Experimental anatexis, fluorine geochemistry and lead-isotope constraints on granite petrogenesis in the Seridó Belt, Borborema Province, northeastern Brazil

Geoquímica do magmatismo Ediacarano Serra do Caramuru, NE da Província Borborema, RN, Brasil

“…Durante a ascensão na crosta, o magma básico a intermediário induziu calor, propiciando a fusão parcial do embasamento encaixante, originando assim, magmas ácidos -fácies graníticas -com os quais exibe feições mixing e mingling. Sallet et al (2015) demonstram, por meio de estudos geoquímicos e isotópicos no batólito de Acari, que rochas shoshoníticas não constituem o magma parental dos tipos félsicos (granitos). Para Neves et al (2000) e Hollanda et al (2003), os altos teores de K 2 O, Sr e Nd radiogênicos das rochas máficas presentes em granitoides neoproterozoicos da Província Borborema corroboram a fusão parcial do manto superior.…”

Fluorine behavior during experimental muscovite dehydration melting and natural partitioning between micas: Implications for the petrogenesis of peraluminous leucogranites and pegmatites

“…The partially melted continental crust form migmatites where the anatectic granitic melt crystallize as a leucosome network along with a residual refractory mineral assembly or melanosome, usually bearing neo-formed or peritectic phases (e.g., Sawyer 2010). The mineralogical and chemical composition of the leuco-and melanosome are determined by the prevailing temperature and pressure, the presence of a fluid phase and its composition, and the chemical and mineralogical nature of the partially melted protolith (e.g., Gao et al 2016;Sallet et al 2015;Weinberg and Hasalovà 2015).…”

“…DOI: https://doi.org/10.2138/am-2022-8663. http://www.minsocam.org/ and Johannes 1991; Sallet et al 2015;Sawyer 2010;Weinberg and Hasalovà 2015) (ii) fluidabsent muscovite dehydration melting in the temperature range of 650 to 750 °C (e.g., Anenburg and Katzir 2014;Brearley and Rubie 1990;Castro et al 2000;Dyck et al 2019;Gardien et al 1995;Michaud et al 2021;Patiño Douce and Harris 1998;Storre 1982) and…”

“…(iii) fluid-absent biotite and amphibole dehydration melting at higher temperatures, in the range of 850 to 900 °C (e.g., Michaud et al 2021;Patiño Douce and Beard 1995;Peterson et al 1991;Pickering and Johnston 1998;Sallet et al 2015;Skjerlie and Johnston 1993;Thompson 1982;Vielzeuf and Holloway 1988) Fluid-absent melting reactions by dehydration of micas (and amphibole) implies a potential fractionated OH-F-Cl release from their hydroxyl site to the melt. Consequently, the residual and neo-formed hydroxyl bearing phases may acquire different OH-F-Cl compositions (e.g., Fink and Thompkins 2017;Hansen and Harlov 2007;Peterson et al 1991;Pickering and Johnston 1998;Sallet et al 2015Sallet et al , 2018. On the other hand, anatexis under fluid saturation by external influx at near eutectic temperatures may allow the micas to remain stable while quartz + feldspars experience partial melting (Weinberg and Hasalovà 2015, and references therein).…”

“…In this study, we experimentally investigated the geochemical behavior of F in peraluminous leucogranites and pegmatites (e.g., Nabelek 2019) during the anatexis of twomica protoliths. Attempts to characterize the Cl content yielded consistently low Cl contents near the detection limit of standard analytical methods (Sallet et al 2015(Sallet et al , 2019. The experiments aimed to determine how F partitions between mica and melt during anatexis.…”