GSA 2020 Connects Online

Paper No. 98-6
Presentation Time: 6:30 PM

EARLY MIOCENE MAGMATISM ALONG THE WESTERN CORDILLERA OF COLOMBIA SOUTH OF 4 DEGREES N: ARC INITIATION AFTER FARALLON PLATE BRAKE UP?


BARBOSA-ESPITIA, Ángel A.1, FOSTER, David A.2, RESTREPO-MORENO, Sergio A.3, KAMENOV, George D.2 and PARDO-TRUJILLO, Andrés4, (1)Departamento de Ciencias Geológicas, Instituto de Investigaciones en Estratigrafia, Universidad de Caldas, Calle 65 # 26-10, Manizales, Colombia; Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611, (2)Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611, (3)Departamento de Geociencias y Medio Ambiente, Universidad Nacional de Colombia, Facultad de Minas, Medellin, 050040, Colombia, (4)Departamento de Ciencias Geológicas, Instituto de Investigaciones en Estratigrafia, Universidad de Caldas, Calle 65 # 26-10, Manizales, 170004, Colombia

The Western Cordillera of Colombia is made up of allochthonous crustal blocks of oceanic affinity associated with the Caribbean Large Igneous Province. South of 4°N, the Western Cordillera is intruded by a series of poorly studied plutonic bodies that might record the initial-derived magmatism after the breakup of the Farallon Plate during Oligocene-Early Miocene times. Zircon U/Pb geochronology, geochemistry, and isotopic (zircon Hf and whole-rock Pb, Sr, Nd) data were used to study the origin of four of these plutons. These data show a magmatic pulse during Early Miocene with typical magmatic-arc trace elements patterns, ie. negative Nb and Ta anomalies, and high LREE/HREE. Isotopically, Pb, Sr, and Nd values are similar to those of the Caribbean Large Igneous Province and the Active Central American Arc. Hafnium isotopic values show a juvenile magma source (+7 to +12 εHf). These data suggest that the initial record of magmatism in the Western Cordillera started at ~22 Ma, after a period of magmatic quiescence, just a few million years after the Farallon Plate split up and formed the Nazca and Cocos plates, establishing the modern subduction setting for the Northern Andes.