Understanding continental crustal architecture and its control on mineral systems is fundamental to the earth sciences. Here we integrate zircon U-Pb geochronology, whole-rock Nd-Hf isotopes, lithogeochemical data, and regional metallogenic records from Cambrian to Triassic magmatic rocks across the Solonker-Alxa region of Inner Mongolia to define crustal domains and their metallogenic significance. Two contrasting isotopic provinces are identified: (1) an enriched domain [epsilon(Nd)(t) < -4, epsilon(Hf)(t) < 0] encompassing the North China Craton-Alxa Block and (2) a depleted domain [epsilon(Nd)(t) > -4, epsilon(Hf)(t) > 0] typifies the Central Asian orogenic belt (CAOB). These domains are separated by the Chifeng-Bayan Obo fault, the area north of Chaganhua, and the Quagan Qulu-Tebai fault. Crustal thickness patterns show a belt of thinned crust (<40 km) along the Mandula, Solonker, Ganqimandu, Yingba, and northern Enger Us fault zones, marking the boundary between the Mongolia collage and the Tarim-North China collage. Variations in crustal thickness suggest that the Alxa Block is a distinct Precambrian terrane, separate from the North China Craton. The protracted subduction-accretion and slab rollback of the Paleo-Asian Ocean have driven significant crustal growth in the Solonker-Alxa region, with juvenile crust contributions estimated at 37% in the southern CAOB. Crustal maturation and felsic differentiation resulted from polyphase melting events involving mafic lower crust, oceanic crust, and the middle to upper crust. A systematic correlation exists between isotopic domains, crustal architecture, and metallogenic distribution. Depleted domains with thin crust (<50 km) preferentially host porphyry Cu (+/- Au), epithermal Pb-Zn-Cu, and volcanic massive sulphide-type Cu deposits, whereas enriched isotopic domains and their peripheries contain porphyry Mo, skarn Cu-Fe, vein-type Au deposits, and magmatic Cu-Ni sulfide deposits, indicating genetic links to ancient crustal recycling and metasomatized lithospheric mantle. This synthesis provides a coherent tectono-metallogenic framework for the Solonker-Alxa segment of the southern CAOB and offers guidance for mineral exploration.

The association of metal minerals in skarn deposits is common, including Cu-Mo, W-Sn, and Cu-Au systems. Among these, Cu-W is notable for its zonation patterns, with Cu typically found in shallow zones and W in deeper regions. However, the formation of Cu-W co-mineralization remains debated, particularly whether it results from a single evolving fluid event. This study assesses the genesis, exploration potential, and timing of the Yongping stratabound skarn deposit in the South China Block (SCB), which hosts both Cu and W mineralization. Because garnets commonly form during the early prograde skarn stage, we use garnet mainly to constrain early skarn-forming fluid evolution, skarn zonation, exploration vectors, and the maximum age of Cu-W mineralization. The linear relationship between Y and REE in garnet, along with similar REE patterns across different mineralization sectors, indicates a closed fluid system derived from a single magmatic hydrothermal source. Garnet mineralogy reveals core-mantle-rim zoning patterns. Garnet cores are rich in Al, exhibit high heavy rare earth elements (HREE) and high field strength elements (HFSE) with low light rare earth elements (LREE)/HREE ratios, indicating a low water–rock ratio and acidic environment associated with early diffusion-controlled metasomatism. The mantles are enriched in Fe, show depleted HREE and HFSE, and have elevated LREE/HREE ratios with significant Eu anomalies, reflecting intense fluid interactions at higher water–rock ratios and infiltration metasomatism, which enhanced permeability and created favorable conditions for Cu-W mineralization. Garnet rims retain similar major-element features to the cores but show REE depletion and marked decreases in Fe and W concentrations, indicating a shift back to a low water–rock ratio due to fluid exhaustion and pH increase during neutralization reactions with carbonate rocks. This process may have triggered early W precipitation accompanied by limited Cu precipitation.Garnet zonation distal from unconformity indicates that garnets near the hydrothermal center in Yongping should have higher and more uniform Fe/Al ratios, elevated REE and LREE concentrations, lower Mn levels, and minimal oscillatory zoning. These features are consistent with observations in the southern sector, indicating favorable exploration potential.In-situ U-Pb dating of ore-related garnet yields ages of 161–158 Ma, recording skarn formation and providing a maximum age constraint on Cu-W mineralization. These Late Jurassic ages coincide with regional tectonic extension and the shift from Cu- to W-dominated metallogenesis in South China, suggesting that Yongping likely formed during this metallogenic transition.

Numerous Late Permian to Triassic porphyry molybdenum deposits have been identified along the northern margin of the North China Craton, distributed across both the North China Craton and the Central Asian Orogenic Belt units. However, significant variations exist in the sources of the ore-forming magmas for these deposits, and the cause of these variations remains poorly constrained. This study focuses on the Chaganhua Mo deposit, the largest in the northern segment of the Nuru-Langshan tectonic zone, and presents a comprehensive analysis of the ore-forming porphyry, including petrography, zircon U-Pb geochronology and If isotopes, whole-rock geochemistry, and Sr-Nd isotopes. The results indicate that the zircon U-Pb age of the Chaganhua porphyritic granite is 242 +/- 1Ma, which is consistent with the previously reported molybdenite Re-Os isochron age of 241.6 +/- 2.5Ma, suggesting that the granite and the Mo mineralization are contemporaneously formed. Geochemically, the analyzed samples of the rocks are characterized by high SiO2 (71.43%similar to 73.16%) and low MgO (0.41%similar to 0.52%), belonging to the high-K calc-alkaline and weakly peraluminous series. They are enriched in light rare earth elements and large-ion lithophile elements (e. g., Rb, Th, U, K, Sr), depleted in heavy rare earth elements and high-field-strength elements (e.g., Nb, Ta, P, Ti), and exhibit a weak negative Eu anomaly (Eu/Eu* = 0.59 similar to 0.67). Additionally, they show high Sr contents (282 x 10(-6) - 320 x 10(-6)) high Sr/Y (32.91 similar to 42.43) and (La/Yb) (22.57 similar to 28.01) ratios, indicating adakitic affinities. Although the samples exhibit relatively high initial Sr-87/Sr-86 ratios (0.705948 similar to 0.709485) and negative epsilon(nd)(t) values (-7.0 similar to -6.4), their Sr-Nd isotopic compositions distinctly differ from those of the ancient lower crust of the North China Craton. In addition, they have high K2O/Na2O ratios, zircon epsilon(Hf)(t) values (+0.0 similar to+4.5), low CaO/Al2O2, ratios and Mg-# values, as well as relatively young zircon IIf two-stage model ages (891 similar to 1131Ma). Integrated with reconstructions of regional crustal thickness evolution, we propose that the Chaganhua porphyritic granite is likely originated from the partial melting of thickened juvenile lower crust during the post-subduction tectonic stage, and underwent moderate crustal contamination during its evolution. Thus, the juvenile lower crust within the Central Asian Orogenic Belt can serve as a significant reservoir for porphyry Mo deposits. Comparative results indicate that the Mo-mineralizing magmas derived from this reservoir are markedly distinct, in terms of Nd-IIf isotopic and geochemical characteristics, from those generated by the melting of ancient continental crust within the North China Craton.

Segmented subduction redirects mantle flow and melt, controlling orogenic magmatism and deformation. The Elashan Tectonic-Magmatic Belt (ETMB) lies between the East Kunlun (EKOB) and West Qinling (WQOB) orogenic belts, linked to Triassic Paleo-Tethys subduction. We present geological, geochemical, zircon U-Pb geochronological, and Hf-Sr-Nd isotopic data from Triassic ETMB granites, supplemented by data from the EKOB and WQOB. The ca. 244 Ma Shiduolong granodiorites display high MgO and enriched aHf (t) (-6.8 to -3.6) values, indicating mixing between crust-derived felsic and mantle-derived mafic melts. The ca. 229 Ma Huda diorites, with low Sr/Y and depleted aHf (t) (-3.0 to -0.7) values, originated from a shallow juvenile lower crust at high-temperature conditions. The Saishitang complex comprises ca. 220 Ma quartz diorite porphyrites and granodiorites, plus ca. 215 Ma diorites. The quartz diorite porphyrites exhibit high-Mg andesite affinities and linear (87Sr/86Sr)i-SiO2 correlation, suggesting partial melting of enriched mantle peridotites with assimilation and fractional crystallization. The granodiorites display high-Mg adakitic characteristics formed by melting of delaminated lower crust. The diorites are geochemically similar to the Huda diorites but exhibit more enriched aHf (t) values (ranging from -9.2 to -4.8), suggesting an older and deeper crustal source. Notably, the 240-230 Ma ETMB granitoids record high aHf (t) values and a depletion trend, which is in contrast with the concurrent enrichment in the adjacent EKOB and WQOB. This implies that, although they were in a contiguous subduction setting, unique dynamics related to the asthenosphere upwelling occurred in the ETMB, related to a slab window between the EKOB and WQOB. The inferred slab window was likely produced by slab tearing, controlled by slab segmentation in response to an along-strike transition from slab rollback in the WQOB to a relatively low-angle subduction regime in the EKOB.

Lode gold deposits have contributed 40 % of the global gold endowment, and high-grade ore shoots within these deposits have long been of great interest. However, the mechanisms of gold remobilization and efficient deposition, which are critical for understanding the genesis of high-grade gold shoots, remain hotly debated. Here, we present a combination of micro-textures and in-situ compositions of pyrites from the Sidaogou gold deposit (up to 1000 g/t Au), North China Craton, to construct a genetic model for high-grade gold shoots. Six texturally distinct generations of pyrite from four mineralization stages are identified and visible gold dominantly exists as inclusions or microfracture infillings in pyrites from stages 2 and 3. In-situ trace element analyses show that pyrite from stage 1 (Py1) has high contents of Co and Ni with moderate As (median = 154 ppm) and negligible Au (0.04 ppm). Porous Py2a in stage 2, sometimes enclosing Py1, is featured by numerous galena inclusions and elevated Au (median = 0.18 ppm) and As (536 ppm) concentrations. Euhedral to subhedral Py2b corrodes Py2a and exhibits much higher Au (median = 4.16 ppm) and As (11350 ppm) accompanied by fewer pores and mineral inclusions. In contrast, anhedral Py3a from stage 3 contains abundant pores and inclusions with depleted Au (median = 0.05 ppm) and As (84.3 ppm). However, Py3b shows significant increases of Au (median = 1.77 ppm) and As (5146 ppm) again and corrodes Py3a with some pores and inclusions of polymetallic sulfides. Euhedral Stage 4 pyrite (Py4) has lower Au (median = 0.26 ppm) and As (1814 ppm) contents relative to Py3b. Above porous and corroded textures indicate multistage coupled dissolution-reprecipitation (CDR) reactions triggered by an oxidation process related to fluid boiling, which is aligned with decreasing trends of delta S-34 values from Py1 (average 9.2 parts per thousand) to Py2b (7.8 parts per thousand) and from Py3a (10.0 parts per thousand) to Py3b (8.7 parts per thousand). Further evidence is recorded by distinct decoupling of elements (As-Cu) and element pairs (Au-As vs. Co-Ni) as well as high As/Sb (most > 20) but low Tl/Cu (< 0.05) ratios in Py2a to Py3b. Mass balance calculation suggests that Au-rich pyrites (Py2b and Py3b) and coexisting visible gold are impossible to primarily sourced from gold remobilization of pre-existing pyrites. Instead, the high-grade gold shoots should be dominantly attributed to efficient gold deposition triggered by fluid boiling. This study highlights the conjunction of multiple processes, a primary gold enrichment via CDR reactions and subsequent efficient gold deposition by fluid boiling, to generate the high-grade ore shoots in large lode gold deposits.

The temporal and genetic constraints of Ta-Nb mineralization in highly fractionated peraluminous granites are vital for understanding the formation mechanisms of these deposits. Cassiterite present in these granites becomes a reliable U-Pb geochronometer and is rich in Ta, Nb, and other trace elements, whose variations may reflect the magmatic-hydrothermal evolution of these systems. This study investigates the mineralogy, geochronology, and geochemistry of cassiterite from the Yashan granite pluton, which hosts the Yichun Ta-Nb-Li deposit, to determine the timing and evolutionary processes of this system. Cassiterite is predominantly of magmatic origin, with minor magmatic-hydrothermal and hydrothermal subtypes. Magmatic cassiterite yields U-Pb ages of 148.5 f 0.9 Ma for the Li-mica granite, 148.0 f 1.0 Ma for the topaz-lepidolite granite, and 148.5 f 2.1 Ma for the granite dikes, overlapping with that of 149.5 f 2.6 Ma for hydrothermal cassiterite from the Li-mica granite. Magmatic cassiterite formed after extensive fractional crystallization and magma degassing, exhibiting textures characterized by multiple dissolution and overgrowth features that suggest episodic fluid oversaturation and degassing events. Distinct compositional trends observed in magmatic cassiterite, along with the various subtypes of hydrothermal cassiterite in each rock type, suggest independent evolution of each intrusion following its emplacement. Early saturation of columbite in these granite units is evidenced by the texture and composition of magmatic cassiterite. Tantalite reached saturation during the crystallization of magmatic cassiterite in the Li-mica granite, but not in the topaz-lepidolite granite and granite dikes. Its saturation in these latter two granitic lithologies was ultimately achieved due to the accumulation of Ta in the melt and the concomitant reduction in its solubility resulting from magma degassing(s).

Snowball quartz is commonly found in highly fractionated peraluminous granites that may be associated with mineralization of Ta, Nb, Li, W, Sn, and Rb. The genesis of snowball quartz has been a subject of controversy, and its genetic relationship with potential rare metal mineralization remains poorly understood. This work presents a study of the mineralogy and chemistry of quartz and plagioclase from the Yashan pluton in southern China. The Yashan pluton hosts the Yichun Ta-Nb-Li deposit and is primarily composed of two-mica granite, Li-mica granite, and topaz-lepidolite granite, which were intruded by granite dikes. The texture known as "snowball" is observed in quartz from Li-mica granite, but it is more frequently and prominently developed in quartz from topaz-lepidolite granite and granite dikes. This texture is characterized by the zonal arrangement of prismatic albite (referred to as snowball albite) within quartz phenocrysts, with the {010} face of snowball albite preferentially adhering to the crystal faces of quartz. It typically develops in specific domains of the mantle and/or rim of quartz phenocrysts, and occasionally in their cores. The snowball texture is preferentially developed on the prism faces (m) of quartz, as indicated by a higher abundance of snowball albites on these faces compared to others. The snowball-textured quartz domain (SBTQD) is texturally similar to other domains from the same growth zone and chemically overlaps with magmatic quartz cores or rims. The snowball albites are chemically indistinguishable from magmatic albite inclusions entrapped within quartz cores. These pieces of evidence suggest that the SBTQDs have a magmatic origin. Given the specific morphologies of snowball quartz (well development of prism faces) and albite (prismatic with a high aspect ratio of similar to 5-10), along with the development of sector zoning in quartz, it is proposed that the snowball quartz formed as a result of rapid growth of quartz and albite under moderate under-cooling (Delta T = 50-100 degrees C) at near-solidus conditions, which was associated with multiple episodes of magma degassing. From the perspective of Ta-Nb mineralization, this degree of undercooling would significantly reduce the solubility of tantalite by more than 70-90%, thereby facilitating its crystallization. This process also promotes the further crystallization of already saturated columbite. Therefore, snowball quartz could serve as an exploration indicator for Ta-Nb deposits associated with highly fractionated peraluminous granites.

The hydrogeochemistry of geothermal fluids is fundamental to reveal the genesis, recharge mechanism and circulation pattern of geothermal water. However, the origin and hydrogeochemical process of geothermal water in deep aquifer system still remain unclear. In this study, 17 water samples were analyzed to study the origin, recharge and mixing process of geothermal water in the Yinchuan basin by using a hydrogeochemical and isotopic approach. The results showed that the concentrations of major ions (SO42 , Na+, Cl , TDS, Ca2+, K+, Mg2+ and NH4+) and trace elements (Li, F , Br , I , Sr and Mn) in geothermal water are significantly greater than those in shallow water, hot spring and cold spring in the study area. The hydrochemical type of geothermal water is dominated by Cl & sdot;SO4-Na, which is mainly influenced by dissolution of halides, chlorides and sulfates under strong fluid-rock interactions. The isotope analysis demonstrated that the atmospheric precipitation in the Helan Mountain area is the major recharge source of geothermal water, the recharge elevation is 1118 m-1133 m, and the deep geothermal water is formed by a mixing process of ancient precipitation and modern precipitation. The silica-enthalpy mixing model suggested that the reservoir temperature of deep geothermal fluid is between 110 degrees C and 175 degrees C, and the mixing ratio of cold water is about 54 % to 92 %. The present study sheds some light on the genesis, recharge mechanism and hydrogeochemical evolution of geothermal water in deep aquifers, which are vital for sustainable exploitation and utilization of geothermal resources.

Interpreting the origin and magmatic-hydrothermal processes of highly fractionated granites can provide important information about crustal evolution and lithium (Li) mineralization. Our study focuses on the Yifeng-Fengxin deposit of South China, a newly discovered world-class Li deposit with >11 Mt of Li2O resources. We present zircon ages from different granite phases hosting the deposit and define three types of zircons characterizing the main stages of magmatic-hydrothermal activity, which spanned 153 Ma to 102 Ma. Dating of paragenetically well-constrained zircons shows that Li mineralization mainly occurred during three periods: 144-139 Ma, 133-131 Ma, and 105-102 Ma. Based on the analysis of Nd-Hf isotopic compositions from multiphase granites, the ore-related Ganfang granitic complex in the Yifeng-Fengxin district derived from the Proterozoic crust and juvenile crustal materials with the input of minor mantle-derived magmas. The formation of these granites could have resulted from multiple episodes of high-temperature (>600 degrees C) magma recharge from a deep reservoir. The enrichment of siderophile elements (Sc and Ti) in zircons may have resulted from the recharge of mantle-derived magmas and remelting of mafic-ultramafic rocks. The residual magmas evolved to low states of oxygen fugacity (Delta FMQ < 1). Trace element distributions, especially rare earth element (REE) + Y with P, and electron probe microanalysis (EPMA) mapping, indicate that zircon grains in the highly fractionated magmatic system have complex charge balances. The charge balances may be provided by Li, U, Ca, Sc, P, Y, and REEs from Li-rich melts. These data support an Li preenrichment process in early granitic melts, and hydrothermal overprinting and redistribution in the late stage. We propose that hydrothermal remobilization plays a crucial role in the formation of economic Li deposits. Zircon can be used as a microfingerprint to reveal the magmatic-hydrothermal evolution of highly fractionated granites and associated rare metal deposits.

The geochemical measurement of stream sediments is an important technical method in the process of mineral exploration.The extraction method of geochemical anomalies of stream sediments based on the division of river basins can be used to effectively delineate the relevant geochemical anomalies for providing favorable information to the mineral prospecting.Based on the high-precision GDEMV2 30M resolution digital elevation data,the study area is reasonably divided into several small watersheds by using the Arcgis software,then the geochemical anomalies in those small watersheds are calculated.The residual deviations are calculated based on contents of samples in the outlets of each sub-basins,and the corrected residual deviations are obtained by performing the slip attenuation correction.Then the calibrated residual deviation values of Cu-Pb-Zn and Au-Cu-Zn element associations are calculated by using the factor scores of Au,Cu,Pb and Zn elements,respectively.On the above basis,the anomalous sub-basins are outlined by using the cumulative frequency method.The experimental results show that it is feasible to calculate the residual deviations by taking contents of samples in the outlets of sub-basins as benchmarks using the method for extracting geochemical anomalies of stream sediments in sub-basins.The anomalies extracted by using this method are highly consistent with spatial locations of the known ore sites ore mineral occurrences.They can be used to provide effective guidance for mineral prospecting.

Lode gold deposits hosted by ductile-brittle shear zones account for more than onethird of the world's gold production. Highgrade ore shoots from this type of deposit are the most critical exploration targets. The ore shoots can form through the post-depositional deformation of auriferous sulfides or overprinting of ore fluids accompanied by coupled dissolution-reprecipitation (CDR) reactions. However, the mechanism that dominates ore shoot genesis remains unknown, primarily due to the controversial single progressive or polyphase nature of ore-bearing shear zones. Here, we report on geological and geochemical analyses we conducted at the large Hetai goldfield, South China, to construct an accurate gold upgrading model for the formation of ore shoots. Stages 1-3 of mineralization at Hetai show features typical of ductile shearing, while Stage 4 is characterized by quartz-sulfide veinlets in brittle fractures. 40Ar/39Ar ages of ca. 184 Ma and 157 Ma for the mineralization of stages 1and 4 overlap with the regionally dextral ductile brittle shear that occurred during ca. 210- 162 Ma. Thus, the gold event at Hetai should have been controlled by a single progressive ductile-brittle shear episode, rather than polyphase structural events. The auriferous fluids at Hetai precipitated minor invisible gold in pyrites (mean 0.173 ppm) produced during stages 1-4 through fluid-rock interaction. The systematic increase of elements Au, As, Sb, Bi, Ag, and Cu and delta 34S values in ductile-deformed pyrites from stages 1-3 indicate that early invisible gold upgrading should be the result of the post-depositional remobilization of auriferous sulfides during the long-lived ductile-brittle transition. Cataclastic pyrites hosting invisible gold from Stage 4 have zoned and porous mantles with elevated invisible gold (mean 0.503 ppm) and Sb, Bi, Pb, Co, Ni, and Ti contents. These pyrites are further replaced by chalcopyrite and pyrrhotite with increasing invisible gold, Co, and Ni contents. In addition, numerous visible native gold grains in Stage 4 are included in sulfides formed by replacement and develop along the microfractures and grain boundaries of these sulfides. We suggest the late invisible and visible gold upgrading events in Stage 4 can be attributed to the auriferous fluid superposition and subsequent replacement of pyrite via CDR reactions in a brittle regime. Therefore, the gold upgrading process at Hetai is jointly caused by the early remobilization induced by ductile-brittle deformation and the late ore fluid superposition with accompanying CDR reactions within a brittle domain. As the ore fluid superposition and CDR reactions in Stage 4 produce a significant amount of visible gold, they exert a first-order control on the genesis of ore shoots at Hetai. The refined model may be widely applicable to lode gold deposits elsewhere and can be used to identify regions with promising exploration targets.

Fluoride-silicate melt immiscibility has been proposed as an important control on light rare earth element (LREE) and Y enrichment in a peralkaline granite (e.g., the Strange Lake pluton in Canada). It remains uncertain, however, whether this immiscibility is a requirement for ore formation in mineralized peralkaline granites globally. In this contribution, we present an integrated mineralogical and chemical study of the REE-Zr-Nb-Be–mineralized Baerzhe peralkaline granite pluton, northeast China. We focus on the mineralogy and chemistry of amphibole and the bulk-rock geochemistry to investigate whether the metal enrichment at Baerzhe was facilitated by fluoride-silicate melt immiscibility or simply resulted from fractional crystallization. The Baerzhe pluton comprises, from early to late, a fine-grained hypersolvus granite, a porphyritic hypersolvus granite, and a transsolvus granite that evolved to pegmatite and a comb-textured amphibole unit. Hypersolvus granite enclave(s) can also be found within the transsolvus granite. The amphibole in these granitic units is arfvedsonite, providing evidence of fractional crystallization, magma mingling, fluoride melt immiscibility, fluid exsolution, and degassing. The presence of fluoride melt inclusions in arfvedsonite indicates that fluoride-silicate melt immiscibility took place in all units of the pluton except for the transsolvus granite, where rare metal mineralization occurs, and in pegmatite. The immiscibility was particularly intense in the porphyritic hypersolvus granite but very weak in other rock units, as evidenced by the abundance of fluoride melt inclusions in the former and lack of them in the latter. Most fluoride melt inclusions are rich in Ca and are enriched in LREEs, middle REEs (MREEs), and Y relative to heavy REEs (HREEs). The estimated volume of fluoride melt in the porphyritic hypersolvus granite was less than 1 wt %, storing about 2 to 6 wt % LREEs and up to 8 to 15 wt % MREEs and Y. The exsolution of fluoride melt, however, does not appear to have affected the trends of increasing concentrations of REEs and high field strength elements (HFSEs) in the coexisting silicate melt, which were driven by intense fractional crystallization of alkali feldspar, quartz, and arfvedsonite. Furthermore, the absence of fluoride melt inclusions in the transsolvus granite and pegmatite, together with their scarcity in the comb arfvedsonite unit, suggests that the early formed immiscible fluoride melt did not accumulate in the residual silicate melt. Fluoride melts appear to have played a limited role in the concentration of LREEs and Y to form the Baerzhe deposit. Instead, fractional crystallization of silicate minerals exerted a dominant control on the enrichment of REEs and HFSEs by factors of five to 20.

The Central Asian orogenic belt is considered to be the largest Phanerozoic accretive orogenic belt on Earth. The late Paleozoic magmatic rocks in central Inner Mongolia are crucial for understanding continental crust growth and the tectonic evolution of the southeastern part of the Central Asian orogenic belt. We present comprehensive geochemical, isotopic, and geochronological data from three late Paleozoic magmatic units in the Mandula area, west of the Solonker suture zone. Zircon U-Pb dating indicates that these rocks formed during the late Carboniferous (316-304 Ma). The Mandula high-Mg diorites exhibit high MgO (3.9-6.5 wt%), high Mg# (61-69), and depleted Nd-Hf isotopic compositions, generated through interaction between a metasomatized mantle and slab melts with the overlying sediments. The Mandula granodiorites display adakite geochemical characteristics with high Sr/Y mass ratios (29-52), high MgO (1.7-2.2 wt%), and high Mg# (52-54), formed by partial melting of the oceanic slab with the addition of overlying sediment. Mafic microgranular enclaves have consistent ages, Sr-Nd-Hf isotope compositions, and hornblende crystallization temperature-pressure conditions with their host granodiorite, formed from a cognate magma associated with the host granodiorites through cumulate. We propose that two phases of slab rollback took place during the late Paleozoic southward subduction-accretion of the Paleo-Asian Ocean. The first phase corresponded to the transformation of low- to medium-angle slab subduction, while the second phase led to subduction-related extension. Considering the tectonic-magmatic evolution, crustal maturity, and thickness variations in the late Paleozoic southeastern part of the Central Asian orogenic belt, we propose that prolonged subduction and slab rollback promoted continental crust growth. The Central Asian orogenic belt coincides temporally and spatially with the Phanerozoic Pangea cycle, suggesting that continuous subduction and supercontinent amalgamation significantly contributed to continental crust growth.

Superconducting undulators (SCUs) are increasingly vital for synchrotron light sources and free-electron lasers in modern particle accelerators due to their ability to surpass the performance limitations of traditional permanent magnet undulators (PMUs). This paper delves into the theoretical framework and key technologies of SCUs, substantiating findings with experimental verifications. The theoretical analysis and numerical simulations of SCU magnetic fields are conducted based on Maxwell's equations, leading to optimized magnetic field distributions. Advanced manufacturing processes, such as high-precision coil winding and epoxy resin impregnation, are developed and refined. The paper also details the SCU’s cryogenic, power supply, quench protection, vacuum, and magnetic field measurement systems, ensuring safe and stable operations in real-world conditions. Prototypes, including 1.5-meter-long SCUs, undergo rigorous tests at liquid helium temperatures to validate reliability, revealing that while the SCU meets the design goals in both the vertical and horizontal states, gravity effects in the horizontal state deteriorate the quality of the magnetic field and require iterative optimization. The improvement of the magnetic field quality is achieved by locally adjusting the tuning gap and the end correction coils. Despite the advances that have been made, it is essential to further enhance the performance of SCUs by optimizing the end design and adding means to regulate the magnetic field at low temperatures. This study lays a solid theoretical and technical foundation for the application of SCUs in advanced light sources, and is expected to provide a meaningful reference for the development of more SCUs in the future.

Taking advantage of a higher field than a conventional permanent magnet undulator, superconducting undulators (SCUs) have been rapidly developed in recent years for applications at synchrotron radiation sources and free-electron lasers. The Institute of High Energy Physics, Chinese Academy of Sciences, has developed a 1.5-m long planar SCU with a short period of 15 mm. This SCU has been commissioned and optimized in the horizontal position. In contrast to the vertical position, where the undulator coils are immersed in liquid helium for superconductivity, the horizontal test requires the assembly of the complete device, including the cryostat, current conductor, cryocooler, vacuum chamber, and undulator coils. This test reflects the operation status and measures the SCU's characteristics under working conditions. Although experiences from the vertical test provided good guidance for horizontal optimization, special care needs to be taken for effects such as gravity. After improving field uniformity through iterative measurements, the rms phase error of the SCU is reduced to 7.3 degrees at a current of 400 A. Additionally, the functions of the end correction coils to mitigate field integral errors have been verified. This paper also demonstrates and analyzes other phenomena and interesting observations during the commissioning process. It discusses important issues that impact field quality and measurement accuracy and suggests further improvement measures for an even better field.

The mechanism of the Triassic continental crust growth in the East Kunlun Orogenic Belt (EKOB) is highly controversial. In this contribution, we present comprehensive data on the Yuegelu granodiorite and its mafic microgranular enclaves (MMEs) from the eastern segment of the EKOB, including zircon U-Pb geochronology and Hf isotope, mineral chemistry, whole-rock geochemistry and Sr-Nd isotopes, and in situ plagioclase Sr isotope, to constrain the genesis of these rocks and shed new insights on the continental crust growth. The MMEs are coeval with the host granodiorite at similar to 240 Ma and display abundant quenching textures such as acicular apatites and quartz phenocrysts rimmed by amphibole. They typically exhibit low SiO2 but high TiO2, Fe2O3T, MnO, and MgO concentrations and have similar Sr-Nd-Hf isotopic compositions to the host rock. We suggest that the Yuegelu MMEs are late cognate cumulates derived from the same parental magma with the host rock as a result of pressure quenching rather than the hybrids of crustal and mantle magmas. The granodiorite is medium- to high-K calc-alkaline, metaluminous I-type granite with relatively high SiO2, but low Al2O3, CaO, and Fe2O3T contents. The granodiorite is enriched in Rb, K, and Pb but depleted in Nb, Ta, Sr, P, and Ti, resembling a bulk continental crust. However, Yuegelu granodiorite has much more depleted Sr-Nd-Hf isotopic compositions than those of the mature crustal materials, indicating a significant mantle contribution. Based on Sr-Nd isotopic modeling, the Yuegelu granodiorite could be generated by partial melting of the Paleo-Tethys Oceanic crust (similar to 80%) with the overlying terrigenous sediments (similar to 20%). The partial melting of oceanic crust fragments in the syn-collisional setting in the Middle Triassic contributed substantially to the continental crust growth in the EKOB.

Supplemental Text S1: Analytical methods; Figure S1: Plots of variation of selected trace elements vs. Zr to check for element mobility during postmagmatic alteration; Table S1: Zircon U-Pb data sources for Paleozoic to early Mesozoic intrusive rocks in central Inner Mongolia; Tables S2 and S3: Whole-rock major-element and trace-element geochemistry, and Sr-Nd isotopic compositions; Tables S4 and S5: Zircon U-Pb-Hf isotopic data; Table S6: EPMA results of amphibole from the late Carboniferous Mandula intermediate to acidic composite pluton; and Table S7: Summary of crustal thickness calculation in central Inner Mongolia.

The Wutuogou Ag-Pb-Zn deposit, a newly discovered vein-type deposit, is located in the Eastern Kunlun Orogenic Belt (EKOB), northwestern China. The vein-type Ag-Pb-Zn ore bodies are hosted in Middle Triassic granodiorite and monzogranite and are characterized by high-grade Ag, Pb, and Zn (average Ag: 293 g/t, Pb: 3.00 %, Zn: 2.85 %). Three paragenetic stages have been recognized: quartz + pyrite (Py-1) + arsenopyrite (stage I), pyrite (Py-2) + sphalerite + chalcopyrite + tetrahedrite + quartz (substage II-1), galena + pyrargyrite + freibergite + freieslebenite + quartz + calcite (substage II-2), and quartz + calcite (stage III). Except for Ag-bearing minerals (pyrargyrite, freibergite, and freieslebenite), invisible silver is also present in pyrite (1.91-165 ppm), sphalerite (3.86-8806 ppm), and galena (up to 0.21 wt%). The calcite is closely associated with sulfides in substage II-2 and yields a U-Pb age of 210 +/- 7 Ma (MSWD = 2.7), which represents the ore-forming age (lower limit). Py-1 displays higher As contents and lower Co contents than those of Py-2, indicating a decrease in temperature from stage I to stage II. In addition, the Fe/Zn mass ratios (0.025-0.075) of sphalerite estimate the fluid temperature for substage II-1 of 246-284 degrees C, whereas the Ag/(Ag + Cu) and Zn/(Zn + Fe) mole ratios of freibergite estimate the fluid temperature for substage II-2 of 140-270 degrees C, further indicating the decrease of temperature from stage I through substage II-1 to substage II-2. Mineral assemblages of pyrite-chalcopyrite-tetrahedrite in substage II-1 and Ag-sulfosalts in substage II-2 suggest a decrease in sulfur fugacity (fS(2)). Both the decrease in fS(2) and cooling of the mineralizing fluids facilitate silver precipitation. The heterogeneous compositions of the freibergite and the Ag zonation in sphalerite (Sp-1) resulted from retrograde solid-state reactions that redistributed Ag through microscale exsolution. The delta S-34 values (+5.49 to +7.78 parts per thousand) of the sulfides and the low Zn/Cd ratios (107-195) of sphalerite indicate a felsic magma source for the ore-forming materials. Therefore, we concluded that the Wutuogou Ag-Pb-Zn deposit corresponds to a medium- to low-temperature magmatic-hydrothermal deposit associated with Late Triassic magmatism in the Eastern Kunlun Orogenic Belt (EKOB).

The helical undulator is in high demand in synchrotron radiation facilities for circular polarization generation. Owing to the higher field strength provided by the superconducting undulator compared to the conventional permanent-magnet undulator, greater research efforts should be directed toward this area. The helical superconducting undulator holds great potential in synchrotron radiation facilities, especially in low-energy storage rings that seek circularly polarized radiation with the highest possible radiation flux. Following the successful development of planar superconducting undulators, the Institute of High Energy Physics conducted research and development for the helical superconducting undulator. A 0.5-m-long Delta-type superconducting undulator prototype was developed and tested. Detailed information on the design, fabrication, and cryogenic testing of the prototype is presented and discussed.

Granitoids are the primary constituents of the continental crust; recognizing and quantifying the effects of crystal accumulation in evolved magmas is a challenging task. Here we present whole-rock chemical, Sr-Nd isotopic, zircon U-Pb geochronological, and Hf isotopic data as well as EPMA and in-situ LA-ICP-MS analyses of amphiboles from Qingshan granodiorite and mafic microgranular enclaves (MMEs) from the North Qilian Orogenic Belt (NQOB). The MMEs and granodiorite have identical crystallisation ages (ca. 434 Ma), the same mineral assemblage, but different mineral modal proportions as the MMEs comprise more amphibole. The MMEs and granodiorite have indistinguishable and depleted zircon Hf (epsilon Hf (t) values of 6.1-8.3, and 6.4-9.1, respectively) and whole-rock Sr-Nd isotopic compositions, i.e. (87Sr/86Sr)i values of 0.70514-0.70913 and 0.70207-0.70552, respectively; and epsilon Nd(t) values of 0.27-2.23 and 0.21-2.39, respectively. The occurrence of idiomorphic amphibole grains, low MREEs and HREEs concentration, low Mg# values of equilibrium melts (AEMs), and decreasing Zr/Hf ratios indicate that Qingshan MMEs represent cumulates formed at a thermal boundary layer between the ascending conduits and the wall rocks. The Qingshan granodiorite was formed by partial melting of subducted oceanic crust with crustal materials during southward subduction of the North Qilian Ocean, followed by further amphibole-dominated fractionation by compaction without crystal deformation. We propose a model of southward subduction with the back-arc basin for the tectonic evolution of the western NQOB. Both the subduction- and collision-related granitoids of the NQOB have played a vital role in continental crust growth.