Reduction of Systematic Errors in 40Ar/39Ar Geochronology

9814378 renne这项拨款支持旨在提高高度精确和非常广泛使用的40Ar/39Ar地质年代学方法准确性的研究。该方法的精度通常优于0.1%，但由于衰变常数、标准数据和钾的同位素组成的系统误差，使该方法的绝对精度限制在2%以下。在这个项目中，研究人员将对精心挑选的样品进行40Ar/39Ar和U-Pb方法的详细比较，这些样品没有地质复杂性。在理想情况下，U-Pb方法的精度约为0.3%，因此通过互标定，40Ar/39Ar体系可以获得接近该极限的精度。这项工作将与实验结合起来，通过详细分析公元79年维苏威火山历史性喷发中富含钾的矿物，首次用现代历法校准40Ar/39Ar年代标准。该项目的预期结果是40Ar/39Ar定年方法精度的十倍或更好的改进

9814378RenneThis grant supports research aimed at improving the accuracy of the highly precise and very widely used 40Ar/39Ar method of geochronology. Precision of the method is often better than 0.1%, but systematic errors from decay constants, data for standards, and the isotopic composition of potassium combine to limit the method's absolute accuracy to no better than 2%. In this project, the investigators will conduct detailed comparisons between 40Ar/39Ar and U-Pb methods for carefully selected samples that are free of geologic complexities. In ideal cases, the U-Pb method is accurate to about 0.3%, thus accuracy approaching this limit may be obtained for the 40Ar/39Ar system through intercalibration. This work will be combined with experiments that will calibrate 40Ar/39Ar dating standards for the first time with the modern calendar through detailed analysis of potassium-rich minerals from the historic eruption of Vesuvius in 79 AD. The expected results of the project are a factor of ten or better improvement in accuracy of the 40Ar/39Ar dating method.***