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The Dineibit El-Qulieb Leucogranite exhibits most features of I-type granitoids (calc-alkaline affinity, relatively high Na2O, moderate values of Rb, Ba, LREE, Rb/Sr and low Rbi Ba with the presence of magnetite and titanite as the main accessories). On the other hand, they possess hyperaluminous (molar A/CNK = 1.22-1.43) and high normative corundum (similar to 5%), which are in contrast to typical I-type granitoids. The REE patterns are characterised by fractionated LREE and relatively flat HREE with pronounced negative Eu anomalies. The investigated rocks have low K/Rb and high Zr/Y ratios reflecting a typical mature continental-arc environment.

The absence of recrystallised phases and the undepleted and flat HREE of the Dineibit El-Qulieb Leucogranite pattern argue against its formation by partial melting of crustal materials. Based on the petrological and geochemical features, the Dineibit El-Qulieb Leucogranite can be generated by fractional crystallisation of mafic magma. The Qulieb leucogranites are characterised by LILE enrichment, normative corundum-rich, strongly peraluminous compositions and associated with miarolitic cavities and pegmatitic patches suggesting the role of the aqueous fluids released from the downgoing slab during subduction. The main fractionating phases were hornblende, biotite, plagioclase and alkali feldspars. Based on the modelling of major elements, the least differentiated adamellite sample requires 91% crystal fractionation, mainly of hornblende, plagioclase, K-feldspar and biotite, from dioritic liquid. On the other hand, the most felsic investigated adamellite sample can be generated by 29% fractional crystallisation of plagioclase, K-feldspar and biotite from the most basic adamellite sample. (C) 1999 Elsevier Science Limited. All rights reserved.