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The Moon's mare volcanism predominantly occurs within the Procellarum KREEP Terrane (PKT), which is widely thought to be associated with KREEP components within the lunar interior. The Chang'e-5 (CE-5) mission sampled a young (2 Ga) mare basalt Em4/P58 unit of northern Oceanus Procellarum. The geochemistry of the CE-5 mare basalt enables assessment of mantle source compositions which are essential to understand the thermo-chemical mechanism for prolonged volcanism during secular cooling of the Moon. Geochemical compositions of the CE-5 bulk soil, breccias, and basalt clasts from various depths within the drill core consistently display high concentrations of incompatible trace elements (ITE: ∼ 0.3 × high-K KREEP; ∼ 5 μg/g Th) with KREEP-like inter-element ratios, for example for La/Sm, Nb/Ta, and Zr/Y. Exotic impact ejecta, extensive magma differentiation (<70 % fractional crystallization) and significant assimilation of KREEP materials during magma transit and eruption cannot account for the ITE contents and ratios or radiogenic isotope compositions (e.g., εNd initial of + 8 to + 9 and εHf initial of + 40 to + 46) of the CE-5 basalts; instead, partial melting of their mantle source played a dominant role. The Chang'e-5 basalt is a chemically evolved low-Ti mare basalt (Mg# of ∼ 34) with enriched KREEP-like ITE compositions but high long-term time-integrated Sm/Nd and Lu/Hf ratios, which represent a hitherto unsampled type of mare basalt. It formed by melting of an augite-rich mantle source (late-stage magma ocean cumulates containing > 30–60 % augite, and little or no ilmenite), with a small amount of late-stage interstitial melt that resembles KREEP (∼1–1.5 modal %, equivalent to 0.2–0.3 μg/g Th in the mantle source). The voluminous mare basalts making up the Em4/P58 unit (>1500 km3) provide compelling evidence for large-scale, ITE enriched young mare magmatism within Oceanus Procellarum. In combination with remote sensing data and with the unique Th-rich Apollo 12 basalt fragment 12032,366–18 (impact ejecta likely from Oceanus Procellarum), this implies that significant portions of the FeO- and Th-rich mare regions of the western PKT may also have formed in a similar way. [ABSTRACT FROM AUTHOR]

Silver (Ag) is a trace metal element in geological rocks and accurate determination of its abundance is very challenging given significant oxide and hydroxide interferences from Zr, Nb, Mo, and Y. Here, we developed a valid method based on inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS), in which NH3 was used as the reaction gas, to determine the Ag content in geological samples. The additional quadrupole analyzer located in front of the collision/reaction cell ensured a simple and controllable reaction in the cell. The first quadrupole (Q1) was set to m/z 107 and 109 to allow Ag+ and its interferences to enter the reaction cell. Ag+ partially reacted with NH3, forming Ag+ and Ag(NH3)2+ as the main products; while the major interferences, ZrO+ and NbO+, reacted strongly and were converted to ZrO(NH3)4+, ZrO(NH3)5+, and NbO(NH(NH3)3)+, respectively, and thus no longer affected the measurement of Ag. Consequently, the Ag signals could be detected by both "on-mass" and "mass-shift" methods, where the m/z of Q1–Q2 were 107–107, 109–109 and 107–141, 109–143, respectively. Under the optimized NH3 flow rate (3.5 ml min−1), the interference levels of the matrix solution (0.3 μg ml−1 Zr and Mo, 0.2 μg ml−1 Zn, 0.1 μg ml−1 Y and Nb, and 0.05 μg ml−1 Ga) in four Q1–Q2 mass pairs were negligible and comparable to background signals, and the limits of detection of geological samples were <0.53 ng g−1. The Ag content of 19 geological reference materials was reported using the proposed ICP-MS/MS method, and the results were consistent with isotope dilution-ICP-MS values. Thus, the proposed method has great potential for the accurate, direct, and high-throughput measurement of Ag in geological samples. [ABSTRACT FROM AUTHOR]

The origin of crystal‐scale Zr isotopic variation remains enigmatic. Here, we report high‐precision Zr isotopic compositions of thin‐sectioned and hand‐picked zircon crystals from monzodiorites and K‐feldspar granites, which represent the mafic and felsic products of a differentiating magma. Our results reveal that zircons from both rock associations are dominated by a rim‐ward increase in the 94Zr/90Zr ratio and accompanied by ∼1‰ intracrystalline and intercrystalline variations, confirming the preferential incorporation of light Zr isotopes and thus kinetic isotopic fractionation during zircon growth. Notably, zircons enclosed by K‐feldspar in monzodiorites generally yield lower 94Zr/90Zr and higher Zr/Hf ratios than that of separated crystals, while in K‐feldspar granites, tiny zircons intergrown with apatite obtain higher 94Zr/90Zr but lower Zr/Hf ratios relative to that of sizable separates. The diversity in petrographic textures and sizes of zircon crystals, corresponding to their crystallization sequence, potentially accounts for some of the heterogeneity of Zr isotopes at the mineral scale. Plain Language Summary: Stable Zr isotopes of zircon have been proposed as a new and promising tracer for magmatic differentiation. However, how significant heterogeneity of Zr isotopes developed at the mineral scale in an evolving magma is highly debatable. Ab initio simulation calculations, experiments, and natural sampling have suggested that kinetic rather than equilibrium effect plays a dominant role in fractionating Zr isotopes during zircon crystallization, whereas how kinetic effect links with the textural contexts of zircons is not directly constrained. Here, petrographic and geochemical constraints on zircon crystals from the mafic and felsic products of a differentiating magma are provided, which reveal that earlier crystallized domains or crystals are isotopically lighter in Zr than the later ones. Besides, the δ94Zr values of zircon crystals, displaying intra‐grain and inter‐grain variations beyond ∼1‰, correlate well with Zr/Hf ratios that reflect diverse stages of magma differentiation, irrespective of the compositions of host rocks. These findings indicate that crystal‐scale elemental and stable isotopic variations (e.g., Zr isotopes in zircon) could be ascribed to the sequential crystallization of targeting minerals. Key Points: Early‐formed zircon crystals or domains are isotopically lighter in Zr than those crystallized late in both mafic and felsic rocksDiversity in textural occurrences and sizes of zircons potentially explain the Zr isotopic heterogeneity at the mineral scaleGeochemical information extracted from separated minerals does not always reflect the nature of primitive magma [ABSTRACT FROM AUTHOR]

Lunar soil is a fine mixture of local rocks and exotic components. The bulk-rock chemical composition of the newly returned Chang'E-5 (CE-5) lunar soil was studied to understand its chemical homogeneity, exotic additions, and origin of landing site basalts. Concentrations of 48 major and trace elements, including many low-concentration volatile and siderophile elements, of two batches of the scooped CE-5 soil samples were simultaneously obtained by inductively coupled plasma mass spectrometry (ICP-MS) with minimal sample consumption. Their major and trace elemental compositions (except for Ni) are uniform at milligram levels (2–4 mg), matching measured compositions of basaltic glasses and estimates based on mineral modal abundances of basaltic fragments. This result indicates that the exotic highland and KREEP (K, rare earth elements, and P-rich) materials are very low (<5%) and the bulk chemical composition (except for Ni) of the CE-5 soil can be used to represent the underlying mare basalt. The elevated Ni concentrations reflect the addition of about 1 wt% meteoritic materials, which would not influence the other bulk composition except for some highly siderophile trace elements such as Ir. The CE-5 soil, which is overall the same as the underlying basalt in composition, displays low Mg# (34), high FeO (22.7 wt%), intermediate TiO 2 (5.12 wt%), and high Th (5.14 µg/g) concentrations. The composition is distinct from basalts and soils returned by the Apollo and Luna missions, however, the depletion of volatile or siderophile elements such as K, Rb, Mo, and W in their mantle sources is comparable. The incompatible lithophile trace element concentrations (e.g., Ba, Rb, Th, U, Nb, Ta, Zr, Hf, and REE) of the CE-5 basalts are moderately high and their pattern mimics high-K KREEP. The pattern of these trace elements with K, Th, U, Nb, and Ta anomalies of the CE-5 basalts cannot be explained by the partial melting and crystallization of olivine, pyroxene, and plagioclase. Thus, the mantle source of the CE-5 landing site mare basalt could have contained KREEP components, likely as trapped interstitial melts. To reconcile these observations with the initial unradiogenic Sr and radiogenic Nd isotopic compositions of the CE-5 basalts, clinopyroxene characterized by low Rb/Sr and high Sm/Nd ratios could be one of the main minerals in the KREEP-bearing mantle source. Consequently, we propose that the CE-5 landing site mare basalts very likely originated from partial melting of a shallow and clinopyroxene-rich (relative to olivine and orthopyroxene) upper mantle cumulate with a small fraction (about 1–1.5 %) of KREEP-like materials. [ABSTRACT FROM AUTHOR]

The Permian basalts in the Central Asian Orogenic Belt (CAOB) are crucial for constraining the closure of the Paleo-Asian Ocean. However, the origin of these basalts is still under discussion. Here, we present comprehensive bulk-rock geochemical, Sr−Nd−Pb−Hf isotopic, and zircon U−Pb−Lu−Hf isotopic data of the Liuyuan basalts and coexisting gabbros, which are located in the Beishan Orogen in the southern CAOB, to constrain their emplacement setting and tectonic implications. Our new gabbro ages of ca. 288–294 Ma are interpreted to represent the formation time of the Liuyuan basaltic belt. The Liuyuan basalts show MORB-like rare earth element (REE) patterns and bulk-rock εHr(t) and εNd(t) values of 11.0–15.4 and 4.6–9.2, respectively, suggesting an origination mainly from a depleted mantle source. However, positive Pb anomalies, Nb−Ta depletions, and high Th/Yb ratios as well as evolved Sr−Nd−Pb−Hf isotopic compositions of some samples indicate variable continental crustal contribution. According to the covariation of Pb anomalies (Pb* =2×PbN/(CeN+PrN)) with Sr−Nd−Pb−Hf isotopic compositions, we speculate that parent magma of the Liuyuan basalt was contaminated by continental crustal materials during the eruption rather than having been generated from an enriched mantle source. As revealed by mixing modelling, the Liuyuan basaltic magmas would require a minor (<10%) upper continental crustal assimilation to explain the enriched trace elemental and radiogenic Sr−Nd−Pb−Hf isotopic signatures. Consequently, the Liuyuan basaltic belt is believed to have been generated in a continental extensional environment instead of an oceanic setting and does not constitute a Permian ophiolitic suture zone as previously suggested, since the Paleo-Asian Ocean was already closed in the southern Beishan Orogen in the Early Permian. [ABSTRACT FROM AUTHOR]

Carbonate melts play an essential role in the deep carbon cycle between Earth's surface and interior. Most previous studies proposed that the source of carbonate melt resulted from the recycling of subducted oceanic slabs. Recent studies on orogenic rocks show that continental subduction may also deliver carbonate sediments into the deep mantle. However, these rocks usually have undergone complex geological processes and strong modifications during exhumation. Here we report evidence of continental subduction-triggered carbonate metasomatism of the lithospheric mantle from a suite of mantle xenoliths entrained by the Cenozoic Qixia basalts from the southeastern North China Craton (NCC). Both petrological (the same variation of mineral modal content as in carbonate melt-peridotite reaction experiments, the replacement of olivine and orthopyroxene by clinopyroxene, and the presence of apatite) and geochemical (high Ca/Al, La N /Yb N , and low Ti/Eu ratios in clinopyroxene) evidence show mantle xenoliths record obvious signals of carbonated silicate melt metasomatism. The high 87Sr/86Sr ratios of 0.7094–0.7100 in clinopyroxene of these xenoliths indicate that the carbonated silicate melt was derived from subducted continental crust rather than oceanic crust and asthenosphere mantle. The carbonated silicate melt could be produced by carbonate dissolution during continental subduction or resulted from the partial melting of the diapiric carbonate-rich sediments. An estimation suggests a carbon input flux of 14 ± 7 Mt yr−1 associated with the Yangtze continental subduction, approximately 20–50% of the estimated total carbon input flux of the global oceanic subduction. It is therefore important to include the contribution of continental subduction when deciphering deep carbon recycling and its effects. • Qixia mantle xenoliths from North China Craton suffered carbonate metasomatism. • Carbonated silicate melt was derived from the subducted Yangtze Block. • Continental subduction plays an essential role in the deep carbon cycle. • Input flux of 14 ± 7 Mt. C yr−1 is estimated during Yangtze continental subduction. [ABSTRACT FROM AUTHOR]

Formation of ultramafic cumulate rocks at the arc root serves as a key process to understanding the deep evolution of arc magma and crustal growth. However, the arc root cumulates are easy to delaminate due to their high density, making limited field exposure. Here, we conducted comprehensive petrographic observations and geochemical analysis of typical ultramafic rocks (peridotites and pyroxenites) in an ophiolitic mélange from the central Beishan orogenic belt in the southern Central Asian Orogenic Belt (CAOB). Petrographic evidence shows that these rocks exhibit characteristic adcumulate and mesocumulate textures with intercumulus minerals such as olivine, orthopyroxene, and clinopyroxene. The mineral characteristics of ultramafic rocks, including olivine and orthopyroxene with lower NiO (0.10–0.33 wt% and 0.03–0.09 wt%, respectively) and Mg# (81–87 and 86–88, respectively), clinopyroxene with higher CaO (19.0–24.7 wt%), and spinel with lower Mg# (0–49), are distinct from those of mantle rocks but resemble cumulates. Both whole rock and calculated equilibrium melt exhibit the compositions of island arc magma characterized by enrichment in large ion lithophile elements (e.g., Cs, U, Pb, and Sr) and depletion in high field strength elements (e.g., Nb, Ta, Zr, Hf, and Ti). The covariation of high Mg# and low SiO 2 in whole rocks is akin to typical arc root cumulates from classic island arcs (e.g., Kohistan and Talkeetna). The positive zircon ε Hf (t) values (+13 to +16) and calculated crystallization pressure of 0.9–1.1 GPa (∼30–40 km) support the formation of ultramafic cumulates in a juvenile island arc setting. These findings imply that most ultramafic rocks in the central Beishan orogenic belt are arc root cumulates instead of the mantle portion of an ophiolitic mélange. Fractional crystallization models suggest that arc root cumulate formation may have influenced the evolution of intermediate-felsic rocks in this area, and that the differentiation of hydrous arc magma played a crucial role in large-scale crustal growth in the southern CAOB during the early Paleozoic. • Ultramafic rocks show cumulate textures and island arc geochemical features. • These rocks are arc-root cumulates, not the mantle portion of an ophiolitic complex. • The crystallization of cumulates promotes intermediate-felsic rock formation. • Hydrous arc magma differentiation has a critical role in crustal growth in the CAOB. [ABSTRACT FROM AUTHOR]

Southeast Asia plays a key role in the evolution of the eastern Tethys, which is characterized by accretion and amalgamation of numerous terranes since early Paleozoic. In the present study, an early Paleozoic granitoid sequence from the Kontum massif in the central Indochina block was investigated to reveal the early Paleozoic accretionary orogenesis of the eastern Tethys. Early Paleozoic Kontum granitoids include diorites and granites. Early Ordovician (485–473 Ma) Ben Giang diorites show high Mg#, Cr and Ni contents, and negative Nb-Ta and positive Pb anomalies as well as positive zircon ɛHf(t) values (+6.2 to +10), probably reflecting the melting of a metasomatized mantle wedge. Late Ordovician (457–453 Ma) Dien Binh hornblende-bearing diorites and granites exhibit low Mg#, Cr and Ni contents, and negative Nb-Ta and positive Pb anomalies as well as negative zircon ɛHf(t) values (−8.7 to −4.2), which is interpreted to reflect the reworking of ancient continental mafic crust during subduction. In contrast, the Silurian (422 Ma) Dai Loc muscovite-bearing granites are characterized by relatively high A/CNK and heavy rare earth element contents, and a negative Eu anomaly, corresponding to a typical S-type granite affinity. Their negative zircon ɛHf(t) values (−6.0 to +0.6) suggest that a petrogenesis linked to reworking of crustal sediments. In combination with the widespread occurrence of coeval high-pressure metamorphism, we suggest that an advancing accretionary orogenesis was responsible for the generation of the early Paleozoic magmatic arc in the Kontum massif. Such magmatic arc systems dominated the early Paleozoic evolution of the northern Gondwana margin during the subduction of the Proto-Tethys. [ABSTRACT FROM AUTHOR]

Oxide interference correction plays a vital role in the accurate determination of trace element compositions of geological samples by inductively coupled plasma-mass spectrometry (ICP-MS). In this study, we found that the oxide production is mainly controlled by the gas flow of the ICP-MS and a constant oxide correction factor (OCF) can be measured during a routine analysis. Thus, we can obtain the oxide production by just investigating the gas flow for a fixed ICP-MS system with monitoring of OCF. Si, Ba and LREE oxide interferences on the Sc, Eu and Gd of four geological standard samples GSP-2, JP-1, GBW03112 and GBW03113 were corrected by such method and the results were in good agreement with the recommended values. Therefore, the present study provides a simple and fast correction method for the oxide interferences of the geological samples during the routine analyses. Furthermore, a Microsoft Excel spreadsheet template integrating the correction equations was developed in an in-house software (ICPMSDataCal) for effective calibration. [ABSTRACT FROM AUTHOR]

• ∼1.4 Ga juvenile magmatism occurs in most microcontinents in the southern CAOB. • The microcontinents show distinct evolution compared to nearby cratons at ∼1.4 Ga. • Mesoproterozoic magmatism records geodynamic transition along the margin of Nuna. The southern Central Asian Orogenic Belt contains numerous microcontinents including the Kazakhstan-Yili block, Central Tianshan Arc and Junggar block in the west, the Erguna, Xing'an, Songliao and Jiamusi-Khanka blocks in the east, bridging by the Tuva-Mongolia block, Beishan Orogenic Belt and Alax block in the central region. New geochemical and geochronological data from the microcontinental blocks within the southern Beishan Orogenic Belt provide new insight into the Precambrian crustal evolution of this region. Five granitoids from the Jiujing region yielded igneous zircon 206Pb/238U ages of 1450–1401 Ma, and zircon xenocrysts from late Paleozoic plutons in the Jiujing, Qiaowan, and Shibandun regions have 206Pb/238U ages that also cluster at ∼1.4 Ga. Those data suggest that crust of this age is widespread beneath the southern Beishan Orogenic Belt. The ∼1.4 Ga zircons display depleted Hf isotopic signatures (ε Hf(t) = 2.0–11.1) and show relatively young two-stage Hf model ages (1.9–1.4 Ga), indicating rapid reworking of juvenile mantle-derived materials. Integrating these results with similar geochronological data from the Kyrgyz North Tianshan, Yili block, Central Tianshan Arc, northern Alxa block and Xilinhot block, we propose that the CAOB incorporates an extensive assemblage of Mesoproterozoic (1450–1360 Ma) magmatism that can be traced over ca. 3000-km long a west-east trending belt. These Mesoproterozoic granitoids display distinct geochemical signatures (e.g., Ga/Al*10,000 ranging from 1.46 to 3.88 and Zr + Nb + Ce + Y varying largely from 101 to 1066 ppm) and show a temporal progression from orogenic to anorogenic over a relatively short period. This suggests a tectonic setting that likely evolved from compressional to extensional environments during 1450–1360 Ma, perhaps resulting from slab roll back. We suggest that the 1450–1360 Ma magmatism along the southern CAOB corresponds with a transition from a compressional to extensional environment on the margin of the Nuna supercontinent. [ABSTRACT FROM AUTHOR]

Earth is the only planet known to be habitable, and is also unique with its liquid water, and the operation of plate tectonics. The geological record shows that the habitability of our planet can rapidly recover from major disasters or catastrophes, even those that cause mass extinctions. We suggest that plate tectonics, which acts as a link between the shallow and deep, is pivotal for the formation, evolution, and long-term stability of the hydrosphere, atmosphere, lithosphere, and thus life. Plate tectonics links the surface environment with the deep interior of high viscosity, low Reynolds number, low entropy, and low chaos, able to produce a strong healing effect to neutralize catastrophic events. It can transfer the bio-essential elements from the deep interior to the near-surface environment and can recycle toxic elements to the deep. This unique planetary energy and material transfer process of Earth is a continuous, slow-release, and bidirectional cycle, where a change in the surface is slowly buffered by a reaction from the deep, shaping a long-term and stable habitable environment. Therefore, it is considered that plate tectonics is the basic condition for the long-term stable evolution of the Earth's biosphere and the stabilizer of the Earth's habitability. [ABSTRACT FROM AUTHOR]

The activity of melts and fluids may have played a key role in inducing the destruction of the eastern North China Craton in the early Cretaceous. Carbonate melts are important agents in mantle metasomatism and can significantly modify the physical and chemical properties of the subcontinental lithospheric mantle. Carbonate metasomatism can be identified by specific geochemical indices in clinopyroxene, such as high Ca/Al and low Ti/Eu ratios. This study presents the spatial and temporal variations of carbonate metasomatism in the lithospheric mantle beneath the eastern North China Craton. Three types of carbonate metasomatism are classified based on the geochemical compositions of clinopyroxene in mantle peridotites. Clinopyroxene formed by Type 1 carbonate metasomatism is characterized by very high Ca/Al ratios (15-70) and 87Sr/86Sr ratios (0.706-0.713). Clinopyroxene derived from Type 2 carbonate metasomatism shows relatively high Ca/Al ratios (5-18) and 87Sr/86Sr ratios (0.703-0.706). However, clinopyroxene resulting from Type 3 carbonate metasomatism has low Ca/Al ratios (5-9) and 87Sr/86Sr ratios (0.702-0.704). Deep (garnet-bearing) and shallow (spinel-bearing) lithospheric mantle beneath the Sulu orogen and surrounding areas in the eastern North China Craton were affected by intense Type 1 carbonate metasomatism before the late Triassic. The deep subduction of the South China Block with its accompanying carbonate sediments was the trigger for Type 1 carbonate metasomatism, which reduced strength of the lithospheric mantle and provided a prerequisite for the destruction of the eastern North China Craton in the early Cretaceous. After the destruction of the eastern North China Craton, the ancient relict lithospheric mantle, represented by spinel harzburgite xenoliths hosted in the late Cretaceous to Cenozoic basalts, only recorded Type 2 carbonate metasomatism. This implies that the lithospheric mantle experienced the intense Type 1 carbonate metasomatism was completely destroyed and not preserved during decratonization. Spinel lherzolite xenoliths hosted in the late Cretaceous to Cenozoic basalts represent the young, fertile lithospheric mantle formed after the cratonic destruction and only a few samples record Type 2 and 3 carbonate metasomatisms. We suggest that carbonate melts derived from the subduction-modified asthenospheric mantle with variable proportions of recycled crustal material was responsible for the Type 2 and 3 carbonate metasomatisms. The carbonate metasomatism of the lithospheric mantle beneath the Jiaodong Peninsula and surrounding areas is very pervasive and is spatially consistent with the remarkable thinning of lithospheric mantle and giant gold deposits in this region. Therefore, we conclude that carbonate metasomatism in the lithospheric mantle played a crucial part in the modification, destruction and gold deposits in the eastern North China Craton. [ABSTRACT FROM AUTHOR]

The Beishan Orogenic Belt is located in the central southernmost part of the Central Asian Orogenic Belt (CAOB), which plays a key role in understanding the formation and evolution of the CAOB. Granitoids are the documents of crustal and tectonic evolution in orogenic belts. However, little is known regarding the petrogenesis and geodynamic setting of the widely distributed Paleozoic granitoids in the Northern Beishan Orogenic Belt (NBOB). The present study reveals significant differences concerning the petrogenesis and tectonic setting of early and late Paleozoic granitoids from the NBOB. The early Paleozoic granitoids from the 446–430 Ma Hongliuxia granite complex of the Mazongshan unit and the 466–428 Ma Shibanjing complex of the Hanshan unit show classic I-type granite affinities as revealed by the relative enrichment of LILEs and LREEs, pronounced depletions of Nb, Ta and Ti and the abundant presence of hornblende. Furthermore, they are characterized by strongly variable zircon ε Hf(t) values between − 16.7 and + 12.8 and evolved plagioclase Sr isotopic compositions of 0.7145–0.7253, indicating the involvement of both juvenile and ancient continental crust in the magma source. Thus, we propose that the early Paleozoic granitoids in the NBOB were generated in a subduction-related continental arc setting. In contrast, the late Paleozoic 330–281 Ma granitoids from the Shuangjingzi complex of the Hanshan unit exhibit positive zircon ε Hf(t) values between + 5.8 and + 13.2 and relatively depleted plagioclase Sr isotopic compositions of 0.7037–0.7072, indicating that they were mainly formed by remelting of juvenile crust. Thus, an intra-plate extensional setting is proposed to have occurred during formation of the late Paleozoic granitoids. Therefore, between the early and late Paleozoic, the magma sources of the NBOB granitoids converted from the reworking of both juvenile and ancient crusts during a subduction-induced compressional setting to the remelting of juvenile crust during an intra-plate extensional setting, respectively. The corresponding crustal growth in the southern CAOB is dominated by early Paleozoic lateral accretion of arc complexes and late Paleozoic vertical addition of juvenile material from the mantle. [ABSTRACT FROM AUTHOR]

An early extensive Neoproterozoic (ca. 900 Ma) continental magmatic arc system covering hundreds of kilometers has been reported to occur in the South Beishan Orogenic Belt (SBOB) and the Central Tianshan (CTA) in the southern Central Asian Orogenic Belt (CAOB). However, evidence for coeval high-grade metamorphism and thus the formation of an accretionary orogen in the framework of Rodinia is ambiguous or absent. This study provides new petrological, geochemical and geochronological data for garnet-bearing schists (quartz + garnet + biotite + plagioclase ± muscovite) from the SBOB in order to constrain its Neoproterozoic metamorphic history. The metamorphic zircon rims are either unzoned or display sector zoning in CL-images and reveal REE patterns with flat HREE patterns and negative Eu anomalies, which are interpreted to be in chemical equilibrium with garnet and plagioclase. The zircon U-Pb dating yields concordant U-Pb ages of 900 ± 3 Ma, 897 ± 2 Ma and 898 ± 4 Ma for the metamorphic zircon rims. The inherited detrital zircon cores of one sample display a concordant U-Pb age of 1397 ± 5 Ma that is consistent with the timing of formation for the extensive Mesoproterozoic continental arc in the SBOB and CTA. Based on phase equilibrium geothermobarometry and average P-T thermobarometric calculations, minimum amphibolite-facies P-T conditions are estimated to be >600 °C at pressure >0.6 GPa, which is thought to have been overprinted by subsequent Paleozoic metamorphism. However, the Ti-in-zircon thermometer still reveals temperatures of up to 840 °C using the composition of metamorphic zircon rims, suggesting former ca. 900 Ma granulite-facies peak metamorphic temperatures. The combined petrological and geochronological evidence in conjunction with the continental affinity of the regional metamorphic rocks suggests that the SBOB and the eastern CTA experienced an early Neoproterozoic accretionary orogenesis during the final assembly stage of Rodinia. [ABSTRACT FROM AUTHOR]

In this study, the Pb/U fractionation between zircon and uraninite during femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry (fs-LA-ICP-MS) analysis was studied in detail. The results show significant Pb/U fractionation between zircon and uraninite during fs-LA-ICP-MS analysis that when calibrated against the zircon standard M257, the obtained U-Pb age of the Chinese national uraninite standard GBW04420 is 17% older than the recommended value. Thus, the accurate in-situ U-Pb dating of uraninite by LA-ICP-MS requires matrix-matched external standards for calibration. Uraninite in thin sections of two U-mineralized leucogranite from the Gaudeanmus in Namibia was analyzed by a fs-LA-ICP-MS equipped with a Signal Smooth Device (SSD), using laser spot and frequency of 10 µm and 1 Hz, respectively. When calibrated using GBW04420 as the external standard, two samples give weighted mean Pb/U ages of 504±3 Ma (2 σ, n=21) and 503±3 Ma (2 σ, n=22), and only one of two samples yields a concordia U-Pb age of 507±1 Ma (2 σ, n=21). These results are consistent with ID-TIMS U-Pb ages of 509±1 and 508±12 Ma and are also indistinguishable from zircon U-Pb upper intercept ages of 506±33 Ma (2 σ, n=29) and 501±51 Ma (2 σ, n=29). The present study shows that in-situ U-Pb dating of uraninite can deliver more reliable formation ages of the deposit than dating coeval high-U zircon because the latter commonly suffer significant Pb loss after formation. Our results confirm that GBW04420 is an ideal matrix matching standard for in-situ U-Pb dating of uraninite. [ABSTRACT FROM AUTHOR]

The South Beishan Orogenic Belt (SBOB) in the southwestern Central Asian Orogenic Belt (CAOB) is thought to be an eastern extension of the Eastern Tianshan Orogen. Up to now, it has been suggested to consist of a well-preserved Paleozoic magmatic and sedimentary sequence with a possible former Neoproterozoic microcontinent. We provide new geochemical and geochronological data for gneissic granites of the SBOB in order to constrain its tectonic evolution and setting. The gneissic granitoids belong to the high-K, calc-alkaline series and are characterized by an enrichment of light rare earth elements (LREE) and large ion lithophile elements (LILE), a depletion of Nb, Ta, Ti, Sr, and Ba and a positive Pb anomaly. The petrography and geochemical signatures reveal a possible I-type granite affinity and are in accordance with typical Andean Arc granites. Zircon grains, yielding 206 Pb/ 238 U magmatic crystallization ages of 933 ± 2 Ma and 900–890 Ma for the Shibanshan and Huaniushan arc granites, respectively, manifest the former presence of an early Neoproterozoic Precambrian microcontinent in the SBOB. Zircon ɛ Hf ( t ) values range from −16.1 to 10.2, indicating that juvenile material and reworked ancient crust were involved in the source of the gneissic granites. Furthermore, in conjunction with studies of the adjacent regions, the results of the present study suggest that the former Precambrian microcontinent in the SBOB neither belonged to the nearby Dunhuang Block nor the Tarim Craton, but has a common affinity with the Central Tianshan Arc Terrane. It is also suggested that the 900–890 Ma plutons originated from the mixing of juvenile material with older crust in an Andean-type active continental arc setting during the assembly of Rodinia. Thus the SBOB plays a key role in understanding the tectonic evolution of the CAOB. [ABSTRACT FROM AUTHOR]

Highlights: [•] TTG in the interior of the Dunhuang blocks was formed at ∼2.7–2.6Ga. [•] Tarim experienced two-stage (∼2.7–2.6 and ∼2.5Ga) intrusion of Archean TTG. [•] Tarim was characterized by episodic generation of juvenile continental crust. [•] Paleoproterozoic and Paleozoic tectonothermal events were prevail in the Tarim craton. [•] Paleoarchean continental crust as old as ∼3.4Ga may have existed in the Dunhuang block [Copyright &y& Elsevier]

Abstract: Eclogite-hosted garnet–spinel–corundum–quartz-bearing titanohematite veins and lenses (10–20cm in width) are described for the first time in the Sulu ultrahigh-pressure metamorphic terrane. Some of the lenses were aligned parallel to the foliation of the host eclogite, suggesting that they were the product of ductile deformation of one titanohematite layer. A vein composed of titanohematite+ilmenite+hematite+spinel+garnet+corundum+quartz+K-feldspar+albite was studied in detail. Ti–Fe oxides account for up to >80% and Al-rich phases for ∼15% of the total volume of this vein. Electron microprobe analyses show that the titanohematite solid solution was made up of 0.75 hematite+0.25 ilmenite. The unusual mineral assemblage of garnet+spinel+corundum+quartz implies that this vein could have experienced high temperatures (>900°C). Although the garnets showed well-defined Mg and Mn diffusion zoning in the rim as a result of the high temperature event, slight Mg and Mn growth zoning was preserved in the core. Thus, we suggest that the Sulu UHP terrane could have experienced a short-lived, high-temperature (>900°C) stage during exhumation. Garnets in the titanohematite vein were characterized by extremely low trace-element contents. Petrological and geochemical features of the veins suggest that they could be metamorphic products of igneous cumulates composed of magnetite+plagioclase±clinopyroxene. [Copyright &y& Elsevier]

Abstract: Hydrothermally altered rocks are products of fluid–rock interactions, and typically preserve numerous quartz veins that formed as chemical precipitates from fluids that fill up cracks. Thus, quartz veins are the record of the fluid system that involved fracture flow in the direction of changing temperature or pressure. In order to decipher the fluid activity in the Sulu ultrahigh-pressure (UHP) terrane in eastern China, quartz veins together with an adjacent eclogite lens and the host gneiss were studied. In one location a deformed quartz vein is located at the boundary between the host gneiss and the eclogite lens. The amphibolite-facies overprinting of the eclogite lens decreases from the rim to the core of the lens, with fresh eclogite preserved in the core. The foliated biotite gneiss contains felsic veins and residual phengites. Zircon rims from the gneiss are characterized by melt-related signatures with steep HREE patterns, high Hf contents and negative Eu anomalies, and a pool of weighted average 206Pb/238U analyses reveal an age of 219±3Ma (2σ), which is younger than the UHP metamorphic age (236±2Ma, 2σ) recorded by zircons from the eclogite lens. This suggests that the gneiss in the Sulu UHP terrane could have suffered from partial melting due to phengite dehydration during the “hot” exhumation stage. The formation age of the quartz vein (219±2Ma, 2σ) defined by zircon rims agrees well with the partial melting time (219±3Ma, 2σ) of the host gneiss. The initial 176Hf/177Hf ratios of zircon rims from the quartz vein are obviously lower than zircons from the eclogite lens, but overlap with the coeval zircon domains from the nearby granite dikes produced by partial melting of orthogneiss. These observations suggest that the quartz vein and corresponding fluid flow could be associated with partial melting of the host gneiss. On the other hand, amphibole-bearing and HREE-rich zircon rims from the amphibolite pool an amphibolite-facies metamorphic age of 217±5Ma (2σ), overlap with the formation age of the quartz vein. This implies that retrogression of the eclogite lens could have been caused by melting-induced fluid flow. Based on the above observations, we speculate that partial melting of the gneiss in the continental subduction-related UHP belt could have induced a significant fluid flow during the exhumation stage, and thus contributed significantly to the extensive retrogression of eclogites in the Sulu UHP terrane. [Copyright &y& Elsevier]

Abstract: In situ U–Pb dating and trace element analysis of zircons, combined with a textural relationship investigation in thin section, is a powerful tool to constrain the ultra high-pressure stage of high-grade metamorphism. Two types of zircon grains have been identified in thin sections of a retrograde eclogite from the main hole of the Chinese Continental Scientific Drill project in the Sulu UHP terrane. Type 1 zircon grains occur as inclusions in fresh garnet and omphacite, and Type 2 zircon grains were found in symplectite around omphacite. The fresh rims of Type 1 zircons and mantles of a few Type 2 zircons exhibit remarkably lower REE, Y, Nb and Ta contents than the inherited zircon cores, suggesting coeval growth with garnet, rutile and apatite during UHP metamorphism. These may have formed in the UHP metamorphism and survived retrograde metamorphism. The weighted average 206Pb/238U age of these zircon domains (230±4Ma, 2σ) agrees well with the published age of coesite-bearing zircon separates (230±1Ma, 2σ), suggesting that the peak UHP metamorphism in the Sulu terrane may have occurred at ~230Ma. Zircon domains surrounded or cut across by symplectite could have been altered by retrograde metamorphism. Together, they provide a younger weighted average 206Pb/238U age of 209±4Ma (2σ). These retrograde zircon domains have similar REE compositions to the ~230Ma UHP zircon domains. These observations imply that the ~209Ma zircon domains could have formed by fluid activity-associated alterations in the amphibolite-facies metamorphism, which could have resulted in the complete loss of Pb but not REEs in these domains. [Copyright &y& Elsevier]

Abstract: Three distinct groups of eclogites (low-Mg–Ti eclogites, high-Ti eclogites and Mg-rich eclogites) and ultramafic rocks from the depth interval of 100–680 m of the Chinese Continental Scientific Drill Hole were studied. The low Mg#s (=100⁎molar Mg/(Mg+Fe)) (81–84%) and low Ni (1150–1220 ppm) and high Fe2O3 total (13–15 wt.%) contents of ultramafic rocks suggest a cumulate origin. Mg-rich eclogites show middle and heavy REE enrichments, which could not be produced by metamorphic growth of garnet. Instead, if the rocks formed from a light REE enriched magma, there may be an igneous precursor for some garnets in their protolith. Alternatively, perhaps they formed from a light REE depleted magma without garnet. The high-Ti eclogites are characterized by unusually high Fe2O3 total contents (up to 24.5 wt.%) and decoupling of high TiO2 from low Nb and Ta contents. These features cannot be produced by concentration of rutile during UHP metamorphism (even for samples with TiO2 >4 wt.%) of high-Ti basalts, but could be attributed to crystal fractionation of titanomagnetite (for those with TiO2 <∼4 wt.%) or titanomagnetite+ilmenite (for those with TiO2 >∼4 wt.%). Thus, we suggest that protoliths of the high-Ti eclogites were titanomagnetite/ilmenite-rich gabbroic cumulates. As a whole, the low-Mg–Ti eclogites are geochemically complementary to the high-Ti eclogites, Mg-rich eclogites and ultramafic rocks, and could be metamorphic products of gabbroic/dioritic cumulates formed by high degree crystal fractionation. All these observations suggest that parental materials of the ultramafic rock-eclogite assemblage could represent a complete sequence of fractional crystallization of tholeiitic or picritic magmas at intermediate to high pressure, which were later carried to ultrahigh-pressure conditions during a continental collision event. [Copyright &y& Elsevier]

• We report high-precision Zr isotopic data of an alkaline differentiation series. • δ94Zr value increases in samples with SiO 2 > 65 wt%. • Alkaline and tholeiitic igneous series differ in Zr isotopic evolution path. • The upper continental crust is not felsic enough to have a high δ94Zr value. • The finding is essential for interpreting Zr isotopic data of samples out of context. Stable Zr isotopes have shown great potential in tracing magma differentiation. However, it remains unclear if different magmatic systems have similar Zr isotopic evolution patterns. Here we report high-precision Zr isotopic compositions of the well-defined Shidao alkaline complex (SAC), eastern China, which show small but important differences from the Hekla tholeiitic volcanic suite, Iceland. The SAC comprises monzodioritic, syenitic, and granitic intrusions with high alkali contents, representing a magmatic suite produced by various degrees of cognate magma differentiation. From mafic to felsic samples, the Zr concentrations and Zr/Hf ratios increase first and then decrease significantly at the inflection of ∼65 wt% SiO 2 , suggesting zircon saturation started at ∼65 wt% SiO 2 during magma differentiation. The δ94Zr values (permil deviation of the 94Zr/90Zr ratio from IPGP-Zr standard) remain nearly constant at ca. +0.01‰ in samples with SiO 2 < 65 wt% but then gradually increase with SiO 2 in more felsic samples (from +0.05 to +0.63‰), indicating that the Zr isotope fractionation also occurs at ∼65 wt% SiO 2. The Shidao alkaline and Hekla tholeiitic suites show zircon saturation at SiO 2 ∼ 65 wt%, but their Zr isotopic evolution paths differ. The alkaline suite increases more slowly in δ94Zr compared to the tholeiitic one, with the former reaching the same δ94Zr value at SiO 2 higher by ∼5 wt%. Our findings represent the first observation of differences in Zr isotopic evolution from different igneous systems (tholeiitic versus alkaline), which should be considered when interpreting Zr isotopic data of samples out of context, such as detrital zircons or sedimentary samples. Based on the more sluggish Zr isotopic enrichment in the alkaline series than the tholeiitic one, we re-interpret the Zr isotopic composition of the upper continental crust, which may simply be not felsic enough to be isotopically heavier. [ABSTRACT FROM AUTHOR]

Sulfides are accessory phases in lunar rocks but are important for understanding lunar interior processes as well as impacts on the lunar surface. Whether or not the lunar mantle had achieved sulfide saturation during magma ocean evolution and displays homogeneous sulfur isotopes remains under debate. The Chang'e-5 (CE-5) mission returned young (2.0 Ga) basalts from a mare terrain in the northern Oceanus Procellarum. Here we study chemical and sulfur isotopic compositions (δ34S V-CDT) of sulfides from CE-5 basaltic fragments and combine them with δ34S of other young (3.1–3.0 Ga) lunar low-Ti basalt (NWA 10597 and NWA 4734) and gabbro meteorites (NWA 6950) to compare them with Apollo low-Ti and high-Ti mare basalts. The sulfides in basaltic fragments of CE-5 are troilites (FeS) with low abundances of Ni, Co, and Cu (e.g., Ni < 0.04 wt% and Ni/Co < 0.3). Textures and chemical compositions indicate that most troilites are late-stage crystallization products from the highly evolved CE-5 basalts. Several troilites occur in the matrices of impactite clasts and are intergrown with Fe–Ni metal (12–36 wt% Ni, Ni/Co of 12–39). These troilites are distinct from the major population of troilites with noticeably higher Ni abundances (mostly > 0.2 wt% with Ni/Co of 1–3) and reconcile with the addition of meteoritic materials into the impact melts. The δ34S V-CDT of large troilite grains (>10 μm) from the CE-5 basaltic fragments and lunar meteorites were obtained by high-precision, high-spatial-resolution femtosecond laser ablation MC-ICP-MS which achieved external uncertainty (0.65 ‰, 2SD at 8-μm laser spots) like nano-SIMS. Sulfur degassing during surficial effusive lava flow likely led to a slight decrease in δ34S (by ∼ 1 ‰) for some basaltic fragments; however, such effects were limited to the scale of bulk rock samples, consistent with previous results. The mean δ34S of troilites in CE-5 basaltic fragments (0.35 ± 0.25 ‰, 2SE, n = 45) is similar to those of ancient (3.8–3.1 Ga old) Apollo low-Ti and high-Ti mare basalts and the young gabbro cumulate NWA 6950 (0.56 ± 0.21 ‰, 2SE, n = 10). The paired NWA 10597 and NWA 4734 show consistent δ34S, lower than most values by ∼ 0.5 ‰. Current data thus indicate that most mantle sources of lunar basalts would be homogeneous for δ34S (0.6 ± 0.3 ‰) and minor regions may be different. The overall homogenous δ34S from different mantle sources with variably low sulfur contents supports sulfide-undersaturated accumulation of the lunar magma ocean, which was inherited from strong volatile loss and evaporative fractionation during the formation of the Moon. [ABSTRACT FROM AUTHOR]

In this study, a novel lithium metaborate fusion technique using a homemade fusion furnace and graphite crucibles was developed to produce homogeneous glasses from silicate rock powder. The glasses were then analyzed for both major and trace element concentrations by LA-ICP-MS. The parameters of the ratio of flux-to-sample, melting temperature and time, and closed fusion were optimized. It was found that homogeneous glasses could be obtained, and the loss of Pb was effectively suppressed at a low melting temperature and short time (900 or 950 °C for 5 min) in closed fusion. Compared to Pt or Pt–Au crucibles in the traditional flux fusion method, homemade graphite crucibles are more economical and omit the need of any releasing agent because the bottom curve design allows the melt to shrink into a bead for easy removal. Accurate results by LA-ICP-MS can be directly obtained by applying a quantitative calibration strategy using 100% oxide normalization, which offers a solution for unknown sample analysis without the prior determination of the concentration of an internal standard element. The analytical results of 42 major and trace elements in 5 USGS silicate rock reference materials (covering mafic to felsic rock types) using the developed LiBO2 fusion technique are consistent with the reference values within 10% for most elements, and analytical precision (RSD) is within 10% for most elements. The developed method is simple for preparing homogeneous glasses from rock powders, which displays great potential for the rapid and accurate determination of mass fractions of major and trace elements in silicate rocks using LA-ICP-MS. [ABSTRACT FROM AUTHOR]

Refertilization of depleted peridotites widely occurs in lithospheric mantle but is poorly understood in a continental subduction channel. The Sulu orogenic belt is a typical ultra-high pressure (UHP) terrane formed by continental subduction and collision. To understand the complex metasomatic processes on peridotites during continental subduction, we combined detailed petrographic and geochemical studies for fertile garnet lherzolites (Chijiadian) from the Sulu UHP terrane, as well as refractory peridotites (Xugou and Lijiatun) for comparison. The fertile garnet lherzolites (Chijiadian) are not residues of low-degree partial melting, but they formed from refertilization processes during peak-UHP metamorphic stages (garnet-facies) in a continental subduction channel, as reflected by abundant clinopyroxene (12 vol%) and garnet (12 vol%), low bulk-rock Mg# of 91 and high Al 2 O 3 of 2.4–3.3 wt%. Garnet, clinopyroxene, and orthopyroxene display secondary poikilitic textures and often contain early phases of olivine, spinel, and garnet inclusions, indicating later precipitation of these minerals into depleted peridotite protoliths. The clinopyroxenes show enrichment of large ion lithophile elements (LILE) and high 87Sr/86Sr of 0.7061–0.7084. The estimated pressure-temperature are 720–770 °C at 4.4–4.8 GPa, consistent with previous constraints on UHP conditions. These features suggest strong refertilization processes at UP-UHP conditions (garnet-facies) in continental subduction channels. The metasomatic agents for refertilization would be basaltic-intermediate melts which incorporated continental materials. Similarly, Xugou harzburgites and Lijiatun dunites also record the subducted continental signatures with enrichment of LILE and high Sr isotopes on clinopyroxenes (87Sr/86Sr: 0.7050 to 0.7065). However, Xugou harzburgites and Lijiatun dunites overall do not display the same typical refertilization features as for Chijiadian, as reflected by low abundances of clinopyroxene and high Mg# of 92–93. Consequently, continental subduction could lead to diverse types of metasomatism of refractory peridotites, including refertilization at UP-UHP metamorphic stages in subduction channels, as in other tectonic settings. • Secondary garnet lherzolites formed from refertilization at high-pressure condition in the subduction channel. • Continental subduction could lead to diverse types of metasomatism. • Continental subduction also drives the formation of refertilized lherzolites as other tectonic settings. [ABSTRACT FROM AUTHOR]

[Display omitted] [ABSTRACT FROM AUTHOR]

The isotope dilution (ID) method, owing to its high precision, is extensively used for the determination of element mass fractions in a wide range of natural samples. One of the prerequisites of the ID method is knowledge of the isotopic composition of an enriched spike, which is often challenging to accurately determine. In this study, we employ a regression mass bias correction model to accurately and precisely measure the isotopic composition of an enriched Hf spike (Lot No. 159293, Oak Ridge National Laboratory). A NIST SRM 3134 Re solution, whose isotopic composition was calibrated by an NRC IRIS‐1 Ir isotope standard, was used to calibrate the isotopic composition of the Hf spike. The obtained ratios of 176Hf/177Hf, 179Hf/177Hf and 180Hf/177Hf were 0.2406 ± 0.0005 (u, k = 1), 2.8620 ± 0.0005 (u, k = 1) and 384.65 ± 0.05 (u, k = 1), respectively, which meet the required precision levels for Hf isotopes in the application of the ID method. The combined uncertainties of the calibrated Re and Hf isotope ratios were evaluated using a Monte Carlo method, in which the uncertainty of the primary calibrator (IRIS‐1, 193Ir/191Ir = 1.6866 ± 0.0005, u, k = 1) was also taken into consideration. The precision of Hf spike was improved significantly compared with the SSB and C‐SSBIN methods. To the best of our knowledge, this is the first report of isotope ratio calibration in an enriched spike using the regression model. The precisely calibrated spike can lower the uncertainty of the Hf mass fraction significantly, thereby increasing the accuracy of the Lu‐Hf chronometer. [ABSTRACT FROM AUTHOR]

[Display omitted] • Juvenile crust in Singhbhum Craton formed at ∼3.51, ∼3.45, 3.38–3.25, 3.15–3.05 and ∼2.80–2.75 Ga. • Reworking of older crust in the craton occurred at ∼3.46, ∼3.3, ∼3.1 and ∼2.8 Ga. • Maximum crustal thickness was attained at ∼3.3 Ga followed by a possible reduction over ∼3.1–2.8 Ga. • Paleo-Meso–Archean continental growth occurred through episodic intraplate juvenile magmatism and resultant crustal reworking. The composition of continental crust and its temporal variation, the mechanism of crust-mantle interaction, and the degree of mantle depletion during the early Archean have been widely debated. To address these issues related to the Singhbhum Craton, we present whole-rock sediment geochemistry, detrital zircon U-Pb date, trace element and Hf isotope data from four Archean clastic sedimentary successions. The rocks have high whole-rock K 2 O/Na 2 O, relatively high La and Th compared to Ni and Sc, distinct negative Eu anomaly and flat HREE patterns, and high detrital zircon U/Yb ratios. These features suggest attainment of early crustal stability with the sediments derived from a strongly weathered basement dominated by granitoids formed through shallow intracrustal melting. Detrital zircon U-Pb and Hf isotope data indicate episodic crust formation at ∼3.51, ∼3.46, 3.38–3.25, 3.15–3.05 and ∼2.80–2.75 Ga. Each major crust formation event is marked by addition of depleted mantle-derived juvenile crust and its quick reworking. Besides, episodic tapping of older crust, as indicated by a wide range (both positive and negative) of zircon εHf t values, are evident at ∼ 3.46, ∼3.3, ∼3.1 and ∼2.8 Ga. Pressure-sensitive zircon trace element ratios suggest that the crust attained the maximum thickness at ∼3.3 Ga followed by a possible reduction in thickness over ∼3.1–2.8 Ga. In the absence of strong evidence of subduction, the rock association and their temporal distribution (coeval granitoid and mafic-ultramafic magmatism) suggest that the Paleoarchean-Mesoarchean crustal growth in the Singhbhum Craton was a result of episodic, depleted mantle-derived, intraplate magmatic injection and attendant crustal reworking. [ABSTRACT FROM AUTHOR]

Complete sample digestion is a prerequisite to achieve accurate and precise results of elemental concentrations and isotopic compositions in Ti-rich minerals of interest, such as refractory rutile. In this study, a rapid digestion protocol using ammonium bifluoride (NH4HF2) was developed to completely digest large amounts of rutile, ilmenite, titanite and perovskite. These Ti-rich samples (50 mg) can be completely digested in 4 hours with the use of 300 mg of NH4HF2 at 230 °C, and each 200 mg of rutile and ilmenite ore can be completely dissolved with NH4HF2 digestion and without insoluble residues present. Furthermore, NH4HF2 digestion was found to be effective in dissolving the different sizes (31–150 μm) of Ti-rich minerals. Compared to common HNO3–HF closed-vessel acid digestion, the proposed NH4HF2 digestion provides consistent results for major Ti and thirty-six other trace elements in a series of ilmenite ore reference materials and in-house Ti-rich minerals. It was found that elemental concentrations (Ti, Sc, V, Cr, Nb, Ta, Hf and U) in rutile measured by inductively coupled plasma-mass spectrometry (ICP-MS) using NH4HF2 digestion were consistent with the values measured in the pressed powder pellet of rutile by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). However, lower recoveries of Ti, V, Nb and Ta in rutile were obtained from closed-vessel acid digestion, possibly due to the formation of white precipitates during the evaporation/redissolution process. The proposed NH4HF2 digestion is safe and more effective in quickly dissolving Ti-rich materials and suitable for the determination of quantities of major and trace elements. [ABSTRACT FROM AUTHOR]

• Negative Ce anomaly in the Gaoyuzhuang and Hongshuizhuang formations provides the evidence of transient oxygenation of the Mesoproterozoic ocean. • The proposed Ce anomaly depth model provide a quantitative constrain the surface environment of the Yanshan Basin. • Transient oxygenations could have provided vital niches for the evolution of eukaryotes. Predominantly anoxic conditions with a heterogeneous stratified water column are widely accepted for the Mesoproterozoic ocean. However, transient and episodic oxygenation during the Mesoproterozoic has been recently hypothesized, which may have been an important trigger for eukaryote evolution. In this study, we analyzed the Ce anomalies of the Gaoyuzhuang and Hongshuizhuang formations in North China, to investigate the Earth's surface environment during the Mesoproterozoic. Our data of negative Ce anomalies in the Gaoyuzhuang and Hongshuizhuang formations, reaching 0.73 and 0.84, respectively, suggest transient oxygenations of the surface environment. We applied a Ce N /Ce N * depth model to quantify these transient oxygenations and the results suggest that the atmospheric oxygen level would have increased by 0.01–0.03% present atmospheric level (PAL), 0.02–0.05% PAL, and 0.1–0.4% PAL, with the respective initial levels of 0.05% PAL, 0.1% PAL, and 1% PAL, in the Gaoyuzhuang and Hongshuizhuang formations. Our results suggest that although oxygen levels in the Mesoproterozoic were low, transient oxygenation may have occurred in the surface ocean, which would have provided vital niches for the evolution of eukaryotes. [ABSTRACT FROM AUTHOR]

The successful return of lunar soil samples from the northern Oceanus Procellarum by the Chang'E 5 (CE-5) mission has provided unprecedented ground-truth information for the previously unexplored region of the Moon. In particular, the particle size and mineral constituents of the CE-5 soil samples are of critical importance to interpret remote sensing data. With a Raman-based particle analysis system, we show that the particle size properties and mineral constituents of the CE-5 soil can be simultaneously determined with a small sample size (ca. 30 μg). The CE-5 sample scooped from the lunar surface has an overall small size between 0.4 μm and 73.9 μm (mean=3.5 μm), and mainly consists of pyroxene (39.4%), plagioclase (37.5%), olivine (9.8%), Fe-Ti oxides (1.9%), glass (8.3%) and other minor or trace phases. The results are consistent with previous analyses with larger sample sizes. In addition to minimum sample consumption, this method requires very little sample preparation, and can rapidly build a large database with each particle precisely traceable. Therefore, this novel technique is particularly suitable for the analysis of future returned soil samples from extraterrestrial bodies. [ABSTRACT FROM AUTHOR]

Ocean island basalts (OIBs) with Zn isotopic ratios higher than the normal mantle (δ66Zn = 0.17 ± 0.08‰) or mid-ocean ridge basalts (MORBs; δ66Zn = 0.27 ± 0.06‰) generally also have an enriched Sr-Nd isotopic signature, suggesting carbonate-bearing eclogites, whose protolith is inferred to be subducting altered oceanic crust, in their mantle source. On the contrary, continental intraplate basalts with high δ66Zn usually show depleted Sr-Nd isotopic signatures (i.e., decoupled Zn-Sr-Nd isotopic composition). To elucidate the origin of the decoupled Zn-Sr-Nd isotopic composition in continental intraplate basalts, we report the discovery of both coupled and decoupled Zn-Sr-Nd isotopic data for a suite of Cenozoic continental intraplate basalts from the Zhejiang province, Southeast China. These basalts display clear spatial and temporal geochemical variations, with early-stage inland low-silica samples presenting moderately enriched Sr-Nd isotopic signatures and high δ66Zn (coupled Zn-Sr-Nd isotopic composition, similar to OIBs), and later-stage coastal high-silica samples that display a pronounced δ66Zn decrease with increasing SiO 2 and 87Sr/86Sr and with decreasing alkali contents and 143Nd/144Nd (decoupled Zn-Sr-Nd isotopic composition). The early-stage basalts with coupled high Zn-Sr-Nd isotopic signatures are also more enriched in incompatible elements than any other basalts from eastern China reported so far. We explain the spatial and temporal geochemical variations of these basalts as the result of two main melting events: 1) the low-silica early-stage magmatism mostly occurs inland and results from high-pressure partial melting of a carbonated eclogite-bearing asthenospheric mantle. Because of the presence of a thick lithosphere limits the melting of the depleted mantle component, the signature of the Zn-Sr-Nd isotopically enriched, and more fusible carbonated eclogite is preserved. 2) At the later stage, magmatism mostly occurs on the coast where the subcontinental lithosphere is thinner. Hence, decompression melting progresses to shallower depth, resulting in an increase of the contribution from the depleted peridotite matrix and a dilution of the signal from the isotopically enriched fusible component. Further upwelling and in-situ melting at the base of the subduction-modified sub-continental lithospheric mantle (SCLM) explains both the decoupled Zn-Sr-Nd isotopic signature of the coastal basalts and their major and trace element variability. We further propose that decompression melting is driven by small-scale convection resulting from variations of lithospheric thickness. Our data highlight the importance of dynamic melting of carbonated eclogite-bearing asthenosphere and subsequent lithospheric melting in preservation and destruction of the coupled enriched Zn-Sr-Nd isotopic signature of carbonated eclogite component and generation of the apparent decoupled Zn-Sr-Nd isotopic signal commonly observed in continental intraplate basalts. [ABSTRACT FROM AUTHOR]

Abundant oriented silica precipitates of α-quartz (4.0 ± 1.0 vol.%), in part coexisting with calcic amphiboles (< 0.2 vol.%), have been identified in clinopyroxenes of eclogites from the Weihai area, Sulu ultrahigh pressure terrane, eastern China. Electron backscatter diffraction (EBSD) analyses demonstrate that the majority (97%) of quartz precipitates have topotactic relationships with their host clinopyroxenes. Three types of crystallographic topotactic relationship have been identified between quartz and host clinopyroxene: (1) 52% quartz precipitates share the same orientation for the c -axes with [0001] qz //[001] cpx ; (2) 34% quartz precipitates share the same orientation for the a -axes with [11 2 ¯ 0] qz //[001] cpx ; and (3) 11% quartz precipitates share the same orientation for the s -planes with (11 2 ¯ 1) qz //(100) cpx . Other quartz axes and planes disperse in large or small girdles around the shared axes or planes. Many quartz rods/needles are elongated parallel to the [001] cpx with the long axes of quartz being either [0001] qz or [11 2 ¯ 0] qz . Amphibole precipitates have also a strong crystallographic relationship with host clinopyroxene, i.e., (100) amp //(100) cpx , [010] amp //[010] cpx , and [001] amp //[001] cpx . These results provide quantitative microstructural evidence supporting an exsolution origin for oriented quartz needles/rods in clinopyroxene and demonstrate that the exsolution of quartz from clinopyroxene occurred within the stability field of α-quartz rather than coesite. The oriented precipitates of α-quartz, in part coexisting with calcic amphiboles, in host clinopyroxene are probably promoted by supercritical fluid or partial melting during the early exhumation of eclogites. Our results suggest that oriented quartz precipitates in clinopyroxene cannot be used as an indisputable UHP-indicator. [ABSTRACT FROM AUTHOR]

The metasomatized sub-continental lithospheric mantle (SCLM) is increasingly proposed to play a key control in the formation of giant gold (Au) deposits. However, the extent of Au enrichment in metasomatized SCLM and the Au contents of its derivative partial melts remain poorly constrained. Lamprophyres are derived from low-degree melting of metasomatic and fusible components in the SCLM, and could provide fundamental information about the metasomatized source and metal release compared to mantle peridotites and/or pyroxenites. The giant Jiaodong Au province (> 5000 tons, ∼ 120 Ma) in the eastern part of the North China Craton (NCC) is an ideal locality to assess the Au endowment of metasomatized SCLM which may serve as the source of Au, as indicated by the presence of mantle-dominated volatiles in auriferous fluids associated with the deposits. Based on detailed petrological studies, we analyzed Au, S, Cu and platinum-group element (PGE) contents of the SCLM-derived lamprophyres that are temporally (130–121 Ma) and spatially associated with the Jiaodong lode Au deposits. The lamprophyre dykes were emplaced in the deep crust and did not experience significant degassing and sulfide segregation, and the sulfide saturation occurred at a late stage during magma cooling, as demonstrated by sulfide petrography, S contents, Cu/S and Cu/Pd ratios of the lamprophyres. The relatively oxidized (ΔFMQ +1 – +2), hydrous (2–4 wt.% H 2 O) lamprophyres display variable and generally low Au contents (0.04–3.59 ng/g, mainly 1–3 ng/g, n = 31), as well as low PGE and Cu contents. Their high Au/Cu (N) and Au/Pd (N) ratios together with high Ba/Nb indicate a discernible Au addition to their source, resulting from multi-stage mantle metasomatism related to subduction. However, the average Au contents of the metasomatized SCLM before large-scale Au mineralization are heterogeneous and overall in a range of 0.5–1.5 ng/g. The values are higher than that of depleted SCLM (< 0.5 ng/g) but are still lower than or similar to the fertile upper mantle (1.2–1.7 ng/g). These results indicate that mantle metasomatism related to subduction replenished some amount of Au into previously depleted SCLM, leading to local or regional Au enrichment. However, such processes evidently did not result in remarkable Au enrichment of the mantle source beneath the eastern part of the NCC. We thus propose that the metasomatized SCLM and magmas derived from it, though without anomalously high Au contents, could still provide large amounts of Au for large-scale Au mineralization. Importantly, metasomatic volatiles from the metasomatized SCLM exert a key role, and they enable efficient release of Au from mantle sources, promote Au transportation along trans-lithospheric fault channels and subsequent enrichment and precipitation via magmatic-hydrothermal processes for giant Au deposits. [ABSTRACT FROM AUTHOR]

The Dunhuang block, which constitutes the northeastern segment of the Tarim Craton, is located between the Central Asian Orogenic Belt (CAOB) to the north and the Altyn–Qilian Orogenic Belt to the south. The present study reveals that the early Paleozoic HP mafic granulites from the Dunhuang block underwent four stages of metamorphism: prograde amphibolite-facies (M1), peak high-pressure (HP) granulite-facies (M2) and two late stages of amphibolite-facies retrograde metamorphism. Based on phase equilibrium modeling, P–T conditions of the four stages of metamorphism are estimated at 720–750°C and 11–13kbar, 760–800°C and 14–16kbar, 690–720°C and 8–8.5kbar, and at <6kbar and <640°C respectively. Peak granulite-facies metamorphism is characterized by a low geothermal gradient of ca. 16°C/km. Zircon U–Pb dating shows that the HP granulite-facies metamorphism occurred at ca. 431Ma and the early retrograde amphibolite-facies overprint at ca. 403Ma. Thus the investigated mafic rocks here reveal a clockwise P–T–t path involving burial heating before peak granulite-facies metamorphism and subsequent decompression–cooling with an uplift rate of ca. 0.8km/Ma. This, together with a continental affinity of the HP metamorphic rocks, indicates that the Dunhuang block experienced a collisional orogenesis during the early Paleozoic. [ABSTRACT FROM AUTHOR]

The architecture and growth history of Precambrian crustal basements in the Central Tianshan Block play a key role in understanding the tectonic evolution of the Chinese Tianshan Orogenic Belt. In this study, we present precise LA-ICP-MS zircon U-Pb dating and LA-MC-ICPMS zircon Hf isotopic data for two granitic gneisses from Alatage area in the Central Tianshan Block. The magmatic zircons from both samples yield similar protolith ages of 945 ± 6 and 942 ± 6 Ma, indicating that the early Neoproterozoic magmatism is prevailed in the Alatage area. These zircons have crustal Hf model ages of 1.82-2.22 and 1.70-2.03 Ga, respectively, which are significantly older than their crystallization ages. It indicates that their parental magmas were derived from the reworking of ancient crust. However, we suggest that these Paleoproterozoic Hf model ages might result from mixing of continental materials with different ages in the Neoproterozoic crust. The inherited (detrital) zircon cores not only yield a wide age range of ca. 989-1617 Ma, but also exhibit large Hf-isotope variations with Hf model ages of 1.54-2.30 Ga. In particular, some 1.4-1.6 Ga zircons show high initial Hf/Hf ratios, consistent with those of depleted mantle, which indicates that the Mesoproterozoic event involved both reworking of older crust and generation of juvenile crust. The Central Tianshan Block has different Precambrian crustal growth history from the Tarim Craton. Therefore, it would not be a fragment of the Precambrian basement of the Tarim Craton. [ABSTRACT FROM AUTHOR]

We present detailed characterization of Tanz zircon megacrysts for the microbeam determination of U–Pb ages, Zr isotopes, Hf isotopes, O isotopes and trace element mass fractions. This batch of dark brown zircon megacrysts from Tanzania contains 269 ± 103 μg g−1 U (Th/U ∼ 0.154), and its total weight is 9.06 kg. The largest Tanz zircon megacryst in this batch weighs 366 grams. The calculated average accumulated alpha-radiation dosage is 0.54 × 1018 events per g for the Tanz zircon, which correlates with a 'well crystallized' structure. Through a large number of laser ablation ICP-MS, laser ablation MC-ICP-MS and SIMS measurements, it is found that Tanz zircon megacrysts are quite uniform in U–Pb ages, O isotopes and Zr isotopes at scales of tens of microns. The Tanz zircon has chemical abrasion isotope dilution TIMS (CA-ID-TIMS) determined mean isotopic ratio values of 0.09180 ± 0.00013 (2SD, n = 47) for 230Th corrected 206Pb/238U, 0.7473 ± 0.0014 (2SD, n = 47) for 207Pb/235U and 0.059069 ± 0.000067 (2SD, n = 47) for 230Th corrected 207Pb/206Pb. The CA-ID-TIMS method yielded a mean 230Th corrected 206Pb/238U age of 566.16 ± 0.77 Ma (2SD, n = 47). The determined mean δ18OVSMOW and δ94/90ZrSRM3169 values of the Tanz zircon megacrysts are 6.52 ± 0.28‰ (2SD, n = 29) and −0.01 ± 0.06‰ (2SD, n = 35) by gas source mass spectrometry and double spike TIMS, respectively. All of these values are in good agreement with the statistical mean values of microbeam measurements and are proposed as the best reference values for Tanz zircon megacrysts. These features make the Tanz zircon megacrysts suitable as primary U–Pb age and Zr–O isotope reference materials for microbeam analysis. However, our LA-MC-ICP-MS data suggest a relatively wide distribution of Hf isotope compositions in the Tanz zircons (0.281821 ± 0.000042, 2SD, n = 321), which makes Tanz zircons not an ideal Hf isotope reference material for microbeam analysis. We propose the Tanz zircon megacrysts as a potential reference material for the primary external calibration or monitoring of analytical validation for microbeam determination of U–Pb ages and Zr–O isotopes. [ABSTRACT FROM AUTHOR]

A protocol was established for simultaneous measurements of zircon U-Pb ages and trace elements by LA-ICP-MS at spot sizes of 16-32 µm. This was accomplished by introducing N2 into ICP to increase the sensitivity. The obtained U-Pb ages for zircon standards GJ-1, TEMORA and SK10-2 are consistent with the preferred values within about 1% uncertainty (2σ) by simple external calibration against zircon standard 91500. Different data reduction softwares could yield different uncertainties for calculation of U-Pb ages. The commercially available program GLITTER4.4 could apply an improper uncertainty calculation strategy, but it may yield artificial high precisions for single analyses. Our trace element analyses indicate that Si is not an ideal internal standard for zircon when calibrated against the NIST glasses. Calibration against the NIST glasses using Si as an internal standard, a systematic deviation of 10%-30% was found for most trace elements including Zr. However, the trace element compositions of zircon can be accurately measured by calibration against multiple reference materials with natural compositions (e.g., BCR-2G, BHVO-2G and BIR-1G), or calibration against NIST SRM 610 and using Zr as an internal standard. Analyses of two pieces of GJ-1 demonstrate that it is relatively homogenous for most trace elements (except for Ti). [ABSTRACT FROM AUTHOR]

Abstract: Rutile and zircon in eclogites from the main hole of the Chinese Continental Scientific Drilling (CCSD-MH) were analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and electron microprobe (EMP). Both single spot and profile analyses of large matrix rutiles (>60μm) generally demonstrate core–rim variability of Pb, Sr, Zr and U. Pb and Sr show enrichment at the rims, while Zr and U decrease in concentration from the cores to the rims. Correspondingly, temperatures estimated by Zr-in-rutile geothermometers are higher within the cores (mainly in the range of 680–740°C) than at the rims by 10–30°C. We note that estimated temperatures within the cores of matrix rutiles correlate positively with grain diameter. This suggests that the Zr content in rutiles is not only dependent on temperature and pressure, but is also affected by fluid activity and Zr diffusion. Estimated temperatures within the cores of matrix rutiles merely represent lower limits of the peak ultra-high pressure (UHP) metamorphic temperatures. Combined with Th/U and Ce/Lu ratios, rare earth element (REE) patterns and 206Pb/238U ages, Ti-in-zircon geothermometers can be used to distinguish the thermal evolution of eclogites during the UHP metamorphism. Zircons of 745±8.0Ma (2σ, n =3) show evidence of the temperatures at which they crystallized from the original magma. Zircons of 240±7.0Ma (2σ, n =11) with flat HREE patterns suggest a definite temperature range (689±18°C (2σ, n =11)) for the prograde metamorphism. Although 226Ma is generally considered the time of the peak UHP metamorphism for the Dabie–Sulu orogen, except for a few grains with a maximum temperature of 744°C, most of the 226±2.0Ma (2σ, n =12) zircons indicate lower temperatures (average=698±12°C (2σ, n =12)). These data imply that the 226Ma zircons were probably not products of the peak UHP metamorphism, but might instead be associated with the pressure decrease in the post-peak metamorphism. The youngest zircons (<220Ma) provide evidence for temperatures (682±14°C (2σ, n =11)) associated with the retrograde metamorphism. Geothermometers that incorporate both rutile and zircon indicate that there may have been experienced a locally short-lived heating event for eclogites from the CCSD-MH. [Copyright &y& Elsevier]

Discontinuous ophiolites within the Indus–Tsangpo suture zone (ITSZ) in southern Tibet represent remnants of Neo‐Tethyan oceanic lithosphere, which are considered to have formed during the late Jurassic to early Cretaceous. We report field observations, petrological and geochronological data for some mafic intrusions in a tectonic mélange in the southern ophiolitic belt of the western ITSZ. Zircon from a gabbro yields an age of 243 ± 1 Ma with εHf(t) values of +7.9 to +13.2. Rare earth element (REE) pattern of this rock resembles that of normal mid‐ocean ridge basalt. We suggest that such gabbro and surrounding mafic–ultramafic rocks represent the remnants of middle Triassic oceanic lithosphere in the ITSZ. Our findings indicate that the Neo‐Tethys Ocean between India and the Lhasa terrane existed from at least the middle Triassic, contrasting with the commonly held view that the Neo‐Tethys Ocean opened along the northern edge of Gondwana during the late Triassic–early Jurassic. [ABSTRACT FROM AUTHOR]

High sensitivity and minimized spectral interference are prerequisites for precise and accurate measurement results of ultra-trace REEs (Sc and Y, rare earth elements) in geological samples (e.g., carbonates and peridotites). In this study, we designed a heating-condensing system for the direct determination of mass fractions of ultra-trace REEs in carbonates and peridotites by Ar–N2 mixed plasma ICP-MS combined with different skimmer cones. Compared to those under normal conditions (without a heating-condensing system), the signal sensitivities of the investigated 47 elements were improved by 5–8 and 6–24 fold at a heating temperature of 180 °C when using the H skimmer cone and the X skimmer cone, respectively. Our results firstly indicate that the geometry of the skimmer cone has an important effect on signal enhancement when using the heating-condensing system in ICP-MS. The addition of nitrogen (3–9 ml min−1) in the central channel of the plasma was found to significantly reduce the oxide ratios (CeO+/Ce+) by a factor of approximately 5–10. This reduction is important for the determination of ultra-trace REEs, which are well known to be interfered by oxides of Ba and light REEs. We successfully applied this method to directly determine ultra-trace REEs in eight reference carbonates and peridotites. This simple and rapid method shows great potential for the direct determination of ultra-trace REEs in geological samples and other technogenic materials with a high matrix and low REE abundances. [ABSTRACT FROM AUTHOR]

Bastnäsite is widespread in alkali granite, carbonatite and REE ore deposits. The U-Th-Pb ages of bastnäsite can constrain the mineralization age. Currently, the lack of suitable in situ analysis reference material is the major obstacle of bastnäsite U-Th-Pb geochronology. In this study, the matrix effects of U-Pb and Th-Pb age determination in bastnäsite using glass NIST 610 as the external calibration reference were evaluated with the 193-nm excimer LA-ICP-MS analysis in normal and additional gases laser ablation modes. The obtained U-Th-Pb ages of bastnäsite were approximately 7–11% lower than their reference values in the normal analytical mode (without additional gas). Fortunately, the determined systematic age biases in U-Th-Pb dating were significantly reduced (less than 1–2%) with the addition of water vapor within the ablation chamber. This reduction may be attributed to the observed significant suppression of 206Pb/238U and 208Pb/232Th downhole fractionation in both NIST 610 glass and bastnäsite by introducing a small quantity of water vapor in the ablation chamber. In addition, the obtained 206Pb/238U and 208Pb/232Th ages of bastnäsite K-9, LZ1384, and MAD809 showed great consistency with their corresponding recommended values. The obtained results show that accurate and precise U-Th-Pb ages of bastnäsite can be simultaneously obtained by using glass NIST 610 as the primary calibration standard in 193-nm LA-ICP-MS with the water vapor-assisted method. This simple and effective water vapor-assisted non-matrix-matched laser ablation method helps to promote the geological application of bastnäsite U-Th-Pb geochronology. [ABSTRACT FROM AUTHOR]

The deep carbon cycle requires tracers to understand carbon sequestration and mobility in the deep Earth. Recently, the use of metal stable isotopes has emerged as a promising and innovative approach to address element cycles, such as the use of magnesium and zinc isotopes to trace the magnesium carbonate cycle. However, despite the prevalence of calcium carbonate as the dominant sedimentary carbonate during the Phanerozoic era, its tracking through the use of metal stable isotopes has proven challenging. Here we show that deep subduction of Phanerozoic calcium carbonates can significantly decrease the δ44/40Ca value, while simultaneously increasing the δ66Zn value and 87Sr/86Sr ratio of the mantle. The Neogene Dalihu basalts in Inner Mongolia have high 87Sr/86Sr ratios, ranging from 0.7058 to 0.7063, which are positively correlated with Sr/Nd ratio, indicating the presence of sedimentary carbonate within their mantle source. The Dalihu basalts exhibit significantly lower δ44/40Ca values (0.51 to 0.70‰) but higher δ66Zn values (0.35 to 0.45 ‰) than the mantle. These low δ44/40Ca values cannot be attributed to partial melting, even when considering the jadeite effect. Our calculations indicate that adding 5–10% recycled calcium carbonate into the mantle source explains the high 87Sr/86Sr ratio and δ66Zn values but low δ44/40Ca values of the Dalihu basalt. Therefore, recycled calcium carbonate directly influences correlated Ca-Zn-Sr isotope variation, thereby providing compelling evidence for its role in the deep carbon cycle. Our findings suggest that combining metal stable isotopes with radiogenic Sr isotope is a powerful tracer of the deep carbon cycle. [ABSTRACT FROM AUTHOR]

• A link between mantle thermal, redox evolution and speciation of C-O-H magmatic volatiles is established, which is used to assess the contribution of mantle degassing on atmospheric oxidation. • We find that a rapid oxidization of Archean mantle related to recycling of oceanic crust, core-mantle material exchange, or evolution of primitive mantle redox heterogeneities can strongly reduce the fraction of reducing compositions (e.g., H 2 and CH 4) in volcanic gases, which then consumed less photosynthetic oxygen, leading to a net increase of atmospheric oxygen and triggering the Great Oxidation Event (GOE) at 2.4–2.3 Ga. • After the GOE, atmospheric oxidation events were likely triggered by plume and rifting degassing during supercontinent breakup. • Before the GOE, scattered oxygen oases can be produced above plume impingent regions. The C-O-H cycling of the early shallow Earth is suggested to be closely related to mantle degassing and speciation processes. These processes are influenced by the mantle's thermal and redox states, which have changed significantly in different mantle reservoirs during Earth's protracted history. However, the link between speciation of C-O-H magmatic volatiles and the temporal changes of the mantle's thermal and redox states in different mantle reservoirs remains elusive. We test this link through chemical equilibrium modeling of C-O-H magmatic volatiles to assess its influences on shallow C-O-H cycling and the oxidization history of the shallow Earth. We find that a rapid oxidization of Archean mantle related to recycling of oceanic crust, core-mantle material exchange, or evolution of primitive mantle redox heterogeneities can strongly reduce the fraction of reducing compositions (e.g., H 2 and CH 4) in volcanic gases, which then consumed less photosynthetic oxygen, leading to a net increase of atmospheric oxygen and triggering the Great Oxidation Event (GOE) at 2.4–2.3 Ga. After the GOE, mantle degassing at rifts, mid ocean ridges, and plumes became more oxidizing and thus triggered later atmospheric oxidation synchronous with supercontinent breakup. Our results support that the oxidation of the atmosphere in the Precambrian was influenced by mantle oxidation, upwelling and/or degassing, especially during the GOE. [ABSTRACT FROM AUTHOR]

MC-ICP-MS has become one of the most powerful analytical methods for Si isotopes in bulk liquid and solid samples in the past decade. Laser ablation provides direct sampling of solid samples, avoiding laborious chemical digestion procedures. As for powder bulk samples, the preparation of stable and homogeneous targets prior to measurements, and strategies to minimize potential matrix effects, are critical for accurate isotopic analysis. In this study, an accurate and precise method for Si isotope ratio measurements by fs-LA-MC-ICP-MS of bulk silicate rock samples was established. A new laser fusion sample preparation technique was developed to achieve fast and homogeneous fusion of silicate rock powders (including granite and granodiorite that contain abundant refractory minerals) into glasses. Compared to the pressed pellet technique, the measurement precision for fused glasses was improved ∼5.7-fold. Matrix effects during Si isotopic analysis were observed when using non-matrix matched calibration protocols under normal dry-plasma instrument conditions with both ns- and fs-laser using a raster ablation mode. Matrix effects were eliminated by the addition of water vapor into the plasma, realizing accurate non-matrix matched calibration. In addition, using a fs-laser provided better measurement precision, with the internal and external precisions being improved ∼1.85 and ∼2.4 fold compared to a ns-laser at nearly equal signal intensities. Five well characterized silicate rock reference materials were analyzed using fs-LA-MC-ICP-MS calibrated against NBS-28 and BHVO-2G. Results obtained for δ29Si and δ30Si for these five reference materials were in agreement with previously reported values, confirming the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

• Granitoids of Singhbhum Craton. • Two generation of TTGs at 3.42 and 3.32 Ga formed by melting of juvenile mafic crust. • Later K-rich, silicic granites at 3.28 and 3.25 Ga formed by melting of tonalites. • Recurring crustal melting in a gradually thickening oceanic plateau. • Final cratonisation of the Singhbhum Craton at 3.25 Ga. A significant part of many Archean cratons formed during Paleoarchean. Yet, the mechanism and tectonic setting of formation of Paleoarchean continental crust remain highly debated. In this contribution, we present field, petrographic, geochemical, zircon U-Pb age and Hf isotope data on Paleoarchean granitoids from west-central part of the Singhbhum Craton (Champua-Hat Gamharia corridor), India. The whole process starting from nucleation of a juvenile continent to its evolution and final stabilization is documented. The core of the craton nucleated with formation of 3.45–3.40 Ga TTGs showing juvenile character (zircon ɛHf t = +0.6 to +7.1). These rocks show slightly depleted HREE and Y, negligible Eu-anomaly (Eu/Eu* = 0.90 to 1.00) and moderate Sr/Y (25–64), consistent with derivation from a low-K mafic crust at a pressure near the lower end of the garnet stability field, causing subordinate garnet retention in the residue and negligible role of plagioclase. A second generation of TTG formation took place at 3.32 Ga in the area by deeper melting of a juvenile mafic crust (zircon ɛHf t = +1.3 to +5.7) as suggested by strongly depleted HREE and Y, and high Sr/Y (52–155) implying significant amount of garnet retention in the residue. Subsequently, the area witnessed intracrustal melting at 3.28 and 3.25 Ga which tapped moderately old to juvenile (zircon ɛHf t = −1.9 to +4.5), mostly TTG sources at variable depths generating potassic, LILE-enriched, high-silica granites. Intrusion of these potassic granites marks the final cratonization of the Singhbhum Craton. The sequence of events is interpreted in terms of repeated crustal melting and granitoid generation in a gradually thickening oceanic plateau with a progressive change in granitoid source from mafic to felsic in composition. A synthesis of rock assemblage, regional geological setting and structural pattern also supports intraplate nature of the magmatism in Singhbhum Craton, which might have been a significant mechanism of crustal growth worldwide during Paleoarchean. Further, a comparison of juvenile crustal growth and crustal reworking events of the Singhbhum and other Indian cratons show that these cratons record distinct evolutionary histories and were probably nucleated at different sites. [ABSTRACT FROM AUTHOR]

A simple and rapid method using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) for direct multi-element analysis of wine samples without any sample pretreatment is described. Bestowed with its micro-sample consumption, the proposed method offers advantages of direct multi-element analysis in wine samples with high ethanol (1–20%) and salt contents, insignificant carbon deposits, reduced matrix effects, and better analytical performance. External calibration using either the solid reference material NIST 610 glass or aqueous standard solutions in combination with an indium internal standard provides accurate results. This calibration strategy offers a solution to the lack of a multi-element certified wine reference material for matrix-matched calibration. Twenty elements (Li, B, Mg, Al, V, Mn, Co, Cu, Zn, Rb, Sr, Y, Cs, Ba, La, Ce, Pr, Nd, Pb, and U) were determined in the wine samples. The proposed method was validated by a comparison with the conventional solution nebulization ICPMS method, with satisfying results. The detection limits for these elements were 0.01–1 ng mL−1. The proposed method also has great potential for multi-element analysis in other beverages. [ABSTRACT FROM AUTHOR]

Variations of the stable Ca isotopic compositions (noted as δ44/40Ca relative to the SRM915a standard) of basalts are interpreted as effects of mantle sources. Mantle pyroxenites are a minor but integral part of the mantle and, as fusible components, they are important source rocks to understand chemical and isotopic heterogeneity in mantle-derived magmas. However, the effect of pyroxenites on the Ca isotopic composition of the mantle has been poorly constrained. To which extent mantle pyroxenites and their formation processes such as melt-peridotite reaction, particularly involving recycled crustal materials, lead to heterogeneity in δ44/40Ca of the mantle is unknown. Here, we report δ44/40Ca of different types of pyroxenites (spinel pyroxenites, garnet pyroxenites, and phlogopite-bearing spinel clinopyroxenites) and minerals separates, along with surrounding peridotites from Hannuoba xenoliths, North China Craton to address the issue. Initial 87Sr/86Sr ratio indicates that recycled crustal materials were incorporated into parental magmas of garnet pyroxenites (0.70391–0.70715) and phlogopite-bearing clinopyroxenites (0.7142–0.7149), consistent with previous conclusions from Sr-Nd isotopes. Overall, the δ44/40Ca of garnet pyroxenites ranges from 0.86‰ to 0.98‰ (average 0.90 ± 0.05‰, n = 10) and the host peridotites affected by the infiltrating melts from 0.87‰ to 0.93‰ (0.89 ± 0.04‰, n = 8). Each pair (n = 8) of garnet pyroxenite and host peridotite displays no measurable difference in δ44/40Ca. The spinel pyroxenites and phlogopite-bearing spinel clinopyroxenites also show similar δ44/40Ca (0.94 ± 0.06‰ and 0.98 ± 0.05‰, respectively). The indistinguishable δ44/40Ca among these different types of pyroxenites and surrounding peridotites suggest no obvious Ca isotope variations during silicate melt-peridotite interaction and fractional crystallization, even if recycled silicate materials were involved. These results indicate that the mantle source with variable proportions of pyroxenites in equilibrium conditions overall would show uniform δ44/40Ca. It implies that the basic magmas derived from such peridotite-pyroxenite source would display limited variations in δ44/40Ca, even if their radiogenic isotopes show strong heterogeneity. The conclusion is consistent with no systematic variations in the available δ44/40Ca of different basalt types such as DMM, EM1 and HIMU. However, garnets in mantle rocks of recent work and this study generally display heavier δ44/40Ca than co-existing clinopyroxenes, implying that melts generated by partial melting of mantle sources with abundant residual garnets may show lighter δ44/40Ca values than MORBs. [ABSTRACT FROM AUTHOR]

Determination of gold abundances in natural rock is critical for applications, but very challenging. Here, we report a method for determining gold with a very low mass fraction (> 0.01 ng g−1) in rocks. The method involves Carius tube digestion with reverse aqua regia, chromatographic separation to remove most of the sample matrix and measurement by high‐sensitivity ICP‐MS. The mono‐isotopic element gold was quantified by external calibration using an internal standardisation of gold to platinum that was precisely determined by isotope dilution. The method is robust and the obtained results are indistinguishable (< 5–10%, 2s) from those independently obtained by a standard addition technique on the same solution. The results from reference materials TDB‐1 and GPt‐2 are consistent with the certified values and those determined by HF‐aqua regia digestion, confirming the validity of the method. TDB‐1 (n = 20), GPt‐2 (n = 6), BHVO‐2 (n = 9) and other mafic RMs are homogenous for gold (10–20%, 2s) at the 2 g test portion level; however, sample heterogeneity affects some RMs. Gold and platinum‐group elements also display different extents of sample heterogeneity for different RMs. Given the homogeneity observed for TDB‐1, GPt‐2 and BHOV‐2, they are recommended as well‐suited RMs for inter‐laboratory comparison studies of gold. [ABSTRACT FROM AUTHOR]