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OBJECTIVES Ion-adsorption type rare earth ore is extremely important in China and rare in the world. It is China's dominant mineral resource. At present, all the rare earth elements in the existing REE reference materials are oxide minerals, not ion-adsorption type, and cannot be exchanged with strong electrolytes. These reference materials cannot be used to monitor the leaching process of ion-adsorption type REE. METHODS The samples were collected from the typical ion-adsorption type REE weathering crust in Jiangxi Province. After being dried and ball-milled to 200 mesh, they were mixed for 1.5h. The contents of rare earth elements in the ionic phase were analyzed to test the homogeneity by ammonium sulfate leaching and inductively coupled plasma-mass spectrometry (ICP-MS). RESULTS Results showed that the F values for the variance test were less than the threshold, which indicated a good homogeneity. The stability of monitoring samples was tested 4 times in two years, and no statistically significant changes were observed, indicating good stability of the samples. An accurate and reliable leaching analytical method was used in 8 technologically significant laboratories to finalize the contents of ionic phase rare earth elements. The determined values of nine monitoring samples were given by statistical calculation, including weighted average value and total uncertainty results which were from uncertainties in certified values, between-bottle homogeneity and long-term stability. These nine monitoring samples have certified values of 15 ionic phase rare earth elements except Sc. CONCLUSIONS The reference materials can be used to monitor the leaching process and provide metrological support for the analysis of rare earth elements in ionic phase during the evaluation and effective utilization of REE mineral resources.

BACKGROUND Strategic critical metal mineral resources including rare, dispersed, rare earth and platinum group elements play an increasingly critical role in emerging industries such as new materials, new energy and information technology. With the deepening of the geological survey of key mineral resources in China, the critical metal elements present new challenges to analytical techniques due to their complex matrix, large differences in different mineral contents, and unstable chemical properties. OBJECTIVES To introduce recent analytical techniques and applications for critical metal elements in different types of geological samples. METHODS Based on different chemical composition, the main matrices of critical metal elements were classified, mainly divided into silicate, carbonate, sulfate, tungstate, phosphate, oxide, sulfide and halide. For different types of rocks and minerals, chemical digestion was largely carried out by traditional dissolution methods such as the acid dissolution method (nitric acid-hydrofluoric acid combination, aqua regia) or alkali fusion methods. RESULTS The characteristics and application of commonly used instruments including electronic probe microanalyzer, inductively coupled plasma-mass spectrometry, inductively coupled plasma-optical emission spectroscopy, and X-ray fluorescence spectroscopy were reviewed. The problems during critical metal analysis including incomplete dissolution, low recovery, oxides and isobaric interference, inconsistency between samples and standard matrices were reviewed and corresponding solutions were proposed. CONCLUSIONS In situ microanalysis with the advantages of high efficiency, low cost, and high spatial resolution, and field on-site geoanalysis with its simple, fast and close to field work features are the main trends in the development of critical metal elements analytical techniques.

BACKGROUND The accurate determination of ionic phase rare earths in ion-adsorption rare earths is of great significance for the evaluation of rare earth ore bodies. Ionic phase rare earths are adsorbed on clay minerals in the form of hydroxyl or hydrated hydroxyls and can be exchanged and desorbed with strong electrolytes (Mg2+, NH4+, etc.) into solution. The former used ammonium sulfate as the leachate to achieve the desorption and extraction of rare earth ions in the ion phase, but the solution concentration, leaching process and other aspects of choice, leaching rates (60% to 90%) are different. There is no efficient and uniform leaching method conducive to the accurate determination of ionic phase rare earth elements. OBJECTIVES To establish a high-efficiency leaching process by ammonium sulfate solution and determine the accurate contents of ionic-phase rare earth elements. METHODS The leaching parameters (solid-to-liquid ratio, ammonium sulfate concentration, best sample weight, and soaking time) of rare-earth ions by ammonium sulfate were standardized through comparative experiments, which reduced the loss of ionic phase rare earth during leaching. The leaching rates were from 88% to 98%, and ICP-MS was used to accurately determine the ion phase rare earth component. RESULTS The detection limits are 0.05-5.11 ng/g, and the relative standard deviations (RSDs) are 1.80%-10.01% for volcanic rock, 1.06%-7.27% for metamorphic rock, and 1.72%-7.58% for sedimentary rock. CONCLUSIONS The analytical results of the collaborative laboratory verify the reliability and accuracy of the method. This method is easy to operate and has high analysis efficiency. It provides the base for the establishment of relevant industry standards and national standards.

BACKGROUND Os can be separated from the sample matrix by distillation, and the absorbing liquid can be introduced into ICP-MS directly, which is a key step of the molybdenite Re-Os isotopic age analysis. However, the Os signal intensity declines significantly after long time storage. According to the properties of OsO4, the possible causes may include:1) volatilization which reduces the Os content in the absorbing liquid, and 2) the reduction in which Os(Ⅷ) transforms to the low valence state without volatility and OsO4 in the gas state decreases. Although they can both reduce the Os being introduced into ICP-MS ultimately, the extent of their effect is not clear. OBJECTIVES To quantify the effects of absorbing liquid storage conditions such as duration, acidity and temperature on the Os signal intensity, to identify the cause of this decline and to find out the methods for its suppression. METHODS:The experiment consists of two parts:1) using the molybdenite Re-Os dating reference materials to construct a different absorbing liquid storage condition series, including duration, acidity and temperature, and measure their Os signal intensities in terms of 187Os/193Ir relative ratios. 2) sealing the residual absorbing liquid together with the spike and oxidizing agents within the Carius tube with sequent heating and distillation. The 187Os/190Os ratios were determined to calculate the Os content and the retention rate. RESULTS After storing, the Os signal intensities of absorbing liquids decline with time from 3.2% to 68.6%. The longer time, the lower acidity and the higher temperature for OsO4 absorbing liquid storage, the more obvious Os signal declines. After storing at room temperature for the same time, the Os retention rate of the low-acidity series is higher than that of the high-acidity series, but the former has a lower signal intensity than the latter. This indicates that both volatilization and reduction contribute to the decline of Os signal intensity and are the main factors. CONCLUSIONS Freezing to -18℃ can inhibit the volatilization of OsO4, whereas increasing the acidity (about 3.5 mol/L) can reduce OsO4 reduction. The combination of the two inhibits signal attenuation, and increases the flexibility and applicability of the distillation method.

Graphite has relatively high Re and Os contents and is an ideal mineral for Re-Os isotope dating. However, there are few studies on Re-Os dating of graphite. Particularly for the graphite which was formed by deformation of coal beds, the variation in Re-Os isotope system needs further study. The Lutang graphite deposit in Hunan is one of the typical cryptocrystalline graphite deposits in China. The ore-bodies are hosted in coals of the Permian Longtan Formation. In this study, the Re-Os isotopic compositions of the graphite samples from Lutang deposit and the raw coal samples from the peripheral area were analyzed by digesting sample in the Carius tube, direct distilling Os from the Carius tube, extracting Re by acetone and determining Re and Os isotopes by Negtive Thermal Ionization Mass Spectrometry. The results indicate that the Re and Os contents are 0.901-9.794 ng/g and 7.3-189.5 pg/g, respectively. The Re-Os isotope isochron age is 155.6±3.6 Ma, which is consistent with the zircon U-Pb age (153-157 Ma) of StageⅡ medium-grained biotite granite of the Qitianling pluton on the east side of the deposit. It also indicates that the coal seam of the Longtan Formation is subjected to 'baking' by the Qitianling pluton, inducing the hot contact metamorphism and changing the raw coal near the Qitianling pluton to graphite to form a graphite deposit. The comparison of Re and Os content and Os isotopic composition between the graphite, coal and Qitianlign pluton demonstrates that the Re and Os in the graphite are mainly derived from raw coal. According to the initial Os isotope ratio of 0.686±0.032, it can be concluded that minor Os with low 187Os/188Os value was absorbed by carbonaceous material during the intrusion of coal seam by the Qitianling pluton.

Volcanic rocks in the Xiemisitai Mountains, in Northwest Junggar were recently considered to form in the Silurian rather than the Devonian period. However, the characteristic and tectonic setting of Middle Silurian volcanic rocks in this area are poorly constrained. In this study, major and trace elements and Sr-Nd-Os isotopic composition analyses were synthetically conducted on the Middle Silurian basalt and basaltic andesite in northwest of the Xiemisitai Mountains, West Junggar. These volcanic samples are characterized by high MgO (5.15%-7.81%) with Mg of 56.0-60.7, low CaO (4.56%-5.09%) and FeOT/MgO (1.15-1.40), similar to those of high-Mg volcanic rocks. Basalts have εNd(t) of 2.65, (87Sr/86Sr)i of 0.70439, and (187Os/188Os)i of 0.4901. The slightly enriched isotopic signatures, high Th/Yb (2.2-2.7) and low Ba/La (17.4-33.4) indicate that they originated from depleted mantle metasomatized by melts from subducted sediments and suffered from crustal contamination. The volcanic rocks are calc-alkaline and exhibit arc-like geochemistry with the enrichment of light REE and large ion lithophile elements. It is suggested that these rocks were probably formed in a back-arc setting due to northward subduction of the Junggar Oceanic slab.

Re-Os isotope method is a powerful tool for dating ore deposits, but digesting samples with the Carius tube is complicated and dangerous.A simple and quick method to determine the age of molybdenite Re-Os and Re content has been established.5-15 mg of molybdenite samples were digested with 3 mL HNO3 in a 10 mL colorimetric cylinder.Molybdic acid in solution was removed by a centrifuge, the supernatant of the solution was then diluted to an appropriate volume.M187/M185 ratio of the resulting solution was determined directly by Inductively Coupled Plasma-Mass Spectrometry(ICP-MS).According to the principle of radioactive decay, it can be inferred that the mass ratio is positively correlated with the age.The Re-Os age of the sample can be calculated by comparing with the M187/M185 ratio of the molybdenite standard material(JDC and HLP).The Re content in the sample can be calculated on the basis of 185Re counting using the relative method.In order to test the reliability of this method, a series of molybdenite samples, whose ages vary from 13.26 Ma to 2130 Ma, were analyzed.The resulting ages were generally identical to the reference ages within 0.36%-7.42% deviations.The samples with older ages yield better results because the 187Os is more radiogenic.This method, without spike addition, can avoid the trouble of sealing and opening the Carius tube and the process of separating and purifying Re and Os, which significantly improves the experimental efficiency.This simple and quick method is highly suitable for the preliminary analysis of molybdenite Re-Os ageing.

Guangdong has abundant kinds of rare earth element resources. The resource which could satisfy the industry exploitation is only the ion adsorption type of rare earth ores. According to previous survey, Guangdong possesses heavy rare earth element resource, which is about 1/3 of total ion adsorption type ore resource. Recently, there are only three companies owning mining rights (referred to as A, B, C mine quarry, respectively). Mining quota of REO (rare earth oxides) for 2013 was only 2200 tons, while Annual ionic rare earth separation capacity was more than 10000 tons. The contradiction between supply and demand is outstanding. In order to reveal the exploitation situation of the rare-earth ores in Guangdong, we collected samples from weathering crust profiles and tailings of A, B and C mining areas. Additionally, in order to study the geochemical characteristics and their resource potential, we analyzed the rare earth elements, trace elements and associated elements by ICP-MS. Our results show that: (1) Guangdong has quite rich resource in rare earth ore, and the resource we calculated is two more orders of magnitude than previous official calculation. (2) The LREEs/HREEs ratios from three weathering crust of rare earth ore areas all ranges from 1.8 to 6.6, implying these three ores are enriched in LREEs, rather than HREEs. However, only mining the LREE ore is incompatible with market demand and the enrichment of heavy rare earth resources in Guangdong. Furthermore, there is a great gap between the rare earth mining quota and smelting separation ability. Therefore, we suggest to raise more mining right licenses and quota for mining rare earth ore properly. (3) The rare earth content of the humus layer and semi-weathered layer was not high in A and C mining areas, which is surface magnetic type metallogenic model and mineralization zone was located in weathered layer. In contrast, the rare earth content of humic layer and completely weathered layer was high (more than 0.3%) in B mining area, which is shallow type metallogenic model. (4) We need to adjust the mining area of weathering crusts according to market demand to reduce the mining leakage and recycle tailings of rare earth resources. (5) The enrichment factors of trace element content in weathering crusts and tailings are less than 10, compared with continental crust abundance, even some elements are depleted. Accordingly, we suggest it is not useful for recycling the trace elements from weathering crusts and tailings.

Abstract: Along with China′s economic development, the dissolution of heavy metals in port minerals stockyard has became important contamination sources of soil and water, which can't be ignored. The amount of heavy metal dissolution is related to the species of heavy metals. Through the static soaking test, according to the leaching of heavy metals to determine the typical mineral products and the typical heavy metal factor to study the influence of time, pH and temperature on release of heavy metals in typical products at Tianjin port stockyard. The results showed that the amounts of heavy metals released from lead ore and copper ore were the greatest. Zn, Pb and Cd in the lead ore and Ni in the copper ore were the typical heavy metal factor, and were found to be 1-3 orders of magnitude higher than other heavy metal ions. The concentration of Zn, Pb, and Cd in lead ore increased with time, and the concentration of Ni in the copper ore basically remained stable. The concentration of Zn, Pb and Cd in the lead ore and Ni in the copper ore had no significant differences with the change of pH (3.5 to 7.5). The concentration of Zn, Pb, and Cd in the lead ore increased with temperature (20-40℃). The concentration of Ni in the copper ore showed a downward trend above 30℃. This study preliminarily investigated the basic rule of dissolution of heavy metals in minerals and provides data to support and control the dissolution of heavy metals in the port stockyard.

The Kuimeishan tungsten deposit is located in the junction area of the eastern segment of the E-W-trending Nanling tectonic zone and southern segment of the NE-NNE trending Wuyishan tectonic zone. It is characterized by intergrowth of quartz vein-type wolframite and skarn-type scheelite in Dingnan county, south of Jiangxi province (Gannan). However, there is no accurate chronological evidence to confirm whether the metallogenesis occured in the Yanshanian period. The SHRIMP U-Pb age of zircons obtained from the metallogenic biotite granite is (157.7±2.7) Ma (n=11, MSWD=1.9), and the Re-Os isochron age of molybdenite from the ore-bearing quartz veins is (153.7±1.5) Ma (n=5, MSWD=0.16). The accurate metallogenic and diagenetic chronology results indicate that the Kuimeishan tungsten deposit was formed during the large-scale diagenesis and mineralization of tungsten ore in the Mesozoic period that occurred in South China. Based on the ‘five levels+basement’ prospecting model and the latest prospecting clues, it is possible that new ore bodies are amassed in the contact zone of deep rock body in Kuimeishan, which has great potential for prospecting. It is significant to the deep and periphery prospecting for tungsten as we proposed the possibility of skarn type tungsten which occurred nearby the deep and periphery part of quartz vein type tungsten in the Gannan region.

Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is suited to analyze the abundances and spatial distributions of trace elements in sulfide. However, the spread use of the technology on micro area analysis has been hampered by the different characteristics of sulfides from silicates and oxides and the lack of sulfide reference material, especially PGE-bearing reference material. In this study, a PGE-bearing sulfide (SRMD-1) is synthesized by remelted nickel sulfide fire assay button in AN evacuated quartz tube. The examination by BSE imaging revealed that the nickel button SRMD-1 was completely of monosulfide composition. Homogeneity testing by LA-ICP-MS shows that the RSDs of elements, such as S, Ni, Cr, Co, Cu, Pb, Sb, Cd, Bi, are less than 10%. The data suggest the homogeneous distribution of these elements inside SRMD-1, but elements Mn, Zn, Sn, Tl are not as homogeneous with relatively larger RSDs. Elements Ag, Au and Pt are homogeneous inside SRMD-1, but RSDs of other noble metal elements are relatively larger according to low element content, instrument fluctuations or mass spectrometry interference. The homogeneity of the nickel button will be improved by increasing the content for the noble metal elements and lowering the quenching temperature for the molten samples. During the analysis of the nickel sulfide fire assay button, the spectral interferences in light PGEs (Ru, Rh and Pd) by argides is serious, and must be corrected, while the interferences to Os, Ir, Pt and Au can be ignored. Compared to the button which is not remelted, the homogeneity of the elements improved significantly. According to the work documented here, it is possible to synthesized PGE-bearing sulfide reference material for LA-ICP-MS by remelted nickel sulfide fire assay button.

In the recent decade, a series of new progress on geological exploration work have been achieved in China. There have new people-oriented trends in modern mineral geological work. The present geological work related to mineral resources is very different from the previous status. For example, local geological party becomes a national-wide and world-wide geological party, special kind of mineral resources extends to all kinds of mineral resources, and special profession of geology develops to no profession. The new trend of growing two markets (national market and international market) has been formed in utilizing two resources (domestic resources and foreign resources). It requires that the close relationship should be established for geological exploration and rock & mineral analysis. On the one hand, it is urgent that geologists should further understand the features of modern testing technology, and fully utilize the instruments and equipments. On the other hand, the laboratory also need to provide the technological support for the geological exploration, develop the new analytical methods, new techniques, new equipments, to meet the requirement of on-site analysis, quick speed analysis, low cost analysis, easy-operation analysis, full and comprehensive analysis, and rather than only receive samples and export simply analytical data. At the same time, the management department should give an important role for the combining geological exploration with geoanalysis in the whole process of making policy and planning project.

In Re-Os isotope chronology, the acetone extraction process is quicker and easier compared to the anion exchange method. The Re solution which was separated and purified by acetone extraction is suitable for the measurement by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), but unsuitable for Negative Thermal Ionization Mass Spectrometry (N-TIMS) directly because of high salt contents. An improvement was made to the acetone extraction method to separate and purify Re for N-TIMS determination by increasing the alkalinity concentration from 5 mol/L to 10 mol/L. Compared with the anion exchange method, the acetone extraction process is not only easier to operate with lower blank (Re 3-7 pg), but also saves time. The signal intensity of Re was over 100 mV per 1 ng Re, which met the requirements of a high-accuracy instrument measurement completely. The national first grade standard material of JDC (GBW 04436) and the laboratory reference material of JCBY were measured to verify the improved method. The Re contents of JDC and JCBY obtained from this method were (17.17±0.50) μg/g and (38.34±0.44) ng/g, respectively, which were consistent with the certified value of JDC (17.39±0.32) μg/g and the certified value of JCBY (38.61±0.86) ng/g. The improved procedure was applied to practical samples with good long-term results.

Scholars at home and abroad in recent years have focused on researching ammonia nitrogen pollution migration rules in the vadose zone soil. Column simulation and software simulation were primarily conducted for the study of ammonia nitrogen pollution migration. Biotechnology was widely used in degradation of pollutant in soil, but less applied to the study of pollution migration. This study applied Denaturing Gradient Gel Electrophoresis (DGGE) and the sequence analysis of the V3 Region of 16S rRNA combined with canonical correspondence analysis to characterize the bacteria vertical distribution characteristics and bacterial community structure in the soil from three typical contaminated zones in the North China Plain. According to the analysis of physical and chemical soil properties in polluted areas, there were some dominant individual bacteria in the key pathways of the nitrogen cycle and sulfate metabolism. It is suggested that the bacterial communities are affected by the distributions of ammonia, nitrate and nitrite nitrogen, showing that the community structure information of the dominant population in contaminated soil is an important parameter to study the ammonia nitrogen pollution migration rules.

Traditionally, the percentage sum method is used to check the data quality of total analysis of constituents for silicate rock. For samples with a high content of trace elements, the contents of major elements obtained by X-ray Fluorescence Spectrometry (XRF) will deviate from the true values, regardless of trace elements, as will its corresponding matrix effect to the major element. The method described in this paper improves the accuracy of major element content in silicate samples with a high content of Sr and Ba， through extending the calibration curve′s quantitative range of Sr and Ba by Chinese National Standard Materials and artificial standard materials, and applying a matrix correction coefficient of Sr and Ba to the major element calibration procedure. The validity of the method was substantiated by analyzing the national standard materials; the relative standard deviations (RSD) of major elements were less than 2%. Additionally, analysis results of major elements of national standard materials and artificial standard materials, which do not participate in regression were basically in accordance with reference contents. The method can be used to satisfy the analysis of silicate rock and the sum results of all major elements meet the standard of specification of testing quality management for geological laboratories (99.3% to 100.7%).

The accuracy and precision are lower, and the detection limit is higher for the determination of F with low content and low fluorescence yield by using X-ray Fluorescence Spectrometry combined with lower dilution ratio fused bead samples preparation. In this paper a method has been reported for the determination of 12 major, minor and trace elements in phosphate ores by wavelength dispersive X-ray Fluorescence Spectrometry. A lower-dilution ratio (5∶1 reagent to sample) fused bead sample preparation mix was used for measurements. Chinese National Standard Materials with similar matrix elemental compositions to the samples were used to calibrate the matrix effect with the experience coefficient method. Results show that precision and accuracy of the method are greatly improved for 12 components, with lower detection limits and satisfactory results for unknown samples. Especially, precision, accuracy and detection limit of F were better than the analytical results in literature and were obtained by using a 10∶1 fused dilution ratio. Meanwhile, this method solved the technological problem by determining the F component using a pressed pellet sample, and other major and minor components by using fused bead pellet samples. The detection limit of F was also lowered by using this method.