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

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

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

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

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

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

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]

To overcome the major shortcomings in conventional ICP-MS analysis with sample introduction by nebulization, a new solution sampling method was developed using laser ablation (LA). With this sampling method, water-related interferences were reduced by 1–2 orders of magnitude, the effects of which are similar to those obtained in membrane desolvation ICP-MS. Another important advantage of this method is that the matrix effects became insignificant in the ICP-MS analysis whether employing a matrix with the sample dilution factor varying between 80 and 2000 or an acid matrix ranging from 2% to 30% (v/v) HNO3. Compared with LA-ICP-MS analysis of solids, this sampling method exhibited 70–250 times improvement in signal sensitivity and the detection limits for most elements were two orders of magnitude lower. Unlike solid sample analysis, the commonly observed time-resolved element fractionation during laser ablation was negligible in solution sampling by LA. With the widely used reference material NIST 610 silicate glass as the external calibration standard and indium as the internal standard element, major and trace elements in a series of geological reference materials (ranging from mafic to felsic rocks) were successfully determined: the feasibility was verified with accuracies within 10% for 45 elements, and most of the precisions were reported as RSD better than 7%. Besides, due to the high tolerance of matrix effects, this method is comparatively green and environment friendly because of the minute consumption of acid and ultrapure water during the sample preparation process, which was reduced by 20–100 times compared to that in the conventional nebulization method. Being simple and effective, this method opens up a new prospect for the solution sampling of ICP-MS analysis. [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]

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

The processes responsible for the origin and evolution of Early Archean continental crust are not properly understood. Questions regarding the pattern of crustal growth (episodic vs. continuous) and the role of crust-mantle interaction in the temporal change of crustal composition and thickness are still being widely debated. In order to address the above issues, we present whole-rock geochemistry and detrital zircon U-Pb-Hf isotopes, and trace-element data from Mesoarchean clastic rocks of two selected greenstone belts of western Dharwar Craton. The mineralogically mature character of the sampled sandstones along with their high K 2 O/Na 2 O, Rb/Sr and CIA values, relatively enriched concentrations of La and Th over Cr and Sc, variably negative Eu-anomaly, and high U/Yb values of detrital zircons are indicative of their derivation from strongly weathered stable continental provenance dominated by low-HREE TTGs and K-rich granites of shallow crustal origin. Detrital zircon U-Pb ages indicate the maximum age of deposition for these sandstones is ∼3.1 Ga. The detrital zircon U-Pb and Lu-Hf data suggest two major crust formation events at 3.54–3.33 Ga and 3.27–3.12, mainly via juvenile crustal addition and subsequent rapid reworking. Besides, ∼3.6 Ga detrital zircons with negative εHft values suggest that the antiquity of the western Dharwar Craton can be traced back at least up to 3.8 Ga. Reworking of the older continental crust occurred during ∼ 3.25 Ga and ∼ 3.15–3.07 Ga, the last one represented by emplacement of K-rich granites. Zircon trace element ratios indicate a maximum increase in crustal thickness at ∼3.2 Ga followed by a crustal thinning at around ∼3.15 Ga. The detrital record in combination with geological setting suggests an episodic crustal growth and reworking in the western Dharwar Craton during Paleoarchean to early Mesoarchean period which was possibly related to intraplate processes. • Juvenile crust in Western Dharwar Craton formed at 3.54–3.33 Ga. • The juvenile crust reworked during 3.27–3.12 Ga. • Reworking of older crust occurred at ∼3.25 Ga, ∼3.15–3.07 Ga and ∼ 3.02 Ga. • Maximum crustal thickness attained at ∼3.2 Ga followed by thinning up to ∼3.1 Ga. • Link between crustal thickening and partial convective overturn is suggested. [ABSTRACT FROM AUTHOR]

Abstract: The trace element, Li and Sr isotopic compositions of major minerals in peridotite xenoliths from Kuandian, North China Craton (NCC) were analyzed in situ to investigate Pacific slab subduction-related mantle modification beneath the eastern NCC. The 87Sr/86Sr ratios (0.70282–0.70553) are positively correlated with the La/Nb and U/Nb ratios for clinopyroxenes (Cpx). Based on the trace element distribution patterns, three types of Cpx were identified. Type 1 Cpx are characterized by significant Nb–Ta–Ti depletions and the highest Sr isotopic ratios (up to 0.70553); Type 2 Cpx display Nb (or Ta) depletions and highly variable Nb and Ta fractionation; and Type 3 Cpx show no significant Nb or Ta depletion or even weak Ta enrichment and have the lowest Sr isotopic ratios (0.70282–0.70323). Some Cpx display a pattern of increasing Ca+Mg±Si from the cores to the rims, indicating addition of Ca+Mg±Si-rich fluids derived from a serpentinized peridotite layer above the subducting slab. These features indicate an ancient mantle metasomatic event associated with the subduction of the altered Pacific oceanic crust, which may contribute substantially to the destruction of the eastern NCC. The variations in the Li contents and isotopic compositions of major minerals in the Kuandian peridotite xenoliths encode both the melt/fluid metasomatism and the cooling process. The Li contents in the Cpx (up to 34.8ppm) and orthopyroxenes (Opx) (up to 28.0ppm) are typically higher than those in the coexisting olivines (Ol) (<9.19ppm), suggesting silicate melt metasomatism. Considering the rapid diffusion rate of Li in minerals at mantle temperature, the Li enrichment and low δ7Li values in the rims of most Ol, Cpx and Opx may have arisen from diffusive fractionation due to faster diffusion of 6Li compared to 7Li during a latest Li-rich melt/fluid metasomatic process shortly before the host magma eruption. On the other hand, a few Ol grains show decreased Li contents and higher δ7Li values from the cores to the rims. This could imply Li isotope fractionation caused by cooling-induced Li redistribution during and/or after the host magma eruption, because D Li Ol/Cpx decreases significantly with decreasing temperature and 6Li diffuses faster than 7Li. [Copyright &y& Elsevier]

Abstract: A combined study of zircon U–Pb and Lu–Hf isotopes and whole rock major and trace elements and Sr–Nd isotopes has been conducted for 10 tonalitic–trondhjemitic–granodioritic (TTG) and granitic gneisses from the Kongling terrain, the only known Archean microcontinent in the Yangtze craton, South China. The results reveal a significant magmatic event at ∼2.6–2.7Ga, in addition to the previously reported ∼2.9Ga and ∼3.2–3.3Ga magmatism. The ∼2.6–2.7Ga rocks show relatively high REE (530–1074ppm), apparently negative Eu anomaly (Eu/Eu*=0.22–0.35), low #Mg (19.51–22.63) and low LaN/YbN (10.3–24.2). Besides, they have high K-feldspar proportion and relatively evaluated (K2O+Na2O)/CaO, TFeO/MgO, Zr, Nb, Ce and Y contents. Their 10,000×Ga/Al ratios range between 3.00 and 3.54. All these features suggest that the protoliths of these gneisses are A-type granites. Most of the ∼2.6–2.7Ga zircon grains have ɛ Hf(t) values >0 (up to 7.93, close to the depleted mantle value). This clearly indicates a considerably higher proportion of new crustal components in the ∼2.6–2.7Ga granitoids compared to the ∼3.2–3.3Ga and ∼2.9Ga TTGs. Our results support the conclusion of worldwide studies of igneous and detrital zircons that age peaks at 2.65–2.76Ga represent increases in the volume of juvenile continental crust. The present study also confirms the existence of the two older magmatic events in the Kongling terrain. Both whole rock ɛ Nd(t) values (−3.74 to 1.59) and the zircon ɛ Hf(t) values (−11.18 to 3.55) for the ∼2.9Ga TTG and the Hf isotopes of ∼3.2–3.3Ga igneous zircons (−7.37 to 3.12) are chondritic or subchondritic, suggesting that they were mainly generated by reworking of older rocks with a small amount of new crustal additions. [Copyright &y& Elsevier]

Abstract: Bulk element and isotopic compositions, single zircon U–Pb ages and trace element compositions of the Triassic high-Mg adakitic andesites (HMAs) from the Linxi area in the Inner Mongolia–Daxinganling orogenic belt (IMDOB) were studied to understand the area''s petrogenesis and implications for Phanerozoic crustal growth. The Linxi HMAs are characterized by typical features of high-SiO2 adakite with high Mg# and high Cr and Ni contents. Coarse clinopyroxene (cpx) phenocrysts with reverse zoning were found. These cpx phenocrysts have cores with lower Mg# and Ni contents, and higher incompatible element contents (e.g., Zr and La) compared with their mantles and rims. Bulk rock Sr–Nd isotopic compositions (87Sr/86SrI =0.70382–0.70396 and εNd(t) =3.2–4.5) fall in the range of mid-ocean ridge basalts (MORB) and modern subduction-related adakites. Single zircon U–Pb dating by LA-ICP-MS suggests an eruption at ca. 238Ma. Combined with the tectonic setting and Precambrian zircon age spectrum, these features suggest that the Linxi HMAs could be derived from the subducted Paleo-Asian oceanic slab with sediments shed from the North China Craton and hybridized by peridotite in the mantle. Trace element-age variations of zircons indicate that the oceanic crust was formed during Carboniferous–early Permian times, and then subducted during ca. 270–260Ma. Melting of the subducted oceanic slab and hybridization by peridotite could have been initiated at ca. 250Ma. It is suggested that the southern accretionary zone between the North China Craton and the Solonker suture in the IMDOB, where the Linxi HMAs are located, could have been consolidated by Carboniferous–Permian times. This implies that the Linxi HMAs could have been derived from partial melting of a fossil oceanic slab after the subduction, and subduction-related melting might have been delayed if the slab was subducted under an old, cold craton. Although we are unsure of the true extent of the fossil oceanic slab, the genesis of the Linxi HMAs is essentially a snapshot of the melting of a subducted slab lagging behind subduction, and melting of the fossil oceanic slab could have played an important role in the Phanerozoic crustal growth in the IMDOB. [Copyright &y& Elsevier]

Abstract: Here we describe an internal standard-independent calibration strategy for LA–ICP-MS analysis of fifty-four major and trace elements in carbonate. Based on the normalization strategy of bulk components as 100%, the MRM-NoIS (calibrated against multiple silicate reference materials without using internal standard) was used to correct the matrix-dependent absolute amount of materials ablated during each run. Applying MRM-NoIS and using the MPI-DING reference glasses as reference materials for external calibration, analyses of carbonate standard MACS-3 generally agree with recommended values within 10% for most trace elements (better than 5% for REEs and major elements). Analyses of natural igneous calcite grains agree with the results of solution-ICP-MS values within 10% for Mg, Sc, Mn, Sr and REEs. The results indicate that, applying MRM-NoIS and using MPI-DING reference glasses as multiple reference materials for calibration, carbonate can be accurately analyzed in situ by LA–ICP-MS without applying internal standardization and matrix matching external standards. Our results also indicate that the working value of Nb in carbonate pellet MACS-3 could be 53.4μg/g rather than 35.2μg/g given in the test of G-Probe 4. [Copyright &y& Elsevier]

The oxygen fugacity of a magma controlling element distribution and mobility is influenced by multiple factors including source composition and magmatic processes (e.g., assimilation and degassing). Here, whole-rock and in situ mineral analyses of the alkaline complex from the northern North China Craton are reported to investigate the influence of source composition and magmatic processes on the evolution of the melt oxidation state. The alkaline complex comprises orthoclase pyroxenites, pyroxene syenites, and syenites with similar mineral assemblages and trace element patterns. Consistent zircon and titanite U-Pb age of ~234 Ma is presented for the alkaline rocks. Their high large ion lithophile elements content, negative high field strength element anomalies, and high 87Sr/86Sr ratio suggest a metasomatized mantle origin by recycled crustal material. Magnetite and hematite inclusions were found in the early-crystallized minerals including clinopyroxene and apatite. Fluorapatites are characterized by high S (SO 3 up to 0.64 wt%) and low Mn contents, with estimated ΔFMQ higher than +3. These features together indicate a primary oxidized magma inherited from the metasomatized mantle. However, inclusion-rich fluorapatites with decreasing S and increasing Mn content from the core to the rim were found in some pyroxene syenites. Moreover, the S content of inclusion-rich fluorapatite from these pyroxene syenites is lower than that of other rock types in the complex, which may correspond to a decrease in oxygen fugacity of ~2.5 log units. These features suggest that the oxidized magma was later transformed into reduced magma. Oriented Cu-rich sulfide in inclusion-rich fluorapatite formed during the reducing event. δ65Cu of the pyroxene syenite with inclusion-rich fluorapatite (−0.06 to −0.24‰) and sulfides in fluorapatite (−0.26‰) are lighter than those of other rock types (+0.30 to +0.43‰), suggesting that the sulfides were derived from extraneous materials via magma assimilation. Variable and high 87Sr/86Sr ratios (0.7071–0.7085) in titanites and high-207Pb/206Pb rims of zoned K-feldspar in the pyroxene syenite imply that the reduced extraneous materials were derived from ancient crust. Overall, in situ mineral analyses and Cu isotopes indicate a direct link between the transformation of alkaline magma from an oxidized to a reduced state with source composition and magmatic processes, and improve our understanding of element mobility and distribution. • Oxidized alkaline magma derived from metasomatized mantle by carbonated melts. • Varied S and Mn in apatite imply the transformation of oxidized magma to reduced. • Sr–Pb–Cu isotopes suggest the redox changes induced by magma hybridization. • Redox state of alkaline magma control element mobility and mineralization. [ABSTRACT FROM AUTHOR]

• Rutile xenocrysts were captured from the basement by the Yangyuan carbonatites. • The Zr-in-rutile thermometer records formation of the rutiles at 743–932 °C. • Cr and Nb contents and Hf isotopes in rutiles support pelitic granulite protoliths. • U-Pb rutile cooling ages peak at 1810 ± 4 Ma, 1735 ± 5 Ma, and 1673 ± 8 Ma. • In combination with dating results from other systems yields episodic cooling path. The amalgamation of the North China Craton along the Trans-North China Orogen at ~1.85 Ga has been widely discussed, but its thermal evolution after amalgamation is relatively poorly constrained. This study presents U-Pb ages, trace element compositions, and Hf isotopes of rutile xenocrysts carried by the Yangyuan Cenozoic carbonatites, revealing an episodic cooling history of the Trans-North China Orogen. The Zr-in-rutile thermometer records formation of the rutiles under granulite facies at 743–932 °C. Cr and Nb concentrations in rutiles support a pelitic protolith, which is consistent with 176Hf/177Hf ratios that are close to zircons from pelitic granulites in the orogen. U-Pb ages of the rutiles are cooling ages, for which three populations can be clearly delineated. In combination with dating results from other systems, three episodes of cooling can be identified: [1] active cooling after the ~1.85 Ga peak metamorphism, with a cooling rate increasing from 7.9 °C/Ma in the period 1850–1810 Ma to 15.3 °C/Ma at 1810–1792 Ma; [2] active cooling after mantle upwelling at ~1.78 Ga, with cooling rate increasing from 8.7 °C/Ma at 1780–1735 Ma to 17.2 °C/Ma between 1735 and 1719 Ma; [3] passive cooling after a rifting event at ~1.68 Ga, with cooling rate decreasing from 20.6 °C/Ma at 1680–1673 Ma to 6.9 °C/Ma in the period 1673–1633 Ma. The first two episodes correspond to exhumation-related cooling, while the last episode resulted from the rift-to-drift transition of the North China Craton due to increasing distance from the heat source during break-up of the Columbia supercontinent. [ABSTRACT FROM AUTHOR]