Structural state of Rare Earth Elements in eudialyte-group minerals

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Marco E. Ciriotti
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Iscritto il: ven 25 giu, 2004 11:31
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Structural state of Rare Earth Elements in eudialyte-group minerals

Messaggio da Marco E. Ciriotti » ven 02 ago, 2019 13:05

Prossima pubblicazione.

Referenza:
▪ Borst, A.M., Finch, A.A., Friis, H., Horsburgh, N.J., Gamaletsos, P.N., Goettlicher, J., Steininger, R., Geraki, K. (2020): Structural State of Rare Earth Elements in Eudialyte-Group Minerals. Mineralogical Magazine, 84, (in press).

Abstract:
Eudialyte group minerals (EGM) attract global interest as potential resources for High Field Strength Elements (HFSE, e.g. Zr, Nb, Ta, and Rare Earth Elements, REE), i.e. critical materials for modern technologies. They are particularly valued for their relative enrichment in the most critical lanthanides, i.e. Nd and heavy REE (Gd-Lu). However, REE substitution mechanisms into the EGM structure are still poorly understood. Light and heavy REE may occupy different sites and there may be ordering and/or defect clustering in the structure. This study uses X-ray Absorption Spectroscopy (XAS) to determine the structural state of REE in EGM from prospective eudialyte-bearing complexes. Yttrium K-edge and Nd L3-edge spectra were collected as proxies for heavy and light REE, respectively, and compared to natural and synthetic REE-bearing standards. Extended X-ray Absorption Fine Structure (EXAFS) data yield best fits for Y in six-fold coordination with Y-O distances of 2.24-2.32 Å, and a second coordination sphere comprising Fe, Na, Ca, Si and O at radial distances of 3.6-3.8 Å. These findings are consistent with dominant Y3+ substitution for Ca2+ on the octahedral M1 site in all samples studied, and exclude preferential substitution of Y3+ onto the smaller octahedral Z site or the large low-symmetry N4 site.
Using lattice strain theory, we constructed relative partitioning models to predict site preferences of lanthanides we have not directly measured. The models predict that all REE are favoured on the Ca-dominant M1 site and that preferential partitioning of heavy over light REE increases in EGM containing significant Mn in the M1-octahedral rings (oneillite-subgroup). Thus, the flat REE profiles that make EGM such attractive exploration targets are not due to preferential partitioning of light and heavy REE onto different sites. Instead, local ordering of Mn- and Ca-occupied M1 sites may influence the capacity of EGM to accommodate heavy REE.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 26570
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Re: Structural state of Rare Earth Elements in eudialyte-group minerals

Messaggio da Marco E. Ciriotti » ven 02 ago, 2019 14:00

Nel testo si dice che le specie del gruppo dell'eudialyte sono 29 (nell'abstract si dice 28; sic!). In realtà sono 30.
Eccole:

Alluaivite Na19(Ca,Mn2+)6(Ti,Nb)3Si26O74Cl·2H2O
Andrianovite Na12(K,Sr,Ce)3Ca6Mn2+3Zr3NbSi25O73(O,H2O,OH)5
Aqualite (H3O)8(Na3K1.5Sr0.5)Σ=5Ca6Zr3Si26O66(OH)9Cl
Carbokentbrooksite (Na,☐)12(Na,Ce)3Ca6Mn2+3Zr3Nb(Si25O73)(OH)3(CO3)·H2O
Davinciite Na12K3Ca6Fe2+3Zr3(Si26O73OH)Cl2
Dualite Na30(Ca,Na,Ce,Sr)12(Na,Mn,Fe,Ti)6MnSi3[Zr3(Si3O9)2(Si9O27)2][Ti3(Si3O9)2(Si9O27)2](OH,H2O,Cl)9
Eudialyte Na12Na3Ca6Fe2+3Zr3Si(Si25O73)(O,OH,H2O)3(Cl,OH)2
Feklichevite Na11Ca9(Fe3+,Fe2+)2Zr3Nb(Si25O73)(O,Cl,OH,H2O)5
Fengchengite Na12☐3(Ca,Sr)6Fe3+3Zr3Si(Si25O73)(H2O,OH)3(OH,Cl)2
Ferrokentbrooksite (Na,Y)15(Ca,Ce)3(Ca,Ce)3(Fe2+,Mn2+)3Zr3Nb(Si25O73)(O,OH,H2O)3(Cl,F,OH)2
Georgbarsanovite Na12[Mn,Sr,(Ce,La,Nd,Y)]3Ca6Fe2+3Zr3NbSi25O76Cl2·H2O
Golyshevite (Na10Ca3)Ca6Zr3(Fe3+,Fe2+)2SiNb[Si3O9]2[Si9O27]2(OH)3(CO3)·H2O
Ikranite (Na,K,H3O)15(Ca,Mn,REE)6Fe3+2Zr3(☐,Zr)(☐,Si)Si24O66(O,OH)6Cl·nH2O (n = 2÷3)
Ilyukhinite (H3O,Na)14Ca6Mn2Zr3Si26O72(OH)2·3H2O
Johnsenite-(Ce) Na12(Ce,Sr,Ca,La,Mn2+)3Ca6Mn2+3Zr3W(Si25O73)(CO3)(OH,Cl)2
Kentbrooksite (Na12REE3)15(Ca,REE)6Mn2+3Zr3Nb(Si25O73)(O,OH,H2O)3F2
Khomyakovite (Na12Sr3)Ca6Fe2+3Zr3W(Si25O73)(O,OH,H2O)3(OH,Cl)2
Labyrinthite (Na,K,Sr)35Ca12Fe3Zr6TiSi51O144(O,OH,H2O)9Cl3
Manganoeudialyte Na14Ca3Ca3Mn2+3Zr3Si[Si25O72(OH)2]Cl2·4H2O
Manganokhomyakovite (Na12Sr3)Ca6Mn2+3Zr3W(Si25O73)(O,OH,H2O)5(OH,Cl)2
Mogovidite Na9(Ca,Na)6Ca6(Fe3+,Fe2+)2Zr3☐Si25O72(CO3)(OH,H2O)4
Oneillite Na15Ca3Mn2+3Fe2+3Zr3Nb(Si25O73)(O,OH,H2O)3(OH,Cl)2
Raslakite Na15(Ca3Fe3)(Na,Zr)3[Zr3(Si,Nb)(Si25O73)(OH,H2O)3](Cl,OH)
Rastsvetaevite Na27K8Ca12Fe3Zr6(Si52O144)(OH,O)6Cl2
Sergevanite Na15(Ca3Mn3)(Na2Fe)Zr3Si26O72(OH)3·H2O
Siudaite Na8(Mn2+2Na)Ca6Fe3+3Zr3NbSi25O74(OH)2Cl·5H2O
Taseqite Na12Sr3Ca6Fe3Zr3NbSi25O73(O,OH,H2O)3Cl2
Voronkovite Na15(Na,Ca,Ce)3(Mn,Ca)3Fe3Zr3Si26O72(OH,O)4Cl·H2O
Zirsilite-(Ce) (Na,☐])12(Ce,Na)3Ca6Mn2+3Zr3Nb(Si25O73)(OH)3(CO3)·H2O
Zirsinalite [Na3][Na3][Ca☐]Zr[Si6O18]

Molte di queste formule necessitano di un'operazione "polish-up".
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 26570
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: Structural state of Rare Earth Elements in eudialyte-group minerals

Messaggio da Marco E. Ciriotti » lun 30 dic, 2019 12:24

A parte l'errorino sul numero di eudialiti approvate dall'IMA, il lavoro - come atteso - è di eccellente qualità.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

Avatar utente
Marco E. Ciriotti
Messaggi: 26570
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: Structural state of Rare Earth Elements in eudialyte-group minerals

Messaggio da Marco E. Ciriotti » gio 26 mar, 2020 17:33

Pubblicazione effettuata.

Referenza:
▪ Borst, A.M., Finch, A.A., Friis, H., Horsburgh, N.J., Gamaletsos, P.N., Goettlicher, J., Steininger, R., Geraki, K. (2020): Structural State of Rare Earth Elements in Eudialyte-Group Minerals. Mineralogical Magazine, 84, 19-34.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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