Petrological and mineralogical characterization of Wadi Ghadir pegmatite, southern Eastern Desert, Egypt.

Abstract

Wadi Ghadir pegmatite bodies are represented by two bodies (large and small), which crossed by latitude 24°48'28.83"N and longitude 34°52'38.43"E, and latitude 24°48'25.75"N and longitude 34°52'46.65"E respectively. They are hosted by monzogranites. They consist of a) wall zone in the form of thin and discontinuous, b) the intermediate zone is mainly composed of K-feldspars. It shows sharp contact with wall zone and gradational contact with core zone and c) quartz core which encloses isolated flakes of muscovite. The separated heavy minerals are magnetite, garnet, zircon, rutile, monazite, uranothorite and gold element (i.e. NYF-type). The presence of garnets could be attributed either to the assimilation from country rocks or to crystallization from volatile-rich magma. Gold is restricted to the associated quartzveins; this may refer to relation of gold to the monzogranites. Fluid inclusions are mainly represented by primary two-phases and two generations secondary inclusions. The early fluid generation is higher in temperature and salinity relative to the late one. The calculated conditions of trapping at temperature 360 o C, and pressure up to 2585 bars for the early generation, and 170 o C, 139 o C for the late. The trapping conditions for immiscible fluids that of H2O -and CO2-rich inclusions are temperatures range (170 -400 °C) and pressures (900-2000 bars). As a result of investigation of chemical composition for K-feldspar samples and performed physical parameters tests, the studied pegmatites fit well of wall rather than floor ceramic tiles. Wadi Ghadir NYFpegmatites are interpreted as deriving from mantle-sourced anorogenic granitic magmas with peralkaline singnature.