GEOCHEMISTRY OF THE NICARAGUAN VOLCANIC ARC: INSIGHTS INTO SLAB BREAK-OFF PROCESSES?

Slab break-off typically occurs at the transition between oceanic and continental lithosphere when the dense subducting slab detaches or tears, particularly in the final stages of ocean closure and subsequent continental collision. However, evidence of slab break-off events occurring in the subduction phase of orogenic development and in the geologic past are difficult to identify in the rock record and our understanding of the geodynamic evolution of slab break-off magmatism remains poorly understood.

Tomographic imaging shows a possible slab break-off occurring beneath a section of the Central American volcanic arc in Nicaragua. This potential break-off event is enigmatic in that slab break-off is occurring during active ocean closure and provides an excellent laboratory to study the space-time evolution arc magmatism and possible pre-collisional slab break-off processes.

To investigate these relationships, mafic samples were collected from eight different volcanic centers along both the modern arc and the older inactive arc in Nicaragua. These samples were analyzed for whole-rock and trace element geochemistry along with Sr-Nd-Hf isotopic analyses to determine source characteristics. Here we present and discuss preliminary geochemical data and discuss its potential relationship to the Cenozoic evolution of the subducting slab in the Central American Volcanic arc.