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We investigated microfabrics of shocked Archean gneisses from two, 10 m-deep drill cores located near the center of the Vredefort impact structure in an area that is characterized by a prominent, long-wavelength negative magnetic anomaly (< − 3000 nT) together with short-wavelength, high-amplitude anomalies attributed to lightning strikes. Planar fractures and feather features in quartz, which can be partially recrystallized, indicate shock conditions less than 20 GPa. Micrometer-sized magnetite and ilmenite along shock-related shear fractures in quartz and feldspar emanate from adjacent deformed coarse (> 100 µm) ilmenite and magnetite host grains. These fine-scaled veins suggest mobilization of magnetite and ilmenite during shear deformation of host Fe-phases and adjacent silicates, probably associated with frictional heating. Coarse ilmenite has fine-lamellar mechanical twins parallel to {101¯1} and single (0001) twins, indicative of dislocation-glide-controlled deformation under non-isostatic stresses related to shock. A few µm-wide magnetite lamellae parallel to {101¯1} and spheroidal magnetite (diameter ≈10 µm) within coarse ilmenite document exsolution after shock. Dauphiné twins associated with planar features in quartz imply cooling from 650 to 725 °C after shock, which accords with estimates of pre-impact basement temperatures from petrographic studies. The Curie temperature of magnetite is 580 °C; therefore, the central negative magnetic anomaly was produced as a thermoremanent magnetization acquired during cooling of the initially hot crust. The long-wavelength anomaly was likely amplified by the newly created magnetite that also acquired a thermal remanence. Although the magnetic properties of surface samples are often influenced by lightning strikes, we found no microstructural evidence for lightning-related processes.

The removal of chromium-containing impurities, such as chrome spinel (ZCr2O4 where Z = Fe, Mg, Mn) from ilmenite (FeTiO3) concentrates through selective sulphidation, has been investigated by the authors. Laboratory experimental studies using sulphur added to ilmenite concentrates under Becher-type reduction conditions showed it is possible to selectively sulphidise chrome spinels from different ilmenite deposits. In this paper, processes to remove the sulphidised chrome spinels from the bulk ilmenite concentrates were investigated using flotation and magnetic separation techniques. Clustering or fusing of the reduced ilmenite (RI) and sulphidised chrome spinel grains was found to have a detrimental effect on flotation performance and made it difficult to have clear separation. A light wet grind was effective for breaking the clustering, but it caused the sulphide rim to spall off from chrome spinel surfaces, which reduces flotation efficiency. The preliminary results obtained after a magnetic separation (0.7 A) of a demetallised sulphidised RI sample show that the sulphidised chrome spinels preferentially report to the magnetic fraction. Additional magnetic separation of the non-magnetic fraction at a lower current (0.3 A) improved the recovery of sulphidised chrome spinels. The demetallisation process followed by a magnetic separation provided insights into a potential route for the removal of chrome spinels from reduced ilmenite concentrates. These two steps simulate the aeration stage of the Becher process. Further studies are required to optimise the process parameters.

Vein, stockwork, skarn, and carbonate-replacement Sn deposits commonly contain little or no Cu, but examples rich in Cu are also well known in many Sn belts worldwide. The origin of Sn-Cu deposits in association with fractionated and reduced, ilmenite-series granites of mostly metasedimentary crustal parentage is enigmatic because Cu, in contrast to Sn, normally accompanies oxidized, magnetite-series intrusions ultimately of mantle origin. Decompression mantle melting in back-arc or post-collisional settings generates mafic magmas, which are commonly invoked as the triggers for partial melting of thick overlying metasedimentary crust to form the fractionated, peraluminous, ilmenite-series magmas required to generate any associated Sn mineralization. Therefore, it is reasonable to suppose that oxidized fluids exsolved from these mafic magmas can contribute Cu to the synchronous and coexisting silicic chambers, thereby adding Cu to reduced Sn-bearing fluids and any resultant Sn deposits. Copper could also be released from Cu-bearing immiscible magmatic sulfides, formed during early crystallization of the reduced silicic magmas, as a result of either the introduction of these oxidized fluids and/or magma degassing. These putative mechanisms are restricted to thick metasedimentary crust, whereas in dominantly metaigneous crust the resultant magnetite-series magmas generate Cu deposits. This fundamental crustal influence on Sn versus Cu metallogeny of back-arc or post-collisional settings is responsible for both along- and across-strike transitions from the Central Andean Sn belt to regions displaying partly coeval Cu ± Au mineralization.

Mare volcanics on the Moon are the key record of thermo-chemical evolution throughout most of lunar history 1 – 3 . Young mare basalts—mainly distributed in a region rich in potassium, rare-earth elements and phosphorus (KREEP) in Oceanus Procellarum, called the Procellarum KREEP Terrane (PKT) 4 —were thought to be formed from KREEP-rich sources at depth 5 – 7 . However, this hypothesis has not been tested with young basalts from the PKT. Here we present a petrological and geochemical study of the basalt clasts from the PKT returned by the Chang’e-5 mission 8 . These two-billion-year-old basalts are the youngest lunar samples reported so far 9 . Bulk rock compositions have moderate titanium and high iron contents  with KREEP-like rare-earth-element and high thorium concentrations. However, strontium–neodymium isotopes indicate that these basalts were derived from a non-KREEP mantle source. To produce the high abundances of rare-earth elements and thorium, low-degree partial melting and extensive fractional crystallization are required. Our results indicate that the KREEP association may not be a prerequisite for young mare volcanism. Absolving the need to invoke heat-producing elements in their source implies a more sustained cooling history of the lunar interior to generate the Moon’s youngest melts. Isotopic analysis of basalt clasts returned from the Moon by the Chang’e-5 mission indicates that the rocks were derived from a mantle source that lacked potassium, rare-earth elements and phosphorus.

The distribution of water in the Moon’s interior carries implications for the origin of the Moon 1 , the crystallization of the lunar magma ocean 2 and the duration of lunar volcanism 2 . The Chang’e-5 mission returned some of the youngest mare basalt samples reported so far, dated at 2.0 billion years ago (Ga) 3 , from the northwestern Procellarum KREEP Terrane, providing a probe into the spatiotemporal evolution of lunar water. Here we report the water abundances and hydrogen isotope compositions of apatite and ilmenite-hosted melt inclusions from the Chang’e-5 basalts. We derive a maximum water abundance of 283 ± 22 μg g −1 and a deuterium/hydrogen ratio of (1.06 ± 0.25) × 10 – 4 for the parent magma. Accounting for low-degree partial melting of the depleted mantle followed by extensive magma fractional crystallization 4 , we estimate a maximum mantle water abundance of 1–5 μg g −1 , suggesting that the Moon’s youngest volcanism was not driven by abundant water in its mantle source. Such a modest water content for the Chang’e-5 basalt mantle source region is at the low end of the range estimated from mare basalts that erupted from around 4.0 Ga to 2.8 Ga (refs. 5 , 6 ), suggesting that the mantle source of the Chang’e-5 basalts had become dehydrated by 2.0 Ga through previous melt extraction from the Procellarum KREEP Terrane mantle during prolonged volcanic activity. Water abundance and hydrogen isotope compositions of two-billion-year-old basalt samples returned from the Moon by the Chang’e-5 mission suggest that the samples came from a relatively dry mantle source.

The pseudo-ilmenite structure ABO 3 have been increasingly highlighted in the optoelectronic area. Nanoparticles of undoped lithium niobates (LiNbO 3 ) and codoped with rare earths (LiNbO 3 : Dy 3+/ Tb 3+ ) were synthesized by the solid-state reaction method and calcined in a controlled way. The properties and structural changes of niobates were evaluated from data obtained in XRD and Rietveld refinement. The SEM-FEG micrographs showed different morphologies obtained (cubes, plates, tetrahedrons and polyhedra) according to the variation of the doping and co-doping process. Optical properties were measured and studied based on the results obtained from the UV-Vis spectrophotometer and photoluminescence assays. The photoluminescence presented by LiNbO 3 was associated with the existence of superficial defects in the particles, i.e., centers of recombination of photogenerated charges favorable to the property. The effect of concentration of dopants was investigated in properties photoluminescence. Photometric measurements (CRI, purity, CCT, LER) were analyzed and a modulation of the emitted color as a function of the concentration of the dopants. According to the obtained results, LiNbO 3 : Dy 3+ /Tb 3+ presents itself as a material with great potential in optical device applications. Graphical Abstract

Although ilmenite and rutile are extensively used to extract TiO2 at the industrial level, through the sulphate and chloride processes, they can also be recognized to possess the potential to be employed as the raw material to synthesize other titanium compounds as well. The Pulmoddai mineral sand deposit in Sri Lanka is considered as a valuable resource containing pure ilmenite and can be used as a very good source of both titanium and iron. Because of the lower TiO2 content compared to rutile, processes, such as the Becher process, Laporte process and Kataoka process, have been developed to upgrade ilmenite into higher grade synthetic rutile. Additionally, research studies have been carried out to develop methods, such as the hydrochloride process, H3PO4/NH3 process, alkaline roasting process, aluminothermic reduction method, alkaline decomposition method, molten salt electroreduction method and magnesiothermic reduction method, to synthesize TiO2 and other related titanium compounds, such as titanium and iron oxides, composites and alloys, from naturally occurring ilmenite where these methods possess both rewards as well as drawbacks over the others.

This article presents studies on the ammonium fluoride processing of dusts from the reduction smelting of ilmenite concentrate with separation of silicon to obtain titanium dioxide. Optimal conditions for pyrohydrolysis of titanium fluorides were determined. The effects of temperature and duration on the process were studied. The optimal conditions for pyrohydrolysis of titanium fluorides were a temperature of 600 °C and duration of 240–300 min. The degree of titanium fluoride conversion to titanium oxide was 99.5% at these conditions. Titanium dioxide obtained by pyrohydrolysis of titanium fluorides was purified from iron, chromium, and manganese impurities. The effect of hydrochloric acid solution concentration, S:L ratio, and the process duration on the purification degree of titanium fluoride pyrohydrolysis was studied. The following optimum purification conditions were determined: hydrochloric acid solution concentration 12.5–15 wt%, temperature 25–30 °C, S:L = 1:6÷8, duration 20–30 min. The purified titanium dioxide consisted mainly of anatase. The pigmented titanium dioxide of rutile modification with 99.8 wt% TiO2 was obtained after calcination at 900 °C for 120 min.

Due to the similar physical and chemical properties of ilmenite and olivine, separating them is challenging. The flotation process, with the use of collectors, is an effective method. In this study, a ternary collector consisting of aluminum ion (III), benzohydroxamic acid (BHA), and sodium oleate (NaOL) was prepared for the flotation separation of ilmenite and olivine. Through micro-flotation experiments, molecular dynamics simulation (MD), density functional theory (DFT), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis, the synergistic effect between the components of the ternary collector and the adsorption configuration on the surface of ilmenite was investigated. The results revealed that at pH = 8, Al (III), BHA, and NaOL could coordinate and adsorb effectively on the surface of ilmenite, enhancing its floatability for separation from olivine. The adsorption configuration differed from previous reports, showing a co-adsorption of multiple forms on the surface of ilmenite.

The discovery of massless Dirac electrons in graphene and topological Dirac-Weyl materials has prompted a broad search for bosonic analogues of such Dirac particles. Recent experiments have found evidence for Dirac magnons above an Ising-like ferromagnetic ground state in a two-dimensional (2D) kagome lattice magnet and in the van der Waals layered honeycomb crystalCrI3, and in a 3D Heisenberg magnetCu3TeO6. Here, we report our inelastic neutron scattering investigation on a large single crystal of a stacked honeycomb lattice magnetCoTiO3, which is part of a broad family of ilmenite materials. The magnetically ordered ground state ofCoTiO3features ferromagnetic layers ofCo2+, stacked antiferromagnetically along thecaxis. The magnon dispersion relation is described very well with a simple magnetic Hamiltonian with strong easy-plane exchange anisotropy. Importantly, a magnon Dirac cone is found along the edge of the 3D Brillouin zone. Our results establishCoTiO3as a model pseudospin-1/2material to study interacting Dirac bosons in a 3D quantumXYmagnet.