(GRGC) Oxygen and Hydrogen Isotope Geochemistry of Soil Minerals: Implications for Paleoclimatology and Pedology.

9418970 撒文 拟议的工作是正在进行的土壤矿物和土壤水的氧和氢同位素地球化学研究的继续。 这项工作的主要近期目标是了解不同成土矿物（特别是粘土矿物和氧化物）的同位素组成与风化环境气候之间的关系。 这项研究的一个主要长期目标是将这些关系应用于从古土壤中矿物的同位素组成重建古代大陆气候。 另一个目标是增加对土壤矿物质形成和改变过程的了解。 拟议的研究是独特的，因为它将土壤矿物的同位素组成的测量土壤沃茨和降水的同位素组成。 土壤矿物的研究开始，在进行同位素分析的相分离之前，要进行非常仔细的野外、岩石学和矿物学检查。 这些研究将包括扩大已完成的亚马逊红土高岭石氧同位素组成的工作。 来自同一剖面同一成壤相的其他土壤矿物（特别是三水铝石、氧化钛和氧化铁） 被分析用于 180. 将分析所有含氢相， D. 土壤矿物研究还将包括对弗吉尼亚州皮埃蒙特火成岩上发育的各种腐泥土进行分析，并与喷气推进实验室和加州理工学院的同事合作，对科哈拉半岛（夏威夷）沿着气候梯度（降雨量随着海拔从每年20厘米增加到150厘米）玄武岩上发育的土壤矿物的稳定同位素系统学进行调查。 将在一年的时间内对所研究的每一土壤剖面（巴西、弗吉尼亚皮埃蒙特、夏威夷）的土壤水和（如有可能）降水的同位素地球化学进行监测。 土壤水同位素地球化学的工作将侧重于分析非饱和带中的液态水相（而不是像大多数以前的研究那样分析总水）。 当土壤水同位素数据与成土矿物的同位素组成相联系时，这是一个重要的区别。 将使用的分析技术是在本补助期内开发的。 这是一种基于实验室的二氧化碳平衡技术。 还计划开展更多的工作，根据对土壤CO2的分析， 当土壤水被分成液相和其它组分时发生的同位素分馏（例如，吸附水）。

9418970 Savin The proposed work is a continuation of ongoing research into the oxygen and hydrogen isotope geochemistry of soil minerals and soil water. The primary immediate goal of the work is to understand the relationships between the isotopic compositions of different pedogenic minerals (especially clay minerals and oxides) and the climate of the weathering environment. A major long term goal of the research is to apply those relationships in the reconstruction of ancient continental climates from the isotopic compositions of minerals in paleosols. An additional goal is to obtain increased insight into the processes involved in the formation and modification of soil minerals. The proposed study is unique in that it will relate measurements of the isotopic composition of pedogenic minerals to the isotopic composition of soil waters and precipitation. Studies of soil minerals begin with very careful field, petrologic and mineralogic examination prior to separation of phases for isotopic analysis. These studies will include an extension of completed work on the oxygen isotopic compositions of Amazonian lateritic kaolinites. Other soil minerals (especially gibbsite, titanium oxides, and iron oxides) from the same pedogenic facies of the same profiles will be analyzed for 18O. All hydrogen-containing phases will be analyzed for D. Studies of soil minerals will also include analysis of a variety of saprolites developed on igneous rocks in the Virginia Piedmont and , in collaboration with colleagues at JPL and Caltech, investigation of the stable isotope systematics of soil minerals developed on basalt on the Kohala Peninsula (Hawaii) along a climatic gradient (rainfall increasing with altitude from 20 cm to 150 cm per year. The isotope geochemistry of soil water and, where possible, precipitation, will be monitored over the course of a year at each of the soil profiles which are studied (Brazil, Virginia Piedmont, Hawaii). Work on the isot ope geochemistry of soil water will focus on the analysis of the liquid water phase (rather than total water as in most previous studies) in the unsaturated zone. This is important distinction when the soil water isotopic data are to be related the isotopic compositions of pedogenic minerals. The analytical technique to be used was developed in the current grant period. It is a laboratory-based CO2 equilibration technique. Additional work is planned on the development and verification of an in situ technique based upon the analysis of soil CO2 and upon the isotopic fractionations that occur when soil water is partitioned into a liquid phase and other components (e.g., adsorbed water).