Magmatic conditions aiding synconvergent extension above the Peruvian flat slab

Author(s)Grambling, Tyler A.
Author(s)Jessup, Micah J.
Author(s)Newell, Dennis L.
Author(s)Grambling, Nadine L.
Author(s)Hiett, Coleman D.
Date Accessioned2024-06-10T18:32:54Z
Date Available2024-06-10T18:32:54Z
Publication Date2024-05-17
DescriptionThis article was originally published in Geosphere. The version of record is available at: © The Authors. Gold Open Access: This paper is published under the terms of the CC-BY-NC license (
AbstractThe Cordillera Blanca and Cordillera Huayhuash contain some of the highest topography in the Andes and provide insight into tectonomagmatic processes associated with the onset of flat-slab subduction. These adjacent ranges shared a similar history of deformation and exhumation prior to the late Miocene, when synconvergent extension began in the Cordillera Blanca. Magmatism in the Cordillera Huayhuash has been inferred as coeval with magmatism in the Cordillera Blanca. Yet, extension, which has been correlated with magmatic heat flow, is limited to the Cordillera Blanca. New zircon U-Pb dates and trace and rare earth element concentrations from the Cordillera Blanca batholith and the Huayllapa pluton in the Cordillera Huayhuash and reassessment of existing zircon data help to characterize regional magmatic processes prior to the establishment of flat-slab subduction. Two compositionally distinct samples of the Huayllapa pluton yielded mean ages of 24.8 ± 0.4 Ma and 25.4 ± 0.8 Ma. In contrast, the Cordillera Blanca batholith has a protracted crystallization history postdating that of the Cordillera Huayhuash by up to 20 m.y. Miocene magmatism in the Cordillera Blanca began at 19 Ma and ended with injection of large volumes of geochemically distinct, mantle-derived magma from 10 to 5 Ma. We suggest that 6–5 Ma magmatism in the Cordillera Blanca promoted elevated heat flow and reduced shear strength, which facilitated extensional shearing along the western slopes of the range, whereas colder amagmatic crust in the Cordillera Huayhuash inhibited southward propagation of faulting. Our data demonstrate that the linkages between magmatism and elevated heat flow identified in the Cordillera Blanca are important driving processes in initiating extension in cordilleran-style orogenies.
SponsorThis research was funded by Sigma Xi Grant-in-Aid of Research G2018031595487456 and a Geological Society of America Graduate Student Research Grant to T. Grambling. Field work and sample collection were made possible by National Science Foundation (NSF) grant EAR-1623034 to D. Newell and NSF grant EAR-1623023 to M. Jessup; analytical work was assisted by NSF grant EAR-1649254 in support of the Arizona LaserChron Center (ALC). Careful and thoughtful reviews by Sarah George, Audrey Margirier, and Snir Attia drastically improved this manuscript. We appreciate the editorial support and insights of Christopher Spencer and Joel Saylor. Conversations with Chris Fedo, Nick Dygert, and Michelle Gevedon were key to exploring the finer points of zircon age distributions and zircon and crustal trace and rare earth element geochemistry controls during development of this manuscript. We thank Alberto Cafferata of Caraz, Peru, for providing field logistical support in the Cordillera Huayhuash and Cordillera Blanca, and to Julio Olaza of Huaraz, Peru, for providing additional transportation and logistical support in the Cordillera Blanca. We are greatly appreciative of ALC staff for hospitality and assistance with sample preparation, analysis, and data handling. Metadata associated with this manuscript can be found in the EarthChem repository at
CitationTyler A. Grambling, Micah J. Jessup, Dennis L. Newell, Nadine L. Grambling, Coleman D. Hiett; Magmatic conditions aiding synconvergent extension above the Peruvian flat slab. Geosphere 2024; doi:
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TitleMagmatic conditions aiding synconvergent extension above the Peruvian flat slab
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