The petrogenesis of high grade contact metamorphic mineral assemblages in calc-silicate xenoliths, Eastern bushveld complex, South Africa

One of the most spectacular but least studied thermal metamorphic aureoles is undoubtedly that surrounding the intrusive rocks of the Bushveld Complex. Apart from displaying a vast range of metamorphic assemblages in pelitic rocks of the Pretoria Group, xenoliths of calcsilicates within the intrusive rocks of the complex host some unique assemblages unknown from other localities. The degree of thermal metamorphism belongs to the highest ever recorded. A petrogenetic grid is proposed, which covers the highest degrees of metamorphism occurring in the system Ca0-Mg0-Sio2-co2. This petrogenetic grid involves 65 stable and metastable mineral reactions and serves to predict the fate of siliceous dolomites under extreme contact metamorphic conditions. With increasing temperature akermanite, monticellite, merwinite and periclase formed from mainly irreversible decarbonation reactions in which calcite was an important reactant. From diagnostic mineral parageneses overburden load pressures of 1.1 - 2.2 kbar for the emplacement of the critical zone magma and 0.6- 1.6 kbar for the marginal zone magma can be inferred. Forsterite exsolutions in monticellite with an unusual optical positive sign and dehydroxylated Ba-phlogopite indicate magma temperatures higher than 1200°c, while the lack of melting of the present high-temperature mineral assemblages gives an upper temperature limit of 1400°c. The minerals and mineral assemblages found in the marginal and critical zone xenoliths were hardly affected by hydration during retrograde metamorphism. The upper zone xenoliths consist mainly of vesuvianite-, grandite- and melilite-bearing mineral assemblages, which became stable during relatively late stages of retrograde metamorphism. In the upper zone xenoliths most of the minerals present belong to the system CaO-MgO-Si02-A1 2o 3-H2o-co2. There are strong indications that they formed from minerals similar to those found in the high temperature mineral assemblages of the marginal zone xenoliths. The average Al 2o3 content in the melilites originally present in the upper zone xenoliths was higher than in the marginal zone xenoliths. This, together with an influx of a H20-rich fluid phase during retrograde metamorphism led to the formation of the vesuvianite- and grandite-bearing mineral assemblages. Microprobe analyses of different coloured Mg-Fe-vesuvianites, garnets of different composition, prehnite and xanthophyllite show unusual variations in their chemical composition.Thesis (DSc)--University of Pretoria, 1988.GeologyDScUnrestricte

Detailed Microparticle Analyses Providing Process Relevant Chemical and Microtextural Insights into the Black Mass

Eramet uses a combination of physical and hydrometallurgical treatment to recycle lithium-ion batteries. Before hydrometallurgical processing, mechanical treatment is applied to recover the Black Mass which contains nickel, cobalt, manganese and lithium as valuable elements as well as graphite, solvent, plastics, aluminium and copper. To evaluate the suitability for hydrometallurgical recycling, it is essential to analyse the Black Mass chemically but also with respect to size, shape and composition of particles in the Black Mass. The Black Mass of various battery recyclers was investigated by using a combination of SEM/QEMSCAN® analyses. This specific QEMSCAN® database contains 260 subgroups, which comprise major and minor chemical variations of phases. The database was created using millions of point analyses. Major observations are: (1) particles can be micro-texturally characterised and classified with respect to chemical element contents; (2) important textural and chemical particle variations exist in the Black Mass from several origins leading to different levels of quality; (3) elements deleterious to hydrometallurgical processing (i.g. Si, Ca, Ti, Al, Cu and others) are present in well liberated particles; (4) components can be quantified and cathodes active material compositions (LCO, different NMC, NCA, LFP, etc.) that are specific for each battery type can be identified; (5) simulation of further physical mineral processing can optimise Black Mass purity in valuable elements

Physical property changes of Fe-Ti oxides along their alteration: a geometallurgical study to improve the yield of a mineralurgical plant

International audienc

Binder-free tableting experiments on manganese oxides and industrial mineral powders

International audienceCold, binder-free tableting experiments under controlled pressure (0-450 MPa), water addition (0-10 wt.%) and pH (4, 11) were performed on powder of pyrolusite ore concentrates, refined hausmannite, bentonite, kaolinite, as well as blends of those materials. It has been shown that increased pressure was beneficial for agglomeration of oxide materials, but pressure > 250 MPa triggered an elastic recovery in the clay minerals. Water addition up to 4 wt.% improved tabletability, increasing diametral resistance and reducing elastic recovery and fines generation. Amounts above 6 wt.% decreased diametral resistance. The presence of layered-structure minerals (such as montmorillonite, kaolinite, lithiophorite) appeared to be key to determine the agglomeration potential of a sample. This study also showed that tableting provides good performances for recycling industrial manganese oxide fines by obtaining industrial-grade resistance for tablets made with an 80/20 pyrolusite concentrate/hausmannite blends and 4 wt.% H2O

Building a Hyperspectral Library and its Incorporation into Sparse Unmixing for Mineral Identification

International audienceThe objective of the SOLSA project (EU-H2020) is to develop an analytical expert system for on-line-on-mine-real-time mineralogical and geochemical analyses on sonic drill cores. As one aspect of the system, this paper presents the building of the hyperspectral library and its incorporation into sparse unmixing techniques for mineral identification. Twenty seven spectra representing 14 minerals have been collected for the library. Three sparse unmixing techniques have been investigated and evaluated using simulated data generated from our hyperspectral library, and real hyperspectral data acquired from a serpentinized harzburgite sample. Among the three techniques, the collaborative sparse unmixing by variable splitting and augmented Lagrangian (CLSUnSAL) method provided the best accurate results on the simulated data. In addition, the results of the CLSUnSAL method show high correlation with that of the QEMSCAN® analysis on the harzburgite hyperspectral data

Building a Hyperspectral Library and its Incorporation into Sparse Unmixing for Mineral Identification

International audienceThe objective of the SOLSA project (EU-H2020) is to develop an analytical expert system for on-line-on-mine-real-time mineralogical and geochemical analyses on sonic drill cores. As one aspect of the system, this paper presents the building of the hyperspectral library and its incorporation into sparse unmixing techniques for mineral identification. Twenty seven spectra representing 14 minerals have been collected for the library. Three sparse unmixing techniques have been investigated and evaluated using simulated data generated from our hyperspectral library, and real hyperspectral data acquired from a serpentinized harzburgite sample. Among the three techniques, the collaborative sparse unmixing by variable splitting and augmented Lagrangian (CLSUnSAL) method provided the best accurate results on the simulated data. In addition, the results of the CLSUnSAL method show high correlation with that of the QEMSCAN® analysis on the harzburgite hyperspectral data