Mineralogical and Chemical Changes Accompanying Greisenization and Albitization of Egyptian Granites PDF

Keywords

albitization, greisenization, granite

Abstract

Albitization and greisenization processes are recognized in certain zones in the tin-bearing granites of the Southeastern Desert of Egypt. These alteration processes are usually followed by hydrothermal activities and are not observed in the non-stanniferous granites. Albitization of of magmatic and/or post-magmatic processes, whereas greisenzation is formed by post-magmatic. Greisenization resulted in the destruction of the feldspars of the granites and the formation of quartz, muscovite, lepidolite, topaz, fluorite and cassiterite. This is accompanied by partial migration of Na, K, Ca, Fe, Ti, Y, Zr, Be and Pb and the addition of Si, F, H2O, Sn and Nb. Albitization is manifested by the growth of fine to medium-grained albite, sometimes with beryl. This is accompanied by the addition of Na, Be, Sn, Nb, Cu, Mo and Bi and partial migration of Si, Fe, Ti, Y and Zr. Fluoride complexing is an important factor in element mobility and transportation during greisenization and albitization. Carbonate and fluoride complexing are the most plausible cause of element mobility in hydrothermal processes giving rise to quartz veins.