Tectonic significance of Late Neoproterozoic granites from the Tibesti massif in southern Libya inferred from Sr and Nd isotopes and U-Pb zircon data

The Neoproterozoic crust of the Tibesti massif was stabilized by magmatism that included subduction-generated batholithic suites and post-orogenic granite plutons. All of the magmatism occurred in a period of about 20 million years centered around 550 Ma, and nearly all of the granites have initial Sr-87/Sr-86 ratios of about 0.706. The Wadi Yebigue pluton has U-Pb zircon ages of 563 Ma and 558 Ma on two different phases and epsilon(Nd) at 550 Ma from -0.5 to -2.2. These isotopic data and the geologic history of the massif suggest that granites in the Tibesti massif developed during and shortly after closure of a short-lived ocean basin that developed by fragmentation of pre-existing continental crust of the Saharan region. (c) 2005 Elsevier Ltd. All rights reserved.