| Summary: | 碩士 === 國立中正大學 === 應用地球物理研究所 === 104 === In this study we analysis the detrital zircon U-Pb ages from Late Triassic to Eocene strata of Sichuan basin and Songpan-Ganze folded belt in eastern Tibet to discuss possible sediment provenance.
The Songpan-Ganze folded belt, comprised of 5-15km thickness of late Triassic flysch deposit, was deformed by Mesozoic and Cenozoic events which formed 3-5km high plateau. It connects with Sichuan basin by Longmenshan orogenic belt. In the Sichuan basin it comprised of shallow marine deposit since Mesozoic and become foreland basin deposit after the Cenozoic.
We collected samples from Triassic to Eocene strata in SW Sichuan basin and Songpan-Ganze folded belt in different age strata and we also combined with previous studies to analysis the possible sediment provenance. In the Songpan-Ganze folded belt we obtained more comprehensive age spectrums in Devonian strata. Previous study show the age spectrum concentrates on 970 Ma and 440 Ma and we observed there exists many 2.4-2.6 Ga grains. The Triassic strata are similar with previous studies which ages concentrate on ca. 1.8Ga, 790Ma and some grains are 260-300Ma and 410-470Ma.
In Sichuan basin the preliminary data show there are quite different age spectrums from Triassic to Jurrassic. The Triassic to Jurassic strata show the age spectrums concentrate on 270Ma, 450Ma, 800Ma, and few 1800Ma. But in Jurassic strata most of grain ages concentrate on 1800Ma. In the Cretaceous strata we started to observed ca. 215 Ma peak and some on 770Ma which infer the sediments could come from Songpan-Ganze folded belt. In Eocene strata the age spectrums concentrate on 1800 Ma and 270 Ma which infers the sediments different source from Cretaceous to Eocene.
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