THE (MG,FE2+) SUBSTITUTION IN FERRI-CLINOHOLMQUISTITE, □LI2(MG,FE2+)3FE3+2SI8O22(OH)2
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dc.contributor.author | Iezzi G. | |
dc.contributor.author | Novembre D. | |
dc.contributor.author | Della Ventura G. | |
dc.contributor.author | Hawthorne F.C. | |
dc.contributor.author | Pedrazzi G. | |
dc.contributor.author | Roberrt J.-L. | |
dc.date.accessioned | 2023-11-26T02:22:40Z | |
dc.date.available | 2023-11-26T02:22:40Z | |
dc.date.issued | 2005 | |
dc.identifier | https://www.elibrary.ru/item.asp?id=14506473 | |
dc.identifier.citation | European Journal of Mineralogy, 2005, 17, 5, 733-740 | |
dc.identifier.issn | 0935-1221 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/41997 | |
dc.description.abstract | Amphiboles have been synthesized by hydrothermal techniques at 500–600 °C, 1 Kbar P(H2O) and low oxygen fugacity (close to NNO) at nominal compositions along the join ferri-clinoholmquistite [squareLi2Mg3Fe3+2Si8O22(OH)2] – ferri-clino-ferroholmquistite [squareLi2Fe2+3Fe3+2Si8O22(OH)2]. SEM-EDS and X-ray powder diffraction show that at 500 °C, amphibole is the dominant phase in the run assemblage, together with minor clinopyroxene + quartz, in the Fe-rich side of the join, up to sim50 mol. % ferri-holmquistite component in the system. For higher Mg contents, an assemblage consisting of predominant clinopyroxene + quartz is obtained, and amphibole is only a minor phase. At 600 °C, the situation is reversed: amphibole is the predominant phase in the Mg-rich side of the join (sim60–100 mol. % ferri-holmquistite component in the system). X-ray powder-diffraction patterns can be indexed in space group C2/m and cell parameters show well-defined linear trends as a function of nominal amphibole composition. Mössbauer spectra show that Fe3+ is strongly ordered at the M2 site, whereas Fe2+ is disordered over the B and C sites. The infrared OH-stretching spectra of intermediate compositions show fine structure caused by ordering of Mg and Fe2+ over the M1 and M3 sites in the amphibole; this fine structure consists of four main bands assigned to the four local combinations of (Mg,Fe2+) at M(1,3). The relative intensities of these bands show that there is almost complete Mg-Fe2+ substitution at M(1,3) in ferri-clinoholmquistite and that there is no significant short-range ordering (cluster and/or anti-clustering) between these two cations at the M(1,3) sites. The IR spectra show, in addition, four minor components that are assigned to (Fe2+,Mg) at M(4), indicating that the amphibole composition departs from the nominal one following the vector M4Fe2+ M2Mg M2Fe3+-1M4Li-1. | |
dc.title | THE (MG,FE2+) SUBSTITUTION IN FERRI-CLINOHOLMQUISTITE, □LI2(MG,FE2+)3FE3+2SI8O22(OH)2 | |
dc.type | Статья | |
dc.identifier.doi | 10.1127/0935-1221/2005/0017-0733 |
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