Evolution of arc magmatic cycles from the Carboniferous to the Early Cretaceous in the western paleomargin of Gondwana, north of the Andes

Abstract

This work presents a considerable volume of new and compiled data indicating that arc magmatism in the western paleomargin of Gondwana began in the Carboniferous and continued during the Permian and Early Triassic. Subsequently, the magmatism reactivated during the Early and Middle Jurassic due to the subduction of the Farallon Plate under the continental paleomargin. The arc pluton belts are distributed from the edge of the paleomargin toward the interior of the continent in the same orientation as the slab (west–east direction). During the Carboniferous, between ca. 333 Ma and ca. 300 Ma, magmatism formed small calcic metaluminous gabbro and leucotonalite plutons of tholeiitic to calc-alkaline affinity on the western margin of Gondwana. Later, the second belt of arc plutons formed during the Permian/Triassic (between ca. 300 Ma and ca. 234 Ma) and are represented by metaluminous to peraluminous calc-alkaline to high-K calc-alkaline batholiths and stocks of heterogeneous composition (granites, granodiorites, diorites, quartz monzonites, and monzonites), which were intruded by dikes and minor granite bodies during the Middle Triassic. Between ca. 214 Ma and ca. 186 Ma, peraluminous plutons of batholithic dimensions of monzogranitic to syenogranitic composition developed in the back-arc. Between ca. 197 Ma and ca. 186 Ma, back-arc magmatism occurred, while a new magmatic cycle began along the arc axis. At the end of the Jurassic, the magmatic arc cycle ended in the northwestern paleomargin of Gondwana (ca. 164 Ma). The intrusion ca. 159 Ma of porphyritic bodies of alkaline andesitic basalts toward the edge of the continental margin suggests the strangulation and collapse of the subduction zone in the mantle. To the west, off the continental margin, a new arc magmatic cycle began over a different continental terrane ca. 171 Ma and extended to ca. 138 Ma, giving rise to a belt of calcic to calcic-alkaline plutons emplaced in the Ordovician metamorphic (Anacona Terrane), Triassic (Tahamí Terrane), and Upper Jurassic (Tierradentro Orogen) rocks. The assemblage amalgamated to the western margin of Gondwana in this period.