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The identification of the Grenvillian‐age ophiolite suites in the Yangtze block in recent years suggested that the northern Yangtze subblock (NYB) and the southern Yangtze subblock (SYB) were once separated by an ocean in late Mesoproterozoic. Although some paleogeographic models advocated the Pre‐Grenvillian connections between the south China blocks and Laurentia, none of them has been paleomagnetically tested. Here we report the new paleomagnetic results obtained from the ∼1,270 Ma purplish‐red muddy dolomite beds of the Luanshigou Formation, Shennongjia Group, NYB, providing new constraints for reconstructing the paleogeographic positions of the south China blocks in late Mesoproterozoic. A total of 447 samples underwent stepwise thermal demagnetization. Two components were identified. The low‐temperature component is interpreted as the recent viscous remnant magnetization. The high‐temperature component was obtained from 64 samples below 580°C and from 177 samples below 690°C, directed northeast‐up or southwest‐down, antipodally, positioning the paleomagnetic pole at 18.5°S, 74.4°E (dm/dp = 2.5/1.6°). Rock magnetic results demonstrate that the magnetic carriers in purplish‐red dolomite and pale‐pink dolomite are predominated by hematite and magnetite, respectively. The data quality is supported by an inverse baked contact test, a B‐class reversal test, and the paleomagnetic pole is distinct from any younger poles of the region. Based on the paleomagnetic results, aided by geological evidence, we propose a reconstruction in which the NYB was juxtaposed to southwestern Laurentia in the late Mesoproterozoic and suggest that the late Mesoproterozoic Miaowan‐Shimian ophiolite zone in the Yangtze block was likely an extension of the Grenville belt of Laurentia. Plain Language Summary: The south China block was traditionally subdivided into the Yangtze block to the northwest and the Cathaysia block to the southeast, which were separated by an early Neoproterozoic ocean. Recently published geological data further suggest that the Yangtze block contains two subblocks, the NYB and the SYB, which were separated by a late Mesoproterozoic ocean. Several paleogeographic models proposed the Mesoproterozoic relationships between the south China blocks and Laurentia, but none has been paleomagnetically tested. Here we report a new paleomagnetic pole obtained from the ∼1,270 Ma purplish‐red dolomite beds of the Luanshigou Formation, Shennongjia Group in the NYB. The data quality is assured by the positive paleomagnetic field tests. Our results combing with the geological evidence suggest that the NYB was located in a low‐latitudinal position and connected to southwestern Laurentia in the late Mesoproterozoic. The late Mesoproterozoic ophiolite zone in the southern margin of the NYB was likely an extension of the Grenville belt. Key Points: A new paleomagnetic pole (18.5°S, 74.4°E, dm/dp = 2.5/1.6°) was obtained from the late Mesoproterozoic Luanshigou Formation of the Shennongjia Group in south ChinaThe northern Yangtze subblock (NYB) was connected to southwestern Laurentia at the late MesoproterozoicThe late Mesoproterozoic Miaowan‐Shimian suture zone in the southern margin of the NYB was likely an extension of the Grenvillian orogenic belt [ABSTRACT FROM AUTHOR]

The Sangong Cu-Ni sulfide mineralized mafic-ultramafic intrusion is located on the southern margin of the Bogeda-Harlik belt, eastern Tianshan, China. The intrusion is a well-differentiated complex and is comprised of leucogabbro, gabbro, olivine gabbro, Pl-bearing peridotite, and Pl-bearing pyroxenite. The Pl-bearing pyroxenite hosts both irregularly disseminated sulfide and round droplet sulfide. The intrusive rocks have a wide range of SiO2 (42.1 wt.%–50.48 wt.%) and MgO (6.21 wt.%–22.11 wt.%), and are enriched in light rare earth elements (LREE), large-ion lithophile elements (LILE; e.g., Rb, Ba, Sr, and Pb), and palladium platinum group elements (PPGE) but depleted in high-field-strength elements (HFSE; e.g., Nb, Ta, and Ti) and iridium PGEs (IPGE). These geochemical characteristics indicate that the Sangong mafic-ultramafic intrusion was derived from high degree of partial melting of depleted mantle and interacted with subduction-related material. The low Pd/Ir (3.21–27.44) but high Ni/Cu (1.64–24.16) ratios, combined with the olivine crystals with low Fo (60.88–78.65) and Ni (54.99 ppm–1 688.87 ppm) concentrations suggest that the parental magma of the Sangong intrusion were likely high MgO basaltic in composition that experienced extensive evolution prior emplacement. The Ce/Pb ratios (5.8–13.6) and Nb/U ratios (11.6–30.3) of the intrusive rocks all range between MORB and crustal values, the Nb/Yb and Th/Yb values are close to the lower crust values, together with the low Se/S ratios [(17–100) × 10−6)] suggest that the magma experienced assimilation not only in mantle source but also in conduit, but the degree of crustal contamination is limited. The Cu/Pd ratios of the rocks range from 3.9 × 104 to 10.8 × 104, and the Cu/Zr ratios of Pl-bearing pyroxenite in the Sangong intrusion are >1, combined with the presence of sulfide droplets in the Pl-bearing pyroxenite, indicating the parental magma experienced sulfide saturation and the economical ore bodies may present in the depth of the intrusion. Furthermore, given the discovery of the Baixintan and Yueyawan deposits, we propose the Dananhu-Harlik belt as an essential prospecting target for Cu-Ni mineralization in North Xinjiang. [ABSTRACT FROM AUTHOR]

Subduction erosion at convergent margins is a leading mechanism for the destruction (recycling and reworking) of continental crust. But because of the lack of direct evidence, it is not straightforward to identify erosive events and their intensities in fossil subduction zones. The Heilongjiang accretionary complex in northeastern China was formed during the early Mesozoic subduction of the Paleo-Pacific Ocean. We investigated amphibolites from this accretionary complex, whose protoliths (based on whole-rock trace elements and Sr-Nd-Hf isotopes) were mafic continental arc magmatic rocks (255-249 Ma; zircon core U-Pb ages) from the upper plate. Phase equilibria modeling constrained by mineral geochemistry indicates that the amphibolites and their wall rocks were first heated to low granulite facies (750-800 °C, ~7 kbar) at 251-244 Ma (zircon rim U-Pb ages) and then cooled to ~700 °C with increasing pressure (8-9 kbar) before 213-187 Ma (titanite and apatite U-Pb ages). To explain the occurrence of the lower arc crustal lithologies in the accretionary complex and their metamorphic history, we propose that the subducting plate strongly eroded the forearc crust, allowing the plate interface to advance landward and scrape the amphibolites and wall rocks formed under the old arc, which finally were exhumed along the subduction channel and became components of the complex. The case study exemplifies direct petrological evidence of strong subduction erosion occurring in an ancient orogen, thus implying that consumption of the entire forearc crust could occur within only ~50 m.y. [ABSTRACT FROM AUTHOR]

The subcontinental lithospheric mantle (SCLM) is now suggested by many workers to play a role in the formation of orogenic gold deposits in active continental margins, given that the gold and volatiles may be introduced into the SCLM during plate subduction. The giant Cretaceous Jiaodong gold province within the North China block occurs in a convergent margin setting where there is no terrane accretion, thus eliminating from consideration the commonly accepted metal and fluid source reservoir for orogenic gold--the metamorphosed upper crust of an active orogenic belt. Thus, the auriferous fluids were released below the high-grade Archean cratonic rocks from either enriched SCLM or directly from the subducted oceanic slab. Mercury (Hg) isotopes allow fingerprinting of isotopically distinct reservoirs, discriminating between the two possibilities. We present Hg isotope data for a set of pyrite grains, native gold, and lamprophyres from six main gold districts in the Jiaodong gold province. These samples dominantly yielded near-zero Δ199Hg (0‰ ± 0.1‰), within uncertainty of the mantle Δ199Hg value. The results provide novel evidence that the SCLM predominantly controlled the Hg budget of the Jiaodong gold deposits, implying that the SCLM acted as a buffer for the crustal mass-independent fractionation Hg signatures and a storage reservoir for gold and volatiles. Consequently, during slab subduction, gold and volatiles were recycled and stored within the SCLM and were later released from the mantle during uplift and relaxation of compressional tectonics. [ABSTRACT FROM AUTHOR]

High‐silica granitoids record the formation and evolution of the continental crust. A new intrusive complex has been recognized among silicic volcanic rocks of the Weixi arc, Southwest China. The intrusions consist of granites, granitic porphyries, and granodiorites. Zircon U‐Pb age data indicate that the Weixi granitoids formed at 248–240 Ma and were coeval with silicic volcanic rocks of the Weixi arc. The Weixi granitoids are enriched in Rb, Th, and U, depleted in Ba, Sr, Nb, Ta, and Ti, and have high light/heavy rare earth element ratios and slightly negative Eu anomalies. The Weixi granitoids have negative εNd(t) values (–9.8 to –7.8) and negative zircon εHf(t) values (–12.02 to –5.11). The geochemical and isotopic features suggest the Weixi granitoids were derived by partial melting of ancient crustal material. The Weixi granitoids and silicic volcanic rocks were derived from the same magma by crystal accumulation and melt extraction, respectively, and they record the formation of a continental arc in the central Sanjiang orogenic belt. [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]

The accurate reconstruction of the early Cambrian paleoclimate and paleoceanographic conditions on the Yangtze Plate is crucial for understanding the ancient environment during the Cambrian Explosion. It is also a key factor in understanding the ecological habits of organisms during the Cambrian Explosion. The study utilized field outcrops, thin section analysis, and major and trace elements to investigate the sedimentary environment, provenance, paleoweathering, and paleoclimate of the Lower Cambrian Hongjingshao (HJS) Formation (Cambrian Stage 3, ~515 Ma) in the Yangtze Basin, eastern Yunnan, SW China. The HJS sandstones are composed of 10 lithofacies, including massive and weakly bedded gravel supported by coarse sandstone (Gm), trough cross-bedded sandstone (St), planar cross-bedded sandstone (Sp), ripple cross-laminated sandstone (Sr), horizontal bedded sandstone (Sh), scour-fill sandstone (Se), massive sandstone (Sm), fine to medium sandstone with thin bed muddy siltstone (Fl), muddy siltstone (Fsc), and mudstone (Fm). On the basis of these lithofacies, channel fill and over-bank deposits in delta and shallow shelf depositional environments are suggested for HJS Formation. The major elements-based provenance discriminant function and mineral composition indicate that felsic rocks from the recycled orogen and continental block are the main sediment source terrane for the HJS sandstones of the study area. CIA, PIA, and CIW values range from 71.29 to 93.72, indicating an intermediate to intense chemical weathering and semiarid to humid climate conditions in Cambrian Stage 3. The research findings have clarified the paleoclimate and paleoceanographic environment of the Early Cambrian in the Yangtze region, which is of significant importance for understanding the early biological and ecological marine environment in the study area. [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]

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]

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]

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]

Plume-derived high-MgO lavas provide important information on the lithological, thermal and chemical variations of Earth's deep mantle. Here we present results from detailed field, mineralogical and geochemical studies of Late Permian–Late Triassic high-MgO lavas near the Chalukou area in the Western Kunlun (WK) orogenic belt, NW China. The major element compositions of the lavas show extremely high MgO contents (26.6–33.8 wt %) in accordance with olivine accumulation. The parental magma is inferred to be picritic in composition with MgO of 17.2 ± 0.9 wt %. Olivine Zn/Fe and Mn/Zn ratios suggest a peridotite-dominated source with a minor fraction of pyroxenite. The temperature and oxygen fugacity estimates based on multi-methods including olivine-melt Mg–Fe equilibria, Al-in-olivine and olivine–spinel thermometry and oxybarometer yield a mantle potential temperature of 1522–1556 °C and high oxygen fugacity of FMQ (fayalite-magnetite-quartz) + 0.93. The H2O contents in the picrite flows are estimated as 3.67 ± 1.0 wt %, indicating the volatile-rich nature of parental magma and its mantle source. The immobile trace element features show that the WK picrites are OIB (oceanic island basalt)-like, with the enrichment in light rare earth elements and positive Nb, Ta, Zr and Hf anomalies. Furthermore, the Nd–O–Os isotopes display typical mantle values without involvement of recycled materials. Our results suggest the high-MgO volcanism in the WK orogenic belt originated from a volatile-rich plume source. [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]

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 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]

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 complex evolutionary history of the Qinghai-Tibetan Plateau and its surrounding areas, including the continental blocks (Indian, Lhasa, South Qiangtang, Tarim, Olongbuluk, Central Qilian, Alxa, North China, Yangtze, Central Iran and Oman) and the orogenic belts between them, has long been the frontier in Earth science research. The Cryogenian and Ediacaran strata are extensively distributed in these blocks. Specifically, relatively complete Cryogenian and Ediacaran successions have been discovered in Oman, Indian, Yangtze, and Tarim blocks, while only the Ediacaran successions have been reported in Iran, the South Qiangtang, Central Qilian, Alxa, and North China blocks. Based on previous studies together with the integration of new materials and advancement obtained through the Second Tibetan Plateau Scientific Expedition and Research, this review aims to synthesize a correlative stratigraphic framework of the representative Cryogenian and Ediacaran sequences from the Qinghai-Tibetan Plateau and its surrounding areas. Furthermore, the Cryogenian and Ediacaran biotas and major geological events in these areas are comprehensively discussed in aspects of current research status. The results indicate that, in general, Ediacaran fossils of each area exhibit distinct features in preservation and assemblage composition, but the typical late Ediacaran fossils Cloudina and Shaanxilithes have been reported from most of these areas. In addition to the two global Cryogenian glaciations, late Ediacaran glaciogenic deposits are extensively recorded in the areas within and around the northern Qinghai-Tibetan Plateau (including the North China, Alxa, Central Qilian, Olongbuluk, and Tarim blocks, and the North Qilian Accretionary Belt), as well as central and southern Iran. However, further research is required to determine the age, distribution, and origin of these late Ediacaran glaciogenic deposits. Meanwhile, the middle Ediacaran DOUNCE/Shuram Excursion is widely documented in the Qinghai-Tibetan Plateau and its surrounding areas. The available data show that, after the break-up of the Rodinia supercontinent, most of the continental blocks in the areas were located along the northern margin of East Gondwana and a few (such as North China) were located between the Gondwana and Laurentia. In general, the paleogeographic evolution of most of these blocks during the Cryogenian and Ediacaran remains disputatious, necessitating further research to resolve the controversies surrounding their paleogeographic reconstruction models during this critical time interval. [ABSTRACT FROM AUTHOR]

The Dulate arc, located in East Junggar (NW China) in the southern Central Asian orogenic belt, records a Devonian magmatic arc evolution, offering a window to understanding the orogenic processes of the Central Asian orogenic belt. Here we present new geochemical and isotopic data for Late Devonian high-Mg andesite (HMA) and Nb-enriched basalt (NEB) suites from the Qiakuerte area, East Junggar. The HMA samples are typical subduction-related volcanic rocks. They have SiO2 contents ranging from 53.30 to 54.59 wt%, high MgO (5.0-5.26 wt%), and high Mg# values (~55) and show enrichments in large ion lithophile elements (LILEs) and depletions in high field strength elements (HFSEs). The HMA samples have high (La/Yb)N ratios and Sr/Y (~6.5 and 50-59, respectively) with no Eu anomalies. The HMA samples have high Na2O (~3.3 wt%) and low K2O (~2.5 wt%) and Th (~2.4 ppm) contents, combined with positive εNd(t) and low (87Sr/86Sr)i values. These characteristics suggest that the samples were formed mainly through interactions between subducted oceanic melts and mantle peridotites. Compared to normal arc basalts, the NEB samples have higher concentrations of Nb (~20 ppm), higher primitive mantle-normalized Nb/La (0.50-0.58), and higher ratios of Nb/U (9.4-14.6). The NEB samples also have positive εNd(t) and low (87Sr/86Sr)i values, indicating that their source was mantle wedge that had been metasomatized by slab melt. Considering the widespread presence of A-type granites, the abnormally high heat flow, and the tectonic characteristics of East Junggar, we conclude that a slab window created by the subduction of an ocean ridge was responsible for the melting of slab and the formation of the NEB-HMA suites. These processes may have also played a key role in the tectonic evolution processes of East Junggar during the Late Devonian. [ABSTRACT FROM AUTHOR]

A series of Mesozoic granites related to the subduction of the ancient Pacific plate are widely developed in the eastern part of the North China Craton. These granites contain garnet as a minor phase. Garnet records important information such as magma composition, temperature and pressure, and is an important object in the study of petrological evolution of granites. We take the late Jurassic garnet–bearing monzogranite in Xingcheng, Liaoning as the research object, and the magmatic evolution process in the study area is discussed by the in–situ element geochemical variation and the Raman effect of magmatic garnet girdle. It is found that the garnet has a zonation structure in which the contents of MnO and CaO increase and then decrease, while the contents of FeO and MgO decrease and then increase from the core to the edge. Through the simulation of the crystallization sequence of garnet and biotite, it is found that the garnet has "M" type "spessartine bell–shaped profile", Mn/(Ca + Mg + Fe) value and Mn/Fe value, which reflects that the crystallization pattern of minerals in the magma is dominated by biotite crystallization to garnet crystallization. It is considered that forward and reverse girdle can exist in the same garnet; the separation and crystallization of minerals in the late magmatic evolution is the main reason for the change in the compositional profile of the garnet. This is consistent with the late evolution of granitic magmas in the northeastern of the North China Craton after the late Jurassic. [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]

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]

Precise determination of the tectonothermal events at the Qinling–Qilian junction is significant for understanding the tectonic evolution of the eastern branch of the Paleo-Tethys. The Banpo pluton outcrops in the northern margin of the North Qinling were chosen as the research subject and their formation and tectonic environment were investigated using zircon U-Pb age and geochemical compositions. The weighted average values of 206Pb/238U ages of samples from three sites of the Banpo pluton corresponded to 213.4 ± 2.1 Ma (MSWD = 0.56), 213.0 ± 1.6 Ma (MSWD = 0.92), and 216.3 ± 2.3 Ma (MSWD = 2.0). All the samples are rich in light rare earth elements, exhibiting a seagull-type right-leaning partitioning curve, with obviously negative Eu anomalies. In addition, based on the regional geological data, it can be concluded that the Banpo pluton was formed during the transition period from a post-Orogenic environment to an anorogenic environment. The results indicated the final stage of the Triassic orogeny and the closure phase of the Paleo-Tethys. Also, it shows closure of the Paleo-Tethys-Mianxian-Lueyang Ocean by the Late Triassic period as well as the completion of the collision between the North China and Yangtze Blocks along the Qinling Orogenic Belt. [ABSTRACT FROM AUTHOR]

The progression from initial back-arc rifting to back-arc opening in ancient orogenic collages is important for reconstructing subduction histories, constraining tectonic switching, and understanding crustal growth and evolution. However, it is difficult to constrain this transition in ancient arcs. The Qinling-Dabie orogenic belt is one of the most important orogenic belts in eastern Asia, yet the history of Paleozoic accretionary processes in this belt remains equivocal, owing to a poor understanding of back-arc opening processes in the Erlangping unit. In this study, we present whole-rock geochemical analyses of mafic dikes in the Erlangping unit, along with U-Pb ages and Hf-O isotope compositions of zircon from these dikes. Zircon secondary ion mass spectrometry (SIMS) dating of these mafic dikes yielded U-Pb ages of 453 ± 3 Ma. The mafic dikes are calc-alkaline and are characterized by high K2O contents (1.16-3.16 wt%). They have enriched ([La/Yb]N = 4.3-14.9) light rare earth elements (REEs) and relatively flat heavy REE ([Dy/Yb]N = 0.9-1.5) patterns, and they exhibit enrichment in large ion lithophile elements (LILEs) but depletion in high field strength elements (HFSEs), resembling arc-like magmatism. These mafic dikes are characterized by relatively enriched initial 87Sr/87Sr (0.7049-0.7059), chondritic to slightly radiogenic εNd(t) (-0.36 to 1.33), and radiogenic whole-rock and zircon εHf(t) (+7.2-7.6 and +7.5-7.8, respectively). The zircons have δ18O values (5.0% ± 0.1%) similar to those of normal mantle zircon. Accordingly, we interpret that the mafic dikes were derived from an enriched lithospheric mantle source metasomatized by subducted Proto-Tethys (Shangdan) ocean material. In contrast, previously reported ca. 440 Ma gabbros from the Erlangping unit are tholeiitic and have lower incompatible trace-element concentrations with less enrichment in LILEs and less depletion in HFSEs than the mafic dikes presented here. Wholerock Nd and zircon Hf isotopic compositions suggest that these Silurian gabbros were derived from partial melting of a more depleted mantle with the involvement of asthenosphere, and they have a close geochemical affinity with back-arc basin basalts. In addition, trace-element ratios and geochemical modeling suggest higher melting pressures for the mafic dikes than the gabbros. The geochemical differences show systematic variations from islandarc basalt into back-arc basin basalt types, which is consistent with the magma source evolution of the Mariana Trough. Thus, we interpret that the ca. 454 Ma mafic dikes were emplaced when the infant arc split, and they record initial back-arc rifting in the Erlangping unit, whereas the Silurian gabbros subsequently formed during the opening of the back-arc basin. Our study provides a paradigm for deciphering the evolution of back-arc basins through the study of spatiotemporal geological and geochemical variations of mafic intrusions in ancient accretionary orogens. [ABSTRACT FROM AUTHOR]

The late Mesozoic tectonic evolution of the eastern North China craton was intimately related with the subduction of the paleo-Pacific plate. This study sheds light on Late Jurassic-Early Cretaceous basin-mountain coupling during paleo-Pacific subduction based on low-temperature thermochronology and geochemical analyses from the easternmost Yanshan fold belt, located at the northern edge of the craton. We performed apatite U-Pb and fission-track double dating and trace element analyses of basement and sedimentary rock samples, integrated with zircon and apatite (U-Th)/He analyses on bedrock samples. Our results revealed that the easternmost Yanshan fold belt experienced two stages of rapid cooling and exhumation in the Middle Jurassic-earliest Cretaceous (ca. 170-140 Ma) and in the Early Cretaceous (ca. 140-90 Ma). The Middle Jurassic-earliest Cretaceous exhumation (ca. 170-140 Ma) is mainly recorded by bedrock along the margins of intermontane basins of the eastern Yanshan fold belt. This exhumation event is consistent with compressional Yanshan movement during the Middle Jurassic-earliest Cretaceous coeval with paleo-Pacific flat-slab subduction. Subsequent Early Cretaceous rapid cooling is ascribed to the progressive evolution of the metamorphic core complexes and associated tectonic exhumation of major plutons of northeastern Asia, which were likely controlled by rollback of the paleo-Pacific slab. A middle Cretaceous (ca. 110-90 Ma) tectonic exhumation event is revealed by very low lag-time values in middle Cretaceous strata. Our findings illustrate the potential of a thermochronology approach that combines single-grain double dating and trace element analyses in synmagmatic orogenic systems, which may find application to other orogenic settings worldwide. [ABSTRACT FROM AUTHOR]

An early Paleozoic eclogite belt extends discontinuously for ~500 km in the East Kunlun Orogen, northwestern China, which provides insight into the evolution of the Proto-Tethys Ocean. However, the nature and age of the eclogite protoliths and subsequent metamorphism are unclear. Here, we report mineral chemical, zircon, and titanite geochronological; whole-rock major and trace elemental; and Sr-Nd isotopic data for eclogites from the Xiarihamu area in the western East Kunlun Orogen. At a minimum, these eclogites underwent peak eclogite-facies metamorphism at 27-28 kbar and 630-650 °C, post-peak decompression, and retrograde amphibolite-facies overprinting. Geochemically, eclogites have characteristics typical of enriched mid-oceanic-ridge basalts and oceanic-island basalts. Inherited magmatic zircon cores yielded a protolith age of 828 Ma, and metamorphic zircons yielded peak and post-peak decompression ages of 443 Ma and 422 Ma, respectively. A titanite U-Pb age of 413 Ma constrains the timing of later amphibolite-facies overprinting. The protoliths of the Xiarihamu eclogites were the products of continental rift-related basaltic magmatism, which was generated during the initial breakup of Rodinia. The protoliths experienced eclogite-facies metamorphism in a continental subduction/collisional setting during the early Paleozoic. The formation of the Xiarihamu eclogites suggests that the Proto-Tethys Ocean had closed by 443 Ma. Given the spatio-temporal relationship between the Xiarihamu magmatic Cu-Ni sulfide deposit and the eclogites studied, the former may have formed in a post-collisional extensional setting. The eclogites and magmatic Cu-Ni sulfide deposit from the Xiarihamu area jointly reveal the evolution of the East Kunlun Orogen from Neoproterozoic supercontinent breakup to early Paleozoic tectonic transitions from collisional convergence to post-collisional extension. [ABSTRACT FROM AUTHOR]

The late Mesozoic destruction of the eastern North China Craton (NCC) resulted from intense crust-mantle interaction, culminating in the formation of world-class gold deposits in the Jiaodong Peninsula at ca. 120 Ma. We present zircon U-Pb geochronological data, Hf isotopic compositions, whole-rock major and trace element, and Sr-Nd-Pb isotopic compositions for two suites of granitoids: one (the Linglong suite) that hosts significant mineralization and the other (the Weideshan suite) that is largely unmineralized. The Linglong suite was emplaced in the Late Jurassic at 160 ± 3 Ma to 155 ± 3 Ma, whereas the Weideshan suite was emplaced in the Early Cretaceous at 121 ± 2 Ma to 118 ± 1 Ma, coeval with gold mineralization. Geochemical data indicate the Linglong suite was derived from the melting of thickened lower crust of the NCC, mixed with material from the Yangtze Craton (YC) and intervening Su-Lu Orogenic Belt, whereas the Weideshan suite was formed from the partial melting of lower continental crust, with the addition of enriched lithospheric mantle components. The Late Jurassic magmatism was associated with crustal growth resulting from the continental collision between the NCC and YC and subsequent subduction of the Paleo-Pacific Oceanic Plate (PPOP). In contrast, Early Cretaceous magmatism was triggered by rapid lithospheric thinning and asthenospheric upwelling resulting from slab roll-back and stagnation of the PPOP beneath the NCC. Lithospheric delamination induced the widespread development of secondary structures associated with the major Tan-Lu Fault, providing favorable loci for the accumulation of auriferous fluids. [ABSTRACT FROM AUTHOR]

The eastern part of the Central Asian Orogenic Belt in NE China is one of the world's well-known Ag-Pb-Zn-Mo metallogenic provinces, and the late Mesozoic magmas have been considered to supply dominant metals for mineralization. However, Cu mineralization in this belt is relatively rare. The Zhalageamu deposit is a newly discovered copper deposit in this region and could be applied to address the issue of whether the regional late Mesozoic magmatism could have triggered the formation of large Cu deposits. The quartz diorite and granite porphyry in Zhalageamu returned laser ablation-inductively coupled plasma-mass spectrometric (LA-ICP-MS) zircon U-Pb ages of 267.1 ± 2.0 Ma and 255.6 ± 2.2 Ma, respectively. Molybdenite coexisting with chalcopyrite yielded an isotope dilution-negative-thermal ionization mass spectrometric Re-Os age of 141.8 ± 0.8 Ma. This age is almost identical to that of the coexisting arsenopyrite within the analytical uncertainty, which yielded an Re-Os isochron age of 140.7 ± 5.9 Ma. The above ages constrain the timing of Cu mineralization to the late Mesozoic. The fact that the Cu mineralization is >110 m.y. younger than its igneous host rocks precludes a genetic link between them. Instead, the Cu mineralization age indicates that a possible hidden late Mesozoic intrusion likely contributed Cu mineralization. The age of the Zhalageamu deposit is similar to that of the late Mesozoic magmatic-hydrothermal Ag-Pb-Zn-Fe-Sn mineralizing event (140-120 Ma) in NE China. This suggests that the Zhalageamu Cu mineralization was part of this event and implies the broader existence of a late Mesozoic magmatic-hydrothermal Cu mineralizing event in NE China, a discovery that would be of great significance for further Cu exploration. [ABSTRACT FROM AUTHOR]

The Curie Point Depth (CPD) marks a significant temperature boundary (∼580°C) within the Earth's lithosphere. However, there has been ongoing debate regarding its spatial distribution. In this research, we utilized the Equivalent Source Method (ESM) based on Gauss‐Legendre integration and data obtained from the EMM2017 model, along with a five‐layer susceptibility model, to generate a 0.5° × 0.5° grid of continental CPD distribution for China and surroundings. The average CPD in the study area is 30.4 km, which is slightly shallower than the average depth of global continental Moho (∼33 km). Notably, stable and cold cratonic basins, such as the Tarim Basin and the Sichuan Basin, exhibit deep CPD of ∼45 km. In contrast, the North China Craton, which has experienced significant tectono‐thermal activity since the Late Mesozoic, shows moderate CPD of ∼30 km and a gradual uplift from west to east. The Tuva‐Mongol orocline within the Central Asian Orogenic Belt, the Deccan Volcanic Province in the Indian subcontinent and the Eastern Yangtze Craton have shallow CPD of ∼20 km. We estimate the surface heat flow by CPD, and the result is consistent with measurements within a RMSE of 18.1 mW/m2. When comparing the CPD with Moho, we find that the CPD may lie below Moho in stable and cold cratonic areas. In comparison to two recent global CPD models, our regional model demonstrates better alignment with tectonic features. Plain Language Summary: The Curie Point Depth (CPD) is the depth where crustal temperatures equal the Curie temperature of magnetite (∼580°C), the dominant magnetic mineral in the crust, and hence below which there is no magnetization. It is a crucial temperature boundary within the Earth's lithosphere, providing valuable insights into the lithospheric thermal structure and dynamic evolution. Traditionally, the CPD is mostly inverted by the Power Spectral Density (PSD) method in the frequency domain, which is more suitable for shallow CPD regions. Here, we determine a new 0.5° × 0.5° continental CPD model for China and surroundings utilizing an Equivalent Source Method (ESM) in the spatial domain. Then we estimate the surface heat flow and crustal temperature with this CPD model, and discuss its relation with the Moho interface. Compared to two recent global models, our regional CPD model showcases enhanced consistency with tectonic characteristics. Key Points: We inverted a new regional continental Curie Point Depth model via Equivalent Source MethodBased on the new CPD model and measured thermal parameters, the surface heat flow and crustal temperature distribution are derivedOur new regional CPD model exhibits better consistency with the tectonics compared to two recent global models [ABSTRACT FROM AUTHOR]

The Sanjiang Tethyan Orogen plays a pivotal role in elucidating the geodynamic processes related to the evolution of the Paleo-Tethys Ocean. Research on the Gicha Complex within this orogen is imperative for comprehending the intricate evolution of the region. This study presents new findings from zircon U‒Pb dating, Hf isotope analysis, and whole-rock elemental analyses of gabbro, olivine gabbro, and the recently discovered mylonitic rhyolite and diabase in the Gicha Complex. The zircon U‒Pb dating yields ages of 703 ± 3 Ma for the diabase, 296 ± 2 Ma for the gabbro, and 231 ± 1 and 228 ± 2 Ma for the mylonitic rhyolite, demonstrating that these rocks record the extended evolution from the breakup of Rodinia to the closure of the Paleo-Tethys Ocean. The Neoproterozoic diabase samples exhibit shoshonitic and arc-like geochemical properties, with positive zircon εHf(t) values ranging from 1.1 to 3.7 and high Th/Yb values ranging from 1.34 to 3.07, suggesting that they were generated by partial melting of enriched subduction-modified lithospheric mantle in an active continental margin. The early Permian gabbro samples are part of the tholeiitic series and exhibit low SiO2 and K2O contents; depletions in Nb, Ta and Ti; and enrichment in Pb, indicating derivation from a combination of depleted mantle peridotite and subduction-related components. The whole-rock geochemical features suggest that these rocks formed in a back-arc setting featuring a small, mature ocean basin. The mylonitic rhyolite samples exhibit weakly peraluminous characteristics (A/CNK = 0.98–1.12) with high-K calc-alkaline geochemical features. The samples are depleted in Ba, Nb, Ta, and Ti and enriched in Th, U, Pb, and LREEs and exhibit negative to positive zircon εHf(t) values ranging from − 0.5 to + 5.9, indicating that they originated from partial melting of Meso-Neoproterozoic juvenile lower crust. Geochronological, petrological, and geochemical analyses indicate that the subduction of oceanic crust occurred along the western margin of the Yangtze Block until the late Neoproterozoic (~ 703 Ma). [ABSTRACT FROM AUTHOR]

Global volcanic and plutonic olivines record the compositional characteristics and physicochemical conditions of the parental magmas. Thus, they have significant potential for use as petrogenetic discriminators of the olivine formation environment and prospecting indicators for potential host rocks of magmatic sulfide deposits. Several data visualization approaches have been proposed by researchers to determine olivine origins. However, they can only discriminate specific olivine populations and require the incorporation of trace elements for which data are lacking globally. In this study, a machine-learning method consisting of the random forest algorithm and the synthetic minority oversampling technique (SMOTE) is used to discriminate the crystallization environments of olivine and predict the sulfide potential of olivine-bearing mafic-ultramafic intrusions. We employ a global data set of 24 341 olivine samples from 12 environments to determine the contents of MgO, FeO, Ni, Ca, Mn, and Cr and the Fo number [100 × Mg/(Mg+Fe)]. The results indicate that the proposed method can classify olivine into genetically distinct populations and distinguish olivine derived from mineralized intrusions from that derived from sulfide-barren intrusions with high accuracies (higher than 99% on average). We develop a dimensionality reduction algorithm to visualize the olivine classifications using low-dimensional vectors and an olivine classifier (accessible at http://101.33.204.62:8080/olivine%5fweb/main.html China University of Geosciences, Beijing). The model is used successfully to identify the contributions of distinct sources to regional magmatism using olivines from the late Permian picrite and basalt along the western margin of the Yangtze block (SW China) and to predict the sulfide potential of the newly discovered Qixin mafic-ultramafic complex in the southern Central Asian Orogenic Belt (NW China). The findings suggest that the proposed approach enables the accurate identification of olivine origins in diferent formation environments and is a reliable indicator suitable for global Ni-Cu-platinum group element (PGE) exploration. [ABSTRACT FROM AUTHOR]

Although carbonatite-alkaline complexes are the primary source of the world's niobium (Nb) supply, the mineralization style is largely variable in these complexes and the processes behind their formation are still poorly understood. Exemplifying with our new observations on the ~430 Ma Miaoya and Shaxiongdong carbonatite-syenite complexes in the southern Qinling orogenic belt, central China, show that disseminated Nb mineralization in these two deposits is pervasive throughout the entire complexes in both syenite and carbonatite. Both magmatic and hydrothermal processes have contributed to Nb mineralization in both deposits, despite differences in the mineralization style. The Nb-bearing minerals in the mineralized Miaoya syenites include magmatic U-poor pyrochlore, rutile, and ilmenite with minor amounts of columbite, and hydrothermal columbite and rutile, whereas those in the mineralized carbonatites are mainly magmatic U-poor pyrochlore, uranpyrochlore, U-rich betafite, and rutile with minor amounts of columbite, and hydrothermal columbite and rutile. On the other hand, the Nb-bearing minerals in the mineralized Shaxiongdong syenites include magmatic U-poor pyrochlore, titanite, rutile, and ilmenite, and hydrothermal fersmite, rutile, and ilmenite, whereas those in the mineralized carbonatites are mainly magmatic U-poor pyrochlore without any hydrothermal Nb-bearing minerals. Field observations, whole-rock chemical and Sr-Nd isotopic compositions strongly constrained that assimilation of U-rich rocks (e.g., the hosting Yaolinghe and Meiziya Groups) and magma differentiation are responsible for diverse magmatic Nb mineralization in the two deposits. On the other hand, the diverse assemblages of hydrothermal Nb minerals in Miaoya and Shaxiongdong are mainly controlled by variations in the nature of the fluids, which is constrained to be genetically related to ~220 and ~420 Ma hydrothermal events, respectively. In summary, both magma evolution (e.g., differentiation, assimilation) and late hydrothermal overprinting are responsible for the diverse Nb mineralogy in carbonatite-alkaline complexes, a situation that is commonly observed worldwide. [ABSTRACT FROM AUTHOR]

The Ailaoshan orogen in SW China records the evolution of the Ailaoshan Paleo-Tethyan ocean and the amalgamation history between the South China and Indochina blocks, an important process for the formation of Southeast Asia. However, its tectonic evolution remains ambiguous with various competing models. We have carried out an integrated geochronological–petrological–geochemical study for the granites, dacites-rhyolites, granodiorites and trachyandesites in this orogen to give new constraints on this issue. The 255–254 Ma granites and the 250–248 Ma dacites-rhyolites show similar geochemical features and are characterized by strongly peraluminous nature, continental crust-like trace element patterns and negative zircon εHf(t) values (−14.4 to −6.6), indicating they derived from partial melting of ancient crust. The 229 Ma hornblende-bearing granodiorites are metaluminous to weakly peraluminous (A/CNK = 0.96–1.01) and belong to high-K calc-alkaline I-type granites. They show depleted whole-rock Sr-Nd and zircon Hf isotope compositions (initial 87Sr/86Sr = 0.7027 to 0.7038, εNd(t) = 4.0 to 4.1, εHf(t) = 9.3 to 11.5), suggestive of derivation from partial melting of juvenile mafic crust. The 226 Ma trachyandesites are characterized by high MgO (4.1–4.6 wt.%), high Mg# (56) and arc-type geochemical affinities with enriched isotope compositions (initial 87Sr/86Sr = 0.7108 to 0.7111, εNd(t) = −7.7 to −7.5, εHf(t) = −6.3 to −3.5). These features indicate that their parental magmas derived from partial melting of enriched lithospheric mantle metasomatized by oceanic sediment-derived melts. These new data, in conjunction with spatial-temporal-temperature variations of igneous rocks, metamorphic records and stratigraphic changes in the region, suggest that the Ailaoshan Paleo-Tethyan ocean closed at the Early Triassic (ca. 250 Ma) which was followed by the Late Triassic postcollisional slab breakoff, and the ocean experienced westward unipolar subduction during its evolution with no assumed eastward subduction. [ABSTRACT FROM AUTHOR]

The article summarizes paleomagnetic data for Tuva, Mongolia, and Eastern China, which showed that in the central part of the Central Asian Fold Belt, areas with different paleomagnetic characteristics are distinguished. These are areas located north of the Mongol–Okhotsk mobile belt, the western and eastern parts of Southern Mongolia, and Eastern China. The areas located north of the Mongol–Okhotsk mobile belt were part of the structure of the Siberian continent from the Ordovician and experienced movement similar to the Siberian continent. The regions of the western part of Southern Mongolia have been part of the structure of the Siberian continent since the Late Carboniferous. The geological complexes of the eastern part of Southern Mongolia and blocks of Eastern China in the Middle Paleozoic and Early Mesozoic were located in a latitudinal interval close to the North China block and experienced similar latitudinal movements and rotations. The large difference between the paleolatitudes of coeval strata in western and eastern Mongolia and Eastern China south of the Mongol–Okhotsk mobile belt suggests the existence of a tectonic boundary that separated blocks formed at paleolatitudes along the 107° E meridian, close to Siberia and North China. To the west of the 107° E meridian, the paleolatitudes of the formation of Late Carboniferous–Permian strata are close to the paleolatitudes of Siberia, and east of the meridian, to the paleolatitudes of North China. The width of the Mongol–Okhotsk Ocean in the Late Paleozoic–Early Mesozoic was 30°–40° E (~3000–4000 km). The southern limit of the Mongol–Okhotsk Ocean was segmented and consisted of terranes of various genesis and structure. The closure of segments of the Mongol–Okhotsk Ocean occurred as a result of collision of terranes with the Siberian continent from the Late Carboniferous (in the west) to the Jurassic (in the east). [ABSTRACT FROM AUTHOR]

The Daqing Shan (DQS) located in the Yinshan-Yanshan Orogenic Belt plays an important role in the Mesozoic to Cenozoic evolution of the North China Craton. However, the cooling and exhumation history since the Cretaceous is still controversial. Integrating the apatite fission track (AFT) data in both this study and previous works, a three-stage exhumation history from Cretaceous to Neogene of the DQS is proposed. (1) The first stage is composed of the early exhumation during Early Cretaceous driven by the collision between the North China and Siberia cratons (ca. 148–132 Ma) and the far-field effect of the subduction of the Pacific Plate (ca. 132–114 Ma). (2) Due to the subsidence of the Hetao Basin and the subsequent compensation between the DQS and the Hetao Basin, the DQS experienced the second rapid exhumation from Early Eocene to Early Oligocene (ca. 54–29 Ma). (3) Since the Late Miocene (ca. 13.5 Ma), the third rapid cooling and exhumation of the DQS occurred due to the far-field effect of the uplift of the Tibetan Plateau and the subduction of the Pacific Plate. [ABSTRACT FROM AUTHOR]

Granulite facies rocks provide important keys to evaluating collisional metamorphism in orogenic belts. The mafic granulites of Baoding in the Fuping Complex of the North China Craton occur within the Trans-North China Orogen (TNCO), a major Paleoproterozoic collisional orogen. Here, we present results from detailed investigations on newly discovered garnet pyroxenite, garnet two-pyroxene granulite, and garnet-bearing-plagioclase amphibolite using petrographic, mineralogical, geochemical, and zircon U-Pb dating methods. Our results show that the Fuping Complex metamorphic evolution in this study evolved in four stages: prograde (M1), high-pressure granulite facies (M2), granulite facies (M3), and retrograde (M4) stages. The mineral assemblage of the prograde stage (M1) consists of Amp + Pl + Q within garnet cores. The mineral assemblage of high-pressure granulite facies at the peak stage (M2) consists of Gt + Cpx + Pl + Q ± Amp, forming the garnet pyroxenite. The granulite facies stage M3 is characterized by the occurrence of orthopyroxene, with a mineral assemblage of Gt + Cpx + Opx + Amp+ Pl + Q. The early retrograde stage M4-1 includes clinopyroxenes scattered inside amphiboles, following the breakdown of garnet and clinopyroxene. The mineral assemblage of this stage comprises Amp + Pl + Q + Ilm ± Cpx. Later, in the late retrograde stage M4-2, the composition of amphiboles changed to actinolite, and epidote and chlorite started to appear in the matrix. Traditional geothermobarometry yielded P-T conditions of 700~706 °C and 6.0~6.2 kbar for prograde stage M1, 854~920 °C and 13.0~13.8 kbar for high-pressure granulite facies stage M2, 912~939 °C and 8.1~9.9 kbar for M3, 661~784 °C and 3.1~4.4 kbar for M4-1, and 637~638 °C, 1.1~1.3 kbar for M4-2, along a clockwise P-T path with a nearly isothermal decompression (ITD) and slight heating. Zircon LA-ICP-MS U-Pb dating constrains the timing of the high-pressure granulite facies metamorphic event to be between 1.83 and 1.86 Ga. Geochemical features suggest that the protoliths of the high-pressure granulites may have formed in an island arc environment within a convergent margin setting. Together with results from previous studies, our data suggest that the ~1.85 Ga metamorphic age recorded in the Fuping Complex represents a regional metamorphism in the TNCO, associated with the subduction–collision and assembly of the Eastern and Western Blocks of the NCC. [ABSTRACT FROM AUTHOR]

This document explores the geological features of the Central Asian Orogenic Belt (CAOB), specifically focusing on the Beishan orogenic assemblage in northwest China. The discovery of a Silurian gabbro in the Hongbaoshan area is discussed, which extends the Silurian SSZ-type ophiolite belt and has potential for VHMS deposits. The gabbro is primarily composed of plagioclase and pyroxene, with minor hornblende and quartz. Dating methods indicate an age of 423.6 ± 1.7 Ma, consistent with the Hongliuhe ophiolite. The gabbro samples also show enrichment in iron, gold, zinc, and copper, suggesting the presence of VHMS mineralization in a supra-subduction tectonic environment. [Extracted from the article]

The eastern Qaidam Basin (EQB), along with its surrounding orogenic belts, witnessed complicated tectonic movements in the period from the late Paleozoic to the early Mesozoic. As strategic succeeding strata, the Carboniferous strata (CST) in the EQB have gradually become a research hotspot in recent years. However, the question of how tectonism controlled the tempo-spatial evolution of the CST has yet to be studied. To resolve these issues, we collated statistics related to unconformities, seismic interpretation, and basin modeling in this study. The results show that the structure of the CST was mostly controlled by NNE-striking faults, namely the Zongjia and Ainan Fault, in the period from the Carboniferous to the Triassic time. During the Carboniferous time, the sedimentation of the CST was controlled by medium-high angle potential normal faults. The CST experienced two stages of tectonic subsidence and subsequent burial: the highest average subsidence and burial rate of 45 m/Ma and 12 m/Ma occurred at 340~285 Ma, decreasing to 15 m/Ma and 7.5 m/Ma between 305 Ma and 250 Ma. However, the maximum burial (~5500 m) took place at ~250 Ma. From the end of the late Permian to the late Triassic (254~195 Ma), the overall exhumation rate of the CST has averaged 38.71 m/Ma, and 75 m/Ma in the southern margin of the Huobuxun Depression. The CST near the piedmont margins of the EQB suffered essential denudation at 254~195 Ma, resulting in small amounts of the residual CST. In these areas, the CST were deformed with a steepening dip during this time and were characterized by the combinations of syncline-anticlinal asymmetric folds with the high-angle interlimb. These findings indicated that the tempo-spatial evolution of the CST was possibly influenced by the sedimentary and tectonic transition, and was a combined response to Paleo-Tethys Ocean subduction, and arc-continental collisions since the late Paleozoic to early Mesozoic periods. [ABSTRACT FROM AUTHOR]

The North China Craton (NCC), notably the southeastern margin of the NCC, hosts the most typical example of decratonic gold deposits. However, the factors controlling the intensity of decratonic gold mineralization and the relation between the geodynamic model of decratonization and gold mineralization still deserve to be well elucidated. The Bengbu and the Jiaobei uplifts are located at the southeastern margin of the NCC and the two uplifts have similar tectonic positions and metamorphic basements, yet the intensity of gold mineralization is quite distinct. Mesozoic mineralization and magmatism in both uplifts are controlled by the same deep geodynamic process. Accordingly, in this review, we make an effort to find solutions to these problems by integrating the whole-rock geochemical and Sr-Nd-Pb isotopic data as well as zircon U-Pb-Hf-O isotopic data from late Mesozoic magmatic rocks from the Bengbu uplift and the Jiaobei uplift. The late Mesozoic magmatism of the two uplifts can be divided into three stages, i.e. Late Jurassic (stage I), middle Early Cretaceous (stage II), and late Early Cretaceous (stage III). Comparative studies of the gold-related rocks in these two areas indicate that the intensity of the decratonic gold mineralization is controlled by magmatic source composition (i.e. the affinity of the upper crust of the South China Block), intrinsic magmatic variables of gold-related rocks (i.e. redox state and volatiles content), as well as lithospheric architecture (i.e. lithospheric thickness). Additionally, the integrated data of magmatic rocks in the three stages suggest that plate subduction acts as the recycling engine factory responsible for the decratonic mineral systems. In the early stage (Triassic), continental subduction of the South China Block induced pre-enrichment of ore-forming nutriments in magma sources, whereas in the late stage (Early Cretaceous), oceanic subduction of the paleo-Pacific plate led to the craton destruction, thereby triggering related magmatism and gold mineralization in the eastern NCC. [ABSTRACT FROM AUTHOR]

The origin of granitic rocks from the South Qilian orogenic belt is of great significance for understanding the continental tectonic framework of Western China. Currently, scholars have different opinions on the tectonic evolution of the South Qilian. Huashigou granite, which exhibits multiple intrusive episodes, is a suitable example for studying the tectonic evolution of the South Qilian. New zircon U–Pb ages and the whole-rock elemental and Sr–Nd–Hf–O isotopic compositions of Huashigou granitic rocks are presented here to investigate their petrogenesis and discuss the tectonic implications for the evolution of the South Qilian orogenic belt. LA-ICP-MS zircon U–Pb dating yielded crystallization ages of 368.7 ± 3.5 Ma, 261.5 ± 0.63 Ma, and 262.2 ± 1.4 Ma for granodiorites from the Hua1 pluton, quartz diorites from the Hua2 pluton, and porphyritic tonalites from the Hua4 pluton, respectively. Late Devonian granodiorites from the Hua1 pluton belonged to the metaluminous calc-alkaline series and were characterized by an enrichment in LREEs, a depletion in HREEs, negative Eu anomalies, and Sr/Y ratios of 9.17 to 11.67. They showed (87Sr/86Sr)i ratios of 0.712356 to 0.71195, εNd(t) values of −6.56 to −6.14, and an εHf(t) value of −2.06. Middle Permian granitic rocks mainly consisted of quartz diorites and porphyritic tonalites, which are part of the metaluminous tholeiitic series and weakly peraluminous tholeiitic series, respectively. Quartz diorites from the Hua2 pluton were characterized by an enrichment in LREEs, depletions in HREEs and HESEs, weak negative Eu anomalies, and Sr/Y ratios of 13.25 to 14.79. They showed (87Sr/86Sr)i ratios of 0.705905 to 0.705971, εNd(t) values of +0.78 to +0.82, and a δ18OV-SMOW value of 12.4‰. Porphyritic tonalites of the Hua4 pluton were characterized by an enrichment in LREEs, depletions in HREEs and HESEs, weak negative Eu anomalies, and Sr/Y ratios of 9.22 to 12.74. They showed (87Sr/86Sr)i ratios of 0.719528, εNd(t) values of −8.57, and a δ18OV-SMOW value of 11.8‰. We can conclude that Late Devonian granodiorites were derived from the partial melting of enriched and shallow-depth crustal materials, whereas Middle Permian granitic rocks were formed by the delamination of a thickened lower crust after the closure of the Paleo-Tethys Ocean, which caused the underplating of mantle-derived basaltic magma, inducing the partial melting of the lower crust at different depths. Our results show that there were at least two important stages of compressional and extensional tectonic switches in the South Qilian orogenic belt during the Late Paleozoic Era, and the evolution of Altyn Tagh–Qilian–North Qaidam had evident stages. [ABSTRACT FROM AUTHOR]

Clarifying the role of mountain-building processes in the filling history of large hinterland basins is an essential aspect of basin-mountain system research. We consider the case of the Triassic South Ordos Basin (SOB) to clarify these points. Located in the south-western North China Block (NCB), the SOB which preserves the most complete Triassic deposition on the north of the Qinling Orogenic Belt (QB) is crucial for understanding the detailed tectonic processes of the QB. Sedimentological, petrological and zircon U-Pb geochronological signatures from the three parts (eastern, central and western) in the SOB indicate that the sediment source migrated both temporally and spatially. Stratigraphic correlation identified two fluvial progradational episodes from south to north in the fluvial-deltaic-lacustrine sedimentary system, one in the eastern SOB and the other in the central SOB. The Late Triassic detrital zircons in the central SOB with distinguishing Neoproterozoic ages were derived from the southern margin of the NCB and the QB. The western SOB exhibited the sediment source shifted from pre-Triassic North Qilian Belt sedimentary cover to basement from the Middleto-Late Triassic based on a zircon age transition from ca. 2000 to ca. 430 Ma. Late Triassic sediment sources also included the southern margin of the NCB and the QB. Differing provenances from east to west were also confirmed using thin section and heavy mineral analyses. Regional comparisons of zircon age distributions in the eastern SOB with published data indicate that detritus from the QB was first transported to the eastern SOB and then to the central and western SOB. Spatiotemporal changes in the sediment source and sedimentary filling transitions in the three parts of the SOB suggest that the QB underwent asynchronous uplift that began in the east during the Early Triassic and propagated westward, reaching its maximum extent in the early Late Triassic. [ABSTRACT FROM AUTHOR]

The Junggar Basin is located on the southwestern margin of the Central Asian Orogenic Belt (CAOB). Whether the Late Permian-Early Triassic tectonic inversion there recorded the final closure of the North Tianshan Ocean or postaccretionary intracontinental deformation remains controversial. Linking the structural style and provenance analysis of the western and northern margins of the Junggar Basin can provide a better understanding of this tectonic event and its geodynamic mechanisms. Seismic reflection profiles show that Early Permian syn-rift half-grabens were followed by the Middle Permian thermal sag, which is characterized by regional onlap and the migration of the depocentre to the centre of the basin. Together with the published isopach and palaeogeography maps in the western margin of the Junggar Basin, the seismic profiles demonstrate that the reactivation of the Ke-Bai and Wu-Xia dextral transpressive fault zones between the West Junggar terrane and the Mahu sag controlled the tilting and deformation of pre-Permian strata and the distribution of Late Permian-Early Triassic fan deltas. The reported igneous and sedimentological evidence indicates that the southern margin of the Junggar Basin was a rift basin controlled by transtensional strike-slip faults in the Early Permian, and also was followed by a Middle Permian thermal sag. Quantitative provenance analysis using detrital zircon geochronology and the DZmix program shows that the West Junggar terrane and Tianshan orogenic belts experienced varied uplift, indicative of a transition from the Middle Permian thermal sag peneplanation to the Late Permian-Early Triassic tectonic inversion involving reactivation of Early Permian normal faults. This intracontinental deformation event in the Junggar Basin was taken up by block counterclockwise rotation during the final amalgamation of the Pangea, which may be the long-range effect of the final closure of Paleo-Asia Ocean in the eastern part of the CAOB. [ABSTRACT FROM AUTHOR]

Arc magmatism can provide crucial information about crustal recycling and growth in subduction zones. However, the crustal material transfer process and mechanism from subducting slab to overlying mantle wedge are controversial. Here, we present detailed petrological, geochronological, geochemical, and Sr-Nd-Hf isotopic data, and previously published data for two episodes of subduction-related magmatism in the Northern Yili Block, NW China, to study these issues in relation to the recycling of continental crust and the growth of two separate magmatic episodes at 400-350 Ma and 350-300 Ma, respectively. The Nd-Sr isotope modeling results, low Nd/Sr, and variable Hf/Nd ratios demonstrate that the arc magmatism of these two episodes could be derived from two distinct mélange sources that formed at the slab-mantle interface during subduction of the Junggar oceanic plate. In the first episode, magmatic rocks exhibit high Th/Yb and (La/Sm)N ratios and the decoupling of Nd-Hf isotopes, which leads to an interpretation that the primary magmas were derived from sources mainly mixed by sediments and mantle-wedge peridotites. In contrast, the magmas of the second episode exhibit high Ba/La and Ba/Th ratios and the coupling of Nd-Hf isotopes, which implies that these magmas were likely produced from mélange diapirs dominated by the mixing of midoceanic-ridge basalts and mantle peridotites. The episodes of Nd-Hf isotopic decoupling and coupling coincided with crustal material recycling and crustal growth in subduction zones, respectively. Considering that the Northern Yili Block at 400-350 Ma was characterized mainly by enriched Nd-Hf isotopes of magmatic rocks and no development of the forearc accretionary complex, while the Northern Yili Block at 350-300 Ma featured high εHf(t)-εNd(t) values of magmatic rocks, occurrences of extension-related magmatism, and distribution of the forearc accretionary complex and immature back-arc basin, we propose that these two different mélange sources probably developed in response to subduction transition. That is, one resulted from advancing and the other was relevant to retreating regime. The partial melting of these mélanges in the mantle wedge generated intermediate felsic magmas, which might have acted as a leading mechanism for crustal recycling and growth of the accretionary orogenic belt. [ABSTRACT FROM AUTHOR]

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

In this study, detrital zircon U–Pb geochronology, trace element and Hf isotopic compositional data from the Early-Middle Triassic clastic rocks in the eastern Sichuan Basin were obtained to distinguish the sediment provenance and constrain the timing of the initial collision between the South China and North China blocks. Detrital zircons from the Early Triassic Feixianguan Formation clastic rocks yield one major age peak at 2476 Ma and three minor age peaks at 1886, 802 and 304 Ma. These detrital zircons may be derived from the South China Block. Detrital zircons from the Early Triassic Jialingjiang Formation clastic rocks yield multiple age peaks at 979, 856, 392 and 269 Ma, indicating a mixed sediment provenance from the South China Block and Qinling Orogenic Belt. This is the first appearance of the detritus with the Qinling Orogenic Belt affinity in the eastern Sichuan Basin. Detrital zircons from the Middle Triassic Leikoupo Formation clastic rocks yield two centralized age peaks at 447 and ca. 245 Ma. These zircons may mainly be derived from the Qinling Orogenic Belt. The results indicate an abrupt change in the detrital zircon U–Pb provenance from the South China Block to the Qinling Orogenic Belt during the Early-Middle Triassic. Integrating the provenance change and other geological characteristics, we suggest that the initial collision in the eastern Qinling Orogenic Belt occurred in the Early Triassic. [ABSTRACT FROM AUTHOR]

Tectono‐thermal records older than ca. 1.8 Ga in the North China craton have been poorly resolved given that they have been strongly overprinted by younger events, despite being key to understanding the tectonic evolution of the craton. We report results of monazite Th–U–Pb isochron geochronology via electron probe microanalysis on the Zanhuang massif in the North China craton, to determine its detailed Precambrian tectono‐thermal history. Results suggest that the ca. 2.1 Ga tectono‐thermal event can be divided into distinct ca. 2.17 Ga and ca. 2.10 Ga stages, reflecting metamorphism related to retroarc regional extension of the North China craton. Similarly, the previously established ca. 1.8 Ga metamorphic event can be divided into distinct ca. 1.88 Ga and ca. 1.79 Ma stages. Through a detailed summary and comparison, we interpret that the ca. 1.88 Ga monazite age reflects the timing of peak metamorphism, which was followed by ca. 1.79 Ga retrogression. [ABSTRACT FROM AUTHOR]

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

Ambient noise tomography, when applied to a dense linear seismic array, has the capability to provide detailed insights into the fine velocity structures across diverse tectonic settings. The linear station arrangement naturally generates parallel and concentrated ray paths along the array trend. This unique geometry requires specific optimization of the inversion methodology and model parameterization. The Bayesian-based transdimensional inversion method, characterized by its fully non-linear nature and high degree of freedom in parameter settings, offers a powerful tool for ambient noise inversion. To effectively adapt this method to a linear array layout, we propose a modification to the Voronoi cell tessellation built in the transdimensional method. By introducing spatial priority to the Voronoi kernels, we strategically increased the density of Voronoi cells along the direction of the array. We then applied the modified approach to a linear seismic array in the North China Craton and validated its robustness through phase velocity images and resolution tests. Our improved non-uniform sampling technique in the 2-D model space accelerates convergence while simultaneously enhancing model accuracy. Compared with the conventional damped leastsquares method, the proposed algorithm revealed a shear-wave velocity map with notable low-velocity anomalies situated in the middle and lower crust beneath the borders of the Ordos block and its surrounding orogenic belt. Aligned with the crustal structures revealed by receiver function and electrical imaging, our findings indicated that the western and eastern margins of the Ordos block had experienced intensive crustal wedge deformation and re-melting, respectively. [ABSTRACT FROM AUTHOR]

The Devonian granitoids are widespread in the Beishan area of the southern Central Asian Orogenic Belt, which provides key geological records for revealing the middle Palaeozoic evolution of the Paleo-Asian Ocean. This study presents new zircon U–Pb ages, whole-rock major and trace elements, and Sr-Nd-Hf isotopes of four granitic plutons in central Beishan. The Haergen muscovite monzogranites were emplaced in the Early Devonian (401 Ma) and are considered as S-type based on their peraluminous features and high P2O5 contents. They show high 87Sr/86Sr(i) (0.7097 to 0.7141), low ℇNd(t) (−4.7 to −4.3) and variable ℇHf(t) (0 to 6.9), indicating an ancient crust source. The Balegentai, Haerteerdele, and Miaomiaojing plutons were intruded in the Late Devonian with ages of 381 Ma, 379 Ma, and 361 Ma, respectively. They are I-type granites, as indicated by their metaluminous to weakly peraluminous features and low zircon saturation temperatures. Furthermore, they present depleted 87Sr/86Sr(i) (0.7042 to 0.7079), ℇNd(t) (−1.6 to 2.2) and ℇHf(t) (4.0 to 10.6), suggesting that they were derived from the partial melting of juvenile crustal rocks. The Early Devonian granitoids with an age peak of 410 Ma in central Beishan consist of I-S-A type granites with variable Nd-Hf isotopes, implying extensive interactions between juvenile and/or mantle-derived and ancient crust-derived magma. In contrast, the Middle-Late Devonian granitoids with an age peak of 370 Ma consist of I-A type granites with depleted Nd-Hf isotopes, implying the input of more juvenile materials. We conclude that a collisional event between the Mazongshan and Huaniushan units occurred during the Early Devonian. The Middle-Late Devonian magmatism was formed in an extensional setting, and the Huaniushan unit was also influenced by the northwards subduction of the Liuyuan Ocean. [ABSTRACT FROM AUTHOR]

As one of the most representative Paleoproterozoic orogenic belts in the North China Craton, the Jiao-Liao-Ji Belt is of great significance to explore the Paleoproterozoic tectonic evolution of the North China Craton, as well as the convergence process of the Columbia Supercontinent. In this study, we present new geochronological and geochemical data of Paleoproterozoic meta-mafic rocks in the Southern Jilin Province, NE China. Our primary objective is to further constraint the formation and evolution of the Jiao-Liao-Ji Belt. The zircon U–Pb dating reveals that the meta-mafic rocks crystallized at 2.2–2.0 Ga, followed by a metamorphism occurring at ~ 1.9 Ga. Additionally, most of the mafic rocks display moderate fractionation in both light rare earth elements (LREEs) and heavy rare earth elements (HREEs), suggesting their association with an arc setting. Furthermore, the rocks also display an enrichment in large ion lithophile elements (LILEs) such as Cs, Rb, Ba, and Pb, and depletion in high field strength elements (HSFEs) including Nb, Ta, Zr, and Ti. These geochemical characteristics suggest a back-arc setting, indicating that the meta-mafic rocks originated from asthenospheric mantle that was metasomatized by fluids or melts derived from the subducting slab. Notably, a shoshonitic metabasalt exhibits trace element and REEs patterns that resemble those of ocean–island basalts. This suggests that the shoshonitic metabasalt was formed in an oceanic island environment, likely generated from the asthenospheric mantle. Combining these findings with previous studies, we can conclude that the Jiao-Liao-Ji Belt is associated with arc–continental collision, indicating the presence of a modern-type plate tectonic regime in the northeastern North China Craton during the Paleoproterozoic period. [ABSTRACT FROM AUTHOR]