Ancient Atmospheric P(CO2), Paleoclimates and the Stable Isotope Geochemistry of Low Temperature Iron Oxides

二氧化碳作为一种“温室”气体在地球上的实际作用 只能从古代大气的代用数据中了解过去 二氧化碳分压和相应的气候温度。 进行的研究 在这个实验室发现氧同位素系统学 普通矿物针铁矿（a-FEOOH）使其成为合适的 古温度和古代水源的指示器。 此外，我们还发现针铁矿含有一种明显的 固溶体中的Fe（CO 3）OH组分，其丰度与 到古环境二氧化碳分压 这些自然的特征 针铁矿被用来推断热带温度， 4.4亿年前的大气二氧化碳压力 针铁矿的这些性质的更广泛的应用是 计划好了 这项工作的一部分很好地涉及实验研究的 针铁矿中Al替代Fe的同位素效应 等 同位素古气候研究中重要信息 涉及针铁矿在热带土壤中，其中程度的铝 取代度可以很高。 另一部分研究计划 将进行氧同位素系统学的研究， 针铁矿+磷酸盐作为一种有前途的矿物对氧同位素 古温度计 土壤的双组分CO2混合模型（如 表现在表面活性剂针铁矿的Fe（CO 3）OH组分中）将 作为研究的第三个方面， 从活跃的新生代红土中的针铁矿中获得。 含针铁矿的中生代鲕状铁矿石和红土也将 是同位素的，等等，分析以评估古代温度， 水资源和可能的大气CO2压力。

The actual role of CO2 as a "greenhouse" gas in the Earth's past can only be learned from proxy data on ancient atmospheric Pco2 and corresponding climatic temperatures. Research conducted in this laboratory has found that the oxygen isotope systematics of the common mineral goethite (a-FEOOH) make it a suitable indicator of paleotempeatures and ancient sources of water. Furthermore, we have discovered that goethite contains an apparent Fe(CO3)OH component in solid solution whose abundance is related to ancient ambient Pco2. These characteristics of natural goethites have been used to deduce tropical temperatures and atmospheric CO2 pressures 440 million years ago. A broader application of these properties of goethite is planned. Part of the work well involve experimental study of the isotopic effects of substitution of Al for Fe in goethite. Such information is of importance to isotopic paleoclimatic research involving goethites in tropical soils, where degrees of Al substitution can be high. another portion of the proposed research will undertake the study of the oxygen isotope systematics of goethite + phosphate as a promising mineral pair oxygen isotope paleothermometer. The two-component CO2 mixing model for soils (as manifested in the Fe(CO3)OH component of surficial goethite) will be tested further as a third aspect of the research with data obtained from goethite in active Cenozoic laterites. Goethite-bearing Mesozoic oolitic ironstones and laterite will also be isotopically, etc., analyzed to evaluate ancient temperatures, water sources and possibly atmospheric CO2 pressures.