A tectonic model for the juxtaposition of granulite- and amphibolite-facies rocks in the Eburnean collision in the orogenic belt (Sassandra-Cavally domain, Côte d’Ivoire)

The Sassandra-Cavally (SASCA) domain (SW Côte d’Ivoire) marks the transition between Archaean Kenema-Man craton and Palaeoproterozoic (Rhyacian) Baoule-Mossi terranes. It is characterized by tectonic juxtaposition of granulite-facies amphibolite-facies rocks. Migmatitic grey gneisses, garnet-cordierite-sillimanite migmatitic paragneisses garnet-staurolite-bearing micaschists reached peak pressure conditions ranging from ~6.6 kbar at 620°C to ~10 820°C. These are associated with first recorded deformation D1 correspond a Barrovian geothermal gradient ~25°C/km. Subsequent exhumation, second D2, was marked decompression followed cooling along apparent gradients ~40°C/km. A D3 phase folding local transposition regional S1/S2 foliation E-W trending shear zones. LA-ICP-MS U-Pb dating monazite, which displays complex internal structures, reveals four age groups as function their textural position: 1) Rare relictual zones yield dates Archaean-Palaeoproterozoic (c. 2400–2600 Ma); 2) cluster centered c. 2037 Ma. This includes crystals located in S2 gneiss, suggests that this for D2 exhumation; 3) 2000 Ma, 4) spreading 1978 1913 documented time West African Craton monazites. ages latter two similar ones identified Guiana Shield, could be attributed disturbance fluids, periodic opening system or an episodic crystallization monazite during slow lasting several tens Myrs. data bring new petro-tectonic geochronological constraints on contact Rhyacian terrains nucleus, confirm collisional character polyphase tectono-metamorphic evolution SASCA Eburnean orogeny. They suggest transitional regime predominance gravitational instabilities modern plate tectonics. exhumation granulite- rocks results combination crustal-scale lateral flow transcurrent zones, would explain significantly different P–T conditions.