Kinetics of the Formation and Transformation of Iron Oxides in Hydrothermal Systems

水热系统中氧化铁的形成和转化动力学

• 批准号: 0229556
• 负责人: Hiroshi Ohmoto
• 金额: $ 30.67万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0229556&HistoricalAwards=false
• 关键词: Kinetics; Formation; Transformation; Iron; Oxides

Most of the world's Fe supply comes from: (a) Precambrian banded iron formations (BIFs), which were composed of a variety of iron-bearing minerals (hematite, magnetite, siderite, and pyrite) that accumulated in submarine hydrothermal environments; and (b) hematite-rich secondary iron ores that were transformed from the magnetite, hematite, siderite, and pyrite of BIFs. The goals of the proposed research are three-fold: (i) to understand the systematics of the geochemical environments and processes involved in the formation and transformation of iron oxides (and other major Fe-bearing minerals) in submarine hydrothermal systems (e.g., BIFs and VMS -volcanogenic massive sulfide deposits); (ii) to develop mineralogical and geochemical methods to identify the depositional environments of Fe-bearing minerals; and (iii) to develop a new exploration model for iron ore deposits. These goals will be achieved through two series of laboratory investigations, exploring: (I) the kinetics of the formation of iron-bearing minerals and silica during the mixing of Fe2+- and silica-bearing hydrothermal fluids with seawater of various compositions, and (II) the kinetics of the non-redox transformation of hematite magnetite at temperatures below 250 C. Some of the important hypotheses will be tested in this research, including: (1) the concentrations of dissolved O2 and HCO3- in the local seawater played major roles in determining the iron mineralogy of BIFs and other hydrothermal ore deposits formed on the ocean floor; (2) hematite-rich BIFs are good evidence for the oxygenated oceans and atmosphere during the Archean era; (3) siderite-rich BIFs suggest they formed in anoxic basins; (4) the transformation of hematite to magnetite, or magnetite to hematite, which in many types of ore deposits was not caused by redox reactions, but caused by simple additions of Fe2+ to hematite, or leaching of Fe2+ from magnetite: Fe2O3 (hm) + Fe2+ + H2O = Fe3O4 (mt) + 2H+; (4) hematite-rich iron ores formed in deep crust as well as on the land surface.

世界上大多数FE供应都来自：（a）由多种含铁的矿物（赤铁矿，磁铁矿，铁矿和黄铁矿）组成的前寒武纪铁层（BIF），这些矿物质是在海底水热环境中积累的； （b）从磁铁矿，赤铁矿，岩石和黄铁矿转化的富含赤铁矿的二级铁矿石。拟议的研究的目标是三倍：（i）了解参与海底热液系统中氧化铁（以及其他主要的含铁矿物）的地球化学环境和过程的系统学（例如，BIFS和VMS- VMS- VMS- VMS-VOL-VOLCANIC-VOLCANIC-VOR-VOLCANIC大量硫化物沉积物）； （ii）开发矿物学和地球化学方法来识别含含粪矿物的沉积环境； （iii）开发一种用于铁矿石沉积的新勘探模型。这些目标将通过两种一系列的实验室调查来实现：（i）在Fe2+和含硅二氧化硅的水热液与各种成分的海水混合过程中形成的矿物质和二氧化硅的动力学，以及（ii）在下面的非二氧化碳的非氧化含量下，有效的250.研究，包括：（1）当地海水中溶解的O2和HCO3的浓度在确定BIFS的铁矿物学和海底形成的其他热液矿石沉积物方面发挥了重要作用； （2）富含赤铁矿的BIF是大帝时代含氧的海洋和气氛的良好证据； （3）富含铁矿的BIF建议它们在缺氧盆地中形成； （4）赤铁矿向磁铁矿或磁铁矿转化为赤铁矿，在许多类型的矿石沉积中，这不是由氧化还原反应引起的，而是由Fe2+简单添加到hematite引起的，或从磁铁矿中浸出Fe2+从磁铁矿中浸出：Fe2O3（hm）+ Fe2++ h2++ h2O = h2O = fe3O4（h2O = fe3O4（MT）+ 2h+ 2h+ 2h+++ 2h++; （4）富含赤铁矿的铁矿石，在深层地壳和陆地表面形成。