STRUCTURAL ANALYSIS OF PELAGONIAN NAPPES OF THE KORABI ZONE, ALBANIA – PRELIMINARY RESULTS AND POSSIBLE IMPLICATIONS FOR THE MIRDITA OPHIOLITE OBDUCTION

The Albanides are part of the Dinaro-Hellenides alpine collisionnal belt which has experienced a multiphase geodynamic evolution. The internal Albanides consist of imbricated Pelagonian nappes that show a mid-Jurassic deformational event related to ophiolite obduction, followed by the development of a Cenozoic Alpine fold-and-thrust belt in the external zones. In NE Albania, there is a series of Pelagonian nappes, making up the Korabi Zone which occurs structurally below the Mirdita ophiolite, a 10 to 15 km-thick slab of Jurassic oceanic lithosphere that escaped major Alpine deformation/metamorphism and represents the largest European ophiolitic complex. The Korabi Zone consists of Paleozoic (Hercynian) basement rocks unconformably overlained by a Permo-Triassic to Jurassic cover sequence of rift-related siliclastic and volcanic rocks that grade upward into a sequence of platform carbonates. One major problem of the Balkan geology concerns the tectonic setting of the Mirdita ophiolite: is it the remnant of a small oceanic basin obducted eastward and slightly thrusted over the Korabi Zone from the West? Or is it rooted into the Vardar Zone (a major intracratonic suture of former Yuguslavia), in which case the ophiolite was obducted westward and thrusted over the Korabi Zone from the East? In order to better understand the kinematics of ophiolite obduction, a structural and metamorphic study of the overthrusted continental margin (i.e. the Korabi Zone) has been initiated in the Kukes area of northeastern Albania. The Korabi Zone can be divided into two subzones: the Korabi (sensu stricto) and the Gjegjane subzones that are separated by a steeply west-dipping series of Neogene (?) normal faults. Metamorphism of the Korabi Zone does not exceed greenschist-grade facies, except for the amphibolitic metamorphic sole of the Mirdita ophiolite in the Gjegjane subzone. In both zones, a NE-SW trending D1 event of deformation, inferred to be obduction-related, is marked by NW-verging isoclinal folds and thrust faults which are locally associated with the overthrusting of Paleozoic basement rocks onto the Mesozoic cover sequence. NE-SW trending Alpine (?) F2 folds, with NW-dipping axial-planar crenulation cleavages, are superimposed onto F1 folds.