TECTONIC EVOLUTION OF THE TETHYAN MARGIN OF GONDWANA FROM NE AFRICA TO THE ZAGROS AND ITS RAMIFICATIONS FOR THE ZAGROS COLLISION - A DETRITAL ZIRCON (U-TH)/HE THERMOCHRONOMETRY PERSPECTIVE

Much of the recent debate and advancement in understanding collisional tectonics in the Zagros has focused on the timing and the structural style of collision between Arabia and Eurasia. In trying to understand the Zagros collision belt, one must examine the inherited architecture of the leading edge of the Arabian plate and its long-lived tectonic evolution as part of the Peri-Gondwanan margin and as a rifted and passive continental margin along the southern margin of Neo-Tethys. This study presents zircon (U-Th)/He (ZHe) age data from the central Neo-Tethyan margin of Gondwana stretching from NE Africa to the Zagros with the aim of elucidating the complex Paleozoic and Mesozoic tectonic and thermal evolution and better understanding the ramifications of inherited structural architecture for the Zagros collision. In contrast to the Zagros, the Neo-Tethyan margin of NE Africa preserves a Paleozoic and Mesozoic tectonic architecture not overprinted by continent-continental collision. ZHe ages from early Paleozoic strata exhibit cooling from >200˚C during Carboniferous block faulting, whereas unreset detrital ZHe ages from Mesozoic and Cenozoic strata record nearly the entire tectonic and thermal evolution of NE Africa, from Ordovician unroofing, major Carboniferous block faulting, Triassic/Jurassic rifting, to Santonian inversion. ZHe data from Sinai and northern Saudi Arabia show similar age patterns dominated by 320-280 Ma and 210-170 Ma populations, reflecting the widespread tectonic effects of Carboniferous block faulting and Neo-Tethyan rifting. Evidence for N-S oriented Carboniferous block faulting is also ubiquitous in the subsurface of NE Saudi Arabia, controlling pre-Permian deposition in N-S trending grabens or wrench-dominated basins. ZHe data from Paleozoic and Mesozoic rocks in the Zagros share the same two major age populations of 350-300 and 210-180 Ma with above discussed regions along the central Neo-Tethys. While these ages do not yield any information on the timing of the Zagros collision, these ZHe results show that the colliding Arabian margin shares the complex structural evolution and anatomy of the adjacent Neo-Tethyan margin and underlines the potential impact of inherited Paleozoic and Mesozoic structures on the tectonic evolution of the continental collision in the Zagros.