Skarn deposits of China

Skarn deposits are one of the most common deposit types in China. The 386 skarns summarized in this review contain ~8.9 million tonnes (Mt) Sn (87% of China’s Sn resources), 6.6 Mt W (71%), 42 Mt Cu (32%), 81 Mt Zn-Pb (25%), 5.4 Mt Mo (17%), 1,871 tonnes (t) Au (11%), 42,212 t Ag (10%), and ~8,500 Mt Fe ore (~9%; major source of high-grade Fe ore). Some of the largest Sn, W, Mo, and Zn-Pb skarns are world-class. The abundance of skarns in China is related to a unique tectonic evolution that resulted in extensive hydrous magmas and widespread belts of carbonate country rocks. The landmass of China is composed of multiple blocks, some with Archean basements, and oceanic terranes that have amalgamated and rifted apart several times. Subduction and collisional events generated abundant hydrous fertile magmas. The events include subduction along the Rodinian margins, closures of the Proto-Tethys, Paleo-Asian, Paleo-Tethys, and Neo-Tethys Oceans, and subduction of the Paleo-Pacific plate. Extensive carbonate platforms developed on the passive margins of the cratonic blocks during multiple periods from Neoarchean to Holocene also facilitated skarn formation. There are 231 Ca skarns replacing limestone, 15 Ca skarns replacing igneous rocks, siliciclastic sedimentary rocks, or metamorphic silicate rocks, 113 Ca-Mg skarns replacing dolomitic limestone or interlayered dolomite and limestone, and 28 Mg skarns replacing dolomite in China. The Ca and Ca-Mg skarns host all types of metals, as do Mg skarns, except for major Cu and W mineralization. Boron mineralization only occurs in Mg skarns. The skarns typically include a high-temperature prograde stage, iron oxide-rich higher-temperature retrograde stage, sulfide-rich lower-temperature retrograde stage, and a latest barren carbonate stage. The zoning of garnet/pyroxene ratios depends on the redox state of both the causative magma and the wall rocks. In an oxidized magma-reduced wall-rock skarn system, such as is typical of Cu skarns in China, the garnet/pyroxene ratio decreases, and garnet color becomes lighter away from the intrusion. In a reduced intrusion-reduced wall-rock skarn system, such as a cassiterite- and sulfide-rich Sn skarn, the skarn is dominated by pyroxene with minor to no garnet. Manganese-rich skarn minerals may be abundant in distal skarns. Metal associations and endowment are largely controlled by the magma redox state and degree of fractionation and, in general, can be grouped into four categories. Within each category there is spatial zonation. The first category of deposits is associated with reduced and highly fractionated magma. They comprise (1) greisen with Sn ± W in intrusions, grading outward to (2) Sn ± Cu ± Fe at the contact zone, and farther out to (3) Sn (distal) and Zn-Pb (more distal) in veins, mantos, and chimneys. The second category is associated with oxidized and poorly to moderately fractionated magma. Ores include minor porphyry-style Mo and/or porphyry-style Cu mineralization ± Cu skarns replacing xenoliths or roof pendants inside intrusions, zoned outward to major zones of Cu and/or Fe ± Au ± Mo mineralization at the contact with and in adjacent country rocks, and farther out to local Cu (distal) + Zn-Pb (more distal) in veins, mantos, and chimneys. Oxidized and highly fractionated magma is associated with porphyry Mo or greisen W inside an intrusion, outward to Mo and/or W ± Fe ± Cu skarns at the contact zone, and farther to Mo or W ± Cu in distal veins, mantos, and chimneys. The final category is associated with reduced and poorly to moderately fractionated magma. No major skarns of this type have been recognized in China, but outside China there are many examples of such intrusions related to Au-only skarns at the contact zone. Reduced Zn-Au skarns in China are inferred to be distal parts of such systems. Tungsten and Sn do not occur together as commonly as was previously thought. The distal part of a skarn ore system may transition to carbonate replacement deposits. Distal stratabound mantos and crosscutting veins/chimneys may contain not only Zn-Pb but also major Sn, W, Cu, Mo, and Au mineralization. The Zn-Pb mineralization may be part of either an oxidized system (e.g., Cu, Mo, Fe) or a reduced system (e.g., Sn). In China, distal Zn-Pb is more commonly related to reduced magmas. Gold and W may also be related to both oxidized and reduced magmas, although in China they are more typically related to oxidized magma. There are numerous examples of distal mantos/chimneys that continuously transition to proximal skarns at intrusion-wall-rock contact zones, and this relationship strongly supports the magmatic affiliation of such deposits and suggests that distal skarns/carbonate replacement deposits systems should be explored to find more proximal mineralization. Carbonate xenoliths or roof pendants may host the majority of mineralization in some deposits. In contact zones, skarns are better developed where the intrusion shape is complicated. The above two skarn positions imply that there may be multiple skarn bodies below drill interceptions of intrusive rocks. Many of the largest skarns for all commodities in China are related to small or subsurface intrusions (except for Sn skarns), have multiple mineralization centers, are young (<~160 Ma), and have the full system from causative intrusion(s) to distal skarns or carbonate replacement extensions discovered. Chinese skarn deposits fall in several age groups: ~830, ~480 to 420, ~383 to 371, ~324 to 314, ~263 to 210, ~200 to 83, ~80 to 72, and ~65 to 15 Ma. They are typically associated with convergent plate boundaries, mostly in subduction settings but also in collisional settings. Seven major skarn metallogenic belts are recognized based on skarn geographic location and geodynamic background. In subduction settings, skarns may form in a belt up to 4,000 km long and 1,000 km inland, with skarns continuously forming for up to 120 m.y., e.g., the eastern China belt. In most other belts, skarns form in 5- to 20-m.y. episodes similar to the situation in South America. In collisional settings, skarns may form up to 50 m.y. after an ocean closure, and the distance to the collisional/accretionary boundary may extend to ~150 km inland. The size of collision-related skarns may be as large as the largest skarns related to oceanic crust subduction. Older suture zones may be favorable sites for younger mineralization, for example, the Triassic Paleo-Tethys suture between the North and South China blocks for the younger and largest skarn cluster of the Middle-Lower Yangtze belt in the eastern China belt, and the Triassic sutures in southwestern China for Cretaceous to Tertiary mineralization

The Impact of Career Plateaus on Job Performance: The Roles of Organizational Justice and Positive Psychological Capital

Previous studies suggest that career plateaus have detrimental effects on employees’ satisfaction and performance. Psychological distress generated by career plateaus hinders organizations from achieving the United Nations’ Sustainable Development Goals (UNSDGs) of ‘health and well-being at work’ (SDG-3) and ‘decent work’ (SDG-8). How to mitigate the negative impact of career plateaus becomes the key to enhancing sustainable well-being at work. However, the influencing mechanisms of career plateaus have not been fully discussed, especially regarding employees’ psychological processes. Drawing on the equity theory and the conservation of resource theory, this study examines the influence mechanism of career plateaus on employee job performance via organizational justice, with positive psychological capital moderating the process. Mplus and the Process macro for SPSS are adopted to conduct confirmatory factor analysis and regression analyses. Building on 368 supervisor–employee paired questionnaires with an average of eight employees per supervisor, empirical results indicate that employees who encounter career plateaus reduce their perceived organizational justice to discourage them from performing well in their jobs. Positive psychological capital, however, mitigates the negative effects of career plateaus on perceived organizational justice and the indirect effects of career plateaus on job performance through organizational justice. Theoretically, this study advances our understanding of the influence mechanism of career plateaus on employees’ job performance. Practical implications are also drawn for organizations to alleviate the negative impact of career plateaus to promote sustainable well-being at work

Fluid compositions reveal fluid nature, metal deposition mechanisms, and mineralization potential: an example at the Haobugao Zn-Pb skarn, China

Fluid inclusion compositions obtained from laser ablation–inductively coupled plasma–mass spectrometry at the Haobugao Zn-Pb skarn in northeastern China provide constraints on fluid origin, evolution, and metal deposition mechanisms and an example of evaluating mineralization potential. Metal concentrations in the prograde fluids were high (up to 1.4 wt% Zn and 1.8 wt% Pb) but remained in solution, likely due to the high temperatures (440–575 °C) and salinities (35.4–45.3 wt % NaCl equivalent). Absolute concentrations of elements (e.g., Rb and Na) and mass ratios (e.g., Zn/Na and K/Na) reveal that the early, prograde fluids were magmatic, consistent with the oxygen isotope composition of fluids (δ18OH2O = 5.5‰–8.5‰). Later mixing with a meteoric fluid caused dilution and Zn-Pb deposition, as revealed by lowered element concentrations and Pb/(Na + K) and Zn/(Na + K) ratios in the sulfide-stage fluid inclusions. Elevated Ca/K ratios in sphalerite-hosted inclusions indicate fluid-carbonate reactions that buffered fluid pH, also facilitating Zn-Pb precipitation. Although cassiterite and molybdenite occur locally at Haobugao, mass balance calculation shows low metal endowment (maximum 2900 t Sn and 2200 t Mo) of the system. Furthermore, the generally unchanged Sn/(Na + K) and Mo/(Na + K) ratios from pre- to late-mineralization fluids suggest that the fluids were never saturated in Sn and Mo. Therefore, finding much Sn or Mo at Haobugao is unlikely. This demonstrates a potential tool for evaluating the metal endowment of a mineral prospect, which may guide exploration

Proactive Career Orientation and Subjective Career Success: A Perspective of Career Construction Theory

In the current dynamic and flexible work environment, traditional career models are constantly challenged by individuals’ self-concepts of career development. Previous studies have investigated the predictors of subjective career success, yet little is known about the impact of proactive career orientation on subjective career success. This study, grounded in the career construction theory, aims to examine the influence mechanism of proactive career orientation on subjective career success by analyzing questionnaire data from 296 employees. Empirical results indicate that proactive career orientation has a positive impact on subjective career success. Second, career adaptability partially mediates the relationship between proactive career orientation and subjective career success. Third, mentoring moderates the relationship between proactive career orientation and career adaptability, as well as the relationship between career adaptability and subjective career success. Specifically, both the positive impact of proactive career orientation on career adaptability and the positive impact of career adaptability on subjective career success are stronger when the level of mentoring is higher. Fourth, the indirect relationship between proactive career orientation and subjective career success through career adaptability is stronger when mentoring is high compared to when mentoring is low. This study contributes to the career construction theory by identifying the influence mechanism of proactive career orientation on subjective career success through career adaptability, with mentoring moderating the process. As for practical implications, research findings remind managers of the importance of career planning and mentorship in enhancing employees’ subjective career successes

Composition and evolution of fluids forming the Baiyinnuo'er Zn-Pb Skarn Deposit, Northeastern China: insights from laser ablation ICP-MS study of fluid inclusions

The Baiyinnuo'er skarn deposit is one of the largest Zn-Pb deposits in northeastern China, with 32.74 million metric tons (Mt) resources averaging 5.44% Zn, 2.02% Pb, and 31.36 g/t Ag. The deposit formed in three stages: the preore stage (prograde skarn minerals with minor magnetite), the synore stage (sulfides and retrograde skarn minerals including calcite and minor quartz), and the postore stage (late veins composed of calcite, quartz, fluorite, and chlorite; cutting the above mineral assemblages). In this study we analyzed the composition of single fluid inclusions using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to (1) determine the composition of the fluids and the evolution through the stages, (2) infer the fluid and metal sources, and (3) explore the metal deposition mechanisms. The preore fluids trapped in pyroxene have higher homogenization temperatures (432°–504°C), higher salinity (36.5–46.1 wt % NaCl equiv), and higher concentrations of Zn (~0.9 wt %), Pb (~1.4 wt %), and other elements (e.g., Na, K, Li, As, Rb, Sr, Cs, Ba, Cl, and Br) than synore mineralizing fluids (<370°C, <10 wt % NaCl equiv, ~450 ppm Zn, and ~290 ppm Pb). The postore fluids show lower temperatures (<250°C) and a rather dilute composition (<4 wt % NaCl equiv, ~33 ppm Zn, and ~24 ppm Pb). Geochemically, the fluids of all paragenetic stages in Baiyinnuo'er have magmatic signatures based on the element mass ratios, including elevated K/Na, Zn/Na, and Rb/Na ratios, lower Ca/K ratios, and combined Cl/Br-Na/K ratios, which are distinctively different from basinal brines. Inclusion fluids in preore stage show little variation in composition between ~510° and ~430°C, indicative of a closed cooling system. In contrast, the major components of the syn- and postore fluids, including Cl, Na, and K, decrease and correlate with a drop of homogenization temperatures from ~370° to ~200°C, indicating a dilution by mixing with groundwater. The Baiyinnuo'er mineralizing fluids (trapped in sphalerite) have higher Ca/K mass ratios (avg ~0.78) than other proximal magmatic hydrothermal systems (0.06–0.52) but lower than that of the distal El Mochito skarn (avg ~6.4), probably reflecting a gradually weakened magmatic signal away from the causative intrusions. The metal contents in preore fluids are significantly higher than those in synore fluids, but no mineralization occurred. This confirms that the early fluids were, although enriched in metals, not responsible for ore precipitation, most likely due to their high temperature and high salinities. One important factor controlling Zn-Pb mineralization was mixing with groundwater, which resulted in temperature decrease and dilution that significantly reduced the metal solubility, thereby promoting metal deposition. Another main driving force was the interaction with carbonate wall rock that buffered the acidity generated during the breakdown of Zn and (Pb)-Cl complexes and the precipitation of sulfides. Phase separation occurred in both the preore and the early part of the synore stages, but no evidence indicated that it caused metal deposition. The prograde minerals and retrograde minerals (including ore minerals) coexisting in the same samples could have been caused by two (or more) successive pulses of hydrothermal fluids released from residual melts of a progressively downward crystallizing magma. Each fluid produced a series of proximal high-temperature prograde to distal low-temperature assemblages, with the lower temperature assemblages of later fluids overprinting the higher temperature assemblages at most locations

Regional metallogeny of Mo-bearing deposits in northeastern China, with new Re-Os Dates of porphyry Mo deposits in the northern Xilamulun district

With many new discoveries of giant Mo deposits in the past decade, northeastern China has become the largest molybdenum mineralization region in China. The Xilamulun district is in the southern part of northeastern China and contains 25 Mo deposits and prospects, dominantly of porphyry type. These deposits are mostly along the E-striking Xilamulun fault. Re-Os dating of hydrothermal molybdenite from four deposits in the northern Xilamulun district revealed mineralization ages of 137 to 129 Ma (129.4 ± 3.4 Ma for Aolunhua, 135.3± 2.6 Ma for Shabutai, 136.4 ± 0.8 Ma for Haisugou, and 136.1 ± 6.6 Ma for Banlashan), in general agreement with the crystallization ages of their host granitoids.\ud \ud The compilation of existing data on Mo-bearing deposits in northeastern China, including the new data of this study, shows that Mesozoic Mo deposits in this region have a wide range of ages, from ~250 to 90 Ma. We propose that they are linked to three tectonic-magmatic events: (1) Triassic Mo deposits (250–220 Ma) are mainly distributed along the E-trending Xilamulun fault and are related to postcollisional crustal extension following the final closure of the Paleo-Asian ocean; (2) Jurassic Mo mineralization (200–140 Ma) displays a clear younging trend from southeast to northwest, coincides with the regional magmatism trend, and is interpreted to be related to the northwestward flat-slab subduction of the Paleo-Pacific plate beneath the Eurasian continent that started in the Early Jurassic (ca. 200 Ma); (3) Cretaceous Mo mineralization (140–90 Ma) shows a reversed migration trend from northwest to southeast, and can be explained by the coastward migration of slab rollback related to lower crust delamination, asthenospheric upwelling, and lithospheric thinning in eastern China. The spatial-temporal distribution of Mesozoic Mo mineralization is important for regional metallogeny and exploration. Recently numerous epithermal Au (Cu, Mo) deposits have been recognized in the southeast margin of northeastern China. According to this study, we predict that hidden porphyry/skarn systems could be located beneath these epithermal deposits

Zircon trace elements and magma fertility: insights from porphyry (-skarn) Mo deposits in NE China

It has been widely accepted that magmas genetically linked to porphyry (-skarn) Cu (Mo) deposits are commonly oxidized. Recently, using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) techniques, zircon Ce4+/Ce3+, Ce-N/Ce-N*, Eu-N/Eu-N*, and Ce/Nd ratios, and magma FMQ values (departure from the fayalite-magnetite-quartz oxygen buffer) based on zircon trace element compositions, have been used as proxies to quantify magma oxidation state. Here we present the zircon trace element compositions of 13 Mesozoic porphyry (-skarn) Mo deposits in NE China of various sizes to examine the relationship between magma Mo fertility and magma oxidation state. Generally, the studied deposits with >0.3Mt Mo have Ce4+/Ce3+>100, Ce-N/Ce-N* >100, Ce/Nd >10, and Eu-N/Eu-N* >0.3, whereas those containing 10Mt Cu. The findings in this study can be used to evaluate an intrusion's potential to produce Mo mineralization