The study of morphology and formation mechanism for tourmaline nodules of aplites from Khaku area (Hamedan) with using fractal and three dimensional analysis

In aplites of Khaku area, located in the east of the Alvand body, tourmaline nodules with spherical and dendritic shapes are dispersed. Some of these nodules have light halo that is actually a transition zone between the core of nodules and host aplites. Geometrically these nodules are fractal shapes. In these nodules fractal dimension vary from 1.46 in dendritic nodules to 1.92 in spherical nodules. In three dimensional reconstructions of the studied nodules average volume for core is 34% and for the margin of nodule is 66%. Based on evidence such as lack of veins between nodules, tourmalines with anhedral forms, presence of a leucocratic halo in the aureole of some nodules, their spherical shape, their linear and flow dispersion in the host rock these nodules have been crystallized in magmatic condition. In the final stages of magma crystallization by increasing the amount of B and starting of unmixing in the melt, distinct spherical bubbles have been made which then have been converted to nodules. Magmatic system acts as chaotic systems and presence of rotational and limited closed areas beside areas with disturbed paths lead to the formation of rounded and dendritic nodules beside each other.