Subduction zones are crucial for regulating volatile exchange between the Earth's surface and interior. Specifically, volatile migration in the mantle wedge controls arc magma genesis and outfluxes. However, the poorly constrained capacity of the forearc mantle wedge to retain volatiles limits our ability to quantify global volatile cycling. This study focuses on serpentinites from the Heimulin area and investigates volatile behavior during shallow forearc serpentinization and subsequent recrystallization within the forearc mantle wedge. This is achieved through analyses of carbon and sulfur contents and isotopic compositions, combined with thermodynamic modeling. The carbon content and isotopic composition of the two sample types, which represent different degrees of serpentinization, show no significant difference. However, carbon enrichment and magnesite formation were observed in serpentinites containing ribbon-textured lizardite. Sulfur systematics suggest that slab-derived dehydrating fluids can introduce sulfur into the mantle wedge, where it can be effectively retained in serpentinite systems as pyrite under low water-rock ratios. These findings imply that forearc serpentinites may play a role in volatile transport and serve as reservoirs for carbon and sulfur, which may have implications for understanding volatile cycling in subduction zones.

The redistribution and oxidation of iron during serpentinization are critical for quantifying hydrogen production and redox fluxes in subduction zones. This study investigates serpentinites from the Heimulin area in the Qinling Orogen, central China, to constrain their evolution and identify the factors controlling Fe3+ incorporation into serpentine minerals and associated H2 generation. Whole-rock geochemical compositions and the chemistry of relict primitive Cr-spinel domains indicate that the protoliths were highly refractory forearc mantle peridotites. The enrichment patterns of fluid-mobile elements closely resemble those of forearc serpentinites, such as those from the Mariana forearc, suggesting the protolith was hydrated by slab-derived fluids in a shallow forearc setting. Mineralogical analyses identify four distinct types of lizardite, reflecting the sequence of serpentinization. Initial low-temperature serpentinization produced some Type-1 lizardite grains, in which Fe3+ was incorporated into the crystal lattice through dioctahedral substitution. When silica activity became sufficiently low, hydration of olivine produced Fe-rich brucite and additional Type-1 lizardite and some Type-2 lizardite grains that lack detectable Fe3+ substitution. As serpentinization progressed, local increases in silica activity, driven by mineralogical heterogeneity (e.g., orthopyroxene dissolution) or influx of SiO2-rich external fluids, induced the breakdown of Fe-rich brucite and promoted the formation of fine-grained magnetite together with additional Type-2 lizardite grains, in which Fe3+ was incorporated into the crystal lattice through cronstedtite substitution. Since the major episode of Fe oxidation occurs during the interaction between brucite and SiO2-rich fluids, and given the widespread occurrence of cronstedtite-type substitution in natural lizardite, the formation of Fe3+-serpentine with tetrahedral Fe3+ may therefore mark the principal stage of hydrogen generation. During subsequent recrystallization, reduced Fe3+ availability favored the transformation of lizardite to chrysotile. Simultaneously, silica-poor conditions promoted the preservation of brucite, which aggregated and recrystallized to form economically significant fibrous brucite deposits. The chemical compositions of lizardite in recrystallized serpentinites, together with variations in bulk-rock Fe3+/ΣFe ratios, further indicate that Fe3+ was redistributed during recrystallization. Overall, low-temperature serpentinization of refractory peridotites under SiO2-poor conditions, followed by recrystallization, creates favorable conditions for the formation of economically valuable chrysotile asbestos and fibrous brucite deposits.

Subduction zone is a unique channel on Earth regulating the long-term exchange of nitrogen (N) between Earth's surface and its interior. Increasing evidence has implied that the serpentinized forearc mantle wedge could be an overlooked sink for slab-derived N that potentially regulates the subduction-zone N cycle but has been poorly studied so far. Here we report the N concentrations and isotope compositions of a suite of lizardite serpentinites, lizardite-antigorite serpentinites, and antigorite serpentinites from the Mianlue tectonic melange in the Qinling Orogen. These samples cover the serpentine phase variations in serpentinized forearc mantle wedge overlain the subducting slab down to a depth of similar to 30 km, and thus provide a unique opportunity to unravel the role of the forearc mantle wedge serpentinization in subduction-zone N cycle. The results show that these serpentinites have significantly higher N concentrations (19.7 to 37.4 ppm) than seafloor serpentinites (3 to 19 ppm), indicating more efficient N uptake during fluid-rock interactions inside the subduction zone. The combined N concentrations and delta N-15 values suggest that the N added into these serpentinites was mainly mobilized directly from subducted sediments (with a delta N-15 range of -1 parts per thousand to +10 parts per thousand) with a small portion possibly derived from abiotic N-2 reduction (with delta N-15 value down to -13 %o). Despite the prograde phase change from lizardite to antigorite, these serpentinites display comparable N concentrations and no sign of metamorphic N devolatilization. The Mianlue serpentinites also show comparable N concentrations with the forearc serpentinized peridotites (dominated by lizardite/chrysotile) from the Mariana mud volcanoes and forearc antigorite serpentinites from the Tso Morari ultrahigh pressure unit exhumed from >100 km depth. These observations suggest strong N retention in the mantle wedge serpentinites during prograde metamorphism. If such N enrichment is typical in the serpentinized forearc mantle wedge, it means that up to 1.4(+/- 0.6) x 10(9) mol center dot yr(-1) slab N can be incorporated into global forearc mantle wedge. Although this amount only accounts for similar to 4 % of the sedimentary N input flux, it may account for a significant portion of the small amount of slab N released during early subduction. This implies that forearc serpentinites may play an unprecedentedly recognized role in subduction-zone N cycle. This role may be even more important in hot subduction zones. If N loss from Catalina Schist (i.e., similar to 70 % N loss in the forearc) is employed to represent hot subduction zones, our estimation shows that up to similar to 25 % of the lost sedimentary N could be re-fixed in forearc serpentinites. The strong N retention in forearc serpentinites as well as in the minerals after antigorite breakdown (e.g., chlorite, amphibole, clinopyroxene and garnet) facilitates deep recycling of slab N (even in the early Earth) if the serpentinized mantle wedge are dragged down by mantle flow. Alternatively, if the serpentinized mantle wedge is imbricated as a portion of the lithospheric mantle, it will enhance the fertilization (and thus heterogeneity) of the lithospheric mantle.

In the realm of control systems, model predictive control (MPC) has exhibited remarkable potential; however, its reliance on accurate models and substantial computational resources has hindered its broader application, especially within real-time nonlinear systems. This study presents an innovative control framework to enhance the practical viability of the MPC. The developed safe data-driven predictive control aims to eliminate the requirement for precise models and alleviate computational burdens in the nonlinear MPC (NMPC). This is achieved by learning both the system dynamics and the control policy, enabling efficient data-driven predictive control while ensuring system safety. The methodology involves a spatial temporal filter (STF)-based concurrent learning for system identification, a robust control barrier function (RCBF) to ensure the system safety amid model uncertainties, and a RCBF-based NMPC policy approximation. An online policy correction mechanism is also introduced to counteract performance degradation caused by the existing model uncertainties. Demonstrated through simulations on two applications, the proposed approach offers comparable performance to existing benchmarks with significantly reduced computational costs.

Subduction zones play a critical role in carbon exchange between Earth's surface and interior. While devolatilization of forearc serpentinites has been proposed as a contributor to arc magma genesis, its role in subductionzone carbon (C) and magnesium (Mg) cycling, as well as its influence on the Mg isotopic variability in global arc lavas, remains poorly constrained. This study investigates Mg isotope fractionation during interactions between forearc peridotites and CO2-rich fluids in the Mianlue tectonic melange, focusing on carbonate-bearing serpentinites from the Jianchaling and Liangyazi regions. Five Jianchaling lizardite-only serpentinites exhibit a narrow range of S26Mg values (-0.28 f 0.02 %o to -0.13 f 0.02 %o), similar to those of four Jianchaling antigoritelizardite serpentinites (-0.27 f 0.03 %o to -0.17 f 0.01 %o). In contrast, seven Liangyazi antigorite-only serpentinites display a broader S26Mg range (-0.27 f 0.03 %o to -0.01 f 0.02 %o). Magnesium isotope compositions of mineral separates reveal temperature-dependent inter-mineral Mg isotope fractionations between carbonate and co-precipitated serpentine minerals. Thermodynamic modeling and mass balance calculations indicate minimal Mg loss from peridotites to fluids during their interaction with CO2-rich fluids. Instead, subsequent fluid infiltration and carbonate dissolution are responsible for the observed Mg isotopic variations. The concurrent precipitation of isotopically heavy silicate minerals and light carbonates in the forearc provides a plausible explanation for the elevated S26Mg values observed in some arc lavas. In subduction zones where the forearc slab-top temperatures can exceed the stability limit of antigorite (600 - 700 degrees C), significant forearc decarbonation produces CO2-rich fluids that interact with forearc peridotites at the bottom of the mantle wedge, forming abundant isotopically heavy silicate minerals. The subsequent breakdown of these silicates and limited release of slab-derived carbonates at subarc depths may be responsible for the high S26Mg values and low CO2 outfluxes characteristic of these subduction zones. In contrast, subduction zones with cooler forearc slab-top temperatures, where subarc slab-top temperatures approach the stability limit of antigorite, experience less significant forearc decarbonation. In such settings, limited formation of isotopically heavy silicate phases and enhanced release of slab carbonates at subarc depths due to infiltrations of slab-derived fluids can potentially result in arc magmas with S26Mg values close to or slightly below the normal mantle. These findings underscore the critical role of fluid-rock interactions in the forearc region in regulating deep carbon cycling and shaping the Mg isotopic signatures of arc magmas.

Deciphering the slab melt contribution to arc igneous rocks in orogenic belts is of great importance for unraveling the fate of subducted slabs, adakite petrogenesis and geochemical recycling process. The fact of subducted slabs, particularly how different sections of the oceanic crust including its overlying sediment react during slab melting, remains poorly understood. Here we present a detailed study of the Leigongshan (LGS) tonalite pluton in the eastern section of the North Qilian suture zone (NQSZ). The tonalites are geochemically similar to low-Mg adakitic rocks characterized by high Sr/Y and (La/Yb)N ratios with low MgO, Cr, and Ni concentrations, indicating limited/no mantle interaction. They exhibit moderately radiogenic Sr, Nd, and Pb isotope compositions with initial 87Sr/86Sr ratio of 0.706216-0.708267, & epsilon;Nd(t) value of -0.7 to -2.1 and (206Pb/204Pb)t of 18.52-18.90, most likely a mixed melt derived from the mafic oceanic crust plus ca. 10-25% overlying sediments. Morphology, internal structure, and U-Pb dating of zircon crystals indicate a common preservation of old cores aged at ca. 470-2733 Ma. The sharp truncation of core zoning and embayed boundaries with the rims further indicate that the cores are probably clastic, abraded materials inherited from a (meta)sedimentary precursor from which the tonalitic magma was derived. The younger mean ages of ca. 453-450 Ma are interpreted as the emplacement age of the pluton. They have & epsilon;Hf (t) values of +0.5-7.0 and & delta;18OZrc values of 4.9%o to 8.7%o, which somewhat deviate from those of the parent mafic oceanic crust, indicating the involvement of subducted sediments as well. The LGS adakitic tonalite represents mixed melts of the subducted slab including the overlying sediment that accounts for the enriched Sr-Nd-Pb isotope compositions. Future detailed research on the zircons of adakite/adakitic rocks would provide new important clues on their petrogenesis.

Despite great successes, model predictive control (MPC) relies on an accurate dynamical model and requires high onboard computational power, impeding its wider adoption in engineering systems, especially for nonlinear real-time systems with limited computation power. These shortcomings of MPC motivate this work to make such a control framework more practically viable for real-world applications. Specifically, to remove the required accurate dynamical model and reduce the computational cost for nonlinear MPC (NMPC), this paper develops a unified online data-driven predictive control pipeline to efficiently control a system with guaranteed safety without incurring large computational complexity. The new aspect of this idea is learning not only the real system but also the control policy, which results in a reasonable computational cost for the data-driven predictive controllers. More specifically, we first develop a spatial temporal filter (STF)-based concurrent learning scheme to systematically identify system dynamics for general nonlinear systems. We then develop a robust control barrier function (RCBF) for safety guarantees in the presence of model uncertainties and learn the RCBF-based NMPC policy. Furthermore, to mitigate the performance degradation due to the existing model uncertainties, we propose an online policy correction scheme through perturbation analysis and design of an ancillary feedback controller. Finally, extensive simulations on two applications, cart-inverted pendulum and automotive powertrain control, are performed to demonstrate the efficacy of the proposed framework, which shows comparable performance with much lower computational cost in comparison with several benchmark algorithms.

The petrogenesis of aluminous A-type granites is a contentious subject. Here, we focused on the North Kudi pluton in the Western Kunlun orogen to investigate the origin and magmatic processes responsible for generating A-type granites. Samples from the North Kudi pluton are metaluminous to weakly peraluminous. K-feldspar granite samples are characterized by high alkali and Cl contents, high HFSE concentrations and FeO/MgO, low F content, negative Ba, Sr, P, Eu, and Ti anomalies, and high magma temperature (>903 °C), showing affinity to aluminous A-type granites. However, their 10,000 × Ga/Al ratios (1.86–3.18) are relatively lower than typical A-type granites. Quartz-monzonite displays similar Sr–Nd isotopic compositions and Ga/Al ratios with the K-feldspar granite but less pronounced negative Sr, P, and Ti anomalies and no discernable negative Ba and Eu anomalies. Fractional crystallization of alkali-rich, Cl-rich, and F-poor magmas can generate some typical geochemical characteristics of A-type granites (e.g., negative Ba, Sr, P, and Eu anomalies) but has little influence on Ga/Al ratios. The enriched Sr–Nd isotopic compositions, high Cl and alkali contents, arc-like geochemical features, and the involvement of slab-derived components, as indicated by high zircon Ce4+/Ce3+ (up to 503), suggest that the North Kudi pluton was possibly derived from partial melting of the metasomatized lithospheric mantle in the time of asthenosphere upwelling during the post-collisional stage. The emplacement of the North Kudi pluton thus indicates the onset of the post-orogenic stage in the Western Kunlun orogen.

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Increasing evidence shows that the man-tle contributes (directly or indirectly) to Sn-bearing granites worldwide. However, the specific role of mantle in the formation of tin granites and related mineralization remains poorly understood. In the world-class Dachang district, South China, tin mineralization is related to the Longxiang-gai equigranular/porphyritic biotite granites and tin orebodies are cut by granite por-phyry dykes hosting mafic microgranular enclaves (MMEs). A combination of zircon U-Pb dating and Hf-O isotopes, mineral chemistry, and whole-rock elemental and Sr-Nd isotopic compositions-for granitic rocks and MMEs, is employed to constrain the petrogenesis and to unravel the link between tin fertility and mantle upwell-ing. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon U-Pb dating indicates that the biotite granites were emplaced at ca. 93 Ma, and the granite porphyry dykes and MMEs were formed at ca. 86 Ma. The biotite granites are silica-and alkali-enriched with A/CNK ratios of 1.04-1.36, and exhibit elevated con-centrations of Li, F, P, Rb, Cs, Ta, Sn, W, and U, showing affinities with highly fraction-ated S-type granites. Whole-rock geochemi-cal and Nd isotopic (epsilon(Nd)(t) = -10.0 to -7.8) data, and in situ zircon Hf-O (epsilon(Hf)(t) = -9.9 to -3.9, delta O-18 = 6.2-8.9%0) isotopes indicate that the biotite granites were formed by partial melting of metasedimentary rocks at relatively high temperatures (>= 782 degrees C), possibly with minor input of mantle mate-rial. Likewise, the post-ore granite porphyry dykes have similar chemical and mineral-ogical characteristics as fractionated S-type granites. Zircon Hf-O isotopes (epsilon(Hf)(t) = -9.0 to -4.9, delta O-18 = 6.5-8.2 parts per thousand) and whole-rock geochemical data suggest they were derived from a similar source as the biotite granites, whereas elevated epsilon(Nd)(t) values of -5.0 to -3.3 for granite porphyry dykes relative to biotite granites reveal an increasing mantle input. Distinct epsilon(Nd)(t) (-0.4 and -0.3) and zircon Hf-O (epsilon Hf(t) = 1.5-5.0, delta O-18 = 6.5-7.2 parts per thousand) iso-topes of the MMEs, suggest that the mafic melt could be sourced from the astheno-spheric mantle, contaminated by subconti-nental lithospheric mantle/continental crust during magma ascent, and hybridized by fel -sic melt at emplacement-level. The magmatic sequence in the Dachang district is indica-tive of an extensional tectonic setting where mantle-derived magmas are predicted to mi-grate to shallower crustal levels as the crust progressively becomes thinner and hotter. High-temperature partial melting of mature metasedimentary crust triggered by heat in-put from the upwelled mantle, may contrib-ute to biotite breakdown, which is important for concentrating tin in melts. Fractional crystallization of initially Sn-rich felsic melts under reduced conditions makes further tin enrichment and produces Sn-bearing gran-ites (the Longxianggai pluton). Prolonged mantle upwelling results in distinct magma mixing and the formation of granite por-phyry dykes and MMEs. These dykes are highly fractionated with elevated Sn and W contents, which show great potential to form hydrothermal Sn-W mineralization.

Model predictive control (MPC) is a state-of-the-art control method that can explicitly tackle system constraints. However, its high computational cost still remains an open challenge for embedded systems. To achieve satisfactory performance with manageable computational complexity, a spatial temporal filter (STF)-based data-driven predictive control framework is developed to systematically identify system dynamics and subsequently learn the MPC policy using STF-based function approximations. Specifically, an online nonlinear system identification method that satisfies persistence of excitation (PE) is developed by using a discrete-time concurrent learning technique. An STF-based function approximation is then employed to learn the nonlinear MPC (NMPC) policy based on the identified model. Furthermore, a discrete-time robust control barrier function (RCBF) is introduced to guarantee system safety in the presence of additive disturbances and system identification errors. Finally, simulations on the cart inverted pendulum are performed to demonstrate the efficacy of the proposed control synthesis.

This paper presents an efficient stochastic model predictive control (SMPC) framework for quasi-linear parameter varying (qLPV) systems. The framework applies to general nonlinear systems that are driven by stochastic additive disturbances and subject to chance constraints. The qLPV form is featured by a composition of a set of linear time-invariant (LTI) models with state-/control-dependent scheduling variables, which can be obtained by the spatial-temporal filtering-based system identification approach developed in our earlier work. The overall framework can then be transformed into a tube-based MPC optimization problem which can be efficiently handled by a series of quadratic programing (QP) problems. A case study on automotive engine control is presented as a pilot demonstration of the proposed qLPV-SMPC where we show its advantage over the zone-based MPC, much greater computational efficiency than nonlinear MPC (NMPC) and less conservativeness of the proposed method as compared to its robust MPC (RMPC) counterpart.

The world-class Gejiu Sn-polymetallic district (southwest China), with ca. 3.27 Mt Sn metal, is a magmatic-hydrothermal deposit associated with the Late Cretaceous biotite granites; however, the magmatic and hydrothermal processes involved in its formation remain poorly understood. Tourmaline is a ubiquitous phase in the Gejiu district, and here we employ in-situ major, trace element, and boron isotope compositions of tourmaline to investigate the source and evolution of the mineralizing fluid, and late-magmatic and hydrothermal processes related to ore formation. Based on petrographic observations, four types of tourmaline are identified: i) latemagmatic tourmaline (Tur I) disseminated in the biotite granites, ii) hydrothermal tourmaline (Tur II) from quartz veins with fracture-filling structure in the biotite granites, iii) hydrothermal tourmaline (Tur IIIa-1, IIIa-2 and Tur IIIb-1, IIIb-2) from fluorite-quartz veins with typical replacement texture against the greisenized granites, among which Tur IIIb-2 is directly related to cassiterite formation, and iv) hydrothermal tourmaline (Tur IV) from sulfide-calcite veins hosted by proximal skarn. Tourmaline (Tur Ito Tur III) from the granites belongs mostly to the alkali group and schorl-dravite solid-solution series, with Fe/(Fe + Mg) ranging from 0.83-1.00 for Tur I, 0.68-1.00 for Tur II, and 0.19-1.00 for Tur III, respectively. By contrast, Tur IV belongs mostly to the vacancy group and has foitite-Mg-foitite composition, with Fe/(Fe + Mg) of 0.10-1.00. Large variations of Fe/(Fe + Mg) as well as Na/(Na + Ca) in hydrothermal tourmaline (Tur II to Tur IV), are related to different degrees of interaction between B-rich fluids with host rocks (solidified granite or carbonate). Most trace elements in tourmaline do not correlate with Fe/(Fe + Mg) and Na/(Na + Ca) ratios, implying the trace element compositions are predominantly controlled by melt/fluid compositions and local fluid-rock reactions. Relative to late-magmatic Tur I, hydrothermal tourmaline (Tur II to Tur IV) is enriched in Sr and depleted in Nb, Ta, and (REE + Y), whereas their Li, Be, Sc, V, and Sn concentrations are largely overlapped. The delta B-11 values in different types of tourmaline fall in a narrow range from -17.8 to -13.7 parts per thousand, in favor of B-rich fluids episodically exsolved from the granitic melt. Tin enrichment in both late-magmatic and hydrothermal tourmaline grains, especially in those (Tur IIIb) from Sn-mineralized veins, is related to magmatic differentiation and late-stage fluid exsolution. Among all types of tourmaline, Tur IIIb-2 coexisting with cassiterite has elevated Fe3+/(Fe3+ + Fe2+) ratios (mean 0.23), indicating that cassiterite precipitated under relatively oxidized conditions. The distinct chemical (i.e. high Mg, Ti, V, Sc, Sr, and Sn contents) and B-isotope compositions (slightly lower delta B-11 values of -17.8 to -15.0 parts per thousand) in syn-ore Tur IIIb-2, combined with the co-occurrence of liquid- and vapor-rich inclusions triggered by fluid boiling in Sn-mineralized veins, suggest that fluid boiling and acid-consuming reaction could be major processes triggering cassiterite precipitation in the quartz vein and greisen. Overall, the chemical and B-isotope signatures of tourmaline are ideal tracers to unravel the magmatic-hydrothermal evolution in the Gejiu Sn-polymetallic district, which could be further employed as a potential prospecting guide for Sn-W deposits.

The copper isotopic compositions of 12 copper-rich minerals (including native copper, sulfides, carbonates, oxides, and copper chloride) have been determined using a 206 nm ultraviolet femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry (UV-fs-LA-MC-ICP-MS). A pure copper wire NWU-Cu-B and a natural chalcopyrite TC1725 were used as bracketing standards for calibration. Reliable and precise (2SD<0.07‰) δ 65 Cu values can be obtained using matrix-matched standards under dry plasma condition and calibrated by the standard-sample bracketing method (SSB). However, the δ 65 Cu values calibrated by non-matrix-matched standards were seriously affected by matrix effect, with a deviation of up to 1.42‰. Therefore, matrix-matched standards are necessary for reliable in situ Cu isotope ratio measurement. Although the analytical precision (2SD) is slightly improved, the use of Ga as an internal standard combined with the SSB correction does not reduce the deviation caused by the matrix effect. However, the matrix effect can be significantly suppressed by adding 8.6 µL min −1 water into the carrier gas. The matrix-induced δ 65 Cu deviation of the TC1725 calibrated against the pure copper NWU-Cu-B was reduced from 0.99‰ in dry plasma mode to 0.03‰ in wet plasma mode and achieved a long-term reproducibility of 0.10‰ (2SD). For the Cu isotopic compositions of 12 natural copper-rich minerals determined under wet plasma mode, the deviation of δ 65 Cu was less than 0.13‰ if the mineral is homogeneous. These results indicate that the non-matrix-matched standardization can be achieved by fs-LA-MC-ICP-MS under wet plasma condition, whether using chalcopyrite or pure copper as the external bracketing standards.

y Large-scale Late Cretaceous magmatic intrusions have been recognized in the southern Gangdese magmatic belt, although their genesis and mineralization potential remain controversial. In this paper, we present new zircon UPb ages, whole-rock compositions, and major- and trace element compositions of zircon and apatite from the Chemen granodioritic intrusion. When integrated with compiled literature data for other Late Cretaceous igneous rocks in the southern Gangdese belt, our new dataset provides new insight into their genesis and mineralization potential. The Chemen intrusion obtains a zircon U-Pb age of similar to 91 Ma, similar to the age of Late Cretaceous magmatic intrusions across the entire southern Gangdese belt. Both the Chemen and other Late Cretaceous intrusions have geochemical characteristics that resemble those of adakites. When considered alongside the coeval formation of mafic intrusive rocks, high-temperature adakitic charnockites, and thickening of continental crust in the region, ridge subduction is considered most likely to be responsible for this 'flare-up' event. The Ce4+/Ce3+ ratios in zircon and SO3 contents of apatite from the Chemen granodiorites both indicate a high oxygen fugacity during crystallization. Further, trace elements in Chemen apatite indicate that the Chemen intrusion has a great mineralization potential; however, no mineralization has been found in some of the Late Cretaceous intrusions in the southern Gangdese belt. Compiled data show that these barren Late Cretaceous intrusions generally formed from magmas with a low oxygen fugacity. Thus, we speculate that the low oxygen fugacity of some Late Cretaceous intrusions may limit the extent to which mineralization may occur.

利用Iris网站中约55万条地震数据对日-月-地、日-地、月-地空间位置关系周期性变化对全球地震时间的影响进行统计分析,并对统计结果与引潮力作用之间的关联进行研究。统计分析结果表明:1)考虑日-月-地空间关系,在不同的震级、震源深度下,全球地震频率在日-月-地三者成90°或180°时均有较为明显的提升; 2)考虑日-地空间关系,全球地震频率在地球运行于惊蛰-谷雨对应的公转轨道时有着明显的提升,当地球运行于春分-清明对应的公转轨道时,全球地震频率在农历初七的提升非常明显,相对于自然概率提升47.6%; 3)考虑月-地空间关系,发震位置经度距离月球星下点经度差为180°时易触发地震; 4)研究表明部分地震发震受到引潮力调制,特定周期下引潮力的最值区间对应于全球地震频率升高的时间区间。

Accretionary orogens are the primary sites for continental growth, but the rate and amount of crust generation throughout its evolution are poorly constrained. In this contribution, our new results about the genesis of two intermediate-felsic plutons are combined with a compiled granitoid dataset to evaluate the amount and rate of crustal growth throughout the evolution of the Western Kunlun orogen, which is a typical accretionary orogen associated with the consumption of the Proto-Tethys during the early Paleozoic. The ca.446 Ma Sanshili pluton was formed through interactions between metasomatized mantle wedge-derived oxidized magmas and the lower arc crust, as indicated by high whole-rock Mg#, high Ce4+/Ce3+ ratios (308–861) of ca.446 Ma zircons, and the existence of inherited zircons with ages of 546–472 Ma. The Yirba dioritic to granodioritic pluton was emplaced at 474 ± 3 Ma. Samples from the Yirba pluton are characterized by high K2O content, higher Mg# (40–49) than pure crustal melts, slightly higher Y + Nb concentrations, and high Th/Nb ratios, and slightly enriched to depleted Hf–Nd isotopes. Combined with the presence of the 502–531 Ma inherited zircons, the Yirba pluton is suggested to from through differentiation of the metasomatized lithospheric mantle derived-magmas beneath the juvenile intra-oceanic arc in combination with crustal reworking during regional extensions. The Yirba pluton, together with contemporary A1-type granites, thus marks an extension event at ca. 475 Ma in the Western Kunlun orogen. The compiled dataset reveals three magmatic flare-ups at 530–500 Ma, 480–470 Ma, and 445–430 Ma, corresponding to two slab rollback events and the slab break-off after the final closure of the Proto-Tethys. The three episodes of more intensive magmatism are associated with more radiogenic Hf–Nd isotopes and increased Nb/La and Nb/Y ratios, indicating more contributions from intraplate-like sources during lithospheric extensions. Meanwhile, element ratios (La/Yb, Sm/Yb, and Sr/Y) that are sensitive to crustal thickness are also elevated. These phenomena are consistent with rapid juvenile crust generation during extensional stages of accretionary orogens. Our study has also shown that the rate of new crust production is quite uniform for different extensional events. The crustal generation rate during slab break-off is much higher than that during slab rollback, although the proportions of juvenile inputs in granitoids formed during slab rollback are relatively higher. This may reflect extra inputs from partial melting of oceanic slabs and subducting sediments like those in continental collision zones and/or rapid asthenospheric upwelling coupled with enhanced crust reworking during slab break-off.

Granitoids in active continental margins are probes of sub-arc magmatic processes and are crucial for the understanding of crust–mantle interaction during subduction. Here we report data for the middle to late Cambrian Tuole (TL) and Dabaishitou (DBST) granitic plutons in the western segment of the North Qilian suture zone (NQSZ). The TL-DBST plutons comprise monzonite, alkali-feldspar granite, gabbroic diorite, monzonitic porphyry and biotite monzogranite. Zircon U‒Pb ages reveal that these granitoids crystallized at ca. 509‒492 Ma, consistent with the early subduction of the North Qilian Ocean. Mineralogical, petrological, and geochemical features indicate that the TL monzonite and gabbroic diorite are both high-K calc-alkaline I-type granitoids but the latter is Nb-enriched; the TL alkali-feldspar granites and DBST granitoids belong to aluminous A-type and transitional I- and A-type granites, respectively. The I- and aluminous A-type granites show similar and comparable isotopic compositions, e.g., εHf(t) values of ‒5.6 to +2.7 versus ‒2.4 to +3.5, but different melting conditions, e.g., high temperature and low oxygen fugacity for aluminous A-type granites as indicated by zircon trace elements. Geochemical and isotope data suggest that all these granitoids were mainly derived from the sub-arc mantle metasomatized by slab-derived fluids/asthenospheric mantle-derived melts/both prior to melting with minor input of LCC-derived melts (ca. 10–20%). The HFSE enrichment feature was inherited by granites and further enhanced by protracted crystal fractionation at low oxygen fugacity conditions to produce the TL aluminous A1-type granites but weakened by fractionation at relatively high oxygen fugacity conditions to produce the DBST I-A-transitional-type granite. Partial melting of the sub-arc lithospheric mantle was induced by upwelling of the asthenospheric mantle and their interactions in response to slab rollback during subduction initiation (ca. 509–506 Ma), and by addition of slab-derived fluids again as subduction proceeded (ca. 493–492 Ma).

Hydrous minerals in the hybridized zone at the slab-mantle interface play a critical role in retaining and transporting fluid mobile elements in subduction zones. The observed high B and As concentrations and high delta(11) B values in arc magmas were previously thought to have been resulted from the mechanical transport of forearc serpentinites down to subarc depths by mantle corner flows or through subduction channels because B, As, and Sb are mostly released during early stages of subduction. This study provides new insights into the recycling of B, As, and Sb in subduction zones via an in-situ study on a set of carbonate-bearing serpentinite samples from the Mianlue me ' lange complex in the Qinling Orogen. Petrological observations and bulk-rock Sr-Pb isotopes reveal that the Jianchaling serpentinites were formed by interactions between forearc peridotites and sediment-derived fluids at a shallow depth in the subduction channel. Some Jianchaling serpentinites experienced the lizardite to antigorite transition at 300-400 degrees C with infiltrations of CO2-rich fluids. In contrast, the Liangyazi antigorite serpentinites were produced at a greater depth. Antigorite grains in the Jianchaling serpentinites have lower Fe-apfu than those in the Liangyazi serpentinites and most antigorite with geochemical data in the literature. Meanwhile, B, As, and Sb concentrations of Fe-poor antigorite from the Jianchaling serpentines (385-653 ppm B, 198-334 ppm As, and 6.24-8.01 ppm Sb) are not only higher than those of the Fe-rich antigorite from the Liangyazi serpentinites but also 2-3.5 times higher than those of the surrounding lizardite. The lower modal percentage of spinel and ferritchromite in antigorite veinlets, together with the lower bulk-rock FeO content of antigorite-lizardite serpentinites than that of lizardite serpentinites from the Jianchaling region, indicates that some FeO might be lost during the lizardite to antigorite transition. The presence of carbonate minerals in the antigorite veinlets and the remarkably high B, As, and Sb concentrations in the Jianchaling antigorite indicate that the penetrating fluids during the lizardite to antigorite transition are most likely derived from sediment and metabasite decarbonations at <350 degrees C. Infiltrations of CO2-rich fluids at the slab-mantle interface could buffer a relatively low pH to significantly enhance the mobility of Fe2+, which is produced by reduction of the cronstedtite component in lizardite or Fe3+ in magnetite during the lizardite to antigorite transition, and facilitate the formation of Fe-poor antigorite at the slab-mantle interface. The oxygen fugacity in such a CO2-rich water-rock system is also high enough for the occurrence of As5+ in the surrounding fluids. Therefore, once Fe-IV(3+) is lost from the serpentine lattice structure during the lizardite to antigorite transition, B3+, As5+, and Sb5+ in the surrounding fluids can occupy the tetrahedral sites in the newly formed Fe-poor antigorite. The formation of Fe-poor antigorite at the slab-mantle interface is therefore made available to transport shallow slab-derived B, As, and Sb to a greater depth, where destabilization of antigorite at 600-700 degrees C liberates these elements into the arc magma source. (C) 2021 Elsevier Ltd. All rights reserved.

U-Pb dating geochronology by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been widely applied in geological research as a low-cost and high-efficient in situ micro-analytical tool. Currently, quantitative analysis using LA-ICP-MS requires matrix-matched external standards to correct for elemental fractionation. Since natural standard minerals are often limited in supply or not available, non-matrix-matched calibration methods using synthetic glasses as the calibration standards have attracted attention. In addition, access to a higher spatial resolution capability of <10 mu m spot size has been driven by the interest in studying the temporal records of fine mineral grains or rims compared to the conventional >20 mu m laser ablation spots used in most LA-ICP-MS laboratories for zircon dating. In this study, we present an LA-ICP-MS analytical procedure for non-matrix-matched U-Pb zircon dating using a 9 mu m laser ablation spot size and a synthetic silicate glass (NIST SRM 610) as the external standard. The elemental fractionation between the NIST SRM 610 glass and zircons can be significantly reduced by using a low laser frequency (2 Hz) and energy density (3 J/cm(2)). To minimize the matrix effect on matrix-mismatched calibration between samples and standards, the effect of adding a small amount of water vapor or hydrogen into the carrier gas was investigated. A small amount (about 1.9 mu L/min) of water vapor added into the sample cell can reduce the Pb/U ratios of the NIST SRM 610 up to 14% during a 40 s ablation time at a small spot size. However, by adding water vapor after the sample cell can achieve an accuracy and precision of better than 2.3% for the weighted average Pb-206/U-238 ages using a 9 mu m spot size. In addition, the laser-ablated crater depth needs to be less than 4.3 mu m to control the down-hole fractionation during laser ablation.