The study of petrography and mineral chemistry in aplite-pegmatites from Simin valley (south of Hamedan)

Aplitic and pegmatitic dykes  exposed in southeast of Hamedan in the Simin area. From the margin to the center of these dykes, two typical textural areas present that obviously indicate effect of crystallization progress: 1- In the marginal zone, fabrics consist of anisotropic textures of the outer zones, including fine-grained units, graphic intergrowths, and unidirectional solidification textures and 2- In the interior zone that have coarse, blocky textures. Microprobe analysis performed on tourmaline, plagioclase and K-feldspar minerals. Tourmalines have schorlite composition. In the FeO/(FeO+MgO) vs. MgO diagram that determine origin of tourmalines, the studied tourmalines have Fe# between 0.8 to 1 that indicates they formed in magmatic conditions and external hydrothermal fluids and don’t take part in their genesis. Compositions of analyzed plagioclases are albite-rich (Ab90-100) and K-feldspars have 92-97 percent K-feldspar. This  indicates  progress of fractional crystallization  which is related to magma. Studied of tourmaline zoning is well visible at thin sections and in the chemical analyses. In the analyzed feldspars, high amount of Rb (1319 ppm) and also Cs (205 ppm) indicate high degree of fractionation which is related to magma.