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

Abstract

In aplites of Khaku area, located in the east of the Alvand body, tourmaline noduleswith spherical and dendritic shapes are dispersed. Some of these nodules have light halothat is actually a transition zone between the core of nodules and the 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-dimensionalreconstructions of the studied nodule, the average volume for the core is 34% and 66%for its margin. Based on evidences such as lack of veins between nodules, tourmalineswith anhedral forms, presence of a leucocratic halo in the aureole of some nodules, theirspherical shape, their linear and flow dispersion in the host rock these nodules have been crystallized in magmatic condition. In the final stages of magma crystallizationand the B content increment followed by beginning of unmixing in the melt, distinctspherical bubbles have been developed which gave rise to nodules formation. Magmaticsystem acts as chaotic systems and the presence of rotational and limited closed areas inthe vicinity of areas with disturbed paths has led to the formation of rounded anddendritic nodules beside each other.

Keywords

• tourmaline nodule
• fluid exsolution
• fractal analysis
• three dimensional reconstruction
• Khaku
• Sanandaj-Sirjan zone