美国莱斯大学Keller, Duncan S.课题组研究大火成岩省火山活动和俯冲铁质地层之间的联系取得新进展。该研究于2023年5月25日发表于国际一流学术期刊《自然—地球科学》杂志上。

课题组人员使用时间序列的统计分析表明，从3200到1000Myr以前，大多数铁质地层沉积年龄与241±5Myr以后的大火成岩省活动相关，并且这些事件在长时间尺度上是耦合的。结合来自构造学、地球动力学、矿物物理学和地震学研究的观察，课题组人员假设，密集俯冲铁质地层沉积可以在最低地幔中形成高传导性的富铁带，并促进热异常的形成，从而产生地幔柱上涌，并最终形成大火成岩省。尽管关于太古代和元古代的汇聚构造的确切性质仍然存在不确定性，但俯冲铁质地层对大火成岩省活动的促进，将把地球海洋化学与热流、地壳生产和化学分异的速度联系起来。

据了解，大火成岩省火山活动代表了广泛的地幔熔融，这种熔融引起地球化学分异、岩石圈和气候的变化。地幔成分的不均匀性，如积累的再循环地壳，可能对大火成岩省的活动起关键作用。一类是能产生独特的地幔不均匀性的铁质地层，这是地球早期海洋中形成的独特致密富铁沉积岩。尽管在大陆上保存了大量的铁质地层，其中一些成为主要的铁矿床，但大量的铁质地层也可能被再循环到地幔中，其后果不确定。

附：英文原文

Title: Links between large igneous province volcanism and subducted iron formations

Author: Keller, Duncan S., Tassara, Santiago, Robbins, Leslie J., Lee, Cin-Ty A., Ague, Jay J., Dasgupta, Rajdeep

Issue&Volume: 2023-05-25

Abstract: Large igneous province volcanism represents extensive mantle melting that has contributed to Earth’s chemical differentiation and lithospheric and climatic changes. Compositional heterogeneities in the mantle, such as accumulated recycled crust, may make key contributions to large igneous province activity. One class of rocks capable of producing distinctive mantle heterogeneities is the iron formations, uniquely dense Fe-rich sedimentary rocks formed in Earth’s early oceans. Although numerous iron formations were preserved on continents, with some becoming major Fe ore deposits, large amounts of iron formations may also have been recycled into the mantle, with uncertain consequences. Here we use statistical analysis of time series to show that from 3,200 to 1,000Myr ago, most iron formation deposition ages are correlated with large igneous province activity 241±15 Myr later, and that these events are coupled on long timescales. Linking observations from tectonics, geodynamics, mineral physics and seismology studies, we hypothesize that dense accumulations of subducted iron formations can form highly conductive Fe-rich zones in the lowermost mantle and facilitate the formation of thermal anomalies that produce mantle plume upwellings, and, ultimately, large igneous provinces. Although uncertainties remain regarding the precise nature of Archaean and Proterozoic convergent tectonics, facilitation of large igneous province activity by subducted iron formations would link Earth’s ocean chemistry to the pace of heat flow, crustal production and chemical differentiation.

DOI: 10.1038/s41561-023-01188-1

Source: https://www.nature.com/articles/s41561-023-01188-1