STRUCTURAL ARCHITECTURE OF A LATE TRIASSIC - EARLY JURASSIC, SEA OF JAPAN TYPE BACKARC BASIN OCEANIC LITHOSPHERE IN THE CENTRAL PONTIDES (ANATOLIA)

The Küre ophiolite in the Central Pontides of northern Anatolia is a Penrose-type ophiolite, complete with a sheeted dike complex, and includes well developed, Cyprus-type, volcanogenic massive sulfide deposits (VMS). It is tectonically imbricated along S-directed thrust faults between the Paleozoic, Hercynian basement rocks of the Devrekani metamorphic massif (Eurasia) to the north and the Triassic–E. Jurassic volcanic arc & subduction-accretion units of the Çangaldag Complex to the south. The ophiolite consists of upper mantle peridotites (mainly harzburgite with dunite & minor lherzolite), layered & isotropic gabbros, sheeted dikes, and extrusive rocks composed of pillowed & massive lavas, hyaloclastites and pillow breccias. The extrusive sequence is 2 to 3 km thick & contains stratigraphic intercalations of scaly argillite, black shale, siltstone-sandstone layers, locally 10s to 100s of meters in thickness (Akgöl Formation). Pillowed & massive lava flows are cut by numerous NW–SE-oriented high- to low-angle, mineralized normal faults with down-dip separations of several cm to meters, and are extensively brecciated & cataclastically deformed along these extensional faults. Hydrothermal alteration of volcanic rocks is intensive within discrete zones in the hanging wall fault blocks. Massive & stockwork VMS deposits are concentrated in hyaloclastic & pillow breccias, sealed by argillite layers, at the intersections of NW–SE-striking normal & NNE–SSW-striking oblique slip faults. Extrusive & dike rocks range in composition from basalt, basaltic andesite to trachybasalt, basaltic trachyandesite & dacite with MORB-like & IAT affinities. Sandstone layers in the argillite-shale unit contain detrital material derived from the Hercynian besement. The Küre ophiolite and the overlying hemipelagic–pelitic sedimentary package formed in a Sea of Japan type backarc basin N of the Çangaldag volcanic arc, developed along the late Triassic-early Jurassic active margin of Eurasia.