DETRITAL MODAL, GEOCHEMICAL CHARACTERISTICS AND TECTONIC SETTING OF THE DAJIN MARINE CLASTIC ROCKS, TIBET

Abstract

The Dajin marine clastic rocks outcropped in the Gangriboche Mountain area, western Tibetan, which was previously regarded as a part of nonmarine molasse together with Gangdese conglomerates formed by India-Eurasia collision. So far, detrital assemblage, source area, and tectonic setting of this unit have not been studied in detail. This paper presents detrital modal from statistic petrological data of conglomerates and greywacke as well as geochemical data of the greywacke and siltstones which are used to study and discuss their source area and tectonic setting based on their sedimentary sequences. These data indicate that source area of the Dajin marine deposits is characterized by combination of continental arc, oceanic island are and passive continental margin, and that the Dajin marine deposits may deposit in a forearc basin.