Source of the sand-rich gas hydrate reservoir in the northern South China Sea: Insights from detrital zircon U–Pb geochronology and seismic geomorphology

Sand-rich gas hydrate reservoirs were initially drilled in the Qiongdongnan Basin of the northern South China Sea in 2019. In this study, the source of the sands in the gas hydrate reservoirs in the Quaternary and their transport routes in the northwestern South China Sea were unraveled by detrital zircon U–Pb geochronology and seismic geomorphology to predict the distribution of the sand-rich gas hydrate reservoirs. In the Quaternary, gas hydrate reservoirs in the study area were mainly deposited as submarine fans which could be sourced from the southwest based on core-log-seismic data. The detrital zircon U–Pb ages indicate that the Quaternary sediments in the Qiongdongnan Basin could be sourced from the Red River, Truong Son Belt, and Hainan Island provenances with contributions of 40.9%, 39.0%, and 20.0%, respectively. Sediments from Hainan Island, mixed with the sediments from the Red River and Truong Son Belt by turbidity and oceanic currents, could be transported to the study area through the northwestern slope of the Qiongdongnan Basin which is the main sediment transport route of the sand bodies, and deposited as submarine fans for a favorable exploration area for gas hydrates.