Studying the genesis of tourmaline and behaviour of rare earth elements during formation of tourmaline in Shirbit Area (Northeast Ahar, East Azarbaijan)

The Studied area is located in vicinity of the Sherbit village, about 28 km to the northwest of Ahar (in Eastern Azerbaijan province. Quartz monzonite intrusion is the host rock of hydrothermal tourmaline in this area. On the basis of their textural features, the tourmalines can be divided into four groups: 1) tourmaline veins, 2) tourmaline-breccias, 3) massive tourmaline and 4) pore space filling tourmaline. Based on the petrography and electron microprobe analysis studies, tourmalines of Sherbit area are correspond to intermediate schorl-dravite with more tendencies toward dravite composition and have been formed in hydrothermal conditions. According to reasons such as more Mg values compared to Fe, low Al amounts, fine scale zoning, content of fluorine, tendency toward outer side of alkali- and proton-deficient vectors and lack of negative correlation between Fe and Mg. Separated tourmaline from the quartz– tourmaline vein shows a very similar pattern to the quartz monzonite samples, which are characterised by a pattern with depletion in HREEs relative to LREEs. It can be concluded that REE concentrations and patterns of tourmaline from the different studied tourmaline rocks are controlled by the host rock and not by the hydrothermal fluid causing boron metasomatism.