近日，南非开普敦大学Tostevin, Rosalie团队报道了前寒武纪海洋中，受绿橄榄岩建造控制的微量营养素的可用性。该项研究成果发表在2023年11月13日出版的《自然—地球科学》上。
研究人员量化了 Fe(II)硅酸盐矿物（结晶绿橄榄岩的前体）在海水和热液流体中形成和后续成岩过程中的金属分配。研究数据显示， Fe(II)硅酸盐可能在太古代热液柱中迅速沉淀，严重削弱了热液中，特别是铜、锌和钒等关键营养物质的输送。研究结果为太古代海洋中的金属可用性模式提供了机械解释，与蛋白质结构和基因组学比较预测的金属利用的时间模式一致。此外，研究结果还表明，天然绿橄榄岩可能提供了深时金属可用性的案例。
研究人员表示，在太古代(40-25 亿年前)进化而来的新陈代谢，优先选择铁、锰和钼来形成金属蛋白，而大多数结合锌、铜和钒的蛋白质出现得更晚。对这些元素的初始偏好通常被解释为，这一现象反映了它们在缺氧海水中的可用性，而游离硫化物被认为是一个关键影响因素。虽然硫化物水降低了锌和铜的可用性，同时也除去了钼，留下了钒。此外，目前的地球化学数据主要反映了含铁（富 Fe2+）的条件，而不是硫化物的条件。与此相一致的是，最近的沉积学工作在太古代岩石中发现了丰富的铁硅酸盐矿物。
附：英文原文
Title: Micronutrient availability in Precambrian oceans controlled by greenalite formation
Author: Tostevin, Rosalie, Ahmed, Imad A. M.
Issue&Volume: 2023-11-13
Abstract: Metabolisms that evolved in the Archaean era (4.0–2.5 billion years ago) preferentially selected iron, manganese and molybdenum to form metalloproteins, whereas the majority of zinc-, copper- and vanadium-binding proteins emerged much later. The initial preference for these elements is commonly interpreted to reflect their availability in anoxic seawater, with free sulfide proposed as a key influence. While sulfidic waters reduce the availability of zinc and copper, they also remove molybdenum and leave behind vanadium. Furthermore, current geochemical data reflect predominantly ferruginous (Fe2+-rich), rather than sulfidic, conditions. Consistent with this, recent sedimentological work has uncovered abundant iron silicate minerals in Archaean rocks. Here we quantify metal partitioning during the formation and subsequent diagenesis of an Fe(II) silicate mineral, a precursor to crystalline greenalite, in both seawater and hot hydrothermal fluids. Our data show that Fe(II) silicates could have precipitated rapidly in Archaean hydrothermal plumes, severely attenuating hydrothermal delivery of key nutrients, in particular copper, zinc and vanadium. These results provide a mechanistic explanation for metal availability patterns in Archaean oceans that is consistent with temporal patterns of metal utilization predicted from protein structures and comparative genomics. Further, our data suggest natural greenalite may provide an archive of metal availability in deep time.
DOI: 10.1038/s41561-023-01294-0
Source: https://www.nature.com/articles/s41561-023-01294-0