Temporal covariation of island arc Sr isotopes and seawater chemistry over the past 2 billion years

• 成果类型: Article
• 署名作者: Bednarick, Amanda L.; Bucholz, Claire E.; Depaolo, Donald J.; Stolper, Daniel A.
• 署名单位: California Institute of Technology; University of California System; University of California Berkeley; United States Department of Energy (DOE); Lawrence Berkeley National Laboratory
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-11566
• DOI: 10.1073/pnas.2401832121
• 发表日期: 2024-10-22
• 关键词: trace-element composition; hydrothermal alteration; sm-nd; troodos ophiolite; samail ophiolite; EVOLUTION; crust; geochemistry; systematics; subduction

摘要

The chemical compositions of island arc basalts (IAB) reflect contributions from the mantle as well as fluids and melts from the subducting slab. Addition of radiogenic seawater Sr to oceanic crust through hydrothermal alteration and subsequent subduction is often invoked to explain elevated 87 Sr/ 86 Sr signatures in modern IAB. However, changes in the 87 Sr/ 86 Sr of island arc magmatic rocks through time has not been investigated, limiting our understanding of the factors influencing the Sr budgets of arcs throughout Earth's history. To address this, we compiled 87 Sr/ 86 Sr values from island arc magmatic rocks ranging in age from modern to Paleoproterozoic, only including data from island arc localities that best preserve initial magmatic 87 Sr/ 86 Sr. Median initial 87 Sr/ 86 Sr values are consistently elevated compared to depleted mantle 87 Sr/ 86 Sr over this period, indicating persistent enrichment in radiogenic Sr in island arcs. Moreover, the elevation in island arc 87 Sr/ 86 Sr relative to the depleted mantle is variable. A notable rise in island arc