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

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 (similar to 350-550 degrees C) and/or age-resetting by metamorphic/metasomatic processes. The Lu-Hf system in apatite has a higher closure temperature (similar to 675-750 degrees C) and is, therefore, more robust to thermal resetting. Here we present the first detrital apatite Lu-Hf age spectra. We have developed a laser-ablation 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.

Automated summary

Apatite is increasingly used in sedimentary provenance studies, but detrital apatite U-Pb geochronology can be challenging. By contrast, the Lu-Hf system in apatite has a higher closure temperature and is more robust, providing a powerful new tool for provenance studies.