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Geology and genesis of vein-type corundum deposits in the Hafafit-Nugrus area, South Eastern Desert, Egypt

Mahmoud Soliman Abu Elatta A., Ali Hani H.

Geologos

2020

Vol. 26, No. 3

181--197

Unusual deposits formed by corundum are described from two separate pegmatitic veins in the Hafafit-Nugrus area of the South Eastern Desert of Egypt. Other related minerals are described too. The vein-type of corundum at Locality 1 (Vein 1) crosscuts through exposed rocks of an ophiolitic mélange, whereas at Locality 2 (Vein 2), it crosscuts through exposed serpentinised ultramafic rocks. The main minerals in Vein 1 are plagioclase, corundum, grossular, phlogopite, muscovite and clinochlore, while almandine, xenotime-(Y), allanite-(Ce), zircon, Cr-rich spinel, apatite, titanite, fergusonite-(Y), meta-ankoleite, U-rich thorite (uranothorite), carbonate and illite are the accessories. In Vein 2, the main minerals are plagioclase, corundum, phlogopite and chlorite, while clinochlore, euxenite-(Y), Nb-rich rutile, almandine, xenotime-(Y), allanite-(Ce), zircon, spinel, apatite, titanite, kasolite, dickite, illite, carbonate, antigorite and talc are accessories. The two types of corundum veins differ in their concentrations of Th, U, Zr, Nb, Ta, REE, Y and Li in wholerock compositions. Field observations, mineralogy and chemical analyses of samples from the two veins of corundum deposits, as well as concentrations of chromophore elements in corundum crystals, suggest metasomatic origins. The present study suggests that the two types of corundum veins formed at different ages from different residual magmas that underwent in-situ hybridisation with the host rocks.

Wykorzystanie mikrospektralnej analizy laserowej w badaniach petroarcheologicznych niektórych narzędzi kamiennych bez ich uszkodzenia

Majerowicz A., Siagło H.

Przegląd Geologiczny

2004

Vol. 52, nr 7

579--580

This paper presents the results of microspectral laser studies of 24 stone tools mainly made of mafic amphibolites and ultramafic serpentinites. Regularities in the occurrence of chromium and titanium in the accessory minerals of these rocks were used. The method applied helps to identify the material the prehistoric tools and artifacts, without their damage. This method is useful in the studies of well preserved objects with smoothly polished surface or covering with a thin weathering patina.