(2020) First-Principles Modeling of X-Ray Absorption Spectra Enlightens the Processes of Scandium Sequestration by Iron Oxides
Chassé M, Blanchard M, Cabaret D, Juhin A, Vantelon D & Calas G
08i: Room 3, Tuesday 23rd June 06:57 - 07:00
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Many thanks Mathieu, this is a very interesting talk. What are the host minerals for Sc that break down during weathering and release it to be adsorbed on Fe-oxide surfaces? I guess that quite specific lithologies must be required, both to have reasonable Sc enrichment in the protolith, and then to produce significant amounts of Fe-oxide in the laterite to retain the Sc. Does Sc also adsorb onto clays (like the REE do)?
Dear Kathryn, Thank you for your question. The lithology is indeed a major condition to find significant Sc enrichments. Most lateritic profiles developed on ultramafic rocks exhibit high Sc contents (50-100 ppm). In specific places, where pyroxenite, amphibolite or gabbro are altered, concentrations can reach several hundreds of ppm (which is among the highest Sc enrichment you can find, in pegmatites you can sometime reach 1000 ppm, not much more). Pyroxenes (specifically clinopyroxenes) and amphiboles are the major Sc-bearing phases in these rocks. The chemical composition is also leading to significant Fe enrichments. The combination of these two factors lead to Sc trapping by Fe oxides. Scandium adsorption onto clays is limited. In clay-rich horizons I studied, in which REE are strongly enriched (relatively to the protolith), Sc enrichment is not that high, because it is not redistributed from upper levels as REE are because it is trapped by Fe oxides. Actually, in clay-rich horizons I studied, I found that Sc was incorporated into the crystal network of smectite-clay minerals, which are replacing pyroxenes. If you want to know more about it, you can find more details in one of our recent papers : https://www.sciencedirect.com/science/article/pii/S0016703719303850?casa_token=Fo_Gf60swCcAAAAA:Ilfyxfoc4LFdmvnQTGomFgu7mX6CReCmuMofHyOayFFtS3T-uJbfNSVlz1eEqkeHl3mU1d2XBNU (you can find a preprint version on ResearchGate)
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