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The Clarke River Shear Zone marks the boundary between the Thomson and Mossman orogens in the northeastern Tasmanides. To better understand the kinematic history of this east-northeast-trending shear zone, and its role during the tectonic history of eastern Gondwana, we investigated rock deformation along a segment of the Clarke River Shear Zone. Based on field observations, interpretation of aeromagnetic data and microstructural analysis, we show that the Clarke River Shear Zone experienced at least three phases of reactivation. Gently plunging stretching lineation and kinematic indicators, such as steeply plunging asymmetric folds and asymmetric porphyroclasts, correspond to an early phase of sinistral strike-slip ductile shearing. Subsequent general dextral shear deformation is suggested based on the presence of S-tectonites, symmetric porphyroclasts and kinematic indicators with dominant dextral and subordinate sinistral shear senses. This phase, which occurred under amphibolite-facies metamorphic conditions, was contemporaneous with the emplacement of the Craigie Tonalite, for which we obtained a new zircon U–Pb crystallisation age of 410.3 ± 1 Ma. A later reactivation phase along the Clarke River Shear Zone, under brittle conditions, is indicated by the presence of cataclasite zones and chlorite–epidote alteration. Based on our findings, and regional information on the tectono-magmatic evolution of northeastern Queensland, we suggest that the Clarke River Shear Zone was possibly a sinistral transform fault during the Silurian. During the Devonian, it is possible that deformation along the Clarke River Shear Zone was related to the transition between the non-retreating subduction zone in the north, and the highly mobile (retreating) plate boundary farther south. However, the dextral kinematic component associated with this deformation is not fully explained. Brittle deformation, likely associated with dextral transpression during the Carboniferous, marked the last stage of activity along the Clarke River Shear Zone. The Clarke River Shear Zone records three phases of reactivation during the Silurian–Carboniferous. Ductile dextral general shear deformation along the Clarke River Shear Zone occurred at ca 410 Ma, based on zircon U–Pb dating of a syn-tectonic intrusion. The Clarke River Shear Zone likely accommodated subduction segmentation during the Silurian–Devonian. [ABSTRACT FROM AUTHOR]

Tick Hill gold deposit is a unique gold mineralisation style in the Mary Kathleen Fold Belt in the Mount Isa Inlier. The gold at Tick Hill is generally pure without silver and was formed during two discrete metamorphic-deformation events (D1 and D3). Early gold was observed as inclusions or coarse grains hosted within D1 peak-metamorphic diopside, scapolite and hornblende from the garnet–biotite–hornblende (tschemakite)–plagioclase (andesine)–quartz assemblage. Late gold is closely associated with bismuth selenide, chlorite, albite, sericite and K-feldspar, and formed during D3. The syn-D1 garnet–plagioclase–hornblende–quartz–biotite assemblage was used to constrain the pressure and temperature (P–T) conditions of metamorphism and mineralisation using the garnet–plagioclase–hornblende–quartz barometer and the hornblende–plagioclase, garnet–biotite and garnet–hornblende thermometers. The results show that peak metamorphism at Tick Hill reached P–T conditions of 6.0–7.6 kbar and 720–760 °C. These P–T conditions together with gneissic and migmatisation textures recorded in different rock types at the Tick Hill area indicate that the peak metamorphism preserved in the area occurred at the amphibolite–granulite facies, compared with the amphibolite facies at the southern Mary Kathleen and Eastern Fold Belt. The D3 chlorite, which formed during stage 2 to stage 4 mineralisation events, displays a wide range of compositions reflecting a gradual retrograde temperature change from ∼380 °C to ∼130 °C. The pressures during D3 could not be reliably determined, but the presence of various Bi-selenides suggests that towards the waning stages of D3, the rocks may have been exhumed to a pressure less than 1 kbar. The 1790–1770 Ma D1 peak metamorphism at Tick Hill reached 6–7.6 kbar and 720–760 °C. The 1525–1520 Ma D3 hydrothermal mineralisation at Tick Hill Deposit occurred at temperatures between ∼380 °C and ∼130 °C. The main D3 gold accumulation episodes at Tick Hill occurred at temperatures ranging from ∼380 to 160 °C. [ABSTRACT FROM AUTHOR]

The U–Pb detrital zircon record of the Surat Basin, an important part of the Great Australian Superbasin, has already revealed important insights about sediment source terranes. However, owing to the high closure temperature of zircons, low-temperature thermal events that might have impacted the sediment are not recorded. Here, new 40Ar/39Ar detrital mica ages, which record low-temperature events as a result of isotopic resetting, are paired with published U–Pb detrital zircon ages from the same samples to provide a more complete interpretation of the tectonic and thermal history of the Jurassic-age Precipice Sandstone and Evergreen Formation. The 40Ar/39Ar geochronology of mica grains from five wells reveals two broad groups with distinct age populations: 1500–180 Ma and 150–45 Ma. Micas older than about 180 Ma are sourced from multiple terranes. The slight discrepancy in ages between the 40Ar/39Ar and the U–Pb systems of the same samples may represent differences in closure temperature. However, some micas, such as those dating to ca 180 Ma, may also reflect a thermal reset event. Similarly, the younger group of micas, split into Cretaceous and Paleogene populations, reflect the impact of post-depositional thermal events on the basin. Isotopic resetting of the micas was likely the result of hydrothermal fluids migrating through reactivated faults, fractures and/or porous and permeable sediments. The origin of the fluids during the Cretaceous can be linked to an eastern subduction zone and subsequent igneous underplating resulting in uplift and denudation. The exact source of the hydrothermal fluids for the micas of Paleogene age, recorded in samples collected from the base of the Evergreen Formation, however, remains uncertain. Importantly, 40Ar/39Ar dating of mica from sandstones permits the detection of post-depositional thermal events that may have implications for tracing fluid migration throughout the basin and reconstructing the Cretaceous–Paleogene tectonic history of the basin. Combining 40Ar/39Ar dating of micas with U–Pb dating of zircons reveals a more complete tectonic and thermal history of the Jurassic-age Precipice Sandstone and Evergreen Formation of the Surat Basin. 40Ar/39Ar dating of detrital micas reveals two broad groups with distinct age populations: 1500–180 Ma and 140–45 Ma. Ages older than ca 180 Ma are linked to multiple source terranes, including the Thomson and New England orogens, and the contemptuous magmatic arc. Ages younger than 150 Ma are most likely the result of post-depositional thermal resetting events, which may have implications for fluid movement throughout the basin. [ABSTRACT FROM AUTHOR]

The Mongolian micro‐continental fragments play an important geodynamic role in the Palaeozoic evolution of the Central Asian Orogenic Belt. However, the original provenance of individual blocks within the Nuna/Columbia and Rodinia supercontinents is not well constrained. In this work, we present zircon U–Pb and Lu–Hf isotopic data from the Mesoproterozoic to Neoproterozoic metamorphosed cover of the Baidrag Block in central Mongolia. These data reveal important maxima in the Neoarchean, Palaeoproterozoic and locally Neoproterozoic. Although the majority of the new data can be attributed to local sources within the basement of the Mongolian micro‐continental fragments, an important contribution of juvenile 2.0 Ga zircons is linked to the western margin of the Siberian Craton, and 1.5 Ga zircons are either directly derived from North Australia or indirectly recycled from sediments in NW Laurentia. [ABSTRACT FROM AUTHOR]

The late Archean Western Dharwar Craton supergroup has volcanic and sedimentary rocks deposited during 2900–2600 Ma underlain by the Sargur Group basement of 3.36–3.2 Ga granitic gneiss and older supracrustal rocks. The western part of the craton, known as the western province (Dharwar Foreland), comprises four major schist belts (Western Ghats-Bababudhan-Shimoga-Chitradurga). A regional gravity and magnetic (Total Field) survey was done in the Shimoga region. The geophysical data of the study area reveal the subsurface extension and behaviour of the exposed rocks of the area. The Euler deconvolution was used to define the depth of the anomaly sources. Euler depth solution for the spherical body (structural index 2), window size = 10, and depth tolerance = 5% depicts the depth of the various sources. The Euler depth solutions cluster over the hook-shaped schist rock of the Medur group (at the northern part of the area) reveals that the body's depth varies from 1 to 4 km in the central part, and at the northern flank, it goes up to 7 km. The solution also brought out the depth of the anomalous body near Hithala, within 4 km. The 2D forward depth modelling of the anomalous zone brings out the involvement of the tectonic forces in the generation of this anomalous body. The more precise depth from the model has been estimated between 2 and 3 km. The model clearly shows the relationship between schist rocks and the basement. However, the high-gravity anomaly has been modelled as the manganese bearing horizon, which has come to optimum depth because of folding and faulting in the region, thus providing a favourable zone for manganese deposition. [ABSTRACT FROM AUTHOR]

The Late Cretaceous magmatic history of the Eastern Pontides Orogenic Belt (NE Turkey) was generally characterized by common I-type and lesser A-type plutons in varying size and composition. Of these, A-type plutons from the Şebinkarahisar (Giresun) area yield SHRIMP zircon U-Pb age of 77.36 ± 0.96 Ma. The rocks of these plutons display a wide range of SiO2 contents (53.63 to 70.96 wt.%) and Mg-numbers (6.2–32.19) with A-type affinities characterized by enrichment in K2O and Na2O, Ga, Zr, and strong negative Eu anomalies. They also show arc-type petrochemical features including enrichment of large-ion lithophile elements (e.g. Cs, K, Rb) and light rare earth elements (LaN/LuN = 6.27–15.61), but depletion in high strength field elements (e.g. Nb, Ta, Ti, and P). The (87Sr/86Sr)i ratios and ɛNd(i) values of the studied rocks are in the range of 0.705129 to 0.0705347 and −3.64 to −3.12, respectively, while bulk rock ɛHf(i) values are between 1.86 and 4.36. They are characterized by positive zircon ɛHf(i) (1.74 to 10.88) plotting between the chondrite and depleted mantle evolutionary line values. Our data combined with the previous studies suggest that the magmas, that formed the Late Cretaceous plutons, were generated in an extensional tectonic environment due to slap roll-back and trench ward migration of the subduction zone to the south. The generation of hybrid magmas forming the studied plutons is in response to the melts derived from a metasomatized lithospheric mantle source, a relatively deeper mantle source, and the juvenile crust along with the heat transfer and decompression. Multi-sourced magmas rise through the continental crust and reach the final composition by predominantly fractional crystallization processes. [ABSTRACT FROM AUTHOR]

The very early herbaceous vegetation which established in the clearings following 2018 'Vaia' storm was investigated in some pre-Alpine areas of Northeast Italy, on calcareous as well as acidic substrata. Sixty-two original vegetation-plot records were executed in spruce or mixed beech-silver fir-spruce blowdown forests, within two years after the salvage logging had been completed. According to different origin and degree of soil disturbance, different communities were recognised. Galeopsis pubescens and G. tetrahit rich stands develop as ephemeral annual associations at the beginning of the regeneration succession where partially decomposed coniferous needles and twigs have accumulated in the litter. Soils with altered profiles due to forestry machineries harbour dominance of perennial herbaceous species (especially Senecio nemorensis agg., Atropa bella-donna, Epilobium angustifolium) which origin as many already recognised associations or vegetation types we ascribed to community level. All coenoses belong to Epilobietea angustifolii class, with the exception of Calamagrostis arundinacea-rich stands on undisturbed base-rich as well as base-poor soils, whose syntaxonomic positions are unclear. [ABSTRACT FROM AUTHOR]

On 22 April 2022, a Mw 5.7 earthquake was generated near Stolac (Bosnia and Herzegovina). The mainshock was succeeded by several aftershocks, three of which were significant. Two Mb 4.3 earthquakes occurred on 23 April 2022, and a Mw 4.8 earthquake was generated on 24 April 2022. Available data from fault mechanism solutions revealed that the mainshock activated a reverse fault, while the aftershock generated a normal fault with a right-lateral component. The Balkan Peninsula stands as one of the most active geodynamic areas in Central and Eastern Europe due to its location within the collision zone between Eurasian and African tectonic plates and the Anatolian microplate. Recorded earthquakes in Bosnia and Herzegovina are related to the energy generated by the subduction of the African tectonic plate under Eurasia. Furthermore, the seismicity of Bosnia and Herzegovina, particularly its southern part, is profoundly influenced by the subduction of the Adriatic microplate under the Dinarides. The Dinarides are a mainly fold and thrust belt that extends from the Southern Alps in the northwest to the Hellenides in the southeast and make dominant the tectonic system of Bosnia and Herzegovina. In this study, two pairs of SAR images obtained from the Sentinel-1 satellite mission were utilized to generate satellite LOS surface displacements using the DInSAR method. Moreover, LOS displacements were decomposed into vertical and east–west horizontal components by combining ascending and descending satellite orbits. Ultimately, the InSAR results were analyzed and compared with the data obtained from the CROPOS CORS GNSS station in Metković (MET3). [ABSTRACT FROM AUTHOR]

The Eastern Kunlun Orogenic Belt (EKOB), located north of the Qinghai-Tibetan Plateau, recorded voluminous late Palaeozoic – early Mesozoic intermediate-acid volcanic rocks. The tectonic evolution of the Palaeo-Tethys Ocean from initial subduction and final closure and post-collision extension has been hotly debated. This study examines the petrogenesis of Palaeozoic to Early Mesozoic volcanic rocks at six locations: Xiahe, Elashankou, Jirimai, Harizha, Nagengkangqieer, and Yazigounan. The investigation involves detailed field observations, petrology, zircon U-Pb geochronology, Lu-Hf isotopes, and whole-rock geochemical analysis. The rocks analysed represent three episodic volcanic events. The ca. 257–245 Ma volcanic rocks were derived from magma mixing response to the subduction. The ca. 227–220 Ma highly fractionated I-type volcanics were derived from partial melting of the ancient lower crust, with varying contribution proportions of mantle materials. The ca. 216 Ma A-type volcanic rocks derived from partial melting of the juvenile crust. In this study, using existing regional geological data and spatiotemporal distribution of the magmatic region, combined with our new data, we attempt to propose more rational models to reveal the tectonic evolution of the Palaeo-Tethys Ocean, and we recognize three significant time nodes: (1) Ca. 240 Ma marks the final closure time of the Palaeo-Tethys Ocean. (2) Ca. 230 Ma indicates the vital tectonic regime transition from compression to extension response to slab break-off and continued lithospheric delamination. (3) Ca. 216 Ma mark the beginning of the final stage of orogeny in the EKOB, and mild magmatism lasts to ca. 200 Ma in response to the mountain collapse. [ABSTRACT FROM AUTHOR]

It is evident that the Yangtze Craton was involved in the formation and breakup of the Columbia supercontinent. However, due to the scarcity of Mesoproterozoic geological records and reliable paleomagnetic data, little is known about the timing, paleogeographic position, and geological processes of the Yangtze Craton. We conducted detailed geological mapping, petrographic, geochemical, and in situ zircon U-Pb and Lu-Hf isotopic investigations on newly recognized Mesoproterozoic quartz syenite and monzogranite in the Dabie orogen, northern Yangtze Craton. The results show that the quartz syenite and the monzogranite were emplaced at 1369 ± 12 Ma and 1372 ± 5 Ma, respectively. Both rocks are high in total alkali (K2O + Na2O) content and FeOt/(FeOt + MgO), with elevated diagnostic 10,000*Ga/Al ratios and Zr + Nb + Ce + Y concentrations, and enrichment in light rare earth elements. They are also depleted in heavy rare earth elements with significant negative Eu anomalies but remarkably low Sr, Cr, and Ni contents. These compositions define affinity to A1-type granite. In addition, the quartz syenite displays variable zircon Hf and homogeneous whole-rock Nd isotopic compositions with positive εHf(t) values of +0.7 to +5.7 (average +2.4) and εNd(t) values of -0.1 to +2.5 (average +1.0). In contrast, the monzogranite has homogeneous zircon Hf and whole-rock Nd isotopic compositions with negative εHf(t) values of -5.7 to -2.6 (average -4.8) and εNd(t) values of -3.5 to -1.5 (average -2.2). We propose that the quartz syenite was likely generated by the partial melting of juvenile, crust-derived melt with involvement of minor mantle-derived material, while the monzogranite was likely derived from the partial melting of ancient crust in an extensional tectonic regime (e.g., continental rift). Based on the newly recognized ca. 1.37 Ga granitic magmatism and previously reported magmatic events, we argue that the mid-Mesoproterozoic (ca. 1.37 Ga) magmatism in the Yangtze Craton occurred in response to the breakup of Columbia, and represents the separation of the Yangtze Craton from Columbia. Furthermore, according to comparable magmatic and sedimentary events, we propose that the Yangtze Craton, along with central Hainan Island, may have been linked to northwestern Laurentia, southwestern Siberia, and northeastern Australia during 1.6-1.4 Ga. [ABSTRACT FROM AUTHOR]

A new tectonic model is presented to explain the tectono-stratigraphic evolution of the Paleoproterozoic Karrat Group in central West Greenland and the polyphase deformation, magmatism, and metamorphism of the Rinkian orogen. Sedimentation of the Karrat Group initiated after ca. 2000 Ma in an intracratonic rift basin with basal quartzites overlying Archean gneisses of the Rae craton. Rift-related alkaline volcanic rocks and synrift siliciclastic sediments were deposited in the north while an evaporite-carbonate platform developed in the south. The rift basin evolved to a back-arc basin, with associated subalkaline volcanic rocks, concomitant with the intrusion of arc-related granitoids of the Prøven igneous complex along the basal contact of the Karrat Group between 1900 Ma and 1850 Ma. The Karrat Group and magmatic arc rocks underwent metamorphism ca. 1830-1800 Ma during the collisional phase of the Rinkian orogeny. The metamorphic grade of the Karrat Group increases from greenschist facies in the south to granulite facies in the north, where it is marked by migmatization and emplacement of S-type leucogranites. Extensive east-southeastward thrust emplacement and fold vergence characterize the Rinkian orogen south of the Prøven igneous complex magmatic arc, where the arc-continent collision is established along a top-to-the-ESE shear zone postdating the Rinkian metamorphism. In summary, the Karrat Basin developed on the upper plate above eastward-dipping subduction and, together with the Rinkian orogen, represents the result of arc-continent collision that initiated the structuring of a backarc fold-and-thrust system antithetic to the subduction system. [ABSTRACT FROM AUTHOR]

Syncollisional magmatism plays an important but underappreciated role in continental crust growth and maturation. However, the origin of syncollisional intermediate magmas in continental subduction zones is controversial, with some models suggesting they form by arc-related processes, and others indicating they form by later slab breakoff-induced melting. Diorite porphyry dikes intruding granitic gneiss in the Paleo-Tethyan Sulu ultrahigh-pressure (UHP) continental collisional orogen have inherited zircon grains with 206Pb/238U ages of ca. 749-238 Ma, and magmatic zircons with weighted mean ages of 216-215 Ma, falling within the well-constrained time range (ca. 235-208 Ma) tracking exhumation of the Sulu UHP rocks from UHP peak conditions to amphibolite facies; they are thus syncollisional. The dikes have high Cr (330-402 ppm), Ni (84.5-103 ppm), and Mg# (64-66) values, showing a mantle origin. The porphyries have relatively high Sm/Yb, Nb/Y, La/Yb, and Gd/Yb ratios, representing a classic signature of slab breakoff magmatism. Together with the arc-like traceelement patterns and enriched Sr-Nd isotope compositions, ages, and εHf(t) values (-19.5 to -17.0) of magmatic zircons and their tectonic setting, we propose a syncollisional slab breakoff model in which the melts were initially generated from asthenospheric upwelling in the gap created when the oceanic slab attached to the Yangtze craton detached underneath the North China craton during Late Triassic collision following Paleo-Tethys Ocean closure. The diorite porphyry dikes have consistent Sr-Nd isotope compositions and spatiotemporal relationships with the nearby Shidao gabbro-syenite-granite complex, for which the tectonic affinity is controversial. Thus, we argue that the diorite porphyries and Shidao complex were sourced from two cratons, including the enriched subcontinental lithospheric mantle of the North China craton, which interacted with abundant felsic melts derived from the sinking slab breaking away from the subducted crust of the Yangtze continental-ocean transitional margin. This study sheds new light on crustal recycling versus continental growth in collisional orogens and implies that considerable syncollisional intermediate magmas can be generated by slab breakoff in continental subduction zones, representing hybrid additions to continental growth that are different and more evolved than arc magmas and have a composition similar to that of the bulk continental crust. [ABSTRACT FROM AUTHOR]

Composite Ni-Cu sulfide- and Fe-Ti oxide-bearing mafic-ultramafic intrusions have been discovered in convergent margin settings worldwide, but their origins remain enigmatic. Permian Kebu mafic-ultramafic intrusion in the Central Asian Orogenic Belt hosts both Ni-Cu sulfide and Fe-Ti oxide mineralization and formed in a post-collisional, Andean-style arc setting. The Ni-Cu sulfide- and Fe-Ti oxide-bearing rocks in the intrusion have similarly arc-like trace element patterns on the primitive mantle-normalized trace element diagram and negative εNd(t) values (-16 to -5), which indicate that the parental magma of the intrusion may have been derived from the enriched, metasomatized lithospheric mantle. The magma oxygen fugacity (fO2) was calculated to be FMQ + 1.3~FMQ + 2.0, which can be attributed to the evolution of hydrated parental magma derived from the metasomatized lithospheric mantle. Also, the rocks all have negative δ13C values (-28.5‰ to -20‰), which indicates incorporation of external-derived crustal organic carbon into magmas. However, the Ni-Cu sulfide-bearing rocks contain more high-temperature carbon than the Fe-Ti oxide-bearing rocks. Modeling results based on alphaMELTS show that the magmas forming the Ni-Cu sulfide-bearing rocks may have assimilated more organic carbon than those that formed the Fe-Ti oxide-bearing rocks. Based on the estimated amounts of organic carbon in the two types of rocks, we deduced that initially oxidized magma pulses may have been reduced in variable degrees, leading to the formation of composite Ni-Cu sulfide and Fe-Ti oxide mineralization in one intrusive body. Mafic magmas in subduction-related, convergent margin settings are commonly highly oxidized due to metasomatism of the mantle wedge by slab-derived fluids/melts, and this may explain why the mafic-ultramafic intrusions associated with composite Ni-Cu sulfide and Fe-Ti oxide mineralization often occur in convergent margin settings. [ABSTRACT FROM AUTHOR]

The timing of deformation within and adjacent to the Helena salient of west-central Montana is poorly constrained relative to other segments of the Sevier fold-and-thrust belt. This study presents low-temperature thermochronology data from the Little Belt Mountains, a basement-cored Laramide uplift that is juxtaposed with the leading edge of the salient. We analyzed eight samples of Paleoproterozoic basement for apatite fissiontrack (AFT) and zircon (U-Th)/He (ZHe) thermochronology. Four samples yielded AFT ages ranging from ca. 80 Ma to 73 Ma and associated long, unimodal confined track lengths, indicating rapid cooling and exhumation of Little Belt Mountains basement during the Late Cretaceous. The other four samples are characterized by younger AFT ages (ca. 55 Ma), which suggest a combination of prolonged residence in the apatite partial annealing zone and postexhumation magmatic reheating. In total, 20 new ZHe dates range from ca. 236 Ma to 28 Ma and show a correlation between date and effective uranium. Forward model results for ZHe data are consistent with upper-crustal residence during the Proterozoic followed by Phanerozoic burial and rapid Late Cretaceous cooling. Cross sections across the Little Belt Mountains display the geometry of the Volcano Valley fault zone, an array of down-to-the-south Proterozoic normal faults that profoundly influenced the development of the Cordilleran thrust belt. Our new constraints from the Little Belt Mountains when integrated with published kinematic constraints from the Helena salient reveal significant out-of-sequence deformation in this portion of the thrust belt between ca. 80 Ma and 55 Ma. A kinematic model is proposed that involves Late Cretaceous (ca. 80 Ma) exploitation of rheologically incompetent units at the base of the Belt Supergroup within the Helena Embayment, facilitating early exhumation in the Little Belt Mountains. Our new data and synthesis are consistent with previous interpretations in which an inherited stratigraphic and structural architecture of Proterozoic ancestry was the predominant control on the development of the Helena salient during Cretaceous-early Eocene time. [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]

To understand the orogenic cyclicity that built the northern Yili magmatic arc in the southern Balhkash-Yili arc of the Central Asian Orogenic Belt, we synthesize its tectono-magmatic processes using new and existing U-Pb geochronological dates (228), Hf-in-zircon (1605 spots), bulk-rock geochemical data (1458), and Sr-Nd isotopic analyses (461) of magmatic rocks. Based on temporal-spatial distribution of magmatic rocks and their geochemical composition, four magmatic episodes (ca. 470-440 Ma, 420-380 Ma, 350-320 Ma, and 300-260 Ma) punctuated by a magmatic gap (ca. 440-420 Ma) and two high-flux magmatic pulses (ca. 380-350 Ma and 320-300 Ma) were recognized. These episodic magmatic processes are proposed to be dynamically associated with changes in configuration of the subducted Junggar oceanic slab, including 470-440 Ma initial subduction, 440-420 Ma flat subduction, 420-380 Ma retreating subduction, 380-350 Ma advancing subduction, and 350-320 Ma retreating subduction, followed by slab break-off in ca. 320-300 Ma and subsequent lithospheric delamination in a postcollisional setting during the Permian (ca. 300-260 Ma). In addition, tectonic transition (ca. 380 Ma and 320 Ma) from extension to compression were suggested to be closely related to the two phases of porphyry Cu mineralization events in the Balkhash-Yili arc. High crustal thickness and more mature arc evolution with prominent crust-mantle interaction may be responsible for the significant porphyry Cu endowment in the northern Balkhash-Yili arc. [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]

Transpressional shear zones commonly occur in ancient and modern convergent plate boundaries to accommodate oblique plate convergence. The early Paleozoic Qilian orogen in northeastern Tibet records the subduction of Proto-Tethyan Ocean lithosphere and the accretion-collision of various magmatic arcs and continental terranes. This study focused on the Datong ductile shear zone, which represents the central part of the WNW-ESE-striking ductile shear zone along the northern margin of the Qilian block in the Qilian orogen. This structure bears key information about the evolution of oblique convergence during the early Paleozoic orogeny. The kinematics and timing of the Datong ductile shear zone were investigated via fieldbased, microstructural, and mica 40Ar/39Ar dating analyses. Mesostructural and microstructural data showed predominantly dextral strike-slip shearing within the Datong ductile shear zone. Microstructural features and quartz c-axis crystallographic preferred orientation patterns indicated that dextral ductile shearing occurred under lower-amphibolite-facies conditions (~500-550 °C and ~5.6 kbar) within the shear zone. Microstructures of quartz showed subgrain rotation (SGR) and grain boundary migration (GBM), suggesting dislocation creep-dominated deformation. A strain rate of 10-12 s-1 and a differential stress of 25-39 MPa were estimated by the rheological flow law and quartz paleopiezometry. Finite strain measurements indicated that all deformed rocks of the Datong ductile shear zone exhibit a weakly oblate ellipsoid near the plane strain. Kinematic vorticity (ranging 0.47-0.83) analysis suggested the coexistence of simple shear and pure shear strains within the Datong ductile shear zone, indicating a transpressional setting. Biotite and muscovite 40Ar/39Ar data showed that transpressional shearing deformation started in the Ordovician (before 453 Ma) and lasted to the Silurian (ca. 430 Ma). Our new data combined with regional geological data show that the deformation type, kinematics, and dynamics of the Datong ductile shear zone were controlled by the southward oblique subduction of the Paleo-Qilian Ocean (Proto-Tethyan Ocean) and the following oblique collision between the Qilian block and the Alxa block. The intensive transpressional deformation along the northern Qilian block may reflect strong coupling between the subducting Paleo-Qilian oceanic slab and the overriding Qilian block as well as a high degree of convergence obliquity during the ongoing early Paleozoic convergence. [ABSTRACT FROM AUTHOR]

Lamprophyres are spatially and temporally widespread in continental belts, but their magmatic differentiation process and melting dynamic mechanisms remain subjects of debate. In this study, we report mineral chemistry, bulk-rock compositions, and Sr-Nd-O isotopes of the alkaline lamprophyres (including monchiquite and camptonite) from the Tuoyun Basin of the southwestern Central Asian Orogenic Belt. Based on the P-T estimates, transcrustal magmatic reservoirs from the lower crust to upper crust are revealed for monchiquite and camptonite. These magmatic reservoirs were potentially connected, and the magmatic recharge and mixing processes that occurred were recorded by zoned clinopyroxene and amphibole. The diverse crystal populations are suggested to have originated from multiple batches of magmas, which were then involved in forming the subsequent magmas. The Sr-Nd isotopic compositions are relatively depleted, with (87Sr/86Sr)i = 0.70390-0.70452 and εNd(t) = 5.46-6.49 for the monchiquite, while the values for camptonite are 0.70391-0.70463 and 4.71-5.02. Moreover, the olivine in situ O isotopes in the monchiquite show Î'18OV-SMOW values of 4.81‰-5.40‰, which are comparable to those of the mantle peridotite. Compared with the experimental melts, a hybridized mantle source of hydrous peridotite + silica-depleted pyroxenite is proposed, and partial melting of this component was induced by the upwelling asthenosphere. Ultimately, our study highlights the critical role of the magmatic plumbing system and hydrous mantle source in the formation of Tuoyun lamprophyres. [ABSTRACT FROM AUTHOR]

A big mantle wedge (BMW) is defined as the broad region of upper mantle above a stagnant slab in the mantle transition zone (MTZ). It is a common and significant structure within Earth's interior at modern convergent plate margins as revealed by seismic data yet rarely identified in fossil convergent systems. We propose the existence of a BMW beneath the Western Mongolia Collage during the early to middle Paleozoic based on a comprehensive chronology of geological events that characterized the accretionary orogen in this region. The trench-arc system initially developed above a NE-dipping subduction zone, with subduction-related arc magmatism clustered at ca. 530-490 Ma and accumulations of flysch-like sequences from the Cambrian to early Silurian constituting the accretionary wedge of the Altai Zone. The westward migration of the arc was likely driven by slab rollback and trench retreat, leading to gradual formation of a BMW as the slab stagnated at the MTZ. The BMW influenced the tectonic evolution of the entire Western Mongolia Collage, inducing Ordovician--Silurian intraplate magmatism in regions inboard of the migrating magmatic arc and the potential opening of the Mongol-Okhotsk Ocean. Westward movement of the trench-arc continued until the Devonian, resulting in back-arc basin formation in the Chinese Altai and intraplate magmatism in the Hovd and Lake Zones of the Western Mongolia Collage, forming a trench--arc--back-arc and intraplate tectonic system. Mantle flow within the BMW is inferred to have impacted magmatism, basin migration, and the stress and thermal state of the overriding plate. [ABSTRACT FROM AUTHOR]

Metallogenic models of polyphase mountain belts critically rely on robust geochronology. We combine petrology with Rb--Sr and U--Th--Pb in situ geochronology, paired at thin-section scale, to date mineralization in deformed hydrothermal Pb--Zn--Ag deposits along an east-west transect in the Western Alps, France. The Pb--Zn--Ag veins occur in shear zones with kinematic structures consistent with the mylonitized host rocks. The ore consists mainly of galena in a quartz-phengite gangue. The paragenesis can be related to hydrothermal crystallization during periods of variable strain. Both isotope systems yield only Cenozoic ages (ca. 35 Ma and 15-20 Ma) without any pre-Alpine inheritance, clearly indicating orogenic mineralization. The metallogenic model proposed here includes significant fluid circulation along major tectonic contacts between basement and sedimentary cover during Alpine convergence. [ABSTRACT FROM AUTHOR]

Dating of igneous rocks from paleo-island arc complexes of orogenic belts makes it possible to determine the precise timing of subduction processes that occurred during the formation of the orogen. Within the central (East Transbaikal) part of the Mongol–Okhotsk orogenic belt, the Kamenka island-arc terrane is an example of such a complex. Its intrusive part is included into the Bereya complex, represented by a gabbro-diorite-tonalite-plagiogranite series of rocks demonstrating subduction geochemical characteristics. The dating of zircons from acidic rocks of this complex by the U–Pb classical method showed that they were formed in a narrow time interval of 203 ± 1–205 ± 1 Ma, which corresponds to the Norian–Rhaetian boundary of the Late Triassic. Taking into account the previously obtained age of the diorites (254 ± 5 Ma), the timing of formation of the entire series of the intrusive rocks is about 50 Ma, thus indicating the probable subduction along the northern (in modern coordinates) margin of the Mongol–Okhotsk Paleocean under the Siberian paleocontinent in the Late Permian – Late Triassic. The diorites of the first phase have positive values of εND(254 Ma) = 3.2–3.6 (TNd(DM) = 879–994 Ma), and the plagiogranites have ɛND(205 Ma) = 2.3–3.5 (TNd(DM) = 859–1028 Ma), which points to the relationship between these rocks and the substance of the depleted mantle source and is consistent with the Sm–Nd isotope characteristics of the juvenile crust of the Central Asian orogenic belt. [ABSTRACT FROM AUTHOR]

The Yulekenhalasu porphyry Cu-Mo deposit (0.2 Mt Cu at 1.04 wt% and 0.012 Mt Mo at 0.06 wt%) is located in the Devonian Halasu copper belt, East Junggar block, northwest China. At Yulekenhalasu, Cu and Mo mineralization commonly occurs as disseminated sulfides or veinlets in porphyry-related alteration zones. Five alteration stages have been identified, including porphyry-type alteration, i.e., sodic-calcic (stage I), potassic (stage IIa), propylitic (stage IIb), and phyllic (stage III) alteration, and widespread late Cu sulfide-bearing veins (stage IV) cross-cutting porphyry-type alteration, plus a post-ore fault-controlled argillic alteration (stage V). Stages IV and V have overprinted porphyry-type alteration (stages I–III). Anomalous concentrations of trace elements in stage IIb pyrite (e.g., Ti, Zr, Gd, and Hf) are due to the presence of micro-inclusions (e.g., zircon and rutile) in the low-temperature (~200 °C) propylitic zone. Cu, Ag, Co, and Mn, occurring as stoichiometric substitutions or as tetrahedrite inclusions in overprinting stage IV pyrite, were sourced directly from the primary hydrothermal fluid. The enrichment of distal pathfinder elements (e.g., Cr, Au, and Tl) in overprinting stage V pyrite was caused by a low-temperature (~160 °C) hydrothermal event related to regional orogenic Au mineralization. The spatial variation of Se/S in pyrite among various paragenetic stages were influenced by changes in the hydrothermal fluid composition and temperature, with the latter having the effect of decreasing pyrite Se/S. Lower Se concentrations in pyrite of stages IIb and III close to the orebody are explained by relatively higher temperatures in the locus of mineralization. This may provide a potential vectoring tool to mineralization using pyrite geochemistry in porphyry deposits. Systematic thermodynamic calibrations were applied to pyrite compositions to fingerprint the corresponding Se/S and Co/Ni ratios of fluids and further to develop a complete metallogenic model for Yulekenhalasu. The Devonian diorite porphyry generated fluids that produced the early porphyry-type alteration. High Co/Fe (average ~1 × 10–4) and Ni/Fe (average ~3 × 10–6) ratios of fluid for late Cu sulfide-bearing veins, combined with higher Se/S (average ~6 ×x 10–7) than orogenic Au deposits (average ~3 × 10–8), indicate that the fluids possibly derived from a Late Devonian-Carboniferous mafic intrusion. Argillic alteration assemblages forming at ca. 280 Ma host pyrite relatively enriched in Au (average 0.1 ppm, with native gold inclusions). Therefore it is likely related to a regional orogenic gold mineralizing event in the Early Permian that overprinted Devonian mineralization. Although spatially contiguous, hydrothermal alteration and hypogene mineralizing stages identified herein represent discrete episodes of hydrothermal activities at Yulekenhalasu. The multi-stage alteration features observed at Yulekenhalasu may provide insights into the complete evolutionary history of Paleozoic porphyry Cu deposit systems in the Central Asian orogenic belt. This study contributes to a better understanding of the metallogenic and exploration models of porphyry Cu deposits overprinted by multi-stage hydrothermal events, which is economically important in Phanerozoic orogenic belts. [ABSTRACT FROM AUTHOR]

The central Inner Mongolia, located at the intersection of the northern margin of the North China Craton (NCC) and the Central Asian Orogenic Belt, is crucial for deciphering the Late Palaeozoic tectonic evolution associated with the subduction and closure of the Palaeo‐Asian Ocean (PAO). Our study focused on petrology, detrital zircon LA–ICP–MS U–Pb geochronology and whole‐rock geochemistry for the Late Carboniferous to Permian sandstones within the Shuanmazhuang, Dahongshan, Naobaogou, and Laowopu formations in Siziwang Banner, central Inner Mongolia. This comprehensive analysis shed light on the dynamic interplay between the NCC and the South Mongolia Block. Detrital zircon U–Pb ages in investigated samples mainly cluster between 250 and 2650 Ma, with significant peaks at 2.4–2.5 Ga, 1.8–2.0 Ga, 400–430 Ma, and 250–320 Ma, respectively. The geochemistry data are characterized by SiO2 contents (56.29–77.95 wt. %), Na2O / K2O ratios (0.45–1.58) and SiO2/Al2O3 ratios between 4.33 and 7.44. Moreover, they exhibit the slight enrichment in large ion lithophile elements (Rb and Ba) and the depletion in high field strength elements (Nb, Ta, Th, and U). These facts indicate that the sedimentary detritus predominantly originates from felsic sources, probably deriving from the Late Carboniferous–Permian continental island arc‐related intermediate‐acid igneous rocks, the Late Ordovician‐Silurian magmatic rocks in the Bainaimiao arc and the basements of the NCC. Furthermore, our present results also suggest that during the Early–Middle Permian, accelerating oceanic crust subduction triggered significant magmatic events in Siziwang Banner, leading to rapid uplift and the erosion of arc magmatic rocks, as well as the abundant corresponding sediments. Subsequently, the gradual convergence and eventual collision between the NCC and the Southern Mongolian Block took place at the end of the Permian, representing final closure of the PAO. [ABSTRACT FROM AUTHOR]

The tectonic deformation reaction to multi‐plate convergence in the northern Guizhong Depression, as well as its geodynamic process, remain poorly understood. Two phases of intracontinental deformation are identified using field geological investigations, paleo‐stress inversion and seismic reflection sections: (1) early NE–SW‐directed compression during the Middle Triassic to Early Jurassic; (2) later NW–SE‐directed compression during the Middle Jurassic to Early Cretaceous. The reconstruction of paleo‐stress provides robust constraints on the spatiotemporal evolution of stress within the Guizhong Depression. The regional SW–NE‐directed compression during the Middle Triassic to Early Jurassic was driven by the collision and convergence between the Indochina and South China blocks, resulting in the formation of NW–SE‐directed compressional structures during the Indosinian Period. The later SE–NW‐directed paleo‐stress field was probably driven by the NW‐directed subduction of the Paleo–Pacific Plate during the Middle Jurassic to Early Cretaceous. [ABSTRACT FROM AUTHOR]

The Sulu orogenic belt, formed by the collision between Sino‐Korean and South China blocks, has important geological implications due to its unique tectonic setting. To understand the deep crustal structure of the extension of the Sulu orogenic belt in the Yellow Sea, we presented a 220‐km long active‐source ocean‐bottom seismometer wide‐angle reflection/refraction profile across the Yellow Sea. The obtained P‐wave velocity structure exhibits significant horizontal and vertical variations. The middle and upper crustal regions of the north beneath the survey line exhibit a higher velocity and larger thickness than those of the south, whereas the opposite is the case with the lower crust. The lower crustal high‐velocity zone in the Northern Depression of the South Yellow Sea Basin is a manifestation of the mantle material upwelling and accretion to the lower crust. Magmatic intrusions occurred along the faults and formed a high‐velocity zone in the middle and upper crusts. Due to undulating Moho interface and varying crustal velocities, the Qingdao–Rongcheng fault is identified as a fault in the Sulu orogenic belt without the significance of tectonic zoning. This study shows that the Sino‐Korean Block, Sulu orogenic belt and South China Block are bounded by the Jimo–Muping faults (an extension to the sea), Qianliyan fault and deep fault of the South Yellow Sea. Furthermore, the Sulu orogenic belt may have been formed by the northward subduction of the South China Block beneath the Sino‐Korean Block during the Indosinian orogeny to the east of the Shandong Peninsula. [ABSTRACT FROM AUTHOR]

The Late Mesozoic lithospheric mantle evolution of the Jiaodong Peninsula is crucial for understanding the destruction of the eastern North China Craton (NCC) and large-scale gold mineralization, but it still remains highly controversial. Here, we comprehensively compiled published Late Mesozoic mafic dyke magmatism data from the Jiaodong Peninsula to provide key constraints on the nature and evolution of the lithospheric mantle. Mafic dykes are widely emplaced in the Jiaodong Peninsula and have been divided into two groups (Jiaobei terrane and Sulu orogenic belt); they mainly comprise lamprophyre, dolerite, and gabbro. The ages of the mafic dykes in the Jiaobei terrane are predominantly between 120 and 125 Ma, and those of the Sulu orogenic belt are between 110 and 120 Ma. The Jiaobei and Sulu mafic dykes both have high contents of Mg and compatible elements (Cr, Ni), as well as low SiO2 content; they are characterized by arc-like mafic magma, including enrichment in Large Ion Lithophile Elements and Light Rare Earth Elements, depletion in High Field Strength Elements, high (87Sr/86Sr)i, and low εNd(t), implying a metasomatized lithospheric mantle source. However, the Jiaobei mafic dykes have relatively higher (87Sr/86Sr)i, lower εNd(t), and a larger range of (206Pb/204Pb)i, (208Pb/204Pb)i, and (207Pb/204Pb)i compared with the Sulu mafic dykes. The Jiaobei and Sulu mafic dykes exhibit Ba/Rb ratios of 1.29‒64.39 (average 29.3) and 6.61‒108.28 (average 33.1), respectively, indicating the presence of hornblende in the melts. The high Fe/Mn (>60) and Zn/Fe (>12) ratios of Jiaobei and Sulu mafic dykes indicate the mixed mantle source of peridotite and pyroxenite. But the content of pyroxenite in the mantle source of Jiaobei terrane is higher with wider range of Fe/Mn and Zn/Fe ratios. These features indicate the heterogeneity of the mantle sources of the mafic dykes in the Jiaobei and Sulu regions. It is suggested that both regions originated from the partial melting of hornblende-bearing peridotite, with the addition of more pyroxenite to the mantle source of the Jiaobei terrane compared to Sulu orogenic belt. The mafic dykes have the low Nb/Zr (Jiaobei: 0.024–0.229; Sulu: 0.030–0.166) and Th/Zr ratios (Jiaobei: 0.017–0.081; Sulu: 0.010–0.068), and the high Rb/Y (Jiaobei: 0.347–12.162; Sulu: 0.224–9.600) and low Nb/Y ratios (Jiaobei: 0.202–1.486; Sulu: 0.140–1.322). It implies that the mantle source area in both regions was metasomatized by subducted slab-derived fluids. The increase in (La/Yb)N and decrease in Hf/Sm implies carbonate metasomatism in both regions. In addition, some Jiaobei and Sulu mafic dykes have high Ti/Eu ratios, implying that the silicate metasomatism occurred in the mantle source of both regions. Based on the regional evolution, the lithospheric mantle source in the two regions beneath Jiaodong Peninsula experienced carbonated fluid metasomatism resulting from the subduction of the Palaeo-Asian Ocean plate beneath the northern NCC (ca. ~250 Ma), silicate melt-related metasomatism from subduction of the Yangtze Craton plate beneath the southern NCC (ca. 240‒220 Ma), and oceanic slab-derived fluid metasomatism from the subducted Palaeo-Pacific plate (at 180‒110 Ma). It is believed that the mantle source of Jiaobei terrane had undergone stronger carbonated fluid metasomatism and silicate melt-related metasomatism, compared to Sulu orogenic belt. Moreover, the continental fluid-related metasomatism only occurred in the Sulu orogenic belt. During the Late Mesozoic, the eastern NCC experienced large-scale lithospheric thinning, leading to upwelling of the asthenospheric mantle. The mafic dykes in Jiaobei and Sulu, show different geochemical features, were derived from partial melting of the metasomatized lithospheric mantle through upwelling of the asthenospheric mantle. [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]

Located in the central part of the Central Asian Orogenic Belt, East Junggar represents one of the most important sites of juvenile crustal growth during the Phanerozoic. However, the mechanism of juvenile crustal growth during the Permian remains controversial. The Daheishan granites in the eastern segment of East Junggar are dated at ~292 Ma (Early Permian) and 269 Ma–267 Ma (Middle Permian). The Early Permian granites are coarse-grained with very high SiO2 (76.64 wt%–80.02 wt%), Al2O3 (10.72 wt%–12.96 wt%), and K2O/Na2O (1.27‒2.14), and low TiO2 (0.12 wt%–0.18 wt%), CaO (0.27 wt%–0.90 wt%), Mg# (25–32), and Sr/Yb (16–25). The Middle Permian granites are medium‒fine-grained with relatively high SiO2 (71.84 wt%–76.26 wt%), Al2O3 (11.26 wt%–13.00 wt%), and K2O/Na2O (0.53–1.54), and low TiO2 (0.17 wt%–0.21 wt%), CaO (0.37 wt%–3.20 wt%), Mg# (33–43), and Sr/Yb (5–9). These Permian granites display slightly positive whole-rock εNd(t) (+0.77 to + 1.04) and highly positive zircon εHf(t) (+7.3 to + 8.7) values, and low Ga/Al (2.04–2.55 < 2.6), P2O5 (0.02%–0.05% <0.14%), and zircon saturation temperature (690°C–749°C, take the median for each sample). Moreover, they display characteristic tetrad rare earth element patterns and non-CHARAC (CHArge-and-RAdius-Controlled) trace element behaviour, suggesting that the Daheishan granites are I-type granites that underwent both fractional crystallization (K-feldspar and plagioclase, e.g.) and crustal contamination prior to their emplacement. In combination with data from volcanic rocks in the Santanghu Basin, we infer that the Early Permian granitic magmas were derived from delamination of a thickened lithospheric mantle base and partial melting of pre-Permian arc components, while the Middle Permian granites formed during the subsequent stretching and thinning of the lithosphere. [ABSTRACT FROM AUTHOR]

The Komsomolsk tin-ore district is located along the Miao-Chan Ridge in the Middle Amur River area (Khabarovsk krai) within the Badzhal accretionary terrane of the Sikhote-Alin orogenic belt. This work presents new results of U–Pb zircon dating of tonalite from the Miao-Chan complex of the Silinka granite pluton (99.7 ± 1.1 Ma) and rhyolites of the lower part of the Kholdami Formation (98.4 ± 1.0 and 98.7 ± 1.2 Ma) from the northeastern part of the Komsomolsk district. The geochemical characteristics of the rocks studied show that granitoids of the Miao-Chan complex are I-type rocks and that synchronous rhyolites of the Kholdami Formation are highly aluminous and correspond to S-type rocks. New data on the composition and early Cenomanian age of the rocks make it possible to consider the ore-magmatic system of the Komsomolsk ore district as part of the previously identified Albian–Cenomanian igneous province of Pacific Asia. [ABSTRACT FROM AUTHOR]

The results of geological, geochemical, and isotopic–geochronological studies of Late Devonian granitoids of Rudny Altai, which formed at the Hercynian stage of tectonogenesis of the Altai–Sayan sector of the Central Asian Fold Belt, are presented. The isotopic U–Pb age of zircons ranges from 367 to 363 Ma. The geochemical characteristics indicate that leucogranites belong to high-K calc-alkaline series (SiO2 > 73 wt %, Na2O + K2O = 6.9‒9.0 wt %, and Na2O/K2O = 0.7‒1.2) of the calc-alkaline and alkali-calcic subtypes (MALI (modified alkali-lime index) = 6.32‒8.41). Rocks are close to saturation with silica (A/CNK = 0.9‒1.2) and are characterized by a high Fe* index (0.84‒0.97) and a higher F content (0.04–0.17 wt %). The variations in HSFE, LILE, and the Ga/Al ratios and a strong negative A/CNK–P2O5 correlation indicate that they belong to fractionated I-type granitoids. The Be mineralization is spatially and genetically related to leucogranites. It is suggested that the formation of granitoids was related to a synshear setting of a convergent margin as a result of oblique subduction or sliding tectonic plates of the Irtysh–Zaisan Ocean and the margin of the Siberian Continent. [ABSTRACT FROM AUTHOR]

The Aqishan-Caixiashan polymetallic ore cluster, located in the eastern Tianshan Orogenic Belt, is part of the southern Central Asian Orogenic Belt (CAOB) and experienced extensive tectono-magmatic events with polymetallic mineralization during the Carboniferous. However, the Carboniferous tectonic affinity and magmatic evolution of the ore cluster are still controversial, which limits further understanding of the tectonic evolution and regional metallogeny. With the aim of solving these problems, we have carried out geochronological and geochemical studies on Carboniferous intrusive rocks and volcanic rocks from the ore cluster. The samples of the Carboniferous magmatic rocks are enriched in LREEs and LILEs but depleted in HFSEs, which attest to the I-type affinity and are similar to those formed in a continental arc. The early Carboniferous granodiorites and granites (350–343 Ma) in the Central Tianshan Block (CTB), with high Mg# values of 37–66, low Y values of 2.3–17.2 ppm, and high Sr/Y ratios (34–85), show characteristics of adakites that are formed by partial melting of delaminated oceanic crust and/or lower crust. Additionally, they have a wide range of εHf(t) values (5.4–15.9), high εNd (t) values (1.78–6.31) and low ISr values (0.705–0.706), indicating a mixed source of depleted mantle and lower crust for its origin. The Late Carboniferous volcanic rocks (314–306 Ma) in the Aqishan-Yamansu Tectonic Belt (AYTB) north of the CTB have obviously negative Nb–Ta-Ti anomalies, as well as high Y contents (12–20 ppm) and low Sr/Y ratios (5.6–29.9) compared to primitive mantle, which has a relatively flat chondrite-normalized REE pattern, resembling arc-related magmas. Additionaly, they have positive values of εHf(t) values (8.7–14.7), high εNd(t) values (3.04–4.45) and low ISr ratios (0.704–0.707), showing a depleted mantle source, which is weakly affected by the contamination of ancient crustal material. Combining this study and previous works, we suggest that the continuous southwards subduction of the North Tianshan Ocean during the Carboniferous generated the continental arc and forearc basin in the northern part of the CTB. The expansion of the Aqishan-Yamansu forearc basin formed intrusions and volcanic formations along the arc belt. The early Carboniferous intermediate-felsic mantle-derived adakitic magmas in the CTB are probably related to regional Zn-Pb enrichment and mineralization, and the Late Carboniferous intrusions and volcanic formations in the AYTB are related to large-scale Fe-Cu-Zn-Pb-Ag mineralization. [ABSTRACT FROM AUTHOR]

This article presents the results of deep seismic studies over the Sikhote-Alin fragment of the 8-DV reference geophysical profile running across the large fold structures of the Pacific tectonic belt, that is, the Sikhote-Alin Orogenic Belt with the superimposed Middle Amur sedimentary basin and the East Sikhote-Alin volcanoplutonic belt. A deep seismic section of the Earth's crust and upper mantle with the distribution of longitudinal wave velocities is constructed. In the upper part of the section, P-wave velocities vary from 4.0–5.0 km/s within the Middle Amur sedimentary basin and the eastern part of the Eastern Sikhote-Alin volcanoplutonic belt to 5.5–5.6 km/s in the central part of the Sikhote-Alin Orogenic Belt. It was established that the thick Paleozoic sedimentary complex within the Middle Amur sedimentary basin is faulted and folded in a complex manner. Crystalline rocks with a compressional wave velocity of 6.0–6.2 km/s occur at depths from 8 to13 km in different parts of the Middle Amur sedimentary basin and at depths of 4–6 km within the Sikhote-Alin orogenic complex. Compressional wave velocities of the crust in the Sikhote-Alin fragment of the 8-DV profile are between 6.3 and 6.35 km/s. The crust varies in thickness from 32–34 km in the northern part of the fragment to 36–37 km in its central and eastern parts. Along the Moho, P-wave velocities are 8.1–8.3 km/s; a number of areas with reduced Vp of 7.8 to 8.0 km/s were identified in the junction zones of large crustal blocks. P-wave data were used to identify anomalies which were correlated with structural-tectonic zones, deep fault zones, and seismicity. The thick Middle Amur sedimentary basin was distinguished along the Central Sikhote-Alin deep fault. This basin is filled by Paleozoic low-velocity deposits and is displaced along the fault plane by 4–5 km at its junction with the Sikhote-Alin Orogenic Belt. Zones of increased heterogeneity in the upper crust projected onto the area within the contours of the Middle Amur sedimentary basin are characterized by increased seismicity. [ABSTRACT FROM AUTHOR]

The Mongol‐Okhotsk suture and the Adaatsag ophiolite belt are associated with the closure of the Mongol‐Okhotsk paleo‐ocean and are located within the Central Asian Orogenic Belt (CAOB) and Mongolia. The suture zone is flanked by volcanic‐plutonic belts that host significant metallogenic zones, containing deposits of copper and gold. The tectonic evolution of this region is not fully understood and the lithospheric structure has been poorly studied. We analyze magnetotelluric data and generate a model of the electrical resistivity distribution across this region. Whereas the northern segment has a sharp transition from a high‐resistivity upper crust to a low‐resistivity lower crust, as observed beneath the Hangai Dome, the southern segment does not show this transition. A wide, low‐resistivity zone (1–100 Ωm) imaged in the crust and lithospheric mantle is coincident with the Mongol‐Okhotsk suture and ophiolite, revealing a clear and significant lithospheric‐scale feature. Across the profile, numerous narrow, vertically oriented, low‐resistivity features (1–100 Ωm) are spatially associated remarkably well with the proposed boundaries of tectonic domains. These results confirm ideas about the development of the CAOB. Some of these low‐resistivity features are beneath the surface locations of large mineral zones, and likely represent fossil fluid pathways. We show congruent seismic velocity models for comparison and the results show a large‐scale low‐velocity anomaly (decrease of 2%–3%) that correlates with the location of the low‐resistivity anomaly below the Mongol‐Okhotsk suture. The geophysical results, combined with geological and geochemical data, provide insights into the structure of this region and help shed light on unanswered questions. Plain Language Summary: When the ancient Mongol‐Okhotsk ocean closed, due to subduction from tectonic re‐arrangement, it left the Mongol‐Okhotsk suture zone and the Adaatsag ophiolite as a trace of its location. Similarly, other tectonic boundaries are hypothesized to exist from terrane accretion across the Central Asian Orogenic Belt (CAOB) and Central and Southern Mongolia, which is located between the Siberian and North China cratons. This region is also rich in economically significant copper and gold deposits. The tectonic evolution of this region and especially the lithospheric structure is not fully understood and has been poorly studied. We analyze magnetotelluric data and generate a model of the electrical resistivity distribution. Additionally, we show models of the seismic velocity for comparison. Examining multiple complementary geophysical models helps to reduce interpretation uncertainty. Anomalies are observed in both models (e.g., low resistivity and low velocity). The suture zone is proven to be a strong lithospheric‐scale boundary. The proposed boundaries of tectonic domains are also imaged, confirming ideas about the development of the CAOB, and solving some controversies. Key Points: Lithospheric‐scale, wide, low‐resistivity zone revealed below the ophiolite belt associated with the closure of the Mongol‐Okhotsk oceanVertical, narrow low‐resistivity features aligned with proposed tectonic boundaries and locations of large mineral zones (copper and gold)The northern part of central Mongolia has a sharp mid‐crustal transition from high to low resistivity, whereas the southern part does not [ABSTRACT FROM AUTHOR]

Surface topography is an important yet largely neglected aspect of the early evolution of cratons. The lateral accretion of cratonic nuclei inevitably forms orogenic belts that subsequently provide a sediment source for large, resource‐rich intracratonic basins, but to date, geodynamic models have focused exclusively on lithospheric root processes. Here we use two‐dimensional thermal‐mechanical models to study the topography and lithospheric deformation during 50 Myr of compression of a cratonic nucleus, to simulate the lateral accretion phase of craton growth in the Neoarchean. Although the cratonic nucleus thickens slightly during the compression phase, most of the deformation occurs in the regions adjacent to the nucleus that have weaker lithosphere. Here, crustal thickness triples developing high topography in excess of 10 km without active erosion. Models with different initial rheological parameters will have different final topography and lithosphere geometry, but in general it is difficult to shorten and deform the depleted cratonic nucleus, unless there are significantly weak heterogeneities in the mantle lithosphere. We apply two quantitative analysis techniques to objectively evaluate a multitude of model outputs. Cross‐correlation clustering (CCC) measures the degree of similarity between topography profiles and categorizes models based on the general topographic character. Six different topography families are possible in the context of our models and crustal strength is the most important parameter affecting the shape. From principal component analysis (PCA) we identify four dominant lithosphere geometries. When used together, these two methods provide distinct yet complementary information about the surface and subsurface deformation features in our models. Plain Language Summary: Cratons, the ancient building blocks of continents, have existed on our planet, virtually unchanged, for the last 2 to 3 billion years. These regions contain the world's largest deposits of economic and precious metals, and they preserve the earliest evidence of life on Earth. The longevity of cratons is attributed to their unique chemical composition and structure that modern day plate tectonics is unable to reproduce. Therefore, understanding how cratons form may help unlock some of the mystery of Earth's early history. While many previous geodynamic studies on this topic have been published, the evolution of surface topography during craton formation via lateral compression has been ignored until now. We present 54 numerical models to test a wide range of initial conditions, showing that topographic relief is largely controlled by crustal strength. We also demonstrate how quantitative analysis techniques can effectively cluster models based on their large‐scale behavior and therefore aid in the interpretation of model results. Key Points: Quantitative clustering techniques effectively summarize results from numerous numerical models and facilitate objective comparisonSignificant surface topography formed during cratonic nuclei compression in supercontinent cycles is strongly controlled by crustal strengthHomogenous cratonic lithosphere is resistant to pure shear thickening when subjected to horizontal compression [ABSTRACT FROM AUTHOR]

This paper aims to update our understanding of the carbon cycle in the Himalayas, the most intense collisional orogeny globally, by providing new insight into its impact on Cenozoic climate cooling through the use of isotopic variations in both organic and inorganic carbon and an isotopic mass balance model. Our results from 20 selected hot springs show that the relative contributions of dissolved carbon from the mantle, metamorphic decarbonization, aqueous dissolution, and soil organic matter are approximately 2%, 82%, 6%, and 10%, respectively. Approximately 87% ± 5% of CO2 generated in the deep crust precipitates as calcite, while approximately 5.5% ± 1% of this carbon is converted to biomass through microbial chemosynthesis at depths less than 2 km. Our random forests approach yielded a metamorphic carbon flux from the entire Himalayan orogenic belt of approximately 2.7 ∼ 4.5 × 1012 mol/yr. The minor CO2 released into the atmosphere (2.5 ∼ 4.2 × 1011 mol/yr) is comparable to the carbon consumption driven by Himalayan weathering. This paper provides new insights into deep carbon cycling, notably that approximately 93% of deeply sourced carbon is trapped in the shallow crust, rendering orogenic processes carbon neutral and possibly acting as one of the major triggers of long‐term climate cooling in the Cenozoic. Plain Language Summary: Large‐scale deep metamorphic decarbonization and CO2 release into the atmosphere during continental collision orogenesis worldwide have had significant impacts on Cenozoic global climate change. However, the carbon sources and sinks and the mechanisms underlying their impacts on climate change are not fully understood. This paper reports the chemistry of aqueous solutions, carbon isotopic compositions of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC), and helium and carbon isotopic compositions of free gases from hot springs in southern Tibet. The carbon isotope fractionation model between gas and aqueous solutions revealed that the carbon released from depth underwent six different stages. Based on the random forests machine learning algorithm, we estimated the metamorphic carbon flux across the Himalayan orogenic belt. Furthermore, only a small fraction (7%) of deep carbon is eventually released into the atmosphere, and this volume is the same magnitude as the amount of carbon absorbed by silicate weathering on the Tibetan Plateau. This paper emphasizes that the carbon sequestration process in the upper crust may have resulted in nearly carbon‐neutral geological bodies in the Himalayan orogenic belt, thus playing a critical role in Cenozoic climate cooling. Key Points: Approximately 87% of deeply sourced carbon precipitates as calcite, while approximately 5.5% is sequestered as biomass in the shallow crustThe carbon flux across the Himalayan orogenic belt was estimated by the random forests approachCrustal thickening has attenuated long‐term deep carbon emissions from the Himalayas [ABSTRACT FROM AUTHOR]

This study integrates geophysical‐geochemical data to investigate the thermochemical structure of the lithosphere and sublithospheric mantle, along the Southern Tyrrhenian Basin, Apennines, Adriatic Sea, Dinarides, and Carpathians‐Balkanides. We present the lithospheric structure of the Adria microplate and the two opposing mantle slabs along its NE and SW margins. The modeling shows the presence of two asthenospheric mantle wedges aligning with the Apenninic and Dinaric continental mantle slab rollback, along with cold (−200°C) sublithospheric anomalies beneath Adria's NE and SW margins. In the northern Adria region, the lithosphere undergoes synchronous thinning in the Tyrrhenian domain and thickening toward the forefront of the northern Apennines. This is associated with the northeastward rollback of the SW Adriatic slab, leading to subsequent delamination of the continental mantle. In the southern Adria region, the complex deep structure results from the variably oriented lithospheric slabs, and nearly 90‐degree shift of the tectonic grain between the southern Apennines and the Calabrian Arc. At the SW Adria margin, beneath the northern Apennines, the thermal sublithospheric anomaly is attached to the shallower lithosphere, while a slab gap is modeled in the southern Apennines. One possibility is that the gap is due to a recent horizontal slab tear. Along the NE margin of Adria, the thermal anomaly penetrates to depths of about 200 km in the northern Dinarides and 280 km in the southern Dinarides, shallower than the SW Adria anomaly, which extends to at least 400 km depth. Plain Language Summary: We integrate geological and geophysical data (e.g., elevation, gravity, geoid, seismic tomography) to investigate the density and temperature distribution of the crust and lithospheric mantle down to 400 km, along a profile that extends from the Southern Tyrrhenian Basin and Apennines in Italy to the Southern Dinarides and Carpathians‐Balkanides in southern Europe. Taking advantage of our previous research in this region, we provide an integrated view of the lithospheric structure and the uppermost mantle of the Tyrrhenian Basin, Apennines, Adriatic Sea and Dinarides. Our results show notable variations in both the crust and the base of the lithosphere. These variations are observed to be shallower beneath the basins and deeper beneath the mountain belts, particularly in areas with elevated topography. Additionally, our observations highlight the presence of two cold and dense zones situated in the distal margins of the Adria microplate, specifically beneath the Apennines and Dinarides. The thermal anomalies indicate the presence of two oppositely subducting slabs with different geometries and depth of penetration. Their current location, depth and shape have largely controlled the geodynamic evolution of the study region in the last 30 My. Key Points: We unveil the thermochemical structure of the lithosphere and uppermost mantle of the Adria Microplate and its marginsResults reveal mantle wedges aligning with Apenninic and Dinaric slabs, and cold sublithospheric anomalies beneath NE and SW Adria marginsIn N Apennines the slab is attached while a gap is observed in S Apennines. At Adria's NE margin, the slab penetrates deeper southward [ABSTRACT FROM AUTHOR]

The Permian to Triassic period represents a pivotal phase in the evolution of the Paleo-Asian Ocean, marked by significant tectonic transitions from subduction, collision, and post-orogenic extension. The timing of closure of the Paleo-Asian Ocean in northeastern China has always been controversial. In this contribution, the petrology, zircon U-Pb geochronology and geochemistry are conducted on granite found in well HFD1, Songliao Basin, eastern part of Central Asian orogenic belt. Zircon U-Pb dating indicates that granite crystallized at 258.9 ± 2.2 Ma, as the product of magmatism occurred in the early Late Permian. The rocks have high SiO2, Al2O3, Na2O content, negative Eu anomaly, light enrichment of rare-earth elements, depletion of heavy rare-earth elements, high Sr (448.29–533.11 ppm, average 499.68 ppm), low Yb (0.49–0.59 ppm, average 0.54 ppm), Y (4.23–5.19 ppm, average 4.49 ppm), and high Sr/Y ratios (98–125, average 112) and can be classified as O-type adakite. This is the first discovery of late Paleozoic adakite in the Songliao Basin and the neighboring areas. The geochemistry of adakite indicates derivation by partial melting of MORB-type subducted oceanic crust, indicating that the subduction of the Paleo-Asian Oceanic lithosphere lasted until at least 258.9 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]

Petrographic descriptions and point counting data, supported by SEM analysis, are presented for 89 sandstone samples of the Khabour Formation from the Khabour, Ora, Chalki Nasara, and Chia Zinnar outcrop sections in northern Iraq. These are compared with previously published data for subsurface samples from the Akkas-1 and Akkas-3 wells in western Iraq. Petrographic observations revealed that sublitharenites and subarkoses form the main sandstone types and may suggest a granitic source region with minor input from metamorphosed sediments. This is supported by the geochemical analysis gained from 66 sandstone samples. Chemical Index of Alteration (CIA) and Index of Chemical Variability (ICV) values along with A-CN-K trends, and Th/U versus Th relationships suggest moderate weathering and humid climatic conditions in the source area. The paleoclimate geochemical proxies are supported by clay mineral associations revealed by XRD and SEM data. Up-section trends in Rb/Sr values imply that humid and dry conditions prevailed during the deposition of the Khabour succession. The Khabour Formation sandstones were deposited in a passive margin setting; however, their ultimate origin is likely to be recycled orogen and continental block provenances with sTable craton sources and with uplifting in the basement complexes. [ABSTRACT FROM AUTHOR]

Carbonate-bearing sediments, containing calcite, dolomite or magnesite as major carbonate components, are important constituents of sedimentary sequences deposited on passive margins through Earth's history. When involved in collisional orogenic processes, these sediments are metamorphosed at variable temperatures and pressures, and undergo decarbonation reactions. While the orogenic metamorphism of some of these lithologies (i.e. impure limestones and dolostones, marls sensu stricto and calcareous pelites) is relatively well understood, very little is known about the metamorphic evolution and decarbonation history of mixed carbonate–silicate rocks in which either dolomite or magnesite is the dominant carbonate component. Here we present the results of a petrologic study of representative samples of metasediments from Central Nepal, derived from Proterozoic dolomitic and magnesitic protoliths metamorphosed during the Himalayan orogeny. The main metamorphic assemblages developed in sediments originally containing different amounts of dolomite or magnesite are characterised in detail. Forward thermodynamic modelling applied to seven samples allows constraints to be placed on (i) the main decarbonation reactions, (ii) the P–T conditions under which these reactions took place, (iii) the composition of the fluids, and (iv) the amounts of CO2 released. We conclude that the CO2 productivity of dolomitic and magnesitic pelites and marls originally containing 15–40% carbonate is significant (>5.5 ± 1.0 CO2 wt% and up to 10.5 ± 1.5 CO2 wt%), whereas for carbonate contents above 60–70%, CO2 productivity is negligible unless aqueous fluids infiltrate from the outside and trigger decarbonation reactions. Since the dolomitic and magnesitic protoliths are significantly abundant in the sedimentary sequences involved in the still active Himalayan orogen, the decarbonation processes described here could contribute to the diffuse CO2 degassing currently observed at the surface. Furthermore, we propose for the first time that the peculiar magnesium-rich assemblages investigated in this study may derive from evaporitic protoliths, and that the whole Upper Lesser Himalayan Sequence may therefore represent the metamorphic product of a Proterozoic sequence consisting of alternating layers of carbonatic, evaporitic and pelitic sediments. [ABSTRACT FROM AUTHOR]

The Triassic granitoids in Central Tianshan play a key role in determining the petrogenesis and tectonic evolution on the southern margin of the Central Asian orogenic belt. In this study, we present SHRIMP zircon U‐Pb ages, Hf isotopic and geochemical data on the Xingxingxia biotite granite, amazonite granite and granitic pegmatite in Central Tianshan, NW China. Zircon U‐Pb dating yielded formation ages of 242 Ma for the biotite granite and 240 Ma for the amazonite granite. These granitoid rocks have high K2O with low MgO and CaO contents. They are enriched in Nb, Ta, Hf and Y, while being depleted in Ba and Sr, showing flat HREE patterns and negative Eu anomalies. They have typical A‐type granite geochemical signatures with high Ga/Al (8–13) and TFeO/(TFeO + MgO) ratios, showing an A2 affinity for biotite granite and an A1 affinity for amazonite granite and granitic pegmatite. Zircon εHf(t) values of the granitoids are 0.45–2.66, with Hf model ages of 0.99–1.17 Ga. This suggests that these A‐type granites originated from partial melting of the lower crust. We propose that Xingxingxia Triassic A‐type granites formed under lithospheric extension from post‐orogenic to anorogenic intraplate settings and NE‐trending regional strike‐slip fault‐controlled magma emplacement in the upper crust. [ABSTRACT FROM AUTHOR]

Post‐collisional magmatism contains important clues for understanding the reworking and growth of continental crust, as well as lithospheric delamination and orogenic collapse. Early Devonian magmatism has been identified in the North Qilian Orogenic Belt (NQOB). This paper reports an integrated study of petrology, whole‐rock geochemistry, Sm‐Nd isotope and zircon U‐Pb dating, as well as Lu‐Hf isotopic data, for two Early Devonian intrusive plutons. The Yongchang and Chijin granites yield zircon U‐Pb ages of 394–407 Ma and 414 Ma, respectively. Both of them are characterized by weakly peraluminous to metaluminous without typical aluminium‐rich minerals, LREE‐enriched patterns with negative Eu anomalies and a negative correlation between P2O5 and SiO2 contents, consistent with geochemical features of I‐type granitoids. Zircons from the studied granites display negative to weak positive εHf(t) values (–5.7 to 2.1), which agree well with those of negative εNd(t) values (−6.4 to −2.9) for the whole‐rock samples, indicating that they were derived from the partial melting of Mesoproterozoic crust. Furthermore, low Sr/Y ratios (1.13–21.28) and high zircon saturation temperatures (745°C to 839°C, with the majority being >800°C) demonstrated a relatively shallow depth level below the garnet stability field and an additional heat source. Taken together, the Early Devonian granitic magmatism could have been produced by the partial melting of ancient crustal materials heated by mantle‐derived magmas at high‐temperature and low‐pressure conditions during post‐collisional extensional collapse. The data obtained in this study, when viewed in conjunction with previous studies, provides more information about the tectonic processes that followed the closure of the North Qilian Ocean. The tectonic transition from continental collision to post‐collisional delamination could be constrained to ∼430 Ma, which is provided by the sudden decrease of Sr/Y and La/Yb ratios and an increase in zircon εHf(t) values for granitoids. A two‐stage tectonic evolution model from continental collision to post‐collisional extensional collapse for the NQOB includes (a) continental collision and crustal thickening during ca. 455–430 Ma, characterized by granulite‐facies metamorphism and widespread low‐Mg adakitic magmatism; (b) post‐collisional delamination of thickened continental crust and extensional collapse of orogen during ca. 430–390 Ma, provided by coeval high‐Mg adakitic magmatism, A‐type granites and I‐type granitoids with low Sr‐Y ratios. [ABSTRACT FROM AUTHOR]

The Ailaoshan Orogen in the southeastern Tibet Plateau, situated between the Yangtze and Simao blocks, underwent a complex structural, magmatic, and metamorphic evolution resulting in different tectonic subzones with varying structural lineaments and elemental concentrations. These elements can conceal or reduce anomalies due to the mutual effect between different anomaly areas. Dividing the whole zone into subzones based on tectonic settings, ore cluster areas, or sample catchment basins (Scb), geochemical and structural anomalies associated with gold (Au) mineralization have been identified utilizing mean plus twice standard deviations (Mean + 2STD), factor analysis (FA), concentration‐area (C‐A) modeling of stream sediment geochemical data, and lineament density in both the Ailaoshan Orogen and the individual subzones. The FA in the divided 98 Scbs with 6 Scbs containing Au deposits can roughly ascertain unknown rock types, identify specific element associations of known rocks and discern the porphyry or skarn‐type Au mineralization. Compared with methods of Mean + 2STD and C‐A model of data in the whole orogen, which mistake the anomalies as background or act the background as anomalies, the combined methods of FA and C‐A in the separate subzones or Scbs works well in regional metallogenic potential analysis. Mapping of lineament densities with a 10‐km circle diameter is not suitable to locate Au deposits because of the delineated large areas of medium‐high lineament density. In contrast, the use of circle diameters of 1.3 km or 1.7 km in the ore cluster scale delineates areas with a higher concentration of lineament density, consistent with the locations of known Au deposits. By analyzing the map of faults and Au anomalies, two potential prospecting targets, Scbs 1 and 63 with a sandstone as a potential host rock for Au, have been identified in the Ailaoshan Orogen. The use of combined methods in the divided subzones proved to be more effective in improving geological understanding and identifying mineralization anomalies associated with Au, rather than analyzing the entire large area. [ABSTRACT FROM AUTHOR]

Identification and anatomy of oceanic arcs within ancient orogenic belt are significant for better understanding the tectonic framework and closure process of paleo‐ocean basin. This article summarizes the geological, geochemical, and geochronological characteristics of upper crust of Proto‐Tethyan Lajishan intra‐oceanic arc and provides new data to constrain the subduction evolution of the South Qilian Ocean. The intra‐oceanic arc volcanic rocks, including intermediate–mafic lava, breccia, tuff, and minor felsic rocks, are distributed along southern part of the Lajishan ophiolite belt. Geochemical and isotopic compositions indicate that the intermediate–mafic lava were originated from depleted mantle contaminated by sediment melts or hydrous fluids, whereas the felsic rocks were likely generated by partial melting of juvenile mafic crust in intra‐oceanic arc setting. Zircons from felsic rocks yield consistent and concordant ages ranging from 506 to 523 Ma, suggesting these volcanic rocks represent the relicts of upper crust of the Cambrian intra‐oceanic arc. Combined with the Cambrian forearc ophiolite and accretionary complex, we suggest that the Cambrian intra‐oceanic arc in the Lajishan ophiolite belt is belonging to the intra‐oceanic arc system which was generated by south‐directed subduction in the South Qilian Ocean at a relatively short interval between approximately 530 and 480 Ma. [ABSTRACT FROM AUTHOR]

The Shangdan suture zone (SDZ) in the Qinling orogenic belt (QOB) is a key to understanding the East Asia tectonic evolution. The SDZ gives information about convergent processes between the North China Block (NCB) and South China Block (SCB). In the Late Mesozoic, several shear zones evolved along the SDZ boundary that helps us comprehend the collisional deformation between the NCB and SCB, which was neglected in previous studies. These shear zones play an essential role in the tectonic evolution of the East Asia continents. This study focuses on the deformation and geochronology of two shear zones distributed along the SDZ, identified in the Shaliangzi and Maanqiao areas. The shear sense indicators and kinematic vorticity numbers (0.54–0.90) suggest these shear zones have sinistral shear and sub-simple shear deformation kinematics. The quartz's dynamic recrystallization and c-axis fabric analysis in the Maanqiao shear zone (MSZ) revealed that the MSZ experienced deformation under green-schist facies conditions at ∼400–500 °C. The Shaliangzi shear zone deformed under amphibolite facies at ∼500–700 °C. The 40Ar/39Ar (muscovite-biotite) dating of samples provided a plateau age of 121–123 Ma. Together with previously published data, our results concluded that QOB was dominated by compressional tectonics during the Late Early Cretaceous. Moreover, we suggested that the Siberian Block moved back to the south and Lhasa-Qiantang-Indochina Block to the north, which promoted intra-continental compressional tectonics. [ABSTRACT FROM AUTHOR]

Early Paleozoic magmatism in the West Kunlun Orogenic Belt (WKOB) preserves important information about the tectonic evolution of the Proto-Tethys Ocean. This paper reports whole-rock compositions, zircon and apatite U-Pb dating, and zircon Hf isotopes for the Qiaerlong Pluton (QEL) at the northwestern margin of WKOB, with the aim of elucidating the petrogenesis of the pluton and shedding insights into the subduction-collision process of this oceanic slab. The QEL is mainly composed of Ordovician quartz monzodiorite (479 ± 3 Ma), quartz monzonite (467–472 Ma), and syenogranite (463 ± 4 Ma), and is intruded by Middle Silurian peraluminous granite (429 ± 20 Ma) and diabase (421 ± 4 Ma). Zircon εHf(t) values reveal that quartz monzodiorites (+2.1 to +9.9) and quartz monzonites (+0.6 to +6.8) were derived from a mixed source of juvenile crust and older lower crust, and syenogranites (−5.6 to +4.5) and peraluminous granites (−2.9 to +2.0) were generated from a mixed source of lower crust and upper crust; diabases had zircon εHf(t) values ranging from −0.3 to +4.1, and contained 463 ± 5 Ma captured zircon and 1 048 ± 39 Ma inherited zircon, indicating they originated from enriched lithospheric mantle and were contaminated by crustal materials. The Ordovician granitoids are enriched in LILEs and light rare-earth elements, and depleted in HFSEs with negative Nb, Ta, P, and Ti anomalies, suggesting that they formed in a subduction environment. Middle Silurian peraluminous granites have the characteristics of leucogranites with high SiO2 contents (74.92 wt.%–75.88 wt.%) and distinctly negative Eu anomalies (δEu = 0.03–0.14), indicating that they belong to highly fractionated granite and were formed in a post-collision extension setting. Comparative analysis of these results with other Early Paleozoic magmas reveals that the Proto-Tethys ocean closed before the Middle Silurian and its southward subduction resulted in the formation of QEL. [ABSTRACT FROM AUTHOR]

The Weining Beishan area of Ningxia Hui Autonomous Region is located at on the western edge of the Helanshan tectonic belt, which is a tectonic joint among Alxa Block, Ordos Block, and North Qilian orogenic belt. However, the tectonic evolution of this area remains unclear due to the lack of magmatic information. This paper conducted researches on geochronology, geochemistry, and Sr-Nd-Hf isotopes of the diorite porphyrites exposed in the Weining Beishan area. The zircon U-Pb dating yields two ages of 145.0 ± 1.1 and 146.2 ± 1.5 Ma, and the whole-rock geochemical data indicate that the diorite porphyrites are metaluminous to weakly peraluminous and high-K calc-alkaline series. The characteristics of highly initial 87Sr/86Sr ratios (0.708 16 to 0.710 47), negative εNd(t) (−8.9 to −8.4), and negative εHf(t) (−13.8 to −21.2) indicate that the diorite porphyrites originated from partial melting of the middle-lower ancient crust related to the North China Craton. Combined with the regional geology, we suggested that partial melting was triggered by a tectonic activity of deep faults cutting through the crust under the regional stress transformation from compressing to extension during the Late Jurassic–Early Cretaceous, which is probably related to the westward subduction of the Paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

The Jiangsu-South Yellow Sea area is located on the East Asian Continental Margin and at the junction of South and North China. It is one of the high seismicity areas in eastern China. To enhance our understanding of the relationship between disastrous earthquakes and the geophysical properties of Earth materials, P- and S-wave travel-time data over the past 20 years are inverted to image the 3D distributions of seismic velocity (VP and Vs) and Poisson's ratio (σ). The results show that the velocity and Poisson's ratio demonstrate congruence with the prominent geological formations present within the study area. Specifically, the velocity models for the upper crust at depths of 5, 10, and 15 km. We found that within the total study area, 70% ± 7.2% of M5+ earthquakes that occurred during the past decades initiated in the VP tomographic edge zones (TEZ). Moreover, the distribution patterns of M5+ earthquakes in the offshore sea region exhibit significant differences when compared to those in the Jiangnan Orogenic Belt. In the offshore sea region, about 66.7% ± 8% of M5+ earthquakes initiated in the velocity and Poisson's ratio TEZ. The presence of comparatively low Vs and high Poisson's ratio anomalies in the Wunansha Uplift suggest the potential existence of fluids. The triggering mechanism for these earthquakes can likely be ascribed to the presence of hydrothermal fluids and the reactivation of preexisting strike-slip faults, influenced by the subduction of the Pacific and Philippine Sea Plates, as well as the collision between the India and Eurasia Plates. In contrast, within the Jiangnan Orogenic Belt, M5+ earthquakes predominantly initiated in the high-velocity and low Poisson's ratio perturbation zones. The primary factor contributing to seismotectonic features disparities are likely the variation in fluid content. We infer the rock matrix in the vicinity of the source region of the Jiangnan Orogenic Belt is presumed to be drier, more brittle, and possess greater mechanical strength. [ABSTRACT FROM AUTHOR]