Mineralogy and geochemistry of tourmalines in Malmir Area (East of Doroud- Iran)

Malmir area is located in the east of Doroud city, in the Sanandaj-Sirjan metamorphic zone. The earliest deposits contain a relatively uniform sequence of slates and phyllites with silisic veins and veinlet. Various granitoid units, with Middle Jurassic age, are the most important geological event that occurred in the area. Microprobe analyses of tourmalines in pegmatites and and quartz-tourmaline veins show that these tourmalines are schorl-foitite type with dominance of schorl type. Different tourmaline occurrences in the granite units, euhedral forms and absence of chemical zoning, high Fe/Fe+Mg, deficiency in X sites and high Al contents are recognizable in most tourmalines and display their magmatic origin. Therefore, the tourmalines in Malmir area are depended on granite environment and were formed by hydrothermal source of magma. This study shows that the relative amount of Fe# is high and the tourmaline formation area is close to the fluid feed source and the low distance to the intrusive mass.