Rich Mineral Research Articles

China – Angola – Russia: Non-existing Triangle

This article contains the detailed comparative analysis of Russian and Chinese participation in the economic development of one of the most important African countries. The article highlights the history of credits and loans, foreign direct investments to Angola, dynamics of Russian and Chines trade turnover in the 21-st century. Main projects of Russia-Angola economic co-operation, activities of the biggest Chinese companies in Angola are in the scope of this research. Main economic interest of both powers – China and Russia – is to obtain access to the rich energy and mineral resources of Angola. However, any numerical indices of Russian and Chinese involvement into Angolan economics show that Russia cannot compete with China in this respect. Incomparable scale of trade turnover and economic cooperation make the hypotheses about possible “rivalry” between Russia and China in this region groundless. In spite of the fact that China has reduced loans volumes to Angola recently, the trade between the two countries shows increasing trend. For the time being Russia seems competitive to China in military cooperation with Angola though falls behind in humanitarian sphere.

Layered Sodium Manganese Oxide Na2Mn3O7 as an Insertion Host for Aqueous Zinc-ion Batteries

ABSTRACTAqueous rechargeable batteries are attractive owing to their higher operational safety, high ionic conductivity, scalable and easy manufacturing. These aqueous batteries form an economic option for large-scale (grid) power storage. In the aqueous battery sector, Mn-based compounds are highly attractive with their non-toxic nature, low-cost, rich mineral chemistry and robust operational safety. Several Mn-based systems like LiMn2O4 spinel and LiNi1/3Mn1/3Co1/3O2 have seen successful commercialization. Pursuing Mn-based materials, we have shown layer structured Na2Mn3O7 as a versatile cathode material for non-aqueous systems like Li-, Na- and K-ion batteries. In the current work, we have exploited Na2Mn3O7 as a cathode material for aqueous Zn-ion battery for the first time. This Na-Mn-O ternary system was prepared using two-step emulsion-based synthesis. The phase-pure Na2Mn3O7 was formed in a triclinic structure with a space group of P-1. It exhibited versatile electrochemical insertion of different ions like Li-, Na- and K-ions involving phase transition. Na2Mn3O7 exhibited reversible Zn-ion intercalation delivering capacity of 245 mA h g-1 with a nominal voltage of 1.5 V. Upon discharge, it triggered phase transformation to an unknown phase. Layered Na2Mn3O7 oxide was found to act as an efficient cathode for Zn-ion batteries with good cycling stability.

A preliminary study on ochre sources in Southwestern Germany and its potential for ochre provenance during the Upper Paleolithic

The use of mineral pigments, specifically iron-oxide rich mineral pigments called ochre, has been put forward as a key element in the development of symbolic and non-utilitarian behaviors in human evolution. However, the processes of ochre procurement, trade and use are difficult to conceptualize without the identification and characterization of the sources where these materials were acquired. We present the results of geochemical analyses of ochre source samples collected from the Swabian Jura, Black Forest, and other localities in southern and eastern Germany. The goal of this study was to build the groundwork for future investigations on the range of ochre behaviors at archaeological sites in the region. We aimed to determine whether specific ochre outcrops could be differentiated based on their geochemical signatures. Using data from Neutron Activation Analysis (NAA), we were able to determine that the ochre source regions exhibit greater source inter-variability than intra-variability when observed using a range of statistical techniques, therefore satisfying the provenance postulate. Furthermore, the data provide the foundation for a Central European database of ochre sources to allow the comparison of ochres from different regions to archaeological ochres from important nearby and perhaps distant sites.

Drained organic soils under agriculture — The more degraded the soil the higher the specific basal respiration

Drained peatlands are hotspots of carbon dioxide (CO2) emissions from agricultural soils. As a consequence of both drainage-induced mineralisation and anthropogenic mixing with mineral soils, large areas of former peatlands under agricultural use underwent a secondary transformation of the peat (e.g. formation of aggregates). These soils show contents of soil organic carbon (SOC) at the boundary between mineral and organic soils. However, the carbon (C) dynamics of such soils have rarely been studied so far. The aim of the present study was to evaluate the vulnerability of soil organic matter (SOM) to decomposition over the whole range of peat-derived soils under agriculture including very carbon rich mineral soils (76–526 g kg−1 SOC). A total of 62 soil samples covering a broad range of soil and site characteristics were selected from the sample set of the German Agricultural Soil Inventory. Potential CO2 production was measured by aerobic incubation. Fen and bog peat samples were grouped into disturbance classes according to their soil properties. Specific basal respiration rates (SBR), i.e. CO2 fluxes per unit SOC, showed the highest values for the most disturbed samples for both fen peat (13.9 ± 6.0 μg CO2-C g SOC−1 h−1) and bog peat (10.9 ± 4.7 μg CO2-C g SOC−1 h−1). Respiration rates of bog peat increased more strongly with an increasing degree of disturbance than those of fen peat. Perhaps counterintuitively, SOM vulnerability to decomposition thus increased with an increasing degree of disturbance and a decreasing SOC content, indicating positive feedback mechanisms as soon as peat soils are disturbed by drainage. Furthermore, the variability of the SBR increased drastically with increasing degree of disturbance. The turnover of SOM in less disturbed peat samples tended to be higher in samples with higher nitrogen (N) content, higher pH value and lower C:N ratio, while plant-available phosphorus was important for the mineralisation of more severely disturbed peat. However, clear correlations between a single soil property and SBR could not be identified. The high potential of CO2 emissions from organic soils with a low SOC content implies that mixing organic soil with mineral soil does not seem to be a promising option for mitigating greenhouse emissions.

Biomineralization Pathways in Calcifying Dinoflagellates: Uptake, Storage in MgCaP-Rich Bodies and Formation of the Shell

Little is known about the formation of the shells of calcareous dinoflagellates, despite the fact that they are one of the major calcifying organisms of the phytoplankton. Here, we investigate calcitic cyst formation in two representative members from different clades of calcareous dinoflagellates using cryo-electron microscopy (cryo-SEM and cryo-FIB-SEM) in combination with micro-Raman and infrared spectroscopy.Only calcein-AM and not calcein enters these cells, indicating active uptake of calcium and other divalent cations. Multifunctional vacuoles containing crystalline inclusions are observed in both species and we identify the crystals as anhydrous guanine in the β-form. We also observe in the same vacuolar enclosures, dense magnesium, calcium and phosphorous rich mineral bodies by cryo EDX. These bodies are secreted into the outer matrix space where calcite forms. Calcite formation occurs via multiple independent nucleation events and the different crystals grow with preferred orientation into a dense reticular network that forms the calcitic cyst. The degree of atomic order of this calcite is less than that of geological calcite. We suggest a common biomineralization pathway for these two calcifying dinoflagellates: (1) Uptake of calcium and other cations through the membranes. (2) Deposition of Mg2+ and Ca2+ ions inside a disordered MgCaP-body. (3) Secretion of these bodies to the space between the outer membranes. (4) Formation and growth of calcite bodies into a dense reticulate network that forms the mature calcitic shell. This study provides new insights into calcium uptake, storage and transport in calcifying dinoflagellates.

City Profile: Panzhihua, China

Located in the upper reaches of the Yangtze River in Sichuan Province of southwest China, Panzhihua, a prefectural-level city, was the first Special Zone selected for resource development in China after 1949. This Special Zone city has been developed based on its rich mineral resources. After more than 60 years of struggle, Panzhihua has been transformed from an industrial city dominated by mineral resource–related industries into a diversified economy. This article traces the historical development of Panzhihua and examines how various versions of urban planning have been employed as effective tools to reshape the city’s built environment to promote economic growth. It also discusses the latest efforts undertaken by the City Government of Panzhihua for industrial transformation and economic growth against the background of global economic recession and local resource exhaustion. The lessons and experiences learnt from the case of Panzhihua city serve as lessons for other resource-reliant cities trapped in the middle of urban transition towards sustainable development.

Computation of Temporal Decline to a Vanished Island (A Case Study Zalzala Koh)

A massive tremor stuck Baluchistan Pakistan on September 24, 2013 with a magnitude of 7.7 recorded on Richter scale. The epicenter was Awaran Baluchistan which directly affected about 300,000 people leaving about 386 causalities. The impact of this earthquake was so much large that it created a new landmass which was named as Zalzala Koh later. It was the result of strike slip faulting at a depth of 15km. The new born island was full of rich minerals, gases and dead sea animals. This island was 60 feet high, 100 feet wide and 250 feet long. The classification results of Landsat 8 show that the island completely disappeared in 2019 after 6 six years of its birth. First the volume of this island decreases due to reduced pressure of internal gases and secondly, the high-pressure water waves vanished it completely. Satellite imagery proved efficient for spatio-temporal monitoring of various landuse classes.

Discussion on Guangzhou-Enping Fault Based on Gravity and Deep Seismic Data

In this paper, the gravity and magnetic data and the preliminary results of the interpretation of the artificial seismic depth sounding in the Pearl River Estuary are combined with the geological data for the discussion of the most important northeast fault in the Pearl River Delta region in terms of the characteristics of deep strata of Guangzhou-Enping fault. It is believed that the Guangzhou-Enping fault is an NE-trending deep fault with a cutting depth of more than 30km, a depth of Moho, a steep dip, and the largest extent in the Pearl River Delta, and has a certain cut with the near EW-oriented fault. Therefore, the Guangzhou-Enping fault is active to some extent which provides a channel for deep material upwelling. The deep flow of molten material is the main component of the low-velocity zone of the lower and middle crust, and the surface is characterized by rich mineral resources, hot springs and basalt exposure.

Computation of Temporal Decline to a Vanished Island A Case Study Zalzal Koh

A massive tremor stuck Baluchistan Pakistan on September 24, 2013 with a magnitude of 7.7 recorded on Richter scale. The epicenter was Awaran Baluchistan which directly affected about 300,000 people leaving about 386 causalities. The impact of this earthquake was so much large that it created a new landmass which was named as Zalzala Koh later. It was the result of strike slip faulting at a depth of 15km. The new born island was full of rich minerals, gases and dead sea animals. This island was 60 feet high, 100 feet wide and 250 feet long. The classification results of Landsat 8 show that the island completely disappeared in 2019 after 6 six years of its birth. First the volume of this island decreases due to reduced pressure of internal gases and secondly, the high-pressure water waves vanished it completely. Satellite imagery proved efficient for spatio-temporal monitoring of various landuse classes.

Characterization of quality and pharmacological assessment of Pimpinella anisum L. (Anise) seeds cultivars

Pimpinella anisum L. seeds of the two cultivars were assessed for their nutritional quality and safety assessment through proximate, chemical and pharmacological studies. The proximate composition along with rich mineral elements as well as minor level of toxic elements indicated the good quality of seeds. The GC–MS analyses of hydro distilled volatile oils of two cultivars contained 16 constituents. The main constituents in BSRC (Bangladesh Spice Research Centre) seeds were trans-anethole (83.67%), fenchone (5.29%) and 1,2-diisopropenylcyclobutane (6.31%) whereas, trans-anethole (69.94%), fenchone (11.184%) and d-limonene (13.007%) were the main constituents in local market seeds. The IC50 values of DPPH antioxidant activity showed at 48.71 and 52.48 mg/mL, in BSRC and local market seeds cultivars essential oils respectively. The antimicrobial activity of the essential oils showed moderate activity in both cultivars against Gram-positive, Gram-negative bacteria and fungi. Both oils had some similarity in physiochemical properties and antimicrobial activity. The brine shrimp cytotoxic activity of the essential oils exhibited weaker activity than the standard drug at 3.06 and 2.86 μg/mL (IC50) in BSRC and local market seed cultivars respectively. The present investigation demonstrated good nutritional quality with rich bioactive phytoconstituents as well as low level of toxic elements of anise seeds. The research findings can open up a new possibility for exportation of indigenously cultivated spices as well as recommendations for food and pharmaceutical industries.

The Role of Hydrothermal Activity in the Formation of Karst-Hosted Manganese Deposits of the Postmasburg Mn Field, Northern Cape Province, South Africa

The Postmasburg Manganese Field (PMF), Northern Cape Province, South Africa, once represented one of the largest sources of manganese ore worldwide. Two belts of manganese ore deposits have been distinguished in the PMF, namely the Western Belt of ferruginous manganese ores and the Eastern Belt of siliceous manganese ores. Prevailing models of ore formation in these two belts invoke karstification of manganese-rich dolomites and residual accumulation of manganese wad which later underwent diagenetic and low-grade metamorphic processes. For the most part, the role of hydrothermal processes and metasomatic alteration towards ore formation has not been adequately discussed. Here we report an abundance of common and some rare Al-, Na-, K- and Ba-bearing minerals, particularly aegirine, albite, microcline, banalsite, sérandite-pectolite, paragonite and natrolite in Mn ores of the PMF, indicative of hydrothermal influence. Enrichments in Na, K and/or Ba in the ores are generally on a percentage level for most samples analysed through bulk-rock techniques. The presence of As-rich tokyoite also suggests the presence of As and V in the hydrothermal fluid. The fluid was likely oxidized and alkaline in nature, akin to a mature basinal brine. Various replacement textures, particularly of Na- and K- rich minerals by Ba-bearing phases, suggest sequential deposition of gangue as well as ore-minerals from the hydrothermal fluid, with Ba phases being deposited at a later stage. The stratigraphic variability of the studied ores and their deviation from the strict classification of ferruginous and siliceous ores in the literature, suggests that a re-evaluation of genetic models is warranted. New Ar-Ar ages for K-feldspars suggest a late Neoproterozoic timing for hydrothermal activity. This corroborates previous geochronological evidence for regional hydrothermal activity that affected Mn ores at the PMF but also, possibly, the high-grade Mn ores of the Kalahari Manganese Field to the north. A revised, all-encompassing model for the development of the manganese deposits of the PMF is then proposed, whereby the source of metals is attributed to underlying carbonate rocks beyond the Reivilo Formation of the Campbellrand Subgroup. The main process by which metals are primarily accumulated is attributed to karstification of the dolomitic substrate. The overlying Asbestos Hills Subgroup banded iron formation (BIF) is suggested as a potential source of alkali metals, which also provides a mechanism for leaching of these BIFs to form high-grade residual iron ore deposits.

The Arctic region in the economic and geographical concept of Vladimir Dehn

The article discusses the views on the Arctic region of Russia expressed by V.E. Dehn (1867-1933), an outstanding Russian researcher in the field of economic geography who developed the theoretical background of this science and contributed to the organization of teaching economic geography in theuniversities of St.Petersburg (Leningrad).The analysis of the book collection created by V. Dehnin 1902 at the Economic Geography Department at St. Petersburg Polytechnic Institute which was regularly replenished with various publications on commodity science, railway engineering, aviation, statistics, geopolitics and other materialsenabled the authors to look into the «intellectual laboratory» of V. Dehn. In his assessments of the prospects for the Arctic region development, V. Dehn used the descriptions of sea polar expeditions, ethnographic surveys of the life of the aboriginal population, governmental reports and scientific reviews of the regional economy development, etc. Within the framework of sectoral economic and geographical concept, V. Dehn’s interest in the North region wasdue to the prospects for the development of forestry and timber industry in Russia. V. Dehnreferred to transport inaccessibility and low population density as the main obstacle for the economic development of the Arctic territories and Siberia. Hence, the researcher paid special attention to railway construction projects developed in the early twentieth century, considering them the primary factor in the colonization of the North. The historical development has shown that the colonization of the Arctic in the twentieth century was associated with the discovery of rich mineral deposits in the region and their industrial production. The researcher highlighted the global importance of the Northern Sea Route as a transport corridor.

Physical and Chemical Properties and Nutrient Composition of Pisha Sandstone Under Different Temperature and Ph Value

The Pisha sandstone is widely distributed and rich in mineral elements. It has caused widespread concern about how to turn the rich mineral elements contained in Pisha sandstone into an activation state that can be absorbed and utilized by plants. Meanwhile, it will be the focus of this paper that the effect of physical and chemical properties and nutrients of the Pisha sandstone under the various activation conditions, such as pH, temperature and salt solution. We take pH and temperature as examples, the changes of physical and chemical properties, the main nutrients and nutritional level evaluation of the treated Pisha sandstone were studied. The results show that the conductivity of the Pisha sandstone can be improved under acidic or alkaline conditions. The temperature is one of the main factors affecting the content of available phosphorus, organic matter and available potassium of the Pisha sandstone, while the total nitrogen content is little affected by pH and temperature. And the nutrient grade of the Pisha sandstone increases from very low to low Only at 50°C.

Nutritional quality assessment of different muscles derived from 15-year-old female emus (Dromaius novaehollandiae): Meat physicochemical traits and sensory scores

The emu (Dromaius novaehollandiae) is considered a versatile farm species whose main by-products are meat and oil. At present, there is lack of information on the value of the meat of laying females at the end of their reproductive cycle which hampers the development of a specific market. To fill this gap, the present research aimed at studying the mineral composition, fatty acid profile, cholesterol level, selected physicochemical parameters and sensory quality of the meat of laying females at the end of their reproductive life cycles was carried out. The study should extend the knowledge on the application of this type of meat in food products as well as the available nutritional information on the muscles of female emus slaughtered at the end of their reproductive lives. The research material consisted of eight females slaughtered at the age of 15 years, at the end of their reproductive period. Following exsanguination, plucking and evisceration, the carcasses were cooled at 4°C for 24 h. After this time, five muscles were separated from both halfs of the carcases. The results showed that meat from 15-year-old females is of satisfactory nutritional quality. The rich mineral composition, high protein content, and low intramuscular fat and cholesterol contents deserve special emphasis. For this reason, the meat can be recommended for formulating healthy diets for humans. Its trading development is therefore expectable.

Socio-economic Impact of Unsystematic Mine Closure: A case of Kolar Gold Fields

This paper aims to study the Socio-Economic impact of un-systematic mine closure on the community and the neighborhood which is completely dependent on the mining. The sudden closure of the mines will affect the community’s entire livelihood and has counter effect on health, employment, environment, population and economy. India as a developing nation with its rich minerals content contributes sufficient towards the economic growth of the mining industry but the livelihood of the mining workers and their family are always kept in high level of risk. The policies and acts to control un-planned mine closure and counter its effects on the community should be made strong by the government. Kolar Gold fields, Karnataka (KGF) which holds an history of 120 years of mining and second deepest mine in the world has been chosen for the study. It is one among of the mines in the country which experienced the un-systematic closure in 2001 and facing its effects due to mill tailings, land contamination and loss of employment till date. These issues and challenges faced by the people of KGF will be addressed and can be improved if the government, mining company and people shows their support and interest for reviving the town.

Some Laboratory Scale Tests on An Australian Coal Tailings Sample

As a country with rich mineral resources, Australia, is amongst the top five world's leading exporter of minerals. As such, coal tailings, one of the by-products of mineral exploration, pose ample challenge for its handling, management and disposal in tailings dams. These usually are encountered with high moisture content. In order to avert the risk of fluidization and associated failures of coal tailing dams, dewatering is necessary to be applied for reducing their water content. With this in mind, some laboratory experiments based on a local coal tailings sample has been presented in this manuscript. The coal tailing sample has been characterized by conducting the liquid limit test, plastic limit test and shrinkage limit test. Sieve analysis and hydrometer test have been conducted to establish the gradational property of the material. Modified compaction test and one-dimension consolidation test have been performed and the load-deformation response of the material is described in detail. Also, the vane shear test has been conducted to figure out the relationship between gravimetric moisture content and shear strength. Furthermore, hydraulic and volume change response of the sample subjected to changing moisture content have been studied through soil-water retention curve (SWRC) and soil shrinkage characteristic curve (SSCC).

Spatial distribution, source identification, and potential risk assessment of toxic contaminants in surface waters from Yulin, China.

The Yulin Energy and Chemical Industry Base is widely known for its rich mineral resources and multiple types of fossil-fuel-based chemical industries; nevertheless, information regarding the level of toxic contaminants in the surface waters is lacking in this area. Therefore, this study investigates the distributions, sources, and risks of various toxic contaminants, including heavy metals, organochlorine pesticides (OCPs), and polycyclic aromatic hydrocarbons (PAHs), from 35 sampling sites in eight rivers. The ΣHCH concentration ranged from 1.28 to 6.64ng/L with predominant β-HCH, and the ΣDDT concentration was less than 0.35ng/L. The OCPs were derived from the recent input of lindane, residual technical-grade HCHs, and DDTs. The soil type can affect the environmental fate of DDT, and p,p'-DDE was widespread in the sandy land and loess areas. p,p'-DDD was rarely detected in the Mu Us Sandy Land area. The calculated ratios of isomers indicated that petroleum was the major source of PAHs. OCP and PAH contamination in the surface waters posed potential risks at several sampling sites. Due to the impacts by industrial emissions, agricultural sources, and vehicular traffic, the distribution of contaminant concentrations in the surface waters exhibited a significant spatial relationship with the land use pattern in the study region according to the results of principal component analysis and cluster analysis.

Fumarolic incrustations at Kudryavy volcano (Kamchatka) as a guideline for high-temperature (>850 °C) extinct hydrothermal systems

Our knowledge of active magmatic hydrothermal system (or magmatic vapors) is largely related to the modeling of geochemical processes including heterogeneous equilibrium calculations with variable bulk composition, temperature or pressure. With the aim to constrain the characteristics of extinct hydrothermal systems it is necessary to look for petrogenic evidence in active ones. The Kudryavy volcano in the Kurile Islands (Russia) provides a unique natural laboratory to study the formation of fumarolic rocks from high temperature fluids (measured temperature for the fumaroles up to 940 °C). By studying the minerals chemistry and assemblages and by computing a thermodynamical modeling, we investigated the mineralogical evidence for such high-temperature. We confirm the documented occurrence of Ca-Fe rich minerals as isolated patches, veins or incrustation in cavities and their formation during the alteration of primary minerals. We describe and documented secondary Na-Al rich minerals (davyne, nepheline, sodalite) and their occurrence together with Ca-Fe minerals in cavities. We also documented the presence of Fe-wollastonite, a relatively rare mineral suggesting high-T formation and we observed assemblages including wollastonite + andradite + magnetite suggesting high-temperature decomposition of andradite. This natural laboratory provides a series of concordant petrologic evidences for high-temperature fumarolic rocks and offers guidelines for the study of ancient high temperature hydrothermal environments on Earth and other planets like Mars.

A multi-technique evaluation of hydrothermal hematite U[sbnd]Pb isotope systematics: Implications for ore deposit geochronology

Hematite (α-Fe2O3) is a common iron-oxide mineral known to incorporate U into its crystal lattice at up to wt% concentrations and has been previously used to date ore formation within iron-oxide copper gold and banded iron formation deposits. However, there has been no detailed evaluation of the potential challenges this novel mineral geochronometer may present for accurate temporal interpretation. We report a multi-technique UPb geochronological study comprising laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), sensitive high-resolution ion microprobe (SHRIMP) and the first isotope dilution-thermal ionization mass spectrometry (ID-TIMS) procedure and analyses using an in-situ grain micro-sampling technique. We assess intra- and inter-sample data reproducibility, and examine the compatibility of spatial and analytical resolutions to texturally and compositionally diverse samples.Five samples of hydrothermal, primary, oscillatory-zoned hematite were analysed from distinct lithologies throughout the ~1.59 Ga Olympic Dam Cu-U-Au-Ag deposit, with typical U concentrations ranging between ~20 and 1000 ppm. LA-ICP-MS mapping of isotope distributions across mm-sized grains allows pinpointing of U-rich and relatively U/Pb isotopically ‘homogeneous’ domains. Micro-domains were extracted via laser-cut square shaped trenches (100 × 100 μm). UPb datum range in complexity, with concordant age domains measured by ID-TIMS indicating that hematite can retain a near-closed UPb system over ~1.6 Ga, while also demonstrating that younger Pb-loss events may be recorded. Significant reverse discordance is common in the data, likely to be a real feature due to both internal decoupling and mobility of Pb within a single grain and UPb fractionation during microbeam analysis. These effects will obscure the interpretation of real ages for Proterozoic samples where non-zero age Pb-loss events occur, and restricts the evaluation of common Pb mixing components. As a result, microbeam analyses may be biased younger or older in terms of 207Pb/206Pb dates in samples with complex histories. Microbeam datum compare favourably with high precision ID-TIMS ages. Although reproducible ID-TIMS UPb dates were generally not obtained, in the best-case example, a 207Pb/206Pb weighted mean age of 1589.91 ± 0.91 Ma (MSWD = 1.3, n = 5), within 0.2% of the Olympic Dam granite host rock age (1593.87 ± 0.21 Ma) was generated. All five hematite samples dated by LA-ICP-MS and SHRIMP yield weighted mean 207Pb/206Pb dates within 2% of the host granite age after small degrees of data rejection. The results demonstrate that with careful sample petrography, screening and data interpretation, hematite can be considered a very useful UPb mineral geochronometer, with potential application to all U-bearing Fe-oxide rich mineral systems.

Tracing water-rock interaction in carbonate replacement deposits: A SIMS pyrite S-Pb isotope perspective from the Chinese Xinqiao system

Deciphering the sources of metals is a prerequisite to establishing genetic models of ore formation, and is of importance for developing exploration models. For most magmatic-hydrothermal deposits, non-magmatic sourced components (e.g., fluids, sulfur and metals) are suggested to have minor or negligible contributions. On the other hand, there is substantial evidence to indicate that external ore-forming components could be crucial for the mineralization of some magmatic-hydrothermal deposits. Here, we conduct a detailed pyrite sulfur and lead isotope study on the Xinqiao stratabound deposit, South China, with the aim of constraining the contributions of ore-forming components from sedimentary rocks and existing mineralization through water-rock interaction. Traditionally, the source of mineralization at Xinqiao is debated. For example, a Cretaceous magmatic-hydrothermal origin was proposed as the sole source of metals. In sharp contrast, a Carboniferous sedimentary sulfide layer as proto-ore, which was enriched later by the Cretaceous magmatic-hydrothermal fluids, is required in a remobilization model. Crystallized pyrite grains from the stratabound orebody (py1) have a δ34S value of 4.09 ± 1.42 ‰ (2 SD), which is similar to that of pyrite grains from the garnet bearing skarn ore (py3). Colloform pyrite ore, which is composed of fine-grained (∼500 nm) cubic pyrite grains (py2a), has a δ34S value of 0.20 ± 1.14 ‰. The sulfur isotope composition of pyrite grains from the sandstone hosted quartz-pyrite veins is bimodal with δ34S values of 3.28 ± 6.46 ‰ (py4a) and −11.87 ± 5.43 ‰ (py4b). The Pb isotope compositions (206/204Pb ≈ 18.5, 207/204Pb ≈ 15.5) of py1, py4a and py4b are broadly the same as that of K-feldspar from the Cretaceous Jitou diorite, while py2a are more radiogenic (206/204Pb ≈ 21.5, 207/204Pb ≈ 18). Our pyrite S and Pb isotope data show no support for the presence of a Carboniferous sedimentary sulfide layer as proto-ore, but instead suggest that leaching sulfur and metals from Permian shales and an unexposed mineralization through water-rock interaction is a vital mechanism for the mineralization at Xinqiao. In line with previous studies, contributions from the late Permian shales are complementary for the stratabound orebody, and recycling existing Mo-Au rich mineralization is key for the formation of sandstone hosted gold rich pyrite-quartz veins. The existing mineralization is not exposed yet, and should be considered in future mineral exploration. Limited sulfur isotope fractionation between py1, py2 and py3 (0–4 ‰) further indicates a relatively reducing condition during their formation, while significant lower sulfur isotope composition (δ34S = −12 ‰) of py4 could imply an oxidizing condition during its formation. Our study highlights that detailed in-situ sulfur and lead isotope analyses under robust geological and petrographic frameworks can tightly constrain the source of ore-forming components, yield insights into oxygen fugacity during ore formation, and offer clues for future mineral exploration.