Th/U and U series systematics of saprolite: importance for the oceanic 234U excess

Suhr, N.; Widdowson, M.; McDermott, F.; Kamber, B. S.

Abstract

The presence of excess 234U in seawater is a compelling argument for active delivery of solutes from the continents to the oceans. Previous studies found, however, that the complementary 234U deficit on the continents is surprisingly modest, which would require protracted U loss from a large continental weathering pool. Our new compilation and statistical analysis of the published data, coupled with a mass balance calculation demonstrates that the apparent small 234U deficit in the continental weathering pool implied by previous studies is insufficient to balance the observed oceanic excess. Our new data for a saprolite weathering profile developed on Deccan basalt reveal a very strong overall loss of U (elevated Th/U) with a strong 234U deficit attributable to chemical weathering. The U and 234U deficits reported here from a geologically recent saprolite confirm the importance of the early stages of chemical weathering at the weathering front in the supply of nutrients to the oceans. Thus, as much as half the oceanic 234U inventory is likely sourced from a thin active saprolite zone.

Citation

Suhr, N., Widdowson, M., McDermott, F., & Kamber, B. S. (2018). Th/U and U series systematics of saprolite: importance for the oceanic 234U excess. Geochemical Perspectives Letters, 6, 17-22. https://doi.org/10.7185/geochemlet.1803

• Journal Article Type: Article
• Acceptance Date: Jan 26, 2018
• Online Publication Date: Feb 14, 2018
• Publication Date: 2018
• Deposit Date: May 28, 2022
• Publicly Available Date: May 30, 2022
• Journal: Geochemical Perspectives Letters
• Print ISSN: 2410-3403
• Peer Reviewed: Peer Reviewed
• Volume: 6
• Pages: 17-22
• DOI: https://doi.org/10.7185/geochemlet.1803
• Keywords: U-series systematics; Saprolite; Chemical weathering; Critical zone; Deccan Traps; Uranium mass balance; Seawater; Soil formation
• Public URL: https://hull-repository.worktribe.com/output/1378934