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The time and processes of hydrothermal mineralization are long-standing problems in geology. This work addresses these questions with reference to the Maoniuping giant rare earth elements (REE) deposit (southwest China), which has rare earth oxides (REO) reserves of 3.17 million tons with an average grade of 2.95 wt%. Bastnäsite is the dominant economic mineral, occurring as four distinct paragenetic types in the Maoniuping syenite–carbonatite complex: (1) primary euhedral bastnäsite (type-A) in syenite, with isolated melt inclusions; (2) macro-crystalline tabular euhedral bastnäsite (type-B) in pegmatitic dikes, with a diverse variety of fluid inclusions; (3) fine-grained, anhedral veinlet-disseminated bastnäsite (type-C) in syenite; and (4) coarse-grained anhedral bastnäsite (type-D) in carbonatite dikes, occurring as veinlets or interstitial to calcite, fluorite, and barite. From the paragenetic and compositional variations, it is inferred that type-A bastnäsite is of primary magmatic origin, whereas the other three types have characteristics of hydrothermal origins. In situ LA-ICP-MS U-Pb geochronology of the four types of bastnäsite results in lower intercept ages of 28.2 ± 0.5 Ma (n = 95, MSWD = 5.10), 27.8 ± 0.4 Ma (n = 43, MSWD = 0.73), 26.8 ± 0.7 Ma (n = 50, MSWD = 0.83), and 25.8 ± 0.7 Ma (n = 55, MSWD = 1.70), respectively, which are consistent with the weighted average 206Pb/238U and 208Pb/232Th ages by 207Pb-correction method. Compositional variations of clinopyroxene and apatite from the associated syenite, pegmatitic and carbonatitic dikes indicate a genetic relationship of the Maoniuping alkaline complex. The compositions of clinopyroxene range from Ae44–67Di14–18Hd17–41 in pegmatitic dikes, Ae43–66Di6–20Hd21–38 in carbonatitic dikes to Ae68–90Di0–3Hd10–30 in syenite. Apatites in the pegmatitic and carbonatitic dikes have similar compositions with higher F, total REE, and Sr, and lower CaO contents than those in the syenite, which suggests a cogenetic origin for the associated pegmatite and carbonatite. Clinopyroxene and apatite compositions suggest that the pegmatitic melt might differentiate directly from the initial carbonatitic melt rather than the syenitic magma. The bastnäsite U-Pb geochronology and minerals data indicate continuous magmatic-hydrothermal evolution for the REE mineralization in the Maoniuping alkaline complex. [ABSTRACT FROM AUTHOR]

Crustal delamination induced by eclogitization of orogenic roots, in addition to plate subduction, is an important process that transfers crustal materials back into the mantle. Many previous studies have demonstrated a causal link between crustal delamination and eclogitization, but actual magmatic records of the process are rarely documented. Here we present detailed studies on two distinct late Paleozoic adakite suites in the Awulale Mountains (Chinese Western Tianshan), that is, the suites with high (HN) and low (LN) Nb/Ta ratios, to constrain the regional crustal delamination. Both igneous suites have adakitic affinity and formed by partial melting of the juvenile thickened lower crust with different residual mineral assemblages in their source regions. The late Carboniferous HN adakite has superchondritic Nb/Ta (21.4–23.3) and high Dy/Yb (2.66–2.88) ratios and may have formed via rutile‐bearing, eclogite‐controlled melting of the lower crust, implying crustal thickening and eclogitization. In contrast, the Permian LN adakites have varying and lower ranges of Nb/Ta (12.9–20.0) and Dy/Yb ratios (1.35–2.53), which were probably derived from mixing of garnet‐bearing amphibolite with minor rutile‐bearing, eclogite‐controlled melts, implying crustal thinning and the end of eclogitization. The succession of these two adakite suites suggests that during the late Carboniferous to early Permian, eclogitization of the orogenic root, accompanying successive crustal delaminations, occurred in this region. Accordingly, our results imply that adakites with different geochemical features are potential tracers for the mineralogy of orogenic roots and, importantly, provide convincing evidence for eclogitization‐induced crustal delamination in orogenic belts. Key Points: Two distinct adakite groups (with super/subchondritic Nb/Ta ratios) are present in the Awulale Mountains (Chinese Western Tianshan)Adakite geochemical features are controlled by the residual mineral assemblages in the magma sourcesAdakites in orogenic belts could be used to trace eclogitization‐induced crustal delamination events [ABSTRACT FROM AUTHOR]

Abstract: Melting and dehydration of subducted oceanic slabs dominate element recycling within the subduction factory, but the role of recycled oceanic crust in the source of intraplate magmas is poorly understood. In situ zircon O‐Hf isotope data from two Early Cretaceous alkaline A‐type granites that are genetically related to large‐scale extension of eastern China in the Late Mesozoic (circa 125 Ma) yield low δ18O (1.8 ± 0.3‰ to 5.1 ± 0.3‰, 2σ) and positive εHf(t) (1.5 ± 1.2 to 17 ± 1.2, 2σ). This suggests the contribution of altered oceanic crust and an enriched mantle component in the source region. Elevated initial 87Sr/86Sr and 206Pb/204Pb ratios, and εHf(t) whole rock values with relatively constant εNd(t) values beyond the normal mantle array, require a component that underwent seawater interaction in the source of protolith. The geochemical data require a complex source region for the alkaline A‐type granites in NE China involving more than 40% recycled oceanic crust. This altered oceanic crust beneath the Late Mesozoic lithospheric mantle likely represents remnants of multiple subduction and collision events between microblocks from the Late Paleozoic to Early Mesozoic in northeastern China. Recycling of subducted oceanic crust represents a novel exotic source for the origin of alkaline A‐type granites in intraplate extensional settings. [ABSTRACT FROM AUTHOR]

Although thermal lattice expansion is a well-documented nature of crystals, including zircon and zircon-type minerals, chemical lattice expansion of natural mineral is rarely reported. Here we present a comprehensive investigation on three types of natural zircon that records the evolution of the granitic system in Xiangshan, North China, and shows expanding crystallographic parameters induced by chemical incorporation instead of thermal expansion. Prismatic and oscillatory-zoned zircon grains (Type-1A), crystallized early in the granitic magma at high temperatures in a volatile-undersaturated environment, have the smallest lattice parameters ( a = 6.603 Å, c = 5.971 Å). Prismatic and altered zircon grains (Type-1B), formed under volatile-saturated conditions and in the presence of F-rich fluid with numerous thorite and xenotime inclusions, have intermediate lattice parameters ( a = 6.649 Å, c = 6.020 Å). Pyramidal zircon grains (Type-2), formed in a subsolvus granitic system at relatively low temperatures and coexisted with fluid inclusions, have the biggest lattice parameters ( a = 6.677 Å, c = 6.010 Å). Trace elements, including Hf, Th, Ti, Y, and REE, and volatiles content, increase in the structure of zircon from the early to late magmatic origin, which is consistent with the expansion of the lattice parameters. The occurrence of the three zircon types in the Xiangshan arfvedsonite granites is interpreted to reflect the progressive fractionation of granitic melt from hypersolvus to subsolvus conditions. Therefore, we conclude that the lattice expansion of zircon in this study results from chemical incorporation of trace element and volatile components during the magmatic to hydrothermal evolution of granitic magma. Besides, the textural and compositional evolution of zircon can be used as efficient indices for the fractionation and evolution of A-type granitic system. [ABSTRACT FROM AUTHOR]

Large-scale Mesozoic volcanisms in the Great Xing’an Mountains (GXM), northeastern (NE) China, are being extensively interested recently. However, the petrogenesis and geodynamic implications of these volcanic rocks are still on controversy. In this study, geochronology and geochemistry of the intermediate and felsic volcanic rocks of Late Mesozoic from the southern GXM was investigated. Zircon U–Pb geochronology yields 206 Pb/ 238 U ages ranging from 154.3 ± 1.7 Ma to 127.0 ± 2.4 Ma for the eight selected volcanic rocks, where the major period of the Mesozoic volcanisms is constrained during the Early Cretaceous. The presented volcanic rocks are andesite–trachydacite–rhyolite and show calc-alkaline to shoshonitic features. They have elevated incompatible trace element concentrations and significantly negative Nb–Ta–Ti and positive Pb anomalies, which display characteristics of typical subduction-related magmas rather than within-plate magmatic signature. Sr–Nd isotopic data indicate that their magma sources were mixed with proportions of old crustal components. Geochemical features, therefore, indicate that the intermediate and felsic shoshonitic magma was plausibly derived from partial melting of the subduction-modified lithospheric mantle and thickened lower crust, respectively, induced by delamination and/or asthenosphere upwelling in extensional setting. Combined with the tectonic evolution of the Great Xing’an area, we propose a hypothesis that the large-scale Mesozoic volcanisms in NE China were controlled by the transition of regional stress from southward to westward, which are induced by the changes of tectonic regimes from the previous Mongol–Okhotsk subduction to the succeeding paleo-Pacific subduction during Late Mesozoic. [ABSTRACT FROM AUTHOR]

The formation of large iron deposits associated with subduction and its genetic relationships with ferrobasalts are not yet well understood. Here we report a geochemical and geochronological investigation on the newly discovered ferrobasalts associated with the Chagangnuoer iron deposit, western Tianshan. The Chagangnuoer ferrobasalts are characterized by high Fe2O3T(14.55–22.68 wt.%) and MnO (0.36–0.93 wt.%) but low TiO2(0.70–1.26 wt.%) contents. Analyses of 10 zircon grains yield a weighted zircon U–Pb age of 314 ± 8 Ma. Based on our new petrological and geochemical data, we conclude that the Chagangnuoer ferrobasalts probably have been originated from the partial melting of a spinel peridotite mantle source that has been modified by subduction related fluids. The ferrobasalts have nearly linear positive correlation between MnO and (87Sr/86Sr)i, implying the involvement of subducted Fe–Mn nodules. The mid-ocean ridge basalt (MORB)- and ocean island basalt (OIB)-like geochemical features, as well as moderate Ti/V values (18–36), indicate that the ferrobasalts may have been formed in an extensional back-arc basin setting. Combined with previous studies on the Chagangnuoer iron deposit, we propose a hypothesis that the overlying iron orebodies were likely derived from the ferrobasaltic magma. [ABSTRACT FROM AUTHOR]

Arc magmatism plays an important role in the recycling of subducted carbon and returning it to the surface. However, the transfer mechanisms of carbon are poorly understood. In this study, the contribution of subducted carbonate-rich sediments to the genesis of the carbonate-bearing K-rich igneous rocks from western Tianshan was investigated. Four key triggers are involved, including sediments subduction, slab decarbonation, partial melting and magma segregation. The globular carbonate ocelli show C–O isotope signatures intermediate between oceanic sediments and mantle, suggesting that the carbon of the primary carbonate ocelli was derived from recycled subducted sediments in the mantle. Decarbonation of the subducted slab is regarded as the primary agent to carbonize the mantle wedge. Geochemical features indicate that the carbonate ocelli are primary, and that the parental K- and carbon-rich mafic alkaline magma was derived from partial melting of carbonated mantle wedge veined with phlogopite. Major and trace element compositions indicate that globular carbonate ocelli hosted in the Bugula K-rich igneous rocks are calcio-carbonate and formed primarily by segregation of the differentiated CO 2 -rich alkaline magma after crystallization fractionation. The K-rich alkaline magma, which formed from partial melting of metasomatized (i.e., phlogopite bearing) mantle wedge in the sub-arc region, is a favorable agent to transport subducted carbon back to the Earth’s surface during carbon recycling in subduction zones, because of the high CO 2 solubility in alkaline mafic magma. We therefore propose a model for the petrogenesis of the carbonate-bearing K-rich igneous rocks in western Tianshan, which are significant for revealing the mechanism of carbon recycling in subduction zones. [ABSTRACT FROM AUTHOR]

Abstract: Continuous Late Paleozoic magmatic activity in the western Tianshan, Xinjiang, China, temporally overlapped the Late Carboniferous collision between the Tarim and the Kazakhstan–Yili plates. Isotopic dating, whole-rock geochemistry, and isotopic characteristics of a suite of calc-alkaline to shoshonitic rocks from Yuximolegai area, in the eastern end of the Awulale Mountains, help define the tectonic evolution of this part of the Tianshan. Zircon U–Pb ages of a quartz diorite and a quartz syenite porphyry are 310.8±2.1Ma and 284.4±3.6Ma, respectively. The geochemical and isotopic characteristics of Late Carboniferous igneous rocks, including the quartz diorite, as well as basaltic andesite and K-rich trachyandesite, indicate an evolution from calc-alkaline towards shoshonitic series. This was generated by the partial melting of the hydrated mantle wedge induced by changing subduction angles. The younger quartz syenite porphyry, however, was more likely derived from the partial melting of a thickened crust in a post-collisional setting or the partial melting of hot juvenile basalt in the lower crust during Early Permian delamination of the subcontinental lithospheric mantle. Therefore, the generation of the calc-alkaline to shoshonitic igneous rocks in Yuximolegai area is genetically linked to the geodynamic evolution of the western Tianshan from convergent subduction to collision during the Late Paleozoic. [Copyright &y& Elsevier]

The Awulale Mountains, the conjunction point of the Tarim Plate, Junggar Plate and Yili-Central Tianshan Block, are the crucial place to decipher the tectonic evolution of the western Tianshan. We report results of petrologic, whole-rock geochemical, Sr–Nd isotopic data and in-situ zircon U–Pb and Hf isotopes for the Wuling (poikilitic) hornblende gabbro from the Awulale Mountains, western Tianshan. Two stage crystallization processes are applied to interpret its mineral composition. Zircon U–Pb ages indicate that the Wuling hornblende gabbro was emplaced during the late Carboniferous (313 Ma ± 3 Ma). The Wuling hornblende gabbro is characterized by tholeiitic affinity with low 87 Sr/ 86 Sr ratios, positive ε Nd ( t ) and zircon ε Hf ( t ) values, resembling its coeval mafic rocks in the Awulale Mountains. They are enriched in large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs), indicating a subduction-related setting for their generation and their mantle source were mainly fluxed by fluids released by the down-going slab. The flat REE and depleted Sr–Nd–Hf isotopic signatures imply a shallow and heterogeneous mantle source with the involvement of a deep MORB-like component. We propose that an arc–nascent back-arc system had been developed between the Nalati Mountains and the Awulale Mountains during the late Carboniferous, where the magma derived from decompression melting of MORB-like mantle caused by the slab roll-back and flux-induced melting of mantle wedge were both contributed to their generation. The arc-type features of them were inherited from the strong subduction input at the initiation of back-arc rifting. However, the back-arc rifting ceased at the end of late Carboniferous because of the compressional stress from the collision between the Tarim Plate and the Yili-Central Tianshan Block. [ABSTRACT FROM AUTHOR]

A-type magmatism is an effective lithoprobe for constraining the tectonic evolution of orogenic belts. In this study, we have identified two episodes of Late Paleozoic A-type magmatism in Qunjisayi, western Tianshan. Zircon U–Pb geochronology has yielded Late Carboniferous (rhyolites, 306 ± 2 Ma)- and Early Permian (granites, 296 ± 3 Ma) ages. Both the Qunjisayi rhyolites and granites have depleted Sr–Nd–Hf isotopic compositions, moderate A/CNK ratios (0.91–1) and negative Nb and Ta anomalies. They are also characterized by high K 2 O + Na 2 O (8.72–10.6 wt.%), FeO T /(FeO T + MgO) (0.86–0.99) and Y/Nb (1.42–2.34) values, similar to those of typical A 2 -type granitoids. The Qunjisayi rhyolites may have been formed by partial melting of a juvenile calc-alkaline granitic crustal source induced by subduction roll-back in shallow depth. The succeeding Qunjisayi granites were likely to be derived from a lower crustal source that contains depleted mantle-derived components. Asthenospheric mantle upwelling, triggered by post-subduction slab break off, may have been important in the Qunjisayi granites formation. We conclude that the Late Paleozoic Qunjisayi A-type magmatism was genetically linked to the geodynamic transformation from late subduction to collision. [ABSTRACT FROM AUTHOR]

Exploitable or potentially exploitable deposits of critical metals, such as rare-earth (REE) and high-field-strength elements (HFSE), are commonly associated with alkaline or peralkaline igneous rocks. However, the origin, transport and concentration of these metals in peralkaline systems remains poorly understood. This study presents the results of a mineralogical and geochemical investigation of the Na-metasomatism of alkali amphiboles and clinopyroxenes from a barren peralkaline granite pluton in NE China, to assess the remobilization and redistribution of REE and HFSE during magmatic-hydrothermal evolution. Alkali amphiboles and aegirine-augites from the peralkaline granites show evolutionary trends from sodic-calcic to sodic compositions, with increasing REE and HFSE concentrations as a function of increasing Na-index [Na # , defined as molar Na/(Na+Ca) ratios]. The Na-amphiboles (i.e., arfvedsonite) and aegirine-augites can be subsequently altered, or breakdown, to form hydrothermal aegirine during late- or post-magmatic alteration. Representative compositions analyzed by in-situ LA-ICPMS show that the primary aegirine-augites have high and variable REE (2194-3627 ppm) and HFSE (4194-16,862 ppm) contents, suggesting that these critical metals can be scavenged by alkali amphiboles and aegirine-augites. Compared to the primary aegirine-augites, the presentative early replacement aegirine (Aeg-I, Na # = 0.91-0.94) has notably lower REE (1484-1972) and HFSE (4351-5621) contents. In contrast, the late hydrothermal aegirine (Aeg-II, Na # = 0.92-0.96) has significantly lower REE (317-456 ppm) and HFSE (6.44-72.2 ppm) contents. Given that the increasing Na # from aegirine-augites to hydrothermal aegirines likely resulted from Na-metasomatism, a scavenging-release model can explain the remobilization of REE and HFSE in peralkaline granitic systems. The scavenging and release of REE and HFSE by Na-metasomatism provides key insights into the genesis of globally significant REE and HFSE deposits. The high Na-index of the hydrothermal aegirine might be useful as a geochemical indicator in the exploration for these critical-metals., Competing Interests: The authors declare that they have no conflicts of interest in this work., (© 2022 The Authors. Publishing Services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.)

In the present study, we investigated the combined effect of Colla Comus Cervi (CCC) and BMP7-overexpressing bone marrow-derived mesenchymal stem cells (BMSCs) on osteogenic induction and the treatment of avascular necrosis of the femoral head (ANFH). BMSCs were isolated from rats. BMP7-overexpressing BMSCs were generated by lentiviral-mediated gene transduction. Cell proliferation, alkaline phosphatase (ALP) activity, osteogenesis related gene expression, osteocalcin levels, and calcified nodules were quantified and compared between four groups: untreated controls, BMSCs cultured with CCC complex medium, BMP7-overexpressing BMSCs, and BMP7-overexpressing BMSCs cultured with CCC complex medium (CCC+BMP7). CCC+BMP7 BMSCs showed higher proliferation rate. ALP activity and osteaocalcin content were significantly increased in CCC+BMP7 BMSCs. The osteogenesis related genes, COLI, and integrin-α2, -α5, and -β1, were expressed significantly higher in CCC+BMP7 BMSCs. The number of calcified nodules in the CCC+BMP7 group was significantly higher than that in other groups. For in vivo assays, ANFH was induced in rats, and BMSCs were injected into the femoral head of the lower left extremity. In rats with induced ANFH, general observation scores of the CCC+BMP7 injected group were significantly higher than the model group. X-ray and microscopic observations revealed that ANFH was significantly improved and femoral head cells gradually recovered in rats treated with CCC+BMP7 BMSCs. Our results suggest that CCC+BMP7 significantly promote the proliferation and osteogenic differentiation of BMSCs in vitm. CCC+BMP7 BMSCs promote the ability of repairing ANFH in rats, providing a new therapeutic paradigm for the treatment of ANFH.

Cretaceous represents one of the hottest greenhouse periods in the Earth's history, but some recent studies suggest that small ice caps might be present in non-polar regions during certain periods in the Early Cretaceous. Here we report extremely negative δ(18)O values of -18.12‰ to -13.19‰ for early Aptian hydrothermal zircon from an A-type granite at Baerzhe in northeastern China. Given that A-type granite is anhydrous and that magmatic zircon of the Baerzhe granite has δ(18)O value close to mantle values, the extremely negative δ(18)O values for hydrothermal zircon are attributed to addition of meteoric water with extremely low δ(18)O, mostly likely transported by glaciers. Considering the paleoaltitude of the region, continental glaciation is suggested to occur in the early Aptian, indicating much larger temperature fluctuations than previously thought during the supergreenhouse Cretaceous. This may have impact on the evolution of major organism in the Jehol Group during this period.