TECTONOTHERMAL EVOLUTION OF THE BADAJOZ-CORDOBA SHEAR ZONE (SW IBERIA) - CHARACTERISTICS AND AR-40 AR-39 MINERAL AGE CONSTRAINTS/

Field characteristics indicate that the Badajoz-Cordoba shear zone has had a long, polyphase tectonothermal evolution. Ar-40/Ar-39 cooling a ges recorded within central, ductile sectors of the Badajoz-Cordoba sh ear zone range from ca. 370 to 360 Ma (amphibole) and 340 to 330 Ma (m uscovite). These are interpreted to date post-metamorphic cooling thro ugh contrasting temperatures required for intracrystalline retention o f argon following a regionally significant Variscan tectonothermal ove rprint. These results combined with field relationships indicate that the Badajoz-Cordoba shear zone experienced at least 15 km of uplift re lative to adjacent areas during late Paleozoic sinistral transpression . The data also indicate that individual structural units within the s hear zone experienced contrasting uplift histories (both in total amou nt and rate). The Ar-40/Ar-39 cooling ages indicate complete Variscan rejuvenation of all older intracrystalline argon systems within centra l sectors of the Badajoz-Cordoba shear zone.