Determining the temperature of crustal anatexis associated with granitic magmatism is vital for understanding the petrogenesis of granites and the processes underlying crustal anatexis. During the partial melting of meta-sedimentary rocks, the breakdown of biotite at elevated temperatures can lead to the formation of peritectic garnet, which is typically rare or absent at lower temperatures when melting is predominantly driven by muscovite breakdown. This distinction makes magnesium (Mg) isotopes a valuable tool for tracing relative variations in crustal melting temperatures, as garnet exhibits the lowest delta 26Mg values compared to other Mg-bearing phases under equilibrium fractionation. However, the extent to which temperature variations influence melt Mg isotope compositions remains inadequately understood. In this study, we present Mg and oxygen isotope data for high-and low-temperature leucogranites from the Himalayan orogen, alongside whole-rock major and trace element data, and zircon Ti content from previous studies. Low-temperature leucogranites, with maximum Ti-in-zircon temperatures ranging from 739 to 801 degrees C, display negative delta 26Mg values between-0.70 and-0.14 %o, aligning with most global S-type granites. Conversely, high-temperature leucogranites, exhibiting maximum Ti-in-zircon temperatures of 800 to 855 degrees C, possess positive delta 26Mg values ranging from 0.46 to 0.53 %o, significantly exceeding those of Himalayan metasedimentary rocks and most global S-type granites. The high-temperature leucogranites also demonstrate relatively elevated Nb/Ta and Eu/Eu* ratios, while their whole-rock delta 18O and CIA values are comparable to those of low-temperature leucogranites. These findings suggest that fluid alteration, fractional crystallization, and crustal assimilation have a minimal impact on the Mg isotope discrepancies between the two granite groups. We propose that the positive delta 26Mg values of the high-temperature leucogranites result from a greater fraction of peritectic garnet in the melting residue, attributable to higher anatectic temperatures. Phase equilibrium modeling indicates that the peritectic reaction involving muscovite breakdown is swiftly replaced by biotite breakdown as temperatures rise, leading to a steady increase in the corresponding fraction of garnet. Equilibrium fractionation calculations further corroborate that melt delta 26Mg values rise with an increasing fraction of peritectic garnet, with values at high temperatures significantly surpassing those at lower temperatures. Consequently, this study elucidates a causal relationship between Mg isotope composition and anatectic temperature, highlighting that whole-rock Mg isotopes can serve as a reliable indicator for distinguishing between high-and low-temperature S-type granites.

The Gaozhou region is the core of the Yunkai Terrane, located in southwestern Cathaysia Block of South China. This study carried out 1 : 50000 field geological mapping, integrated with geochemical analysis of garnet-bearing and garnet-free plagiogneisses, and detailed petrography, mineral chemistry and phase equilibrium modeling of garnet-biotite plagiogneissses. Analytical results indicate that both garnet-bearing and garnet-free biotite plagiogneisses is characterized by high contents of SiO, and Al2O3, low Tio, content, low ratios of Na2O/K2O and Fe2O3T/K2O, negative europium anomaly, and high (La/Yb), ratios, Additionally, they are enriched in rubidium Rb, Th, U, while being depleted in HFSEs such as Nb, Ta, Zr, Hf. The protolith is likely a suite of clay-bearing greywacke formations on the surface, intercalated with a small amount of arkose, and belongs to paragneiss. Petrological examination reveals that garnet-biotite plagiogneiss experienced two metamorphic stages, with peak assemblage of Crt+Pl+Bt+Kfs+Ms+L+Qz and retrograde assemblage of Pl+Bt+Kfs+Ms+Qz. Mineral composition and phase equilibrium modelling constrain the peak P-T conditions of 740 similar to 750 degrees C and 1.15 similar to 1.20GPa, followed by retrograde conditions below 650 degrees C. This constructs a clockwise P-T path involving cooling and decompression, indicating that these rocks underwent early crustal thickening and subsequent rapid exhumation/uplift processes. Previous geochronological data indicate that the metamorphic event of the Cathaysia Block occurred during 460 similar to 400 Ma. Thus, the metamorphic basement of the Gaozhou region experienced high-pressure amphibolite facies metamorphism during the Early Paleozoic, suggesting that the Yunkai Tarrene should be involving in the Caledonian crustal thickening event.

Deciphering the magmatic evolution of S-type granites through zircon petrochronology presents significant challenges due to the textural complexities observed in this mineral, particularly so for the Himalayan leucogranites in which zircon is characterized by large relict cores but narrow overgrowth rims. Conventional whole-rock geochemical approaches often fail to adequately resolve dynamically varied magmatic sources and processes. In this study, we utilize integrated in-situ monazite U-Th-Pb geochronology, and trace element and Nd isotope geochemistry of the Cuonadong granitic suite, which includes two-mica granite, muscovite granite, and pegmatite, located in the eastern Tethyan Himalaya, to constrain the timing, duration and evolution process during magma crystallization. Our monazite data collectively reveal a crystallization history lasting ca. 5.2 Myr and three distinct magmatic pulses occurring at ca. 20, 18, and 16 Ma, respectively, characterized by progressively decreasing epsilon(Nd)(t) values (from -8.7 to -15.4) and varying rare earth element (REE) compositions, collectively documenting evolving melt sources and discrete or cogenetic crystallization processes. The earliest phase (similar to 19-20 Ma), consisting of all three lithologies, have epsilon(Nd)(t) values ranging from -12.5 to -8.7, featuring pegmatites with the most depleted epsilon(Nd)(t) values and the earliest crystallization initiation relative to two-mica and muscovite granites. This challenges the general fractionation crystallization model, but suggests that the pegmatitic melts originate from volatile-rich sources within Higher Himalayan Crystalline Sequence (HHCS) metapelites under extensional decompression of South Tibet Detachment System (STDS). Subsequent pulse (similar to 17-18 Ma) also includes the three lithologies and displays comparable Nd isotope compositions (epsilon(Nd)(t) = -13.5 to -9.4) alongside systematic REE variations that reflect concomitant fractional crystallization of monazite and feldspar. In the latest pulse, the muscovite granites crystallized earlier (16.8-16.3 Ma) than the two-mica granites (16.2-15.6 Ma) and have higher epsilon(Nd)(t) values than the latter (-13.8 to -12.3 vs -15.4 to -13.3). Therefore, the apparently systematic variations in REE compositions do not testify fractional crystallization-controlled process but only illustrate respective crystallization processes of two melt batches. Importantly, the progressively lowering epsilon(Nd)(t) values with crystallization ages suggest an increasing incorporation of ancient Lesser Himalayan Sequence (LHS) material since 20 Ma, probably driven by the movement along the Main Central Thrust (MCT). These findings fundamentally challenge the recently proposed fractionation crystallization model regarding the relationship between the three lithologies of interest, rejecting the simplistic differentiation trends from two-mica granite through muscovite granite to pegmatite. Instead, we propose a dual-control mechanism (crustal anatexis and fractional crystallization) involving decompression melting of HHCS metapelites associated with STDS extension, combined with increasing LHS involvement over time, facilitated by MCT activity. By elucidating the potential for combining isotope and trace element information retained in monazite, our results demonstrate the unique capability of monazite to resolve melt source evolution during orogenic process. This research establishes a novel framework for investigating S-type granite petrogenesis in collisional orogens through integrated in-situ petrochronology and isotope tracer.

Ultrahigh-temperature (UHT) metamorphism represents one of the most thermally extreme types of crustal metamorphism on the Earth, providing a critical petrological archive to probe crustal evolution and geodynamics. While UHT metamorphism under the plate tectonics regime has been well established and linked to the Wilson Cycle, its thermal mechanisms under pre/non-plate tectonic regime (e.g., sagduction) preserved in Archean granite-greenstone terranes remain poorly understood. Here, we develop 2D thermomechanical numerical models and comprehensively evaluate two key controlling factors - crustal radiogenic heat production (RHP) and basal temperature. Through 36 parameter-space testing cases, we reveal that low RHP (1.0-1.6 mu W & centerdot;m(-3)) and low basal temperature (similar to 1100 degrees C) fail to generate sufficient crustal melting to form the typical granite-greenstone assemblage and the iconic dome-and-keel structure. In contrast, high RHP (2.2-2.8 mu W & centerdot;m(-3)) and high basal temperature (1100-1500 degrees C) result in intensive crustal melting and vigorous local convection in the lower crust. Under these conditions, supracrustal rocks and the lower crust become mechanically decoupled. Only a moderate RHP range of 1.0-1.6 mu W & centerdot;m(-3), combined with a basal temperature of 1300-1500 degrees C, can trigger the crustal-scale sagduction and formation of the dome-and-keel structure within 12-60 Myr, accompanied by localized UHT metamorphism. Within this parameter range, supracrustal rocks may be much easier to access UHT metamorphism with increasing RHP value. These results align with regional metamorphic data from the North China Craton. Our findings indicate that mantle plume and crustal radiogenic heat production synergistically controlled the Neoarchean crustal sagduction and UHT metamorphism in high-grade domains.

The Gaozhou region is situated in the southwestern Cathaysia Block of South China and represents the core of the Yunkai Terrane. Field geological mapping at a scale of 1:50,000 was undertaken for this study, coupled with geochemical analysis of both garnet-bearing and garnet-free biotite-plagioclase gneisses. Detailed petrography, mineral chemistry, and phase equilibrium modeling were further performed on garnet-biotite-plagioclase gneisses. Analytical results reveal that both garnet-bearing and garnet-free biotite-plagioclase gneisses share common geochemical features: high SiO₂ and Al₂O₃ contents, low TiO₂ content, low Na₂O/K₂O and Fe₂O₃T/K₂O ratios, high (La/Yb)N ratios, and negative Eu anomalies. These rocks are also depleted in Nb, Ta, Zr, and Hf, while showing enrichment in large-ion lithophile elements (LILEs) such as Rb, Th, and U. The inferred protolith is a sequence of clay-bearing greywacke with minor intercalated arkose, classifying it as a paragneiss. Based on petrological observations, two stages of metamorphic assemblage development in the garnet-biotite-plagioclase gneiss are identified: the peak assemblage of Grt+Pl+Bt+Kfs+Ms+L+Qz and the retrograde assemblage of Pl+Bt+Kfs+Ms+Qz. Constraints from mineral composition and phase equilibrium modeling yielded peak P-T conditions of 740-750 °C and 1.15-1.2 GPa, and the rocks subsequently experienced retrograde conditions below 650 °C. These findings define a clockwise P-T path involving cooling and decompression after the peak stage, indicative of an early crustal thickening event followed by rapid exhumation or uplift. Existing geochronological data place the timing of metamorphism in the Cathaysia Block during 460-400 Ma. Consequently, the metamorphic basement in the Gaozhou region recorded Early Paleozoic high-pressure amphibolite-facies metamorphism, revealing that the Yunkai Terrane was involved in the Caledonian crustal thickening event.

Identifying multi-phase metamorphism from Archean cratons and establishing the pressure-tempera ture-time (P-T-t) paths will provide notable insights into the geodynamic evolution of the early Earth. In this contribution, an integrated analysis of petrography, mineral chemistry, phase equilibria modeling, geothermobarometer and geochronology is conducted for felsic and mafic granulites from the Southern Jilin Complex (SJC), North China Craton (NCC). The results show that the rocks record two phases of metamorphism. The first phase is represented by the granulite-facies assemblage of Grt + Opx + Pl + Qz in both kinds of rock. The felsic granulite exhibits a clockwise P-T path with peak conditions of 8.6-11 kbar and 800-850 degrees C, while the mafic granulite shows an anticlockwise P-T path with peak conditions of 6.8-8 kbar and 735-770 degrees C. The second phase is recorded by an overprinting assemblage of Grt + Hbl + Bt + Pl + Qz in the felsic granulite, exhibiting a clockwise P-T path with peak conditions of 7.5-10 kbar and 680-756 degrees C. For the first-phase metamorphism, zircon U-Pb dating of felsic and mafic granulites yields ages of 2498 +/- 11 Ma and 2509 +/- 15 Ma, respectively, while hornblende 40Ar/39Ar dating of mafic granulite gives a cooling age of 2402 +/- 9 Ma. In-situ apatite U-Pb dating of felsic granulite yields a cooling age of 1742 +/- 13 Ma for the second-phase metamorphism. The coexistence of clockwise and anticlockwise P-T paths for the first-phase metamorphism may indicate a sagduction regime during the late Neoarchean. The second-phase metamorphism is inferred to be resulted from a late Paleoproterozoic collisional orogeny. Combined with previous data, this study documents a geodynamic transition in the NCC from pervasive vertical tectonism (potentially coexisting with horizontal tectonics) to dominant horizontal tectonism during the late Neoarchean to late Paleoproterozoic. (c) 2026 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Unraveling the tectono-thermal history of medium-to low-grade belts would place important constraints on the regional tectonic evolution. There exists a Barrovian metamorphic belt in the L & uuml;liang Group, Trans-North China orogen of the North China craton. Representative rock samples from chlorite zone, biotite zone, garnet zone, and staurolite-kyanite zone have been collected to delineate the pressure-temperature-time (P-T-t) evolution. A two-stage prograde P-T path characterized by heating first and then pressurizing is recovered from the garnet zone by phase equilibria modeling. The peak P-T conditions are constrained to be similar to 7.0 kbar and 560 degrees C. Decompression-dominated P-T paths involving peak pressure (6.8-9.2 kbar, 515-565 degrees C) and peak temperature (4.6-6.5 kbar, 560-615 degrees C) stages are obtained from the staurolite-kyanite zone. Metamorphic zircon from the staurolite-kyanite zone and garnet from the garnet zone yield U-Pb ages of 1850 +/- 31 Ma and 1882 +/- 67 Ma, respectively. Biotite from the biotite zone gives an 40Ar/39Ar age of 1762 +/- 3 Ma. The geochronological results indicate that metamorphism of the L & uuml;liang Group is younger than the formation age of the Trans-North China orogen (ca. 1.95 Ga) but is coeval with the subduction-collision orogeny (1.90-1.82 Ga) along the northern margin of the North China craton. The distribution of the Barrovian metamorphic belt is also parallel to the latter orogen (E-W trending). Consequently, combining these results with field observa tions and regional geological evolution, it is inferred that the genesis of Barrovian metamorphism in the L & uuml;liang Group may be related to the stress propagated from the 1.90-1.82 Ga orogeny. The heat sources and formation mechanisms of Barrovian metamorphism globally may vary case by case.

The Neoarchean era marks a pivotal period in Earth's tectonic evolution and continental crust formation. In this context, crustal architecture and structural patterns serve as key indicators for reconstructing Neoarchean geodynamic processes. The Western Shandong Province (WSP) granite-greenstone belt, located in the North China Craton (NCC), preserves well-exposed Neoarchean rock assemblages and provides valuable insights into the Neoarchean tectonics. In this study, we conducted systematic geological mapping and detailed structural analysis, integrated with LA-ICP-MS zircon U-Pb geochronology, in the Qixingtai region of the WSP. Three stages of compressional deformation (D1 to D3) were identified. The earliest deformation D1, predating similar to 2663 Ma, is characterized by NW-SE-trending, sub-vertically penetrative S1 foliation in early Neoarchean supracrustal rocks and TTG rocks, indicating an initial NE-SW compressional regime. This was followed by a regional extension during 2.60-2.55 Ga and deposition of the Shancaoyu Formation during 2.55-2.52 Ga. The subsequent deformation D2 (similar to 2520-2514 Ma) progressively overprinted earlier structures and generated NW-SE-trending upright isoclinal folds in late Neoarchean supracrustal and TTG rocks, indicating a consistent and prolonged compressive stress field. The last deformation D3, occurring around similar to 2500 Ma, resulted in the development of ductile shear zones of variable scales along the major lithological boundaries and generated regional L-S tectonites with nearvertical foliation and horizontal lineation. Our results suggest that the WSP experienced a long-lasting NE-SW compressive stress field throughout the Neoarchean but lacks diagnostic features of typical subduction or collisional belts. Combined with previous studies, we propose a tectonic model for the tectonic evolution of the Qixingtai area. This area initially developed from an oceanic plateau in the early Neoarchean, experienced regional extension in the middle Neoarchean, and ultimately underwent extensive magmatism and horizontal shortening during the late Neoarchean.

Although the early tectonic regime of the Earth remains debated, it is generally accepted that the geodynamic system underwent a notable transition during the Neoarchean-Paleoproterozoic. Here, we establish the metamorphic database for the North China Craton, comprising 446 valid data (83 Neoarchean and 363 Paleoproterozoic), which are categorized into high, intermediate, and low types based on the thermobaric ratio (T/P). This framework is used to investigate the thermal history, tectonic evolution, and the initiation of plate tectonics during this period. The results show that the North China Craton is dominated by high and intermediate T/P metamorphism, with only limited low T/P metamorphic records appearing in the late Paleoproterozoic. The Neoarchean-Paleoproterozoic thermal evolution of the North China Craton is overall consistent with the global thermal evolution trend, suggesting a transition from ancient-style plate tectonics to modern-style plate tectonics. The Paleoproterozoic metamorphic T/P curve exhibits relatively lower thermobaric ratios at 2.0-1.95 Ga (similar to 1.97 Ga) and similar to 1.80 Ga, corresponding to two orogenic events: the collision and amalgamation of internal blocks within the North China Craton, and its final incorporation into the Columbia supercontinent. Furthermore, this study links the evolution of plate tectonics with Earth's solid-surface systems, providing new insights into material circulation processes.

The primary magma of Archean tonalite-trondhjemite-granodiorite (TTG) is considered to originate from the partial melting of mafic crust. This process is pivotal for deciphering the formation and evolution of the Archean continental crust. However, defining the TTG primary magma is challenging due to the superposition of magmatic evolution and subsequent geological events. Based on detailed field survey and sampling, and subsequent petrological, geochemical and isotopic analyses, as well as extensive data compilation, we recently identified a suite of TT (tonalite-trondhjemite) rocks in the eastern Hebei region. These rocks are indicative of a primary medium-pressure (MP) TT magma composition. LA-ICP-MS zircon U-Pb dating shows that the TT samples emplaced at 2560-2507 Ma and metamorphosed at 2494-2473 Ma. Geochemically, these TT samples exhibit typical characteristics of MP-type TTG, with moderate SiO2 (56.1-64.7 wt%) and Al2O3 contents (15.5-17.5 wt%), elevated Na2O contents (4.04-5.17 wt%), low MgO contents (1.03-3.36 wt%), insignificant Eu/Eu* anomalies (0.94-1.1), near-chondritic Nb/Ta ratios (14.8-19.4), homogenous Dy/Yb ratios (2.10-2.75), and low Sr/Y (30.1-105) and (La/Yb)N (7.45-30.1) ratios. Whole-rock Nd and zircon Hf isotopes indicate that their precursors were extracted from the depleted mantle at 2850-2650 Ma. By combining experimental petrology findings, geochemical data with Ti-in-zircon thermometer calculations, we suggest that these samples most likely originated from the partial melting of the mafic lower crust (ca. 10-12 kbar) in a high-temperature and dry to damp environment, with amphibole, plagioclase, and minor garnet as residual minerals. Their compositions have not been significantly influenced by magmatic mixing, contamination, and fractional crystallization (e.g., plagioclase or amphibole). Amphibole barometer calculations indicate that these MP-type TT magmas may have been emplaced at a mid-crustal depth of 20-26 km. Compared with globally reported TTG primary compositions, we propose that these TT samples can serve as archetypes of MP-type TT primary magma formed by the partial melting of mafic lower crust in the late Neoarchean. They could provide valuable insights in further examining the characteristics and evolution of TTG primary magmas in other ancient cratons globally.

The Archean basement rocks in the Eastern Block of the North China Craton have undergone extensive granulite-facies metamorphism during the late Neoarchean to Paleoproterozoic. However, the geodynamic process and associated tectonic regime of this area remain poorly understood. The Qingyuan area of Northern Liaoning, located in the nucleus of the Eastern Block, plays a crucial role in unraveling the tectonothermal evolution by reconstructing its metamorphic history. Previous studies have mainly focused on the northern part of the area, while the tectonothermal evolution of the southern part remains unknown. In this study, we utilized petrography, phase equilibria modeling, and geochronology to constrain the pressure-temperature-time (P-T-t) paths of representative metapelite and metabasite samples of the area. Our results indicate that both samples have recorded anticlockwise P - T - t paths. The peak condition for the metapelitic rock sample 22QY02-9 is 10.0-11.2 kbar/800-815 degrees C. U-Pb zircon and monazite dating results indicate a post- peak metamorphic age of ca. 2470-2450 Ma. Metamafic rock sample 22QY04-3 reaches the ultrahigh temperature peak metamorphic condition of 11.5-12.5 kbar/920-950 degrees C, which is consistent with the results obtained from the ternary-feldspar thermometry calculations. U-Pb zircon dating reveals a cooling age of metamorphism at ca. 2487 Ma. By combining the data from this study with previous research, a sagduction model, operating under a non-plate tectonics regime, appears to be the most promising explanation for the most prevalent geological phenomena in the Neoarchean North China Craton.

The Neoarchean greenstone-granite rock association preserved in the Eastern Block of the North China Craton exhibits distinctive dome-and-keel structures. Although the metamorphic data from these rock assemblages provide valuable insights into the tectonic evolution of this region, the interpretation of the clockwise paths with nearly isothermal decompression (ITD) and the anticlockwise P–T paths involving near-isobaric cooling (IBC) remain inconsistent and controversial. By conducting 2D numerical models with the initial and boundary conditions similar to those of the Neoarchean Eastern Block, we investigated the coexistence of diverse P-T paths and determined their possible geodynamic regime. The model results demonstrate that the combination of crustal density inversion and heat from the high-temperature lower boundary initiates a crustal-scale sagduction process, leading to the formation of dome-and-keel structures. Additionally, we identified four primary types of P-T-t paths. Firstly, an anticlockwise IBC-type P-T-t path reveals the supracrustal rocks gradually subside to a deep crustal level, where they experience a prolonged residence period characterized by ambient mantle cooling without significant exhumation. Secondly, a clockwise ITD-type P-T-t path suggests the supracrustal rocks descend to the deep crust and are partly entrained by upwelling TTG magmas, leading to their rapid ascent to a middle crustal level. Thirdly, a newly identified crescent-type P-T-t path indicates an integrated burial-exhumation cycle, consisting of an initial burial stage with high dT/dP, followed by a rapid exhumation stage and a subsequent cooling stage exhibiting low dT/dP. Lastly, a hairpin-type P-T-t path highlights the slow exhumation rate experienced by deeply buried supracrustal rocks. The dome-and-keel structure and P-T-t paths observed in the numerical model are consistent with the geochronological, metamorphic and structural data of the Eastern Block. Based on these observations, we propose that the crustal-scale sagduction involving a mantle plume could responsible for the geological complexity of eastern China. This work was financially supported by the National Natural Science Foundation of China (42025204) and National Key Research and Development Program of China (No. 2023YFF0803804).

[Objective]Western Shandong is located in the core area of the eastern North China Craton and represents a typical Archean basement exposure.It extends as an overall NW-SE trending linear belt.This area preserves not only multiple phases of magmatic records spanning the early to late Neoarchean but also abundant anatectic-rheological structures overprinted by ductile deformation fabrics.These features are of great significance for understanding the Neoarchean tectonic evolution of the North China Craton.The Culai Mountain region is one of the most promising areas for such geological studies.Situated in the core of the tectonic belt(Belt B)of western Shandong,it is characterized by well-developed anatexis and ductile deformation.This makes it an ideal location for investigating the spatial and temporal relationships between crustal anatexis and ductile deformation.[Methods]In this study,we selected a representative migmatite outcrop at the Huangshiya Village and conducted systematic field structural analyses,petrographic observations,and LA-ICP-MS zircon U-Pb geochronology.[Results]Field observations show that the structural lineaments in this region exhibit an overall NW-SE orientation.Numerous felsic melts developed within the amphibolites,mainly as bands along the foliation,with a few occurring in a network-like or disseminated pattern.Flow folds are well-developed.Petrographic observations demonstrate that quartz grains are distributed along the irregular,corroded boundaries of K-feldspar and plagioclase,containing small melt pockets,bead-like quartzs,and melt films.These features collectively indicate intense anatexis in the region.The newly generated melts reduced the overall rock strength,making it more susceptible to subsequent ductile deformation.Concurrently,NE-SW-oriented horizontal compressive stress further promoted NW-SE regional extension,consistent with the nearly vertical foliation and sub-horizontal mineral stretching lineations observed in the amphibolite.This suggests a deformation regime dominated by near-oblate strain.To constrain the timing of the regional deformation,we conducted LA-ICP-MS zircon U-Pb dating on representative pre-,syn-,and post-tectonic samples of the area.The results indicate that the residual amphibolite records a melt crystallization age of～2503 Ma,representing the timing of the regional anatexis event.The syn-tectonic monzogranite yields a crystallization age of～2497 Ma,reflecting a syn-tectonic magmatic event,while the undeformed pegmatite veins formed at～2465 Ma,bracketing the regional ductile deformation at 2497-2465 Ma.[Conclusion]In summary,the western Shandong region experienced intense anatexis in the late Neoarchean,which was rapidly overprinted by near-oblate strain-dominated shortening deformation under NE-SW-oriented horizontal compressive stress.The anatexis further facilitated the development of NW-SE-directed ductile deformation.The superimposition of these two events ultimately shaped the structural pattern of the Neoarchean crust of the western Shandong region.[Significance]This study provides new constraints that improve the understanding of the Neoarchean tectonic framework and structural patterns of the western Shandong region.

The Cenozoic Himalayan granites are widely accepted as the anatectic products of crustal rocks. However, previous geochemical studies on their petrogenesis are mainly based on whole-rock analyses. Here we conducted a detailed petrographic, trace elemental and Sr isotopic investigations of apatite from the Middle Eocene (44-40 Ma) two-mica granites and subvolcanic porphyritic leucogranites of the Yardoi-Lhunze complex from the Tethyan Himalayan Sequence in the southeast Tibet, with the aim to constrain their magma sources and petrogenetic processes. The results show that apatites from the Quedang and Dala two-mica granites are characterized by euhedral to subhedral crystal shape, and have a wide range of initial 87Sr/86Sr ratios (0.7016-1.0088). They show significant negative Eu anomaly and varied concentrations of Sr and Y, indicating they are typical magmatic apatites. Apatites from the Qiaga porphyritic leucogranites can be divided into two groups based on Eu anomaly. Group-I apatites with positive Eu anomaly mainly display euhedral to subhedral crystal shape but with alteration rim, suggesting from the influence of hydrothermal fluids. Group-II apatites with negative Eu anomaly also have euhedral to subhedral crystal shape but they exhibit patchy or oscillatory zones, consistent with a magmatic origin. However, both group-I and II apatites have comparable initial 87Sr/86Sr ratios, 0.7198-0.9966 and 0.7174-0.9999, respectively. Previous studies based on whole-rock petrology and geochemistry have suggested that the Quedang and Dala two-mica granites and the Qiaga porphyritic leucogranites represent cumulates and fractionated melt-rich magmas, respectively. This is evidenced by systematic variations between Sr, Y, (La/Sm)N and Eu/Eu* in magmatic apatites from Quedang and Dala, consistent with the fractionation crystallization of plagioclase and monazite. Apatite has a wide range of initial 87Sr/86Sr ratios (0.7016-1.0088), far exceeding the range of whole-rock records (0.7011-0.7204). Notably, most of the analyzed apatites show lower range of initial 87Sr/86Sr ratios consistent with locally exposed amphibolites (0.7109-0.7332). The remaining small portion of apatites have initial 87Sr/86Sr ratios falling within the data range of the locally exposed metapelites (0.8517-0.9527). Therefore, the investigated granites have mixed magma sources dominated by amphibolites with subordinate metapelites. This can be inferred by apatite Sr isotopes alone, but not by whole-rock Sr isotopes alone. Our investigations highlight that in-situ geochemistry of apatite can provide a powerful means to unravel the mixed magma sources and complicated magmatic processes for granites.

本文总结了现阶段前板块构造与大陆起源研究的三大重要进展:（1）提出了地幔柱构造、重力凹沉构造和热管构造的前板块构造模式;（2）揭示了非板块构造与板块构造的标志;（3）发现了地球早期层圈演化地质记录.但是,现有的前板块构造并不能完美解释太古宙大陆的起源,板块构造在解释大陆起源与演化方面也遇到重大挑战.此外,阐述了我国开展前板块构造与大陆起源研究的必要性、研究优势及风险,并凝练了目前前板块构造与大陆起源研究的关键科学问题:（1）地球是先有陆还是先有板块构造;（2）海陆的形成是否同步;（3）冥古宙陆壳和英云闪长岩-奥长花岗岩-花岗闪长岩（tonalite-trondhjemite-granodiorite, TTG）的起源.基于学科发展,提出动力学热模拟和比较行星学在前板块构造与大陆起源研究中的重要性.在此基础上,认为未来5～10年前板块构造与大陆起源的研究重点领域为:（1）大陆的起源及其对早期地球环境和生命的影响;（2）前板块构造样式及其形成机制;（3）太古宙的构造热体制及热演化;（4）前板块构造与类地行星演化.

Eclogite and blueschist are important monitors of subduction zone processes and can record complex polymetamorphic histories during the protracted evolution of subduction systems. However, the rarity of such high-pressure, low-temperature metamorphic rocks in the Indus-Yarlung suture zone of the Himalaya hinders our understanding of the convergence of India and Asia. Here, we examine high-pressure, low-temperature metamorphic rocks from the Milin area of the eastern Indus-Yarlung suture zone. A comprehensive microtextural, mineral chemistry, and phase-equilibrium modeling investigation shows that low-temperature eclogite-facies metapelites with different parageneses (garnet-mica schists) experienced a cold subduction history along a lowthermal gradient, with peak pressures of ,, 1.6 GPa at ,, 550 degrees C. This represents an approximate thermal gradient of ,, 10 degrees C km - 1 . After peak pressure, these rocks underwent a two-step exhumation history with initial exhumation accompanying heating at ,, 590-600 degrees C and ,, 0.8-1.0 Gpa; this was followed by the second stage of exhumation to lower amphibolite-facies conditions. We interpret these low-temperature eclogitefacies metapelites to represent sedimentary rocks that overlaid Neo-Tethyan oceanic crust during subduction. Exhumation paths of high-pressure, low-temperature rocks in the eastern Indus-Yarlung suture zone include an amphibolite-facies overprint, which is absent from high-pressure, low-temperature rocks in the western Indus-Yarlung suture zone. This result is caused by the different timing of exhumation relative to the terminal collision of India and Asia.

The Early Paleozoic Orogeny in eastern South China has been highly controversial. It has been alternatively interpreted to have formed in an intra-plate setting driven by far-field tectonic forces or at plate boundaries involving subduction-collision. The West Cathaysia terrane in the core of the orogen is characterized by extensive magmatism, intense deformation and especially high-grade metamorphism. Identifying early Paleozoic high-pressure (HP) metamorphism and establishing a complete P-T-t path from the high-grade metamorphic rocks could help us understand the tectono-thermal evolution process and nature of the Early Paleozoic Orogeny. Here, we present results from a felsic granulite from the Chencai Complex in the northeastern West Cathaysia terrane. Petrographic evidence, mineral compositions and phase equilibria modelling indicate that the granulite underwent a pre-peak HP stage with P-T conditions of 13.3-14.7 kbar/696-718 degrees C and low geothermal gradients of 13-14 degrees C km(-1), and a peak high-temperature stage with P-T conditions of 9.711.0 kbar/785-820 degrees C. A clockwise P-T path involving pre-peak decompressional heating, post-peak near-isothermal decompression and near-isobaric cooling processes was constrained for the HP felsic granulite. In situ monazite U-Pb geochronology combined with previous results date these metamorphic processes at c. 440, c. 425 and c. 400 Ma, respectively. Our new metamorphic and geochronological data from the HP felsic granulite support the case that the Early Paleozoic Orogeny was a typical collisional one.

Water plays a critical role in the formation of granitic magmas and continental crust, but distinguishing water-present and water-absent anatectic scenarios using the geochemistry of granites is controversial. In this study we use an integrated approach that combines whole-rock major and trace element geochemistry, Ti-in-zircon thermometry, phase equilibrium modeling and trace element modeling to study the water regime that produced the Miocene granites from the Malashan-Gyirong area in central Himalaya to solve this controversy. The Gyirong granites have relatively low CaO, Sr and Ba and high Rb and (Sr-87/Sr-86)(i) and the Malashan granites have relatively high CaO, Sr and Ba and low Rb and (Sr-87/Sr-86)(i), and were classified as group A and group B granites, respectively. Following previous interpretation, group A and group B granites are consistent with the products of water-absent and water-present melting of metasedimentary rocks, respectively. Ti-in-zircon thermometry yielded maximum values of 761-796 degrees C for the Gyirong granites and 730-764 degrees C for the Malashan granites. Distinct variation trends in zircon trace element compositions indicate that these two groups of granites were not linked by crystallization differentiation. Using average compositions of Proterozoic pelite as starting materials, phase equilibrium modeling was carried out at a variety of P-T-H2O conditions typical of the Himalayan orogen, P = 5, 10 and 15 kbar, T = 600-800 degrees C, H2O = 0-10 wt%. Pelite can produce melts with coupled CaO-Na2O contents for both groups at 10 kbar. Specifically, constraints from compositions and temperatures require that the bulk H2O content is ca. 1-2 wt% for group A granites and > ca. 4 wt% for group B granites. Compared with the maximum structural water content of the pelite at 10 kbar (1.77 wt%), this study testifies that group A granites formed under water-absent conditions and group B granites under water-present melting conditions. Modeling shows that water-present melting can produce melts with high Sr-Ba and low Rb contents resembling group B granites, while water-absent melting can produce melts with low Sr-Ba and high Rb contents resembling group A granites. This study highlights that water can indeed cause differences in granite geochemistry but a comprehensive investigation is required to better determine the role of water during crustal anatexis.

The isothermal compression is a special prograde metamorphic P-T path in high-pressure rocks. However, the exact geodynamic processes and associated tectonic significance of this path remain unclear. The Mesozoic subduction and collision between the Sundaland Block and east Java-west Sulawesi (EJWS) generated various metamorphic rock assemblages, thus leading to the crucial need to understand the evolution of the Meso-Tethys. The Bantimala Complex is a key metamorphic basement in Western Sulawesi that preserves records of high-pressure (HP) to ultrahigh-pressure (UHP) metamorphism during Cretaceous subduction. This manuscript presents a detailed petrological, mineralogical, geochronological, phase equilibrium modelling, and Zr-in-rutile thermometry study of a garnet amphibolite from the Bantimala Complex. Petrographic observations indicate that the garnet amphibolite underwent three metamorphic stages that include prograde (M-1), peak (M-2), and retrograde (M-3a and M-3b) stages. Pseudosection modelling constrains the P-T conditions of these stages at 13-15.5 kbar/565-585 degrees C (M-1), similar to 23.5 kbar/588 degrees C (M-2), 8-9.5 kbar/410-480 degrees C (M-3a), and 8.3-8.8 kbar/415-440 degrees C (M-3b), respectively. UPb dating utilizing magmatic zircon reveals a protolith formation age of 212 +/- 3.1 Ma. Ar-40/Ar-39 dating results from sodic-calcic amphibole and phengite indicate the timing of HP metamorphism at 136-128 Ma (Early Cretaceous). In contrast to other HP metamorphic rocks in the Bantimala Complex (eclogite and blueschist), garnet amphibolite exhibits a unique counterclockwise P-T path that includes an isothermal compression stage. This implies that the rock likely detached from the upper plate and was transported to the lower plate within the subduction zone. Following peak metamorphism at a depth of approximately 75 km, it was exhumed along with other HP metamorphic rocks to a shallower crustal depth of approximately 25 km. Combined with the available data, this study also reveals the coexistence of diverse P-T trajectories within the Bantimala Complex, thus providing robust evidence for a Mesozoic subduction system between the Sundaland Block and Western Sulawesi (Indonesia).