Time and mode of exhumation of the Cordillera Blanca batholith (Peruvian Andes). Issue 8 (29th August 2016)

• Record Type: Journal Article
• Authors: Margirier, Audrey; Audin, Laurence; Robert, Xavier; Herman, Frédéric; Ganne, Jérôme; Schwartz, Stéphane
• Is Part Of: Journal of geophysical research. Volume 121:Issue 8(2016:Aug.)
• Page Start: 6235
• Page End: 6249
• Publication Date: 2016-08-29
• Subjects: amphibole thermobarometry -- normal fault -- plutonism -- glacial erosion -- Andes -- Cordillera Blanca; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1002/2016JB013055
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: The Cordillera Blanca batholith (12–5 Myr) forms the highest Peruvian summits and builds the footwall of the Cordillera Blanca normal fault (CBNF). Even if several models have been proposed, the processes driving both the exhumation of the Cordillera Blanca and extensional deformation along the CBNF are still debated. Here we quantify the emplacement depth and exhumation of the batholith of the northern Peru arc from the late Miocene to present. Based on a compilation of crystallization ages and new thermobarometry data in the Cordillera Blanca batholith, we propose that the batholith was emplaced at a depth of ~3 km in successive sills from 14 to 5 Ma. By contrast, the younger rocks exposed at the surface were emplaced the deepest (i.e., ~6 km) and are located close to the CBNF, suggesting post 5 Ma tilting. Furthermore, a formal inversion of the thermochronologic data indicates an increase of the exhumation rates in the Cordillera Blanca during the Quaternary. The higher predicted exhumation rates correlate with areas of high relief, both in the northern and central part of the Cordillera Blanca, suggesting that Quaternary valley carving by glaciations have a significant impact on the latest stage of the Cordillera Blanca exhumation (2–0 Ma). Key Points: First thermobarometry data in the Cordillera Blanca batholith indicates its emplacement in the upper crust (6–3 km) by sill underplating Tilting of the Cordillera Blanca batholith, footwall of the Cordillera Blanca normal fault Acceleration of exhumation rates over the past 2 Myr in the Cordillera Blanca synchronous with glaciations