2013

Trace elements solubility and partitioning in ZIRCON OF Gabal Bab El-Mekhaniq GRANITES, North Eastern Desert, Egypt

Azza Fahmy

Nuclear Materials Authority, P.O.Box 530 El Maadi, Cairo Egypt

Much attention has been paid to trace elements studies of zircons, because they carry important information such as trace elements solubility and partitioning, which are unobtainable from major phases. The studied zircons were separated from older granitoids and younger granites (monzogranites and syenogranites) of G. Bab El-Mekhaniq at south of Wadi El Atrash were analyzed by electron microprobe analysis.

Electron microprobe analyses show that zircon of younger granites are characterized with higher contents of Al₂O_3, Fe₂O₃, ThO₂, UO_2, HfO₂ and CaO and lower values of ZrO₂ relative to zircon of older granitoids. The higher UO₂ + ThO₂ content and lower ZrO₂ / HfO₂ content in zircons of the younger granites suggest a lower temperatures at which this rock crystallized. The lower temperature has significantly enhanced isomorphic elements to substitute for Zr.

Two types of zircons of the younger granite are recognized. Zircons of type (1) are higher in HfO₂ content than type (2) which are higher in UO₂ + ThO₂ + REE contents. The replacement of Zr by tetravalent cations (Th, U and Hf) interpreted that the trace elements solubility and partitioning in zircon, is favored in the most evolved granites. The enrichment of LREEs may due to subsets of analyses of Type 2 zircons that appear to result from incorporation of mineral inclusions in the analyzed volume.