Geochemistry, petrogenesis and fluid inclusion studies of the Kadabora granite pluton and associated enclaves, Central Eastern Desert, Egypt.

The studied area is occupied by Neoproterozoic basement rocks comprising  ophiolitic melange, metagabbro-diorite complex, younger granites and post-granite dykes.

Detailed field studies revealed that Kadabora pluton is differentiated into three phases: granodiorite phase I, monzogranite phase II is and finally syeno- alkali feldspar- granite phase III.

Mafic enclaves (ME) with andesitic composition are recorded only in granodiorite phase I and have sharp to diffuse contacts with their host rocks. Macroscopic descriptions indicate that the ME are of magmatic origin.

Geochemistry, The enclaves are calc-alkaline, and formed in island arc and active continental margin. Variation diagrams display that the andesite enclaves (ME ) and the granodiorite phase I are separated from each other with a conspicuous compositional gap which indicate that there are two magmas and probably formed by mingling/mixing process at depth before their emplacement. The granodiorite phase I is calc-alkaline, I-type and formed under the subduction tectonic regime. Phase II falls within the alkaline and  highly fractionated calc-alkaline granites (HFCAG), whereas phase III straddles the boundary into proper alkaline granitoids field. Phase II and III belong to the A₂-subtype granite. This A₂-subtype granite was probably formed in an extensional regime, either concurrent with or subsequent to subduction which can lead to tensional break-up of the crust (i.e. post-collisional, post-orogenic granites). The monzogranite phase II and the syeno-alkali feldspar-granite phase III are probably formed by partial melting of relatively anhydrous lower crust source and/or tonalite to granodiorite is viable  alternative to the granulite source.

Fluid inclusions study revealed that the fluids infiltrated in Kadabora composite granite pluton are dominated by aqueous fluids. These fluids are represented by two-phase inclusions distributed along lines or fluid inclusion planes. In phase I and II only one fluid generation was infiltrated. This fluid is low salinity (1-8 wt.% NaCl eq), and medium temperature (140-250°C) aqueous fluid. In phase III granite, more than one fluid generation was infiltrated in the granite as indicated from petrographic and microthermometric. These fluid generations have wide range of salinity between 1 and 30 wt.% NaCl eq., and temperature between 70 and 380 °C. These fluid generations are consistent with the widespread retrograde alterations observed in phase III granite. Melt inclusions have been also observed in the first and second granitic phases.