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

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

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

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

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

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

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

Deep-water canyon systems can provide important sandstone reservoirs for deep-water oil and gas exploration in the South China Sea; however, the sedimentary provenance of the Central Canyon in the Qiongdongnan Basin remains controversial. In this work, detrital zircon grains from three drilling sandstones in the Upper Miocene Huangliu Formation in the western part of the Central Canyon were analysed by LA-ICP-MS for U-Pb ages, in order to constrain their provenance. One hundred and ninety-one zircon grains yield concordant U-Pb ages ranging from 28.6 to 3285 Ma. Most of them show oscillatory or linear zoning in CL-images and high Th/U ratios (>0.1), suggesting that they are magmatic zircons. Three major age clusters at about 30 Ma ( N=6), 220-270 Ma ( N=29), and 420-440 Ma ( N=13), and five minor age clusters at 70-110 Ma ( N=7), 150-170 Ma ( N=4), 800-850 Ma ( N=11), 1800-2000 Ma ( N=16), and 2400-2600 Ma ( N=7), can be identified in the age spectrum, which are very similar to those of the Upper Miocene sandstones and modern river sands in the Red River area, but different from those of other nearby regions (e.g., Hainan Island, the Pearl River area, and the Mekong River area) in Southeast Asia. The major age peak at about 30 Ma in our samples is consistent with the timing of tectonothermal events in the Red River Fault Zone. Therefore, we suggest that the provenance of the western part of the Central Canyon, in the Qiongdongnan Basin, was fed dominantly by the Paleo-Red River system during the Late Miocene. [ABSTRACT FROM AUTHOR]

The Neogene sediments of Gansu Group from northwestern China contain eolian and fluvial deposits. The origins of these sediments are very important for exploring the onset of Asian inland aridification, the pattern of paleo-atmospheric circulation, and the regional tectonics and geomorphic evolution during the Miocene. Here we present detrital-zircon age spectra of typical eolian and fluvial deposits from highlands and subsidence basin, and compare them with those of surrounding eroded mountain (such as the West Qinling Mountains and Liupan Mountains) materials and Quaternary loess derived from the Asian inlands. The results reveal that (1) the detrital-zircon age spectrum of the Miocene eolian sample is remarkably different from the eroded materials of the West Qinling Mountains and the Miocene fluvial deposits from Tianshui region, but very similar to the Quaternary loess deposits. This indicates that the provenance of Miocene eolian sediments is similar with the Quaternary loess, and thus further confirms the previous conclusions that the distribution of Asian arid lands and the pattern of atmospheric circulation during the Miocene are broadly similar with the Quaternary. (2) The detrital-zircon age spectrum of the fluvial deposits (with age about 11.5 Ma) from Tianshui region is different from the eroded materials of West Qinling Mountains, but similar with that of the Liupan Mountains to the east, which may suggest that the Liupan Mountains have already been exhumed by 11.5 Ma. [ABSTRACT FROM AUTHOR]

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

Garnet-rich granulite xenoliths collected from the Hannuoba basalts, the North China craton (NCC), were studied to reveal the Mesozoic crust-mantle interaction. These xenoliths are characterized by low SiO (37.7 wt.%-46.0 wt.%) and high AlO (10.8 wt.%-17.9 wt.%) contents. Their Mg (60-75, Mg=100×Mg/(Mg+Fe), atomic number) are relatively low for their low SiO contents. They have low rare-earth element (REE) contents and LREE-rich REE patterns, and show remarkable enrichments in Sr relative to the adjacent REE. Some of them exhibit convex REE patterns with a maximum at Nd and remarkably positive Eu anomalies. Taking into account their high garnet mode (generally >30%), these features suggest that they are high-pressure metamorphic products of low-pressure cumulates (e.g., gabbro) after it had been depressed into the garnet stability field. They have evolved Nd and Sr isotopic compositions (Nd/Nd=0.511 763-0.512 173, Sr/Sr=0.705 34-0.706 99) and fall in the trend defined by the >110 Ma Mesozoic basalts and high-Mg andesites from the NCC. Zircon U-Pb dating by LA-ICP-MS shows a wide age range from 83 to 2 581 Ma, most of which cluster in 83-134 Ma. CL images of some Mesozoic zircons from the granulites show typical features of igneous zircons, providing direct evidence for the Mesozoic underplating event in this area. Neither peridotite-derived basaltic underplating model nor residue model of ancient lower crust after lithospheric thinning alone can reasonably explain the above features of the garnet-rich granulite xenoliths. Combined with the previous research, we propose that most of the granulite xenoliths from the Hannuoba basalts are products of the Mesozoic magmatic underplating and mixing with the pre-existing lower crust (i.e., AFC process). However, the melts could be mostly derived from partial melting of basaltic layers that were previously subducted (a fossil oceanic slab) or underplated into the base of the lithospheric mantle, or from partial melting of Archean lithospheric mantle that was variably hybridised by melts derived from foundered lower crustal eclogite, although it cannot be excluded that some of the melts were derived from depleted mantle peridotite. In other words, parent melts of most granulite xenoliths could share the same petrogenesis as the >110 Ma Mesozoic basalts from the NCC. [ABSTRACT FROM AUTHOR]

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

Carbon in rocks and its rate of exchange with the exosphere is the least understood part of the carbon cycle. The amount of carbonate subducted as sediments and ocean crust is poorly known, but essential to mass balance the cycle. We describe carbonatite melt pockets in mantle peridotite xenoliths from Dalihu (northern China), which provide firsthand evidence for the recycling of carbonate sediments within the subduction system. These pockets retain the low trace element contents and δ18OSMOW = 21.1 ± 0.3 of argillaceous carbonate sediments, representing wholesale melting of carbonates instead of filtered recycling of carbon by redox freezing and melting. They also contain microscopic diamonds, partly transformed to graphite, indicating that depths >120 km were reached, as well as a bizarre mixture of carbides and metal alloys indicative of extremely reducing conditions. Subducted carbonates form diapirs that move rapidly upwards through the mantle wedge, reacting with peridotite, assimilating silicate minerals and releasing CO2, thus promoting their rapid emplacement. The assimilation process produces very local disequilibrium and divergent redox conditions that result in carbides and metal alloys, which help to interpret other occurrences of rock exhumed from ultra-deep conditions. [ABSTRACT FROM AUTHOR]