Abstract:

       Increasing data indicate that the SE coastal region of China mainland is not a post-Caledonian platform but a amalgamation of different massives. The Late Triassic Wenbinshan Formation in southwestern Fujian Province is characterized by quasi-mollasse. The U-Pb dating on detrital zircons is employed in this research to a better understanding of the varied provenances and the regional tectonic evolution. The morphological observations of detrital zircons and the U-Pb age dating results reveal four points regarding to the tectonic evolution in southwestern Fujian Province as follows: (1) Late Triassic Wenbinshan Formation has a complicated provenances but mainly derived from northwestern Fujian uplift. (2) Late Triassic sedimentation has an Archaean provenance older than 2.5 Ga which indicates distribution of Archean continent relics on Cathaysia region or another previously unrevealed Archean basement in southeast China. (3) 980-1,190 Ma detrital zircons imply that a Grenville age block served as a provenance area during Late Triassic sedimentation. This block collided with Cathaysia block as a result of the closing of Paleo-Tethys ocean during Late Triassic. (4) The Indosinian magmatic rocks belt in the region formed another part of the provenance during the Late Triassic sedimentation of Wenbinshan Formation.
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Key words: U-Pb dating, detrital zircon, Wenbinshan Formation, Late Triassic, southwestern Fujian