Magmatic fractionation and the magmatic-hydrothermal transition in rare metal granites: Evidence from Argemela (Central Portugal)

Abstract

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Rare elements enrichment in crustal peraluminous magmas: insights from partial melting experiments

“…Fig.10Comparison between experimental melts from this study (Tables4, 5) and compositions of Variscan granites and volcanic equivalents(Cornwall: Simons et al 2016Manning and Hill 1990; Portugal: Charoy and Noronha 1996;Neiva 2002;Michaud 2019;Michaud and Pichavant 2020; French Massif Central: Raimbault et al 1995;Raimbault and Burnol 1998;Villaros and Pichavant, 2019; Armorican Massif: Ballouard et al 2015; Spain: Chicharro et al 2016; Erzgebirge: Breiter et al 2005; Macusani Volcanics: Pichavant et al 1987). a Major element compositions plotted in the A*-B* diagram ofDebon and Lefort (1983), see Tables1 and 4. b Nb/Ta vs. Nb content.…”

“…However, RMGs might be produced by a combination of petrogenetic processes rather than by partial melting alone. For example, crystallization differentiation might act together with mica dehydration-melting to produce the distinctive RMG geochemical signatures (e.g., Pichavant et al 1988b;Raimbault et al 1995;Roda-Robles et al 2018;Michaud and Pichavant 2020). Evaluation of this scenario requires combined melting-fractionation models incorporating the type of information presented in this study for partial melting processes.…”

“…This implies that biotite is not a key W sequestering phase in high grade residual source rocks. In contrast, the elevated K d W for muscovite (~ 2, Raimbault and Burnol 1998;Michaud and Pichavant 2020) makes this phase critical in the supply of W to crustal melts.…”

“…Major element chemistries of experimental melts are compared with whole-rock compositions of Variscan granites and volcanic equivalents with examples taken from Cornwall (Simons et al 2016(Simons et al , 2017Manning and Hill 1990), Portugal (Charoy and Noronha 1996;Neiva 2002;Michaud 2019;Michaud and Pichavant 2020), French Massif Central (Raimbault et al 1995;Raimbault and Burnol 1998;Villaros and Pichavant 2019), Armorican Massif (Ballouard et al 2015), Spain (Chicharro et al 2016), Erzgebirge (Breiter et al 2005) and from the Macusani Volcanics (Pichavant et al 1987). Variscan granites include peraluminous biotite, biotite-muscovite, muscovite and rare metal granites.…”

“…Overall, and while noting that caution is required with the use of whole-rock data as proxies of melt concentrations (see Michaud and Pichavant 2020 for illustration), significant differences exist between the rare element patterns of experimental melts and Variscan granites. 4, 5) and compositions of Variscan granites and volcanic equivalents (Cornwall: Simons et al 2016Simons et al , 2017Manning and Hill 1990;Portugal: Charoy and Noronha 1996;Neiva 2002;Michaud 2019;Michaud and Pichavant 2020;French Massif Central: Raimbault et al 1995;Raimbault and Burnol 1998;Villaros and Pichavant, 2019;Armorican Massif: Ballouard et al 2015;Spain: Chicharro et al 2016;Erzgebirge: Breiter et al 2005;Macusani Volcanics: Pichavant et al 1987). a Major element compositions plotted in the A*-B* diagram of Debon and Lefort (1983), see Tables 1 and 4.…”