Value chain politicisation to boost rare earth supply

Significance Short-term factors combined to strengthen prices, including widespread flooding in China’s Sichuan province and low capacity utilisation among producers outside China. In the first two months of 2021, Chinese exports of rare earths rebounded by 28.8% year-on-year to 7,068 tonnes, although this was boosted by the low base of a demand slump in early 2020. Impacts Beijing has threatened to cut off supplies of refined rare earth products to US aerospace firm Lockheed Martin for trading with Taiwan. Norway may plan mining after finding polymetallic sulfides in its seabed containing high concentrations of lithium and certain rare earths. China also imports rare earths, and problems with shipping raw materials from Myanmar will exacerbate its rare earth shortages. US firm Energy Fuels is partnering with Neo Performance’s European operations to provide concentrates free of radioactive materials.

Exploring ocean floor geodiversity in relation to mineral resources in the Pacific Ocean

<p>There is a growing demand for mineral resources such as metals and rare earth elements, but global terrestrial resources are rapidly declining. Alternatively, the ocean floor provides unprecedented mining potential. However, their occurrences  in relation to ocean floor geodiversity is largely unexplored. Therefore, it is unclear what the (irreversible) potential impact of future mining is on ocean floor geodiversity.</p><p>Here, we quantify the ocean floor geodiversity of the West-Pacific ocean floor and explore the distribution of three mineral resources: polymetallic sulfides, cobalt-rich ferromanganese crusts and polymetallic nodules.  We developed a workflow for the calculation of a geodiversity index composed of openly available geomorphological, sediment thickness, bathymetric and derived ocean floor roughness input data in ArcGIS Pro.</p><p>Our results show a large variety in geodiversity on the West-Pacific ocean floor, ranging from very low and low geodiversity on large plateaus and in wide trenches and throughs, to high and very high geodiversity in heterogeneous, patchy environments on shelves, basins and abyssal plains. Regression analysis results indicate that polymetallic sulfides and cobalt-rich ferromanganese crusts positively correlate to the geodiversity index, while polymetallic nodules indicate a negative correlation.  Further analysis will focus on refining and expanding this method to a global extent by adding ocean floor age, a possible important factor, into the geodiversity assessment.</p><p>Our findings suggest that understanding of ocean floor geodiversity can contribute to promote sustainable mining and support conservation of the ocean floor.</p>

Genesis of the Longmendian Ag–Pb–Zn Deposit in Henan (Central China): Constraints from Fluid Inclusions and H–C–O–S–Pb Isotopes

The Longmendian Ag–Pb–Zn deposit is located in the southern margin of the North China Craton, and the mineralization occurs mainly in quartz veins, altered gneissic wallrocks, and minor fault breccias in the Taihua Group. Based on vein crosscutting relations, mineral assemblages, and paragenesis, the mineralization can be divided into three stages: (1) quartz–pyrite, (2) quartz–polymetallic sulfides, and (3) quartz–carbonate–polymetallic sulfides. Wallrock alteration can be divided into three zones, i.e., chlorite–sericite, quartz–carbonate–sericite, and silicate. Fluid inclusions in all Stage 1 to 3 quartz are dominated by vapor-liquid two-phase aqueous type (W-type). Petrographic and microthermometric analyses of the fluid inclusions indicate that the homogenization temperatures of Stages 1, 2, and 3 are 198–332°C, 132–260°C, and 97–166°C, with salinities of 4.0–13.3, 1.1–13.1, and 1.9–7.6 wt% NaCleqv, respectively. The vapor comprises primarily H2O, with some CO2, H2, CO, N2, and CH4. The liquid phase contains Ca2+, Na+, K+, SO42−, Cl−, and F−. The sulfides have δ34S=–1.42 to +2.35‰ and 208Pb/204Pb=37.771 to 38.795, 207Pb/204Pb=15.388 to 15.686, and 206Pb/204Pb=17.660 to 18.101. The H–C–O–S–Pb isotope compositions indicate that the ore-forming materials may have been derived from the Taihua Group and the granitic magma. The fluid boiling and cooling and mixing with meteoric water may have been critical for the Ag–Pb–Zn ore precipitation. Geological and geochemical characteristics of the Longmendian deposit indicate that the deposit is best classified as medium- to low-temperature intermediate-sulfidation (LS/IS) epithermal-type, related to Cretaceous crustal-extension-related granitic magmatism.

Process and Mechanism of Gold Mineralization at the Zhengchong Gold Deposit, Jiangnan Orogenic Belt: Evidence from the Arsenopyrite and Chlorite Mineral Thermometers

The Zhengchong gold deposit, with a proven gold reserve of 19 t, is located in the central part of Jiangnan Orogenic Belt (JOB), South China. The orebodies are dominated by NNE- and NW- trending auriferous pyrite-arsenopyrite-quartz veins and disseminated pyrite-arsenopyrite-sericite-quartz alteration zone, structurally hosted in the Neoproterozoic epimetamorphic terranes. Three stages of hydrothermal alteration and mineralization have been defined at the Zhengchong deposit: (i) Quartz–auriferous arsenopyrite and pyrite; (ii) Quartz–polymetallic sulfides–native gold–minor chlorite; (iii) Barren quartz–calcite vein. Both invisible and native gold occurred at the deposit. Disseminated arsenopyrite and pyrite with invisible gold in them formed at an early stage in the alteration zones have generally undergone syn-mineralization plastic-brittle deformation. This resulted in the generation of hydrothermal quartz, chlorite and sulfides in pressure shadows around the arsenopyrite and the formation of fractures of the arsenopyrite. Meanwhile, the infiltration of the ore-forming fluid carrying Sb, Cu, Zn, As and Au resulted in the precipitation of polymetallic sulfides and free gold. The X-ray elements mapping of arsenopyrite and spot composition analysis of arsenopyrite and chlorite were carried out to constrain the ore-forming physicochemical conditions. The results show that the early arsenopyrite and invisible gold formed at 322–397 °C with lgf(S2) ranging from −10.5 to −6.7. The crack-seal structure of the ores indicates cyclic pressure fluctuations controlled by fault-valve behavior. The dramatic drop of pressure resulted in the phase separation of ore-forming fluids. During the phase separation, the escape of H2S gas caused the decomposition of the gold-hydrosulfide complex, which further resulted in the deposition of the native gold. With the weakening of the gold mineralization, the chlorite formed at 258–274 °C with lgf(O2) of −50.9 to −40.1, as constrained by the results from mineral thermometer.

The acidic waters in Italy: a brief overview

The present study is aimed at providing a brief overview of the Italian acidic waters based on literature and unpublished data. Acidic waters in Italy, as elsewhere, are relatively common and associated with extremely variable geological settings. Owing to their peculiar features, these waters may seriously affect the environment and the ecosystems. Along the Apennine belt, the western and inner sectors of the Italian peninsula record an anomalous geothermal gradient, mostly overlapping with the Neogene-to-present magmatism, that explains the presence of a huge amount of CO2(H2S)-rich gas and thermal water discharges, geothermal fields (e.g. Larderello and Mt. Amiata) and ore deposits (e.g. Fe- and polymetallic sulfides, e.g. Elba Island and Colline Metallifere). Acidic waters (pH ≤5) from volcanic and geothermal areas show outlet temperatures and Total Dissolved Solids (TDS) from 10 to 96°C and <1 to ≈30 g/L, respectively, with a chemical composition usually belonging to the Ca-SO4, NH4-SO4 or Na-Cl facies. Frequently, they are related to bubbling and boiling pools due to the interaction between deepsourced gases and shallow aquifers or meteoric waters. Concentrations of heavy metals and metalloids are in most cases high. Extremely high contents of metals are also recorded for those acidic waters that characterize the main Italian mining districts, mostly located in Sardinia (not included in the present study), Tuscany and NW Alps, where they are related to Acid Mine Drainage l.s. or Acid Rock Drainage. The pH values are as low as 2.08, with variable TDS concentrations. Compositionally, they are Na-SO4, Ca(Mg)-SO4, and/or Mg(Ca)-SO4 waters, prevalently due to oxidative processes affecting polymetallic sulfides.

Особенности спектров ЯМР -=SUP=-63,65-=/SUP=-Cu в локальном поле образцов полупроводникового минерала CuFeS-=SUB=-2-=/SUB=- из сульфидных месторождений океана

The results of studying natural samples of CuFeS_2 chalcopyrite mineral from hydrothermal ore manifestations of island arcs of the Pacific Ocean by ^63Cu nuclear magnetic resonance (^63Cu NMR) in a local field at room temperature are presented. The asymmetric shape of the detected resonance lines in the ^63Cu NMR spectrum indicates the presence of at least two overlapping lines. The presence of two overlapping central components can be a consequence of the occurrence of regions with different types of structural distortion near the resonant nuclei. These results show that the pulsed ^63Cu NMR method can be an effective method for studying the physical properties of deep-sea polymetallic sulfides of the global ocean.