Metamorphic tourmaline and its petrogenetic significance from the Maramureș Mountains (East Carpathians, Romania)

Abstract This study describes mineralogical and crystallochemical characteristics of metamorphic tourmalines from an Alpine shear zone in a Variscan rock sequence the Maramures region northern part East Carpathians. We use this mineral to unravel aspects evolution tourmaline bearing host rocks compare crystallo-chemical other Alps. Petrographic microstructural observations, as well electron microprobe analyses on several zoned associated minerals (mica, feldspar) mylonitic schist Rebra terrane (Maramureș Mountains), indicate that pre-kinematic belong alkali group (Na dominant), hydroxyl dominated crystallographic W-site can be assigned species dravite schorl. The tourmaline-bearing have metasedimentary protolith. analysed porphyroblasts, rotated by simple shear, show corroded rim are interpreted formed due pressure release. Three main compositional zones were evidenced porphyroblast: core two asymmetrically arranged inclusion-poor/free rims, all pre-alpine prograde conditions. Based relations geothermobarometry (tourmaline–muscovite, tourmaline–plagioclase geothermometry phengite geobarometry), peak conditions investigated evaluated been at temperature ca. 590 620 ± 22 °C P min = 5.5 - 6.0 0.5 kbar. By observing dynamically recrystallized microstructures quartz feldspar 350 400 was estimated paleopiezometry outlined differential stress about 1.5 kbar implied only minor chemical change outer zone.