Abstract:

The Triassic clastic sedimentary rocks in the GongheHuashixia Area, Qinghai Province are classified as greywacke and arkose based on petrochemistryProvenance rocks formed in arc setting during the Paleozoic and were exhumed to surface by subsequent collision, which are mafic or its partial melting product, metamorphosed basement and/or its anatexis magma, as well as granitesAveraged Nd depleted mantle model age is 175 Ga, which is consistent with those of basements of the Qilian Mountains, the Qaidam, the Eastern Kunlun Orogens and the Yangtze CratonThe Nd depleted model age suggests that the blocks share common tectonic affinity to the GondwanaThe histogram and probability density distribution of zircon UPb ages show significant peaks of 400500 Ma, 250300 Ma plus a secondary peak of 7501 000 Ma, which indicate key tectonomagmatism episodes of the Paleozoic, the Early Mesozoic, and the Neoproterozoic in the Qaidam, the Eastern Kunlun, and the Qilian MountainsThe ages of greater than 1 000 to 2 700 Ma represent basement formation of the Qilian, the Qaidam and the Eastern Kunlun OrogensHf isotopic compositions of zircons show three dominant age ranges of 1725 Ga, 2836 Ga and 1017 Ga for accretion of provenance crustThe majority of zircons are mixing products of anatexis melts derived from NeoproterozoicPaleozoic mafic rocks and basement rocks of the Qilian Mountains, the Qaidam, and the Eastern Kunlun MountainsThe Late PaleozoicEarly Mesozoic zircons originated mainly from anatexis melts of Paleozoic juvenile crustContrasting histogram to that of Triassic clastic sedimentary rocks in the western Qinling Mountain suggests that their provenance material were not communicated owing to the barrier of the western Qinling MountainIn contrast to high reliefs of the Qaidam, the Qilian Mountains, and the Eastern Kunlun, the western Qinling Mountain was in low relief with little contribution to the Gonghe Basin during the Triassic period.

Key words: Gonghe Basin; Triassic; clastic sedimentary rocks; provenance; tectonic affinity