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The nickel content of nickel-based high-temperature alloy is between 50% and 70%, and the alloy contents of chromium, iron, cobalt, molybdenum, aluminum, titanium and tungsten are within 20%. A method of high resolution plasma mass spectrometry was established to determine the trace elements in nickel-based high-temperature alloy. According to the principle of large isotope abundance, small interference and high sensitivity, the isotopes and resolution of the elements to be measured were optimized, the interferences of most of the multi-atom and double-charged ions were effectively eliminated. The mass spectral interferences of matrix, compositions of alloy and dissolving acid on the trace elements were investigated. The appropriate internal standard of caesium was selected to overcome the matrix effect and reduce the signal drift. Chromium was extracted by methylisobutylone, the extraction efficiency reached up to 99.7%, which eliminated the mass spectral interference of principal component molybdenum in the nickel-based high-temperature alloy. The linear correlation coefficient of the calibration curve was greater than 0.999, and the method detection limit was between 0.002 1 and 0.074 μg/g. The trace elements in the reference material was analyzed, the relative standard deviation (RSD, n=6) was between 2.9% and 7.8%, and the measured value was very consistent with the standard value. This method is simple, fast, accurate and reliable, which can meet the requirement of trace elements determination in nickel-based high-temperature alloy.

The dolomite reservoirs in the fourth member of Leikoupo formation of the western Sichuan gas field have good prospects for natural gas exploration and development. However, the conventional and one-dimensional nuclear magnetic resonance (1D NMR) logging data are not sufficient for a definitive classification of the reservoir fluid type, likely because of heterogeneity of the reservoirs. Through geological characteristics analysis, log response analysis and two-dimensional (2D) NMR experiment, the environmental factors and technical parameters leading to the differences between the laboratory results and actual logging data were determined. According to the analysis of T2-T1 and T1/T2 (R) differences, the distribution range of drilling fluid, bound fluid, movable water and natural gas signals in the 2D NMR spectra was delineated to build a gas-water 2D NMR identification chart. The results obtained using the identification chart were verified with the actual drilling test results. Complementary to conventional and 1D NMR logging, the 2D NMR identification method was proposed, and can be used to determine the fluid properties in the dolomite reservoirs effectively.

Formation porosity can be calculated from one-dimensional nuclear magnetic resonance (NMR) logging data with a fixed cutoff value and the volume model of conventional logging data. However, the porosity calculated with this method often appears to be overestimated in the enlarged hole section. In this work, the calculation methods for T2 and T1 nuclear magnetic porosity from NMR results of core samples and two-dimensional NMR logging data were investigated. Firstly, the characteristics of NMR relaxation spectra of fluids at different pore sizes were obtained and used to analyze the distribution range of pore diameter and affecting factors of the cutoff value of the drilling fluid peak. A model for estimating the cutoff value of the drilling fluid relaxation time was then established. A method for calculating the effective porosity was then proposed with variable cutoff value of clay bond water relaxation time, according to the deterministic principle about cutoff value of clay bond water relaxation time in un-enlarged and enlarged hole section. The method proposed was applied to the data from many wells, and demonstrated better accuracy than the traditional method using T1 distribution spectra. The method can effectively solve the problem of overestimated porosity in the enlarged hole section and meet the requirement for reservoir evaluation.

BACKGROUND Iron is the most abundant element on earth with variable valences. It is widely distributed in various minerals, rocks, fluids and organisms, and is involved in diagenesis, mineralization, hydrothermal activities and life activities. The study of iron isotope composition provides important information for geochemistry, astrochemistry and biochemistry. The accurate measurement of Fe isotopes is an important basis for the development of related research. OBJECTIVES To summarize the research progress of Fe isotope measurement technology. METHODS The current chemical separation and purification methods and main instrumental analysis techniques commonly used for iron isotopes, were compared and analyzed in this review, and the mechanism of different types of fractionations during mass spectrometry were discussed. These advances included:(1) Improvement of anion resin during determination of iron isotope by solution method; (2) Mass spectrometry development from traditional thermal ionization mass spectrometry to multi-collector inductively coupled plasma mass spectrometry; (3) Development of laser in situ analytical technology. On this basis, the steps and calibration methods that would cause iron isotope fractionation during the analysis were summarized, and the advantages and disadvantages of different analytical methods were reviewed. RESULTS The analysis process of solution method was long and complicated, but the precision was high (0.03‰, 2SD) and the method was stable. In situ iron isotope analysis method developed from nanosecond laser denudation to femtosecond laser denudation, with shorter pulse duration, higher pulse peak intensity (up to 1012W), and focusing intensity exceeding 1020W/cm2. In situ iron isotope analysis method was fast and had high spatial resolution, which can be used to discuss the geochemical process from the microscopic perspective. However, the presence of matrix effects limited the widespread use of iron isotopes. CONCLUSIONS Shortening solution analysis process and developing a series of matrix-matched standard samples are the research direction of iron isotope analysis.

143Nd/144Nd isotope ratio is the key for Sm-Nd isotope method. The 143Nd/144Nd isotope ratio of geological samples varies within a small range, and thus the 143Nd/144Nd isotope ratio analysis must be precise. In order to obtain high precision and high accuracy of the analytical data, the analysis process involving Nd isotope reference material plays an important role. The previous Nd isotope reference material is neodymium oxide, which have been exhausted in recent three decades. A national reference material of 143Nd/144Nd isotope ratio was introduced in this paper, which shows sufficient homogeneity and stability. The certified value of this reference material was determined by eleven participating laboratories using MC-TIMS and MC-ICP-MS. The 143Nd/144Nd isotope ratio value for the reference material is 0.512438, with a combined expanded uncertainty (k=2) of 5×10-6. The standard solution gets certification in May, 2015 and the Serial number is GSB 04-3258—2015. The standard solution can be used for quality monitoring of the equipment calibration and analysis process during the 143Nd/144Nd ratio determination for geology, resources, ocean, environment, archaeological and other type samples.

Non-traditional lithium isotope is a frontier in isotope geochemistry and has been applied to the studies of Solid Earth Sciences, such as the lithosphere and fluids from the Earth's surface to the mantle. Lithium isotopic compositions of 7 standard reference materials BHVO-2, JB-2, BCR-2, AGV-2, NKT-1, L-SVEC and IRMM-016 are reported in this paper. The rock standards were digested with HNO3-HF mixed acids. Cation exchange resin AG50W-X8 was used for the separation of Li from other elements. Li isotope ratios were determined by Multi-Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS), and isotopic mass fractionation was calibrated by standard-sample bracketing. The Li isotopic compositions and the analytical uncertainties (reported in 2SD) of analyzed standard reference materials were: 7LiBHVO-2-L-SVEC=4.7‰±1.0‰ (n=53), 7LiJB-2-L-SVEC=4.9‰±1.0‰ (n=20), 7LiBCR-2-L-SVEC=4.4‰±0.8‰ (n=8), 7LiAGV-2-L-SVEC=6.1‰±0.4‰ (n=14), 7LiNKT-1-L-SVEC=9.8‰±0.2‰ (n=3), 7LiL-SVEC-L-SVEC=-0.3‰±0.3‰ (n=10), 7LiIRMM-016-L-SVEC=0.0‰±0.5‰ (n=10). The results were in good agreement with published data within analytical uncertainties. The accuracy of this method is about ±0.5‰ and the long-term external precision (2SD) of replicate analyses including the entire pretreatment procedure is less than ±1.0‰, and is similar to the state of the art method. The reported data of 7 standard reference materials provided a new standard framework for Li isotope research, and enabled the evaluation of the quality of data retrieved from geological samples. The influence of sample size was also assessed by loading different amounts of separated IRMM-016 solutions. The results show that when the lithium concentration has reached 100 μg/L, the measured lithium isotopic compositions are in coincidence with the accepted value within uncertainty, and the sample size does not affect the accuracy of measurements.

The Epo intrusion with an exposed area of 200 km2, is mainly composed of biotite monzonitic granite, and is located on the western margin of the Yudu-Qingtang basin, the conjunction of E-W trending Nanling tectonic-magmatic belt and the NNE trending Wuyishan tectonic belt. Situated in such a special tectonic position, this region is advantageous to mineralization. The Yinkeng ore field, which lies to the west of the Epo intrusion, consists of Au-Ag-Pb-Zn and W polymetallic deposits. On the basis of field survey, zircon U-Pb dating for Epo biotite monzonitic granite has been carried out by Laser Ablation-Multicollector-Inductively Coupled Plasma-Mass Spectrometry (LA-MC-ICP-MS). Magma series and petrogenesis have been discussed according to geochemical data, and metallogenetic potentiality of the intrusion has been studied by comparing with other metallogenetic granitic bodies in the district. Analysis results show that the diagenetic age of Epo granite is (412.5±1.7) Ma. The granite contains abundant aluminium minerals, such as muscovite and sillimanite. Major and trace elements indicate that Epo granite is strongly peraluminous S-type granite, and belongs to the High potassium calc alkaline-shoshonite series. The pluton stemmed from Neoproterozoic metamorphic shale by remelting and intruding during the Late Caledonian period. Comparative research with Caledonian and Yanshanian W-Sn metallogenetic granites shows that W and Sn had been concentrated during the formation of Epo granite. Proof that the previous Rb-Sr whole rock isochron age (307 Ma) represents a late geological event after the diagenesis period is given in this paper, and Caledonian granites have potential for W-Sn mineralization.

After years of rapid mining, the shallow resources of the polymetallic tin ore bodies in the Bali area, Dachang, have been depleted. Therefore, deep prospecting is imminent. The REEs of limestone samples in the Middle/Upper Devonian from drill holes of ZK39-1 in the Bali area, Dachang, by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) have been analysed and the process is presented in this paper. The drilling depth is 1580 m, which is one of the world's deepest hole drilling. The results showed that the amount of the REES (∑REEs) is 3.49-261.07 μg/g with a large range. ∑REEs (3.49-45.81 μg/g) of drill core samples at 1100-1580 m are significantly lower than ∑REEs (188.96-242.36 μg/g) at 1100 m above, which is about 10 times the regional background values and far more than common sedimentary limestone. The ratios of light rare earth elements and heavy rare earth elements (LREEs/HREEs) had a range of 2.96-10.04, which meant that there was a high degree of fractionation between light rare earth elements and heavy rare earth elements. δEu values varied between 0.11 and 1.00 and δCe values ranged from 0.53 to 0.99. The Chondrite-normalized distribution pattern chart was ‘right inclination’ LREE enrichment type. Samples from1100-1580 m had a negative Eu anomaly and Ce had a negative anomaly decreasing from top to bottom. The chondrite-normalized pattern chart of 1100-1580 m drill core samples was similar to that of granite from Dachang, indicating that the carbonates were altered by granite magma and that there might be deep magmatic hydrothermal origin or silicon skarn-type polymetallic mineralization near the granite contact zone, known as the ‘third metallogenic spatial’.

Apatite is a common accessory mineral, having a high Sr-Nd content and a low Rb content. The precise determination of micro-area Sr-Nd isotopic composition for apatite will provide important geochemical information for discussing the details of the geological process. Laser Ablation Multi-collector Inductively Coupled Plasma-Mass Spectrometry (LA-MC-ICPMS) technique has the characteristics of rapid analysis, high analytical precision and high spatial resolution, and is particularly suitable for Sr-Nd isotopic analysis of a large quantity of fine-grained apatite samples. The precise deduction of isotopic interference and calibration of instrument mass bias are crucial for in-situ analysis to obtain Sr-Nd isotopic ratio. In this article a method is described, which adopts LA-MC-ICPMS and combines with the newly published method for deduction of interferences, like Kr, Rb, divalent ions of REEs and calcium-containing polymer for Sr isotopes, Sm for Nd isotopes. The calibration of instrument mass bias is carried out, and the in-situ Sr-Nd isotopic analysis approach for apatite is established. The test results of Durango apatite standard, Apatite 1 and PE show that Sr-Nd isotopic composition of apatite sample with high Sr-Nd content can be accurately determined. The specific results are consistent with literature or the measured values by Thermal Ionization Mass Spectrometry (TIMS) within error. The measurement precision of Sr isotopes is < 0.015% (2SD), and that of Nd isotopes is < 0.005% (2SD). The established method is applied for Sr-Nd isotopic analysis of Durango apatite standard, Apatite 1 and PE (laboratory standard), respectively. The analysis results indicate that the Sr-Nd isotopic compositions of the three apatite samples are basically consistent, and can serve as ideal reference samples for in-situ Sr-Nd isotopic analysis.

The Gacun deposit is a typical Volcanic Hosted Massive Sulfide (VHMS) associated with Late Triassic seafloor calc-alkaline felsic volcanics. Studies of zircon ages, petrology, major and trace element geochemistry, and Sr-Nd-Hf isotope geochemistry of volcanic rocks from the Northern Yidun arc were undertaken in this paper. We reshaped the Gacun magmatic system activity time, defined the origin of magma evolution, and proposed a metallogenic model of the deposit. Whole-rock major element compositions of the magmatic rocks in the Northern Yidun island arc indicate that they are a complete basalt–andesite–dacite–rhyolite assemblage, showing three obvious stages of composition evolution. They are enriched in large-ion lithophile and light rare earth elements, but depleted in high field-strength and heavy rare earth elements, with weak-to-negligible Eu anomalies (obvious in rhyolite). These geochemical features indicate that the Northern Yidun island arc is a magmatic arc based on ancient continental crust. The Ganzi–Litang oceanic subduction induced mantle melting and produced calc-alkaline basaltic magma, while the MASH processes at the bottom of the crust produced andesitic magma. Part of the andesite magma erupted to form andesite lava. The remaining part was mixed with magma produced via anatexis of ancient crust (approximately 20%–40% of the ancient crustal component), forming the ore-bearing rhyolite. Zircon U-Pb age data defines Gacun magmatic–hydrothermal mineralization sequence of events: At 238 Ma, arc magmatism led to the formation of andesite in the eastern part of the deposit. At 233 Ma, in the arc zone (the western part of Gacun deposit), a large-scale bimodal magmatism formed the main ore-bearing rock series of Gacun deposit, rhyolitic volcanic rocks. At 221 Ma, volcanic eruptions tended to end and sub-volcanic intrusion occurred, forming a lava dome, which was located under the ore-bearing rhyolitic volcanic rocks. The lava dome acted as a thermal engine and promoted hydrothermal circulation. The hydrothermal activity reached a peak at 217 ± 1 Ma, and the Gacun VHMS deposit was formed. [ABSTRACT FROM AUTHOR]

Voluminous Neoproterozoic granitoid sheets of the Imorona–Itsindro Suite are important components of exposed basement in west-central Madagascar. Here, we report precise new zircon U–Pb ages and whole-rock geochemistry for granitoids within the Maevatanana area of Madagascar. The new laser ablation inductively coupled plasma mass spectrometry zircon U–Pb dating undertaken during this study indicates that Antanimbary granitoid and Antasakoamamy granitoid were emplaced at 747 ± 9 Ma and 729 ± 9–727 ± 8 Ma, respectively. Geochemically, the Antanimbary granitoids show poor Nb, Ta anomalies, pronounced positive Zr anomalies, and are K-rich (K2O/Na2O > 1), but the Antasakoamamy granitoids are relatively depleted in Nb, Ta, show slightly negative Zr anomalies, and are Na-rich (Na2O/K2O > 1). Both suites contain zircons with strongly negativeεHf(t), indicating participation of much older (Palaeoproterozoic and Archaean) crust. Their geochemical characteristics, along with the use of various discrimination diagrams, reveals that crustal delamination and asthenospheric upwelling resulted in crustal extension of the region before ~747 Ma, with subsequent lithospheric subduction and arc magmatism after 729–727 Ma. [ABSTRACT FROM AUTHOR]