Genesis and petrology of Late Neoproterozoic pegmatites and aplites associated with the Taba metamorphic complex in southern Sinai, Egypt
We present new field, petrographical, mineralogical and geochemical data from late Neoproterozoic pegmatites and aplites in southern Sinai, Egypt, at the northernmost limit of the Arabian-Nubian Shield. The pegmatites cross-cut host rocks in the Taba Metamorphic Complex (TMC) with sharp contacts and are divided into massive and zoned pegmatites. Massive pegmatites are the most common and form veins, dykes and masses of variable dimensions; strikes range mainly from E-W through NW-SE to N-S. Mineralogically, the massive pegmatites are divided into K-feldspar-rich and albite-rich groups. Zoned pegmatites occur as lenses of variable dimensions, featuring a quartz core, an intermediate zone rich in K-feldspars and an outer finer-grained zone rich in albite. All compositions are highly evolved and display geochemical characteristics of post-collisional A-type granites: high SiO_2, Na_2O+K_2O, FeO*/MgO, Ga/Al, Zr, Nb, Ga and Y alongside low CaO, MgO, Ba and Sr. They are rich in Rare Earth Elements (REE) and have extreme negative Eu anomalies (Eu/Eu*= 0.03–0.09). A genetic linkage between the pegmatites, aplites and alkali granite is confirmed by their common mild alkaline affinity and many other geochemical characteristics. These pegmatites and aplites represent the last small fraction of liquid remaining after extensive crystallization of granitic magma, injected along the foliation and into fractures of the host metamorphic rocks. The extensional tectonic regime and shallow depth of emplacement are consistent with a post-collisional environment.
© 2016 University of Barcelona. This work is licensed under a Creative Commons Attribution-ShareAlike License. Manuscript received January 2016; revision accepted March 2016; published Online June 2016. We are indebted to King Saud University, Deanship of Scientific Research, Research Group Nº RG-1436-036, for their support. MKA's visit to the Division of Geological & Planetary Sciences, California Institute of Technology, USA, was supported by the Cairo Initiative of the US Agency for International Development. Special thanks to Prof. George Rossman and Michael Baker for use of sample preparation facilities at Caltech. Also, the authors would like to thank Chi Ma for his help with the microprobe analyses. The authors highly appreciate thoughtful reviews by the Editor (Antonio Castro), Yaron Be'eri-Shlevin and Alexander Falster, which improved the manuscript.
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