Composition and Sources of Clastic Material of Terrigenous Rocks of the Khabarovsk Accretionary Complex (Sikhote-Alin)

Abstract

––The results of comprehensive studies of terrigenous rocks of the Khabarovsk Sikhote-Alin accretionary complex are presented. It is established that the fragments of Jurassic and Permian–Triassic sandstones are dominated by poorly rounded and poorly separated material mainly from local provenance areas. The detrital part of the rocks is mainly represented by quartz, in a smaller amount by feldspar and rock fragments. Sandstones are characterized by high silica content, moderate alumina content, low concentrations of femic elements and calcium, moderate alkali content with significant variations in the K/Na ratio. Both Jurassic and Permian–Triassic rocks are typically characterized by reduced contents of LILE, REE, to a lesser extent HFSE and negative values of the ɛNd(T) parameter – compared to PAAS. The model Nd age of Jurassic sandstones varies from 1.36 to 1.71 Ga, Permian–Triassic – from 1.14 to 1.35 Ga. Most of the detrital zircon population is of late Paleozoic–early Mesozoic age, approximately 25% are older (pre-Paleoproterozoic). The studied sandstones are mainly rocks of the first cycle of weathering (petrogenic), formed during the erosion of igneous rocks of felsic composition. The synthesis of the obtained data suggests that the main source of the cluster material for the Mesozoic sedimentary rocks was the geological formations of the northern part of the Bureya–Khanka superterrane (Bureya and Malokhingan blocks), as well as, possibly, the eastern part of the Mongol–Okhotsk belt. The Khabarovsk terrane has not drifted significantly along the Tan Lu stike-slip system and is an “autochthonous” block in the present-day structure of Sikhote-Alin.