Geodynamic Emplacement Setting of Late Jurassic Dikes of the Yana–Kolyma Gold Belt, NE Folded Framing of the Siberian Craton: Geochemical, Petrologic, and U–Pb Zircon Data

We present the results of geostructural, mineralogic–petrographic, geochemical, and U–Pb geochronological investigations of mafic, intermediate, and felsic igneous rocks from dikes in the Yana–Kolyma gold belt of the Verkhoyansk–Kolyma folded area (northeastern Asia). The dikes of the Vyun deposit and the Shumniy occurrence intruding Mesozoic terrigenous rocks of the Kular–Nera and Polousniy–Debin terranes were examined in detail. The dikes had diverse mineralogical and petrographic compositions including trachybasalts, andesites, trachyandesites, dacites, and granodiorites. The rocks showed significant similarities in distributions of REE, and their concentrations of most HFSEs were close to the intermediate ones between ocean islands basalts and enriched middle ocean ridge basalts. We propose that the subduction that was ongoing during the collision of the Kolyma–Omolon superterrane with Siberia led to melting in the asthenospheric wedge and in the lithosphere, which formed a mixed source for the dike systems from both an enriched and a depleted mantle source. The U–Pb SHRIMP-II dates obtained for the dikes corresponded to the Late Jurassic interval of 151–145 Ma. We present a geodynamic model for the northeastern margin of the Siberian Craton for the Tithonian age of the Late Jurassic

Late Neoproterozoic evolution of the southwestern margin of the Siberian Craton: evidence from sedimentology, geochronology and detrital zircon analysis

Sedimentary successions and igneous rocks exposed in Eastern Sayan provide an important geological record on the tectonic evolution of the southwestern margin of the Siberian Craton during the Neoproterozoic. Here we present sedimentological and detrital zircon provenance data from key stratigraphic units, complemented by a new U-Pb zircon age of 718 ± 6 Ma from the mafic Nersa magmatic complex. Sedimentological and provenance data from the lower part of the stratigraphic succession (Karagasy Group) show that these rocks were deposited in a passive margin setting after 750 Ma and before the emplacement of the Nersa magmatic complex. The upper part of the stratigraphic succession (Oselok Group) consists of Cryogenian and Ediacaran glaciogenic deposits and associated cap carbonates, overlain by mid to late Ediacaran sequences of dominantly shallow-marine and fluvial siliciclastic rocks. Provenance data indicate that rocks from the Tuva-Mongolia and Zavkhan terranes provided a significant input of detrital material into the sedimentary basin that was the source of the glacial deposits. Orogenic processes during the late Ediacaran (ca 570–540 Ma) in Eastern Sayan were likely associated with the accretion of the Tuva-Mongolia terrane, as indicated by the detrital zircon data