Empirical constraints on thermal processes in the deep crust of magmatic arcs: Sierra de Fiambala, northwestern Argentina

The Sierra de Fiambala, northwestern Argentina, exposes deep crustal igneous and metasedimentary rocks. Field mapping in conjunction with structural, metamorphic, and geochronologic data document multiple episodes of deformation, metamorphism, and intrusion during the Paleozoic. Metamorphism accompanied by intrusion and injection migmatization affected all rocks in the Cambrian at 550 to 540 Ma. A subsequent event in the Ordovician (;The Fiambala gabbronorite was emplaced at 7 to 8 kb during regional amphibolite facies metamorphism in the Ordovician (;U-Pb data from zircon and monazite indicate that partial melting and granulite formation occurred in less than 10 My between 515 and 505 Ma. In contrast, regional amphibolite-facies metamorphism lasted for 75 to 100 My. The long duration of regional amphibolite-facies conditions in contrast to the short duration of contact granulite-facies conditions is the basis for a conceptual model of metamorphism in the deep crust. "Regional" heating with a duration of 50 to 150 My reaches amphibolite-facies conditions. Granulite-facies metamorphism occurs for short periods of time (...