TRACKING MESOZOIC ACCRETIONARY DYNAMICS IN THE NORTHERN ANDES OF COLOMBIA THROUGH AR-AR DATING OF SHEAR ZONES AND (U-TH)/HE - FISSION TRACK THERMOCHRONOLOGY OF PLUTONIC MASSIFS (APATITE AND ZIRCON)

The configuration of Northern Andes is closely related to an accretionary orogen, at least since the Mid-Cretaceous. In Colombia, accreted terrenes are mainly of oceanic affinity, including plateau rocks related to Caribbean Plate and volcanic arcs of the Barroso Formation. These rocks were accreted to the pre-Mesozoic margin in Late Cretaceous times along the Romeral Fault System, which had a predominant transpressive, dextral character for the time. The dominant structural style for this orogen along the margin is a west verging thrust system and transcurrent associated faults. Upper Paleozoic medium grade metamorphic rocks from the ancient paleo-margin are thrust over oceanic domains defining a thick-skinned deformational style. These rocks are in turn thrust over other local units including syeno-granites, basic volcanic and ultramafic rocks of the Quebradagrande Formation. In this contribution we present (U-Th)/He data in apatite, FT data in zircon, Ar-Ar results from highly deformed zones and structural and microstructural considerations to spatiotemporally constraint the accretionary dynamics. The main deformational