Significance of the Damara Orogen in Gondwana Assembly: an Evaluation of Detrital Zircon Ages and Isotopic Compositions of Neoproterozoic Metasedimentary Rocks

University Of Florida, Gainesville FL

Investigators

Abstract

Two different hypotheses for the relationship between the Congo and Kalahari cratons, during the Rodinia and Gondwana supercontinent cycles, will be evaluated. Co-funding for this work has been provided by the Office of International Science and Engineering. Congo and Kalahari presently reside within Africa and are juxtaposed across the Neoproterozoic-Cambrian Damara-Lufilian-Zambezi orogenic system. The primary controversy surrounding the assembly of these two cratons in the supercontinent cycle centers on the extent to which Congo and Kalahari remained associated geographically throughout the cycle, i.e., were the two cratons directly adjacent to one another in Rodinia, and, did they remain so until amalgamated in Gondwana, or was one (or both) not in Rodinia at all and were not joined until Gondwana formed? The metamorphosed sedimentary detritus within the Damara orogenic zone records the separation of these blocks from Rodinia and accretion within Gondwana. The U/Pb age and Hf-isotopic compositions of detrial zircons from the metasedimenatry rocks, along with whole-rock Nd isotopes, will be measured to define the origin of the continental detritus in the suture zone. The significance of the alternative hypotheses relates to the configuration of Rodinia, the amalgamation of Gondwana (E-W or N-S final suturing), and the degree to which Rodinia was fragmented during break-up. The accretion and dispersal of supercontinents remains one of the most significant problems in understanding global dynamics and motions of continents through time and the convection of rock in the mantle. The growth and break-up of two supercontinents in late Precambrian time ? Rodinia and Gondwana ? are particularly significant for understanding the supercontinent cycle, because they overlap the development and dispersal of complex life forms in the shallow oceans along their margins. The hypotheses being tested in this project have implications for the dispersal and source of sediment in the shallow seas, the initiation and proliferation of early life in those seas, the evolving paleoclimatic system of the planet, and the time that the younger supercontinent cycle of Pangea initiated.