The genesis of fluorite veins in Gabal El Atawi granite, Central Eastern Desert, Egypt

Abstract

Quartz-fluorite-calcite veins were deposited by hydrothermal solutions along structures in Gabal El Atawi granitic pluton. The present investigation aims to study the geochemical characteristics and petrogenesis of Gabal El Atawi fluorite veins. Micro-inclusions data in fluorite veins were obtained and integrated with the available geological, mineralogical and geochemical data to yield information on the genesis of the mineralization as well as the evolution of the mineralizing fluids. Fluid inclusions studies reveal that the fluorite precipitated from saline (up to 22 equiv. wt % NaCl) H2O–NaCl-CaCl2 solutions at homogenization temperatures (Th up to 220 °C). The close spatial relationship between fluorite veins and the granitic rocks, the structural control of the veins, the presence of fluorite and tourmaline as accessory minerals in the granite, the high fluorine concentration in the granite, the REE normalized pattern and the formation conditions of fluorite imply a magmatic origin of hydrothermal fluids which formed the fluorite veins. The source of the fluorite veins is the same magma chamber that supplied the granitic magma i. e. co-magmatic. The ore fluids were released as a result of late-stage differentiation, forming fluorite veins along faults and shears.