Fe Deposits Research Articles

Improvement of tensile strength of cold sprayed Fe deposits via in-process powder preheating

Cold sprayed Fe deposits were manufactured with non-preheated and preheated powders, respectively. The microstructure of the deposits was characterized by electron backscattered diffraction. The tensile property of the deposits was then evaluated. The results show that the preheated Fe powder deforms more extensively than the non-preheated powder during cold spraying due to their thermal softening. The ultimate tensile strength of the deposits made with preheated powder approximately doubles to 109.42 ± 50.56 MPa due to the enhanced intersplat bonding. However, the deposits in both cases exhibit poor ductility. The increased dislocation density and the nano-sized oxides on the preheated powder surface are considered to be the cause of low ductility of the deposits fabricated with preheated powder.

Electrolysis energy efficiency of highly concentrated FeCl2 solutions for power-to-solid energy storage technology

An electrochemical cycle for the grid energy storage in the redox potential of Fe involves the electrolysis of a highly concentrated aqueous FeCl2 solution yielding solid iron deposits. For the high overall energy efficiency of the cycle, it is crucial to maximize the energy efficiency of the electrolysis process. Here we present a study of the influence of electrolysis parameters on the energy efficiency of such electrolysis, performed in an industrial-type electrolyzer. We studied the conductivity of the FeCl2 solution as a function of concentration and temperature and correlated it with the electrolysis energy efficiency. The deviation from the correlation indicated an important contribution from the conductivity of the ion-exchange membrane. Another important studied parameter was the applied current density. We quantitatively showed how the contribution of the resistance polarization increases with the current density, causing a decrease in overall energy efficiency. The highest energy efficiency of 89 ± 3% was achieved using 2.5 mol L−1 FeCl2 solution at 70 °C and a current density of 0.1 kA m−2. In terms of the energy input per Fe mass, this means 1.88 Wh g−1. The limiting energy input per mass of the Fe deposit was found to be 1.76 Wh g−1.Graphical abstract

Ferristatin II, an Iron Uptake Inhibitor, Exerts Neuroprotection against Traumatic Brain Injury via Suppressing Ferroptosis.

As a specific ferroptosis marker, transferrin receptor 1 (TfR1) expression is increased following traumatic brain injury (TBI), but the precise role of TfR1 in TBI-induced ferroptosis and neurodegeneration remains to be determined. To further identify more potent ferroptosis inhibitors and effective targets for treating TBI, our study aims at investigating the effects of TfR1 on ferroptosis in a mouse TBI model using ferristatin II (an iron uptake and TfR1 inhibitor). The effect of ferristatin II was first verified in the HT-22 cell line in vitro and showed antiferroptotic action when exposed to ferric citrate (FAC), which is in parallel with the results obtained from the positive controls, including deferoxamine (DFO) and liproxstatin-1 (Lip-1). In vivo, ferristatin II administration reduced the expression of TfR1 at 12 h after TBI, and immunofluorescence experiments further confirmed that this decreased TfR1-positive cells were neurons. Importantly, ferristatin II suppressed TBI-induced iron homeostatic imbalance by decreasing the content of Fe (III) and iron-positive deposits and reversed the expression of iron homeostasis-related proteins. Moreover, ferristatin II attenuated TBI-induced lipid peroxidation by reversing the expression of lipid peroxidative genes and proteins, as well as the increase in malondialdehyde (MDA) level following TBI. Finally, ferristatin II alleviated TBI-induced neuronal injury and neurodegeneration, as detected by staining with Nissl and Fluoro-Jade B, thereby exerting a neuroprotective effect. In summary, these data indicated that ferristatin II might be a potential strategy to restrain ferroptosis and develop novel therapeutic agents against TBI.

Textural and chemical evolution of magnetite from the Paleozoic Shuanglong Fe-Cu deposit: Implications for tracing ore-forming fluids

Abstract The Aqishan-Yamansu belt in Eastern Tianshan (NW China) hosts several important Fe and Fe-Cu deposits, the origin of which is the subject of considerable debate. The coexistence of various types of ore-forming fluids makes it difficult to distinguish the genesis of the Fe-Cu deposits. We present detailed textural and compositional data on magnetite from the Paleozoic Shuanglong Fe-Cu deposit to constrain the formation of iron oxides and the evolution of the ore-forming fluids and thus define the genesis of the Fe-Cu ores. Based on the mineral assemblages and crosscutting relationships of veins, two mineralization stages were established, including the early Fe mineralization and late Cu mineralization stage. Three types of magnetite, i.e., platy (MA), massive (MB), and granular (MC) magnetite occur in the Fe mineralization. Backscattered electron (BSE) images identified display oscillatory zoning in an early hematite and transformational mushketovite phase (MA-I), characterized by abundant porosity and inclusions, as well as two later generations, including an early dark (MA-II, MB-I, and MC-I) and later light magnetite (MA-III, MB-II, and MC-II). The MA-I has extremely high W contents and mostly displays as micro- and invisible scheelite inclusions, which were probably caused by the W expulsion during mushketovitization. The texture and composition of magnetite suggest that the later light magnetite formed via dissolution and reprecipitation of the precursor dark magnetite, and the temperature and oxygen fugacity of fluids decreased over time. Our study also shows the MB-II magnetite and coexisting chlorite display synchronous oscillatory zoning, with the calculated temperature from 444 to 212 °C. Such variations could indicate the incursion of external low-temperature fluids with high salinity, which can dissolve the primary dark magnetite. This study provides a good example of using magnetite to trace the complex evolution and multiple sources of ore-forming fluids.

Multiple-Stage Mineralization in the Huayangchuan U\u2212REE\u2212Mo\u2212Cu\u2212Fe Ore Belt of the Qinling Orogen, Central China: Geological and Re\u2212Os Geochronological Constraints

The Huayangchuan ore belt is located in the western segment of Xiaoqinling Orogen in the southern margin of the North China Craton (NCC), and hosts voluminous magmatism and significant U−REE−Mo−Cu−Fe polymetallic mineralization. However, geochronological framework of the various mineralization phases in this region is poorly understood. Here, we present new Re−Os isochron ages on magnetite from the Caotan Fe deposit (2 675 ± 410 Ma, MSWD = 0.55), and on pyrite from the Jialu REE deposit (2 127 ± 280 Ma, MSWD = 1.9) and Yuejiawa Cu deposit (418 ± 23 Ma, MSWD = 11.5), and Re−Os weighted average model age on pyrite from the Taoyuan Mo−U deposit (235 ± 14 Ma, MSWD = 0.17). These ages, combined with regional geology and mineralization ages from other deposits, suggest that mineralization in the Huayangchuan ore belt lasted from the Neoarchean to the Late Mesozoic. The mineralization corresponds to regional tectono-magmatic events, including the Neoar-chean alkali magmatism (REE mineralization), Paleoproterozoic plagioclase-amphibolite emplacement (Fe mineralization), Paleoproterozoic pegmatite magmatism (U mineralization), Paleozoic Shangdan oceanic slab subduction-related arc magmatism (Cu mineralization), Early Mesozoic Paleo-Tethys Ocean subduction-related arc magmatism (Mo−U mineralization), and Late Mesozoic Paleo-Pacific oceanic plate subduction direction change-related Mo(-Pb) mineralization. We proposed that the Huayang-chuan ore belt has undergone prolonged metallogenic evolution, and the magmatism and associated mineralization were controlled by regional geodynamic events.

Origin of the subduction-related Late Carboniferous dacitic tuffs associated with the Bailingshan Fe deposit in Eastern Tianshan, NW China: Geochronological, geochemical, and Sr-Nd-Hf-O isotopic constraints

The Bailingshan deposit is an economically important Fe deposit in Eastern Tianshan, located in the southern margin of the Central Asian Orogenic Belt, Xinjiang, northwest China. The orebodies at Bailingshan are mainly hosted in the Carboniferous volcanic rocks. In this study, new secondary ion mass spectrometry (SIMS) zircon U-Pb dating, whole rock geochemistry, zircon Hf-O isotopic analyses and Sr-Nd isotopic analyses were carried out on the Bailingshan dacitic tuff. New SIMS zircon U-Pb dating results indicate that the dacitic tuff occurred in the Late Carboniferous (312.1 ± 3.3 Ma and 312.4 ± 4.4 Ma). The geochemistry of the dacitic tuff is consistent with calc-alkaline arc magmatism, characterized by high SiO2 (70.33–74.70 wt%) and (La/Yb)N values of 1.06 to 3.47. In addition, the Bailingshan dacitic tuff displays variable εHf(t) values (+8.2 to + 14.1), low δ18O values (4.70 to 6.35 ‰), high Mg# values (30–59), together with relatively uniform εNd(t) values from + 2.1 to + 5.8 and (87Sr/86Sr)i ratios ranging from 0.703818 to 0.707168, suggesting a fractional crystallization dominated origination from melting of a juvenile lower crust that mixed with the depleted mantle materials was most likely responsible for genesis of the Bailingshan dacitic tuffs. Combined with regional tectonic evolution and our new data, we infer that the change of subduction angle led to the rupture of magma chamber and the release of the Fe-rich fluids from magma chamber, causing the iron mineralization and relevant alteration of Bailingshan deposit in the Aqishan-Yanmansu arc.

Review on geology and mineralization of North Korea (II: Phanerozoic)

AbstractIn this review, we attempted to summarize and interpret the Phanerozoic geology and mineralization following the article (vol. 71 in Resource Geology) which reviewed the Precambrian geology and mineralization of North Korea. The basement of the Korean peninsula was built during the Precambrian and gradually became more evolved and complex during the Phanerozoic. The northern part of the peninsula was in the active and passive continental margins of the Korea–China platform during the Phanerozoic. In the tectonic environments of the Phanerozoic, the tectonic provinces of North Korea comprise several Paleozoic–Mesozoic intracontinental and rift basins as well as Cenozoic ocean border and rift basins. During the Paleozoic, the sedimentary strata were formed within the marine‐to‐nonmarine intracontinental basins, such as the largest Pyeongnam and Hyesan–Iwon basin, Imjingang rift basin, and several small structural basins, and the sedimentary type of limestone, dolomite, and coal deposits were formed. Mesozoic orogenic events in the peninsula were the most overwhelming geologic event causing block movements through collision and subduction of the paleo‐Pacific plate. Songrim orogeny (late Permian to early Triassic) might be caused by continental collision associated with strong deformation, metamorphism, and granite intrusion. Daebo orogeny (Jurassic) resumed the crustal deformation under a contractional setting during the subduction and caused dextral ductile shearing, magmatism, and metamorphism in the entire peninsula. Amnokgang orogeny, corresponding to Bulguksa orogeny in South Korea, during the Cretaceous formed several pull‐apart or transtensional basins probably because of oblique subduction of the Izanagi plate, and nonmarine sedimentary and pyroclastic sequences were deposited in the basin. The mineralization related to the Mesozoic plutonism was the most dominant in the peninsula. The considerable mineral deposits are ultramafic related magmatic Ni deposits owing to rift magmatism and granite related hydrothermal Au–Ag, Cu, Pb–Zn, Fe, W, and Mo deposits caused by the subduction of paleo‐Pacific plate. During the Tertiary, several structural basins under the extensional regime were overprinted on the Mesozoic basins in the northern part of the peninsula. They contain marine and nonmarine sedimentary rocks and felsic–mafic extrusives. Some sedimentary deposits, such as coal, kaolin, bentonite, diatomite, and zeolite, were formed. The Tertiary Pohang basin in South Korea shows basin geology, magmatism, and mineralization similar to those of North Korea. The Phanerozoic geotectonics of the peninsula are characterized by the evolution of the structural basins and violent magmatism. The peninsula is located on the Amur plate, bounded by the Philippine plate, Pacific plate, and Eurasian plate. Since Phanerozoic, the peninsula's geographic position created an important tectonic link between northeastern China and the Japanese Islands throughout geotectonic evolution.

Combining Δ18o Isotope Data and In-Situ La-Icp-Ms Trace Element Analysis of Magnetite as a Proxy for Ore Genesis: Constraints on the Formation of Fe Deposits from Ossa-Morena Zone (Sw Iberian Peninsula)

Combining Δ18o Isotope Data and In-Situ La-Icp-Ms Trace Element Analysis of Magnetite as a Proxy for Ore Genesis: Constraints on the Formation of Fe Deposits from Ossa-Morena Zone (Sw Iberian Peninsula)

Zircon U-Pb and molybdenite Re-Os geochronology and geochemistry of the Tieling deposit in the Eastern Tianshan, NW China: Insights into the timing of mineralization and tectonic setting

The Aqishan-Yamansu belt in the Eastern Tianshan (NW China) contains many Carboniferous granitic intrusive rocks and volcanic rocks and hosts numerous large to medium sized Fe (-Cu) deposits. The Tieling deposit consisting of 89 iron ore bodies in the Aqishan-Yamansu belt has been mined since discovered in 1970 s. Mo mineralization was newly identified in concealed rocks of the Tieling deposit, and molybdenite is extensively distributed as a disseminated phase in the biotite moyite and occurs as aggregates in quartz veins. The molybdenite Re-Os model ages (300.6 ∼ 298.7 Ma) are consistent with the zircon U-Pb age (304.5 ± 2.4 Ma) of the ore-causative biotite moyite within error, which indicating that the Tieling Mo mineralization occurred during the Late Carboniferous. The Late Carboniferous biotite moyite exhibits calc-alkaline and peraluminous characteristics, with negligible Eu anomalies, akin to I-type granites. Dominantly positive εHf(t) values (+13.6 to + 15.2), variable Mg# values (31 to 49), and limited variation in (87Sr/86Sr)i ratios (ISr = 0.70358–0.70390), and positive εNd(t) values (+4.55 to 6.39), along with the juvenile TDM2 age (548 to 697 Ma), suggest that the biotite moyite was probably originated from partial melting of the juvenile lower crust with involvement of mantle-derived magmas. Integrating published data and our work, we conclude that the Aqishan-Yamansu belt evolved from the pre- Early Carboniferous forearc basin (ca. 450–350 Ma) to the Carboniferous island arc environment (ca. 350–310 Ma) triggered by the bidirectional subduction of the Kanggur Ocean, then the extensional geodynamic setting (ca. 310–270 Ma) is conducive to the porphyry Mo mineralization of the Tieling deposit and Ni-Cu-Au deposits in the Eastern Tianshan.

Garnet and titanite U–Pb dating of the Kaladawan Fe–Mo orefield in the Altyn Mountains, NW China: Constrains for ore genesis

The Kaladawan Fe–Mo orefield is located in the east of the Altyn Mountains, NW China. It contains six Fe(–Mo) deposits, with total reserves of 60 Mt Fe and 10 kt Mo by-product. Mineralization is hosted in the contact zone between Early Paleozoic volcanic–sedimentary rocks and Ordovician granite, with intense and pervasive skarn alteration. Skarns exhibit some stratabound features. These deposits were variably classified as sedimentary-type with hydrothermal overprints, submarine volcanogenic iron-oxide- (SVIO-) type or skarn-type, centered on whether they are syngenetic or epigenetic. Titanite and garnet from skarn in the ore field are newly U–Pb dated to be ca. 482.6–481.0 Ma, consistent with the intrusive age of the granite but later than the formation age of the host rocks. These age data also further support that mineralization in the Kaladawan orefield is skarn-type.

In situ trace elements of magnetite in the Bayan Obo REE-Nb-Fe deposit: Implications for the genesis of mesoproterozoic iron mineralization

The giant Bayan Obo REE deposit bears a large amount of iron resources as well. However, the genesis of iron mineralization is still highly controversial with limited research. In this study, new data of trace elements of magnetite from Bayan Obo ores, Eastern contact zone skarn and Heinaobao BIF are obtained by Laser ablation (LA) ICP-MS analyses, revealing the genesis of Bayan Obo iron resources through comparing study. The Bayan Obo deposit contains disseminated, banded and massive ores, and in which magnetite is associated with REE minerals, fluorite, aegirine, riebeckite, and biotite. Euhedral magnetite in the skarn of Eastern contact zone is usually associated with pyrite, biotite, fluorite, and bastnaesite. There are two types of magnetite in the Heinaobao BIF: (1) euhedral to subhedral magnetite associated with quartz and a small amount of amphibole; (2) anhedral magnetite associated with quartz, garnet, plagioclase, amphibole and biotite.Magnetite in the Bayan Obo is enriched in Ni, but depleted in Mg, Al, Ti, Ge, Mn, Ga and Zn, showing low and variable concentrations, which is similar to the hydrothermal magnetite. The contents of some trace elements (e.g. Ti, Mn, Sc, Zn, Nb and REE) of magnetite from the skarn ores are generally higher, indicating a relatively high formation temperature. Magnetite in the Heinaobao BIF is generally characterized by low and uniform trace element contents, except for the abnormal values of Ti, Al, Cr and Mn, suggesting the involvement of terrigenous clastic materials. Compared with Bayan Obo magnetite, the skarn magnetite has the highest Sn/Ga, Co/Ni, Nb/Ta, La/Yb, Ti/V and Ti/Al ratios, while magnetite in the BIF has the highest Al/Co and lowest Nb/Ta ratios. The significant difference in mineralogical and trace element characteristics among the three types of magnetite indicates that the iron resources in Bayan Obo deposit are unlikely to be a skarn Fe deposit nor a BIF deposit. However, the Bayan Obo magnetite shows similar geochemical characteristics to hydrothermal magnetite related to carbonatite, both of which are depleted in high field strength elements, such as Zr, Hf and Ta, and show strong positive anomalies of Mn and Zn and negative anomalies of Co and Ga. In addition, in the diagrams of Ti vs. Nb + Ta and Ti vs. Zr + Hf, the Bayan Obo magnetite falls into the field of hydrothermal magnetite associated with carbonatite. In conclusion, it is recommended that the Bayan Obo iron deposit is a typical hydrothermal deposit related to carbonatite. In this contribution, the skarn magnetite formed at high temperature and the BIF magnetite was contaminated by terrigenous materials deviating from the expected region in discriminant diagrams. It is therefore proposed that the validity of these diagrams depends on a full understanding of mineralogical characteristics of samples and magnetite precipitation environment, and that multiple discrimination diagrams should be used in combination.

A gravity and magnetic study of lithospheric architecture and structures of South China with implications for the distribution of plutons and mineral systems of the main metallogenic belts

• 3D density and susceptibility models of South China were inverted by gravity and magnetic data. • Lithospheric structure such as Moho of South China has been calculated and interpreted. • 5 source zones as well as pathways of mineral systems are clearly revealed. • Termination sites of mineral system are uncovered by 3D density and susceptibility models. South China is characterized by enormous volumes of igneous rocks generated by multiple stages of magmatism. Five large-scale metallogenic belts with many world-class deposits have been discovered, demonstrating great potential for prospecting new resources. To restrict the South China metallogenic cognition the main problems include the types and metal associations of the deposits, factors controlling the distribution of the different types of metallogenic belts, and targets for new deposits. To find possible and feasible solutions to solve these problems. It is necessary to consider the metallogenic factors from the concept of mineral systems. This study first converted the satellite gravity into Bouguer gravity under spherical coordinates. Then the reduction-to-the pole (RTP) magnetic anomalies were obtained using a moving window with different geomagnetic parameters. The vertical lithospheric interfaces and main faults were inverted and interpreted according to these gravity and magnetic data. Based on the results obtained, we have discussed the possible sources and pathways of the five metallogenic belts in South China. Meanwhile, it identified the 3D spatial distribution of intrusions qualitatively by inverted susceptibility and density model, and predicted the potential sites for Cu, Fe, Au, W, and Sn deposits.

Electrochemical study of iron deposit in acid media for its recovery from spent pickling baths regeneration

• Fundamental study of iron electro-deposit from a model pickling bath carried out. • The effect of Fe 2+ concentration on electrochemical iron deposition was analyzed. • Tafel analysis showed redissolution of metallic Fe even at cathodic potentials. • Rotating disk electrode studies evidenced intermediate kinetics for the Fe deposit. • For Fe reduction electrolysis tests, the removal was until t = 400 s. Electrochemical technologies for the regeneration of spent pickling baths are feasible since they allow simultaneous metal deposition and acid production in the same process unit. In this work, the effect of Fe 2+ concentrations on the electrochemical iron deposition from aqueous model sulfate electrolytes (representing spent pickling baths) is analyzed by voltammetry switching potentials, Tafel analysis, and spectroelectrochemistry studies. The research showed that the electrodeposition rate and potential decreased as Fe 2+ concentration increased according to cyclic voltammetry tests. Moreover, at higher Fe 2+ concentrations, a decrease in the hydrogen evolution reaction was observed. Also, chemical Fe dissolution is present at all concentrations studied, due to the high corrosion rate of iron at the low pH of the model bath as was showed by voltammetry and Tafel plots analysis. Thermodynamic diagrams and electrochemical tests coupled to UV–VIS spectroelectrochemical analysis demonstrated the presence of iron sulfate complexes that are involved in the main electrochemical reaction.

Carboniferous high-Mg andesitic and dioritic rocks in the Aqishan-Yamansu belt: Implications for mantle metasomatism and tectonic setting of the Eastern Tianshan

The Aqishan-Yamansu belt, Eastern Tianshan is characterized by voluminous Late Paleozoic intermediate–felsic igneous rocks and magmatic–hydrothermal Fe (–Cu) deposits. This study presents zircon U–Pb ages and whole-rock geochemistry of newly identified high-Mg andesitic and dioritic rocks (HMAs and HMDs) within the Hongshanliang copper district in the Aqishan-Yamansu belt, Eastern Tianshan to investigate their petrogenesis and constrain the Carboniferous tectonic setting of the Eastern Tianshan. Zircon U–Pb dating of the HMAs and HMDs yielded ages between 336.9 ± 1.9 Ma and 329.0 ± 4.2 Ma. The HMAs and HMDs show calc-alkaline affinities, and exhibit weak Rb, Ba, U, and Pb enrichment and Nb and Ta depletion, with minor negative Eu anomalies. Moreover, the positive εNd(t) values (+6.4 to +6.6), low Th and (La/Sm)N contents/ratios, as well as relatively low and variable εHf(t) values (−3.71 to +1.55) indicate that they were probably sourced from a depleted mantle wedge with negligible to minor crustal contamination. They have low Ba/Th ratios (10.8–93.3), minor negative Eu anomalies, high and variable (La/Sm)N and Th/Yb ratios, which are comparable to the well-known sanukites of the Setouchi volcanic belt, suggesting involvement of sediment-derived magmas during their formation. Integrating published regional mafic–intermediate rocks from the Aqishan-Yamansu belt and this study, we propose that the Hongshanliang high-Mg rocks formed in a continental arc-related setting in the Carboniferous and the belt underwent a sharp tectonic transition event (ca. 330–322 Ma) from the Kangguer oceanic slab steepening to breakoff, corresponding to the Late Carboniferous basin inversion.

Review on geology and mineralization of North Korea (I: Precambrian)

AbstractIn this review, we introduce the geology and mineralization of the northern part of the Korean Peninsula based on recently published data in North Korea. Geological characteristics and events are described in order of geological period and the representative mineral deposits are presented according to the geologic period to show the relationship between the geology and mineralization. In particular, we rearrange the stratigraphy of the Precambrian basement and reset the timing of intrusion and mineralization based mainly on the reported zircon U–Pb age data. The Precambrian geotectonic provinces of North Korea contain continental cores and massifs, active continental margins, and rift zones. The Precambrian strata between the eastern North China Craton (NCC) and North Korea are newly correlated considering rearranged stratigraphy in this review. The Precambrian strata of North Korea are characterized by the depletion of the Paleoproterozoic to Mesoproterozoic strata compared to the NCC from 1.8 to 1.5 Ga. It may indicate that the northern part of the Korean Peninsula was the passive continental margin environment during this period. The common occurrences of bimodal igneous suites (mafic‐felsic and alkaline‐subalkaline) are also characteristic of North Korea. The bimodal magmatism is well explained by the progressive tectonic evolution from oceanic crust‐continent subduction (2.0–2.2 Ga) and island arc–continent collision (~1.9 Ga) to post collisional extension (1.82–1.87 Ga) in the NCC including North Korea. The Precambrian geological similarities between Northeastern China and North Korea would have resulted in the same or similar mineralization. For example, Algoma type banded iron formations of the Fe deposits of the Anshan–Benxi area in China and Musan Fe deposit in North Korea were formed during the Neoarchean and Paleoproterozoic. Sedimentary exhalative type Pb–Zn and metasedimentary type magnesite deposits were formed within the Jiao‐Liao‐Ji belt extending from the Liaoning Rift Zone of China (Pb–Zn deposits in the Qingchenzi orefield and magnesite deposits in Dashiqiao magnesite belt) to the Macheollyeong Rift Zone of North Korea (Geomdeok Pb–Zn deposit and Daeheung–Ryongyang magnesite deposits) during Paleoproterozoic. The geotectonic, geological and metallogenic similarities between Northeastern China and North Korea indicate that the Precambrian continental massifs of North Korea might be evolved in accordance with the NCC evolution. This review is expected to be helpful for understanding the geotectonics, geology, and related mineralization of the northern part of Korean Peninsula and correlating with those of the NCC.

Cryogenian glaciostatic and eustatic fluctuations and massive Marinoan-related deposition of Fe and Mn in the Urucum District, Brazil

Abstract Global Neoproterozoic glaciations are related to extreme environmental changes and the reprise of iron formation in the rock record. However, the lack of narrow age constraints on Cryogenian successions bearing iron-formation deposits prevents correlation and understanding of these deposits on a global scale. Our new multiproxy data reveal a long Cryogenian record for the Jacadigo Group (Urucum District, Brazil) spanning the Sturtian and Marinoan ice ages. Deposition of the basal sequence of the Urucum Formation was influenced by Sturtian continental glaciation and was followed by a transgressive interglacial record of >600 m of carbonates that terminates in a glacioeustatic unconformity. Overlying this, there are up to 500 m of shale and sandstone interpreted as coeval to global Marinoan glacial advance. Glacial outwash delta deposits at the top of the formation correlate with diamictite-filled paleovalleys and are covered by massive Fe and Mn deposits of the Santa Cruz Formation and local carbonate. This second transgression is related to Marinoan deglaciation. Detrital zircon provenance supports glaciostatic control on Cryogenian sedimentary yield at the margins of the Amazon craton. These findings reveal the sedimentary response to two marked events of glacioeustatic incision and transgression, culminating in massive banded iron deposition during the Marinoan cryochron.

Studying structural, magnetic and morphological features of electrochemically fabricated thin films of Co–Ni–Fe with different Fe compositions

In this work, a detailed study on the influence of the Fe composition on the crystallite size, lattice parameter, crystallographic texture, coercive field (Hc), magnetic squareness ratio (SQR), domain structure, surface roughness and grain size in electroplated Co–Ni–Fe deposits was carried out. For this aim, Co–Ni67, Co–Ni61–Fe6 and Co–Ni54–Fe13 thin films with different Fe compositions were fabricated using electrochemical deposition technique. The results showed that the composition of Fe in the deposit depends on the concentration of Fe ions in the electroplating solution. An increase in the Fe composition caused a noticeable reduction in the size of crystallites and induced a considerable enhancement in the strength of the preferred orientation being in the [111] direction. It was also observed that an increase in the Fe composition makes the lattice parameter larger. Compared to other deposits, the Co–Ni54–Fe13 with the highest Fe composition exhibited a lower surface roughness and a more compact nodular surface topography consisting of relatively finer grains. All deposits displayed a stripe domain (SD) structure, an in–plane magnetic hysteresis loop with a vertical magnetization component and a semi–hard magnetic property. However, the Hc value, SQR parameter and SD width varied in accordance with the Fe composition.

Geochemical and Fe-isotope characteristics of the largest Mesozoic skarn deposit in China: Implications for the mechanism of Fe skarn formation

Skarn deposits are major repositories of Fe and are the principal sources for iron mining in China. However, their mechanism of formation remains debated. Here we investigate the Xishimen (XSM) Fe deposit, located in Wu’an, China. This deposit is a well-known Mesozoic large skarn Fe deposits in the Han-Xing Fe metallogenic belt. Here we report the various features of this Fe deposit that suggest a clear magmatic affinity. We present data on the mineral assemblages, major and trace element data and Fe isotope analysis of magnetite from the XSM Fe deposit. Our results identify four distinct types of magnetite (Type I, II, III and IV). Magnetite type I is characterized by anhedral shape with vesicles in the ores, and is associated with diopside (Di), tremolite (Tr), ±garnet (Gt) and/or augite (Aug), together with phlogopite. Magnetite type I shows high content of TiO2 (0.25–1.21 wt%) and Al2O3 + MnO (0.24–0.72 wt%). These features suggest that magnetite type I is of magmatic origin. Magnetite type IV displays euhedral shape, and is associated with calcite, apatite and pyrite, and is enriched in SiO2, CaO, Sr, Ba, Rb, Nb, and total REE, and depleted in TiO2. These features suggest that magnetite type IV is of hydrothermal origin. The features of magnetite types II and III fall in between magnetite I and magnetite IV. The δ56Fe values are also distinct for the four types of magnetites: δ56Fe is the highest for type I magnetite (average 0.085‰); and the lowest for magnetite type IV (average 0.016‰). Our results also show that the δ56Fe value tends to be higher under high temperature environment and in lower part of the main orebody. Statistical analysis shows a negative correlation between the δ56Fe values and depth.With a view to constrain the origin of the skarn type Fe deposit, we present a conceptual model based on the geochemical and isotope data. We envisage distinct phases during the Fe ore genesis, including: (a) the formation of an iron-rich magma of dioritic composition which reacted with the carbonate wall rocks; (b) the iron-rich magma sinks into the bottom of the magma chamber with high density; (c) volatiles from deep magmatic chamber evolve and interact with the surrounding carbonate rocks; and (d) due to fluid overpressure in the chamber, the iron bearing melt and fluids migrate along structural conduits and precipitate the Fe ore. Because of the difference in temperature, pressure, and oxygen fugacity, the composition of magnetite varied along the fluid/melt conduits. Thus, magnetite type I (high Ti Mt) was mainly distributed in the lower part of the conduit, and magnetite IV (high Si Mt) was mainly concentrated in the upper part during progressive cooling in the conduit. Fe isotope fractionation occurred during the evolution of the Fe-bearing melt/fluid in response to changes in temperature and oxygen fugacity.

Igneous genesis of the Bayan Obo REE–Nb–Fe deposit: New petrographical and structural evidence from the H1–H9 cross-section and deep-drilling exploration

Rare earth elements (REEs) are a focus of global attention because of their unique properties and high-tech applications. Bayan Obo is the world's largest REE deposit and is hosted in the Paleoproterozoic Bayan Obo Group, Inner Mongolia. The REE resources are concentrated in unit H8, “dolomite marble.” However, whether unit H8 has an igneous or sedimentary origin is debated, and relationships among units H1–H9 are unclear, hindering our understanding of the formation of such a giant REE deposit. It was previously assumed that the unit H8 orebody is located in both limbs of the Bayan syncline and unit H9 in the core, which also needs to be confirmed because it is a guide for ore exploration. Field observations and petrographic studies of units H1–H9 were undertaken to re-evaluate the petrology and structure of the Bayan Obo Group. It was found that some units (e.g., H5–H7) are missing from the studied cross-section, with the two sides of unit H9, across the hinge of the so-called syncline, not being directly comparable. Unit H8 displays petrological, mineralogical, and whole-rock REE geochemical characteristics distinct from those of the other units investigated, suggesting they are of different origin. Moreover, deep-drilling exploration indicates major differences between the two limbs of the orebodies in terms of thickness, occurrence, and spatial distribution. The East orebody has a steep dip angle of 70°–80° and continuously extends to depth without reduction of angle, suggesting the syncline is probably nonexistent. These results, combined with the reported intrusion relationship of unit H8 with surrounding rock and in situ isotopic studies previously reported, indicate that the orebody is a carbonatitic igneous conduit rather than being of sedimentary origin. SHRIMP U–Pb dating of detrital zircons from the units H2–H9 yielded ages of 2574 ± 25 to 132 ± 2 Ma, overlapping the ages of units H1–H9 and the main REE mineralization periods reported previously. These protracted and complicated ages of the orebody likely represent fluid-aided resetting ages.

The high-grade Fe skarn deposit of Jinling, North China Craton: Insights into hydrothermal iron mineralization

Skarn-type Fe deposits constitute a major source of iron in the world, and 57% of the high-grade iron ores in China are hosted by skarn deposits. Most researchers agree that skarn-type Fe deposits are genetically linked with the associated magmas and precipitate from hydrothermal fluids, however, whether these ore-forming fluids are mainly derived from magmas or some other external sources is controversial. Besides, the detailed process of iron concentration in the high-grade ores in skarn Fe deposits has not been well constrained. To better understand these issues, we investigated the petrological, mineral chemical, geochronological, fluid inclusion and oxygen isotope characteristics of the Jinling Fe deposit, which is a typical high-grade skarn-type Fe deposit in the North China Craton. Zircon grains in these skarns were demonstrated to result from completely modification of magmatic zircons by the later hydrothermal fluids and they yield a weighted mean 206Pb/238U age of 126.7 ± 2.0 Ma (2σ) constraining the timing of the skarn iron formation, which is consistent with that of the ore-hosting Jinling complex. The similarity in chondrite-normalized REE patterns of the zircons in skarns and magmatic zircons suggests that the ore-forming hydrothermal fluids might mainly be derived from magmas. Additionally, the oxygen isotopes of the hydrothermal fluids in various stages as estimated based on δ18O values of representative hydrothermal minerals show relatively constant values during the evolution of hydrothermal system, suggesting that there was no significant involvement of external fluids. Three types of fluid inclusions, namely, high-salinity Type 1 with daughter minerals (homogenizing into liquid phase, with salinity of 42–71 wt% NaCl equivalent), vapor-rich Type 2 (homogenizing into vapor, with salinity ≤23 wt% NaCl equivalent), and relatively low-salinity Type 3 (homogenizing into liquid, with salinity ≤23 wt% NaCl equivalent) were identified in the various skarn minerals (garnet, clinopyroxene, epidote, and anhydrite). Among these, only Type 3 fluid inclusions occur in the clinopyroxene within the dominant massive ores, implying that the relatively low-salinity fluids were the predominant ore-forming hydrothermal fluids from which the magnetite ores precipitated. The high-salinity Type 1 fluids which might have resulted from phase separation (or boiling) of the primary magmatic hydrothermal fluids due to pressure drop, were believed to be responsible for the Fe-rich rims of zoned clinopyroxenes (with Fe-poor cores) in the thin magnetite-clinopyroxene interbedding layers between skarns and the massive magnetite orebodies. Thus, this zoned texture also implies an Fe re-enrichment event after formation of magnetite ores. The process of multiple Fe enrichment may significantly contribute to the formation of high-grade skarn-type Fe deposits.