The Stable Isotope and Minor Element Geochemistry of Iron (III) Oxide Rocks and Minerals

氧化铁 (III) 岩石和矿物的稳定同位素和微量元素地球化学

• 批准号: 8719070
• 负责人: Crayton Yapp
• 金额: $ 9.02万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-02-01 至 1990-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8719070&HistoricalAwards=false
• 关键词: Stable; Isotope; Minor; Element; Geochemistry

Recent work in this laboratory has shown that the common mineral goethite is an important new low temperature oxygen isotope geothermometer in combination with silica, carbonate or phosphate. A potentially important development in these studies has been the discovery of a CO2 component in natural goethites that might serve as a quantitative indicator of CO2 partial pressures. The proposed studies include experiments to calibrate the temperature dependence of the hematite-water oxygen isotope fractionation, substantiation of the goethite-water oxygen isotope curve, and further investigation of the CO2 component in goethite as a possible indicator of ancient P(CO2) values. Additional efforts will include infrared work to study both the amounts and chemical speciation of the CO2 in goethite. This knowledge will be applied to Phanerozoic oolitic hematitic and goethitic ironstones representing ore-grade concentrations of chemically precipitated, oxidized iron which formed during two extended "pulses" in the Phanerozoic. These pulses generally coincided with periods of high eustatic sea level, flooded continents, and rapid rates of sea-floor spreading. The study should yield information on surface or near-surface temperatures, water-rock interactions and possibly CO2 partial pressures in the local environment. More generally, such data could provide insight into plaeoclimate and possible secular variations in seawater 0-18/0-16 ratios at a time when there was continental glaciation in the southern hemisphere, thus increasing our knowledge of conditions during an interval of considerable interest in the Phanerozoic.

本实验室最近的工作表明，常见矿物针铁矿是与二氧化硅、碳酸盐或磷酸盐相结合的一种重要的新型低温氧同位素地质温度计。这些研究的一个潜在的重要进展是在天然针铁矿中发现了一种二氧化碳成分，它可以作为二氧化碳分压的定量指标。建议的研究包括实验标定赤铁矿-水氧同位素分馏的温度依赖性，充实针铁矿-水氧同位素曲线，以及进一步研究针铁矿中的CO2组分作为古代P(CO2)值的可能指示器。其他努力将包括研究针铁矿中二氧化碳的数量和化学形态的红外工作。这一知识将被应用于显生宙的蚝粒赤铁矿和针铁矿铁矿，这些铁矿代表在显生宙的两次延伸的“脉冲”期间形成的化学沉淀的氧化铁的矿石级集中度。这些脉冲通常与海平面高、大陆被洪水淹没和海底快速扩张的时期相吻合。这项研究应该提供关于地表或近地表温度、水-岩石相互作用以及当地环境中可能的二氧化碳分压的信息。更广泛地说，这些数据可以提供对南半球大陆冰川时期海水0-18/0-16比率的古气候和可能的长期变化的洞察，从而增加我们对显生界相当感兴趣的间歇期条件的了解。