Single quartz δ18O: A new frontier in detrital provenance analysis (Bengal Fan, IODP Expedition 354)

Abstract

Quartz is the most abundant mineral in sediments and sedimentary rocks but efforts to reliably identify its provenance have been only partially fruitful so far. Even advanced methods such as cathodo-luminescence, Raman spectroscopy, synchrotron X-ray absorption spectroscopy, and laser ablation spectrometry have led to limited success. This article demonstrates how the δ18O of detrital quartz provides useful additional insight. The oxygen-isotope signature primarily depends on source rocks and their formation conditions, being highly different for different crustal sources and highest for carbonate rocks.This study illustrates a new protocol to analyze δ18O signatures of single quartz grains and shows how provenance from magmatic, metamorphic, or sedimentary domains can be discriminated. In each sand sample from rivers draining exclusively a single Himalayan tectonic domain (e.g., Trans-Himalaya, Greater Himalaya, Lesser Himalaya, and Tethys Himalaya), ~200 quartz grains were analyzed by ion microprobe LG-SIMS (Large Geometry Secondary Ion Mass Spectrometry) to characterize their oxygen-isotope variability. In each turbidite sample collected from the Bengal Fan during IODP Expedition 354, ~150 quartz grains were analyzed next to quantify the relative contribution of each Himalayan domain. This allowed us to complement data obtained with other bulk-sediment to single-mineral approaches, thus enhancing provenance resolution and highlight the erosional evolution of the Himalayan-Tibetan orogen through time.