15 research outputs found
Two-billion-year granulites in the late Precambrian metamorphic basement along the southern Peruvian coast
Catazonal Xenoliths in French Neogene Volcanic Rocks: Constitution of the Lower Crust. 2. Chemical Compositions and ConseÂquences of the Evolution of the French Massif Central Precambrian Crust
High temperature-low pressure Cretaceous metamorphism related to crustal thinning (Eastern North Pyrenean Zone, France)
Pinite and Pseudo-"Glass" in High-Grade Metamorphic Gneisses. A Discussion of: "Biotite Melting in High-Grade Metamorphic Gneisses from the Haut-Allier (French Massif Central)"
Petrology and Geochemistry of Granulite Xenoliths from Central Hoggar (Algeria) -Implications for the Lower Crust
Thermal interaction of middle and upper crust during gneiss dome formation: Example from the Montagne Noire (French Massif Central)
International audienceThis paper aims to decipher the thermal evolution of the Montagne Noire Axial Zone (MNAZ,southern French Massif Central) gneiss core and its metasedimentary cover through determination ofP–T paths and temperature gradients. Migmatitic gneiss from the core of the dome record a clock-wise evolution culminating at 725 25 °C and 0.8 0.1 GPa with partial melting, followed by adecompression path with only minor cooling to 690 25° C and 0.4 0.1 GPa. Field structuralanalyses as well as detailed petrological observations interpreted in a petrogenetic grid indicate thatthe cover sequence experienced LP-HT metamorphism at <0.4 GPa. Apparent thermal gradientswithin the cover were determined with garnet–biotite thermometry and Raman Spectroscopy on Car-bonaceous Matter. High-temperature apparent gradients (e.g. 530 °C km1 along one transect) areexplained by late brittle–ductile extensional shearing evidenced by phyllonites that post-date peakmetamorphism. In areas where normal faults are less abundant and closely spaced, gradients of 20to 50 °C km1 are calculated. These gradients can be accounted for by a combination of domeemplacement and ductile shearing (collapse of isotherms), without additional heat input. Finally, thethermal evolution of the MNAZ is typical for many gneiss domes worldwide as well as with otherLP-HT terranes in the Variscides