Syn-tectonic Dipilto Batholith (NW Nicaragua) Linked to Arc-Continent Collision: High- and Room-Temperature AMS Evidence

The northern Central America region (Honduras and Nicaragua) is characterized by geotectonic units delimited by strike-slip fault systems and shortening zones of poorly constrained ages. The eastern portion of the Chord's block, named the "Dipilto micro-block" or "Patuca" is one of these units that besides with the Siuna Serpentinite Melange, provides evidence for Early Cretaceous arc-continent collision. Nevertheless, within the Dipilto micro-block is the Early Cretaceous Dipilto batholith (NW Nicaragua), an Ilmenite-Series granitoid suites whose emplacement tectonic setting is unknown. We document the room- and high-temperature anisotropy of magnetic susceptibility (RT-AMS and HT-AMS) and hysteresis cycles from 31 sites in the Dipilto batholith and cross-cutting dikes as well as the oxide mineral microscopy of main lithologies. This is to investigate the magmatic fabric in the granitoids and dikes, and the relation to the emplacement dynamics. The RT-AMS and HT-AMS results show magnetic lineation and foliation (K-max and K-max K-int plane) dominated by paramagnetic minerals (biotite and hornblende). The central parts of the intrusion show a NE-SW K max distribution and sites near to boundary of the country-rock a K-max-K-int plane sub-parallel to the contact. These results and previous structural data in the surrounding Nueva Segovia Schist country-rock support an intrusion emplaced in a contractional setting concurrent with the batholith's NE-SW regional geometry. The Dipilto batholith age (119-112 Ma) implies a syn-collisional origin that together with our results indicate an Early Cretaceous progressive shortening in the region associated with the Siuna Intraoceanic Arc collision (similar to 134-113 Ma). Furthermore, they indicate that the shortening azimuth (i.e., the direction of tectonic transport) is similar to 127 degrees-137 degrees in its current geographical position, but was 227 degrees-237 degrees in its Early Cretaceous paleo-position, probably related to the final stage of shortening and collision events of the southwestern Mexican paleocontinent.