The Stable Isotope and Minor Element Geochemistry of Iron- Rich Chemical Sediments

以三价铁氧化物为主的化学沉积物是地球表面和许多近地表环境中丰富的游离氧和液态水独特组合的表现。 该实验室进行的研究表明，某些铁（III）氧化物中氧、氢和碳的稳定同位素比率包含有关古代温度、水源以及与铁（III）氧化物沉淀相关的水性碳酸盐系统的有机成分的信息。 此外，来自地岩的捕获的二氧化碳丰度数据可能与矿物形成时的环境二氧化碳分压有关。 将研究普遍存在的磷酸铁（III）氧化物对的氧同位素系统学，以确定它们是否包含古温度信息。 从这项研究以及我们之前对氧化铁（III）的研究中获得的知识将应用于显生宙鲕粒铁岩、最近细菌介导的氧化铁（III）沉淀物和晚前寒武纪带状铁形成（BIF）的同位素、化学和随之而来的岩相学研究。 晚奥陶世风化面的碳酸铁 (III) 丰度和碳 13 变化可以提供有关周围二氧化碳分压和有机质在这一古老环境中的作用的知识。 将获得来自显生宙全球“温室”和“冰室”区间的热带鲕粒铁矿石的氧、氢和碳丰度以及同位素数据。 将比较古代热带温度和水源，以寻找代表这些假定的全球极端气候的沉积物。 晚前寒武纪石英-赤铁矿 BIF 的氧同位素测量应该可以深入了解该矿床的沉积环境。 本研究中获得的古气候数据对于最终了解全球构造与可能在晚前寒武纪产生明显的热带大陆冰盖或晚奥陶世的极地冰盖的气候状况类型之间的可能联系至关重要。

Chemical sediments dominated by iron(III) oxides are a manifestation of the unique combination of abundant free oxygen and liquid water found in the surface and many near-surface environments of Earth. Research performed in this laboratory has shown that the stable isotope ratios of oxygen, hydrogen and carbon in certain iron(III) oxides contain information on ancient temperatures, sources of water and organic contributions to aqueous carbonate systems associated with iron(III) oxide precipitation. In addition trapped CO2 abundance data from geothites may be related to ambient CO2 partial pressures at the time of mineral formation. The oxygen isotope systematics of ubiquitous phosphate-iron(III) oxide pairs will be studied to determine if they contain information on paleotemperatures. Knowledge obtained from this and our previous studies of iron(III) oxides will be applied to isotopic, chemical and attendant petrographic investigations of Phanerozoic oolitic ironstones, recent bacterially mediated iron(III) oxide precipitate and Late Precambrian banded iron formation(BIF). Fe(III) carbonate abundance and carbon-13 variations in a Late Ordovician weathering surface could provide knowledge of ambient CO2 partial pressures and the role of organic matter in this ancient environment. Oxygen, hydrogen and carbon abundance and isotopic data from tropical oolitic ironstones that date from global "greenhouse" and "icehouse" intervals in the Phanerozoic will be obtained. The ancient tropical temperatures and sources of water will be compared for the deposits that represent these putative global climatic extremes. Oxygen isotopic measurements of a Late Precambrian quartz-hematite BIF should provide insight into the depositional environment of this deposit. Paleoclimatic data of the type to be obtained in this research are essential to an ultimate understanding of the possible link between global tectonics and the types of climatic regimes that could produce apparent tropical continental ice sheets in the Late Precambrian or polar ice sheets in the Late Ordovician.