Age, provenance and tectonic setting of Neoproterozoic to early Paleozoic sequences in southeastern South China Block: Constraints on its linkage to western Australia-East Antarctica

Abstract

Zircon U-Pb-Hf isotopes and whole-rock geochemical data are applied to investigate the age, provenance and tectonic setting of the late Neoproterozoic and overlying sequences from the Cathaysia Block of South China, in order to understand the tectonothermal evolution of this block and its linkage to supercontinents. New zircon U-Pb ages, in combination with previous fossil data, indicate the lower and upper Louziba Groups were deposited between 655 and 635Ma (Cryogenian) and 635 and 542Ma (Ediacaran), respectively. Low CIA (65–57) and high ICV (1.64–1.05) values for the Louziba sandstones are suggestive of immature sediments that experienced mild to weak chemical weathering in their source areas. In contrast, early Paleozoic sandstones have higher CIA (80–69) and lower ICV (0.95–0.84) values, indicative of mature sediments with intensive chemical weathering. Despite the different degrees of chemical weathering, all sedimentary samples show positive correlation between TiO2 and Al2O3, and negative correlation in plot of (La/Yb)n vs Zr but lack any correlation between (La/Yb)n and P2O5. These data demonstrate sorting of resistant minerals, such as rutile, monazite and zircon, did not affect the chemical signatures of sampled detritus. Consequently, geochemical features, in combination with detrital age spectra, indicate that the Louziba Group and overlying sequences record sedimentation in collisional and passive settings, with the detritus being derived dominantly from intermediate to felsic igneous rocks.Late Mesoproterozoic (ca.1300–1000Ma) detritus in the lower Louziba Group were probably derived primarily from the Windmill Islands-Bunger Hills (1300–1050Ma) and Albany-Fraser Belt-Musgrave (1300–1050Ma) regions in East Antarctica-western Australia. Increasing input of early Neoproterozoic (∼990–950Ma) detritus in the uppermost Louziba Group indicates a greater contribution from the Eastern Ghats (ca. 990–950Ma) in eastern India and North Prince Charles Mountains (ca. 990–950Ma) in East Antarctica. This source change was synchronous with the formation of the Kuunga (560–530Ma) and Pinjarra (560–520Ma) Orogens during assembly of Gondwana. The sediments of the Huanglian Formation of the uppermost Louziba Group likely recorded this event. Overlying Paleozoic sequences then were deposited on passive margin with detritus being derived dominantly from an early Neoproterozoic source, e.g., eastern India and East Antarctica.