Detrital apatite Lu-Hf and U-Pb geochronology applied to the southwestern Siberian margin

Abstract

Apatite is increasingly used in sedimentary provenance studies. However, detrital apatite U–Pb geochronology can be challenging due to the presence of non-radiogenic Pb, its intermediate closure temperature (~350–550°C) and/or age-resetting by metamorphic/metasomatic processes. The Lu–Hf system in apatite has a higher closure temperature (~675–750°C) and is, therefore, more robust to thermal resetting. Here we present the first detrital apatite Lu–Hf age spectra. We have developed a laserablation Lu–Hf dating technique, using reaction-cell mass spectrometry, that allows rapid cost-effective analysis, required for detrital apatite studies. The method is best suited to Precambrian detritus, permitting greater radiogenic Hf ingrowth. Using samples from Siberia, we demonstrate: (1) excellent correlations between U–Pb and Lu– Hf dates for apatites from igneous protoliths; and (2) that Lu–Hf dating can detect primary age information in metamorphic grains. Hence, when used in tandem with U–Pb zircon and apatite geochronology, Lu–Hf apatite dating provides a powerful new tool for provenance studies.