The early Paleozoic tectonic evolution of the Russian Altai: Implications from geochemical and detrital zircon U-Pb and Hf isotopic studies of meta-sedimentary complexes in the Charysh-Terekta-Ulagan-Sayan suture zone

摘要

The Charysh-Terekta-Ulagan-Sayan suture zone was regarded as a tectonic boundary separating two distinct subduction-accretion systems in the Central Asian Orogenic Belt (CAOB). In the north, magmatic arcs, such as the Gorny Altai terrane, formed in the southwestern periphery of the Siberian continent, whereas in the south, arc-prism systems, such as the Altai-Mongolian terrane, formed around the so-called Kazakhstan-Baikal composite continent with Gondwana affinity. When did these two systems amalgamate and whether the metamorphic complexes in the suture zone represent Precambrian micro-continental slivers are critical for our understanding of the accretionary orogenesis and crustal growth rate in the CADS. A combined geochemical and detrital zircon U-Pb-Hf isotopic study was conducted on the meta-sedimentary rocks from the Ulagan (also referred to Bashkaus) and Teletsk Complexes in the suture zone. The results indicate that the protoliths of these rocks were dominated by immature sediments deposited in a time period between 500 and 420 Ma. Thus, Precambrian micro-continental slivers may not exist in the suture zone and even in the whole Altai Orogen.