Detrital muscovite 40Ar/39Ar geochronology and provenance of Cenozoic deposits in the Qaidam basin, northern Tibetan Plateau and comparison with detrital zircon and apatite records

Abstract

The single-grain detrital multi-mineral dating techniques are powerful tools for tracing sediment provenance. However, natural biases in sediment source-to-sink systems may lead to heterogeneous sink signals based on detrital single-grain ages. Differing provenance interpretations may arise from detrital multi-mineral geochronologic data because of the potentially diverse origins and transport behaviors of the analyzed detrital minerals. To test this hypothesis, we present new single-grain detrital muscovite 40Ar/39Ar dating results from the Cenozoic Qaidam basin and compile published detrital muscovite 40Ar/39Ar, detrital zircon U-Pb, and detrital apatite fission track age data to interpret muscovite provenance and to explore the potential inconsistencies among multi-dating results and related controlling mechanisms. Our results indicate that detrital muscovite grains from most Cenozoic deposits have a similar, dominated 300–400 Ma age range, with subordinate 200–300 Ma and 400–500 Ma. The new and compiled 40Ar/39Ar age data demonstrate that detrital muscovite records from the Cenozoic Qaidam basin are stratigraphically variable. Samples from middle fine-grained deposits-dominated strata, representing the paleo-megalake period, exhibit a relatively wider age range compared to those from lower and upper coarse-grained deposits-dominated strata, indicating a probable control of sedimentary environments. Comparisons of detrital muscovite, zircon, and apatite records indicate that the detrital zircon age spectra have the oldest ages, the widest age ranges, and the largest number of age groups. Detrital zircon and apatite age spectra exhibit higher spatial variations than detrital muscovite records, likely due to the distinct source-to-sink behaviors of these minerals. The magmatic, metamorphic, and uplift history of source terranes, along with system closure temperatures, originally determine detrital mineral age records, i.e., high-temperature systems yield older ages, and vice versa. Parent-rock types, mineral fertility, and weathering resistance control the numbers and probabilities of the detrital age clusters. Differences in mineral shape, density, and transport and depositional processes (i.e., different transport loads of light, platy minerals vs. heavy, granular minerals) may cause variations in age spectra. These differences in detrital mineral behaviors warrant more attention in multi-mineral dating-based sediment provenance studies. Additionally, 40Ar/39Ar age data compilation based on global Cenozoic sedimentary basins and modern rivers indicates that detrital muscovite records have potentials to determine tectonic settings, but climate-induced exhumation signals need to be distinguished before interpretation.