英国曼彻斯特大学Zoltán Taracsák团队研究了加那利岛岩浆中硫的起源及其对地球深部硫循环的影响。相关论文于2025年3月19日发表在《美国科学院院刊》杂志上。
全球硫循环在地球表面和上地幔的氧化还原演化中起着至关重要的作用，但地幔中硫的分布和来源在很大程度上仍然不受限制。耶罗岛是加那利群岛的一个火山岛，由富含硫的岩浆供给。为了限制这些熔体中硫的来源，研究组将原位硫同位素分析与回归建模相结合。他们计算出未脱气的El Hierro熔体的δ34S值为0±2‰。未脱气的耶罗熔体的平均δ34S比大洋中脊喷发的岩浆高0.3‰至1‰。质量平衡计算表明，耶罗地幔源含有310±120μg/g硫，源中平均60%的硫来自循环来源。这种回收材料应含有>1800μg/g硫，以满足地幔源中其质量分数的同位素限制。
蛇纹岩和沉积物中的硫和氧同位素特征明显偏离上地幔，使其不适合作为回收材料的候选者。经过俯冲带处理后，回收的海洋地壳的氧化部分熔融保留了其三分之一的硫预算，这可以解释加那利岛地幔中的过量硫。回收的海洋地壳预计含有硫化物形式的硫，硫不能氧化地幔。回收组分中铁的存在是产生交代熔体所必需的，交代熔体具有足够的氧化性，可以将足够的硫带入海岛玄武岩的地幔源。
附：英文原文
Title: The origin of sulfur in Canary Island magmas and its implications for Earth’s deep sulfur cycle
Author: Taracsák, Zoltán, Hartley, Margaret E., Burgess, Ray, Edmonds, Marie, Longpré, Marc-Antoine, Monteleone, Brian D., Tartèse, Romain, Turchyn, Alexandra V.
Issue&Volume: 2025-3-19
Abstract: The global sulfur cycle plays a critical role in the redox evolution of Earth’s surface and upper mantle, yet the distribution and origin of sulfur in the mantle remains largely unconstrained. El Hierro is a volcanic island in the Canary archipelago that is fed by sulfur-rich magmas. To constrain the origin of sulfur in these melts, we combine in situ sulfur isotope analyses with regression modeling. We calculate that undegassed El Hierro melts have δ34S values of 0 ± 2‰. The average δ34S of undegassed El Hierro melts is 0.3‰ to 1‰ higher than magmas erupting at mid-ocean ridges. Mass balance calculations reveal that El Hierro’s mantle source contains 310 ± 120 μg/g sulfur and that on average 60% of sulfur in the source is of recycled origin. This recycled material should contain >1,800 μg/g sulfur to satisfy isotopic constraints on its mass fraction in the mantle source. The sulfur and oxygen isotopic signature in serpentinites and sediments deviate significantly from the upper mantle, making them unsuitable candidates for the recycled material. An oxidized partial melt of recycled oceanic crust that retained one third of its sulfur budget after subduction zone processing can explain excess sulfur in the Canary Island mantle. Recycled oceanic crust is expected to contain sulfur as sulfide, which is not capable of oxidizing the mantle. The presence of ferric iron in the recycled component is necessary to produce metasomatic melts that are oxidizing enough to carry sufficient sulfur into the mantle source of ocean island basalts.
DOI: 10.1073/pnas.2416070122
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2416070122