing, combined with GIS spatial analysis, early identification of active landslide disasters in the study area and exploration of spatial distribution patterns, supplemented by field surveys to support the following understanding. According to the inducing factors of the disaster, the areas where the disaster points are concentrated can be divided into three zones: disaster zones induced by reservoir storage, such as Maoergai Reservoir in Heishui County; disaster zones caused by broken mountains after the earthquake, such as the junction of Minjiang River and Heishui Gully in Maoxian County, the area from Wenchuan County to Li County, and the area from Jiuzhaigou County to Shijiba Town; disaster zones cause by essential rivers, such as Zhouqu County, Lazikou Town, Xiaojin County, and Danba County. The active landslides in the region are mainly distributed in metamorphic rocks such as phyllite and clastic rocks such as shale. The disasters are mainly distributed in the terrain with aspects of SE, E, NE, slope greater than 15°, elevation interval of 1000~3000 m, relative elevation difference greater than 1000 m, and curvature between -0.5~?0.5. The disaster points are mainly close to the Minjiang fault, the Tazang fault, the Guanggaishan-Northern Dieshan fault, and the Maowen-Wenchuan fault zone. The combination of orbit-ascending and orbit-ascending data of Sentinel-1A increases the effective observation area to 73.41% of the total area. The ALOS-2 data are relatively better than the Sentinel-1A data in the western Sichuan plateau area. The coincidence rates of ALOS-2 and Sentinel-1A are 58.7% and 44.8%, respectively, in Jiuzhaigou and Maoxian, and the identified number of the former is 3.98 times and 1.39 times that of the latter. [ABSTRACT FROM AUTHOR]

This study integrates provenance and statistical data, along with published sedimentological results, applied on the Lower Oligocene submarine‐fan deposits in Pindos foreland basin. Twelve outcrops were analysed using conglomerate clast composition, petrographic and statistical analysis and this integration suggests that the studied deposits were sourced by the Pindos Orogen. Conglomerate clast composition analysis suggests that the studied deposits contain mainly limestone clasts, followed by sandstone and chert clasts. This conclusion is further supported by the petrographic and cathodoluminescence analyses that have been conducted on the conglomerate matrix and, additionally, suggest the influence of a low‐grade metamorphic source. Potential source rock candidates in the Pindos Orogen that provided the detritus in the succession are represented by the Mesozoic carbonates (limestone and chert), the Cenozoic transitional (mixed carbonate and siliciclastic) and the Cenozoic clastic submarine‐fan deposits (sandstone). The rock units of Pelagonian zone likely represent the low‐grade metamorphic source rock. The principal component and cluster analysis of clast lithologies suggest the existence of three compositional clusters, with the first one being controlled by black chert clasts, the second one by sandstone clasts and the third one by limestone and red chert clasts. The upward increase of chert and lithic fragment abundances is ascribed to the progressive unroofing of the Pindos orogenic source regions. This study utilizes the Pindos foreland basin as an example to unravel the contribution of orogenic processes on sedimentary provenance of the adjacent pro‐foreland basins. Furthermore, this study highlights the advantage of implementing a multi‐faceted approach, including statistical treatment in sedimentary provenance. [ABSTRACT FROM AUTHOR]

The authors summarize the available data on the structural-formational zonality of the Urals. Seven megazones of the Ural Fold Belt from west to east have been studied. The paleocontinental sector of the Urals, i.e., the former passive margin of the Baltica/Laurussia paleocontinent includes the Cis-Uralian Foredeep, the West Uralian and Central Uralian megazones. The paleo-island-arc sector, a collage of ophiolites, island-arc, and microcontinents (?), includes the Tagil–Magnitogorsk, East Uralian, and Transuralian megazones. These sectors are separate by the suture zone (the Main Ural Fault MUF). New data on the geochronology of the Bashkirian anticlinorium belonging to the Central Uralian Megazone are presented. Within the Central Uralian Megazone, the Paleozoic facies of the continental rise have been identified for the first time. The Tagil and Magnitogorsk island-arc terranes are correlated. The Tagil terrane began its development earlier and experienced two cycles of magmatism. The Magnitogorsk island arc is characterized by the shorter period of formation, gently dipping and less deep erosional downcut. The ideas, according to which the East Uralian megazone is considered a Madagascar-type microcontinent (Kazakhstan or Mugodzhary), are under discussion. The previously proposed Proterozoic age of the metamorphic rocks of the eastern segment of the Urals has remained unproven. The East Uralian Megazone, a rather young structure, is an integral part of the Ural Fold Belt and did not belong to hypothetical older megastructures. The main stage of folding, tectonic stacking, metamorphism, and granitization in the Ural Fold Belt are dated back to Late Paleozoic. It is shown that the observed latitudinal zonality of the Urals is determined by different present-day erosion depths. The vertical movements that determined the sublatitudinal zonality occurred mainly in the Middle–Late Triassic and were induced by north–south compression. [ABSTRACT FROM AUTHOR]

Orogenic gold deposits associated with metamorphic orogenic fold belts are the major sources of gold currently being mined in the world. The role of metamorphic and magmatic processes and crustal and mantle sources in the gold mineralization genesis are of much debate. The formation of orogenic gold deposit in Precambrian metamorphic belts is usually described by а metamorphic devolatilization model. Some of the orogenic deposits, however, are proved to be much younger than the peak of regional metamorphism. Geological features of these deposits suggest close relation of their gold-forming systems with deeper lithospheric processes. The Baikal-Muya Belt (BMB) of the Central Asian Orogenic Belt is an example of such a region. The BMB comprises ca. 20 orogenic gold deposits and occurrences of Permian age. Gold mineralization at the deposits is usually located in quartz lodes situated in the vicinity of fault zones in association with Late Paleozoic sub-alkaline and alkaline basic and acid intrusions. Using high-precision (0.02–0.03%, 2SD) MC-ICP-MS method, we studied in detail Pb isotopic composition of the Permian gold-bearing mineralization at six BMB deposits, as well as metamorphic and igneous rocks of Tonian to Permian age. The 46 studied sulfide samples representing BMB gold-bearing lodes are highly variable regarding their Pb isotopic composition: 206Pb/204Pb from 16.628 to 18.293, 207Pb/204Pb from 15.325 to 15.614, and 208Pb/204Pb 36.742 to 38.384. Individual Permian orogenic gold deposits and occurrences differ in Pb isotope ratios and degree of their Pb isotopic composition heterogeneity. The Pb isotope features weakly correlate with the geological setting of the deposits. Age-corrected Pb–Pb data for the 41 samples of the BMB metamorphic and igneous rocks are similar to those of the gold mineralization: 206Pb/204Pb from 16.89 to 18.57, 207Pb/204Pb from 15.34 to 15.65, and 208Pb/204Pb 36.67 to 38.4. The high variability of model parameters (µ2 = 9.02–9.78, ω2 = 35.2–42.5, Th/U = 3.84–4.46) and Pb-isotope mixing trends for the ore lead suggest different sources of the metal. One of the sources was the BMB Neoproterozoic metamorphic and magmatic rocks hosting the gold deposits. The obtained data also suggest a common source for these deposits which is identical in its Pb-isotope characteristics to the Permian alkaline and sub-alkaline igneous rocks. We propose that the metasomatized subcontinental lithospheric mantle (SCLM) as well as the SCLM derived alkaline mafic magmas could be the important source of metals (including gold) for the Permian orogenic gold mineralization of the BMB. [ABSTRACT FROM AUTHOR]

Understanding the tectonic evolution of the Yenisei Range offers important clues not only for the tectonic evolution of orogenic belts at margins of ancient cratons but also for solving the problem of the incorporation of the Siberian craton into the Rodinia supercontinent. Results of mineralogical−petrological, geochemical, and isotope–geochemical studies provide an insight into the petrogenesis, geotectonic settings, thermodynamic parameters of formation, and the ages of the metamorphism and protoliths for the contrastingly compositionally different rocks of the Garevka metamorphic complex. The paper discusses the possible models for the origin of the rock complexes and the geodynamic settings in which they were formed. The western margin of the Siberian craton was determined to have been affected by two pulses of Neoproterozoic endogenic activity, which were related to the origin of the Rodinia supercontinent (930–900 and 880–845 Ma), and which correlated with Grenville and post-Grenville processes responsible for Valhalla folding. The regional geodynamic history is correlated with the coeval sequence and similar style of tectono−thermal events in the peripheries of the large Precambrian cratons Laurentia and Baltica, which is consistent with the proposed Neoproterozoic paleogeographic reconstructions of close spatiotemporal relationships between these cratons and their incorporation into Rodinia configuration. [ABSTRACT FROM AUTHOR]