Intra-basin Early Miocene volcanism at the Northern Puna-Eastern Cordillera boundary, province of Jujuy, Argentina

Abstract

The limit between the Puna and the Eastern Cordillera is an area of geological complexity where Cenozoic tectonic, volcanic and sedimentary processes overlap. In this contribution, we describe the Early Miocene volcanic and subvolcanic manifestations located on the border between Northern Puna and Eastern Cordillera, analyzing their relationship with the foreland basin sedimentary succession. We present a new age of 17.94 ± 0.17 Ma (40Ar/39Ar hornblende) for the volcanic rocks, located in the middle Member of the Moreta Formation, as well as new geochemical analysis, showing andesitic-trachydacitic compositions belonging to the high K-calcalkaline series. In addition, we have studied the subvolcanic bodies intruded in the Río Grande Formation, from we which propose an early post-depositional emplacement. In both cases, we present brief considerations about the chemical composition of both study sites, since in the case of Moreta Formation the rocks are high K-calcalkaline andesites while in the case of Río Grande Formation, they are somewhat more undersaturated in silica and enriched in K (shoshonitic series). The new data we presented evinces an event of intra-foreland basin volcanism, mafic to intermediate in composition, at 18 Ma in the Northern Puna-Eastern Cordillera transition.