Mass balance vs Rietveld refinement to determine the modal composition of ultramafic rocks: The case study of mantle peridotites from Northern Victoria Land (Antarctica)
This paper aims at applying the Rietveld refinement method to X-ray powder diffraction (XRPD) spectra in order to determine the mineralogical assemblages of ultramafic rocks. The results are compared to those obtained by mass balance (MB) calculations, a least squares method that reduces major eleme...
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ftunivferrarair:oai:iris.unife.it:11392/2310617 2024-02-11T09:56:59+01:00 Mass balance vs Rietveld refinement to determine the modal composition of ultramafic rocks: The case study of mantle peridotites from Northern Victoria Land (Antarctica) S. Gentili S. Comodi P. BONADIMAN, Costanza COLTORTI, Massimo S. Gentili, S. Comodi, P. Bonadiman, Costanza Coltorti, Massimo 2015 STAMPA http://hdl.handle.net/11392/2310617 https://doi.org/10.1016/j.tecto.2015.01.024 https://www.sciencedirect.com/science/article/pii/S0040195115000852 eng eng info:eu-repo/semantics/altIdentifier/wos/WOS:000356121400011 volume:650 firstpage:144 lastpage:155 numberofpages:12 journal:TECTONOPHYSICS http://hdl.handle.net/11392/2310617 doi:10.1016/j.tecto.2015.01.024 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-84929357920 https://www.sciencedirect.com/science/article/pii/S0040195115000852 info:eu-repo/semantics/closedAccess X-ray powder diffraction Rietveld method Mass balance calculations Modal composition Geologic material info:eu-repo/semantics/article 2015 ftunivferrarair https://doi.org/10.1016/j.tecto.2015.01.024 2024-01-24T17:33:16Z This paper aims at applying the Rietveld refinement method to X-ray powder diffraction (XRPD) spectra in order to determine the mineralogical assemblages of ultramafic rocks. The results are compared to those obtained by mass balance (MB) calculations, a least squares method that reduces major element chemical analyses to the whole rock composition. This methodological work was carried out in five hydrous and anhydrous mantle xenoliths from Northern Victoria Land, Antarctica. The intrinsic goodness of the XRPD and MB results, evaluated by with R-wp and r(2) respectively, shows similar values of modal compositions. Independent of the mineralogy (amphibole-bearing and amphibole-free) and textures (fine to coarse grained), good agreement (<2%) is observed for modal contents lower than 10%, whereas a discrepancy of up to 10% is recorded for phase abundances higher than 70%. The comparison of the two methods has allowed us to demonstrate that the Rietveld method is applicable even when limited amount of material (<1 g) is available, and the "classical" chemical approaches (XRF and EMPA) cannot be applied. Moreover it not only provides information on rock mineral concentrations (wt.%), but also gives supplementary information on crystallographic data (i.e., mineral crystallite size, mineral lattice parameters, density, site occupancies). On the other hand, the MB procedure provides direct chemical information of both bulk rock and minerals, but requires a large amount of material (i.e., for XRF at least >1 g of material is needed). Dealing with MB procedure, problems can occur if accessory minerals cannot be identified in thin sections, which are, however, part of the whole-rock analysis. Besides, the strength of XRPD, if compared with all the suitable methods for the quantitative mineralogical identification, is to provide direct information about the physical properties, and mineral site occupancies that could indirectly give a mineral chemical composition. Article in Journal/Newspaper Antarc* Antarctica Victoria Land Università degli Studi di Ferrara: CINECA IRIS Victoria Land Tectonophysics 650 144 155 |
institution |
Open Polar |
collection |
Università degli Studi di Ferrara: CINECA IRIS |
op_collection_id |
ftunivferrarair |
language |
English |
topic |
X-ray powder diffraction Rietveld method Mass balance calculations Modal composition Geologic material |
spellingShingle |
X-ray powder diffraction Rietveld method Mass balance calculations Modal composition Geologic material S. Gentili S. Comodi P. BONADIMAN, Costanza COLTORTI, Massimo Mass balance vs Rietveld refinement to determine the modal composition of ultramafic rocks: The case study of mantle peridotites from Northern Victoria Land (Antarctica) |
topic_facet |
X-ray powder diffraction Rietveld method Mass balance calculations Modal composition Geologic material |
description |
This paper aims at applying the Rietveld refinement method to X-ray powder diffraction (XRPD) spectra in order to determine the mineralogical assemblages of ultramafic rocks. The results are compared to those obtained by mass balance (MB) calculations, a least squares method that reduces major element chemical analyses to the whole rock composition. This methodological work was carried out in five hydrous and anhydrous mantle xenoliths from Northern Victoria Land, Antarctica. The intrinsic goodness of the XRPD and MB results, evaluated by with R-wp and r(2) respectively, shows similar values of modal compositions. Independent of the mineralogy (amphibole-bearing and amphibole-free) and textures (fine to coarse grained), good agreement (<2%) is observed for modal contents lower than 10%, whereas a discrepancy of up to 10% is recorded for phase abundances higher than 70%. The comparison of the two methods has allowed us to demonstrate that the Rietveld method is applicable even when limited amount of material (<1 g) is available, and the "classical" chemical approaches (XRF and EMPA) cannot be applied. Moreover it not only provides information on rock mineral concentrations (wt.%), but also gives supplementary information on crystallographic data (i.e., mineral crystallite size, mineral lattice parameters, density, site occupancies). On the other hand, the MB procedure provides direct chemical information of both bulk rock and minerals, but requires a large amount of material (i.e., for XRF at least >1 g of material is needed). Dealing with MB procedure, problems can occur if accessory minerals cannot be identified in thin sections, which are, however, part of the whole-rock analysis. Besides, the strength of XRPD, if compared with all the suitable methods for the quantitative mineralogical identification, is to provide direct information about the physical properties, and mineral site occupancies that could indirectly give a mineral chemical composition. |
author2 |
S. Gentili, S. Comodi, P. Bonadiman, Costanza Coltorti, Massimo |
format |
Article in Journal/Newspaper |
author |
S. Gentili S. Comodi P. BONADIMAN, Costanza COLTORTI, Massimo |
author_facet |
S. Gentili S. Comodi P. BONADIMAN, Costanza COLTORTI, Massimo |
author_sort |
S. Gentili S. |
title |
Mass balance vs Rietveld refinement to determine the modal composition of ultramafic rocks: The case study of mantle peridotites from Northern Victoria Land (Antarctica) |
title_short |
Mass balance vs Rietveld refinement to determine the modal composition of ultramafic rocks: The case study of mantle peridotites from Northern Victoria Land (Antarctica) |
title_full |
Mass balance vs Rietveld refinement to determine the modal composition of ultramafic rocks: The case study of mantle peridotites from Northern Victoria Land (Antarctica) |
title_fullStr |
Mass balance vs Rietveld refinement to determine the modal composition of ultramafic rocks: The case study of mantle peridotites from Northern Victoria Land (Antarctica) |
title_full_unstemmed |
Mass balance vs Rietveld refinement to determine the modal composition of ultramafic rocks: The case study of mantle peridotites from Northern Victoria Land (Antarctica) |
title_sort |
mass balance vs rietveld refinement to determine the modal composition of ultramafic rocks: the case study of mantle peridotites from northern victoria land (antarctica) |
publishDate |
2015 |
url |
http://hdl.handle.net/11392/2310617 https://doi.org/10.1016/j.tecto.2015.01.024 https://www.sciencedirect.com/science/article/pii/S0040195115000852 |
geographic |
Victoria Land |
geographic_facet |
Victoria Land |
genre |
Antarc* Antarctica Victoria Land |
genre_facet |
Antarc* Antarctica Victoria Land |
op_relation |
info:eu-repo/semantics/altIdentifier/wos/WOS:000356121400011 volume:650 firstpage:144 lastpage:155 numberofpages:12 journal:TECTONOPHYSICS http://hdl.handle.net/11392/2310617 doi:10.1016/j.tecto.2015.01.024 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-84929357920 https://www.sciencedirect.com/science/article/pii/S0040195115000852 |
op_rights |
info:eu-repo/semantics/closedAccess |
op_doi |
https://doi.org/10.1016/j.tecto.2015.01.024 |
container_title |
Tectonophysics |
container_volume |
650 |
container_start_page |
144 |
op_container_end_page |
155 |
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1790607574769336320 |