Authors : B.N.A. Shalaby, M.S. El-Maghraby, A.O. Mashaly and A.K.A. Salem
Abstract: Gabal Abu Hibban, Southwest of Port Qusseir is represented mainly by trachytic rocks in the form of lava flows, sheets, dykes and sills. Petrographically, these rocks are composed mainly of sanidine and albite phenocyrsts with less frequent aegerine and aegerine augite in addition to sodic amphibole, zircon and biotite. The amount of quartz varies greatly from 0% up to 12% of the rock volume. Geochemically, trachytes from Gabal Abu Hibban exhibited a remarked alkaline-peralkaline, meta-aluminous nature as revealed from agpaitic index, feldspathoid silica saturation index, modified alkali-lime index and the aluminum saturation index. Based on CIPW norms, Abu Hibban Trachytes (AHT) comprise nepheline normative and quartz normative varieties. These trachytes were derived from more basic alkali rich magma had undergone fractionation giving rise to more fractionated trachytic rocks. Variation diagrams and elemental ratios revealed a combined role of fractional crystallization and crustal contamination affected the differentiation trends between nepheline normative trachytes and quartz normative trachytes. Abu Hibban Trachytes (AHT) erupted within continental plate, characterized by enrichment in immobile elements; Zr, Y, P and Ti and depletion in mobile elements; Sr, Ba, Rb and K with respect to that formed within oceanic plate. Such variations between the two suites reflect the role of the subcontinental lithosphere in the continental rift zones. Assessment of the possibility of utilization of nepheline as well as quartz trachyte as a flux comparable with the widely used K-feldspar was performed based on the chemical and mineral compositions of the trachytes. The melting behaviour of the trachyte as well as the K-feldspar cone samples were tested after firing for 1 h at 1100 and 1200°C. Solid-phase composition of the samples was semi-quantitatively determined using XRD. Nepheline as well as quartz normative trachytes exhibited melting point lesser than K-feldspar and a completely liquid phase was formed on firing at 1200°C, this indicates that the present trachyte can partially or completely replace K-feldspar in the ceramic mixture as a flux.
B.N.A. Shalaby, M.S. El-Maghraby, A.O. Mashaly and A.K.A. Salem, 2017. Geochemical Characterization of Trachytic Rocks at Gabal Abu Hibban, Central Eastern Desert, Egypt and Their Suitability as a Flux in the Ceramic Industry. Research Journal of Applied Sciences, 12: 242-253.