Mineral Systems Research Articles

Lithospheric conductors reveal source regions of convergent margin mineral systems

The clean energy transition will require a vast increase in metal supply, yet new mineral deposit discoveries are declining, due in part to challenges associated with exploring under sedimentary and volcanic cover. Recently, several case studies have demonstrated links between lithospheric electrical conductors imaged using magnetotelluric (MT) data and mineral deposits, notably Iron Oxide Copper Gold (IOCG). Adoption of MT methods for exploration is therefore growing but the general applicability and relationship with many other deposit types remains untested. Here, we compile a global inventory of MT resistivity models from Australia, North and South America, and China and undertake the first quantitative assessment of the spatial association between conductors and three mineral deposit types commonly formed in convergent margin settings. We find that deposits formed early in an orogenic cycle such as volcanic hosted massive sulfide (VHMS) and copper porphyry deposits show weak to moderate correlations with conductors in the upper mantle. In contrast, deposits formed later in an orogenic cycle, such as orogenic gold, show strong correlations with mid-crustal conductors. These variations in resistivity response likely reflect mineralogical differences in the metal source regions of these mineral systems and suggest a metamorphic-fluid source for orogenic gold is significant. Our results indicate the resistivity structure of mineralized convergent margins strongly reflects late-stage processes and can be preserved for hundreds of millions of years. Discerning use of MT is therefore a powerful tool for mineral exploration.

Multiple Sulfur Isotope Compositions in Mesoarchean Sulfide Deposits of the Karelian Craton: Implications for Determining the Sulfur Source, Biogeochemical Processes, and Deposit Genesis

Abstract —In the present paper we demonstrate that most sulfides of the studied deposits of the Archean Sumozero–Kenozero greenstone belt within the Karelian Craton on the Fennoscandian Shield have nonzero Δ33S values. This indicates that proportions of seawater sulfate and elemental sulfur in Mesoarchean, included into the ores and resulting from UV photolysis, are different. Our results show that systematics of sulfur isotopes of sulfides generally reflects the mixing of mass-independently fractionated sulfur reservoirs with positive and negative Δ33S values. Pyrite is depleted in 34S isotope, which was interpreted as evidence for microbial sulfate reduction. Variations in the positive Δ33S anomalies of the Leksa deposit and the general tendency for Δ33S sulfide content to increase with stratigraphic levels in certain boreholes most likely reflect the change in temperature and the fluid mixing throughout the life of the hydrothermal system. The presence of sulfides with strongly negative Δ33S anomalies suggests that atmospheric sulfur and seawater sulfate, rather than volcanic sulfur, were the prevailing source for mineral systems of the studied deposits. The presented data require the Mesoarchean seawater to contain sulfates at least locally.

Investigation of Surface Charge at the Mineral/Brine Interface: Implications for Wettability Alteration

The reservoir rock ismade up of differentminerals which contribute to the overall formation wettability. These minerals in their natural state differ in chemistry and structure, and thus behave differently in an environment of varying composition and salinity. These have direct implications for enhanced oil recovery due to water flooding, or wettability alteration due to long-term exposure to brine. With the reservoir rock being a complex system of multiple minerals, the control of wettability alterations becomes difficult to manage. One of the dominant mechanisms responsible for wettability alteration is the mineral surface charge, which is dependent on pH, and fluid composition (salt type and salinity). For the first time, the surface charge development of barite, dolomite, and feldspar minerals in their native reservoir environments (accounting for the formation brine complexity) is presented. Also, the effect of oilfield operations (induced pH change) on minerals’ surface charge development is studied. This was achieved by using the zeta potential measurements. The zeta potential results show that barite and dolomite minerals possess positively charge surfaces in formation water and seawater, with feldspar having a near-zero surface charge. Furthermore, the surface charge development is controlled by the H+/OH− (pH), electrical double-layer effect, as well as ion adsorption on the mineral’s surfaces. These findings provide key insights into the role of fluid environment (pH, composition) and oilfield operations on mineral surface charge development. In addition, the results show that careful tuning of pH with seawater injection could serve as an operational strategy to control the mineral surface charge. This is important as negatively charged surfaces negate wettability alteration due to polar crude oil components. Also, the design of an ion-engineered fluid to control the surface charge of minerals was implemented, and the results show that reduction in the Ca2+ concentration holds the key to the surface charge modifications. Surface charge modifications as evidenced in this study play a critical role in the control of wettability alteration to enhance production.

The New Century for Nickel Resources, Reserves, and Mining: Reassessing the Sustainability of the Devil’s Metal

Abstract Nickel (Ni) is fundamentally important to the modern world for stainless steel, specialty alloys, electroplating, batteries, and other uses. Global Ni demand is expected to soar as the world transitions to a net-zero greenhouse gas emissions economy based on electric vehicles and energy storage batteries linked to renewable energy systems. This means that understanding the current Ni sector, especially known Ni resources, reserves, and mining (i.e., current and likely future sources of this metal), is crucial to enabling this energy transition, including the likely environmental, social, and governmental challenges that may prevent the development or may hinder the continuation of future and current Ni mining operations. This paper achieves this by presenting a comprehensive global assessment of reported Ni deposits and projects for the year 2018. All of these are classified by mineral deposit type to understand the relative importance of the different mineral systems that are mined for Ni and allocate each site a primary and secondary mineral deposit type. We also compare our results for 2018 with the results of a previous study focused on 2011 data to understand how deposits and projects have evolved over time and coincident with production. The majority of Ni has been and will continue to be sourced from laterites and magmatic sulfide systems; other deposits have produced only minor amounts of Ni. Our database indicates that globally some 627 Ni deposits remain with in-ground resources and/or reserves, including 148 and 86 laterite, 248 and 93 magmatic sulfide, 33 and 14 hydrothermal, and three and two tailings Ni-containing code-and noncode-compliant resources, respectively. Projects with reserve estimates include 38 laterite reserves, 70 magmatic sulfide, and three hydrothermal Ni-containing reserves. These data yield 350.2 million metric tonnes (Mt) of contained Ni in resources distributed as 190.2, 124.1, and 35.4 Mt Ni in laterite, magmatic sulfide, and hydrothermal resources, respectively. Reserves contain 47.12 Mt of Ni split into 25.97, 20.14, and 1.01 Mt Ni in laterite, magmatic sulfide, and hydrothermal reserves, respectively. Comparison of these data to 2011 data indicates that sulfide deposits are effectively keeping pace with depletion by mining, whereas laterite resources are lower than in 2011, perhaps reflecting the fact that the latter can be more comprehensively assessed during the early stage of laterite resource and reserve estimation. This suggests that although current resources are sufficient to enable current production to be sustained, the expected increase in demand for Ni may act to constrain supply. This may also be exacerbated by the increasing environmental, social, and governmental challenges facing the minerals industry globally, with a number of projects that have faced delays or problems associated with these challenges also outlined in this study. Our study also highlights the variable level of sustainability reporting undertaken by different companies involved in Ni mining and exploration. One potential approach to more effective environmental and social engagement would be improvements in this area, allowing more transparent engagement with social and environmental stakeholders. Overall, known Ni resources and reserves are sufficient to continue current levels of production for several decades to come (assuming all of this material can be mined); however, the Ni mining sector faces a number of challenges that may change this, including increased demand from electric vehicles and batteries and potential supply restrictions relating to increased environmental, social, and governmental challenges to the mining industry globally.

Maximizing drilling information in greenfields exploration: Linking the fabric and geochemical footprint of the basement to the surface in South Australia

Detection of mineral system footprints in regions under thick cover is challenging. The difficulties are enhanced in regions with low-relief landscapes that are deeply weathered. This research examines how information from a single drill hole in an underexplored region can deliver a significant amount of information to assist in greenfields exploration. This study describes the geochemical dispersion processes through >500 m of cover based on observations from drill hole CDP008, and explores the possibility of recognising landscape features that link basement features with the surface.Our study revealed that: (1) the lower fluvial sandstone package contains a geochemical footprint of the underlying basement rocks, produced by vertical and lateral geochemical dispersion; whereas (2) the overlying sediments do not record any footprint of the basement rocks; and (3) the top limestone units are a chemical barrier for vertical geochemical dispersion due to their lack of permeability.Basement features identified from magnetic data are mimicked by linear surface landscape features that lie above them, which may potentially be associated with vertical geochemical dispersion processes, linking the basement with the surface. Hence from the point of view of mineral exploration, surface geochemical sampling should target these particular neotectonic/reactivation-associated features of the landscape.We suggest that in areas of deep cover, neotectonics/reactivation surface landscape features have the highest prospectivity to detect deep basement geochemical signatures at surface. The findings from this study may therefore impact approaches to mineral exploration under cover in similar landscape contexts around the world, such as regions in West Africa, India, China and Brazil.

Early Devonian volcanic facies, central Lachlan Orogen, New South Wales: implications for tectonic and metallogenic models

The central Lachlan Orogen volcanic belt contains predominantly silicic and explosive eruptive products emplaced between ca 428 and 412 Ma within elongate basins over an area ∼350 km long and 20 km wide. The volcanic rocks are exposed in two parallel, south-southeast-trending belts between Cobar and Albury, NSW, and have S-, I- or A-type magmatic affinities. The southernmost sequences include subaerial rocks of the Gurragong Volcanics and Walleroobie Volcanics (herein renamed the Gurragong Group), and the newly described Culcairn Group. The Gurragong Group comprises crystal-rich Walleroobie Ignimbrite, lithic-rich Corella Ignimbrite, Mount Ariah Rhyolite coherent facies and newly recognised airfall Indarra Tuff. The Culcairn Group includes the Budginigi and Wallandoon ignimbrites. The Budginigi Ignimbrite includes crystal-rich ignimbrite, the Hadrells Hill Member hyaloclastite breccia and the Soldiers Quarry Member (coherent rhyodacite). The Wallandoon Ignimbrite is compositionally intermediate, metaluminous and amphibole-bearing. The volume estimate of southern pyroclastic units ranges from 15 to 75 km3 per succession. The northern volcanic sequences include the Canbelego-Mineral Hill Volcanic Belt, Mount Hope Group and Ural Volcanics, all deposited in a shallow- to deep-marine environment during the Cobar Basin opening. The subaerial depositional environment of the southern volcanic successions, the proximity of exposed Silurian granitoid, and contact metamorphic overprint of the Devonian volcanic successions by contemporaneous intrusions implies the volcanic pile was thicker, and synchronous uplift was occurring. Variation in the aluminium saturation index from peraluminous to metaluminous, and a variation in high-field-strength elements in the almost exclusively felsic igneous rocks may reflect variation in the source rocks and temperature of partial melting. The resulting metallogenic patterns reflect these basement differences. Metals in the south resulted in intrusion-related Sn–W; in the north, the marine environment proximity to a major transcrustal structure and variation in the fertility of the lower crustal rocks led to the development of diverse mineral systems. Key points The central Lachlan Orogen Siluro-Devonian volcanic belt is predominantly silicic, containing explosive eruptive products emplaced within a series of elongate basins between Cobar and Albury, NSW. The southernmost sequences, the Gurragong Group and the newly described Culcairn Group are subaerial; the northern sequences include the Canbelego-Mineral Hill Volcanic Belt, Mount Hope Group and Ural Volcanics and are wholly submarine. Variations in the igneous rock chemistry and regional mineralisation reflect the variation in the basement source rocks, related fertility and associated structures.

The Magmatic-Hydrothermal Ore-Forming Processes of the Tonggou Cu-Zn Deposit, NW China: Constraints from Magnetite Chemistry and Fluid Inclusions

The Tonggou deposit is a porphyry Cu and vein-type Cu-Zn mineralization system located in the Bogda Orogenic Belt, north of Eastern Tianshan. Systematic fluid inclusion analyses were performed on granular quartz from the magnetite–quartz stage and pyrite–chalcopyrite–quartz stage from the porphyry Cu mineralization. During the early stage of porphyry Cu mineralization, the ore-forming fluids were at high temperatures (450–501 °C) and high salinity (51.2–55.2 wt.% NaCl equiv.) H2O-NaCl hydrothermal fluids with fluid boiling. These fluids evolved to high temperature (412–450 °C) and intermediate to low salinity (8.3–14.2 wt.% NaCl equiv.) H2O-NaCl hydrothermal fluids during the pyrite–chalcopyrite–quartz stage. In addition, magnetite from the Tonggou deposit was studied as a marker for the ore-forming process evolution of porphyry and vein-type mineralization. Sampled magnetite can be divided into MagI (allotriomorphic magnetite from altered granodiorite), MagII (magnetite from altered granodiorite found in veinlets or as granular aggregates), MagIII (from the magnetite–quartz stage of porphyry mineralization), and MagIV (from the polymetallic sulfide–epidote–quartz stage of vein-type mineralization). Magnetite LA-ICP-MS data indicate a hydrothermal origin. The contents of Ti, Si, Al, and Ta are controlled by temperature, and these elements gradually decrease from MagI to MagIV. Moreover, fO2 has considerable influence on the substitution of Sn, V, and Mn in magnetite, and the contents of these elements generally decrease from MagI to MagIII—increasing only in MagIV. Indeed, high fO2 in the polymetallic sulfide–epidote–quartz stage (MagIV) of vein-type mineralization is shown by the presence of a replacement texture in ilmenite grains within hydrothermal magnetite. On the other hand, magnetite samples from the Tonggou deposit have relatively low Ti + V contents compared to other porphyry Cu deposits—plotting in the skarn field of the (Ti + V) vs. (Ca + Al + Mn) diagram—and shows negative correlations in the (Ti + V) vs. Sn diagram. These data indicate that the porphyry Cu mineralization at Tonggou formed at relatively lower fO2 conditions than the Tonggou vein-type mineralization and other typical porphyry Cu deposits. Finally, porphyry and vein-type mineralization at Tonggou are both sourced from the porphyry system, as a result of ore-forming fluid transfer to a different location.

Controls on the metallogenesis of the Lhasa–Mozugongka district, Gangdese Belt, Tibetan Plateau: Constraints on melt distribution and viscosity from the 3-D electrical structure of the lithosphere

Some of the largest and most significant Miocene porphyry copper systems in China are within the Gangdese metallogenic belt on the southern Tibetan Plateau. It has been recognized that the crustal architecture and rheology, derived from regional tectonic events, has direct implications for the evolution and transport of fluids and magmas, and thus for the metallogenesis and prospectivity. Using data from a magnetetolluric array, which intersects the Lhasa–Mozugongka district of the Gangdese metal belt, a 3-D electrical resistivity model was generated, with the goal of investigating the tectonic and rheological controls on the magmatic mineral system. The lithospheric temperature distribution was estimated by applying the Arrhenius equation to conductivity profiles generated from 1-D Monte-Carlo models of long-period magnetotelluric data. The conductivity of partial melts in the lower and middle crust (30–60 km depth) was estimated for local conditions by applying the experimentally-derived equation of X. Guo et al. (2018). Subsequently, we estimated the melt fraction required to explain the observed bulk resistivity in each part of the study area. Variations in the effective viscosity of the lower and middle crust were constrained by the electrical resistivity model by applying the empirical relation of Liu and Hasterock (2016). Beneath the Miocene Cu–Mo deposits in the Lhasa terrane, conductive features in the lower and middle crust are attributed to partial melt fractions of more than 5% and viscosity reductions of 1–2 orders of magnitude. These conductive features may represent the signatures of (ore-controlling) melt/fluid migration channels and deeper melt/fluid source regions in the form of extensive crustal reservoirs of partial melt. Based on the interpretations of the geophysical model, and other available geological and geochemical evidence, a model of the metallogenic dynamics of the Miocene porphyry Cu–Mo deposits is proposed. Overall, the study highlights the applicability of electromagnetic geophysical methods to reliably link resistivity structures to melt/fluid transport channels and sources within a mineral system and supports the hypothesis that crustal rheology exerts a major control on the distribution of ore deposits.

Influence of polysaccharides with different chemical character on stability of montmorillonite suspensions in the presence of pseudoamphoteric cocamidopropyl betaine

Mixtures of the cationic starch (CS), carboxymethyl cellulose (CMC) and guar gum (GG) with the pseudoamphoteric surfactant - cocamidopropyl betaine (CAPB) were used as stabilizers of aqueous suspensions of clay mineral (CM) of montmorillonite type (MMT). The spectrophotometric method (UV–VIS) was used in to estimate the mechanism of the polysaccharide/CAPB/MMT systems stabilization. Additionally, surface tension measurements were performed to investigate the interactions between the polymers and the surfactant and the complex formation. In order to obtain complete information about the studied systems: FT-IR, XRD, SEM as well as porosity measurements were also performed for polymer/clay mineral system as well as of those in the presence of surfactant. The results show that the MMT suspensions can be successfully stabilize using chosen polysaccharides (CS, CMC and GG) able to be adsorbed on the MMT surface. The best stability of the studied suspensions was obtained with a small concentration of polysaccharides (2 ppm) and a small amount of CAPB (0.04%). It seems that this surface active agent can be the ideal option for industrial applications because its small concentration ensures very large stability of the MMT/polysaccharide suspensions.

Ferromagnetism and exchange bias in compressed ilmenite-hematite solid solution as a source of planetary magnetic anomalies.

We propose a compressed ilmenite-hematite solid solution as a new potential source of Earth’s magnetic anomalies. The 0.5FeTiO3·0.5Fe2O3 solid solution compressed by collision synthesis with super-high-energy ball milling showed a decrease in molar volume of approximately 1.8%. Consequently, the sample showed a saturation magnetization of 1.5 ampere square meter per kilogram (Am2/kg) at 300 kelvin, a Curie temperature of 990 kelvin, and a magnetic exchange bias below 100 kelvin, e.g., 1.7 × 105 ampere per meter at 60 kelvin. Ilmenite-hematite solid solutions are common mineral systems in most mafic igneous and metamorphic rocks, and the compressive force in the rocks is generated by the high pressure in the upper mantle or by shock events with high pressure such as the collision of these rocks with meteorites. Therefore, we consider that the compressed ilmenite-hematite solid solution is an additional candidate source of other planetary magnetic anomalies including those in the Moon and Earth.

Cu–Au exploration target generation in the eastern Carajás Mineral Province using random forest and multi-class index overlay mapping

The Carajás Mineral Province (CMP) located in the southeast of the Amazon craton, northern Brazil is one of the most important provinces of the world hosting a high number of large-tonnage Cu–Au deposits. This potential is due to overprinted mineralization events dated from the Neoarchean to Paleoproterozoic, including VMS, IOCG, and Cu–Au granite-related systems. The discovery of a new mineral deposit is linked to direct detection methods that have an elevated cost. Mineral potential modeling is a multi-source geoscience data that can help outline high prospective areas, containing new mineral exploration targets in the order to reduce the exploration risk. This work employed one knowledge-based method, multi-class index overlay, and one machine-learning algorithm, random forest, to produce two mineral potential maps in a district scale for Cu–Au deposits in the easternmost CMP (Parauapebas area) using a mineral system-based approach. This approach consists of translating the critical ore-forming processes of the mineral system components (source of fluids, metals, and ligands, source of energy, pathways, ore deposition gradient) into spatial data (evidence maps). For this study, ten evidence maps were created using the Spatial Data Analyst in GIS, then for the multi-class index overlay, each evidence map received a weight according to its relevance in the modeling, and integrated through the Image Analyst Tools. For the random forest algorithm, meanwhile, the model was trained four times using the Orange Data Mining software. The performance of the models was measured through the classification of accuracy, ROC curve, AUC values, predictive and success-rate curves. Both models achieve good performance with classification accuracy and AUC values of 80% and 0,805 for the multi-class index overlay and values of 76,4% and 0,812 for the random forest. Although the models have similar performance, the analysis of the curves showed that the random forest model was able to predict 82% of the locations of the known deposits, selecting about 25% of the total study area, while the multi-class index overlay predicted 72% of the location of the known deposits over 35% of the study area. Furthermore, both models predicted less than 10% of the study area as highly prospective helping prioritize areas for research and follow-up copper and gold exploration activities.

Geochemical characterization of the Central Mineral Belt U ± Cu ± Mo ± V mineralization, Labrador, Canada: Application of unsupervised machine-learning for evaluation of IOCG and affiliated mineral potential

The Central Mineral Belt (CMB) in Labrador, Canada, hosts multiple U (±base ± precious metal) showings, prospects and deposits in metamorphosed and variably hydrothermally altered Neoarchean to Mesoproterozoic, igneous and sedimentary rocks. Previous work has recognized U mineralization locally associated with Fe-Ca and alkali metasomatism typical of metasomatic iron oxide and alkali-calcic alteration systems (IOAA) that host iron oxide-copper-gold (IOCG) and affiliated critical metal deposits. However, the type, extent and temporal or genetic relationships between the diverse Fe, Ca and alkali metasomatism and the regionally distributed U mineralization remains poorly understood.Combined unsupervised machine-learning and classification of alteration from a large geochemical dataset distinguish the main alteration phases in the CMB, identify compositional changes related to U mineralization, and infer lithological/mineralogical information from samples with censored (i.e., missing), limited and/or inaccurate metadata. Weak to intense Na and Na + Ca-Fe (Mg) metasomatism in the southwest (Two-Time and Moran Lake areas) and eastern (Michelin area) portions of the CMB pre-dates U mineralization and Fe-oxide breccia development, similar to albitite-hosted U and IOCG deposits globally.Rare earth elements and spider diagrams highlight both preservation and disruption of normally immobile elements. Principal component and cluster analysis indicate significant variations in Fe-Mg ± Na contents in the rocks from combinations of Na, Ca, Fe, and Mg-rich alteration, while protolith REE signatures can be locally preserved even after pervasive albitization-hematization. Cluster analysis identifies mineralized felsic and mafic rocks in the Michelin deposit and Moran Lake area, facilitating inference of relevant lithological/mineralogical information from samples lacking or with limited meta-data.The methods outlined provide rapid and relatively inexpensive means to optimize identification of mineral systems within large geochemical datasets, verify drill core or field observations, highlight potentially overlooked alteration, and refine economic mineral potential assessments. Based on our results and previous work, we suggest the mineral potential of the southwestern and eastern CMB needs to be re-assessed with modern exploration models for IOAA ore systems and their iron oxide-poor variants.

Genesis of orogenic gold systems in the Daduhe belt: Evidence of long-lived fertile mantle lithosphere as a source of diverse metallogeny on the western margin of the Yangtze Craton, China

The poorly documented Daduhe gold belt on the western margin of the Yangtze Craton, an important metallogenic belt in southwest China, is characterized by typical orogenic gold systems against a highly anomalous geodynamic setting. A synthesis of regional and deposit geology, mineralization ages, and S-O isotopic compositions of 33 gold deposits from the Danba-Kangding-Shimian-Mianning area of the belt reveals regional metallogenic patterns, establishes a consistent genetic model, and demonstrates a source equivalent to other diverse mineral systems on the western margin of the Yangtze Craton. The Daduhe orogenic gold deposits are controlled by the lithosphere-scale Xianshuihe and Anninghe strike-slip faults in the northern and southern segments of the belt, respectively. The alteration and ore mineral assemblages of the Daduhe orogenic gold deposits define a wide range of hypozonal, mesozonal, and epizonal sub-types. They formed during two episodes: 1) Early Jurassic gold mineralization related to closure of the Paleo-Tethys Ocean, with a large hypozonal gold deposit on the margin of the Danba dome in the northern segment; 2) Cenozoic gold mineralization associated with continental collision on the Tibetan Plateau, with small mesozonal and epizonal gold deposits in shear zones in migmatite basement and at contacts with cover sequences in both the northern and southern segments. At the belt and deposit scales, the ore-controlling structures for both mineralization episodes are NNE-trending second-order extensional faults or their intersections with the dominant NW-trending compressional faults. The three deposit sub-types have overlapping δ34S of 0 ∼ 10‰, δ18Ofluid of 6 ∼ 11‰, and low He-Ar isotope ratios, all consistent with derivation of ore fluids from metasomatized mantle lithosphere. Importantly, the Daduhe orogenic gold deposits have similar S-O-He-Ar isotope compositions to the giant IOCG, Cu-Ni-PGE, Fe-V-Ti, anomalous porphyry Cu-Mo-Au, and carbonatite-related REE deposits in the Panxi region on the shared margin of the western Yangtze Craton. This suggests that these diverse mineral systems have a common source of ore fluids and metals derived from fertile mantle lithosphere during different geodynamic and metallogenic events. Such a widespread hydrous metal-rich deep source with lithosphere-scale faults as ore fluid pathways, and a depth continuum of orogenic gold deposits in the Daduhe belt suggest a high prospectivity and a higher future gold endowment for the belt. This study adds to an increasing awareness of the diversity of mineral systems on specific craton margins globally.

The effect of crosslinking additives and molecular weight of starch depressants on pyrrhotite and pentlandite floatabilities

• Synthesized starches (paste starches and crosslinked starch) can depress hexagonal pyrrhotite and pentlandite at pH 9.2. • Paste starch with higher molecular weight and crosslinked starch showed a certain selectivity in a binary mineral system. • The presence of metal hydroxylate species on both minerals allowed their chemical interaction with starch groups according to surface analysis. • Crosslinking additives within starch structure promoted a mixed interaction with mineral surfaces via chemisorption and electrostatic attraction. Pentlandite is very important to the mining industry since it is the main source of metallic nickel. However, its separation from hexagonal pyrrhotite by froth flotation is challenging due to their similar floatabilities, and inefficiencies in this process generate environmental issues caused by emissions of sulfur oxide gases during the pyrometallurgy of nickel concentrates. Although successful, the current pyrrhotite depressant (diethylenetriamine - DETA) is also harmful to the environment which compels the research and development of non-toxic and biodegradable reagents such as polysaccharides. Therefore, three starch depressants for hexagonal pyrrhotite were used in this study. They include a paste starch with higher molecular weight (MW), a paste starch with lower molecular weight, and a crosslinked starch formed by mixing the lower MW paste starch and copper ions. We hypothesize that the presence of crosslinking additives such as copper provide a “driving” effect towards the gangue mineral. The performance of depressants was investigated in single and binary mineral systems. For single minerals, all depressants impacted hexagonal pyrrhotite and pentlandite flotation recovery. For the binary mineral systems, the higher MW paste starch and crosslinked starch showed an improved Ni separation efficiency of 90.5% and 85.6%, respectively, at an intermediate PIBX dosage (9.66x10 −6 M) compared to the lower MW paste starch (58.6%), demonstrating a certain selectivity. The choice of the most suitable starch depressant proved to be complex since both minerals were able to chemically interact with the starch depressants as verified via X-ray photoelectron spectroscopy (XPS). Hydroxyl groups present on the α-D-glucose units bound with surface metal (Fe and/or Ni) hydroxylate species while the crosslinked starch also interacts with the mineral surfaces by electrostatic attraction. These findings will contribute to the advancement of knowledge related to the use of polysaccharides as depressants for complex sulfide mineral systems.

Genetic links of porphyry Mo-epithermal Pb–Zn–Ag mineralization system: a case study of the Shipingchuan polymetallic deposit, South China

Genetic links of porphyry Mo-epithermal Pb–Zn–Ag mineralization system: a case study of the Shipingchuan polymetallic deposit, South China

Trace elements in sulfide minerals from the Huangshaping copper-polymetallic deposit, Hunan, China: Ore genesis and element occurrence

The Huangshaping copper-polymetallic deposit, which is located in southern Hunan Province, China, is an important resource base for Pb–Zn minerals. This study used the major sulfides (sphalerite, pyrite, pyrrhotite), which formed during the Pb–Zn mineralization stage of the Huangshaping deposit, to determine the genesis of the Pb–Zn ore minerals and element occurrence. In-situ LA-ICP-MS analysis of minerals was conducted to determine their trace element concentrations and reveal the distribution and occurrence of trace elements in different sulfides. The formation temperature and genesis of the Pb–Zn ore minerals were also constrained based on the deposit geology and trace element data. Trace elements were significantly different among different sulfides in the Pb–Zn mineralization stage of the deposit. Sphalerite primarily enriches Mn, Cu, Ag, Sn, and Pb and is the main carrier mineral of Ga, In, and Cd. Pyrite relatively enriches Tl, Sb, W, and Se, and pyrrhotite primarily enriches Ge. In sphalerite, Fe, Mn, Cd, Ga, In, Cu, Sn, Ag, and Ge exist by substituting for other elements (such as Zn). The replacement method of Ge is Ge4++2Cu+↔3Zn2+, whereas that of In (Ga) is In3+(Ga3+) + Cu+↔2Zn2+. In pyrrhotite, Ge is incorporated through coupling substitution, and the abnormal concentrations of Pb, Ag, and Se are caused by galena that has replaced pyrrhotite. In pyrite, W occurs as a solid solution. When galena replaces pyrite, it causes abnormal concentrations of Pb, Tl, Sb, and Ag. The sphalerite is characterized by high concentrations of high-temperature ore-forming elements (e.g., Fe, Mn, In, and Sn) and relatively low concentrations of Cd, Ge, Ga, and other elements. Thus, the sphalerite was formed at a medium–high temperature (288–341 °C). The trace element characteristics of sphalerite are consistent with those of high-temperature hydrothermal deposits. The deposit geology, pyrite Co/Ni ratio (averaging 0.13, n = 29), S/Se ratio (averaging 173,905, n = 19), pyrrhotite Co/Ni ratio (averaging 0.10, n = 26), and binary diagram of trace elements in sphalerite indicate that Pb–Zn mineralization is related to the late-stage hydrothermal activity of skarn mineralization. The Pb–Zn mineralization and W–Mo(Fe) mineralization together constitute a skarn-type mineralization system.

Efficiency of mineral and organomineral fertiliser systems for column-like apple trees on sod-podzolic soil

Currently, biologized systems of land use and cultivation of agricultural crops based on the application of biological methods of plant protection, organic and organomineral fertilizer systems are becoming more widespread in various branches of crop production, including industrial horticulture. At present, in various fields of crop research, including industrial horticulture, biological land use and cropping systems based on biological plant protection methods, organic and organomineral fertiliser systems, have increasingly been used. The fertilisation of the column-like apple tree, dramatically different in its parameters and characteristics of physiological development from the apple tree with a conventional crown, has been insufficiently studied. The specific biological fertiliser systems for column-like apple trees should be developed. It is necessary to define doses, forms, periods, methods of mineral and organic fertiliser application into particular soil and weather conditions of cultivation, which will ensure stable fruiting of column-like varieties, high performance of plants, commercial and consumer qualities and environmental safety of fruits, beneficial for human health. The present work established the influence of mineral and organomineral fertiliser systems on plant performance and fruit quality of column-like apple-tree cultivated on sod-podzolic soils. The research objects included the Triumph, President, Valyuta and Ostankino column-like apple varieties, organic and mineral fertilisers. The research was carried out in 2016-2020 in the field agrochemical experiment at the Demonstration Garden of FSBSO ARHCBAN (Moscow region) on the sod-podzolic soil having medium loamy particle-size distribution. The experiment included 4 groups: 1) control without fertilisers, 2) N90K90, 3) 100 t/ha of organic fertilisers, 4) N90K90 + 100 t/ha organic fertilisers. Mineral fertilisers (Na, Kc) were applied annually; organic fertiliser (bedding horse manure and sawdust) was applied in 2014. The performance measurements, plant biometrics and analyses of plant samples were carried out following the standard methods. The influence of mineral and organomineral fertiliser systems on plant performance and fruit quality of column-like apple trees growing on sod-podzolic soil showed varietal specificity and diversity, depending on the variety. The Valyuta variety was more sensitive to mineral fertilisers (plant performance improved by 22.1 % over the unfertilised control) than organic fertilisers (plant performance decreased by 14.3 % compared to the reference). Although the President variety reacted positively to the application of organic fertiliser (plant performance increased by 22.5 %), the apple mass per plant in this variety decreased by 9.0 % when mineral fertiliser was applied. Furthermore, the co-application of an additional fertiliser (organic or mineral, respectively) for Valyuta and President varieties reduced the plant performance. The Triumph variety showed a weak sensitivity to various forms of fertilisers; upon their coapplication, the plant performance of this variety decreased by 12.4 % relative to the unfertilised control. The Ostankino variety characterised by the highest plant performance (up to 5.5 kg/plant) showed low sensitivity towards each fertiliser; under their co-application, the plant performance increased by 14.6 % relative to the control.

Ore-formation at the Halasheng Ag-Pb-Zn deposit, northeast Inner Mongolia as revealed by trace-element and sulfur isotope compositions of ore-related sulfides

The Early Cretaceous Halasheng Ag-Pb-Zn deposit in NE China, which is mainly hosted in Jurassic rhyolitic tuff, andesite, and volcanoclastic rocks, comprises both proximal skarns and more distal hydrothermal discordant ore veins and stockworks with associated Fe-Mn-carbonate, illite, and silica alteration in NNW-trending extensional faults. Suggestions of a magmatic-hydrothermal relationship are tested by LA-ICP-MS trace-element and sulfur isotope studies of ore minerals, particularly sphalerite which is a major ore mineral.Sphalerite has at least three types: SpS, anhedral, mainly dark red sphalerite in skarns; Sp1, euhedral, normally pale yellow coarse-grained, and rarely oscillatory zoned sphalerite formed in Stage 2 of hydrothermal vein mineralization; and Sp2, fine-grained, red, non-zoned sphalerite formed in Stage 3 of hydrothermal mineralization. Sphalerite with different textures has As, Ag, Cd, Sb, and Pb contents that increase from proximal skarn to distal hydrothermal mineralization consistent with the increase in sulfosalt minerals in the late hydrothermal stage. In situ time-resolved depth profiles, together with tangential profiles, and LA-ICP-MS element mapping of sphalerite indicate that trace elements are largely in solid solution in Halasheng sphalerite with substitution mechanisms including: Zn2+ ↔ Fe2+, Cd2+, Mn2+, and 3Zn2+↔ (As3+, Sb3+) + Ag++Pb2+. Enrichment of In and Sn, and depletion of Ga and Ge, together with In/Sn ratios indicate the high-temperature ore-forming fluids at Halasheng that are most likely closely related to intrusions. In situ mean δ34S values of SpS, Sp1, and Sp2 sphalerites are 5.3‰, 7.6‰, and 8.3‰, respectively, indicating that sulfur was derived both from magmatic-hydrothermal fluids and from wall rocks with higher (>10‰) values.These data help confirm that the Halasheng Ag-Pb-Zn deposit is an intrusion-related deposit with local proximal skarn mineralization at the contact of Tamulangou Formation andesite with Ergunahe Formation crystalline limestone, and more distal vein-type volcanic-hosted hydrothermal mineralization, with both ore and gangue mineral assemblages and available fluid inclusion data suggesting an intermediate-sulfidation epithermal association. As ore-forming hydrothermal fluids cooled and evolved they became enriched in silver, with silver-bearing sulfosalt minerals and silver-rich sphalerite precipitated in the latter stages of deposition.In terms of future exploration, there is potential for the concealed Lower Cretaceous Pb-Zn skarns and intermediate sulfidation Ag-Pb-Zn epithermal deposits at Halasheng to be part of a larger porphyry-related mineral system with porphyry Cu-Au-Mo deposits, similar to those of Middle Triassic to Early Jurassic age in the same metallogenic belt, at deeper crustal levels than the known deposits.

Petrogenesis of Late Cretaceous granites and implications for W-Sn mineralization in the Youjiang Basin, South China

Five Late Cretaceous tungsten-tin ore clusters (Gejiu, Dulong, Bainiuchang and Dachang tin deposits and Damingshan tungsten deposit) have been identified in the Youjiang Basin, South China. However, litter attention has been paid to such W-Sn metallogenetic specialization in the Youjiang Basin, as well as the geodynamic setting of mineralization and related magmatism. This study presents petrographical, geochronological, zircon Lu-Hf isotopic and whole-rock geochemical analyses for the Kunlunguan (KLG) biotite granites from the Damingshan ore cluster in the eastern part of the Youjiang Basin, and synthesizes previously published data from other ore clusters. The KLG granites yield crystallization ages of ∼ 100.2–98.6 Ma, and are characterized by high SiO2 and low A/CNK, Rb/Sr and 10000*Ga/Al, belonging to metaluminous to weakly peraluminous unfractionated I-type granite. The granites have initial 87Sr/86Sr ranging from 0.70919 to 0.71133 and εNd(t) from −9.3 to −6.8 with zircon εHf(t) ranging from −13.2 to −3.1, Eu/Eu* from 0.18 to 0.42 and Ce/Ce* from 7.43 to 254. Such signatures suggest that the KLG granites originated from partial melting of lower crustal mafic rocks with a minor mantle component. Overall, the W-Sn metallogenic specialization in the Youjiang Basin was first-order controlled by crustal sources of ore-host granites. The metallogenic age of the W-Sn deposits (∼97–75 Ma) is similar to the crystallization age of the granites (∼100–77 Ma), and the ages of mineralization and granites in the west of the Youjiang Basin are relatively younger than those in the east. The Late Cretaceous W-Sn mineralization system in the Youjiang Basin belongs to a part of an EW-trending Sn-W-Cu mineralization belt from Myanmar to Guangdong (South China), forming in an extensional setting caused by the Neo-Tethys oceanic slab roll-back.

Rare earth elements associated with carbonatite–alkaline complexes in western Rajasthan, India: exploration targeting at regional scale

Abstract. A two-stage fuzzy inference system (FIS) is applied to prospectivity modelling and exploration-target delineation for rare earth element (REE) deposits associated with carbonatite–alkaline complexes in the western part of the state of Rajasthan in India. The design of the FIS and selection of the input predictor map are guided by a generalised conceptual model of carbonatite–alkaline-complex-related REE mineral systems. In the first stage, three FISs are constructed to map the fertility and favourable geodynamic settings, favourable lithospheric architecture for fluid transportation and favourable shallow crustal (near-surface) emplacement architecture, respectively, for REE deposits in the study area. In the second stage, the outputs of the above FISs are integrated to map the prospectivity of REE deposits in the study area. Stochastic and systemic uncertainties in the output prospectivity maps are estimated to facilitate decision-making regarding the selection of exploration targets. The study led to the identification of prospective targets in the Kamthai–Sarnu-Dandeli and Mundwara regions, where detailed project-scale ground exploration is recommended. Low-confidence targets were identified in the Siwana ring complex region, north and northeast of Sarnu-Dandeli, south of Barmer, and south of Mundwara. Detailed geological mapping and geochemical sampling together with high-resolution magnetic and radiometric surveys are recommended in these areas to increase the level of confidence in the prospectivity of these targets before undertaking project-scale ground exploration. The prospectivity-analysis workflow presented in this paper can be applied to the delineation of exploration targets in geodynamically similar regions globally, such as Afar province (East Africa), Paraná–Etendeka (South America and Africa), Siberia (Russia), East European Craton–Kola (eastern Europe), Central Iapetus (North America, Greenland and the Baltic region) and the pan-superior province (North America).