Search Results (34)

The Shuixie Cu–Co polymetallic orefield, located in western Yunnan Province (southeastern margin of the Qinghai–Tibet Plateau), is renowned for its Cu–Co mineralization. A recent resource reassessment identified Sb–Au and Cu–Co–Bi (Sb–Au) orebodies as genetically associated with primary Cu–Co mineralization. The mineralization characteristics and microscopic observations indicate that gold mineralization in the Sb–Au orebodies follow a pulsating fluid injection model. The model includes four pulses: (1) euhedral gold-poor pyrite (PyI₁) precipitation; (2) margin-parallel growth of gold-rich pyrite (PyI₂) on PyI₁; (3) continued growth of gold-rich pyrite (PyI₃) along PyI₂; and (4) outermost concentric gold-rich pyrite (PyI₄) formation. This study examined gold-bearing pyrite in orebodies and host rocks. In situ laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) analysis of pyrite and inductively coupled plasma mass spectrometry (ICP–MS) whole-rock trace element analysis were conducted to track the ore-forming fluid evolution. Compared with CI chondrite, pyrites from all pulses were enriched in LREEs over HREEs. The pyrite REE distribution curves exhibited right-skewed patterns, reflecting LREE enrichment. The Hf/Sm, Nb/La, and Th/La ratios were generally below 1, indicating high-field-strength element depletion. These results suggest a Cl-rich, F-poor ore-forming fluid. The pyrite trace elements showed enrichment in the chalcophile elements (e.g., Cu and Pb) and exceptionally high Bi levels compared with the continental crust. The chalcophile elements (e.g., Zn and Cd) were depleted, whereas iron-group elements (e.g., Co) were enriched and Ni was depleted. The pyrite δCe values (0.87–1.28, mean = 1.01) showed weak anomalies, indicating a reducing ore-forming environment. The δEu values of pyrite during pulses 1 to 4 ranged widely, from 0.2–3.01 (mean of 1.17), 0.27–1.39 (0.6), and 0.41–1.40 (0.96) to 0.4–1.36 (0.84), respectively, suggesting an initial temperature decline and subsequent increase in the ore-forming fluid. Significant variations were found in the Y/Ho, Zr/Hf, and Nb/Ta ratios across pulses, indicating the potential involvement of high-temperature hydrothermal fluids or late-stage alteration during ore formation. The Y/Ho ratio of pyrite overlapped most closely with that of the continental crust of China, indicating a close relationship between the ore-forming fluids and the crust. Full article

High-purity quartz is considered one of the world’s scarce mineral resources. During the evaluation process of high-purity quartz raw material deposits, metallurgical purification evaluation experiments are often required to assess the quality of quartz. However, these experiments are costly and time-consuming, and have other drawbacks. In addition, high-purity quartz is difficult to analyze by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) due to its extremely low impurity content, resulting in low accuracy. It is therefore essential to assess the validity of the results obtained from LA-ICP-MS analysis of quartz minerals and to establish an efficient and cost-effective method for the evaluation of high-purity quartz deposits. We selected samples from the high-purity quartz deposits at Yamansu and Taerlang in Xinjiang, which exhibit uniform cathodoluminescence (CL) characteristics. We conducted trace element analysis of quartz using four methods: nanosecond laser dot ablation, femtosecond laser dot ablation, femtosecond laser line ablation, and femtosecond laser area scanning. Combined with the results of metallurgical purification, the stability of quartz LA-ICP-MS analytical data and the proximity to the purification results are evaluated by using two methods, i.e., the comparison of casting diagrams and the construction of comprehensive stability and proximity evaluation models. The results show that the femtosecond laser line ablation has the best stability in the analysis of the elements of quartz Al, Ti, Li, and B and the highest proximity to the results of metallurgical purification, and the nanosecond laser dot ablation also has better stability and proximity, while femtosecond laser surface scanning data quality is relatively poor due to unavoidable inclusions and co-associated minerals. Geological mapping using in situ quartz trace element content can effectively delineate the potential areas of high-purity quartz, and the results of analysis and the metallurgical purification results have a high degree of proximity. Therefore, this paper recommends the use of femtosecond laser line ablation as a highly efficient exploration method for high-purity quartz deposits. Full article

The Jiepailing deposit in southern Hunan is a typical large to super-large polymetallic tin deposit enriched in beryllium and other rare metals. To enhance the understanding of the mineralization processes of the Jiepailing deposit, detailed mineralogical, in situ geochemical, and sulfur isotopic analyses were conducted on pyrite closely associated with tin–polymetallic mineralization. Five types of pyrite have been identified in the deposit: (1) euhedral to subhedral medium- to coarse-grained pyrite (PyI) in tungsten–tin ore; anhedral fine-grained pyrite (PyII) in tin polymetallic–fluorite ore; anhedral fine-grained or aggregate pyrite (PyIII) in lead–zinc ore; euhedral to subhedral coarse-grained pyrite (PyIV) in beryllium–fluorite mineralization; and subhedral to anhedral fine-grained pyrite (PyV) in carbonate veinlets developed in the wall rock. Backscattered electron imaging indicates consistent structural features across the five types of pyrite. In situ trace element analysis reveals differences in trace element concentrations among the pyrite types. PyI is relatively enriched in Sn, Cu, and Co. In contrast, PyIII is enriched in Pb, Zn, Sn, and Ti, while PyIV and PyV are enriched in Ag and Sb. PyI has a Co/Ni ratio more than 1, while the Co/Ni ratios in the other four types of pyrite are less than 1. LA-MC-ICP-MS in situ sulfur isotope analysis shows δ³⁴S values ranging from 2.5‰ to 5.8‰ (average 4.3‰, PyI), 2.5‰ to 5.8‰ (average 4.3‰, PyII), −7.6‰ to 9.5‰ (average 3.9‰, PyIII), −3.7‰ to 10.6‰ (average 3.6‰, PyIV), and 6.8‰ to 14.1‰ (average 9.2‰, PyV). Based on previous studies, regional geological background, deposit characteristics, and the in situ trace element and sulfur isotope compositions of pyrite, it is inferred that the various ore bodies in the Jiepailing deposit are products of Late Cretaceous magmatic–hydrothermal activity. The early ore-forming fluid originated from magmatic sources and during the migration into the wall rock and shallow formations, mixed with fluids primarily derived from atmospheric precipitation. Temperature, pressure, and composition changed of the ore-forming fluid which carried a large amount of substances, leading to tungsten–tin, tin polymetallic–fluorite, lead–zinc, and beryllium–fluorite mineralization, followed by carbonation during the late-stage mineralization. Full article

The sulfide Pb–Zn deposits in the Aksai Chin region of Xinjiang have long been subject to debate regarding their genetic classification due to the unclear origin of the ore-forming components. This study focuses on the Sachakou Pb–Zn deposit, the most representative deposit in the region, and integrates field investigations, petrographic observations, in situ LA-ICP-MS trace element analysis, and in situ S–Pb isotope analysis. The deposit is hosted within the siliceous rock and silicified limestone of the Lower Jurassic Bagongbulansha Formation, with ore bodies controlled by structural and stratigraphic factors. Three mineralization stages have been identified in the Sachakou deposit: a red–brown sphalerite mineralization stage (S1), a light-brown sphalerite stage (S2), and a galena mineralization stage (S3). The trace elements in sphalerite indicate that the mineralization process is unrelated to magmatic activity. The mineralization temperature, determined using a GGIMFis geothermometer, ranges from 294 °C to 121 °C. The δ³⁴S_V-CDT values of sulfides range from −4.93‰ to 1.24‰, suggesting that the Jurassic gypsum layer served as the sulfur source. The lead isotope ratios of ²⁰⁶Pb/²⁰⁴Pb range from 18.308 to 18.395, of ²⁰⁷Pb/²⁰⁴Pb—from 15.669 to 15.731, and of ²⁰⁸Pb/²⁰⁴Pb—from 38.595 to 38.776, indicating that the ore-forming metals were predominantly sourced from the upper crust. Based on geological and geochemical characteristics, the Sachakou Pb–Zn deposit is classified as a sedimentary-hosted epizonogenic hydrothermal deposit. Full article

The newly discovered Erdaodianzi gold deposit in southern Jilin Province, Northeast China, is located in the eastern segment of the northern margin of the North China Craton (NCC). It is a large-scale gold deposit with reserves of 38.4 tons of gold. Gold mineralization in the ore district primarily occurs in gold-bearing quartz–sulfide veins. The gold ore occurs mainly as vein, veinlet, crumby, and disseminated structures. The hydrothermal process can be divided into three stages: stage I, characterized by quartz, arsenopyrite, and pyrite; stage II, featuring quartz, arsenopyrite, pyrite, pyrrhotite, chalcopyrite, sphalerite, and native gold; and stage III, consisting of quartz, pyrite, sphalerite, galena, electrum (a naturally occurring Au–Ag alloy), and calcite. Electrum and native gold primarily occur within the fissures of the polymetallic sulfides. To determine the enrichment mechanism of the Au element and the genetic types of ore deposits in the Erdaodianzi deposit, sourcing in situ trace element data, element mapping and sulfur isotope analysis were carried out on sphalerites from different stages using LA-ICP-MS. Minor invisible gold, in the form of Au–Ag alloy inclusions, is present within sphalerites, as revealed by time-resolved depth profiles. The LA-ICP-MS trace element data and mapping results indicate that trivalent or quadrivalent cations, such as Sb³⁺ and Te⁴⁺, exhibit a strong correlation with Au. This correlation can be explained by a coupled substitution mechanism, where these cations (Sb³⁺ and Te⁴⁺) replace zinc ions within the mineral structure, resulting in a strong association with Au. Similarly, the element Pb exhibits a close relationship with Au, which can be attributed to the incorporation of tetravalent cations like Te⁴⁺ into the mineral structure. The positive correlation between Hg and Au can be attributed to the formation of vacancies and defects within sphalerite, caused by the aforementioned coupled substitution mechanism. A slight positive relationship between Au and other divalent cations, including Fe²⁺, Mn²⁺, and Cd²⁺, may result from these cations simply replacing Zn within the sphalerite lattice. The crystallization temperatures of the sphalerite, calculated via the Fe/Zn ratio, range from 238 °C to 320 °C. The δ³⁴S values are divided into two intervals: one ranging from −1.99 to −1.12‰ and the other varying from 10.96 to 11.48‰. The sulfur isotopic analysis revealed that the ore-forming materials originated from magmatic rock, with some incorporation of metamorphic rock. Comparative studies of the Erdaodianzi gold deposit and other gold deposits in the Jiapigou–Haigou gold belt have confirmed that they are all mesothermal magmatic–hydrothermal lode gold deposits formed at the subduction of the Paleo-Pacific Plate beneath the Eurasian Plate during the Middle Jurassic. The Jiapigou–Haigou gold belt extends northwest to the Huadian area of Jilin province. This suggests potential for research on gold mineralization in the northwest of the belt and indicates a new direction for further gold prospecting in the region. Full article

The Xiong’ershan district is situated on the southern margin of the North China Craton (NCC) and located within the Qinling–Dabieshan Orogen’s orogenic zone. It is adjacent to the XiaoQinling mining district and exhibits very favorable geological conditions for mineralization, as the district contains numerous gold deposits, positioning it as one of the key gold-producing areas of China. The Miaoling gold deposit is a hydrothermal deposit and is controlled by the Mesozoic nearly NS-trending fault. The ore bodies are hosted in the Mesoproterozoic Xiong’er Group of the Changcheng System of volcanic rocks, with reserves reaching large-scale levels. Pyrite is the main gold-bearing mineral and can be classified into four generations: early-stage fine- to medium-grained euhedral to subhedral cubic pyrite (Py1); medium- to coarse-grained euhedral to subhedral cubic granular pyrite in quartz veins (Py2a); fine-grained subhedral to anhedral disseminated pyrite in altered rocks (Py2b); and late-stage anhedral granular and fine-veinlet pyrite in later quartz veins (Py3). Through in situ trace element analysis of the pyrite using LA-ICP-MS, a positive correlation between Au and As was observed during the main mineralization stage; gold mainly exists as a solid solution within the pyrite lattice, and the ablation signal curve reflecting the intensity of trace element signals showed that gold also occurs as micron-scale mineral inclusions. The trace element content suggested a gradual increase in oxygen fugacity from Stage 1 to Stage 2, followed by a decrease from Stage 2 to Stage 3. The Co/Ni values in the pyrite (0.56 to 62.02, with an average of 12.34) exhibited characteristics of magmatic hydrothermal pyrite. The in situ sulfur isotope analysis of the pyrite using LA-MC-ICP-MS showed δ³⁴S values of 4.24‰ for Stage 1, −6.63‰ to −13.79‰ for Stage 2, and −4.31‰ to −5.15‰ for Stage 3. Considering sulfur isotope fractionation, the δ³⁴S value of the hydrothermal fluid during the main mineralization stage was calculated to be between 0.31‰ and 2.68‰. Full article

The Xinjiazui gold deposit marks a notable significance in prospecting within the Back-Longmenshan tectonic belt, located on the northwest margin of the Yangtze Block, China. Despite the extensive studies conducted on this deposit, the source of the ore-forming materials remains unclear, leading to ongoing debates regarding the genesis of this deposit. This study analyzed in situ (EPMA and LA-ICP-MS) trace elements and S-Pb isotopes of arsenopyrite, solely from the principal metallogenic stage and paragenetic with native gold. The results show that the gold in arsenopyrite occurs as invisible gold (Au³⁺), with an average concentration of 9.38 ppm, whereas the concentrations of magma-related elements, such as W, Sn, Mo, and Bi, are very low. The sulfur isotopes (³⁴S) of arsenopyrite range from 8.32‰ to 10.16‰, aligning closely with the deep metamorphic basement (Pt₃l). Meanwhile, the lead isotopes in arsenopyrite display characteristics typical of those found in orogenic belts. A comprehensive analysis of the abundance of gold indicated that the metallogenic materials (sulfur and gold) primarily originated from Pt₃l. Additionally, the arsenopyrite thermobarometer indicated that the Xinjiazui gold deposit formed in a medium–low-temperature, medium metallogenic environment (5.57–8.69 km), with a sulfur fugacity (log f (S₂)) below −8.4. Combined with previous research results, this study proposes that the Xinjiazui gold deposit is a subduction-related mesozonal orogenic gold deposit. In gold prospecting and exploration in the Back-Longmenshan tectonic belt, it is essential to focus on the distribution of brittle-ductile shear zones and location of the quartz veins associated with pyrite and arsenopyrite mineralization. Full article

The Bou Dahar Pb-Zn district, located in the Moroccan High Atlas, is a typical carbonate-hosted Pb-Zn ore district (>30 Mt at 4 wt.% Pb, 4 wt.% Zn). In situ trace element analysis was performed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) on galena and cerussite from different ore types. The galena is generally enriched in Ag and Sb, secondarily enriched in Cu, with a trace amount of Cd and As, but extremely depleted in Bi and Tl. The main substitution mechanism in galena is (Ag, Cu)⁺ + Sb³⁺ ↔ 2Pb²⁺, and at high Sb concentrations, the further substitution of 2Sb³⁺ + □ ↔ 3Pb²⁺ (where □ represents a vacancy) took place. Micro-inclusions of Cu-Sb-bearing minerals (such as tetrahedrite) and Ag-bearing minerals (such as acanthite) may exist in some situations. The features of trace elements in galena show the existence of different coupled substitutions in vein-related ore, breccia-related ore, and strata-bound ore. This suggests that the Bou Dahar district experienced multistage mineralization. The MVT model alone cannot fully explain the ore-forming process. The cerussite replacing strata-bound galena is enriched in Sr, Ba, Ag, and Cu, with minor Sb, As, and Tl. Strontium and Ba are directly substituted with Pb in the cerussite lattice. Copper and Ag are likely present in cerussite as nano-inclusions, which differs from the coupled substitution mechanism of the original galena. High concentrations of Ag may occur due to minor electrum inclusions. The enrichment of Ag, Cu, and Au in cerussite during the oxidation process may guide the optimization of ore processing, especially in extracting valuable trace/minor elements. Full article

The gold deposit offshore of Northern Sanshandao is an ultra-large-scale gold deposit discovered in the Jiaodong ore area in recent years. This deposit is a fractured-zone altered-rock-type gold deposit; however, its ore genesis and precise mineralization processes are still highly controversial. Based on petrographical observation, the trace elements, sulfur isotopes, and rubidium–strontium isotopes of the gold-bearing pyrite were analyzed using LA-MC-ICP-MS to obtain the source of the ore-forming fluids and ore genesis. The results show that Au has a good positive correlation with Ag, As, and Cu. It is speculated that the As in the pyrite of the gold deposit offshore of Northern Sanshandao is in the form of As⁻, replacing S⁻ and entering the pyrite, causing its lattice defects, and thus promoting the entry of Au⁺ into the gold-bearing pyrite. The Co/Ni ratios mainly range between 0.1 and 10, indicating that the mineralization process has experienced different forms of hydrothermal evolution and the mixing of different fluids. The results of the in-situ sulfur isotope analysis show that pyrite δ³⁴S in the mineralization period is characterized by a high sulfur value. The authors of this study believe that the initial sulfur isotope composition has mantle-derived components. The large-scale, deep cutting, and high degree of fragmentation in the Sanshandao fault zone are conducive to the interaction between fluids and rocks, as well as the mixing and addition of seawater, resulting in the characteristic high δ³⁴S value. The Sr isotopic compositions indicate a crust–mantle mixing attribute of the mineralized material source. The Rb–Sr isochron age of the pyrite is 118.5 ± 0.65 Ma, which represents the age of gold mineralization. According to the characteristics of the trace elements and sulfur isotopes, it is inferred that the gold deposit minerals offshore of Northern Sanshandao originated from deep magmatic-hydrothermal reservoirs, and the mixing of seawater and Au–As-rich hydrothermal fluids was the formation mechanism of huge amounts of gold precipitation. Full article

A series of Mo-polymetallic deposits have been developed in the Jiaodong Peninsula. Notably, these Mo-dominant deposits formed essentially during the same period as the well-known world-class Au deposits in this area, hinting at a potentially unique geological correlation between them. Therefore, conducting thorough research on Mo deposits in Jiaodong holds significant importance in exploring the area’s controlling factors of Mesozoic metal endowments. To reveal the petrogenesis and metallogenic potentials of Mo-fertile and ore-barren granitoid, apatite grains from the Late Aptian Nansu granodiorite and Aishan monzogranite are investigated in this study. Detailed petrographical observations, combined with in situ analysis of electron probe micro-analyzer (EPMA) and Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), have been conducted on apatite grains from the Nansu and Aishan plutons. This comprehensive analysis, encompassing both major and trace elements as well as isotopic characteristics of apatite, aims to elucidate the metallogenic differences within the late Early Cretaceous granitoids of Jiaodong. The results reveal that the apatite grains across all samples belong to fluorapatites, suggesting their magmatic origin. Additionally, chondrite-normalized rare earth element (REE) patterns of apatites in ore-fertile and ore-barren granitoids exhibit a “right-leaning” trend, characterized by relative enrichments in light REEs and depletions in heavy REEs. Both the Nansu and Aishan plutons exhibit moderately negative Eu anomalies (with averages δEu values of 0.44 and 0.51, respectively), along with slightly positive Ce anomalies (averaging δCe values of 1.08 and 1.11, respectively). A negative correlation is observed between their δEu and δCe values, indicating that the parental magmas of ore-fertile and ore-barren granitoids were formed in a relatively oxidizing environment. The calculated apatite OH contents for the Nansu pluton range from 0.26 to 1.38, while those for the Aishan pluton vary between 0.24 and 1.51, indicating comparable melt H₂O abundances. Consequently, the results suggest that neither the oxygen fugacities nor the water contents of the parental magma can account for the metallogenic differences between Nansu and Aishan plutons. The apatite in the Nansu pluton exhibits a higher Ce/Pb ratio and a relatively lower Th/U ratio, indicating the involvement of a greater volume of fluids in the magmatic evolution process of this ore-bearing granitoid. Apatite grains sourced from the Nansu and Aishan plutons exhibit ε_Nd(t) values ranging from −16.63 to −17.61 (t = 115.7 Ma) and −17.86 to −20.86 (t = 116.8 Ma), respectively. These results suggest that their parental magmas primarily originated from the partial melting of Precambrian metamorphic basement rocks within the North China Craton, with a minor contribution from mantle-derived materials. Additionally, the presence of mafic microgranular enclaves in both the Nansu and Aishan plutons indicates that both have undergone magma mixing processes. The binary diagrams plotting the ratios of Ba/Th, Sr/Th, and U/Th against La/Sm demonstrate that apatite grains of ore-fertile granitoid exhibit a distinct trend towards sediment melting. This suggests the potential incorporation of sedimentary materials, particularly those rich in molybdenum, into the magmatic source of the Nansu pluton, ultimately leading to the occurrence of molybdenum mineralization. Full article

The Jiaodong gold province is one of the most important gold fields globally and the largest in China. The Denggezhuang gold deposit is situated in the eastern portion of the Muping metallogenic belt, within the Jiaodong gold province. Despite many recent investigations, detailed mineralogical studies, particularly on auriferous minerals such as pyrite, are lacking. Therefore, further constraints on the occurrence mode and source of gold are necessary for this deposit. This study employed in situ laser ablation (multi-collector) inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) trace element and sulfur-lead isotopic analyses on pyrite at different stages. The aim was to reveal the occurrence status of various trace elements within Denggezhuang pyrite and to trace the complete evolution process of multi-stage fluids at Denggezhuang, elucidating the sources of gold mineralization. Four generations of pyrite in chronological order, Py-1, Py-2a, Py-2b, and Py-3, were identified via petrographic and backscattered electron (BSE) image analyses. Using in situ LA-MC-ICP-MS, we found that Co and Ni are most abundant in Py-1, while Py-2b is rich in As, Au, Ag, Pb, and Zn, reflecting the evolution of the mineralizing fluids in different mineralization stages. Py-2b contains a significant amount of invisible lattice gold, which migrates and precipitates within fluids rich in As. The in situ LA-MC-ICP-MS S-Pb isotopic analysis of pyrite indicates a relatively consistent source of ore-forming materials across different stages. Additionally, the S-Pb isotope characteristics resemble those of widely distributed coeval mafic dikes. Therefore, we propose that a water-rich, fertile, and deep-seated mafic magmatic system might have provided fluids, materials, and heat for mineralization. Full article

In this work, a reliable and robust in situ non-matrix-matched calibration method is proposed for element composition determination in scheelite samples. With external calibration against the silicate glass standard reference material NIST SRM 610, the concentrations of both major elements (Ca and W) and trace elements (Si, Fe, Mo, Y, rare earth elements, etc.) in scheelite are determined using an ArF 193 nm excimer nanosecond laser ablation-inductively coupled plasma mass spectrometer (LA-ICP-MS). Here, the ablation was performed by hole drilling under a helium (He) environment using a laser spot size of 35 μm and a laser repetition of 5 Hz, and the aerosols were then transported to a quadrupole ICP-MS by a mixture of He and make-up gas argon (Ar) with a total gas flow rate of 1.6 L/min. Results showed that there was no apparent matrix effect between the NIST SRM 610 and scheelite by this proposed method. With internal standardization against W, the obtained concentrations of CaO and WO₃ were found to yield an average matrix CaO/WO₃ mass fraction ratio of 0.245 (2σ = 0.003, n = 19), which agreed well with the value of 0.243 (2σ = 0.002, n = 15) from electron probe microanalysis (EPMA). Furthermore, the accuracy of trace element analyses with this proposed non-matrix-matched calibration in situ method was evaluated by comparing the concentration results with those from bulk analysis by solution nebulizer ICP-MS (SN-ICP-MS). It was found that the quantification results from LA-ICP-MS and SN-ICP-MS were comparable, in particular showing a relative concentration bias of the total ∑REE+Y contents of less than 2%. This confirmed that scheelites can be accurately analyzed in situ by LA-ICP-MS without matrix-matched calibration standards. By using this developed in situ method, the element compositions in a series of scheelite samples from different W-associated deposits in China were successfully quantified, promising further genetic process investigation and associated geologic activities of the polymetallic resources. Full article

In the process of in situ zircon U–Pb dating, it is an effective means to overcome the matrix effect by using a matrix-matched external reference material. However, the limited number of available zircon reference materials still makes it difficult to meet the research needs. In this paper, we performed a preliminary analysis of the gemological characteristics, trace elements and U–Pb ages of natural zircon CAM18 to assess its suitability as a reference material for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb dating. This tawny, gem-quality zircon has no visible inclusions and weighs approximately 0.55 g. Its density, full width at half maximum (FWHM) of the Raman peak and alpha flux (Dα) indicate that the sample has suffered mild-to-moderate radiation damage without any thermal treatment. The LA-ICP-MS U–Pb dating results reveal that the trace elements content and U–Pb ages of the sample are fairly homogeneous at the 50 μm scale, and there is no obvious loss of radiogenic Pb. The ²⁰⁶Pb/²³⁸U age (571.0 ± 3.0 Ma, 2s) and ²⁰⁷Pb/²³⁵U age (573.4 ± 6.0 Ma, 2s) are consistent within the analytical uncertainty, and the calculated concordia age is 571.4 ± 1.4 Ma (2s, n = 20). The variation in the ²⁰⁶Pb/²³⁸U ages is small, with a measurement repeatability of 0.46% (RSD), which is within the uncertainty of the age accuracy obtained by LA-ICP-MS. The oscillatory zoning, Th/U ratio (0.2) and chondrite-normalized rare-earth element (REE) pattern imply a magmatic origin of zircon CAM18. The Ti-in-zircon temperature ranges from 714 to 742 °C, and the oxygen fugacity ranges from ΔFMQ−2.87 to ΔFMQ−3.17, suggesting that it is crystallized in a reducing environment. All the results show that zircon CAM18 may has great potential in LA-ICP-MS U–Pb dating. Full article

Greyish-purple tremolite jade has become well known in the past few years, and the origin of its color has attracted the attention of gemologists. In this study, FT-IR spectra, EPMA, EPR spectra, micro-XRF, UV–Vis–NIR spectra, and LA-ICP-MS in situ mapping were analyzed to investigate the chromophore elements. The study sample was chosen from the Sanchahe mine, Qinghai Province, NW China, which has the typical characteristics of a gradual color change. The FT-IR and EPMA results revealed that the mineral composition of the dark and light greyish-purple regions of the sample are primarily composed of tremolite. UV–Vis–NIR spectra demonstrated that the greyish-purple color is mainly due to strong absorptions at 560 nm and 700 nm and weak absorption at 745 nm in the visible range. The EPR spectra presented ~3400 G six hyperfine lines resulting from the hyperfine interactions of the unpaired electron with the Mn²⁺ nucleus in the octahedral site. The UV–Vis–NIR and EPR spectra analyses demonstrated that Mn²⁺ is the origin of the purple color. A comparison of the major elements in the light and dark regions indicated that the chromogenic elements have strong positive correlations with Mn, Cu, and Fe. LA-ICP-MS mapping used to analyze the first transition metals indicated possible positive correlations between the greyish-purple color and the trace chromogenic elements. This suggested that the Mn, Cu, and Fe contents are significantly high in the dark band region. Combining in situ LA-ICP-MS mapping of trace elements, UV–Vis spectra, and EPR analysis results, it was suggested that Mn, Cu, and Fe are the major contributors to the greyish-purple color. This study provides a reference for the specific experimental methods to determine chromophores and the origin of color in tremolite jades. Full article

The use of analytical techniques is important and critical in all areas related to REE, such as basic fundamental research, exploration, mining, extraction, and metallurgical activities at different stages by different industries. At every stage of these activities, rock, ore, minerals, and other related materials have to be analyzed for their REE contents in terms of elemental, isotopic, and mineralogical concentrations using different analytical techniques. Spectacular developments have taken place in the area of analytical instrumentation during the last four decades, with some of them having shrunk in size and become handheld. Among laboratory-based techniques, F-AAS, GF-AAS, ICP-OES, and MP-AES have become very popular. Because of high sensitivity, fewer interference effects, and ease of use, ICP-MS techniques, such as quadrupole ICP-MS, ICP-MS/MS, ICP-TOF-MS, MH-ICP-MS, HR-ICP-MS, and MC-ICP-MS, with both solution nebulization as well as direct solid analysis using laser ablation sample introduction methods, have become more popular for REE analysis. For direct analysis of solids, INAA, XRF, and LIBS techniques, as well as LA-based ICP-MS techniques, are being extensively utilized. The LIBS technique in particular requires little to no sample preparation. TIMS, SIMS, and SHRIMP techniques are being used for isotopic as well as dating REE depots. Portable analytical techniques, such as pXRF, pLIBS, and Raman spectrometers are able to perform in situ analysis even in the field, helping to make fast decisions during exploration studies. At present, hyperspectral remote sensing techniques including handheld, drone, and satellite-based techniques have become very popular in REE exploration studies because of their ability to cover larger areas in a limited time and, thus, became very cost-effective. Deployment of microanalytical devices/sensors mounted in remotely operated vehicles (ROV) is being successfully utilized in detecting REE-rich deposits in the deep oceans. Providing updated in-depth information on all these important aspects with suitable examples, especially from the point of view of REE research studies is the focal point of this review article. Full article