Detrital multi-mineral provenance constraints on the reconstruction of the South China Block within Gondwana

Abstract

The late Neoproterozoic-early Paleozoic marked an important interval in Earth history, during which there was the transition from the breakup of Rodinia to the assembly of the Gondwana supercontinent. The South China Block (SCB) is a key part of Gondwana, and is an important component in its paleogeographic reconstructions. Sedimentary provenance analysis has been applied to constrain the SCB source-to-sink systems and hence to reconstruct its position within Gondwana. However, previous studies have mainly undertaken detrital zircon provenance analysis on Cryogenian-Ordovician strata from a single sedimentary basin, leading to different paleogeographic models for the SCB within the Gondwana supercontinent. To resolve these challenges, detrital rutile, apatite and zircon data of Cryogenian to Ordovician successions from four sub-basins in the Cathaysia Block of South China were compiled in addition to acquiring new data from four samples. Detrital rutile and apatite from the Cryogenian to Ordovician successions share similar 650–500 Ma major age populations, which are considered mainly derived from Pan-African orogens in western Australia, India and East Antarctica. Most detrital rutiles are derived from amphibolite- or eclogite-facies metamorphic rocks, with appreciable proportions (22–42%) derived from metamafic rocks. The apatite data demonstrate a significant amount of metamorphic- (52–72% of all grains) and mafic-derived (40–70% of igneous-derived grains) populations. Three provenance switches are demonstrated by the detrital apatite data and indicate the exhumation of Pan-African orogens in the late Cryogenian, Ediacaran-Cambrian, and early Ordovician in the source areas. In contrast, the detrital zircon data are characterized mainly by 1300–900 Ma igneous populations from late Mesoproterozoic-early Neoproterozoic orogens in western Australia and India. Provenance switches caused by exhumation of the orogenic sources and the Cathaysia Block in the late Ediacaran and middle Cambrian are detected. The trace element systematics of rutile and apatite along with zircon Lu-Hf isotopic compositions reflect similar temporal trends in the proportions of materials derived from (meta)mafic rocks and juvenile crust. They support increased input of juvenile crust including (meta)mafic source rocks in the Ediacaran and subsequent exhumation. Collectively, the variations in age and lithology of source(s) are best detected by the detrital apatite dataset, especially for metamorphic- and mafic-derived sources when information from detrital rutile can also be integrated. Our analysis provides a more refined and complete understanding of the provenance evolution of the Cathaysia basins by this analysis of detrital multi-mineral datasets, and places further constraints on reconstructions of the South China Block within Gondwana.