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Plenty of gold deposits related to Late Mesozoic craton destruction are widely distributed in eastern North China Craton. However, significant differences in research degrees, ore-forming characteristics, and proven reserves exist among different regions in the North China Craton. The Liaodong Peninsula has similar regional geological characteristics to those of the Jiaodong Peninsula, with both experiencing craton destruction during Late Mesozoic, but the two areas have substantial differences in terms of gold mineralization and the proven gold resources. Based on regional geology, Mesozoic magmatic-tectonic evolution and ore geology, combined with integrated geophysical exploration and big data AI resource prediction, in this paper, we propose that the ore-forming materials of Late Mesozoic gold deposits in Liaodong were mainly originated from mantle-derived melts and/or fluids induced by craton destruction. The gold deposits were primarily controlled by NE-NNE-trending faults, mainly classified as fracture-controlled altered rock-type and sulfide-bearing quartz vein-type. Moreover, our study predicts that the Yalu River fault zone and its related secondary faults, as well as the periphery and deeper parts of known goldfields, are the important regions for future gold resource exploration. The Yalu River metallogenic belt has an enormous potential for gold resources, and the Liaodong Peninsula has a potential to add thousands of tons of gold resources. [ABSTRACT FROM AUTHOR]

Precise and accurate Fe isotope data of thirteen silicate minerals, including olivine, garnet, amphibole and biotite are reported here using the non-matrix-matched BCR-2G reference glass for isotope ratio calibration combined with a Ni doping method for instrumental mass bias correction by LA-MC-ICP-MS under wet-plasma conditions. All the in situ Fe isotope data are consistent with the recommended Fe isotopic values determined by SN-MC-ICP-MS. These results indicate that in situ Fe isotopic determinations by LA-MC-ICP-MS under wet-plasma conditions are matrix-independent for a variety of silicate minerals, and BCR-2G glass is suitable as the reference material for microbeam Fe isotopic analysis for silicate minerals. However, for other microbeam Fe isotopic analysis, e.g., SIMS, finding matrix-matched standards for data quality assurance is also required. Multiple analyses on two international olivine standards (San Carlos and ALM) and four natural silicate minerals (YY09-04 olivine, YS-13 garnet, YS-31 amphibole and Moosilauke biotite) reveal homogeneous Fe isotopic compositions with the external reproducibility better than 0.20‰ for δ56Fe values (2SD). Thus, these silicate minerals are proposed as matrix-matched in-house standards for isotope ratio calibrations and data quality control during microbeam Fe isotopic analysis. YY11-12 olivine, YS-42 garnet, YS-37 amphibole and YS-20 biotite with the external reproducibility of 0.23‰, 0.28‰, 0.23‰ and 0.25‰ for δ56Fe values (2SD), respectively, are only suitable as in-house standards for data quality monitoring during microbeam Fe isotopic analysis. [ABSTRACT FROM AUTHOR]

Ancient orogens within the supercontinent like Columbia can remain stable evolution as long as the cratons. What kind of lithospheric mantle was beneath those orogens and how it evolved into a stable state are still enigmatic. The Trans‐North China orogen (TNCO) is one of the typical collisional orogens within the Columbia supercontinent and was formed at ca. 1.85 Ga. Our work reveals that a cluster of kimberlites intruded the orogenic belt at ca. 1.54 Ga. These rocks were originally generated under a thick lithosphere (>200 km). Their entrained olivine cores show a composition of overlapping olivines from refractory mantle peridotites. The results suggest a thick and refractory lithospheric mantle beneath the TNCO at ca. 1.54 Ga. Such craton‐like property may result from large volume melt extraction from the lithospheric mantle, possibly caused by the ca. 1.78 Ga large igneous event, which eventually induces the long‐term stability of the TNCO during the subsequent supercontinent cycle. [ABSTRACT FROM AUTHOR]

Nowadays, in situ Fe isotopic analysis is facing a dilemma that the conventional reference material of IRMM-014 for isotope ratio normalization is commercially unavailable and is unable to meet the needs of laboratories. In this study, the other Fe metal (IRMM-524A), instead of the nearly exhausted IRMM-014, has been systematically checked to be a potential reference material for the Fe isotopic analysis by femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry (fs LA-MC-ICP-MS). A total of 136 analyses on IRMM-524A were directly calibrated against IRMM-014 using fs LA-MC-ICP-MS during eight analytical sessions. The result shows that the IRMM-524A Fe metal is relatively homogeneous, with average values of 0.01 ± 0.13‰ and −0.02 ± 0.19‰ (2SD, n = 136) for δ56Fe and δ57Fe, respectively, which are identical to the published values obtained by solution nebulizer (SN)-MC-ICP-MS within analytical uncertainties. Fe isotopic compositions of two in-house standards (Balmat pyrite, PZH12-24 ilmenite) and four natural samples (NKAu01 pyrite, PZH12-16 ilmenite, PZH12-18 ilmenite, and Moosilauke ilmenite) measured by fs LA-MC-ICP-MS relative to IRMM-524A or IRMM-014 are identical within analytical uncertainties. In addition, five of the samples (Balmat pyrite, PZH12-24 ilmenite, NKAu01 pyrite, PZH12-16 ilmenite, and PZH12-18 ilmenite) have homogeneous Fe isotopic compositions and yield an external reproducibility of 0.12‰ to 0.16‰ for δ56Fe values for different sections within three years. Thus, the IRMM-524A Fe metal and other five samples can be used as reference material and secondary standards for quality assurance for non-matrix-matched Fe isotopic analysis of pyrite and ilmenite by fs LA-MC-ICP-MS. [ABSTRACT FROM AUTHOR]

High-quality Sr isotope data are critically dependent on the quality of reference materials that are used for instrumental calibration and data monitoring during LA-MC-ICP-MS analysis. A suite of natural plagioclase samples (BDL-1, BDL-2 and BDL-3) from the Badaling intrusive complex, Beijing were investigated here to test their suitability as a plagioclase Sr isotope reference material. Major and trace element analyses by EPMA and LA-ICP-MS showed that plagioclase crystals separated from two troctolites (BDL-1 and BDL-3) and one gabbro (BDL-2) were all characterized by extremely low Rb/Sr ratios (0.00012–0.00047), and low heavy rare earth elements (HREEs) and high Sr contents (2377–2836 μg g−1). A total of 200 LA-MC-ICP-MS analyses for plagioclases BDL-1, BDL-2 and BDL-3 showed consistent and homogeneous Sr isotopic compositions with an average 87Sr/86Sr ratio of 0.70535 ± 0.00007 (2SD), which was in good agreement with solution-based data determined by TIMS or SN-MC-ICP-MS (0.70533 ± 0.00004; 2SD, n = 12), thus suggesting that BDL plagioclase can be used as a potential reference material for microbeam Sr isotopic analysis. Compared to the other available plagioclase Sr isotopic reference materials, the large quantities, long-term availability, high Sr content and extremely low isobaric interference (Rb, Er and Yb) of BDL plagioclase make it especially suitable for instrumental calibration and to adjust for inter-laboratory bias of the measured 87Sr/86Sr ratios. [ABSTRACT FROM AUTHOR]

The sub-continental lithosphere mantle (SCLM) contains considerable amounts of carbon and is responsible for significant CO 2 emissions via magmatism during major heating and rifting events. However, the role of SCLM in Earth's carbon cycle during other geological processes, such as decratonization, a process of major removal and replacement of cratonic SCLM, remains poorly understood. The North China Craton is an archetype of Archean craton having been decratonized during the Mesozoic with extensive magmatism developed. Here we show that the primary melt of Early Cretaceous Yixian basalts contained abundant CO 2 (0.6 wt%), through investigating melt inclusions trapped in olivine crystals. The melt inclusions are alkalic and chemically distinct from their sub-alkalic host basalts, which could be explained by that the primary alkalic melt was reactively modified during magma ascent in the SCLM. The primary melt has geochemical characteristics consistent with partial melting of a veined carbon-rich amphibole clinopyroxenite source in the SCLM formed metasomatically during circum-craton subduction events. The findings highlight that the carbon introduced into the cratonic SCLM during subduction could be subsequently reactivated and transferred to the crust and atmosphere through decratonization-related magmatism, which might represent a major process regarding the SCLM in regulating the terrestrial carbon cycle. • CO 2 in decratonization-related magma is measured utilizing melt inclusions; • The primary magma contains abundant CO 2 (∼0.6 wt%) and was reactively modified; • A carbon-rich veined metasomatic source in the SCLM is responsible for the magma; • Decratonization acts as a potential process for remobilizing carbon in the SCLM. [ABSTRACT FROM AUTHOR]

The oxygen fugacity (f O 2) of the Earth's mantle is a key parameter that regulates fundamental geological processes such as planetary differentiation, mantle melting, and volatile cycling. Large igneous provinces (LIPs) are among the most voluminous mafic volcanic eruptions in the Earth's history. Constraining the f O 2 of LIP rocks is critical for understanding the redox state of the mantle and migration of volatiles from the deep Earth to the atmosphere. Here, we investigated primitive picrites from the Dali and Lijiang areas belonging to the Emeishan LIP, which contain early-crystallized olivine phenocrysts with Fo contents up to 93.5 and 91.9, respectively. The f O 2 conditions of primary and derivative melts are determined by the olivine-spinel and olivine-melt V oxybarometers, aided by temperature estimates from olivine-spinel Al and olivine-melt Sc/Y thermometers. The calculated f O 2 values are negatively correlated with olivine Fo contents due to fractionation of mafic minerals in a system closed to oxygen. The f O 2 s of Dali and Lijiang primary melts are −0.8 ± 0.4 and + 0.6 ± 0.3 (1σ) ΔFMQ log units, respectively, more variable than those of primitive MORBs, indicating significant f O 2 fluctuations in primary magmas from the Emeishan LIP caused by changes in both redox state of the source rock and depth of melt extraction. Melt barometer constrains the Dali and Lijiang primary melts generated at 4.7 and 3.0 GPa, respectively. After correcting for the depth effect, the Dali and Lijiang sources are more oxidized (with higher Fe3+/∑Fe ratios), in varying degrees, than the ambient upper mantle, likely due to incorporation of recycled surface materials. Under such oxidized conditions, mantle carbon is efficiently extracted during melting in the form of CO 2 and released to the atmosphere during massive magma emplacement, which may have played an important role in causing the climatic and environmental changes and triggering the end-Guadalupian mass extinction. [ABSTRACT FROM AUTHOR]

It is intriguing to speculate on how continental crust grew and differentiated during the Archean and which tectonic regimes and magmatic mechanisms were responsible for such a process. The continental nucleus of the Kaapvaal Craton, which includes the Barberton granitoid-greenstone terrane (BGGT) in South Africa and the Ancient Gneiss Complex (AGC) in Swaziland, exhibits the best preserved geological record from 3.6 to 3.0 Ga and thus provides the optimal location to address this issue. In this study, combined U-Pb, O and Lu-Hf isotope and trace element analyses were carried out on detrital zircon grains from two Moodies Group sandstones and three modern river sand samples in the Barberton and Swaziland regions, southern Africa. The results, in conjunction with previously published data, show that the detrital zircons in the Moodies sandstones on both sides of the Inyoka Fault, had two similar U-Pb age clusters of 3.25–3.30 Ga and 3.40–3.47 Ga and the oldest age up to 3.57 Ga. This suggests that they were derived from older felsic volcanic rocks of the greenstone belt and the granitoid gneisses in the BGGT and AGC. Using the approach created for Earth's oldest zircons (i.e., Jack Hills detrital zircons), we inferred that the source magmas of the studied detrital zircons had average arc-like andesitic compositions (SiO 2 = 58.0 ± 5.6 wt.%; Th/Nb = 5.0 ± 3.2), similar to those of the Jack Hills detrital zircons. However, these inferred compositions conflict with the source rocks of the detrital zircons, namely, the felsic volcanic rocks and the granitoid gneisses in the BGGT and AGC, which have high SiO 2 contents (average = 70 ± 4.3 wt.%) and moderate Th/Nb ratios (average = 0.76 ± 0.44). These findings suggest that the inferred average andesitic compositions for the Earth's oldest zircons should be reevaluated. The U-Pb age spectra of detrital zircons in modern river sands suggest that the exposed rocks in southwestern Swaziland are dominantly ca. 3.45 Ga tonalitic, trondhjemitic and granodioritic (TTG) gneisses without Eoarchean crust. The concordant zircon U-Pb age data reveal four major magmatic episodes for the eastern Kaapvaal Craton at 3.52, 3.46, 3.26 and 3.10 Ga. The first magmatic episode is suggested to dictate crustal growth, whereas the other three magmatic episodes are predominated by crustal reworking. This process is manifested by major positive changes in ε Hf (t) and ε Nd (t) values starting at ∼3.5 Ga, gradual decreases in ε Hf (t) and ε Nd (t) values afterwards, and increases in δ18O values at ∼3.25 Ga. Combined with other geological observations, we suggest that modern-style plate tectonic processes, such as subduction, may not have been a requirement for crustal growth and reworking in the eastern Kaapvaal Craton during the Paleoarchean (3.6–3.2 Ga). Instead, they could be ascribed to episodic partial convective overturns at different crustal depths. [ABSTRACT FROM AUTHOR]

The North China Craton (NCC) experienced strong destruction (i.e., decratonization) during the Mesozoic, which triggered intensive magmatism, tectonism and thermal events and formed large-scale gold and other metal deposits in the eastern part of the craton. However, how the decratonization controls the formation and distribution of large-scale of gold and other metal deposits is not very clear. Based on a large number of published data and new results, this paper systematically summarizes all the data for the rock assemblages, chronology, geochemistry and petrogenesis of Mesozoic magmatic rocks, as well as for the mineralizing ages of gold and other metal deposits and the evolution of the Mesozoic basins in the eastern NCC. The results are used to restore the extensional rates of Mesozoic to Cenozoic basins and the strike-slip distance of the Tanlu Fault, to ascertain the location of the Paleo-Pacific plate subduction zones during the Mesozoic to Cenozoic, and to reconstruct the temporal and spatial distribution of Mesozoic gold and other metal deposits and magmatic rocks in the eastern NCC. It is obtained that the magmatism and mineralization in the eastern NCC westward migrate from east to west during the Early to Middle Jurassic, but they eastward migrate from west to east during the Early Cretaceous. The metallogenesis of these deposits is genetically related to magmatism, and the magmas provided some ore-forming materials and fluids for the generation of metal deposits. The geodynamic mechanism of decratonization and related magmatism and mineralization is proposed, i.e., the westward low-angle subduction of the Paleo-Pacific slab beneath the NCC formed continental magmatic arc with plenty of porphyry Cu-Mo-Au deposits in the Jurassic, similar to the Andean continental arc in South America. The mantle wedge was metasomatized by the fluids/melts derived from the subducting slab, laying a material foundation for hydrothermal mineralization in the Early Cretaceous. While the rollback of the subducting slab with gradually increasing subduction angle and the retreat of the subduction zones during the Early Cretaceous induced strong destruction of the craton and the formation of extensive magmatic rocks and large-scale gold and other metal deposits. [ABSTRACT FROM AUTHOR]

Abundant arc-type magmatic and metamorphic rocks exist on Earth today, which provide insights into the equilibrium state of the subduction process. However, magmatic samples generated during the initial stage of subduction is largely unknown. This hinders our understanding of the subduction initiation process and by inference, the onset of plate tectonics as well as the history of crustal formation. To address this issue, we carried out a comprehensive geochemical-geochronological study of a suite of Late Triassic to mid-Jurassic plutonic rocks from southern Alaska that potentially represent magmas from the initial to mature stages of arc formation. While all studied samples show typical arc-type geochemical signatures, i.e., enrichment of large ion lithophile elements (LILEs) and depletion of high field strength elements (HFSEs) relative to the heavy rare earth elements (HREEs), the Late Triassic trondhjemites show unique geochemical features such as strongly positive ε Hf (t) and ε Nd (t) coupled with lower δ 18O (average 4.77‰ ± 0.09‰). These signatures, along with its higher zircon saturation temperatures compared with younger plutonic rocks, are best explained by shallow partial melting of subducting high-temperature hydrothermally altered lower oceanic crust (i.e., gabbro). If true, these surprising findings would open up new ways to study subduction initiation which would have important bearing on future research on the onset of global plate tectonics and the formation of the continental crust. [ABSTRACT FROM AUTHOR]

The magnesium (Mg) isotopic distinction between surficial carbonate and mantle rock makes the Mg isotopes a potential tracer for recycled crustal materials (especially the carbonate-bearing materials) within the mantle. However, whether or to what extent recycled carbonate-bearing crustal materials could influence the Mg isotopes of the lithospheric mantle is still in debate. Here, we report the Mg isotope data for three well-characterized alkaline complexes from the northern margin of the North China Craton, i.e., the Hekanzi, Yaojiazhuang and Saima alkaline complexes. These alkaline rocks were all derived from enriched lithospheric mantle sources beneath the craton margin that were variably metasomatized by carbonate-bearing recycled crustal materials. However, they have relatively homogeneous and normal mantle-like δ26Mg values, i.e., −0.23 to −0.25‰ for the Hekanzi, −0.20 to −0.30‰ for the Yaojiazhuang and − 0.25 to −0.30‰ for the Saima alkaline rocks, respectively. These Mg isotopic characteristics were unrelated to shallow crustal processes (i.e., surface alteration, fractional crystallization and crustal assimilation) but inherited from the mantle sources. The mantle-like Mg isotopes suggest that the recycled carbonate-bearing crustal materials did not change the Mg isotopic compositions of the lithospheric mantle overlying the subduction zone, which mainly ascribes to the large contrast of MgO contents between the recycled crustal materials and the lithospheric mantle peridotite. The MgO contents of calcite-rich carbonates in the metasomatic agents released from the subducted crustal materials are too low to induce Mg isotopic anomaly in the MgO-rich peridotite. Our work reveals that Mg isotopes might not be a sensitive tracer of carbonate melt/fluid metasomatism in the lithospheric mantle beneath the craton margins. • Magnesium isotopes are reported for alkaline rocks from the craton margin. • The consistent mantle-like Mg isotopes unrecord recycled carbonates. • Large MgO contrast and calcite-rich metasomate buffer the effect on mantle δ26Mg. [ABSTRACT FROM AUTHOR]

Alkaline rocks commonly occur as volcanic-plutonic ring complexes, but the petrogenetic mechanism for the coexistence between volcanic and plutonic rocks remains controversial. The Early Cretaceous Houshihushan alkaline ring complex in the Yanshan Fold and Thrust Belt, China, contains arfvedsonite granites surrounded by syenites, trachytes and alkali rhyolites. In situ trace elements and Sr-Nd isotopic compositions of apatites from these rocks are presented to constrain the petrogenetic link between coeval alkaline volcanic and plutonic rocks. Petrographic and geochemical features suggest that apatites in the trachyte crystallized from the melt at an early stage. Their initial 87Sr/86Sr ratios (0.7048–0.7052) and ε Nd (t) values (−21.9 to −17.6) well constrain the Sr-Nd isotopic compositions of the lithospheric mantle source for the trachyte, better than those of whole-rock (0.7114 and −18.6, respectively). In contrast, apatites in the syenites crystallized from host melt throughout the whole history of magma evolution. Their geochemical features and variable initial 87Sr/86Sr ratios (0.7084–0.7175) and ε Nd (t) values (−16.0 to −12.7) suggest that the syenites were formed by the cumulation of their parental magma, coupled with gradually mixed by felsic magma with a high initial 87Sr/86Sr ratio. However, a few and small-size apatite grains crystallized from parent magma of the arfvedsonite granites and alkali rhyolites suggest that in situ geochemistry of apatites is not feasible to constrain the petrogenetic process of high-silica alkaline rocks. Combined with whole-rock data, the geochemical features and Sr-Nd isotopic compositions of apatites indicate a crystal mush model to interpret the genetic link between syenites and arfvedsonite granites and alkali rhyolites. The early accumulations of mixing mafic and felsic magmas formed syenites at the margin, while the residual silicic melts solidified as arfvedsonite granites at the core. After the exposure of the intrusive rocks by rapid exhumation, the injection of high-temperature mantle-derived magma into the crystal mush promoted the extraction of the residual melt from the magma chamber. The mantle-derived magmas and residual melts directly erupted to the surface to form trachyte and rhyolite in the middle, eventually forming the alkaline ring complex. • Distinct origins for apatite grains in the Houshihushan alkaline ring complex. • Early-stage crystallized apatite records Sr-Nd isotope signature of the source. • Apatite can reveal the detailed petrogenetic processes of alkaline rocks. • Alkaline ring complex is formed by cumulation-crystal fractionation-magma mixing. [ABSTRACT FROM AUTHOR]

Rutile stands as a classical mineral within U‐Pb geochronology, offering insights into both magmatic and metamorphic events, and contributing to the understanding of provenance of detrital sedimentary rocks. Addressing the paucity of high‐quality Archaean rutile reference materials suitable for microbeam U‐Pb dating, we present a natural rutile (RKV01) sourced from the Kaap Valley pluton, South Africa, positing it as a potential Archaean reference material. Major element determination was executed via electron probe microanalysis, while trace element determination was conducted using laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS). The determination of U‐Pb ages involved the application of isotope dilution‐thermal ionisation mass spectrometry (ID‐TIMS), secondary ion mass spectrometry (SIMS) and LA‐ICP‐MS. The ID‐TIMS mean 207Pb/206Pb age is 3225.61 ± 0.64 Ma (2s, MSWD = 0.83), interpreted as the best estimate for the crystallisation age. The relatively high U mass fraction (~ 83 μg g‐1), extremely low Th mass fraction (~ 0.003 μg g‐1), negligible common Pb and isotopically homogeneous compositions collectively facilitated precise 207Pb/206Pb age determination via microbeam methods. Both LA‐ICP‐MS and SIMS 207Pb/206Pb ages are characterised by reproducibility and were consistent with the ID‐TIMS age within 2s analytical uncertainty. The results underscore the potential of RKV01 rutile as an Archaean reference material for microbeam U‐Pb dating. [ABSTRACT FROM AUTHOR]

The formation of rodingites has been a continually controversial topic, largely due to the absence of minerals that can be unambiguously dated. Here, we present a case study that utilized LA‐ICPMS garnet U–Pb dating, in conjunction with field investigations, petrology and Raman spectroscopy, to reveal the age and petrogenesis of rodingite in the northern North China Craton. The rodingites are spatially associated with mafic and alkaline rocks. Our findings indicate that rodingitization occurred at ca. 388 Ma, making it about 5–10 Myr younger than its mafic protoliths, but contemporaneous with the adjoining alkaline plutons. These observations suggest that the rodingitization may be attributed to hydrothermal fluids from the alkaline magmas. Our study emphasizes the importance of utilizing garnet U–Pb dating to determine the timing of rodingitization and introduces a novel perspective on the relationship between rodingitization and alkaline magmas in extensional continental settings. [ABSTRACT FROM AUTHOR]

The short-lived 182Hf-182W system has been used to constrain the early Earth's accretion and differentiation. This paper reports high precision W isotopic compositions and trace element concentrations for Archean (4.0–3.0 Ga) intermediate to felsic rocks from the Slave, North China, and Kaapvaal cratons to discuss early Earth differentiation and mantle mixing processes. The 4.0–3.8 Ga diorite and trondhjemite samples from the Acasta Gneiss Complex (AGC) in the Slave Craton and Anshan Complex in the North China Craton have positive μ182W values ranging from 8.3 ± 3.6 to 14.5 ± 4.0, whereas the 3.36–2.95 Ga TTG rocks from the North China Craton have a uniform modern mantle-like μ182W value of 0.7 ± 3.9 (2 SD, n = 11); with one exception, the 3.32 Ga old sample F28-2, which has a positive μ182W anomaly (7.3 ± 3.9 and 13.0 ± 3.2 for two individual analyses). The Earth's oldest potassic granites, occurring as conglomerates in the Moodies Group, an intrusive trondhjemite, and an amphibolite with ages of ~3.55 Ga in the Kaapvaal Craton exhibit W isotopic compositions indistinguishable from what is proposed for the modern mantle. The positive 182W anomalies in the 4.0–3.8 Ga rocks could possibly be the result of either early mantle differentiation that occurred within the lifetime of 182Hf or a partial lack of late accreted material. The signature of 182W excess in the 3.32 Ga sample (F28-2) is inherited from earlier crust, presumably similar to the 3.8 Ga TTGs, either by melting or crustal contamination. The transition in μ182W values from positive to near-zero would indicates that a significant event occurred at ∼3.6 Ga which caused efficient mixing of early differentiated mantle and late accreted material, possibly indicating the transition of tectonic regimes from plume to plate tectonics on the Earth. [ABSTRACT FROM AUTHOR]

In situ U–Pb and Hf analyses were used for crustal zircon xenocrysts from Triassic kimberlites exposed in the Rangnim Massif of North Korea to identify components of the basement hidden in the deep crust of the Rangnim Massif and to clarify the crustal evolution of the massif. The U–Pb age spectrum of the zircons has a prominent population at 1.9–1.8 Ga and a lack of Archaean ages. The data indicate that the deep crust and basement beneath the Rangnim Massif are predominantly of Palaeoproterozoic age, consistent with the ages of widely exposed Palaeoproterozoic granitic rocks. In situ zircon Hf isotope data show that most of the Palaeoproterozoic zircon xenocrysts have negative ϵ Hf(t) values (−9.7 to +0.7) with an average Hf model age of 2.86 ± 0.02 Ga (2 σ), which suggests that the Palaeoproterozoic basement was not juvenile but derived from the reworking of Archaean rocks. Considering the existence of Archaean remanent material in the Rangnim Massif and their juvenile features, a strong crustal reworking event is indicated at 1.9–1.8 Ga, during which time the pre-existing Archaean basement was exhausted and replaced by a newly formed Palaeoproterozoic basement. These features suggest that the Rangnim Massif constitutes the eastern extension of the Palaeoproterozoic Liao–Ji Belt of the North China Craton instead of the Archaean Liaonan Block as previously thought. A huge Palaeoproterozoic orogen may exist in the eastern margin of the Sino-Korean Craton. [ABSTRACT FROM AUTHOR]

In this work, we report the geochemical, whole-rock Sr-, Nd-, and Hf-isotopes, and zircon U–Pb age and Hf–O isotopic compositions for six granitic intrusions in northeastern Fujian, coastal region of southeastern China, to elucidate the petrogenesis of aluminous and peralkaline A-type granites in this region. Zircon U–Pb dating of these rocks (including porphyritic syenites, porphyritic granites, alkali-feldspar granites, and arfvedsonite granites) yielded Late Cretaceous ages of 94–98 Ma. Mineral assemblage and geochemical features suggested that the arfvedsonite granites were peralkaline A-type but the porphyritic syenites, porphyritic granites, and alkali-feldspar granites were aluminous A-type. Geochemical data, whole-rock Nd–Hf isotopes (ε Nd (t) = −5.5 to −4.0, ε Hf (t) = −3.6 to 0), and the zircon Hf–O isotopes (ε Hf (t) = −3.0 to +1.4, δ18O = 5.4‰–6.0‰) indicated that the porphyritic syenites were produced by partial melting of crustal rocks in the lower crust. The porphyritic granites and alkali-feldspar granites had similar geochemical features and zircon Hf–O isotopic composition with the porphyritic syenites, suggesting that they were formed by feldspar-dominant crystal fractionation of deep crust derived syenitic magma under shallow crustal level. Compared with the aluminous A-type granites, the peralkaline A-type granites had lower abundance of Al 2 O 3 , MgO, CaO, Ba, and Sr, higher abundance of SiO 2 and HFSE, as well as higher ratio of total FeO/MgO, Ga/Al, and Rb/Sr. However, the whole-rock Nd-, Hf- and zircon Hf–O isotopic compositions of the peralkaline and aluminous A-type granites were similar. It could be inferred that the peralkaline A-type granites were formed by crystal fractionation of aluminous A-type granitic magmas. Since the studied A-type granitic intrusions were coeval with the bimodal volcanic rocks and the extensional basins in the coastal region of southeastern China, they were likely produced in an extensional setting, possibly during lithospheric thinning that resulted from the subduction of the paleo-Pacific plate beneath southeastern China. • Aluminous and peralkaline A-type granites were crystallized at 94–98 Ma. • Aluminous and peralkaline A-type granites were derived from a common source. • Aluminous A-type granite was produced by partial melting of lower crustal rocks. • Peralkaline A-type granite was formed via crystal fractionation. [ABSTRACT FROM AUTHOR]

The occurrence of high‐pressure (HP) garnet‐bearing metamorphic rocks in the southern Barberton granitoid–greenstone terrane (BGGT), South Africa, has been proposed as a key indicator of the onset of modern plate tectonics at ca. 3.2 Ga. Here, we report new zircon/titanite U–Pb ages of garnet‐bearing HP metamorphic rocks and associated granitoids in the BGGT that argue against such an interpretation. The results show that HP metamorphism occurred synchronously with granitoid magmatism in the Stolzburg domain, the supposed subducted plate, during two episodes at 3.4 and 3.2 Ga, and that these two episodes of magmatism occurred on both sides of the assumed suture zone, a feature that cannot easily be explained by the subduction model. In contrast, the coupled magmatism and metamorphism probably resulted from partial convective overturn (PCO), another viable mechanism for production and differentiation of continental crust during early Archean. [ABSTRACT FROM AUTHOR]

The North China Craton (NCC) was originally formed by the amalgamation of the eastern and western blocks along an orogenic belt at ∼1.9 Ga. After cratonization, the NCC was essentially stable until the Mesozoic, when intense felsic magmatism and related mineralization, deformation, pull-apart basins, and exhumation of the deep crust widely occurred, indicative of destruction or decratonization. Accompanying this destruction was significant removal of the cratonic keel and lithospheric transformation, whereby the thick (∼200 km) and refractory Archean lithosphere mantle was replaced by a thin (<80 km) juvenile one. The decratonization of the NCC was driven by flat slab subduction, followed by a rollback of the paleo-Pacific plate during the late Mesozoic. A global synthesis indicates that cratons are mainly destroyed by oceanic subduction, although mantle plumes might also trigger lithospheric thinning through thermal erosion. Widespread crust-derived felsic magmatism and large-scale ductile deformation can be regarded as petrological and structural indicators of craton destruction. ▪ A craton, a kind of ancient continental block on Earth, was formed mostly in the early Precambrian (>1.8 Ga). ▪ A craton is characterized by a rigid lithospheric root, which provides longevity and stability during its evolutionary history. ▪ Some cratons, such as the North China Craton, can be destroyed by losing their stability, manifested by magmatism, deformation, earthquake, etc. [ABSTRACT FROM AUTHOR]

Mineral compositions, clinopyroxene trace-element and Sr-Nd-Hf isotopic compositions, whole-rock major element and platinum group element (PGE) contents, and Re-Os isotopes are reported for peridotite xenoliths in the Cenozoic alkali basalts from Yangyuan, Hebei Province (China), in order to constrain the nature of the subcontinental lithospheric mantle beneath the central part of the North China Craton, and further to investigate the mechanism of decratonization. The xenoliths mainly consist of spinel lherzolites and minor spinel pyroxenites and spinel harzburgites with equilibration temperatures of 890–1060 °C. The olivine in these xenoliths have Mg number (%Fo) ranging from 88.2 to 91.6. According to the chemical characteristics, two groups of peridotites can be identified, i.e., group 1 are spinel lherzolites and spinel harzburgite that are depleted in Pt, Pd and Re (i.e., P-PGEs) relative to Os, Ir and Ru (i.e., I-PGEs) and their clinopyroxenes are depleted in light rare earth elements (LREEs), whereas, Group II are spinel lherzolites that are enriched in P-PGEs relative to I-PGEs and their clinopyroxenes are enriched in LREEs relative to HREEs. The spinel lherzolites have radiogenic 187 Os/ 188 Os ratios ranging from 0.1182 to 0.1262, whereas, the spinel harzburgites have relatively low 187 Os/ 188 Os ratios with Proterozoic model ages. Clinopyroxenes in the peridotite xenoliths have variable but relatively unradiogenic Sr ( 87 Sr/ 86 Sr = 0.7026–0.7046) and radiogenic Nd (ε Nd = +2.0 to +14.7) and Hf (ε Hf = +8.8 to +37.9) isotopic compositions. All these geochemical features indicate that the subcontinental lithospheric mantle beneath Yangyuan had experienced variable degrees of melt extraction and mantle metasomatism by the silicate melts represented by spinel pyroxenites. The spinel pyroxenites are enriched in LREEs and P-PGEs relative to HREEs and I-PGEs. Clinopyroxenes in pyroxenite xenoliths have high 87 Sr/ 86 Sr ratios of 0.7054–0.7063, negative ε Nd (−3.4 to −15.8) and ε Hf (−2.0 to −22.0) values, and high 187 Os/ 188 Os ratios of 0.2196–0.3343, indicating that the silicate melts were derived from ancient lower continental crustal materials. Our data suggest that the lithospheric mantle beneath Yangyuan had been metasomatized by silicate melts derived from recycled ancient lower crust, indicating that decratonization of the North China Craton was possibly induced by delamination of the lower crust and lithospheric mantle. [ABSTRACT FROM AUTHOR]

An improved chemical method is developed to accurately measure the W isotopic compositions of silicate samples with a precision of better than ±0.05ε on ε182W. Compared with the conventional method, two developments of this method mainly include the sample digestion process that is modified to better W dissolution from the co-precipitations and the W separation procedure. The optimized extraction chromatography using TEVA resin is designed to more efficiently separate W from Ti, Zr and Hf after the first-stage cation-exchange procedure with the percent recovery of W more than 85%. The blank during the whole procedure is less than 0.3 ng and is negligible for W isotopic analysis. The W isotopic ratios of Alfa Aesar W standard solution and a variety of silicate reference materials, i.e., RGM-2, GSP-2, AGV-2, JB-3, BCR-2 and BHVO-2, are measured by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). RGM-2, GSP-2, AGV-2, JB-3 and BCR-2 have normal ε182W values, identical to that of the terrestrial Alfa Aesar W standard, whereas BHVO-2 has a negative ε182W value of −0.09 ± 0.05 (2SD, N = 10). The duplicate measurements of Alfa Aesar W standard solution RGM-2 and BHVO-2 show that the external reproducibility of ε182W is usually better than 5 ppm (2SD), which is the most precise among the published data measured by MC-ICPMS and can be comparable to the precision acquired by negative thermal ionization mass spectrometry (N-TIMS) (about 5 ppm). All these results show that our new method provides an efficient way to precisely measure W isotopic compositions of silicate materials. It provides a widely useful tool to reveal the earliest history of the silicate earth and offers the ability to resolve sub-million-year age differences in meteorites. [ABSTRACT FROM AUTHOR]

Voluminous Mesozoic felsic volcanic rocks and granites in southeastern China provide a unique opportunity for studying the role of crustal magmatism in the evolution and modification of the crust in the eastern Cathaysia Block. The high-silica rhyolites of the upper volcanic sequence in eastern Zhejiang Province were investigated, focusing on their genesis and their relationship with contemporaneous granites. Rhyolites in the Tiantai, Yongkang and Liucheng basins were dated as late Early Cretaceous (from 111 Ma to 106 Ma in age). These rocks contain a large proportion of inherited zircons of ca. 130 Ma, corresponding to the age of the lower volcanic sequence in the area. However, the zircons of different ages have similar ranges of oxygen and Hf isotopes, implying similarities in the magmas from which they were generated. The rhyolites of the upper sequence also resemble those of the lower sequence in terms of their geochemistry. It is concluded that the former were derived by reworking of magma mush formed during the earlier magmatic episode via fractionation of feldspars and accessory minerals, e.g., zircon. Fractionation took place within the magma crystal mush by extraction of interstitial melts and accumulation of residual mineral phases, aided by the emplacement of contemporaneous basaltic magmas at the base of the crust. Overall, the geochemical features of the volcanic rocks in southeastern China indicate that episodic magmatism and reworking of crystal mush were essential mechanisms that drove the evolution of the igneous rocks and the hence crustal architecture in this area. [ABSTRACT FROM AUTHOR]

Major and trace element, whole-rock Sr-, Nd- and Hf-isotope, zircon U-Pb age and Hf-O isotope data are reported for the intrusive rocks from the Matsu Islands in the coastal area of southeastern (SE) China, in order to study the ages, sources and petrogenesis of these rocks and evolution of the lower crust. The rocks include gneissic granite, massive granite, brecciated granite and diabase. Secondary ion mass spectrometer (SIMS) zircon U-Pb dating reveals that the rocks in the Matsu Islands were emplaced at ∼160 Ma, ∼130 Ma and ∼94 Ma. The Jurassic granites (∼160 Ma) have high SiO 2 (74.1–74.5 wt%) and K 2 O + Na 2 O (8.32–8.33 wt%) contents and high Rb/Sr ratios of 0.6–1.2 and (La/Yb) CN ratios of 12.6–19.4. Their relatively high initial 87 Sr/ 86 Sr ratios (0.7074–0.7101), variable and negative ε Nd (t) values (−9.2 to −5.4), and variable zircon ε Hf (t) (−17.0 to +5.2) and δ 18 O (4.7–8.1‰) values indicate they were mainly derived from an ancient lower crustal source, but with involvement of high ε Hf (t) and low δ 18 O materials. The Early Cretaceous diabase (∼130 Ma) has SiO 2 content of 56.5 wt%, relatively high MgO concentration, low initial 87 Sr/ 86 Sr ratio and negative ε Nd (t) value, similar to geochemical features of other Cretaceous mafic rocks in the coastal area of SE China. Zircons from the diabase have high ε Hf (t) values (−5.5 to +0.2) and relatively low δ 18 O values of 4.2–5.0‰. These characteristics indicate that the parental magma of the diabase was generated by partial melting of enriched lithospheric mantle, which have been metasomatised by altered oceanic crust-derived low-δ 18 O fluids. For the Cretaceous granitoids (∼130 Ma and 94 Ma), they have relatively low SiO 2 (68.0–71.3 wt%) and K 2 O + Na 2 O (5.30–7.55 wt%) contents and low Rb/Sr ratios and (La/Yb) CN ratios of 5.8–7.1. They have low initial 87 Sr/ 86 Sr ratios (0.7071–0.7082), homogeneous ε Nd (t) (−4.3 to −4.5) and relatively high zircon ε Hf (t) values (−3.7 to +1.2) and low δ 18 O values (4.6–5.9‰). Their isotopic compositions are similar to those of the diabases in this study as well as other Cretaceous mafic rocks in the coastal area of SE China, suggesting that the sources of the Cretaceous granitoids might be the newly formed lower crust related to the underplated mafic rocks. Whole-rock geochemical, Sr-Nd and zircon Hf-O isotopic compositions indicate that the Jurassic granitoids are most likely generated by partial melting of relatively ancient basement rocks, whereas the Cretaceous granitoids were generated by partial melting of relatively young lower crustal rocks with addition of mantle-derived magma. This distinction implies that the pre-existing ancient lower crust beneath the coastal area of SE China has been modified by large-scale mafic magma underplating. Therefore, underplating of mantle-derived mafic magma would result in modification of the pre-existing ancient lower crust and formation of the relatively juvenile lower crust. [ABSTRACT FROM AUTHOR]

Whole rock major and trace element and Sr-, Nd- and Hf-isotope data, together with zircon U-Pb, Hf- and O-isotope data, are reported for the Nb-Ta ore bearing granites from the Lingshan pluton in the Southeastern China, in order to trace their petrogenesis and related Nb-Ta mineralization. The Lingshan pluton contains hornblende-bearing biotite granite in the core and biotite granite, albite granite and pegmatite at the rim. In addition, numerous mafic microgranular enclaves occur in the Lingshan granites. Zircon SIMS U-Pb dating gives consistent crystallization ages of ca. 132 Ma for the Lingshan granitoids and enclaves, consistent with the Nb-Ta mineralization age of ∼132 Ma, indicating that mafic and felsic magmatism and Nb-Ta mineralization are coeval. The biotite granites contain hornblende, and are metaluminous to weakly peraluminous, with high initial 87 Sr/ 86 Sr ratios of 0.7071–0.7219, negative ε Nd (t) value of −5.9 to −0.3, ε Hf (t) values of −3.63 to −0.32 for whole rocks, high δ 18 O values and negative ε Hf (t) values for zircons, and ancient Hf and Nd model ages of 1.41–0.95 Ga and 1.23–1.04 Ga, indicating that they are I-type granites and were derived from partial melting of ancient lower crustal materials. They have variable mineral components and geochemical features, corresponding extensive fractionation of hornblende, biotite and feldspar, with minor fractionation of apatite. Existence of mafic microgranular enclaves in the biotite granites suggests a magma mixing/mingling process for the origin of the Lingshan granitoids, and mantle-derived mafic magmas provided the heat for felsic magma generation. In contrast, the Nb-Ta mineralized albite granites and pegmatites have distinct mineral components and geochemical features, which show that they are highly-fractionated granites with extensive melt and F-rich fluid interaction in the generation of these rocks. The fluoride-rich fluids induce the enrichment in Nb and Ta in the highly evolved melts. Therefore, we conclude that the Nb-Ta mineralization is the result of hydrothermal process rather than crystal fractionation in the Lingshan pluton, which provides a case to identify magmatic and hydrothermal processes and evaluate their relative importance as ore-forming processes. [ABSTRACT FROM AUTHOR]

A-type granites are a distinctive group of igneous rocks classified based on chemical and mineralogical criteria. Although numerous theories for the origin of A-type granite have previously been proposed, their genesis remains highly controversial. In the current study, we present bulk-rock geochemistry and zircon U Pb isotopes, Hf isotopes, and trace elemental data for a suite of quartz monzonite, porphyritic granite, and miarolitic alkali feldspar granite from the coastal area of Fujian, southeastern China, to evaluate the genetic link between these rocks. Zircon U Pb dating indicates that these rocks were crystallized at ∼94–102 Ma. Our data strongly suggests that lithological differences in these rocks are the result of crystal-melt segregation in the shallow crust. The quartz monzonites are enriched in Sr and Ba, with high Zr/Hf and low silica content and a weak negative Eu anomaly, representing the cumulate residue from the crystal-melt segregation of a magma reservoir. A limited fraction of zircon from the quartz monzonite has evolved trace element signatures (high Hf, Nb, Y, U; low Eu/Eu⁎), indicating that the quartz monzonite represents a mixture of accumulated crystals and high silicic melt trapped in cumulate mush. The miarolitic alkali feldspar granites and porphyritic granites are enriched in silica and Rb, and depleted in Sr and Eu. They also display low whole-rock Zr/Hf and Eu/Eu⁎ ratios, and high Rb/Sr ratios, representing highly evolved silicic melts that were segregated from a magma reservoir. The majority of the zircon grains from the miarolitic alkali feldspar granites exhibit the most evolved trace element signatures (high Hf, Nb, Y, U; low Zr/Hf and Eu/Eu⁎) of the entire suite. This reveals that these zircons crystallized from the high silicic melts extracted from a magma reservoir. Magma recharge and the exsolution of volatiles from the interstitial melt have promoted the segregation and upward extraction of high silica magmas from a compacting magma reservoir in the upper crust. Our work demonstrates that the miarolitic alkali feldspar granites with A-type granite features from the coastal area of southeastern China were generated by the crystal-melt segregation process in a shallow crustal magma reservoir. [ABSTRACT FROM AUTHOR]

The Nanling Range (NLR) is the largest tungsten metallogenic province in China and perhaps in the world. The tungsten mineralization is believed to be related to Jurassic granitic magmatism. However, the petrogenesis of these granites and their relation to the tungsten mineralization are still debated. Whole-rock geochemical and Sr–Nd–Hf isotopic data and zircon in situ U–Pb ages and Hf–O isotopes are reported for W-bearing granitic intrusions from the southern Jiangxi Province in the NLR, in order to constrain their magmatic sources and petrogenesis. The NLR granites include biotite granites, two-mica granites and garnet muscovite granites. SIMS and LA-ICPMS U–Pb dating of zircons and monazites give emplacement ages of 161–154 Ma for these rocks. The granites are metaluminous to strongly peraluminous with high SiO 2 (> 72.3 wt.%) and high K 2 O (> 3.7 wt.%). Petrographic and geochemical features show that they are highly fractionated I-type granites. The biotite granites are enriched in light rare earth elements (LREEs) relative to heavy REEs, have weakly negative Eu anomalies and are depleted in Nb, Ba, P and Ti. In contrast, the two-mica and garnet-bearing muscovite granites have tetrad-type REE patterns with strongly negative Eu anomalies and are extremely depleted in Ba, Nb, Sr, P and Ti. Magmatic garnets are mainly almandine and spessartine, and have low-Mn cores and high-Mn rims. Their (Y + HREE) contents are high and generally decrease from core (1.2 wt.%) to rim (average = 4955 ppm). All of these granites are characterized by variable whole-rock initial 87 Sr/ 86 Sr (0.7053–0.8000), ε Nd (t) (− 12.6 to − 9.4) and ε Hf (t) (− 12.3 to − 8.5), as well as variable zircon ε Hf (t) and δ 18 O, with values of − 16.3 to − 7.4 and 7.6 to 10.0‰, respectively. They contain abundant zircon xenocrysts and xenoliths of micaceous schist. All of these features are consistent with a process of crystal fractionation of crustally-derived magmas coupled with strong assimilation of sedimentary rocks. The assimilation of meta-sedimentary materials increased the concentrations of tungsten, alumina and manganese in the magmas, whereas high degrees of crystal fractionation further enriched them in the evolved granitic rocks. The W-enriched magmatic fluids formed the tungsten-bearing quartz veins, revealing the genetic relationship between tungsten mineralization and emplacement of garnet-bearing two-mica or muscovite granites in the NLR. [ABSTRACT FROM AUTHOR]

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a powerful micro-analytical tool that has been widely used in geoscience because of its ability to rapidly and precisely analyze isotopes in situ with a typical spatial resolution of 30–80 microns. Here we present a new method for U–Pb dating of zircon with a higher spatial resolution at a scale of 5.8–7.4 μm in diameter and ＜3 μm in sampling depth (＜0.5 ng of zircon material consumption), using a 193 nm ArF excimer laser ablation system coupled with multiple ion counting inductively coupled plasma mass spectrometry (LA-MIC-ICP-MS). Ion counters have an obvious advantage when using a small ion beam (＜12.5 mV) and make it possible to date zircons with a 238U signal of ＜0.5 mV with improved spatial resolution. The new technique was evaluated by investigating six zircon standards with various known ages ranging from 32 Ma to 2060 Ma. Using this technique, we obtained a precision (2s) for the weighted mean 206Pb/238U age within 1% and an accuracy of ＜1% offset to the nominal reference age. We then further demonstrated the utility and robustness of the new high spatial resolution technique for its application to the real geological problem of complexly zoned zircons, to determine the age of the famous Dabie ultrahigh pressure metamorphism. We anticipate that the method will have a wide range of applications in high-resolution U–Pb dating of tiny or complex zircon grains with small cores or relatively narrow zones, with high efficiency and throughput in the geological research community. [ABSTRACT FROM AUTHOR]

An integrated study of zircon U-Pb ages and Hf-O isotopes, whole rock and apatite geochemistry, and whole rock Sr-Nd-Hf isotopes were conducted for the Jurassic adakitic volcanic rocks from the Tiaojishan Formation in the Yanshan Fold and Thrust Belt (YFTB) of the North China Craton, to investigate their genesis, with attention to the role of crust thickness in achieving the adakitic traits. Zircon U-Pb dating gives eruption ages of 162–158 Ma for these rocks. These rocks have variable SiO 2 (55.7–68.1 wt%) and MgO (0.35–4.0 wt%), and adakitic trace element signatures including high Sr/Y (27.9–100) and (La/Yb) N ratios (9.6–27.6). Chemical variations in whole rock and apatite suggest a feldspar-dominated fractional crystallization, superimposed by variable mineral accumulation on whole rock compositions. Together with isotopic compositions that include evolved whole rock (87Sr/86Sr) i = 0.70447–0.70591, ε Nd (t) = −17.5 to −12.1, and ε Hf (t) = −22.2 to −11.2, and zircon ε Hf (t) = −26.8 to −11.2 and δ18O = 5.7–7.0 ‰, we attribute these rocks are sourced from mafic lower continental crust. By comparing the trace element signatures between the examined samples and modern continental arc magmatic rocks formed at variable crustal thickness, it is suggested that these rocks are most likely originated from a thickened crust. A further estimate based on whole rock Sr/Y and La/Yb gives a crust thickness of 56 ± 7 km. The crust thickening and associated uplift of the YFTB could be attributed to the westward subduction of the Paleo-Pacific plate. This led to a high altitude (∼3.8 ± 0.9 km) and cool climate habitat (a mean annual paleotemperature of 7 ± 7 °C) for the Yanliao Biota lived therein during this period, which may have played an important role in the earliest appearance of the feathered characteristic of dinosaurs. • A thickened lower continental crust source is responsible for the volcanic rocks. • Crust thickening and uplift are related to the subduction of the Paleo-Pacific plate. • Uplift-induced cooling may be important for the appearance of feathered dinosaurs. [ABSTRACT FROM AUTHOR]

A combined study of zircon U–Pb ages, mineral chemistry, whole-rock elements and Sr–Nd–Hf isotopes was carried out for the Saima alkaline complex in the northeastern China, in order to investigate the source and petrogenesis of coeval silica-saturated and silica-undersaturated alkaline rocks. The Saima alkaline complex consists of nepheline syenites, quartz-bearing syenites and alkaline volcanic rocks (i.e., phonolite and trachyte), with minor mafic dikes and carbonatitic veins. Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and secondary ion mass spectrometry (SIMS) zircon U–Pb dating gives consistent ages of 230–224 Ma for these rocks, suggesting that they are coeval. All alkaline rocks in the Saima complex are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and depleted in high field strength elements (HFSEs) with significant negative Nb, Ta and Ti anomalies. Geochemical data and Sr–Nd–Hf isotopic compositions indicate that the various alkaline rocks were all derived from partial melting of an ancient, re-enriched lithospheric mantle in the garnet stability field, but experienced variable siliceous- or carbonate-rich crustal contamination. Based on petrographic evidence, mineral compositions, and whole-rock geochemical data, two distinct magmatic evolutionary trends are proposed to explain the coeval emplacement of the various rock types within the Saima alkaline complex. The silica-undersaturated rocks (nepheline syenites and phonolites) result from alkali feldspar + apatite + titanite crystal fractionation of an alkaline mafic parental melt combined with assimilation of marine carbonate host rocks. In contrast, the generation of silica-saturated rocks (quartz-bearing syenites and trachytes) may be attributed to subsequent and continued clinopyroxene + apatite + biotite crystal fractionation coupled with assimilation of siliceous sediments. [ABSTRACT FROM AUTHOR]

Whole-rock geochemical and Sr–Nd–Hf isotopic data and zircon in situ U–Pb ages and Hf–O isotopes are reported for twelve granitic intrusions from inland to coastal areas of the Cathaysia Block, Southeast (SE) China, in order to constrain their magma sources and petrogenesis. They are mainly composed of biotite granites with minor granodiorites. Zircon U–Pb dating by LA-ICPMS and SIMS methods gave emplacement ages of 165–154 Ma for these rocks, which are metaluminous to weakly peraluminous (A/CNK = 0.95–1.10), with variable SiO 2 contents and high K 2 O contents. They are all depleted in high field strength elements (HFSEs) and enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs), and show negative Sr, Ba and Eu anomalies in the spidergrams. Petrographic and geochemical features suggest the granodiorites that contain hornblende to be typical of I-type, while the biotite granites without hornblende are fractionated I-type granites. Their variable major and trace element concentrations are due to fractional crystallization of feldspar, biotite, hornblende, and accessory minerals, including apatite, allanite and monazite. Moreover, our data indicate significant variations in isotopic compositions of these granitoids from inland to coastal areas. The inland granites, from the Lapu, Fogang, Xinfengjiang and Baishigang plutons, have relatively high initial 87 Sr/ 86 Sr ratios (0.7105–0.7155) and low ε Nd ( t ) (−11.2 to −7.3) and ε Hf ( t ) (−10.9 to −6.3) values for whole rocks, and variable δ 18 O values of 7.69–9.25‰ and ε Hf ( t ) values of −13.5 to −6.7 for zircons. In contrast, the coastal granites, from the Longwo, Wushikeng, Lianhuashan, Shigushan, Chiliao, Hulutian, Mantoushan and Fenghuang plutons, show relatively low initial 87 Sr/ 86 Sr ratios (0.7056–0.7110) and high ε Nd ( t ) (−7.6 to −6.2) and ε Hf ( t ) (−6.5 to −2.8) values for whole-rocks, together with ε Hf ( t ) values of −7.2 to 3.9 and δ 18 O values of 6.69–8.38‰ for zircons. The spatial isotopic variations suggest that these Jurassic granitoids were generated by different-percentage mixing of mantle- and ancient (Paleoproterozoic) crust-derived magmas, with subsequently minor crustal assimilation. Our results highlight that Jurassic fractionated I-type granites occur widely from inland to coastal areas of SE China, arguing against the previous view that Jurassic granites occur only in inland while coastal granites are mainly Cretaceous. The widespread occurrence of Jurassic granitoids in SE China is attributed to ascending of mantle-derived magmas, which provide heat for partial melting of lower crustal materials, in an extensional setting. [ABSTRACT FROM AUTHOR]

Friedel–Crafts reaction of indoles to aromaticα-ketimino esters was found to be catalyzed by camphorsulfonic acid with good yields (up to 98%) under ambient temperature. This process provides an efficient method for the synthesis of unnatural amino acid derivatives that bear quaternary carbon centers. [ABSTRACT FROM PUBLISHER]

Objective To investigate the relationship between hepatic impairment and Th17/CD4+ T cells and IL-17 in the peripheral blood and hepatic tissues of patients with primary biliary cirrhosis (PBC) . Methods Peripheral blood and liver specimens of 26 PBC patients, 20 HBV infected patients and 20 healthy subjects were collected. The ratio of Thl7cells/CD4 +T cells was measured by flow cytometry (FCM) . Serum levels of IL-17 were tested by enzyme-linked immunosorbent assay (ELISA) and compared between different groups. Correlations of IL-17 with ALP and GGT were also analyzed. The levels of Thl7/CD4+T and IL-17 in different pathological stages were compared. Results Th17/CD4+T cells in peripheral blood and liver tissue and serum IL-17 of patients with PBC were significantly higher than those of patients infected by HBV or healthy control group (P < 0.05) . There were positive correlations of serum IL-17 with ALP and GGT (P < 0.05) . The level of Thl7/CD4 +T cells in the peripheral blood and hepatic tissue of patients with stage III-IV PBC were significantly higher than that of patients with stage I-II PBC. Conclusion Thl7/CD4+T cells and specific cytokine IL-17 secreted by Thl7/CD4+T cells may play a critical role in the immuno-pathogenesis and hepatic fibrosis of patients with PBC. [ABSTRACT FROM AUTHOR]

This study investigated the influences of plasma condition, concentration effect, ablation position and on-line addition of an aqueous Ni standard for non-matrix-matched Fe isotopic analysis by femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry (fs LA–MC–ICP–MS). Deviations up to ~0.7‰ in δ56Fe values caused by non-matrix-matched analyses were difficult to eliminate under dry plasma condition even with fs-LA. However, the nebulized water after the ablation cell efficiently reduces or eliminates the matrix-dependent fractionation of Fe isotopes without reducing signal intensity. Furthermore, concentration- and position-dependent fractionation of Fe isotopes was not observed under wet plasma condition. For instrumental mass bias correction, the standard–sample bracketing (SSB) method and SSB with Ni doping (SSB + Ni) were performed in the presence of nebulized water with fs LA–MC–ICP–MS. Results indicate that both the SSB and SSB + Ni methods are sufficient to correct for instrumental mass bias under wet plasma condition, with the SSB + Ni method being more effective in calibrating short-term fluctuations in mass bias with improved external reproducibility of ~0.15‰ (2SD) for δ56Fe values. Compared to SN–MC–ICP–MS, deteriorated precision offered by fs LA–MC–ICP–MS may represent a major limitation for some applications relying upon precise Fe isotope ratio measurements. This approach for non-matrix-matched analysis of Fe isotopes by fs LA–MC–ICP–MS under wet plasma condition combined with the SSB + Ni method allows for more flexibility in tracing detailed geological processes with large Fe isotope fractionation of a wide range of solids. Relatively precise and accurate Fe isotopic compositions of potential reference materials of Balmat pyrite (δ56Fe = −1.32 ± 0.12‰, δ57Fe = −1.91 ± 0.20‰; 2SD, n = 166) and PZH12–24 ilmenite (δ56Fe = −0.38 ± 0.15‰, δ57Fe = −0.57 ± 0.23‰; 2SD, n = 134) were obtained using this analytical protocol, consistent with reference values obtained by solution nebulization (SN)–MC–ICP–MS within analytical uncertainties (Balmat pyrite: δ56Fe = −1.30 ± 0.04‰, δ57Fe = −1.94 ± 0.07‰, 2SD, n = 3; PZH12–24 ilmenite: δ56Fe = −0.38 ± 0.06‰, δ57Fe = −0.55 ± 0.07‰, 2SD, n = 6). [Display omitted] • A strategy of non-matrix-matched Fe isotopic analysis by fs LA–MC–ICP–MS is provided. • Evaluation of plasma condition, concentration and position effect are discussed. • A comparison of SSB and SSB + Ni for mass bias correction is discussed. • Fe isotopic compositions of potential standards of pyrite and ilmenite are presented. [ABSTRACT FROM AUTHOR]

Abstract: Zircon U–Pb ages and in-situ trace elements and Hf–O isotope compositions, together with whole rock geochemical and Sr–Nd–Hf isotopic data, are presented for Cretaceous granitoids in southeastern (SE) China in order to establish their origin and the evolution of the underlying lithosphere during the Late Mesozoic. Two stages of Cretaceous magmatism, with contrasting geochemical features, have been identified: an earlier adakite-like biotite granite as represented by the Shangying pluton and a later enclave-bearing monzogranite as represented by the Zaoshan pluton. The Shangying biotite granites have a zircon U–Pb age of 99±1Ma. They have relatively low Y and Yb contents, with high La/Yb and Sr/Y ratios, showing geochemical features of adakite. Their Sr–Nd–Hf isotope compositions are similar to those of Early Cretaceous mafic rocks in the same area, indicating that they were generated by partial melting of juvenile granulitic crust at a depth of about 40km. The source was formed by underplating of enriched lithosphere mantle-derived magmas. In contrast, the Zaoshan calc-alkaline monzogranites, their enclaves and associated dolerite dykes from the Zaoshan pluton have an emplacement age of ~88±1Ma. The dolerites have high MgO contents, relatively low SiO2 concentrations and low La/Yb ratios, and depleted Hf isotope compositions. All these geochemical features suggest that they were derived from a depleted spinel Iherzolite mantle source. The enclaves have high SiO2 contents, indicating that they were derived from a crustal source. They have variable zircon Hf and O isotope compositions, suggesting that two components, i.e., a high εHf(t) and a low δ18O component and a low εHf(t) and high δ18O component, were involved in their origin. The high zircon εHf(t) values and low δ18O values are similar to those of the dolerites, indicating a common source. Thus, we suggest that the enclaves were generated by partial melting of newly underplated depleted mantle-derived materials. The monzogranites have distinctly different zircon Hf and O isotope compositions from the enclaves, indicating that the parental magmas were mainly derived from ancient crust that interacted with underplated depleted mantle-derived magmas. The monzogranites have relatively high HREE contents, suggesting a garnet-free source (<32km), distinct from the Early Cretaceous adakite-like granites that were generated from a garnet-bearing source. Combined with previously published data, it is evident that Early Cretaceous adakite-like magmatic rocks (107–99Ma) and associated mafic rocks (100–107Ma) were widespread in SE China, indicating a crustal thickening event that was possibly induced by underplating of mantle-derived magma. Subsequently, between 99 and 87Ma, crustal extension and lithospheric thinning induced the later widespread I-type granites with similar geochemical features to the Zaoshan pluton. A-type granites and syenites of this age are also present in SE China. The transition in geochemical and isotopic data, from enriched to depleted Hf isotope compositions as seen in the monzogranites, their enclaves and intrusive dolerites, suggest that depleted mantle-derived materials were involved in the generation of the monzogranites, further indicating continental crustal reworking and later crustal growth in SE China during the early Late Cretaceous. [Copyright &y& Elsevier]

Two new Cd(II) coordination polymers, namely [Cd(HOA)(μ-HO)(HO)]·3 nHO (1) and [Cd(HOA)(phen)]· nHO ( 2) (HOA = 3,3′,4,4′-oxidiphthalic acid, phen = 1,10-phenanthroline) have been synthesized by combining HOA or HOA and phen with Cd(II) salts under hydrothermal conditions. Single-crystal X-ray diffraction analysis reveals that 1 features a hydrogen-bond directed two-dimensional (2D) layered structure constructed from alternating left- and right-handed double strand helical chains, 2 represents a one-dimensional (1D) chain structure with the phen molecules dangling on it, which is further extended into a three-dimensional (3D) supramolecular framework through strong face-to-face π···π interactions. In addition, luminescent properties of these two compounds were also investigated in the solid state at room temperature. [ABSTRACT FROM AUTHOR]

Vesuvianite is a common accessory mineral that usually occurs in metamorphosed and metasomatised, argillaceous carbonate rocks (i.e., skarn rocks) and as a late crystallising phase in igneous rocks such as nepheline syenites. Vesuvianite is a Ca-rich mineral that preferentially incorporates Sr and light rare earth elements (LREEs). Given that vesuvianite is susceptible to alteration and commonly contains inclusions, in situ laser ablation analysis is the preferred approach for measuring its Sr–Nd isotopic compositions. The use of matrix-matched and homogeneous reference materials is a prerequisite for laser ablation isotope analyses. Two in-house vesuvianite standards M6635 and M659 were used for external correction during in situ laser ablation analysis for Sr and Nd isotopic compositions, respectively. In this paper, we apply in situ Sr and Sm–Nd isotope analyses for 11 vesuvianite samples (M6635, M784, M1377, M660, M1439, M1450, M6601, 13MDL176, Wilui, Hazlov, and Goodall) from different locations. The obtained Sr and Sm–Nd isotopic compositions for these vesuvianite samples are consistent with those obtained by solution-based methods using MC-ICP-MS, which demonstrates the robustness of our analytical methods. We recommend that samples M6635, M784, M1377, and M1450 are suitable vesuvianite reference materials for in situ Sr isotope analyses, and sample M659 is a potential vesuvianite reference material for in situ Sm–Nd isotope analyses. [ABSTRACT FROM AUTHOR]

The Cretaceous granitoids in eastern Zhejiang were examined to establish a model for the construction of the highly silicic upper crust in southeastern China. The studied rocks include quartz monzodiorite, quartz monzonite, alkali feldspar granite, and their microgranular enclaves (ME). Zircon U Pb dating suggests that the granitic rocks and MEs were emplaced at approximately 102–114 Ma. Geochemical features and isotopic compositions of the quartz monzodiorite, quartz monzonite, and alkali feldspar granite indicate that they are mainly produced by the partial melting of Neoproterozoic to Mesoproterozoic crustal rocks. The quartz monzodiorites, quartz monzonites, and alkali feldspar granite appeared to derive from a similar silicic magma reservoir because they have comparable crystallization age, zircon trace element variation trend, Sr-, Nd-, and Hf-isotopic compositions, and complementary geochemical compositions. The studied quartz monzodiorites, quartz monzonites, and low silica alkali feldspar granites (SiO 2 < 75 wt%) are deemed a residual cumulate according to their geochemical compositions and textural features (e.g., aggregates of coarse-grained euhedral plagioclase crystals in "glomeroporphyritic aggregates"), whereas the high silica alkali feldspar granites (SiO 2 > 75 wt%) resemble frozen remnants of high silica melts segregated from a crystal mush because they are highly enriched in SiO 2 and depleted in Ba, Sr, and Eu. The MEs hosted in the quartz monzodiorites and quartz monzonites have low SiO 2 and high MgO contents, high initial 87Sr/86Sr ratio and negative ε Nd (t) and ε Hf (t) values, and variable zircon δ18O and ε Hf (t) values. Petrographic observations and geochemical features suggest that they are formed from solidified mafic magmas and generated by the crystal fractionation of mantle-derived hydrous mafic magma with subsequent crustal contamination. Compared with these mafic MEs, the MEs hosted by the alkali feldspar granites have relatively high SiO 2 and low K 2 O contents, indicating that the felsic MEs are generated by crystal fractionation of the parental magma of the mafic MEs. Since abundant MEs occurred in the quartz monzodiorites, quartz monzonites, and alkali feldspar granites, magma recharge may have promoted the extraction and upward percolation of high silicic melts from the compacting crystal-rich mush in the shallow crust. Thus, the chemical and lithological diversity of the granitic plutons in eastern Zhejiang is generated in the upper crust via crystal-melt segregation. Specifically, the quartz monzonites and quartz monzodiorites are formed as residual cumulate, whereas the high silica alkali feldspar granites are generated as frozen remnants of high silicic melts segregated from a compacting crystal mush. More widely, our work suggests that the formation of the highly silicic upper crust in southeastern China is controlled by crystal-melt segregation processes in the shallow crust. • Low silica granites represent the residual silicic cumulates. • High silica granites are extracted from an upper crustal crystal mush. • Chemical diversity of granitic rocks is generated via crystal-melt segregation. • Highly silicic upper crust is formed by crystal-melt segregation processes. [ABSTRACT FROM AUTHOR]

Whole rock geochemistry and Sr-Nd-Hf isotope, zircon U Pb and Hf O isotope data are reported for the early Jurassic gabbro-syenite-alkali-feldspar granite in the inland of South China, in order to investigate their sources, petrogenesis and tectonic implication, and to further trace the rejuvenation of continental crust of South China. The zircon U Pb dating constrains the crystallization ages of 198–195 Ma for syenites, and of about 190 Ma for alkali-feldspar granites and gabbros, respectively. The early Jurassic gabbros have low SiO 2 contents and high MgO, TiO 2 , Cr, V and Ni concentrations, with weak negative Nb and Ta anomalies, variable whole rock initial 87Sr/86Sr ratios (0.7064–0.7117), ε Nd (t) values (−1.5 to +0.6), ε Hf (t) values (−1.6 to +5.7) and zircon ε Hf (t) values (+3.4 to +6.4) and mantle-like δ18O values (+4.9 to +6.2‰). They are inferred to be derived from partial melting of a fertile lithospheric mantle that had been metasomatized by subduction-related fluids/melts, with subsequent limited crustal assimilation and fractional crystallization. The early Jurassic syenites are high-K to shoshonitic rocks with weakly negative Nb and Ta anomalies, strongly negative Sr, P and Ti anomalies, unradiogenic Sr and radiogenic Nd and Hf isotopic compositions (ε Nd (t) up to +5.3 and ε Hf (t) up to +11.5), indicating that they were generated by low-percentage partial melting of an amphibole-bearing lithospheric mantle, with subsequent crustal assimilation and extensive crystal fractionation and/or accumulation. The geochemical features of the early Jurassic K-feldspar granites suggest that they were mainly generated by mixing between mantle-derived mafic magma and crustal-derived felsic magma with extensive feldspar-dominant fractional crystallization. The early Jurassic magmatism was possibly triggered by asthenospheric upwelling following delamination of the flat-subducted Paleo-Pacific plate beneath South China, which provided heat to partial melting of above lithospheric mantle and continental crust. The underplating of depleted mantle-derived magmas changed the ancient crustal structures and modified the components of continental crust, indicating lithospheric rejuvenation during early Jurassic in South China. [Display omitted] • The gabbro-syenite-K-feldspar granite suite in South China was emplaced at 197–189 Ma. • Early Jurassic gabbros and syenites were derived from depleted mantle sources. • Early Jurassic magmatism was caused by delamination of the subducted oceanic plate. • Rejuvenation of the continental crust by magma underplating in South China. [ABSTRACT FROM AUTHOR]

We present new whole rock major and trace element and, Sr–Nd–Hf isotope data for Mesozoic basalts and andesites from the Siziwangqi area, northwestern China, in order to constrain their petrogenesis and regional tectonic implications. The basalts belong to the shoshonitic series and can be subdivided into olivine (Ol-) and plagioclase (Pl-)basalts. The Ol-basalts have moderate MgO contents (5.1–5.5 wt%) and Mg# values (48.7–50.3), and trace element patterns similar to typical ocean island basalts with positive Nb–Ta and negative Pb anomalies. We interpret the Ol-basalts as mantle-derived rocks. The Pl-basalts and andesites are more differentiated than the Ol-basalts, and have low MgO contents (3.9–4.5 and 0.55–3.4 wt%, respectively) and Mg# values (40.3–43.3 and 26.9–47.4; respectively). Trace element (e.g., low Nb/U and Ce/Pb ratios) and Sr–Nd–Hf isotope data for the Pl-basalts and andesites indicate an origin by fractionation and mixing between the mantle-derived magma parental to the Ol-basalts and a crust-derived silicic magma. Crustal melting was induced by the underplating of the mafic parental magmas of the Ol-basalts. Geochemical features of the Ol-basalts, including high SiO 2 , Nb, Ta, Na 2 O/K 2 O, and Fe/Mn and low Rb/Sr and Dy/Yb, are best explained by the vein-plus-wall rock melting of a metasomatized mantle source consisting of amphibole–clinopyroxene-rich veins and surrounding peridotites. The Ol-basalts have enriched Sr–Nd isotopic compositions ((87Sr/86Sr) i = 0.70585–0.70597; ε Nd (t) = −2.8 to −2.6) and decoupled Hf–Nd isotopes with positive ∆ε Hf (t) (+4.5 to +5.0) that are consistent with recent enrichment of the lithosphere by subduction components from the Paleo-Asian oceanic slab. We propose that the Siziwangqi magmatism was related to intra-continental extension of the North China Craton. • New whole rock geochemical data for the Siziwangqi volcanic rocks, western NCC. • Geochemical variations of the rocks caused by magma mixing and fractionation. • A vein-plus-wall rock melting model for the genesis of olivine-basalts. • The Siziwangqi magmatism related to intra-continental extension in the NCC. [ABSTRACT FROM AUTHOR]

Abstract: Whole-rock geochemical and Sr–Nd–Hf isotopic data and in situ zircon U–Pb and Hf–O isotopes have been determined for mafic (gabbro and diorite) and felsic (I- and A-type granites) rocks from the Zhangzhou batholith in southeastern (SE) China, in order to constrain their source and petrogenesis. The batholith consists of gabbro, diorite, granodiorite, monzogranite and alkali feldspar granite, with mafic microgranular enclaves in the monzogranite. Zircon SIMS and LA–ICP–MS U–Pb dating gives consistent emplacement ages of 107–97Ma for these rocks, establishing that the mafic and felsic magmas were coeval. The gabbros and diorites have relatively high MgO contents (up to 5.2wt.%) at low silica concentrations (up to 49.9wt.%), with relatively homogeneous whole-rock initial 87Sr/86Sr ratios (~0.706), negative εNd(t) values of −3.4 to −2.7, chondrite-like εHf(t) values of −0.3 to +0.5, zircon εHf(t) values of −0.8 to +3.2 and δ18O values of +5.0 to +6.1‰, indicating that they were derived by partial melting of an enriched subcontinental lithospheric mantle, coupled with olivine and pyroxene fractionation. The calc-alkaline granodiorites and monzogranites are metaluminous and have relatively high SiO2 and low MgO contents. They have whole-rock initial 87Sr/86Sr ratios of 0.706, εNd(t) ratio of −3.0 to −4.0, εHf(t) values of −2.0 to +0.3 and zircon εHf(t) values of −4.4 to +0.3, with Nd and Hf model ages of about 1.3Ga, indicating that they were mainly derived by partial melting of old continental crustal materials. The alkali feldspar granites have geochemical features similar to A-type granite, with relatively high K2O+Na2O and Nb contents and FeO/MgO and Ga/Al ratios. They have distinct isotopic compositions from the associated mafic rocks, with εNd(t) values of −4.9, εHf(t) values of −3.2 to −3.5, zircon εHf(t) values of −5.1 to +1.0 and δ18O values of +5.1‰ to +6.3‰. They are depleted in Sr, Ba and Eu, indicating that they were mainly derived from partial melting of crustal materials with plagioclase in the residue. Field observations, as well as the petrographic and geochemical data, suggest that the mafic and felsic rocks in the Zhangzhou batholith- were the result of mixing between lithospheric mantle-derived and crustally-derived magmas, coupled with crystal fractionation, in an extensional setting related to Cretaceous subduction of the Paleo-Pacific Plate. [Copyright &y& Elsevier]

Here we report the first set of thallium (Tl) isotope data in alkaline rocks from the North China Craton to constrain the nature of recycled materials in the metasomatized subcontinental lithospheric mantle. Samples from the Hekanzi and Saima alkaline complexes display Tl isotope compositions (ε205Tl) identical to the present‐day upper mantle and continental crust, suggesting that neither the recycled low‐temperature altered oceanic crust nor the pelagic sediments were involved in their sources. The volcanic rocks from the Liaodong‐Jinan region, whose source was previously proposed to contain recycled low‐temperature altered oceanic crust, also display modern mantle‐like Tl isotope composition, suggesting a significant Tl‐loss in the recycled oceanic crust during the subduction due to the dehydration process. Our Tl isotope data provide complementary constraints to the Sr‐Nd‐Hf‐O isotopes on the nature of metasomatic agent in the subcontinental lithospheric mantle. Plain Language Summary: Recycling of crustal materials into Earth's mantle by subduction causes mantle heterogeneities. The sources of some alkaline rocks contain recycled crustal materials. Pelagic sediments, low‐temperature altered oceanic crust, and continental crust have sharp differences in thallium isotope compositions. Combined with Sr‐Nd‐Hf‐O isotopes, whole‐rock Tl isotopes place a better constraint on the metasomatic sources. Key Points: Thallium isotope compositions of the alkaline rocks were analyzed to track crustal recycling in the subcontinental lithospheric mantleThallium isotope suggested that low‐temperature altered oceanic crust and pelagic sediments were not involved in the investigated sourcesThe O‐Nd‐Hf‐Tl isotope data for the Liaodong‐Jinan volcanics reveal a significant Tl‐loss in the subducted slab during dehydration process [ABSTRACT FROM AUTHOR]

Abstract: Major and trace element, whole rock Sr‐, Nd‐and Hf‐isotopes and zircon U–Pb age and Hf–O isotope data have been determined for mafic to felsic intrusive rocks from the Late Triassic Mayihe (MYH), Longtou–Chaxinzi–Xiaoweishahe (LCX) and Nankouqian–Xidadingzi (NX) intrusions in the northern Liaodong Peninsula, NE China, in order to investigate their sources and petrogenesis related to decrationization of the North China Craton. The rocks include clinopyroxene diorite, monzodiorite, quartz diorite, granodiorite, monzogranite and mafic microgranular enclaves. Laser ablation inductively coupled plasma mass spectrometry (LA–ICPMS) and secondary ion mass spectrometer (SIMS) U–Pb analyses of zircon from MYH, LXC to NX intrusions yield Late Triassic ages of 224–218Ma, establishing that the mafic and felsic magmas were coeval. The clinopyroxene diorites from the MYH pluton have high MgO concentrations at low silica contents, with positive whole rock εNd(t) (up to +3.8) and εHf(t) (up to +6.2) and zircon εHf(t) values and some mantle-like δ18O values. They are enriched in large ion lithophile (LILEs) and light rare earth elements (LREEs) and depleted in high field strength elements (HFSEs), which can be explained as melts derived from a depleted mantle, with some subsequent crustal contamination. However, the diorites from the LXC and NX intrusions are high‐K rocks and have high MgO concentrations and mantle-like δ18O values, but with negative whole rock εNd(t) (−12.9 to −7.6) and εHf(t) (−14.0 to −5.6) and zircon εHf(t) values, distinct from those of MYH pyroxene diorites, indicating that their parental magmas were derived from partial melting of an ancient lithospheric mantle. The granitoids from three plutons have high SiO2 contents and low MgO concentrations, suggesting they were mainly derived from crustal sources. However, the MYH monzogranite and granodiorite have positive whole rock εNd(t) and εHf(t) (up to +3.0) and zircon εHf(t) values, indicating a juvenile crustal source, whereas, the LXC and NX granitoids have strong negative and variable whole rock εNd(t) and εHf(t) and zircon εHf(t) values, indicating that they were derived from partial melting of ancient lower crustal materials with involvement of mantle components. Field observations, geochronology, geochemistry, Sr–Nd–Hf isotopic and zircon Hf–O isotopic compositions point to a complex petrogenesis, where mantle- and crust-derived magma mixing was coupled with crystal fractionation, thus explaining the genetic link between mafic and felsic rocks. Identification of four components, i.e., depleted and enriched mantle and juvenile and ancient crust in the Late Triassic magmatism in the northern Liaodong Peninsula suggests a strong mantle–crust interaction process related to decratonization of the North China Craton. [Copyright &y& Elsevier]

Abstract: Whole-rock major and trace element and Sr-, Nd- and Hf-isotope data, together with zircon U–Pb and Hf-isotope data, are reported for three alkaline intrusions (Liangjia, Jianfang and Hekanzi) in the Yanshan Fold and Thrust Belt in the northeastern North China Craton, in order to investigate their sources, petrogenesis and tectonic implications. The Liangjia and Jianfang plutons are mainly composed of medium-grained quartz syenites, whereas, the Hekanzi complex consists of nepheline-bearing pyroxene-biotite syenites. Zircon U–Pb dating gives emplacement ages of 254–246Ma for the Liangjia and Jianfang silica-saturated syenites and 226–224Ma for the Hekanzi silica-undersaturated syenites. The Late Permian silica-saturated alkaline rocks have high silica contents (SiO2 =69.2–75.7wt.%) and low MgO (0.04–0.47wt.%) concentrations, and are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) but with negative Eu, Ba and Sr anomalies and depletion in high field strength elements (HFSEs), with significant negative Nb, Ta, P and Ti anomalies. Geochemical data and Sr-, Nd and Hf-isotopic compositions indicate that they were mainly derived from partial melting of lower crustal materials with extensive pyroxene and plagioclase fractionation. The Triassic silica-undersaturated syenites have relatively high MgO abundances (up to 5.3wt.%) at basic to intermediate silica contents. They are enriched in LREE and LILE and depleted in HREE and HFSE, with negative Nb, Ta and Ti anomalies. They have relatively low initial 87Sr/86Sr ratios and relatively negative whole rock εNd(t) and εHf(t) values and zircon εHf(t) values. All these geochemical features indicate that they were the result of crustal assimilation and fractional crystallization of a mafic magma derived from an amphibole-clinopyroxene-rich lithospheric mantle via small degree partial melting. Based on the regional geology, the Late Permian syenites would form in a post-collisional extension setting, whereas, the Triassic syenites were most likely generated in an intraplate extensional setting, providing time constraints on the geodynamic transition from post-orogenic to intra-plate extension. [Copyright &y& Elsevier]

Abstract: Mineral compositions, clinopyroxene trace-element and Sr–Nd–Hf isotopic compositions, whole‐rock major‐element and Platinum Group Element (PGE) contents, and Re–Os isotopes of peridotite xenoliths in the Cenozoic alkali basalts from Abaga, Inner Mongolia (China) help to constrain the nature of the subcontinental lithospheric mantle beneath the eastern part of the Central Asian Orogenic Belt. The mantle xenoliths are mainly spinel lherzolites, with minor olivine websterite and spinel harzburgite. Clinopyroxene–orthopyroxene equilibration temperatures are higher than 840°C. An olivine websterite (sample A2-2) has the lowest MgO and highest Al2O3, CaO and TiO2 contents, whereas a harzburgite (sample A2-1) has the highest MgO and low Al2O3, CaO and TiO2 contents. The spinel lherzolites have major-element concentrations transitional between the harzburgites and websterites. According to the chemical characteristics and Sr–Nd–Hf isotopic compositions of clinopyroxenes, two groups of spinel lherzolites can be identified. Group 1 spinel lherzolites are moderately depleted in Light Rare Earth Elements (LREEs) and with flat Heavy Rare Earth Element (HREE) patterns, indicating a low degree of melt extraction and minimal metasomatism. They have clinopyroxenes with homogeneous 87Sr/86Sr (0.7030−0.7033), 143Nd/144Nd (0.5131–0.5132) and 176Hf/177Hf (0.2834–0.2835) ratios. They have flat chondrite-normalized PGE patterns and radiogenic 187Os/188Os ratios (0.1232–0.1256), within the range of modern convective mantle. Group 2 spinel lherzolites have low HREE contents with variable LREE concentrations, suggesting complex melt extraction and mantle metasomatism processes. They have relatively heterogeneous Sr–Nd–Hf isotopic compositions with 87Sr/86Sr of 0.7040–0.7054, εNd values of +6.1 to +12.1 and εHf values of +19.2 to +474. The Group 2 spinel lherzolites have flat chondrite-normalized PGE patterns and radiogenic 187Os/188Os ratios (0.1231–0.1252). The websterite has a magmatic origin with weakly decoupled Nd–Hf isotopes and the lowest 187Os/188Os ratio of 0.1219. The harzburgite has a 187Os/188Os ratio of 0.1280 similar to that of the modern convective mantle. All these characteristics indicate that the Group 2 spinel lherzolites represent ancient lithospheric mantle that experienced high‐degree melt extraction and subsequent extensive silicate metasomatism. Thus, it is proposed that the SCLM beneath the Abaga region of the eastern Central Asian Orogenic Belt (CAOB) is mostly juvenile with minor relicts of old depleted lithospheric mantle, which cooled from near-adiabatic to near-lithospheric temperatures to form new lithospheric mantle during the formation of the eastern CAOB. [Copyright &y& Elsevier]

Abstract: The North China Craton (NCC) is the typical example of destruction of an ancient craton. However, the destruction mechanism and geodynamic controlling factors still remain enigmatic due to controversy on the timing of destruction, which is the key to understanding the destruction processes. Based on temporal and spatial distributions of the igneous rocks, and their sources and tectonic settings, it is recognized that six stages of tectono-magmatism occurred in the NCC during the Phanerozoic, i.e., Carboniferous to Early Permian, Late Permian to Middle Triassic, Late Triassic, Jurassic, Early Cretaceous and Cenozoic. Among them, Cenozoic magmatism mainly consists of alkali basalts and is found only occasionally in the eastern NCC. The first four stages of magmatism and tectonism, related to the southward subduction of the Paleo-Asian plate and the assembly of Sino-Korean and Yangtze cratons, are locally distributed in limited parts of the NCC, reflecting a multiple stage modification of the NCC from the Late Carboniferous to Jurassic. However, the intensive development of Early Cretaceous magmatism, extensional deformation and associated gold mineralization, with significant continental crustal growth, indicate that the eastern NCC was destroyed during this time period. This destruction was the result of Paleo-Pacific subduction beneath the eastern Asian continent, with lithospheric removal and/or replacement of an ancient cratonic lithosphere by a juvenile oceanic lithosphere. [Copyright &y& Elsevier]

The Chehugou granite-hosted molybdenum deposit is typical of the Xilamulun metallogenic belt, which is an important Mo–Ag–Pb–Zn producer in China. A combination of major and trace element, Sr and Nd isotope, and zircon U–Pb isotopic data are reported for the Chehugou batholith to constrain its petrogenesis and Mo mineralization. The zircon SIMS U–Pb dating yields mean ages of 384.7 ± 4.0 Ma and 373.1 ± 5.9 Ma for monzogranite and syenogranite and 265.6 ± 3.5 Ma and 245.1 ± 4.4 Ma for syenogranite porphyry and granite porphyry, respectively. The Devonian granites are calc-alkaline with K2O/Na2O ratios of 0.44–0.52, the Permian granites are alkali-calcic with K2O/Na2O ratios of 1.13–1.25, and the Triassic granites are calc-alkaline and alkali-calcic rocks with K2O/Na2O ratios of 0.78–1.63. They are all enriched in large-ion lithophile elements (LILEs) and depleted in high-field-strength elements (HFSEs) with negative Nb and Ta anomalies in primitive mantle-normalized trace element diagrams. They have relatively high Sr (189–1256 ppm) and low Y (3.87–5.43 ppm) concentrations. The Devonian granites have relatively high initial Sr isotope ratios of 0.7100–0.7126, negative ɛNd(t) values of −12.3 to −12.4 and 206Pb/204Pb ratios of 16.46–17.50. In contrast, the Permian and Triassic granitoids have relatively low initial 87Sr/86Sr ratios (0.7048–0.7074), negative ɛNd(t) values of −10.1 to −13.1 and 206Pb/204Pb ratios of 17.23–17.51. These geochemical features suggest that the Devonian, Permian and Triassic Chehugou granitoids were derived from ancient, garnet-bearing crustal rocks related to subduction of the Palaeo-Asian Ocean and subsequent continent–continent collision between the North China and Siberian plates. [ABSTRACT FROM AUTHOR]

[Display omitted] • Collision of the Bainaimiao island arc and North China Craton took place in the late Silurian. • The Inner Mongolia Paleo-uplift underwent rapid uplift during the Carboniferous. • Initial subduction of the Paleo-Asian Ocean was triggered by an arc–continent collision. The driving mechanisms for initial oceanic subduction beneath a passive continental margin remain unclear. The Paleozoic convergence history between the North China Craton (NCC) and the Paleo-Asian Ocean provides an ideal opportunity to investigate the driving mechanisms of the onset of oceanic subduction. Our detrital zircon U–Pb dating results yield Middle Devonian to Permian ages (391–273 Ma) in Paleozoic strata within China's Aoji region, specifically in the Bainaimiao arc belt situated between the NCC and Central Asian Orogenic Belt (CAOB). Detrital zircon age spectra, ε Hf (t) values, and two-stage model ages of the Devonian to Permian sediments suggest zircon contributions from both the NCC and CAOB. Combined with data from various regions along the Bainaimiao arc belt, findings suggest that the Bainaimiao island arc was accreted to the northern margin of the NCC through arc–continent collision during the late Silurian, rendering the NCC margin passive until the end-Devonian. At this point, southward subduction in the Paleo-Asian Ocean beneath the NCC commenced and continued into the Permian, transforming the northern margin of the NCC from passive to active. This initial subduction (ca. 359 Ma) in the Paleo-Asian Ocean resulted from collision-induced magmatism and deformation due to the protracted convergence and also led to a reversal in subduction polarity. Subsequently, in response to Paleo-Asian Ocean subduction, the northern margin of the NCC underwent rapid uplift during the Carboniferous, which led to widespread exposure of the NCC basement rocks in the late Carboniferous. [ABSTRACT FROM AUTHOR]

The reworking of continental crust in collision zones is a key process in the chemical maturation of crustal rocks. However, the mechanisms that cause crustal reworking remain highly controversial. The compositionally diverse magmatic rocks along the Lhasa–Qiangtang collision zone provide a favorable opportunity for studying the mechanism of crustal reworking and maturation in continental collision zones. Here we report zircon U Pb ages and Hf isotopes, mineral major elements, and whole-rock geochemistry and Sr Nd isotopes for the Momu intrusive complex in the Lhasa–Qiangtang collision zone, central Tibet. Zircon U Pb ages reveal that the intrusive complex formed during the late Early Cretaceous (115–113 Ma). Diorites from the intrusive complex have high Mg# values (49.7–51.2) and initial 87Sr/86Sr ratios (0.7082 to 0.7083), and low ε Nd (t) values (−7.3 to −6.9), with negative to slight positive zircon ε Hf (t) values (−3.8 to +0.8), suggesting that these rocks were likely generated by the partial melting of the enriched lithospheric mantle. Granodiorites from the intrusive complex have high SiO 2 (64.4–67.9 wt%) and Al 2 O 3 (14.8–16.1 wt%) and low MgO (1.4–1.8 wt%) contents. These rocks are also characterized by high initial 87Sr/86Sr ratios (0.7091–0.7098) and whole-rock negative ε Nd (t) (−9.9 to −8.4) and zircon ε Hf (t) (−7.9 to −2.2) values. The associated granites have the highest SiO 2 (68.7–71.5 wt%) contents among the intrusive complex rocks, high initial 87Sr/86Sr (0.7089–0.7093) ratios, and negative whole-rock ε Nd (t) (−10.1 to −7.7) and zircon ε Hf (t) (−5.3 to −0.2) values. These geochemical characteristics indicate that the granodiorites were most likely derived from the partial melting of ancient continental crust and that the coeval granites were formed by the fractional crystallization of granodioritic magmas. Integrating our new results with data for the coeval magmatic rocks of the Lhasa–Qiangtang collision zone, we suggest that the Momu intrusive complex formed in a post-collisional slab breakoff setting. Asthenosphere upwelling caused by slab breakoff could have provided a substantial source of heat for crustal reworking, which gradually contributed to the maturation of continental crust in the Lhasa–Qiangtang collision zone. • The Momu intrusive complex of central Tibet formed at 115–113 Ma. • The diorites were derived by partial melting of modified lithospheric mantle. • The granodiorites and granites formed via partial melting of ancient crust. • Crustal maturation occurred by collision of the Lhasa and Qiangtang terranes. [ABSTRACT FROM AUTHOR]

Abstract: Simultaneous in situ U–Pb dating, trace element and Hf isotopic analyses have been carried out on detrital zircons obtained from sandstones in the Neoproterozoic Jing’eryu Formation from the Eastern Block, North China Craton (NCC), with the aim of constraining the ages of magmatic and metamorphic events and hence the Precambrian crustal evolution of the NCC. Two groups of zircons, i.e., magmatic and metamorphic in origin, have been identified based on cathodoluminescence images, zircon Ti-temperatures and Th/U ratios. Zircon U–Pb dating shows two main magmatic events with ages of 2.55–2.47Ga and 1.80–1.70Ga, and four metamorphic events, with ages of 2.51–2.48Ga, 1.96–1.90Ga, 1.87–1.85Ga and ∼1.80Ga in the NCC. No zircons with ages of ∼3.8Ga have been identified in this study, indicating either these were covered at the time of deposition or the limited presence of 3.8Ga rocks in the NCC. The Hf isotopic data show the ∼2.5Ga magmatic zircons have variable ɛ Hf(t) values, including both positive and negative values and with crustal model ages of 2.7–2.9Ga, which can be interpreted to indicate mixed sources for their parental rocks, i.e., ancient crust (3.8Ga or 3.3Ga) and depleted mantle, implying significant continental crustal growth at ∼2.5Ga. However, Paleoproterozoic magmatic zircons all have negative ɛ Hf(t) and Archean Hf model ages, suggesting that their parental rocks were formed from recycled Archean materials. The widespread ∼2.5Ga metamorphism in the Eastern Block, coupled with extensive ∼2.5Ga magmatism and crustal growth, are consistent with a mantle plume beneath the Eastern Block of the NCC during the Neoarchean. Whereas, a progressive increase in ∼1.85Ga metamorphic zircon westward across the Eastern Block toward the Trans-North China orogen is best explained by collision between the Eastern and Western blocks at this time. [Copyright &y& Elsevier]

Abstract: It is well accepted that the North China Craton formed by assembly of the Eastern and Western blocks along the Trans-North China Orogen, with cratonization in the Paleoproterozoic (∼1.85Ma). However, there is controversy about the formation of the Eastern and Western blocks themselves, especially the timing of cratonization of the Eastern Block. The Jiao-Liao-Ji orogenic belt is the most important Paleoproterozoic Orogenic belt in the Eastern Block and consists mainly of the North and South Liaohe Groups and the Liaoji Granitoids. The timing of metamorphism of the Liaohe Group is the key to understanding the evolution of the Eastern Block of the North China Craton. Because the isotope systematics of metamorphic minerals can be used to date parts of the prograde thermal histories of metamorphic belts, dating of minerals, such as garnet and staurolite has the distinct advantage that time information can be related directly to the pressure–temperature-deformation history recorded by the same mineral. In this paper we present results of precise 207Pb/206Pb stepwise-leaching (PbSL) dating of garnet and staurolite from the metasedimentary rocks of the south Liaohe Group. The primitive Pb and radiogenic Pb are selectively extracted from garnet and straurolite by leach steps and determined by multiple collector (MC-) ICP-MS. The garnet and staurolite record two groups of 207Pb/206Pb ages, at 1.93–1.91Ga and ∼1.86Ga, respectively. These constrain the time of peak metamorphism of the Liaohe Group during collision between the Longgang Block in the north and the Liaonan (Nangrim) Block in the south and a subsequent post-collisional event, respectively. Our data for the South Liaohe Group and previously published data for the Liaoji Granite, combined with key lithological, structural and metamorphic information, indicate that the cratonization of the Eastern Block of the North China Craton occurred at 1.93–1.91Ga. [Copyright &y& Elsevier]