Quantifying crustal thickness and magmatic temperatures of the Jurassic to Early Cretaceous North-Andean arc

Abstract

ABSTRACT We characterized the crustal thickness variations and magmatic saturation temperatures of the Early Jurassic to Early Cretaceous (194–130 Ma) plutonic and volcanic rocks of the Northern Andes of Colombia and Ecuador, combining trace elements signatures and zircon and apatite saturation temperatures. Also, we analysed the implications of the emplacement conditions during the last stage of the magmatism using Al-in-hornblende thermobarometry. Moderate rare earth elements (REE) slopes and depleted heavy REE patterns show that the primary residual magma source was amphibole, but plagioclase and pyroxene were also significant residual phases indicating that the magma source was formed in a crust that varied in thickness from 35 to 50 km. According to the La/Yb and Sr/Y crustal quantifications and the REE ratios, two phases in the arc evolution are characterized by a thick crust. The first is in Santa Marta Massif, Upper Magdalena Valley and Garzón Massif (190–180 Ma), which could be associated with shortening or basaltic underplating due to magmatic events. The second one recorded in the Ibagué Batholith (160–154 Ma) is related to the crustal thickening on an oblique subduction setting. During the latter period, the magmatic volumes progressively decreased, as is recorded by saturation temperatures increase. Finally, a thin crust emplaced the last stage of the arc magmatism during the Late Jurassic to Early Cretaceous (154–130 Ma).