Phosphate oxygen isotopes constrain Mesoproterozoic marine temperatures and the paucity of phosphorite

Yuntao Ye, Xiaomei Wang, Huajian Wang, Haifeng Fan, Zhigang Chen, Qingjun Guo, Ziteng Wang, Chaodong Wu, Donald E. Canfield, Shuichang Zhang*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Phosphorus (P) is an essential element for life, and the oceanic P cycle is closely coupled with the global carbon and oxygen cycles via the role of P as a limiting nutrient. Since P has only one stable isotope, tracking the P cycle through geological history is challenging. However, phosphate oxygen isotopes (δ18Op) represent a valuable tool for deciphering various P-related reactions, such as intracellular P turnover and enzymatic P regeneration, and have been successfully applied to modern soils and marine sediments. The marine P cycle prior to the Neoproterozoic Era remains controversial due to the scarcity of phosphorite and large uncertainties in estimating seawater phosphate levels. Here, we present δ18Op of carbonate fluorapatite (CFA) from the Mesoproterozoic Gaoyuzhuang and Xiamaling Formations in North China. Despite considerable uncertainties, the derived authigenic δ18Op values are markedly lower than those from modern sites with similar depth and latitude, which imply a warmer climate during the Mesoproterozoic Era compared to the present day. Based on thermodynamic calculations of saturation state with respect to CFA, we suggest that the elevated temperatures could have hindered P authigenesis, partially accounting for the general absence of phosphorite in contemporaneous successions.

Original languageEnglish
Article number121831
JournalChemical Geology
Volume644
Number of pages9
ISSN0009-2541
DOIs
Publication statusPublished - 20. Jan 2024

Keywords

  • Apatite
  • Gaoyuzhuang formation
  • North China
  • Phosphate oxygen isotopes
  • Xiamaling formation

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