Isotopic Studies of Mantle-Crust Evolution

小行星9614471 初步提出的研究旨在进一步发展一种新的方法，U-Th-Pb地质年代学，并评估其适用于洋底玄武岩。 这项新技术可能有助于更好地了解深海火山活动的时间框架。 建议的工作包括精确测量206 Pb/207 Pb和208 Pb/207 Pb，以及U/Pb和Th/Pb在选定的海底玄武岩的矿物，玻璃和基质分离，以确定该方法的适用性。 本研究计划评价大洋玄武岩是否满足206 Pb/207 Pb和208 Pb/207 Pb均匀的必要初始条件，并将同一岩石的U-Pb和Th-Pb年龄与Ar-Ar年龄测定进行比较，以确定其可靠性。 另外两个二级项目将继续进行。 第一个项目将利用玄武熔岩的地层时间序列数据，定量评估部分熔融区的水文特性，以更好地了解熔融区分散和色谱法在地幔同位素变化研究中的作用。 第二个项目旨在验证太古代早期地幔中分馏地幔储层的证据，并量化重建变质太古代岩石初始同位素和化学成分的方法。

9614471 DePaolo The primary proposed research is aimed at further developing a new approach to U-Th-Pb geochronology, and assessing its applicability to ocean floor basalts. The new technique may allow for improved understanding of the temporal framework of deep sea volcanism. The proposed work involves precisely measuring 206Pb/207Pb and 208Pb/207Pb, and U/Pb and Th/Pb in mineral, glass and groundmass separates of selected submarine basalts to determine the applicability of the method. The plan is to evaluate whether the necessary initial condition of uniform 206Pb/207Pb and 208Pb/207Pb is satisfied in oceanic basalts, and to compare the U-Pb and Th-Pb dates from the same rocks to Ar-Ar age determinations to establish its reliability. Two other secondary projects will be pursued. The first will use stratigraphic time-series data from basaltic lavas to quantitatively assess the hydrological properties of partial melt zones to better understand the role of melt zone dispersion and chromatography in the study of isotopic variations in the mantle. The second project is aimed at verifying the evidence for fractionated mantle reservoirs in the early Archean mantle and quantifying approaches for reconstructing the initial isotopic and chemical compositions of metamorphosed Archean rocks.