Geodynamic emplacement setting of late jurassic dikes of the yanakolyma gold belt, ne folded framing of the siberian craton: Geochemical, petrologic, and upb zircon data
We present the results of geostructural, mineralogicpetrographic, geochemical, and UPb geochronological investigations of mafic, intermediate, and felsic igneous rocks from dikes in the YanaKolyma gold belt of the VerkhoyanskKolyma folded area (northeastern Asia). The dikes of the Vyun deposit and the Shumniy occurrence intruding Mesozoic terrigenous rocks of the KularNera and PolousniyDebin 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 KolymaOmolon 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 UPb SHRIMP-II dates obtained for the dikes corresponded to the Late Jurassic interval of 151145 Ma. We present a geodynamic model for the northeastern margin of the Siberian Craton for the Tithonian age of the Late Jurassic.
