瑞士日内瓦大学Farsang Stefan团队研究了岛弧岩浆流体中硫的种类和金的迁移过程。这一研究成果于2024年12月16日发表在国际顶尖学术期刊《自然—地球科学》上。
据介绍，岩浆流体中存在的硫种类影响着全球氧化还原循环、地球气候，和一些最大、最具经济价值的关键金属矿床的形成。然而，在与上地壳岩浆储层相关的条件下，硫的种类形成尚不清楚。
研究人员将原型压力容器装置和拉曼光谱结合起来，在一系列地质相关的压力-温度-氧化还原条件下，原位确定了弧岩浆流体类似物中的硫种类。研究人员发现HS-、H2S和SO2是实验流体中的硫化物的种类，而与以前的实验工作相比，S6+和S2-和S3-硫自由基离子的浓度可以忽略不计。
当硫主要以HS-、H2S形式存在时，实验流体中测得的金的溶解度最高，大大超出热力学预测。研究结果表明，HS-（而不是硫自由基）是岩浆热液中金的高溶解度的原因。研究人员还发现，岩浆硫脱气是氧化条件下的氧化还原过程，并可能导致超出板块衍生通量和结晶作用之外的额外岩浆氧化。
附：英文原文
Title: Sulfur species and gold transport in arc magmatic fluids
Author: Farsang, Stefan, Zajacz, Zoltn
Issue&Volume: 2024-12-16
Abstract: The sulfur species present in magmatic fluids affect the global redox cycle, the Earth’s climate and the formation of some of the largest and most economic ore deposits of critical metals. However, the speciation of sulfur under conditions that are relevant for upper crustal magma reservoirs is unclear. Here we combine a prototype pressure vessel apparatus and Raman spectroscopy to determine sulfur speciation in arc magmatic fluid analogues in situ over a range of geologically relevant pressure–temperature–redox conditions. We find that HS-, H2S and SO2 are the main sulfur species in the experimental fluids, while the concentrations of S6+ species and S2- and S3- sulfur radical ions are negligible, in contrast to previous experimental work. The measured gold solubilities in the experimental fluids are highest when sulfur is dominantly present as HS- and H2S species and greatly exceed thermodynamic predictions. Our results imply that HS-, rather than sulfur radicals, accounts for the high solubilities of gold in magmatic–hydrothermal fluids. We also find that magmatic sulfur degassing is a redox process under oxidizing conditions and may lead to additional magma oxidation beyond that imparted by slab-derived fluxes and crystallization.
DOI: 10.1038/s41561-024-01601-3
Source: https://www.nature.com/articles/s41561-024-01601-3