Evidence for transpression during formation of the Candelaria Punta del Cobre IOCG -district and regional implications

Abstract

The youngest and best exposed Iron Oxide Cu–Au (IOCG) deposits currently recognized are found in the coastal belt of the Andes. Their formation has been attributed to back-arc extension or transtension associated with the convergent Andean margin. Here we document transpressional deformation synchronous with Cu mineralization in the Candelaria-Punta del Cobre district, the largest IOCG district of the Andean belt. A northwest-southeast shortening direction is recorded by north-northwest sinistral strike-slip faults that host mineralization, northwest dikes, and north-northeast compressive structures. Batholith emplacement synchronous with mineralization formed a north-northeast oriented foliation zone parallel to the intrusive contact and associated folds in the host rock sequences that face inwards towards the intrusive contact. Age constraints indicate that transpressional deformation in the Cretaceous arc, at least locally, begun earlier than previously documented, and IOCG mineralization may have spanned the transition from extension to the initial phase of compression.