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Earth Sciences Laboratory, National Research Centre, Dokki, Cairo, Teachers Institute of Education, El-Odylia, Kuwait, and Teachers Institute of Education, El-Shamia, Kuwait

ABSTRACT

The formation of elbow twin in the examined zircons suggests that they were crystallised from a melt which shows a sudden variation in the rate of crystallisation. The presence of parallel growth in these zircons suggested that a high proportion of zircons was crystallised early from a low viscous melt which permitted the movement and collision of growing zircon crystals. Necked zircon crystals are observed in some granites which indicate that a process of dissolution took place through a late stage of chemical corrosion during the formation of Ras Barud granites. The zircons of the examined granitic rocks are characterised by sharply bounded euhedral crystals, uniformity in crystal morphology and the elongation ratios which are mainly above two. It is evident that the previous characters of the zircons mainly suggest the magmatic origin of the host granites of Ras Barud area.