Process of mineral compositional changes during brine activity under upper amphibolite facies conditions

Abstract

Ca. 1cm-thick Grt-Hbl vein discordantly cuts a gneissose structure of a Grt-Opx-Hbl gneiss in the central Sor Rondane Mountains, East Antarctica. Changes of mineral compositions and mineral assemblages with a distance from the vein suggest that the Grt-Hbl vein was formed by NaCl-KCl brine infiltration in open system under upper amphibolite facies conditions. Moreover, Zn-, Sr-, Ba-, Pb-, and U-contents in Hbl and Li-, Sr-, Ba-, and Pb-contents in Pl decrease with a distance from the vein. Trace elements compositional profiles with a distance from the vein imply the elements diffuse from the vein to the wall rock.