TECTONIC EVOLUTION OF THE CHORTIS COMPOSITE BLOCK, NORTH-WESTERN NICARAGUA

Many orogens comprise collages of fault-bounded terranes. From a tectonic perspective, the timing of terrane accretion in the orogenic evolution results in protracted mountain building events and marks different stages of the orogenic development. Terranes may record multiple orogenic events and move great distances with the destruction of large tracts of oceanic crust. Typically, terranes accumulate along suture zones at the heart of supercontinents and therefore have the potential to record pre-syn and post collisional tectonic processes. As a result, terranes often have a complex geologic history involving deformation and metamorphism, magmatism and sedimentation and in turn have the potential to record many different geologic processes in space-time.

The geologic and tectonic history of Central America is complex, under-explored and affords a unique opportunity to observe both modern and ancient tectonic processes. The basement of Central America is thought to be comprised of primarily peri-Gondwanan terranes; Oaxaquia, Maya, and Chortis. The Chortis block is a cratonic-type peri-Gondwanan terrane and is commonly included in Neoproterozoic to Paleozoic paleogeographic reconstructions however, its pre-Cretaceous tectonothermal evolution remains largely unstudied. Previously much of the research completed on the Chotis block has concerned its Mesozoic evolution, ignoring its potential to contain a wealth of tectonothermal evolutionary history by recording the geological processes of many supercontinent cycles. We compare in detail the tectonostratigraphy of both the Southern and Eastern components of the Chortis block focusing on its pre-Mesozoic evolution. Detailed structural analysis coupled with field mapping of plutonic, volcanic, and metasedimentary rocks attests to the complexity of the Pre-Mesozoic evolution and the composite nature of the Chortis block. Geochemical data confirms field observation of a previously undiscovered mafic plutonic series within the basement of the South components of the Chortis Block. Preliminary trace element data helps to identify i) the composition of unexposed sections of the Chortis basement ii) assist in the de-lineation of tectonic boundaries between adjacent terranes and iii) help to interpret potential sources for magmatism. Taken together these data contribute to our understanding of the evolution of Peri-Gondwanan terranes in Central America and the tectonic evolution of Nicaragua.