Large Deposits Research Articles

The influence of large wood on sediment routing and flow characteristics: A study in a low-order stream in the southern brazilian plateau

The coupling of sediment sources varies in terms of efficiency and availability based on the frequency and intensity patterns of rainfall events over time. It is commonly assumed that reaches with steeper gradients have higher longitudinal connectivity, while lower gradient reaches have lower longitudinal connectivity. However, considering that the longitudinal connectivity of channels is not always perfectly established, this conception regarding channel gradient may not always hold true. In forested regions, elements such as large wood can be the main agents of this disconnectivity. Thus, this study investigates the effects of large wood on sediment flux, flow characteristics and channel morphology in the context of the Atlantic Forest Biome in a low-order stream in the southern Brazilian plateau. To achieve this, measurements of hydrological variables, characterization of sediments, and channel morphology were conducted. Hydraulic and morphological variables were estimated to define hydraulic signatures for each river section. The influences of large wood barriers in the study section were highlighted through an analysis of hydraulic characteristics at different cross-sections and the assessment of morphological variables. The investigation revealed a tendency for a reduction in velocity of approximately 90 % in low-discharge conditions in sections where large wood barriers were present. In the case of high-magnitude events, the velocity reduction was considerably lower. Additionally, it was found that each large wood deposit presented uniqueness, and the structural characteristics of each reflected the potential for system disconnectivity. Finally, it was observed that both barriers have the capacity to store sediments, leading to the constriction of the cross-section due to the formation of sediment bars, although surveys revealed that fine sediments were poorly retained in both barriers.

A Comparative Analysis of the Gas Pipeline Geopolitics of China and India in the Central Asia Republics

After the discovery of large oil and gas deposits in Central Asia, the region has become a vital battlefield for major world powers’ competing interests, resulting in a complex geopolitical and energy transportation interaction known as ‘pipeline politics’. After independence, multinational energy companies and global powers contacted the Central Asian Republics. Chinese investment has dominated the region’s energy sector throughout the past decade. India is strategically seeking Central Asia’s energy resources as it becomes more global. This article compares China’s and India’s Central Asian natural gas strategy and identifies research shortcomings. The complex geopolitical landscape is considered while examining their objectives and regional investments. This analysis reveals these methods’ motivations and their effects on the Central Asian Republics and the world. China has an advantage over India in Central Asian pipeline politics, making the region vital to China’s energy security.

Control of Ag deposition for improvement of specular reflection in Ag deposition-based electrochemical mirror through modulation of electrolysis condition

The reflection behavior of an Ag deposition-based reversible electrochemical mirror is determined by the morphology of the electrodeposited Ag. This study demonstrates the control of the morphology of Ag deposits through the modulation of the electrolysis conditions, specifically the applied potential and Ag+ ions concentration, without increasing the amount of Ag deposits. By applying a potential with a sufficiently large deposition overpotential for continuous deposition on the electrode surface, the deposited Ag formed a flat surface, resulting in high reflectivity. Considering the concentration dependence of Ag+ ions, the diffusion of Ag+ ions to the electrode significantly affected the resulting morphology of the deposits. At higher Ag+ concentrations, the time for the transition to a diffusion-limited process increased because Ag+ ions were close to the working electrode. Therefore, a flat Ag layer was obtained due to the promotion of three-dimensional deposition, including the in-plane growth.

Time-transgressive microbial diversity in a tropical bat guano accumulation, Deer Cave, Mulu, Borneo

Bat guano accumulations in caves can constitute large deposits of organic material, particularly chitin and its degradation products, that host a diverse microbiome. Previous microbiological studies have not addressed the stratified nature of these deposits in the context of the timeframe of the decomposition process. We present such data (temperature, pH, DNA sampling of eight carbon-dated strata) for a 75 cm-deep tropical guano accumulation that undergoes complete decomposition over a timescale of ~120 years. The aerobic, surface layer of freshly-fallen guano has the greatest diversity of taxa, with Bacteroidota co-dominant with Pseudomonadota, and includes many taxa unique to this zone (including those from guanophagic invertebrates, bat guts, and insects). The ~20-40-year-old, more anaerobic, middle layer of increasing acidity and temperature has fewer taxa, with Pseudomonadota dominant and Bacteroidota almost disappearing, and many taxa tolerant of high temperatures and anaerobic conditions. The ~60-120-year-old, deepest, zone has the lowest diversity with a single genus of Actinomycetota (Mycobacterium) taking over as dominant. We also present data on the significantly different microbiomes of guano falling into aerobic versus water-logged, anaerobic conditions at the surface, the anaerobic having almost twice the diversity of the aerobic, including many taxa that are unique to this sample. Taxa of especial interest include methanogens, sulphur reducers and oxidizers, chitin decomposers, halophiles, acidophiles, and extremophiles.

Mantle-plume model for the Zun-Kholba orogenic gold deposit (Eastern Sayan, Russia): results of mineralogical, Rb-Sr and <sup>40</sup>Ar-<sup>39</sup>Ar geochronological and Pb-Pb isotopic studies

The large Zun-Kholba deposit, belonging to a numerous group of orogenic-type gold deposits, is in the Eastern Sayan (Russia) – a segment of the Altai-Sayan fold system of the Central Asian Orogenic Belt. The paper discusses the results of mineralogical, geochemical, geochronological and Pb-isotopic studies of gold mineralization, the purpose of which was to verify the genetic model of the deposit. Mineralogical and geochemical data obtained for ore bodies located between hypsometric levels from 1290 to 2090 m indicate a complex distribution of mineral associations at the deposit. There is no vertical and horizontal zonation in the distribution of mineral associations, in the chemical composition of the main ore minerals, as well as in the content of impurity elements in them. In dating ore-forming processes at the Zun-Kholba deposit, a comprehensive approach based on the study of K-Ar and Rb-Sr isotope systems of metasomatites was applied. The combination of Rb-Sr and 40Ar-39Ar methods allowed us to determine that the age of gold mineralization is 411 ± 2 Ma, while the age of the superimposed event, which is associated with redistribution of ore, as well as disturbance of the Rb-Sr and K-Ar isotopic systems of metasomatites, is about 380 Ma. Pb-Pb isotopic study of ore mineralization at the deposit and host Precambrian rocks allowed to prove the leading contribution of the latter in ore lead supply to the mineral-forming system. The model of formation of the Zun-Kholba orogenic gold deposit assumes a genetic relationship between ore-forming processes and intraplate alkaline mafic magmatism due to the impact of the plume in the Early Devonian time on the lithosphere of the Tuva-Mongolian terrane.

ANALISIS PEMBERLAKUAN TARIF MIKRO ANGKUTAN ANTAR KOTA TRAYEK KOTA GORONTALO PAGUAT

Analysis of the Implementation of Micro Tariffs for Inter-City Transport on the Gorontalo Paguat City Route. The aim of this research was to overcome the existence of micro drivers who charge their own transportation rates which are not in accordance with the provisions of established regulations. With the data collection method, interviews or in the context of this research, they are called informants. In this data source, the informants include the drivers, the Head of the Talaga Terminal Coordinator, Gorotalo City and the community, place, namely the data source obtained from a description of the situation and conditions related to the problem being discussed, Paper, namely the data source that presents signs in the form of letters. , numbers, images, or symbols. Based on the district regulation. Gorontalo number 28 of 2013 concerning adjustments to passenger transportation rates between cities, sub-districts and rural areas for economy class, namely Rp. 437.46,- /km/pnp. Based on these regulations, the Gorontalo-Paguat route is approximately 145km, namely Rp. 63,431,- or around Rp. 63,500,-. Meanwhile, the fare applied by micro drivers is Rp. 75,000. This is due to the large deposits made to the PO which covers the drivers, as well as the increasingly high cost of living necessities, therefore the government needs to review the determination of micro tariffs for public transport on the Gorontalo-Paguat route.

Geochemistry of Middle Jurassic Coals from the Dananhu Mine, Xinjiang: Emphasis on Sediment Source and Control Factors of Critical Metals

In recent years, coal-type critical metal deposits have become a research hotspot in coal geology. As a major coal-accumulating basin in the Xinjiang area, the Turpan-Hami Basin contains abundant coal resources and has the potential to become a large coal-type critical metal deposit. However, previous studies on the enrichment characteristics of critical metal elements in coal are few and need further research. Based on SEM-EDS, XRF, and ICP-MS experiments, this study investigates the coal petrology, mineralogy, and geochemistry of the No. 22 coal of the Xishanyao Formation from the Dananhu Coal Mine, Xinjiang, to identify the sediment source, depositional environment, and controlling factors of the critical metal elements of the No. 22 coal. The results showed that the Dananhu coals are characterized by a low ash yield, low total sulfur content, high volatile yield, and high inertinite proportions. Quartz, kaolinite, and illite are the main minerals in the coal. Compared with the world’s low-rank coals, Ni, Co, Mo, and Ta are slightly enriched, Li, Rb, Cs, Ba, Tl, Bi, and Ge are depleted, and the concentrations of other trace elements are comparable to the average values of the world’s low-rank coals. The REY of the Dannanhu coals exhibited high fractionation, with its enrichment patterns characterized by the H-type and M-H-type. Although most of the critical metals are not enriched in the Dannanhu coals, the Ga, Zr (Hf), and Nb (Ta) concentrations in the coal ash of the Dannanhu coals have reached the economic cut-off grade and have the potential to be a substitute for rare metal resources. The terrigenous detrital sources of the Dannanhu coals mainly come from the Paleozoic dacite, andesite, and a small amount of granite from the Harik Mountain and Eastern Bogda Mountain in the Turpan-Hami Basin. The Dannanhu coals are generally in a dry and hot depositional environment, with high salinity and weak reduction-oxidation. The low source input and weak reduction-oxidation environment have resulted in low concentrations of critical metal of the No. 22 coal from the Dananhu Coal Mine.

Transcriptomic and Metabolomic Analyses Reveal Molecular Regulatory Networks for Pigmentation Deposition in Sheep.

Domestic animals have multiple phenotypes of skin and coat color, which arise from different genes and their products, such as proteins and metabolites responsible with melanin deposition. However, the complex regulatory network of melanin synthesis remains to be fully unraveled. Here, the skin and tongue tissues of Liangshan black sheep (black group) and Liangshan semi-fine-wool sheep (pink group) were collected, stained with hematoxylin-eosin (HE) and Masson-Fontana, and the transcriptomic and metabolomic data were further analyzed. We found a large deposit of melanin granules in the epidermis of the black skin and tongue. Transcriptome and metabolome analysis identified 744 differentially expressed genes (DEGs) and 443 differentially expressed metabolites (DEMs) between the pink and black groups. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses revealed the DEGs and DEMs were mainly enriched in the pathways of secondary metabolic processes, melanin biosynthesis processes, melanin metabolism processes, melanosome membranes, pigment granule membranes, melanosome, tyrosine metabolism, and melanogenesis. Notably, we revealed the gene ENSARG00020006042 may be a family member of YWHAs and involved in regulating melanin deposition. Furthermore, several essential genes (TYR, TYRP1, DCT, PMEL, MLANA, SLC45A2) were significantly associated with metabolite prostaglandins and compounds involved in sheep pigmentation. These findings provide new evidence of the strong correlation between prostaglandins and related compounds and key genes that regulate sheep melanin synthesis, furthering our understanding of the regulatory mechanisms and molecular breeding of pigmentation in sheep.

Simulation of triggering and evolution of ELM by pellet injection in EAST under BOUT++ framework

A BOUT ++ three-field magnetohydrodynamic model is employed to study the triggering and evolution of edge localized mode (ELM) by Li pellets injected along the outer mid-plane in the EAST configuration. The linear simulation shows that compared with a large deposition on the pedestal top (scenario I), a smaller deposition within the steep-gradient pedestal region (scenario II) can stimulate much larger linear growth rates of all-n peeling-ballooning modes (PBMs). The nonlinear simulation shows that there exists a pellet size threshold for ELM triggering for two deposition locations; the threshold for scenario I predicted in the present study matches the EAST observation well. Comparison of the two scenarios reveals that a smaller deposition is sufficient to trigger an ELM in a much shorter time in scenario II, whose ELM size is comparable to that in scenario I. This conclusion confirms previous DIII-D and ASDEX-Upgrade observations, suggesting that the steep-gradient pedestal region is a favorable deposition location for ELM triggering with minimum pellet size. Simulation analyses also find that the positive radial gradient of the hump-like pressure profile in the outer mid-plane induced by the pellet deposition plays a different role in the two scenarios. In scenario I, the force resulting from the gradient hinders the outflow of core plasmas and in return, the perturbation is suppressed from spreading inwards after ELM crashes. In scenario II, with a sizable deposition, the gradient results in another competitive perturbation growth region during the linear phase, thus dispersing the free energy and reducing the efficiency of destabilizing PBMs by pellet injection. The suppressing effect of saturated zonal flow on other modes, the short ELM fast crash phase, and the restricting transport effect of the positive radial pressure gradient work together to constrain the pedestal energy loss, especially when the pellet deposition amount is high.

A visual construction history of the West Lothian shale bings

The West Lothian shale bings are large deposits of spent-shale rock in Scotland, created by the first industrial scale oil refineries which operated in the region from the mid-19th to the mid-20th century. Through its visual format, this gallery essay eschews formal investigative strategies to break with previous scholarship and interpret the bings as structures with their own construction history. Images of their current shape have been substituted for plans, photos and representations of them in development, to highlight the various logics and designs that converged within their construction. First-hand accounts from archived interviews have also been used to integrate the sensory and personal information that animated the bings as they were built. Social production is centred in this way to undermine an ideological narrative that sees waste as either aberrant corollary to intensive industry, or a neutral object without history. Analysing each image of the bings reveals intent, calculation and purpose which are pointedly incongruous with the view of waste as monolithic, accidental or unconscious. Such interpretations must be challenged because they obfuscate the necessarily profound impact of capital upon environmental history, as well as denuding ecology of its social aspects.

Mineralization based on CSAMT data: A case study on the Gaoloushan section of Yangshan gold belt

AbstractYangshan gold belt (YSGB) in Gansu Province is a super‐large orogenic gold deposit located in the middle section of the Mianxian‐Lueyang arcuate suture zone (Mian‐Lue suture zone). The YSGB is mainly divided into the Gejiaowan, Anba, and Gaoloushan mine sections. The ore veins are strictly controlled by strong strain zones in the fracture zone and secondary fractures superimposed on the inherited activity and are vein‐like in general and lenticular in localities. For a long time, there have been different understandings regarding its ore‐controlling factors and mineral genesis. By utilizing controlled‐source audio‐frequency magnetotellurics (CSAMT) technology to conduct electrical characteristic studies, the deep electrical structural characteristics of the Gaoloushan section are identified, and a tectonically‐controlled geoelectric model of the deposit is established, which provides geophysical evidence for the view that the Yangshan gold mine is a tectonically‐controlled low‐temperature hydrothermal deposit in altered rock, guiding the arrangement of exploration work and identifying prospective mining areas, and thereby providing a geophysical exploration paradigm for deep exploration of large orogenic gold deposits.

Hydrogeochemical characteristics and enrichment regularities of groundwater uranium in the Erlian basin, China

Groundwater is a key medium for the migration and enrichment of elements into ore bodies in sandstone-type uranium deposits, with anomalies of uranium elements and their associated components in water serving as indicators for exploring such deposits. The Erlian Basin, located in central-northern Inner Mongolia, is a crucial production area for sandstone-type uranium deposits in China. The groundwater flow system in the basin plays a significant role in the formation of uranium deposits. To study the hydrogeochemical characteristics and enrichment regularities of groundwater uranium in the Erlian Basin, 269 groundwater samples were collected. Hydrogeochemical analysis methods, such as Piper diagrams, Gibbs diagrams, and contour maps, were employed to determine the distribution characteristics and occurrence forms of groundwater uranium in the study area. The primary water chemistry types in the study area were HCO3–Ca•Na, HCO3–Na, HCO3•SO4–Na, and SO4•HCO3–Na•Ca. The distribution range of uranium content in groundwater in the study area was 0.1–453 μg/L (average of 53.08 μg/L). A comprehensive analysis, based on the direction of groundwater flow and changes in the redox environment, suggested that the higher uranium values in groundwater were distributed in the runoff and discharge areas, with uranium anomaly points existing in areas with alternating oxidation and reduction zones. These uranium anomaly points were in good agreement with the known large uranium deposits of Nuheting, Qiharigetu, Daoersu, and others, thereby predicting six other uranium hydrochemical anomaly points as prospective areas for uranium mineralization. The pH value distribution range in the study area's groundwater was 6.8–9.1, and the redox potential (Eh) value range was -126–52 mV, indicating that uranium exists in groundwater in the form of UO2(CO3)34− and UO2(CO3)22−. An increase in bicarbonate (HCO3−) is conducive to uranium dissolution. The enrichment and occurrence forms of uranium in groundwater are influenced by the concentrations of Fe and (Ca2++Mg2+), with uranium precipitation and enrichment occurring as the groundwater evolves and changes in the redox environment. The uranium content in deep wells is higher than in nearby shallow wells, indicating that deep water circulation is beneficial for mineralization. The pH, Eh, HCO3−, Fe, and other hydrogeochemical indicators are indicative of uranium enrichment; thus, they can be considered as reference bases when exploring for potential uranium resources.

Geochronology and geochemistry of granites from the Longhua Ni-Co deposit, South China: Implication for the formation of Ni-Co mineralization

Mineral exploration activities since 2010 in a previously poorly explored region of northeastern Guangxi province, South China, confirmed the existence of a potentially large hydrothermal Ni-Co deposit. As a newly discovered deposit, many aspects of this deposit are still unclear, including in which tectonic setting the deposit formed and how the high-grade mineralization developed. To address these questions, in this study, we conduct a comprehensively geochronological and geochemical study on the Dajin pluton (consisting of biotite monzogranite and sericitized monzogranite), which is the only pluton occurring in the district. LA-ICP-MS zircon U-Pb dating shows that two types of granites were emplaced nearly at the same time, with biotite monzogranite and sericitized monzogranite being 449 ± 15 Ma and 448.4 ± 8.8 Ma, respectively. This, combined with previously published studies, confirms that the Dajin pluton was broadly emplaced during the formation of the Longhua deposit. These granites are characterized by high K2O, and noticeable depletion of Eu, Sr, P and Ti, with whole-rock εNd(t) values ranging from −1.99 to −4.26 and zircon εHf(t) values ranging from −0.9 to 4.1. These features support that the studied granites are typical of A2-type granites, which experienced strong fractional crystallization and formed in a post-collisional environment. Although Co and Ni might not have been originally derived from granitic magmas, we suggest that the emplacement of the Dajin pluton facilitated the formation of high-grade Ni-Co mineralization in two ways: (1) melting the Co– and Ni-enriched mafic basement probably existing in the deep crust, and (2) remobilizing and concentrating metals from wall rocks.

Geochronology, geochemistry, and isotope signatures of porphyries from the dabate Mo—Cu deposit, Western Tianshan, China: Implications for petrogenesis and geodynamic setting

The Dabate deposit in the West Tianshan Orogenic Belt is a large porphyry Mo-Cu deposit with obvious zoning feature. The Dabate pluton is closely related to mineralization associated with the rhyolite and granite porphyries. Copper (Cu) mineralization occurs on the margin of the rhyolite porphyry, and molybdenum (Mo) mineralization occurs in the interior of the rhyolite porphyry. Petrology, zircon U-Pb isotopic data, whole-rock geochemistry, and Sr-Nb-Hf-Pb isotopic data of the rhyolite and granite porphyries in the Dabate Mo-Cu mining zone and to discuss the properties, sources, evolution, and tectonic environment of the magma. Zircon U-Pb age dating shows that the rhyolite porphyry and granite porphyry were formed in 300.1 ± 1.3 Ma and 290.4 ± 5.2 Ma, respectively, and they are geochemically similar. Both are characterized by negative Eu anomalies (δEu = 0.09–0.15 and 0.10–0.11, respectively) and are slightly rich in light rare earth elements (LREE) but depleted in high-field-strength elements (HFSE), which indicates that they are both A2 type granites that underwent high differentiation. The Sr isotope (ISr) values for the rhyolite and granite porphyries range from 0.70564 to 0.70658 and 0.70833–0.70954, respectively. The Nd isotopic composition [εNd(t)] values for both are negative but close to zero (−0.25 to −0.46 and −0.65 to −1.10, respectively), and the two-stage depleted mantle Nd model ages (TDM2(Nd)) are 1.07–1.10 Ga and 1.11–1.14 Ga, respectively. Zircon εHf(t) values are 7.29–11.97 and 6.26–11.08 for rhyolite porphyry and granite porphyry, respectively, and the two-stage Hf model ages (TDM2(Hf)) are 550–848 Ma and 605–916 Ma, respectively. The initial Pb isotope ratios for the rhyolite and granite porphyry are close at (206Pb/204Pb)i = 18.26–18.65, (207Pb/204Pb)i = 15.54–15.64, and (208Pb/204Pb)i = 38.19–38.57. These results indicate that the two porphyries have a mixed source, likely originating from the partial melting of mantle blended with some recently formed lower crust material. The geochronology, geochemistry, and Sr-Nd-Hf-Pb isotope data of existing intrusions in the West Tianshan imply that the Late Carboniferous to Early Permian Dabate area was underplated in a post-collisional extensional setting, and A2-type granite intrusions with related Mo-Cu mineralization were formed.

Hydrothermal enrichment of rare earth elements in the Lower Permian Lijiatian bauxite deposit, southern China

Bauxite deposits are an important source of Al and also host a variety of critical metals, including rare earth elements (REEs). However, the parent rocks of bauxite deposits generally have low REE contents, leading to uncertainty over the REE sources and enrichment mechanisms. In this study, we report high REE (2095 ppm; Ce = 1340 ppm) contents in the Lijiatian bauxite deposit in Luxi County, western Hunan Province, South China. The Lijiatian bauxite deposit is the largest deposit in Hunan Province, with a total Al resources exceeding 7 × 106 tons. The ore-bearing strata in the lower Permian Liangshan Formation (ca. 275 Ma) are comprised a 3–5-m-thick bauxite layer (bauxite ore/clay) and an underlying 4–8-m-thick Fe layer (Fe ore/Fe-rich clay). The high REE contents in the bauxites can be attributed to the widespread presence of bastnäsite. The bastnäsite commonly coexists with authigenic chlorite, which formed at temperatures of 221–285 °C, indicative of a hydrothermal origin. Uranium–Pb dating of the bastnäsite yielded an age of 141.4 ± 7.0 Ma, indicating a hydrothermal overprint occurred during the Early Cretaceous, which resulted in the enrichment of REEs in the bauxites. The high contents of REEs, Ba, and P in the Cambrian Niutitang Formation black shales indicate it was a potential source of these elements for bastnäsite and coexisting barite and apatite. The deep-seated hydrothermal fluids (enriched in HF, CO2, and H2S) associated with the late Yanshanian extensional tectonic event in South China (155–123 Ma) ascended along fractures. The ascending fluids interacted with the black shales, extracting REEs, Ba, and P. When the fluids reached a certain depth, they mixed with the infiltrating basinal waters to form a mineralising fluid. The fluid then migrated towards the bauxite layers, underwent cooling and depressurisation, and precipitated bastnäsite, barite, apatite, and chlorite. We propose that a hydrothermal event led to the enrichment of REEs in the bauxites in Hunan Province. Considering the scarcity of REEs in the parent rocks of bauxites worldwide, hydrothermal activity likely has a key role in REE enrichment in bauxites.

Авландинский палеовулкан и золото-серебряное оруденение

The article describes the geological structure and composition of the Avlandya stratovolcano, composed of cover and intrusive volcanites of the Late Devonian - Early Carboniferous Kedonian series. The paleovolcano area corresponds to the Avlandya ore cluster. The sector block on the southwestern periphery of the paleovolcano is the Kubaka ore field, which contains the large Kubaka gold and silver deposit and a number of occurrences. Textural features, the composition of ores and native gold indicate that the Kubaka deposit belongs to the volcanogenic gold-silver formation. The geological criteria of the Kubaka's Middle Paleozoic age have been determined.

ПЕРСПЕКТИВЫ ИСПОЛЬЗОВАНИЯ МЕСТОРОЖДЕНИЙ ПОДЗЕМНЫХ ВОД КАЗАХСТАНСКОЙ ЧАСТИ ПРЕДГОРИЙ КИРГИЗСКОГО АЛАТАУ ДЛЯ ОРОШЕНИЯ И ХОЗЯЙСТВЕННО-ПИТЬЕВОГО ВОДОСНАБЖЕНИЯ СЕЛЬСКИХ НАСЕЛЕННЫХ ПУНКТОВ ЖАМБЫЛСКОЙ ОБЛАСТИ

In this area, 4 large deposits of groundwater were explored, including for irrigation. Prospects for the use of groundwater in the Kazakhstan part of the foothills of the Kyrgyz Alatau for irrigation and domestic and drinking water supply to rural settlements in the southern part of Zhambyl region to ensure economic growth and development of agriculture in the region

Metal remobilization at the Nibao gold deposit in Youjiang basin, SW China: Implications from mineral texture, trace element and sulfur isotope compositions of sulfides and TiO2 polymorphs

Multistage mineralization overprinting is important for the formation of giant hydrothermal gold deposits. The Youjiang basin in SW China has undergone at least three major deformation phases in the Mesozoic, but their relationship with the large-scale gold accumulation in the region remains enigmatic. Here, we study the large Nibao gold deposit (reserve > 70 t Au) in the northern part of the basin, which has both fault-controlled and stratabound orebodies. We identified a pre-ore stage and syn-ore stage including four tectono-hydrothermal (T-H) substages (i.e., T-H stage 1, 2, 3 and 4) for the local mineralization at Nibao. The pre-ore stage is dominated by coarse-grained pyrite coexisting with TiO2 polymorphs in the Middle-Late Permian basaltic rocks. The T-H substage 1 is characterized in that the sedimentary pyrites are brecciated in bedding-parallel faults. Fluorination and silicification occur in the T-H substage 2, which is re-brecciated at the T-H substage 3 forming the highest gold grade ore in high-angle thrust fault. The T-H substage 4 presents as fault reactivation within minor calcite and pyrite deposition. Mineralogy and in-situ trace element analyses reveal that mineral dissolution and reprecipitation (incl. dolomite, auriferous pyrite and TiO2 polymorphs) is ubiquitous during the multistage tectono-hydrothermal process, and the continuous alteration overprinting may have promoted gold accumulation. This replacement process of different generations of auriferous pyrite is also recorded by their inherited sulfur isotopes, giving a narrow δ34S (−3.1 to + 2.1 ‰) range. Anatase is the main accessory phase of TiO2 polymorphs, as identified with LA-ICP-MS trace element and laser Raman spectroscopic analyses. Moreover, the anatase can been divided into two types (type-I and II) based on their texture, alteration and chemistry. The type-I anatase commonly occurring in the stratabound ore is characterized by higher Zr (mean 1,730 ppm), V (mean 1,412 ppm), and Cr (mean 110 ppm) contents than type-II that coexists with zoned pyrite in the fault-controlled ore (mean 26 ppm, 187 ppm, and 38 ppm, respectively). Additionally, W (mean 636 ppm) and Mg (10,021 ppm) in type-II are much higher than type-I ones (mean 135 ppm W and 476 Mg). These features show that the sedimentary-stage Zr-V-Cr-rich type-I anatase was dissolved via fluid metasomatism, and reprecipitated as the hydrothermal-stage W-Mg-rich and Zr-poor anatase, with gold gradually enriched. Besides, the anatase phase of TiO2 polymorphs also indicates that the Nibao gold deposit was formed under low pressure–temperature condition. Overall, we propose that the Nibao is a Carlin-type gold deposit, dominated by multistage tectono-hydrothermal events.

Genesis of the sediment-hosted Qukuleke Au deposit in the East Kunlun Orogenic Belt, NW China: Constraints from geology, apatite U–Pb age, and C–O–S–Pb isotopes

Genetic classification of sediment-hosted Au deposits is often disputed in many orogenic belts around the world. The marine sediment-hosted Qukuleke Au deposit (>5 t Au) is an example of this, which has been attributed to orogenic or intrusion-related type. This paper addresses its metallogeny through detailed geologic and petrographic studies, together with apatite U–Pb dating and C–O–S–Pb isotopes.The hydrothermal paragenesis at Qukuleke is divided into three stages (I to III): Stage I (pre-ore) sheeted quartz veins; Stage II (main ore) pervasive sericite ± carbonate ± apatite ± pyrite ± arsenopyrite alteration associated with quartz–calcite ± stibnite veins; Stage III (post-ore) barren calcite veins. LA-ICP–MS hydrothermal apatite U–Pb dating on Stage II disseminated Au ore yielded 208.1 ± 6.5 Ma, coeval with the Late Triassic post-collisional intrusions from the periphery of Qukuleke deposit. Carbon–oxygen isotopes of Au–Sb ore-related hydrothermal calcite show that the hydrothermal fluids were derived from the marine carbonate ore host with considerable magmatic input. Lead–sulfur isotopes of the Au–Sb ore-related are consistent with those of coeval intrusions around the deposit, but different from those of the local sedimentary strata. Our age and geochemical data suggest the presence of a magma source that supplied the hydrothermal fluids, sulfur and metals for the mineralization. Combining the low sulfide content and the Au–As–W–Sb–Mo assemblage characteristics, the Qukuleke is best classified as a sediment-hosted intrusion-related Au deposit. Considering also the discovery of the large coeval Qukukekedong Au deposit nearby, we propose that Late Triassic intrusion-related Au system is a high-potential exploration target in the western EKOB.

Decoupling of Cu and Zn in sediment-hosted base metal deposits: Evidence from LA-ICP-MS analyses of fluid inclusions and trace elements in minerals at Baiyangping, China

Copper and lead–zinc mineralization in basinal rocks worldwide commonly shows distinct spatiotemporal zonation. The Baiyangping deposit in the Lanping Basin, southwest China, is a large sediment-hosted polymetallic deposit that shows clear and pronounced zoning of Cu versus Pb-Zn mineralization. Here, we analyzed trace elements in pyrite and sphalerite and fluid inclusions in sphalerite, celestine, quartz, and dolomite to seek insights into the origins of the ore-forming fluids and the processes that govern the separation of Cu- from Zn-rich ores. We show that while the later Zn-rich mineralization is characterized by fluid inclusions showing typical hallmarks of basinal brine composition (low homogenization temperature < 230 °C, high salinity > 20 wt% NaCl eq., dominated by Na-K-Ca-Mg chlorides), the earlier Cu-rich mineralization shows markedly distinct composition that more closely resembles deeply-circulated water that has equilibrated with crystalline basement rocks (higher homogenization temperature of 210–280 °C, variable but lower salinity of ∼ 5–15 wt% NaCl, dominated by Na-K-Li chlorides). Pyrites formed during the earlier Cu-rich stage show elevated Cu, Co, Sb and Zn, while pyrites formed during the later Pb-Zn stage are more enriched in As, Pb and Mn. We interpret that the earlier-formed Cu-rich ores were deposited by deeply sourced fluids that ascended along basement-penetrating reverse faults, whereas the later Zn-rich ores were formed by subsequent circulation of fluid from within the basin, whose flux was promoted by shallower strike-slip faults. Hence, the two ore types reflect discrete pulses of chemically distinct hydrothermal fluids. We suggest that the evolving structural controls and fluid pathways during prolonged ore formation allowed sequential pulses of fluids that had acquired different metal budgets by equilibration with different sources. We suggest that this type of two-step process may be more common in sediment-hosted base metal deposits than single-fluid cooling sequential order of precipitation.