Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, Israel.
Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta, Canada.
Science. 2019 Aug 2;365(6452):469-473. doi: 10.1126/science.aaw9247.
The oxygen isotope composition (δO) of marine sedimentary rocks has increased by 10 to 15 per mil since Archean time. Interpretation of this trend is hindered by the dual control of temperature and fluid δO on the rocks' isotopic composition. A new δO record in marine iron oxides covering the past ~2000 million years shows a similar secular rise. Iron oxide precipitation experiments reveal a weakly temperature-dependent iron oxide-water oxygen isotope fractionation, suggesting that increasing seawater δO over time was the primary cause of the long-term rise in δO values of marine precipitates. The O enrichment may have been driven by an increase in terrestrial sediment cover, a change in the proportion of high- and low-temperature crustal alteration, or a combination of these and other factors.
自太古代以来，海洋沉积岩的氧同位素组成（δO）增加了 10 到 15 个千分位。由于温度和流体 δO 对岩石同位素组成的双重控制，这一趋势的解释受到了阻碍。过去 2 亿年左右的海洋氧化铁中的一个新的 δO 记录显示出类似的长期上升趋势。氧化铁沉淀实验揭示了一种弱温度依赖的氧化铁-水氧同位素分馏作用，这表明随着时间的推移，海水 δO 的增加是海洋沉淀物 δO 值长期上升的主要原因。O 的富集可能是由陆地沉积物覆盖的增加、高低温地壳蚀变比例的变化，或这些因素和其他因素的综合作用驱动的。
