Structural geology, single zircon ages and fluid inclusion studies of the Meatiq metamorphic core complex: Implications for Neoproterozoic tectonics in the Eastern Desert of Egypt

The Meatiq metamorphic core complex (MMCC) formed during the Precambrian as a result of multiple deformation and metamorphism in the Eastern Desert of Egypt. Structural, geochronologic, and fluid inclusion microthermometric a nalyses reveal a long formation/deformation history for the MMCC. This star ted with the break-up of Rodinia at ca. 800 Ma and continued until Pan-Afri can collision at ca. 580 Ma. Between 800-780 Ma, rifting continued into sea floor spreading and oceanic crust formation. Synchronously, the Um Ba ' an ib granite intruded into an approximately 1.14 Ga old crust comprising migm atic amphibolites. Rifting was accompanied by the deposition of quartz- and mica-rich sediments. Between 660 Ma and 620 Ma, convergence between East a nd West Gondwanaland caused burial of sediments to a crustal depth of appro ximately 20 km and intrusion of calc-alkaline rocks. Subsequently, the meta -sediments were thrust across the Um Ba ' anib granitoid. Deformation of bo th rock units took place under amphibolite-facies metamorphic conditions. F luid inclusions with moderate density provide evidence for the retrograde s tage of this metamorphic event. Continued oblique convergence between East and West Gondwanaland resulted in a transpressional regime with displacemen t partition. While nappe stacking continued in foreland domains, the MMCC w as exhumed to a depth of 12-15 km in hinterland domains. Extension-related granitoids were emplaced between 620 and 580 Ma. Microthermometric analyses of fluid inclusions suggest a crustal depth of approximately 10-12 km for the transpressional event. Rapid exhumation was accompanied by detachment o f the cover nappes and emplacement of syn-tectonic intrusions, which caused local contact metamorphism. Low-density fluid inclusions document high-T, low-P conditions for the contact metamorphism. The final stage of exhumatio n took place under brittle/ductile conditions at a crustal depth of approxi mately 3-6 km indicated by water-rich fluid inclusions. The age of this eve nt is constrained by the intrusion of the late- to post-tectonic Arieki ada mellite at approximately 580 Ma. (C) 2001 Elsevier Science B.V. All rights reserved.