Volcanism Pacing Slumping Gravity Flow Deposits during the Late Carboniferous in the Southern Margin of the Junggar Basin, China

Abstract

Deep‐water gravity depositional processes and evolution in arc systems have become hot research topics in recent years. This study discusses the co‐evolution of volcanism and deep‐water gravity flow deposits at the southern margin of the Junggar Basin based on petrology, geochronology, and geochemistry analyses. The results showed that a massive collapse of unstable sediments from the slope was triggered by volcanism, resulting in the formation of slumping gravity flows. The occurrence of volcanic beds in the slump deposits confirmed that synchronous volcanism likely affected sediment instability and triggered gravity flows. The Th/Yb, Ta/Yb, and Th/Ta elemental ratios, U‐Pb ages of detrital zircons, and palaeocurrent directions indicated that the North Tianshan (NTS) island arc represented the provenance of the Qianxia Formation. Moreover, statistical data on the pyroclastic components in the gravity flow deposits revealed an intensity index of volcanism, which indicated that volcanism is strongly related to gravity flow deposits, especially in terms of the type and distribution of deposits. A model for volcanically triggered deep‐water gravity flow deposits was established to provide a more in‐depth understanding of the co‐evolution of volcanism and gravity flow deposits and depositional setting of the Late Palaeozoic NTS oceanic subduction margin in the Junggar Basin.