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Here, we provide the correct glass transition temperatures for 10°C/min cooling/heating rate-treated samples. Corrigendum to "A tetrad effect in the glass transition of lanthanide-doped sodium disilicate glasses" (J. Am. Ceram. In our paper "A tetrad effect in the glass transition of lanthanide-doped sodium disilicate glasses", rather than plotting values for the glass transition (T SB g sb ) for a matched cooling/heating rate of 10°C/min (as stated in that paper), we erroneously plotted values for the glass transition (T SB g sb ) of first calorimetric runs on glasses "as synthesized" with unknown thermal history (i.e., cooling rate). [Extracted from the article]

This paper reports two types of basalt that have different ages (Carboniferous and Permian) but occur next to each other in the northern part of the Changning–Menglian accretionary wedge, southwestern China. We use the geochronology and geochemical data to evaluate the tectonic evolution of the Palaeo‐Tethys during this period. Zircon grains from the mafic‐ultramafic rocks associated with the Permian basalts in the Xiaomengtai area yield a U–Pb age of 281 Ma and εHf(t) values from +9.2 to +12.8. The Permian mafic‐ultramafic rocks and the associated basalts are all characterized by normal mid‐ocean ridge basalt (N‐MORB)‐like chondrite‐normalized rare earth elements patterns, moderately negative Nb‐Ta anomalies in the mantle‐normalized immobile incompatible trace element patterns, and positive εNd(t) values from +4.2 to +6.5, which are consistent with the geochemical characteristics of mafic‐ultramafic rocks in supra‐subduction zone (SSZ)‐type ophiolite. On the contrary, the Carboniferous basalts, which are associated with marine carbonates, are characterized by light REE enrichments, slightly positive Nb‐Ta anomalies, and εNd(t) values from +2.8 to +4.0. These features are similar to those of typical oceanic island basalts (OIBs) worldwide. Modelling results using REEs show that the parental magmas for the Carboniferous OIBs and the Permian basalts were likely derived from mantle peridotites at the depths of garnet and spinel stability, respectively, consistent with the formation depth of these two different types of basalt globally. The occurrence of these two different types of mafic‐ultramafic rocks with significantly different ages in the same area supports the view that they are the remnants of the accreted Palaeo‐Tethys oceanic crust. The Carboniferous OIBs are considered to be parts of an OIB‐carbonate seamount chain that originally formed in the southern part of the Palaeo‐Tethys. The Permian mafic‐ultramafic rocks are regarded as fragments of SSZ‐type ophiolites that were present in the northern part of the Palaeo‐Tethys. These different pieces of oceanic crust were accreted to the Simao–Indochina continental Block by subduction between the Late Permian and the Triassic. [ABSTRACT FROM AUTHOR]

The Zhaojinggou Nb–Ta deposit is one of large rare metal deposits newly discovered in the northern margin of the North China Craton in recent years. This paper reports petrography, petrochemistry, columbite‐group minerals U–Pb chronology study of the amazonite granitic pegmatite (AGP) exposed in this deposit, and composition of columbite‐group minerals and biotite are obtained by electron probe microanalyzer and LA‐ICP‐MS. Eighteen analyses of columbite‐group minerals yielded weighted mean 206Pb/238U age of 116.9 ± 1.4 Ma. The crystallization temperature of biotite is 630–650°C, and the oxygen fugacity is 10−17–10−18 bars. The biotite has low MgO contents and high Rb, Rb/Sr, and FeOT/(FeOT + MgO) ratios. The AGP has extremely low MgO, Cr, Co and Ni contents, with Nb/Ta ratios range from 1.63 to 9.05 and Rb/Sr ratios range from 303.30 to 648.90, and obvious 'M' type tetrad effect of rare earth element indicating that the formation of the AGP is related to crust‐derived magma. The contents of Nb2O5 and FeO decrease, while the Ta2O5 and WO3 contents, Mn# and Ta# values increase gradually from the core to the rim of columbite‐group minerals. Some columbite‐group minerals have unobvious oscillatory zoning, and some have a clear bright zoing with high Ta contents on the rim, indicating that the genesis of Zhaojinggou Nb–Ta deposit is mainly magmatic crystallization differentiation, accompanied by hydrothermal autometasomatism in the late stage. [ABSTRACT FROM AUTHOR]

Shortly thereafter, in the wake of the "plate tectonics revolution" and working with Alan White, Ross noted the striking similarity between the average composition of the continental crust and andesite - one of the most diagnostic igneous rock types formed in subduction zones (Taylor & White, 1965). Stuart Ross Taylor, always known by his middle name Ross, was born in Ashburton, New Zealand, on November 26, 1925, and died peacefully in Canberra, Australia, on May 23, 2021, at the age of 95, surrounded by his wonderful and loving family. Brian was Goldschmidt's last student in Oslo (but finished his own Ph.D. in Stockholm due to the invasion of Norway) and Ross was always proud of the direct academic lineage to Goldschmidt (as are Ross's students and their students). In 2006, he led the famous Taylor Clan (Ross - Father; Larry - Son; Jeff - Holy Ghost) in an important paper: I The Moon: A Taylor perspective i (informally called Taylor-cubed). [Extracted from the article]

This paper presents a survey of geological attributes on the lateritic‐bauxitic deposits to examine their provenance, palaeogeography, and palaeoclimate condition in the Permian–Triassic boundary of Alborz Mountain, north Iran. The mineralogical analysis revealed that haematite, quartz, goethite, kaolinite, diaspore, boehmite, and anatase are the major rock‐forming minerals in these deposits. The major oxide composition of samples detected that enrichment of Al2O3 (up to 31.5%) and Fe2O3 (up to 37.9%) led to the formation of laterite, kaolinitic laterite, and bauxitic kaolinite. The distribution of trace and rare elements provides information about the enrichment of deposits concerning immobile elements. Employing geochemical proxies such as Al2O3/TiO2, bivariate diagrams of Eu/Eu* versus Sm/Nd and TiO2/Al2O3, enrichment of samples relative to heavy rare earth elements, and positive Eu anomaly revealed that the deposits originated from intermediate to mafic rocks. Several factors are inferred to be responsible for the transformation of parent rock(s) into lateritic‐bauxitic deposits: The high values of CIA, CIW, and PIA (mostly above 80) and increase of kaolinite point to deep to moderate parent rock(s) weathering, which is consistent with warming and humidity around the Permian–Triassic boundary. In continuation, transportation and trapping of weathered materials above the karstified carbonate bedrock of the Ruteh Formation and environmental interactions induced the formation of new minerals in a transitional environment near the vadose zone. The deposits have a generic correspondence with Palaeotethys Oceanic crustal subduction due to tectonic uplift, exhumation of bedrock, and regional sea‐level fall at the end of Palaeozoic that offered an opportunity for lateritization process. [ABSTRACT FROM AUTHOR]

This paper presents new zircon U–Pb–Hf isotopic and whole‐rock geochemical data for early Paleozoic–early Mesozoic igneous rocks from the Zhangguangcai Range, which are used to provide constraints on the petrogenesis and tectonic setting of these rocks and on the tectonic evolution of the eastern Songnen Massif. We dated five igneous rocks from the Zhangguangcai Range of the eastern Songnen Massif, namely, a late Cambrian (~489 Ma) syenogranite, a middle Silurian (~431 Ma) dacite, a Middle Triassic (~247 Ma) gabbro‐diorite and two Late Triassic (214–210 Ma) rhyolites. The late Cambrian syenogranite, middle Silurian dacite and Late Triassic rhyolites have high SiO2 and (Na2O + K2O) contents and low Mg# values. These four rocks are enriched in light rare earth elements (LREEs) and large‐ion lithophile elements (LILEs) but depleted in heavy REEs (HREEs) and high‐field‐strength elements (HFSEs). In addition, the εHf(t) values and TDM2 ages of zircons from these rocks range from −1.31 to +5.88 and from 1264 to 896 Ma, respectively. These data suggest that their primary magma was derived from partial melting of the juvenile mafic lower crust that was generated during the Mesoproterozoic–Neoproterozoic. The Middle Triassic gabbro‐diorite has low SiO2 and high MgO, Sc, Co, Cr and Ni contents and is enriched in LILEs and LREEs but depleted in HREEs and HFSEs such as Nb and Ta. Combining these features with the zircon εHf(t) values of the gabbro‐diorite, which range from +0.02 to +1.79, the primary magma of this rock is inferred to have been derived from partial melting of an isotopically depleted lithospheric mantle. The late Cambrian syenogranites and the middle Silurian dacites are weakly peraluminous and are classified as medium‐ to high‐K calc‐alkaline series, indicating that they formed in an active‐continental‐margin setting. The Middle–Late Triassic igneous rocks exhibit a bimodal igneous rock association, suggesting that they formed within an extensional environment. Combining our new results with previous findings, the early Paleozoic–early Mesozoic tectonic evolution of the eastern Songnen Massif is revealed. During the early Cambrian–early Silurian, the oceanic plate between the southern Songnen and southern Jiamusi massifs subducted westward beneath the Songnen Massif. The amalgamation between the southern Songnen and southern Jiamusi massifs occurred during the middle Silurian, and the southeastern Songnen Massif was in a post‐collisional extensional setting during the Devonian. During the late Carboniferous–Triassic, the Zhangguangcai Range was in an extensional environment, and the Mudanjiang Ocean started to open along the Jiayin–Mudanjiang Fault, separating the Songnen and Jiamusi massifs during the Middle–Late Triassic. [ABSTRACT FROM AUTHOR]

This paper discusses whole‐rock geochemistry, mineral chemistry, and platinum group element (PGE) systematics of depleted mantle rocks (harzburgite and dunite) from the northern part of Nagaland–Manipur Ophiolite (NMO), north‐east India, to comprehend their source features, fractionation behaviour of PGE during magmatic evolution, and its tectonic origin. The studied ultramafic rocks are characterized by a low concentration of CaO (0.57–0.71 wt%), Al2O3 (0.18–0.92 wt%) with ∑REE of 1.135–2.702 ppm and high concentrations of MgO (38.70–44.21 wt%), Cr (1,843–4,572 ppm), and Ni (894–4,138 ppm). They show U‐shaped REE patterns [LREE and HREE enrichment (La/Sm)N = 1.85–4.11, (Dy/Yb)N = 0.51–0.85]. Olivine ranges Fo 88.18 to Fo92.23, whereas Cpx and Opx range En44.84 to En47.89 and En86.37 to En93.37 respectively. The chrome spinel Cr# [Cr/(Cr + Al)] and Mg# [Mg/(Mg + Fe2+)] are 0.47–0.83 and 0.31–0.60, respectively, which indicates recrystallization from a boninitic magma in a Supra‐Subduction Zone setting. Conventional thermometry indicates the equilibration temperatures of the dunite sample yielded high temperatures of ~850°C, suggesting their formation due to later interaction with high‐temperature percolating melts. The PGE contents in harzburgite are low (125.6–142.8 ppb) as compared to the dunite (248–360 ppb). They have high PPGE/IPGE and negative Pt* (Pt/Pt* = 0.73) anomaly, which is characteristic of re‐entry of PPGE into the system via reaction with percolating basaltic melt in the mantle wedge. Significantly higher concentration of PPGEs than IPGEs in the samples, indicating recrystallization of PPGEs with early sulphide fractionation. The presence of significant Rh and Pd enhancements relative to Pt in all samples suggests that Pt was removed during PGE fractionation. This could be one of the reasons for both harzburgite and dunite's sulphide undersaturation. PGE distribution in NMO ultramafic rocks was therefore validated as being governed by sulphide saturation in parental magma and altered not only by partial melting but also by fractionation during their production in the Supra‐Subduction Zone environment. [ABSTRACT FROM AUTHOR]

Wear resistance is one of the essential properties of grinding media. Good wear resistance is the quality guarantee of preparing high‐purity ultrafine powder. This paper mainly studied the influence rule and enhanced mechanism of Sc2O3 on the wear resistance of Al2O3 ceramics. The relationship between Sc2O3 content and sintering properties, wear resistance, and microstructure of ceramics was studied. According to research findings, Sc2O3 could promote the densification of ceramics, improve the morphology of grain boundaries, enhance the binding force of grains, and increase the mechanical property of alumina grain. [ABSTRACT FROM AUTHOR]

The Woduhe area of Heilongjiang Province is located in the eastern side of the Greater Xing'an Range. This area has experienced the evolution of the Palaeo‐Asian Ocean, the Palaeo‐Pacific, and the Mongolia–Okhotsk Ocean, and it can be used to discuss the transformation process of these palaeo‐oceanic plates to continental plates. However, controversies exist over its time period and the process of transformation. The 1:250000 Woduhe Geological Map shows that Early Cretaceous granitic batholith developed near the Dajinshan area. However, the LA‐ICP‐MS zircon U–Pb dating presented in this paper shows that the trondhjemites from the southern part of the Dajinshan area were formed at 156.9 ± 2.2 Ma, syenogranites were formed at 131.7 ± 1.6 Ma, and diorite porphyrite dikes were formed at 126.0 ± 3.1 Ma. Therefore, Early Cretaceous batholiths should be reclassified as different, separate units. The Late Jurassic intrusive rocks belong to TTGG assemblages (tonalite–trondhjemite–granodiorite‐granite). Trace element spider diagrams show that the rocks are enriched in K, Pb, Zr, and Hf; depleted in Nb, Ta, and Eu; with higher Sr; and lower Y content. The rare earth element pattern is right‐sloping (La/Yb > 12). The Early Cretaceous intrusive rocks belong to G assemblages (granodiorite). Combined with the tectonic settings, we determined that the Late Jurassic and the Early Cretaceous granites were formed in a magmatic arc setting related to subduction. Late Jurassic intrusive magma mainly originated from the partial melting of the thickened lower crust under the Xing'an arc, and was likely contaminated by mantle material. Early Cretaceous intrusive magma originated from the partial melting of the Xing'an sub‐arc crust. Based on the distribution of the Late Jurassic TTG (N and NE) and G (S and SW) assemblages, intrusive records of the southward and southwestward subduction of the Mongolia–Okhotsk Ocean can be observed. In addition, the grade of maturity of the Xing'an arc is increasing during Late Jurassic to Early Cretaceous. [ABSTRACT FROM AUTHOR]

Hainan Island is a key part of the eastern Tethyan region and contains detailed geological information that can enhance our understanding of the tectonic evolution of this region since the late Palaeozoic. In this paper, we report geochronological, geochemical, and Sr–Nd isotopic data for granitoids from Baomei and Chahe in the northern part of Hainan Island. Three new zircon U–Pb ages of 243.3 ± 1.7 Ma, 237.1 ± 5.1 Ma, and 257.0 ± 4.0 Ma were obtained for these granitoids. The late Permian Chahe granite (257 Ma) is weakly peraluminous to peraluminous, and has rare earth element patterns and Ga/Al and FeOT/MgO ratios typical of A‐type granites formed in an extensional tectonic setting. The Middle Triassic Baomei granitoids (243–237 Ma) are weakly peraluminous, and exhibit a negative correlation between P2O5 and SiO2, which is typical of I‐type granites. All the granitoids have EM II‐type‐enriched mantle Sr–Nd isotopic compositions, which indicate that they were derived from a mantle source that had experienced enrichment and metasomatism. Hainan Island was in an extensional tectonic setting from the late Permian to Middle Triassic when widespread A‐ and I‐type granites were generated. We speculate that Hainan Island was mainly affected by the Tethyan tectonic domain during the Permian–Triassic, which involved closure of the Palaeo‐Tethys Ocean, collision of the Indochina and South China blocks, and subsequent post‐collisional extension. [ABSTRACT FROM AUTHOR]

Although progress has been made in defining and explaining the temporal and spatial distributions of Neo‐Tethyan magmatism in the Tibet–Himalaya region, the correlation of magmatic suites in the SE Tibetan Plateau remains poorly constrained. This paper reports zircon U–Pb dating, geochemistry, and Sr–Nd isotope compositions of a concealed gabbroic unit (coverage area of >6.0 km2) in the southern Lancangjiang tectonic zone, western Yunnan, SW China. Zircon 206Pb/238U ages of 143–133 Ma indicate that the unit formed during the Early Cretaceous (ca. 139.7 Ma). The gabbro samples have variable MgO (7.88–16.1 wt%; Mg# = 58–74) and relatively low TiO2 (0.76–1.24 wt%) and total‐alkali (K2O + Na2O = 2.61–4.06 wt%) contents. The samples exhibit weakly fractionated rare earth element (REE) patterns with slight depletion in light REEs and negligible Eu anomalies. In a primitive‐mantle‐normalized element‐variation diagram, the gabbros, display variable enrichment in large‐ion lithophile elements and relatively flat patterns of high‐field‐strength elements. Initial 87Sr/86Sr ratios of 0.7079 to 0.7142 and relatively depleted εNd(t) values of +3.96 to +4.84 are similar to those of the mantle source of back‐arc basin basalts (BABBs) in the central Lhasa Block and mid‐ocean ridge basalt in the Indus–Tsangpo Suture Zone. These various characteristics suggest that the gabbroic unit was derived from a shallow and depleted mantle source by relatively high‐degree partial melting in the spinel stability field. The parental magma underwent slight crustal contamination, as well as fractional crystallization of clinopyroxene. The studied gabbros have distinct BABB‐type geochemical affinities similar to those of the Okinawa BABB. Combining our data with the coeval occurrence of a continental rift basin (the Simao–Lanping Basin) leads us to suggest the existence of a back‐arc rifting setting in the SE Tibetan Plateau during the Jurassic–Cretaceous. This setting can also be geochronologically and genetically correlated to the back‐arc basin developed within the Lhasa Block. These settings and constituent characteristics formed as a result of Neo‐Tethyan oceanic slab subduction during the late Mesozoic. [ABSTRACT FROM AUTHOR]

Due to strong anti‐poisoning ability, good emission stability, high emission current density, lanthanum hexaboride (LaB6) and cerium hexaboride (CeB6) have been maturely applied in electron emission emitter. In this paper, a new manufacturing method for LaB6 (or CeB6) powder was proposed by using La2O3 (or CeO2), B4C, and Al as raw materials. After high‐temperature reaction in the range of 1673–1773 K and the following alkaline leaching at 90°C, LaB6 or CeB6 powder with particle size of about 10 μm was obtained. Furthermore, by Al metal flux method, the obtained powder was used to manufacture single crystal block with size of several millimeters. [ABSTRACT FROM AUTHOR]

The Kelameili Ocean was one branch of the Palaeo‐Asian Ocean, the initiation and closure history of which remains elusive. Consequently, they hamper our understanding of the accretionary evolution of the southern Altaids. In this paper, we carried out field mapping and also geochronological and geochemical analyses on the Huangcaopo Group in the northern Harlik Mountains, NW China. Field investigation revealed that "block‐in‐matrix" structure develops with blocks of andesite, limestone, sandstone, and gabbro in matrices of turbidites. Combined with our recent work, our field investigation indicates that the Huangcaopo Group is the southern extension of the Kelameili accretionary complex. A gabbro block (19HAM057) was dated at 500 ± 4 Ma, its geochemical affinity was defined to be similar to arc magmatic rocks. Magmatisms represented by two gabbroic intrusions (19HAM057‐2 and 19HAM048) were dated at the latest Devonian (360 ± 5 Ma) and the latest Carboniferous (299 ± 4 Ma), respectively. Their geochemistry displays enrichments in light rare earth elements (LREE) and large ion lithophile elements (LILE), but depletions in high field strength elements (HFSE, especially Nb and Ta). And a younger gabbroic intrusion (19HAM052) yielded crystallization age of the latest Permian (254 ± 3 Ma), and its geochemistry also shows affinity to arc magmatism. The magmatism represented by the gabbro block (19HAM057) was coeval with the Zhaheba‐Aermantai ophiolite, indicating that it was the product of incipient arc magmatism following subduction initiation in the Kelameili branch of the Palaeo‐Asian Ocean. However, two episodes of gabbroic magmas (19HAM057‐2 and 19HAM048) that intruded the Kelameili accretionary complex from the latest Devonian to latest Carboniferous indicate southward rollback of the subducting Kelameili oceanic lithosphere and resulted in the development of a growing arc. Meanwhile, the youngest gabbroic intrusion (19HAM052) suggests that northward subduction of the Kelameili oceanic lithosphere may have at least lasted to the latest Permian, indicating that the closure of the Kelameili Ocean might have been later than the latest Permian, most likely in the early Triassic. Our new data provide further constraints on the initiation and closure history of the Kelameili Ocean, which shed light on the accretionary evolution of the Altaids. [ABSTRACT FROM AUTHOR]

Geochemical data for 435 samples of the Pliocene to Quaternary (P–Q) volcanic rocks from Iran, distributed mostly along a NW–SE trending belt, were compiled from 28 papers (12 written in Persian). Until now, the rock nomenclature employed has been inconsistent with the recommendations of the International Union of Geological Sciences (IUGS). Moreover, older bivariate and ternary tectonic discrimination diagrams and only traditional qualitative approaches using Nb and Ta anomalies, have been used to understand the origin and evolution of the P–Q magmas. The P–Q magma and rock types were classified by strictly following the IUGS recommendations. Two geochemometric multidimensional models based on 10 and 16 elements, along with two decision procedures, capable of discriminating 29 fine tectonic settings, were used to document the existence of six tectonic settings in Iran during the P–Q. The rare earth elements indicated that the evolved intermediate and silicic rocks had a significant crustal component in their origin. The quantification of Nb and Ta anomalies in multielement diagrams was used to support the tectonic inferences from the multidimensional geochemometric models. [ABSTRACT FROM AUTHOR]

The study of the palaeoenvironment of the Early Cretaceous has been a significant research topic, largely due to the "Jehol Biota" in western Liaoning and the important prospect of fossils in Dakangpu Layer. Based on the sedimentology of Dakangpu Layer, it is helpful to get a deeper understanding of the living environment of the "Jehol Biota." Varves are highly developed in the Dakangpu Bed of lower Cretaceous Yixian Basin in western Liaoning, China, supplying reliable and high‐quality proxies to explore the palaeoclimate. This paper reconstructs the palaeo‐lake environment and palaeoclimate, using petrography, facies associations, varves components, and geochemistry. Detailed petrographic studies helped to recognize 11 lithofacies which were grouped into two facies associations: Shallow lake and deep to semi‐deep lake sequences. The delicate structure of varves in the Dakangpu Bed were divided into two categories: Clastic and endogenic. Additionally, two sub‐types of clastic varves have been discovered, with distinct components, thickness, and distribution in vertical sequence. Nineteen representative samples of varves reveal that rare earth and trace elements have a similar change trend. The composition, formation, and preservation of the varves in the Dakangpu Bed depicted a deep lake, with stratified water and oxygen‐depleted bottom layer environment. The U/Th ratios and V/Cr ratios are in the ranges of 0.37–1.55 and 0.97–10.47 respectively, supporting the redox environment's minor fluctuation. The varve thickness, flood frequency, sporopollenin collections, and geochemical data indicated that precipitation and humidity decreased gradually in the sedimentary period, and the climate changed to warmer and drier, with fluctuations in the middle to later periods. [ABSTRACT FROM AUTHOR]

This paper studies the major, trace, and rare earth elements (REEs) in fluvial sediments from the Yarlung Zangbo River (YZR) on the Tibetan Plateau, China, with the aim of investigating their provenances, sediment maturity, weathering conditions, and tectonic settings. All samples and analytical techniques are based on Environmental Geochemical Monitoring Networks, which are a crucial part of IGCP259/360 (Global Geochemical Baseline). The results show that the YZR sediments consist of greywacke and litharenite with low‐moderate maturities of textures and minerals. The chemical index of alteration (CIA) (49–71), plagioclase index of alteration (49–77), and index of compositional variability (ICV) values (0.82–1.54) indicate that both mature and immature sediments are present in the YZR and have experienced weak to moderate weathering with little intense weathering in the source area, which is also confirmed by the ICV‐CIA, A‐CN‐K, A‐CNK‐FM, and MFW plots. Moreover, the provenance discrimination diagrams suggest that the YZR sediments are predominantly derived from felsic rocks that are close to the upper continental crust and from acid intermediates, and the tectonic settings of the YZR source rocks were associated with active continental margins and continental island arcs. The overall sediment types, weathering conditions, and tectonics of the YZR were consistent with those of the Brahmaputra River and Meghna River during the Himalayan–Tibetan orogeny, while the sediments of the Brahmaputra River are characterized by recycled‐quartzose sources when compared with the other two Himalayan rivers due to the contributions of quartzolithic composition. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) is one of the largest accretionary orogenic collages in the world with prominent juvenile crust addition, where the southernmost margin of the CAOB located is one hot topic in the international studies. The Dunhuang Block located to the south of the Beishan Orogen is a key position for outlining the tectonic framework of the south margin of the CAOB. However, at present, the tectonic attribution of the Dunhuang Block is still controversial. In this paper, we focus on the origins and protoliths of the meta‐mafic rocks from the Hongliuxia complex in the southern Dunhuang Block for determining the tectonic attribution of the Dunhuang Block. In the field, the meta‐mafic rocks are mainly exposed as tectonic blocks within the metasedimentary rocks displaying the "block‐in‐matrix" fabrics or as tectonic slices juxtaposed by faults. Geochemically, the meta‐mafic rocks could be divided into three groups based on the rare earth elements (REE) and trace elements: the group 1 samples are depleted in the LREE relative to HREE and show flat HREE patterns, similar to the mid‐oceanic ridge basalt; the group 2 samples show flat REE patterns without obvious differentiation between the LREE and HREE, like the oceanic plateau basalt; the group 3 samples are enriched in LREE relative to LREE, and have negative Nb, Ta, and Ti anomalies, similar to the island arc basalt. Conclusively, the protoliths of the meta‐mafic rocks dominantly belong to the oceanic plate components. They were metamorphosed during Early Silurian to Middle Devonian in different depths of the subduction zone documented in previous studies. So, we suggest the Hongliuxia complex is an exhumed Palaeozoic subduction–accretion complex (SAC) formed during the oceanic plate subduction. This result confirms the Palaeozoic subduction event occurred in the Dunhuang region and indicates that the Dunhuang Block is a Palaeozoic Orogen rather than a part of Precambrian continent block. Considering the regional geology context, we speculate the Dunhuang Orogen belongs to the southernmost margin of the CAOB. [ABSTRACT FROM AUTHOR]

The Kelameili suture located between the eastern Tianshan Junggar Plate and the Harlik island arc in east Tianshan. This suture is well known as identifying the Kelameili ophiolite and the Tucker Takezale ophiolitic melange. This paper first reports a new discovery of the Shihuiyao ophiolite, which is 70 km away from the Takezale ophiolitic mélange to the east. It is mainly composed of the variable serpentinized peridotite, metagabbro, and minor siliceous rocks. The serpentinite and gabbros are characterized by high content of Al2O3 and normal mid‐ocean ridge basalt (N‐MORB)‐type rare earth element compositions. These rocks also show a typical characteristic of origin of island arc setting with depletion of high‐field strength element (HFSE) and enrichment of large‐ion lithophile element (LILE). The LA‐ICP‐MS dating of zircon grains from gabbros gave a weighted mean 206Pb/238U age of 352 Ma, which was interpreted to represent the age of the Kelameili Ocean. This paper provided an important constraint on the tectonic evolution of the Kelameili Ocean. [ABSTRACT FROM AUTHOR]

The Lower Jurassic clastic rocks in the Qiangtang Basin, northern Tibet, are generally regarded as the early sediments of the new Mesozoic Qiangtang Basin (Late Triassic to Early Cretaceous). However, little attention has been paid to the palaeoenvironment, provenance, and tectonic setting of this unit. The QZ‐16 well, located in the east of the northern Qiangtang Basin, firstly recovered the Lower Jurassic strata (Quemo Co Formation) in the Qiangtang Basin. In this paper, the whole‐rock major‐trace elemental characteristics of 34 mudstone samples and detrital zircon geochronology of one sandstone, collected from the Quemo Co Formation of the QZ‐16 well, are reported in order to infer the palaeoenvironment, provenance, and tectonic setting. Quemo Co mudstones are dominated by SiO2 and Al2O3, while Fe2O3, CaO, K2O, and MgO are the second most abundant oxides. They are generally characterized by high REE concentrations, enrichment in light rare earth elements (LREEs), marked negative Eu and Ce anomalies. The REE contents of the mudstones are mainly controlled by terrigenous detrital minerals input. The Lower Jurassic mudstones have relatively high chemical index of alteration (79.1–83.6) values, indicating moderate to high degree of chemical weathering conditions of the source area. Sr/Ba and Rb/K ratios reflect that the marine transgression impact was limited and the mudstones were generally deposited in a brackish water environment. Major, trace, and REE contents indicate that the mudstones were mainly derived from intermediate igneous rocks with subordinate felsic igneous rocks. Prominent age peaks at ca. 200 ~ 400 Ma, 700 ~ 970 Ma, 1,700 ~ 1,900 Ma, and 2,100 ~ 2,700 Ma of the detrital zircon grains suggest that the Lower Jurassic clastic rocks were derived from the Central Qiangtang and Songpan–Ganzi complex. Moreover, tectonic discrimination diagrams based on major and trace elements show that the source of the Lower Jurassic sediments were most likely derived from a collision tectonic setting. [ABSTRACT FROM AUTHOR]

Some of the poorest people in the world's poorest countries eke out a living in artisanal and small‐scale mining (ASM). Equipped with primitive tools like picks, shovels, buckets, and gold pans, they work mining valuable resources, like gold, diamonds, tin, lithium, rare earth elements, tantalum, and cobalt, and any other usable commodity, for example, sand, coal, or mica. The mining and refining processes are labor intensive and associated with a variety of health problems due to accidents, overheating, overexertion, dust inhalation, exposure to toxic chemicals and gases, violence, and illicit and prescription drug and alcohol addiction. Evident disadvantages with ASM are counterbalanced by the immense economic benefits. For many, the true scope and scale of ASM activities are unappreciated, along with the unknown health and societal impacts. Here, we set out to elucidate the scope of ASM beyond the recovery of familiar commodities, such as gold and diamonds. We adopt a holistic perspective toward health impacts of ASM, which includes unique occupational, environmental, and human/social drivers. A particular focus is poverty as a health risk with artisanal miners. They are commonly poverty‐stricken people in poor countries, ensnared by a variety of poverty traps, which take a toll on the health and well‐being of individuals and communities. ASM sometimes provides an opportunity to diversify income in the face of a decline in subsistence agriculture. However, ASM often trades one kind of generational poverty for another, coming along with serious health risks and turmoil associated with work in an informal "cash‐rich" business. Plain Language Summary: Many of the world's most valuable commodities, for example, gold, diamonds, and strategic metals, and less valuable resources, for example, sand, clay, and coal, are the products of artisanal and small‐scale mining (ASM). The miners are commonly poor people with rudimentary tools, like shovels, buckets, and pans subsisting by working shallow ore deposits. Although an inefficient mining method, the large numbers of people can contribute substantially to a country's total production. Much of this mining occurs in distant, lawless areas like the Amazon River basin or the outback in the Democratic Republic of Congo. The work is grueling and dangerous because of violence and unregulated work sites. Miners suffer from the expected collection of occupational health risks, due to, for example, accidents, chemical exposures, dust inhalation, and lifting and lugging of heavy loads. Mining communities are at risk from incidental exposures to mercury, mosquito‐borne diseases, poor sanitation, and more. Human and social problems also impact health. Our paper emphasizes poverty as a risk factor for disease, as miners are caught in poverty traps—unable to leave. Injuries and disease often must remain untreated because of costs and absent clinics. Key Points: Artisanal and small‐scale mining (ASM) is primitive with health problems determined by occupational, environmental, and social settingsASM involves 80 + countries and valuable resources, like gold, diamonds, precious stones, tantalum, tin, tungsten, and commoditiesGrueling work, poverty, illegalities, and worksites located in remote and medically underserved areas contribute to poor health [ABSTRACT FROM AUTHOR]

The Mahanadi river basin (MRB) is one of the eight major fluvial basins of India. This paper presents a very first systematic study of geochemical characteristics, including rare earth elements of surface sediments collected from the riverbed at different parts of this basin to infer the chemical weathering, provenance, and tectonic settings. Lower mean values of major elements (except for SiO2 and K2O) are observed compared with that of the upper continental crust (UCC). It is attributed to the dominance of quartz and orthoclase in sediments and removal of mobile elements from the sediment during the transportation. The concentrations of Rb, Ba, Cu, Th, and Pb are elevated with respect to the UCC. The higher concentration of K2O and Rb, the ratio of Al2O3 to TiO2, and other bivariant plots indicate that the sediments are derived mostly from acidic to intermediate igneous rock. Majority of the sediments have geochemical similarity with the arkose and litharenite sandstones. The chemical index of alteration (CIA) values of the MRB sediments varies between 52 and 69 with most of the samples having CIA < 60 suggesting the lower degree of weathering which is further supported by the mineralogy. The eroded sediments have compositional maturity comparable to sediments deposited under semi‐arid climatic conditions. Sediments show both positive and negative Eu anomalies based on the source rock. Based on the commonly used discrimination diagrams, it is concluded that the MRB has a tectonic setting similar to the passive continental margin. [ABSTRACT FROM AUTHOR]

The relationship between the Shangdan and Erlangping suture zone (ESZ) and the initiation stretch time of the Early Paleozoic back‐arc system in the Qinling Orogen still remains unclear. This paper reports the chronological and geochemical data of the Miaogou mafic intrusion along the southern margin of the Shangdan suture. The pyroxenite in the mafic intrusion has a zircon U–Pb age of 485 ± 5 Ma (Mean Standard Weighted Deviation (MSWD) = 0.08, n = 18). It has low SiO2 (45.41–46.02 wt%), K2O (0.42–0.44 wt%), and TiO2 (0.73–0.83 wt%) contents, high MgO (13.9–15.13 wt%) contents with high Mg# (74–77). In combination with its high clinopyroxene portion, the pyroxenite represented the accumulates from the mafic magma. Some sieve rims of the clinopyroxene indicate that the primitive pyroxenite was metasomatized by subduction‐related fluids. However, their consistent trace element and rare earth element (REE) patterns suggest that the metasomatism process has insignificant effects on their geochemical features. Zircons from the pyroxenite have positive εHf(t) (+7.18 to +11.75) values, reveal a depleted source region. In combination with its high V (322–1,093 ppm) contents, low Ti/V (10–15) ratios and smooth REE patterns, we propose that the pyroxenite was derived from metasomatized depleted mantle wedge in a back‐arc basin. In considering the duration limit (<475 Ma) of the back‐arc basin along the ESZ, we argued that the ~485 Ma Miaogou pyroxenite represented the initiation back‐arc basin in the Shangdan suture, which might represent the initial rifting of the North Qinling microcontinent induced by the northward subduction of the Shangdan Ocean. [ABSTRACT FROM AUTHOR]

The Early Cretaceous Shengli River–Changshe Mountain marine oil shale belt, located in the northern Qiangtang Basin, Tibet, is estimated to be the largest marine oil shale resource in China. However, its palaeoweathering, provenance, and tectonic setting during the depositional history have received little interest. In this paper, 19 outcrop marine oil shale samples from the ChangsheMountain (CSM) area were studied to investigate the provenance, palaeoclimate, palaeoweathering, and tectonic setting during the marine oil shale deposition. The total organic carbon and organic sulphur contents of the CSM oil shales range from 2.2% to 13.44% and 0.19% to 1.08%, respectively. The CSM oil shale samples contain abundant carbonate (e.g., calcite and dolomite), quartz, and clay minerals. The clay minerals of the CSM oil shale samples is dominated by illite and then by smectite. Other minerals, including haematite, apatite, pyrite, baryte, and celestite, were also identified by scanning electron microscope–energy‐dispersive X‐ray spectrometer. The total rare earth element (∑REE) contents of the oil shales range from 9.01 to 105.96 ppm (average 57.56 ppm), close to the average REE contents of U.S. coals. The REE contents in oil shale samples are mainly controlled by terrigenous input. The CSM oil shales show LREE‐enriched, HREE‐depleted, with the LREE/HREE ratios ranging from 5.12 to 10.18, negative Eu anomalies (0.56–0.84) and slightly negative Ce anomalies (0.87–1.05). The chemical index of alteration values of the CSM oil shales range from 67 to 76 (average 73), indicating a moderate chemical weathering condition. Sr/Cu and Rb/Sr ratios suggest the CSM oil shales were mainly deposited under a warm and humid climate regime. Sr/Ba ratios, ranging from 0.54 to 7.84, suggest a palaeoenvironment with fluctuant salinity. Major element, trace element, and REE relationships indicate that the CSM oil shales are mainly from the felsic and intermediate igneous rocks. The REE distribution patterns of the CSM oil shales are similar to the Late Triassic Nadi Kangri felsic volcanic rocks in the Qiangtang Basin, indicating that the CSM oil shale may be derived from the Late Triassic volcanic rocks and the oil shales were mainly formed in rift tectonic setting. Favourable preservation condition (e.g., warmer palaeoclimate, higher palaeosalinity, and dysoxic to anoxic water column environment) could be the main controlling factor for organic matter accumulation. [ABSTRACT FROM AUTHOR]

Miocene postcollisional potassic and adakitic rocks are widely distributed in the southern Lhasa terrane and western central Lhasa terrane. However, coeval potassic and adakitic rocks in eastern central Lhasa terrane were rarely recognized, and their origins and formation mechanism remain controversial. In this paper, we provide new geochronological and geochemical data for the Miocene postcollisional potassic and adakitic intrusions exposed in the Qingdu area, eastern central Lhasa terrane, southern Tibet. The Qingdu Miocene intrusions consist of quartz monzonite porphyry and biotite granite with coeval zircon U–Pb ages of 14.1 Ma and 14.0 Ma, respectively. They have high SiO2 (67.98–75.32 wt.%), Al2O3 (14.13–14.78 wt.%), and K2O (4.06–6.18 wt.%) and low MgO (0.25–1.46 wt.%) contents. They are both enriched in light rare earth elements (LREEs) and depleted in heavy rare earth elements (HREEs), with high (La/Yb)N (25.37–42.32) ratios. The biotite granite samples have low Y (7.10–9.96 ppm) and Yb (0.61–0.85 ppm) contents, and high Sr (229–384 ppm) contents and high Sr/Y (30–41) ratios, which show adakitic geochemical characteristics, whereas the quartz monzonite porphyry samples show potassic geochemical characteristics. They display initial (87Sr/86Sr)i ratios of 0.7083–0.7103, εHf(t) values of −6.7 to −0.1, εNd(t) values of −8.96 to −7.44, (208Pb/204Pb)i ratios of 39.028–39.110, (207Pb/204Pb)i ratios of 15.662–15.684, and (206Pb/204Pb)i ratios of 18.541–18.577. These signatures indicate that both the potassic and adakitic intrusions are more likely to originate from partial melting of a thickened lower crust, which were mainly the products of the binary mixing between the juvenile and ancient crust components. Based on the spatial distributions and isotopic features of the postcollisional potassic and adakitic rocks in the Lhasa terrane, we suggest that the differences of the lower crustal composition played a crucial role in causing the geochemical variations of the Miocene postcollisional adakitic and potassic rocks in Lhasa terrane. [ABSTRACT FROM AUTHOR]

The Devonian volcanic rocks are widely distributed in the East Junggar (Xinjiang, NW China), preserving important magmatic records for investigating Palaeozoic tectonic evolution. The Beitashan Formation is mainly composed of pyroclastic rocks and sedimentary rocks in the lower section and intermediate–basic volcanic lava and pyroclastic rocks in the upper section. In this paper, we present geochronological, geochemical, and in situ Lu–Hf isotopic data for Beitashan Formation volcanic rocks from the East Junggar. Zircon U–Pb analyses from a basalt sample by laser ablation inductively coupled plasma mass spectrometry yielded a weighted mean age of 387.8 ± 4.5 Ma, indicating that it was generated in the Middle Devonian. The basic–intermediate volcanic rocks are tholeiitic to calc‐alkalic and are characterized by MgO (2.29–5.91 wt.%), low TiO2 (0.75–1.36 wt.%), and relatively high Al2O3 (15.82–16.73 wt.%). Furthermore, they display enrichment in light rare‐earth elements and large‐ion lithophile elements (such as Ba and Sr) and depletion in Nb, Ta, and Ti, along with slightly positive Eu anomalies (δEu = 0.83–1.15) and Ce anomalies (δCe = 1.00–1.11). In addition, in situ zircon Hf isotopic analyses from basalt samples show εHf(t) values ranging from +4.33 to +15.2, indicating a depleted mantle source with minor crustal contamination. They also show relatively low Nb/Zr (0.04–0.06), Th/Yb (0.67–3.83), and Ba/La (6.79–67.53) and high Ce/Th (7.71–18.94), Ba/Rb (21.39–294.28), and Ba/Th (31.42–486.58). The geochemical data suggest these rocks were likely derived from 10% to 30% partial melting of a garnet‐rich with minor spinel‐bearing Iherzolite depleted mantle metasomatized by slab‐derived fluids, with crustal contamination. Combined with the geological setting and previous studies, we suggest that the northern East Junggar was in a northward‐subducted island‐arc setting in the Devonian. [ABSTRACT FROM AUTHOR]

Carboniferous magmatism in the Darbut region is critical for understanding the evolutionary history of the accretionary orogenesis of the West Junggar area in the Central Asian Orogenic Belt. In this paper, zircon U–Pb geochronological, whole‐rock geochemical and Sr–Nd–Pb–Hf isotopic analyses of the basalts, basaltic andesite, and dacite from the Carboniferous Tailegula Formation, Darbut region, have been performed. The magmatic zircons from basalt, basaltic andesite, and dacite yield concordia U–Pb isotope ages of 344 ± 4, 347 ± 3, and 340 ± 5 Ma, respectively, which are interpreted as the crystallization ages of these rocks. The basalts and basaltic andesite are characterized by an alkali composition; high Nb/Yb, Th/Yb, Ta/Yb, La/Sm, and Sm/Yb trace element ratios and Pb isotopic ratios; moderate (87Sr/86Sr)i ratios; low (143Nb/144Nb)i ratios; and positive εNd(t) (+0.66 − +4.73) and εHf(t) (+1.7 − +15.2) values. These characteristics indicate that the magmas were derived from mixed mantle sources, that is, enriched mantle sources and high U/Pb ratio mantle (HIMU) component sources with ≤10% partial melting of garnet and spinel lherzolite. The samples display pronounced light rare earth elements (LREEs) and incompatible element enrichment patterns with positive Nb–Ta anomalies and a high Pb content and Nb/La ratios but low (Th/Nb)N ratios and a lower degree of partial melting, implying that these rocks were formed in a continental extensional setting. Based on our results and that of previous studies, we conclude that the early Carboniferous volcanic rocks in the Darbut region formed by mantle plume or regional‐scale mantle upwelling in a continental extensional setting after closure of the Junggar Ocean. [ABSTRACT FROM AUTHOR]

This paper reports new zircon U–Pb ages and Hf isotopic compositions of felsic units of the Abor volcanic rocks (AVR) of Eastern Himalayan Syntaxis (EHS), Northeast India, and discusses their relationship to the Kerguelen plume activity. The AVR are bimodal and predominantly constituted by mafic rocks with minor felsic units. Mafic volcanics are identified as basalt and basaltic andesite with light rare earth elements (LREE) enriched and slightly depleted heavy rare earth elements (HREE) pattern without Eu anomalies. Low concentrations of LILE, high contents of Fe2O3, and other incompatible trace elements ratios reflect enriched nature of these mafic volcanics. Felsic volcanic rocks are dacitic to rhyolitic in composition, which have high REE content, high LREE/HREE, and pronounced negative Eu anomalies. Enriched LREE, high Th/Nb, Ce/Nb ratios, and variations in Rb/Zr, K/Rb, La/Sm ratios with negative anomalies of Ba, Nb, Sr, P, Ti in felsic rocks suggest substantial contribution of crustal contamination at the time of eruption. Zircons from felsic units yield an average U–Pb age of ~132 Ma and unradiogenic (ƐHf(t) < 0) Hf isotope values of −7.0 to −13.3 with model ages between 1.5 and 2.1 Ga, suggesting old crustal assimilation in their genesis. The AVR were emplaced in the continental rift tectonic setting, and depth of the magma source is confirmed as near spinel stability zone. The AVR are positively comparable with other flood basalts that were formed due to the Kerguelen plume activity. Therefore, our combined new geochemical and geochronological data show that the AVR were emplaced at early stage (~132 Ma) of eastern Gondwana breakup due to outbreak of the Kerguelen plume. This study thus supports the idea of the Kerguelen plume affecting a large area of Eastern India, Western Australia, and Antarctica during early stage of Gondwana breakup. [ABSTRACT FROM AUTHOR]

The use of rare earth elements (REE) in permanent magnets (PMs) raises problems in several domains. The supply chain of these is fragile, the prices have shown volatility and its manufacturing has a bigger impact on climate change when compared to the manufacturing of other PMs. Instead, ferrite PMs have been researched as an alternative. This alternative shows a relatively higher demagnetisation risk when compared to REE PMs. Thus, a detailed study on permanent demagnetisation during winding faults is crucial. The authors use the finite element method to evaluate different machine designs, developed under mechanical constraints, and explore several strategies to mitigate permanent demagnetisation. Also, the importance of avoiding permanent demagnetisation is changed gradually in the optimisation process. The results show that the protection of the PM and performance optimisation are irreconcilable goals. It also highlights the impact of the stator design in decreasing demagnetisation. Additionally, it is shown that the classic notion of avoiding demagnetisation is an ineffective strategy for designing high‐performance machines with ferrite magnets, and instead, it should be integrated into the optimisation process and weighted according to the application demands. [ABSTRACT FROM AUTHOR]

Major, trace, and rare earth element (REE) geochemistry of sediments from a tropical mountain river is investigated to understand the behavior of chemical elements during weathering and transportation in a Peninsular Gneissic terrain. The results from this study are compared with the Deccan Basalt‐derived River sediments and the eastern Arabian Sea sediments with an intent to highlight the challenges associated with the provenance determination of sediments along the continental margin of India. The geochemistry of suspended particulate matter (SPM) and mud sediments (<63 μm) of the Nethravati River indicate that sediments are derived from a relatively homogenous lithology, characterized by intermediate rocks of tonalitic (low‐Al TTGs) composition. The tectonic origin of the source rocks discriminated using sediment geochemistry suggests an ocean island arc origin. The sediments experience intense chemical weathering in the source region. The elemental composition and their inter‐element relationships suggest differential chemical weathering of mineral phases fractionate mafic components and their secondary mineral products in SPM, and mixed sources dominated by felsic components and their secondary mineral products in mud sediments. Intense chemical weathering induces significant geochemical splits among the suspended and mud sediments. The transport of mafic‐biased sediments from Peninsular India to Oceans, and the geochemical similarity with Deccan Basalt‐derived sediments makes it challenging to track the Peninsular Gneiss‐derived sediment provenance along the continental margin of India using conventional elemental geochemistry. The inferences from this study have important implications for determining the sediment provenance along the continental margin of India. Plain Language Summary: The focus of this study is to characterize the impacts of chemical weathering and hydrodynamic sorting on the chemical composition of river sediment along a river in Peninsular India. The Arabian Sea dominantly receives sediment from the Himalaya and Deccan Traps and thus other sources, like rivers draining Peninsular India, are overlooked as important sediment sources. However, the processes that govern river sediment chemistry in Peninsular India are not well characterized, which may lead to incorrect interpretations of sedimentary records in the Arabian Sea. To address this knowledge gap, the major and rare earth element (REE) compositions of river‐suspended sediment and mud sediments have been analyzed and compared with the sediment compositions of Deccan Basalt draining rivers and the sediments from the Indian Ocean. The composition of river‐suspended sediment differs from mud due to hydrodynamic sorting, where suspended sediment has a more mafic affinity and mud has a more felsic affinity. Moreover, the study shows that REE patterns in rivers with substantially different exposed bedrock types can be similar because of intense weathering, which complicates the interpretation of incompatible element patterns in geologic records. Key Points: Geochemical split among the granulometric grades of sediments observed in the Peninsular RiverFelsic‐biased coarser sediments and mafic‐biased finer sediments in the Peninsular Gneissic cratonic RiverGeochemical similarity among the Peninsular Gneiss derived finer sediments and Deccan Basalt‐derived sediments is observed [ABSTRACT FROM AUTHOR]

This paper presents UPb zircon dating and element compositions for Miocene intrusive rocks in NE Tafresh situated in the central Urumieh‐Dokhtar Magmatic Arc. These intrusive rocks, consisting of granodiorite and diorite, were emplaced during the Early Miocene (19.07–20.37 Ma), following extensive submarine volcanic activity in the Eocene. In normalized multi‐element diagrams, all the analysed rocks are characterized by enrichments in large ion lithophile elements (e.g., Ba, Rb, and Sr) and depletions in high field strength elements (e.g., Nb, Ta, and Hf) and display geochemical features typical of subduction‐related calc‐alkaline arc magmas. The enrichment of light rare earth elements and flat heavy rare earth elements patterns reflect amphibole fractionation from relatively hydrous, calc‐alkalic magmas. The geochemical features and ages of the Tafresh intrusive rocks suggest that the Neo‐Tethys Ocean did not close completely in the region until the Miocene and is consistent with a diachronous collision starting in the NW and closing later in the SE. [ABSTRACT FROM AUTHOR]

This paper reports on the petrography, geochemistry, and geochronology of late Mesozoic volcanic rocks in the Wenkutu area of the northern Great Xing'an Range, North‐east China, and discusses the formation age, petrogenesis, and tectonic environment of the Manketouebo, Manitu, Baiyingaolao, and Meiletu formations. Results of Zircon U–Pb dating show that the volcanic rocks in the Wenkutu area were formed during the Early Cretaceous (Manketouebo Formation at 145 ± 1 Ma, Manitu Formation at 141.3 ± 1.7 Ma, Baiyingaolao Formation at 128.7 ± 1.1 Ma, and Meiletu Formation at 129 ± 1 Ma). The Manketouebo, Manitu, and Baiyingaolao formations are dominated by intermediate to acid volcanic rocks that belong to the high‐K calc‐alkaline series, with Eu/Eu* values of 0.38–0.84.They are enriched in light rare earth elements (LREE) and depleted in heavy rare earth elements (HREE). The Meiletu Formation is dominated by intermediate to basic volcanic rocks, belongs to the high‐K calc‐alkaline series, has Eu/Eu* values of 0.89–0.97, and is enriched in Ba, K, Th, U, La, Ce, Sr, Nd, and Hf but relatively depleted in Nb, Ta, Zr, P, and Ti, with no obvious fractionation of LREE and HREE. Results indicate that the magma of the Manketouebo, Manitu, and Baiyingaolao formations had a crustal origin, whereas the Meiletu Formation was sourced from the mantle and subsequently contaminated by crustal materials. The late Mesozoic volcanic rocks in the study area were formed during an orogenic stage, and the compressional environment was caused by subduction of the paleo‐Pacific Plate below the Asian continental plate. [ABSTRACT FROM AUTHOR]

Early Cretaceous magmatic rocks associated with the Kerguelen mantle plume are widespread in the Comei area with a chronology concentrated from 134 to 130 Ma. However, less data for the earliest Early Cretaceous magmatic rocks cropping out in the Comei area have been reported. The earliest Early Cretaceous magmatic rocks from the Kada area comprise mafic rock (diabase) and felsic rocks (granite, dacite, and quartz monzonite). This paper presents a detailed LA‐ICP‐MS zircon U–Pb chronology with major and minor (trace) elements and Lu–Hf isotope data from Kada igneous rocks to identify the extent of the early activity of the Kerguelen mantle plume and the initial break‐up of eastern Gondwanaland. The LA‐ICP‐MS zircon U–Pb dates reveal that the age of Kada magmatic rocks range from 136.9 to 143.5 Ma. Kada mafic rocks exhibit both OIB (Samples KD3 and KD06) and N‐MORB (Sample KD7‐1) characteristics. The N‐MORB‐type mafic rocks were derived from partial melting of depleted spinel lherzolite. However, the OIB‐type mafic rocks were derived from partial melting (~60–80 km) of spinel + garnet lherzolite. Kada felsic rocks show obvious enrichment of light rare earth elements and negative Eu anomaly features. Among these, dacite and quartz monzonite rocks show flat heavy rare earth elements and clear Nb, Ta, P, and Ti negative anomalies with depleted εHf(t) characteristics (−11.0 to −21.0). This is indicative of partial melting of specific crustal rocks in an intraplate environment caused by underplating of coeval basaltic magmas. However, granite is characterized by high heavy rare earth element fractionation and high and dispersed εHf composition (−1.5 to +8.9), thus indicating that granite is derived from extensive fractional crystallization of mantle‐derived melts from an AFC process. The Kada felsic rocks show A‐type granitic characteristics in an extensional environment. Based on the evidence from palaeomagnetism reconstructions, Kada rocks and Bunbury basalts are both distributed in and influence the scope of the Kerguelen mantle plume. They are also coeval with the initial break‐up of eastern Gondwana. We suggest that Kada magmatic rocks in southern Tibet represent the earliest activity of the Kerguelen mantle plume and that they played a role in the initial break‐up of eastern Gondwana. [ABSTRACT FROM AUTHOR]

The Eastern Yanbian area, Northeast China is tectonically located in the easternmost margin of the Xing'an Mongolian Orogenic Belt, which is a key area for providing important evidence of mineral deposits to constrain the tectonic evolution of the Paleo‐Asian Ocean. Five quartz‐vein‐type scheelite deposits have been identified in the eastern Yanbian area. These deposits are hosted within the late Palaeozoic metamorphic and granitic rocks and form under the identical hydrothermal mineralization. Zircon U–Pb ages and whole‐rock geochemistry of the ore‐hosting biotite granite and Sm–Nd ages of scheelite crystals within quartz veins are presented in this paper. Zircon U–Pb dating of the biotite granite yields a weighted mean age of 251.9 ± 2.2 Ma (mean standard weighted deviation (MSWD) = 4), and Sm–Nd dating of scheelite samples yields an isochron age of 251.7 ± 2.9 Ma (MSWD = 0.87), which constrains the scheelite mineralization in Eastern Yanbian to the late Permian. Our results, integrated with published geochronological data, indicate three periods of Phanerozoic W mineralization in Northeast China, (a) Cambrian, (b) late Permian (this work), and (c) Jurassic. Geochemical data reveal that the biotite granite is a calc‐alkaline I‐type granite, and it exhibits enrichment in large‐ion lithophile and light rare earth elements and depletion in high‐field‐strength and heavy rare earth elements (especially in Nb and Ta), consistent with the characteristics of arc magma. The subduction‐related biotite granite intrusion and quartz‐vein‐type scheelite mineralization together indicate that the Paleo‐Asian Ocean had not closed before the late Permian in the Eastern Yanbian area, and its final closure occurred in the Early‐Middle Triassic. The late Permian subduction of the Paleo‐Asian Ocean induced the partial melting of the lower crust, thus forming the magmatic arc activity and related quartz‐vein‐type scheelite mineralization, which clearly justifies the proposed tectonic–metallogenic model. [ABSTRACT FROM AUTHOR]

The Kaiyuan tectonic mélange makes up the western part of the Kaiyuan–Yanji Accretionary Complex Belt, NE China, and there has been a long‐standing controversy about its age and tectonic setting. In this paper, we present new zircon U–Pb ages and geochemical data for the mafic rocks of the Lujiapuzi Formation in the Kaiyuan tectonic mélange, and these data provide insights into the tectonic setting during the late Paleozoic and the evolutionary history of the Paleo‐Asian Ocean in the eastern segment of the Central Asian Orogenic Belt (CAOB). SHRIMP U–Pb dating of zircons from samples of albite–actinolite schist and amphibolite yielded a crystallization age of 258 ± 5.5 Ma for the protoliths, suggesting that the protoliths formed during the late Permian. The albite–actinolite schists and amphibolites have similar geochemical characteristics, and they represent metamorphosed basaltic volcanic rocks. Major, rare earth and trace element data show that the mafic rocks have a close affinity with mid‐ocean ridge basalt. REE petrogenetic modelling indicates that the primary magma was generated through the partial melting of a mixed garnet‐ and spinel‐bearing mantle source, and assimilated crustal material and underwent crystal fractionation during ascent. The geochemical features and inherited/xenocrystic zircons in the mafic samples indicate that they formed in a tectonic setting similar to the back‐arc basin. These new findings, together with other previously published data, indicate that the Paleo‐Asian Ocean still existed in the eastern segment of the CAOB during the late Permian to Early Triassic. The Kaiyuan tectonic mélange formed during the Middle Triassic, and its formation may represent the timing of final closure of the Paleo‐Asian Ocean. [ABSTRACT FROM AUTHOR]

The Early Precambrian magmatism in the Archean–Palaeoproterozoic basement Yudongzi Complex is critical for understanding the early crustal formation and evolutionary history of the Yangtze Block in the South China Craton. In this paper, combined zircon UPb geochronological, zircon Hf isotopic, and whole‐rock geochemical studies are carried out on the granitoid gneisses from the Yudongzi Complex, north‐western Yangtze Block. The magmatic zircons from the granitoid gneiss yield a UPb upper intercept age of 2,477±18 Ma, interpreted as the crystallization age of the granitoid gneiss. The granitoid gneiss samples are characterized by high Al2O3 contents, moderate to high Sr/Y, (La/Yb)N and Na2O/K2O ratios, no obvious Eu and Sr anomalies, and depleted Nb, Ta, and Ti values that are similar to those of Archean trondhjemite–tonalite–granodiorite (TTG) suites, indicating that the investigated rocks belonging to TTG‐series rocks. They display pronounced enriched‐LREE patterns with high La/Yb values and relatively high Zr/Sm and Eu/Eu* but low Nb/Ta and Dy/Yb ratios, implying that these rocks were formed by partial melting within amphibolite‐facies conditions with mainly residual amphibole, garnet, and accessory rutile in the magma source. These rocks also display apparently low MgO, Mg#, Ni, and Cr contents, suggesting derivation from partial melting of thickened ancient lower crust. Zircon εHf(t) values from the granitoid gneiss sample vary from −10.1 to −6.9 with TDM2 of ca. 3.59–3.40 Ga, what demonstrates their crustal source nature as well. Thus, taking all these factors together, we propose that the ca. 2.48 Ga granitoid gneisses in the Yudongzi Complex might have been produced by partial melting of ancient crust material under amphibolite‐facies conditions, with primarily residual assemblages of amphibole, garnet, and attached rutile. Taking together our new data and such from previous studies, the Yangtze Block has been probably involved into a significant reworking of ancient crust event during the Early Palaeoproterozoic time. [ABSTRACT FROM AUTHOR]

The tectonic setting of the Alxa Tectonic Belt (ATB) during the late Palaeozoic is highly controversial. The nature and tectonic origin of the late Palaeozoic magmatism in the ATB are key to resolving the current controversy. This paper provides field, petrographic, geochemical, and zircon U‐Pb‐Hf isotopic data for the late Palaeozoic granitoids and volcanic rocks from the south‐western ATB. The granitoids display a wide range of SiO2 contents from diorite, granodiorite, to granites, with widely distributed hydrous minerals such as hornblende and biotite. They are calc‐alkaline to high‐potassium calc‐alkaline, metaluminous with an enrichment of light rare earth elements and large‐ion lithophile elements (LILE), and a depletion of high‐field‐strength elements (HFSE). The presence of mafic‐intermediate enclaves in the plutons suggests the role of crust–mantle interaction in generating the granitoids. The volcanic rocks show "block‐in‐matrix" structures in the field. They are dacite‐porphyry and rhyolite and show calc‐alkaline characteristics with an enrichment of LILE and a depletion of HFSE. Laser ablation inductively coupled plasma mass spectrometry zircon U‐Pb dating shows that the granitoids and enclaves crystallized during ~317–287 Ma and the dacite porphyry formed at ~295 Ma. Hf‐in‐zircon isotopic compositions reveal predominately positive εHf (t) values and Neoproterozoic TDMC ages for the magmatic rocks, indicating mixing between mantle‐derived magma and Precambrian basement during their genesis. The diagnostic field, geochemical data, and isotopic data imply these rocks were generated in a subduction‐related active continental margin setting. The presence of A2‐type granite indicates an extensional environment resulted from slab rollback in a retreating accretionary context can best interpret the large‐scale late Carboniferous–early Permian magmatism in the ATB. Our new data, combined with published data, imply that a large active continental margin existed in the Beishan, Alxa, and the northern margin of the North China Craton, due to the south‐dipping subduction of the Palaeo‐Asian Ocean (PAO) in the late Palaeozoic. Therefore, our data suggest that the PAO did not close until after the early Permian. [ABSTRACT FROM AUTHOR]

This paper reports mineral and whole‐rock geochemical data (major and trace elements, Sr–Nd isotopes, and in situ plagioclase Sr‐isotope analysis) for Cenozoic volcanic rocks from Sabeto, NW Fiji, with the aim of constraining the origin of Cenozoic shoshonitic rocks found throughout Fiji. The most mafic shoshonitic lavas (absarokites) exhibit porphyritic textures and massive structure with phenocrysts of olivine (Fo = 76–78), clinopyroxene (Mg# = 73.9–80.0), and plagioclase (An = 71.9–92.1). Major element geochemical data include SiO2 = 47.31–48.46 wt%, MgO = 4.20–5.76 wt%, Mg# = 49–51, Al2O3 = 17.64–18.93 wt%, and (Na2O + K2O) = 5.12–7.01 wt%. The trace element geochemistry is typically arc like, with enrichment in the large ion lithophile elements (LILEs), the light rare earth elements (LREEs), and P, along with depletion in the heavy rare earth elements (HREEs) and high‐field‐strength elements (HFSEs; e.g., Nb, Ta, Zr, Hf, and Ti). Whole‐rock (87Sr/86Sr)i ratios and εNd(t) values vary from 0.7037 to 0.7039 and from +7.62 to +8.45, respectively. The former is near equal to the 87Sr/86Sr ratios of plagioclase phenocrysts (0.7034–07039). Based on these geochemical data and the results of previous studies, we propose that the Sabeto shoshonitic primary magma was derived from partial melting of the depleted lithospheric mantle, modified by subduction‐related fluids. The thermobarometric calculation indicates that the P–T conditions of Fiji shoshonitic magma chamber are ~1100 °C and ~2.8 GPa (~90 km depth), with an average H2O fraction of ~6 wt%. In addition, the shoshonitic melts experienced fractional crystallization of clinopyroxene, olivine, and plagioclase during magma evolution. These volcanic rocks formed in an extensional setting following collision of the Vitiaz arc and the Ontong Java Plateau during the Pliocene. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report upconversion (UC) luminescence enhancement in LaBGeO5:Yb3+, Er3+ glass‐ceramics (GCs), surface crystallized glass‐ceramics (SCGCs) and ceramics compared with the as‐melt glass fabricated by the conventional melt‐quenching technique. Based on structural investigations, we find that the nucleation and crystallization of trigonal stillwellite LaBGeO5:Yb3+, Er3+ nanocrystals occur first at the glass surface before the following volume crystallization. The local site symmetry around rare earth (RE) ions which was evaluated using the Eu3+ ions as a probe together with Judd‐Ofelt theory calculations exhibits a clear increase with the devitrification of the glass. Consequently, complete crystallization of the glass leads to largest enhancement in the UC emissions of the LaBGeO5:Yb3+, Er3+ ceramics. We ascribe the enhancement of UC luminescence in the LaBGeO5:Yb3+, Er3+ GCs, SCGCs, and ceramics to the structural ordering and the improvement of site symmetry surrounding RE ions that minimizes the rate of nonradiative relaxation process. [ABSTRACT FROM AUTHOR]

Due to strong anti‐poisoning ability, good emission stability, high emission current density, lanthanum hexaboride (LaB6) and cerium hexaboride (CeB6) have been maturely applied in electron emission emitter. In this paper, a new manufacturing method for LaB6 (or CeB6) powder was proposed by using La2O3 (or CeO2), B4C, and Al as raw materials. After high‐temperature reaction in the range of 1673–1773 K and the following alkaline leaching at 90°C, LaB6 or CeB6 powder with particle size of about 10 μm was obtained. Furthermore, by Al metal flux method, the obtained powder was used to manufacture single crystal block with size of several millimeters. [ABSTRACT FROM AUTHOR]

This work evaluates glacial dust as a source of sediment, and associated iron (Fe), to the Fe‐limited Gulf of Alaska (GoA). A reanalysis of GoA sediment data, using rare earth elements and thorium as provenance tracers, suggests a flux to the ocean surface of Copper River (AK) glacial dust, and associated Fe, that is comparable to the flux of dust from Asia, at least 1,000 km from the narrow mountain valley glacial dust source area. This work suggests dust from Asia may not be the largest source of Fe to the GoA. Dust models fail to accurately simulate this glacial dust transport because their coarse resolution underestimates wind speeds, and the dust flux. This work suggests that glacial dust fluxes may have been important in the geologic past (e.g., the last glacial maximum) from locations where there was more extensive coverage by glaciers than at present. Plain Language Summary: The growth of phytoplankton, the base of the marine food web, is known to be limited by availability of the micronutrient iron in the Gulf of Alaska. We evaluated the importance of glacial dust in this region as a source of iron, and other trace metals, by using concentrations of the rare earth elements and thorium in particles as tracers of their geographic origin. We analyzed for these elements in glacial dust samples from the Copper River valley (Alaska), the largest source of glacier‐derived dust. Together with previously published concentrations for dust from Asia and volcanic material, we estimated the inputs of each source material to the sediments of the Gulf of Alaska. This information, together with published sediment mass accumulation rates, suggests an important contribution of Alaskan glacial dust and associated iron, to surface waters of the Gulf of Alaska, at least 1,000 km from the source. Dust models fail to accurately simulate this dust transport because their coarse spatial resolution substantially underestimates wind speeds. Glacial dust fluxes may have been important sources of iron in the geologic past (e.g., the Last Glacial Maximum) from New Zealand and South America, when there was more extensive glacial coverage. Key Points: Copper River glacial dust contributes substantially to Gulf of Alaska sediments, and associated iron to surface watersDust models lack sufficient spatial resolution to accurately simulate the winds that drive the flux of glacial dust from narrow valleysGlacial dust‐associated iron may have been important in the geologic past in times and locations with more extensive glacial coverage [ABSTRACT FROM AUTHOR]

In thin films of rare-earth manganites, RE1− xM xMnO3 (RE=rare earth, M=Ca, Sr, Ba), with mixed-valence perovskite structure, the transport properties highly depend on the deposition technique, processing conditions, and the substrate used. Chemical solution deposition techniques provide many advantages, such as low cost, easy setup, and coating of large areas. However, the crystalline quality, uniformity, and reproducibility of the film depend on the reactivity of the chemical used for solution preparation. In this paper, we report a novel process to grow rare-earth manganite films using low-cost polymer-assisted deposition technique. In this process, polymer controls the viscosity and binds metal ions, resulting in a homogeneous distribution of metal precursors in the solution and a uniform film. These solutions were stable, and crack-free films were obtained using these solutions. In this paper, thin films of La1− xSr xMnO3, La1− xCa xMnO3, and Pr0.5Ca0.5MnO3 were grown on (001) LaAlO3 substrates. The La1− xSr xMnO3 and La1− xCa xMnO3 films were highly c-axis oriented and epitaxial, and showed high magnetoresistance near their Curie temperature. Charge ordering was observed in the Pr0.5Ca0.5MnO3 film at 220 K and high magnetoresistance of nearly −100% was obtained at low temperatures. The structural, transport, and magnetic properties of these films were similar to those obtained for films grown by physical vapor deposition. [ABSTRACT FROM AUTHOR]

In a previous paper, we reported that the reaction of cerium metal in 2-methoxyethanol yielded a transparent colloidal solution of ultrafine (2 nm) ceria particles [M. Inoue, M. Kimura, T. Inui, Chem. Commun., 957 (1999)]. In this paper, the solvothermal reaction of other rare-earth metals in 2-methoxyethanol has been examined. Reactions of Sm and Yb metals in 2-methoxyethanol at 300°C yielded transparent colloidal solutions of Sm2O3 and Yb2O3 particles. However, the reaction of rare-earth metals of Y, Eu, Gd, and Tb in 2-methoxyethanol at 300°C resulted in recovery of the starting materials. Transparent colloidal solutions of the oxides of these elements were obtained by reaction in the presence of a small amount of acetic acid. The solvothermal reaction of rare-earth metals in 2-aminoethanol was also examined. [ABSTRACT FROM AUTHOR]

In this paper, we compare the U-Pb zircon age distribution pattern of sample 14311 from the Apollo 14 landing site with those from other breccias collected at the same landing site. Zircons in breccia 14311 show major age peaks at 4340 and 4240 Ma and small peaks at 4110, 4030, and 3960 Ma. The zircon age patterns of breccia 14311 and other Apollo 14 breccias are statistically different suggesting a separate provenance and transportation history for these breccias. This interpretation is supported by different U-Pb Ca-phosphate and exposure ages for breccia 14311 (Ca-phosphate age: 3938 ± 4 Ma, exposure age: ~550-660 Ma) from the other Apollo 14 breccias (Ca-phosphate age: 3927 ± 2 Ma, compatible with the Imbrium impact, exposure age: ~25-30 Ma). Based on these observations, we consider two hypotheses for the origin and transportation history of sample 14311. (1) Breccia 14311 was formed in the Procellarum KREEP terrane by a 3938 Ma-old impact and deposited near the future site of the Imbrium basin. The breccia was integrated into the Fra Mauro Formation during the deposition of the Imbrium impact ejecta at 3927 Ma. The zircons were annealed by mare basalt flooding at 3400 Ma at Apollo 14 landing site. Eventually, at approximately 660 Ma, a small and local impact event excavated this sample and it has been at the surface of the Moon since this time. (2) Breccia 14311 was formed by a 3938 Ma-old impact. The location of the sample is not known at that time but at 3400 Ma, it was located nearby or buried by hot basaltic flows. It was transported from where it was deposited to the Apollo 14 landing site by an impact at approximately 660 Ma, possibly related to the formation of the Copernicus crater and has remained at the surface of the Moon since this event. This latter hypothesis is the simplest scenario for the formation and transportation history of the 14311 breccia. [ABSTRACT FROM AUTHOR]

Colloid systems modified by luminescent ions in situ are highly attractive for the design of new molecular architectures and adaptable for monitoring and visualizing soft drug delivery systems. This paper presents original results on the characterization of the self-organization process and the structure of vesicles formed by tetraethylene glycol monodecyl ether (CEO) in the presence of lanthanide ions and decanol additives. Detailed characterization of surface activity, aggregation properties and microstructure of individual and mixed aggregates has been carried out based on surface tension, electron microscopy, small-angle X-ray scattering, dynamic light scattering analysis and fluorescence spectroscopy. The small-angle scattering results in combination with quantum-chemical calculations assume the multishell vesicle formation in CEO/CHOH/HO media. In the CEO solution the presence of Ln(III) ions and decanol initiate the formation of multilamellar vesicles with a size of about 100 nm. The luminescence analysis of the Eu(III) and Tb(III) complexes has shown the efficient solubilization in the CEO/CHOH/HO vesicles, which leads to increase in the lifetime. The resulting outcome is the possibility to control micro and macro properties of a molecular organized system to give it the desired functionality. [ABSTRACT FROM AUTHOR]

The Compostela area is located in the western Trans‐Mexican Volcanic Belt, which consists of volcanic rocks that produced during the Pliocene to Recent volcanism. In this paper, we present petrography, whole‐rock major‐ and trace‐element concentrations, Ar–Ar ages, and Sr–Nd isotopic data of volcanic rocks from the Compostela area in the south of the city of Tepic, Nayarit, Mexico. These volcanic rocks are of intermediate composition and belong to the transitional series: basaltic trachyandesites [52.72–53.94 wt% SiO2; 0.69–2.53 wt% MgO] and subalkaline series: low‐Si [55.11–60.94 wt% SiO2; 0.79–2.74 wt% MgO] and high‐Si [61.60–62.71 wt% SiO2; 0.36–0.80 wt% MgO] andesites. The 40Ar/39Ar dating of two basaltic trachyandesites yields plateau ages of 1.05 ± 0.15 Ma and 1.07 ± 0.17 Ma and the andesites yielded a plateau age of 2.42 ± 0.36 Ma. These results indicate that the studied rocks were formed during the Pleistocene in two discrete episodes. The basaltic trachyandesites show enriched light rare earth elements patterns relative to high rare earth elements [(La/Yb)N = 5.81–8.07] with negligible Eu anomalies. The andesites display enriched large‐ion lithophile elements (Ba, K) with anomalies of Nb (Th/Ce) and Ti in the three groups identified in the subalkaline series. The basaltic trachyandesites appear in a tight cluster of initial 87Sr/86Sr ratios (0.703519–0.703882) as compared to the basaltic andesite 87Sr/86Sr (0.704073) and positive ɛNd(t) values of +5.6 to +3.4, respectively, indicating that the basaltic trachyandesites were derived from intermediate magmas from a shallow mantle source. Geochemical modelling reveals that both basaltic trachyandesite and andesite rocks were derived by a process of crystal fractionation accompanied by assimilation of crustal rocks at the lower or middle level. Geochemical ratios and multidimensional discrimination diagrams, combined with the cross‐section of the subduction zone indicates that basaltic trachyandesites were generated from a rift and/or Ocean Island Basalt‐type source, whereas andesites were generated from a slab‐derived source in a subduction environment. [ABSTRACT FROM AUTHOR]

Dehydration reactions within subducted oceanic crust are important for fluid‐mediated element transfer within the subducting plate and potentially to the mantle wedge. The effects of metamorphic reactions and fluid flow on element recycling that occur during retrogression and exhumation of subducted continental crust from mantle depths are poorly understood. We study two metabasite pods with fresh eclogite cores and retrogressed amphibolite‐facies rims and surrounding host gneiss within the Western Gneiss Region (WGR), Norway, to better understand element mobility and mass transfer during exhumation of subducted continental crust. Bulk‐rock data were collected from samples taken across the pod and into the host gneiss. Phengite breakdown in eclogite and epidote recrystallization in veins and/or gneiss within pod cores contributed large ion lithophile elements and REE to retrogressed eclogite closest to the pod cores. In gneiss hosting the pods, phengite and epidote breakdown provided fluid that mediated elemental transfer and redistribution to the pod rim or tail. Compared to the studied pod in the southern WGR, the pod in the northern WGR underwent higher P‐T conditions, partial melting and higher strain rates. This resulted in the infiltration of external fluid farther into the pod interior from the rim and facilitated larger mass gain in trace elements in the amphibolite tail of the pod relative to fresh eclogite in the core. The results show clear evidence for retrogression dehydration reactions driving significant fluid‐mediated element redistribution as observed on the outcrop scale during exhumation following ultrahigh‐pressure metamorphism, which directly impacts element signatures within the exhuming crust. Plain Language Summary: A lot is not known about how fluids and metamorphic reactions recycle elements in continental crust as it is brought to the surface after being subducted to ∼100 km. We study two eclogite pods that are surrounded by gneiss in the Western Gneiss Region, Norway to study how different pressure‐temperatures (P‐T), deformation, and fluids control element movement in deep crust as it is exhumed. The pod cores have eclogite that record the rock conditions at ∼100 km, but the exteriors were altered during exhumation. We sampled transects from the pod cores to ∼20 m into the surrounding gneiss. Bulk‐rock and mineral trace‐element data show two situations of mineral breakdown that generated trace‐element‐rich fluid that reacted with and enriched metabasite in Rb, Sr, Ba, and light rare earth elements: (a) veins or gneiss in pod cores enriched adjacent eclogite, and (b) surrounding gneiss enriched the pod exteriors. As shown by the pod that experienced higher P‐T conditions and deformation than the second pod, larger amounts of elements were transferred into the pod rim, and fluid penetrated the pod, enriching eclogite near the pod rim. Clearly, exhumation conditions and mineral break‐down reactions are important for elemental recycling in crust during exhumation. Key Points: In the Western Gneiss Region, Norway, fluids redistribute elements during retrogression after ultrahigh‐pressure metamorphismRecrystallization of epidote‐group minerals and phengite in metabasite pod interiors facilitate elemental transfer within the podsHost gneiss‐derived fluids infiltrate amphibolite‐facies retrogressed pod rims, driving significant element redistribution and mass transfer [ABSTRACT FROM AUTHOR]

Establishing the biogenicity of sedimentary surface textures with unresolved microbial origin is critical to any environmental and geobiological interpretation of clastic settings. Here, some Ediacaran wrinkle structures and associated carbonaceous greywacke samples containing mat fragments rich in 'bacteriomorph acritarchs' are investigated. Their biogenicity was evaluated with transmitted light and scanning electron microscopy, epifluorescence and Raman spectroscopy, and confirmed by the presence of distinct cyanobacterial biomarkers. The comparison of results yielded by these techniques validates the use of Raman spectroscopy on Neoproterozoic kerogen (organic‐walled microfossils and amorphous organic material) under low metamorphic conditions. Raman spectrographs also allowed recognition of associated rare‐earth element‐rich phosphate (monazite) and subsidiary metal sulphide concentrations, and interpreted as a result of biosorption and/or mat trapping under normal oxic conditions. These microbial mat features represent cyanobacterial bloom‐forming Bavlinella acritarchs, which characterise eutrophic episodes in a semi‐enclosed retroarc basin sandwiched between an active Cadomian arc and West Gondwana. [ABSTRACT FROM AUTHOR]

Phosphorites of the Georgina Basin (northern Australia) are an established economic source of phosphate and have recently been recognized to be a potential source of rare earth elements (REE). Previous bulk‐rock geochemistry work focused on the eastern margin of the basin revealed that phosphorites from the southern region have significantly higher (up to 0.5%) REE contents than equivalent prospects further to the north. In this study, we examine the origin of REE enrichment in the Georgina Basin phosphorites using an integrated geochemical, petrographic, mineralogical, and isotopic (Sm‐Nd and Sr) approach. The trace element geochemistry of primary phosphate minerals is consistent with a seawater origin for the REEs in phosphorites, with minimal input from the underlying basement rocks. Variations in total REE concentrations are controlled largely by the seawater composition, depositional environment, and the texture of the phosphorite (grainstone vs. mudstone phosphorite). Grainstone phosphorite yields on average higher concentrations of REEs compared to the mudstone phosphorite, likely due to the higher surface‐to‐mass ratio of the grainstone phosphorite resulting in the uptake of higher concentrations of REEs during coastal reworking. The formation of the low‐REE northern and central deposits took place during early transgression in oxidized, shallow supratidal to subtidal platformal environments. During the subsequent main transgressive event, fault‐controlled topography in the southern domain allowed phosphogenesis along basement highs to be facilitated along a redox boundary, where more saline and REE‐rich deep anoxic bottom waters, along with Fe‐cycling and bacterial mediation played a major role in the enrichment of REEs in the southern phosphorites. Key Points: The origin of rare earth element (REE) enrichment in phosphorites of the Georgina Basin in northern Australia, was determined using an integrated geochemical, mineralogical, and isotopic approachThe enrichment of REEs in phosphorites is controlled by the texture and the depositional environment at the time of phosphorite formationVarying levels of REE enrichment occurred at different stages of marine transgression [ABSTRACT FROM AUTHOR]

Phosphorites can record oceanic conditions during their deposition, but the faithful retention of primary information in Paleoproterozoic deposits can be mitigated by post‐depositional processes. Here, we examine a peritidal phosphorite within a microbialite reef complex in the 2.4–2.2 Ga Turee Creek Group in Western Australia to assess the environmental information retained. Field mapping and petrography distinguishes between authigenic and locally transported phosphorite fragments, each of which contains unique information regarding the deposit. Elemental mapping and laser‐ablation analyses differentiate the impact of depositional versus early diagenetic versus metamorphic processes within these fragments. Samples within a near‐shore pebble conglomerate have mixed riverine‐oceanic signals and lack cerium anomalies, consistent with the depositional environment. Clasts from off‐shore peloidal grainstone beds retain "hat‐shaped" patterns with small negative cerium anomalies, reflective of transport and redeposition within potentially oxic seawater. U‐Pb isotopic dates range from ∼1.8 to 2.3 Ga and are generally uncorrelated with rare earth element and yttrium data. The youngest date (∼1.8 Ga) is associated with recrystallized apatite, with concave down, middle rare earth element enriched patterns. A potential depositional age, ∼2.3 Ga, is associated with massive apatite in a chert‐rich clast that has rare earth element patterns reflective of riverine‐oceanic signals. Overall, the peritidal system in the reef was dynamic, with potentially oxic seawater that had a strong riverine influence. Local recycling and reworking, early diagenesis, and later orogenic events impacted the preserved geochemical signals and together show that spatially resolved geochronological and geochemical data are ideal for interpreting ancient phosphorites. Plain Language Summary: Understanding our ancient rock record is challenging because very few rocks are preserved from early Earth. Phosphorites are sedimentary deposits that are useful environmental archives because apatites can preserve primary chemical information. Here, we examined a shallow water phosphorite deposit from a reef complex in the c. 2.4–2.2 Ga Turee Creek Group to see what information is preserved. Knowing what the environment was like at this time will provide important insights into life at the time of the Great Oxidation Event. The phosphorite here contains a variety of textures of apatite, representative of different environmental and secondary processes, so we used spatially resolved techniques to study the different textures. Our data show that more chemically pristine apatite textures record a potentially oxic, mixed riverine‐oceanic signal, while others are more representative of transport and early diagenesis or metamorphism. Overall, we show that deep‐time phosphorites are useful archives for environmental information and that life at this time may have encountered oxygenated water in the very shallow oceans. Key Points: Spatially resolved data differentiate depositional and secondary information from a peritidal phosphorite in a Paleoproterozoic microbialite reef complexApatite rare earth element data indicate a mixed riverine‐oceanic, potentially oxic signal for the depositional environmentApatite U‐Pb data show a prospective depositional/early diagenetic age (∼2.3 Ga) alongside ages coincident with regional orogenic events at ∼2.1 and ∼1.8 Ga [ABSTRACT FROM AUTHOR]

Occurrences of alkaline and carbonatite rocks with high concentrations of rare earth elements (REE) are a defining feature of Precambrian geology in the Mojave Desert of southeastern California. The most economically important occurrence is the carbonatite stock at Mountain Pass, which constitutes the largest REE deposit in the United States. A central scientific goal is to understand the genesis of the carbonatite ore body in the context of widespread REE‐rich igneous activity. A swarm of mafic alkaline (shonkinite) dikes has been mapped and sampled at Bobcat Hills, 65 km southeast of the Mountain Pass mine. Whole‐rock geochemistry and zircon geochronology demonstrate a clear affinity to the ca. 1.4 Ga Mountain Pass intrusive system. Bobcat Hills dikes have comparably high REE concentrations (La ∼1,000× chondritic) and an error‐weighted mean 207Pb/206Pb zircon crystallization age of 1,426 ± 2 Ma (2σ). Unlike the alkaline intrusions at Mountain Pass, which have abundant inherited zircon from Paleoproterozoic basement rocks and crustally influenced oxygen isotope compositions (δ18Ozircon = 6.5–7.5‰), the Bobcat Hills dikes lack any evidence of crustal assimilation and have oxygen isotope values that overlap a mantle range (Bobcat Hills average δ18Ozircon = 5.6 ± 0.3‰). The dikes were a high‐temperature, early center of mafic alkaline magmatism in the Mojave Desert that serve as a snapshot of melt generation from a spatially extensive, metasomatized mantle source. We propose that modification of the crust over many tens of Myr at Mountain Pass created an environment that favored crustal assimilation and enabled ascent of late‐stage, REE‐rich carbonatite magmas. Key Points: The Bobcat Hills site expands the distribution of REE‐rich mafic alkaline magmatism 65 km southeast of the Mountain Pass mineShonkinite dikes at Bobcat Hills are physically and chemically similar to mafic intrusions at Mountain Pass and have comparably high REEBobcat Hills was an early center of REE‐rich magmatism in the Mojave Desert, with a zircon U‐Pb crystallization age of 1,426 ± 2 Ma [ABSTRACT FROM AUTHOR]