Age and Sources of Dzhagdy Terrane Metasedimentary Rocks in the Mongol–Okhotsk Fold Belt: Detrital Zircon U–Pb and Lu–Hf Isotopic Data

Abstract

Ditrital zircon U-Pb and Lu-Hf isotopic data are reported for metaterrigenous deposits of Dzhagdy Terrane in the Mongol–Okhotsk Fold Belt. The youngest zircon populations in metasedimentary rocks of the Dzheskogon and Nekter formations is concluded to be of the Middle–Late Triassic and Early Jurassic Age, suggesting that the formations are Early Mesozoic and not Carboniferous, as was previously assumed. We have made the assumption that the Dzheskogon, Nekter, and Bochagor formations of the Dzhagdy Terrane are not a single sedimentary sequence, but a set of tectonic slices consisting of Late Paleozoic and Early Mesozoic rocks of differing genesis. This raises the question on whether the terrane under consideration is a fragment of an accretionary prism. Detrital zircon U-Pb geochronological and Lu-Hf isotopic data coupled with whole-rock Sm-Nd isotopic data from previous studies indicate that the sedimentary basin was mainly sourced from the continental Amur Superterrane (from the south in present-day coordinates). Material replenishment from the southern framing of the North Asian Craton (from the north in present-day coordinates) was either minimal or absent.