Sandstone provenance analysis in Longyan supports the existence of a Late Paleozoic continental arc in South China

Because of the limited magmatic and metamorphic record, the Late Paleozoic tectonic setting in South China remains controversial. This paper presents sedimentologic data and provenance analysis of Upper Paleozoic sandstones in Longyan, which are rich in quartz (73–90%) and poor in lithic fragments (2–12%) and feldspar (3–25%). Devonian sandstones contain mostly metamorphic lithic fragments (e.g., quartzite), whereas Carboniferous-Permian sandstones contain mostly felsic volcanic and subvolcanic lithic fragments indicating provenance from felsic volcanic rocks. Detrital zircon U-Pb age spectra of Devonian-Carboniferous sandstones display modes at ~440 Ma and 420–380 Ma, with subordinate Mesoproterozoic age components, pointing at the Nanling terrane and the western-middle part of the Wuyi terrane as most likely ultimate sediment sources. Permian sandstones inherited the age components mentioned above, but also include peaks at ~290 Ma and ~1850 Ma. The ~290 Ma component corresponds to the age of Late Paleozoic magmatism in southeastern China and southwest Japan. Numerous detrital zircons aged at 350–250 Ma also occur in Permo-Triassic strata exposed across South China and southwest Japan. Based on regional data and on the ages and Hf isotope signatures of detrital zircon, we infer that a Late Paleozoic continental arc existed in the coastal area of southeastern China and contributed detritus to the adjacent sedimentary basins. The Permo-Triassic igneous rocks locally exposed in the area may represent the remnant of that continental arc. Arc growth may have been responsible for the westward retreat of a broad Upper Paleozoic carbonate platform.