Terrestrial 107Pd-107Ag Systematics: Implications for Mantle Circulation, Core-Mantle Exchange and the Age of the Earth

0229417豪利利用这笔赠款给华盛顿卡内基研究所地磁系的资金，分析了各种各样的地磁的银浓度和同位素组成。（洋中脊玄武岩、洋岛玄武岩、太古代科马提岩、肥沃地幔橄榄岩捕虏体、和各种地壳岩石）和外星人（主要是整个岩石）材料将进行，以探讨的可能性，107钯/~（107）Ag放射性测量系统可用于揭示地球形成和地核与地幔分离的详细年代学。 107 Pd衰变为107 Ag，半衰期为650万年。 因此，Pd-Ag同位素系统只对太阳系历史的前6000万年发生的事件敏感。 PI开发的用于Ag同位素测定的新MC-ICPMS分析技术与以前使用的方法相比，允许同位素比精度提高10-20倍。 如果观测到银同位素组成的变化可能与107钯衰变有关，那么地球在太阳系形成的50-60百万年内一定经历了显著的地球化学分化。 另一方面，如果观测到的银的变化是由于质量分馏，那么地球的挥发性元素耗尽，和地球核心的形成，必须发生在太阳系形成后60百万年。 一名博士后助理将被雇用和培训，以协助持续发展的化学和质谱程序的银同位素分析，并将协助我们传播这种特殊的技术，和其他新技术的同位素分析等离子体质谱仪，更广泛的地球科学界。

0229417HauriUsing funds from this grant to the Carnegie Institution of Washington - Department of Terrestrial Magnetism, analyses of the Ag concentration and isotopic composition of a wide variety of terrestrial (mid-ocean ridge basalts, ocean island basalts, Archean komatiites, fertile mantle peridotite xenoliths, and assorted crustal rocks) and extraterrestrial (primarily whole rock chondrites) materials will be undertaken in order to explore the possibility that the 107Pd/107Ag radiometric system can be used to reveal the detailed chronology of Earth formation and the separation of its core from the mantle. 107Pd decays to 107Ag with a half-life of 6.5 Myr. The Pd-Ag isotope system is thus sensitive to events occurring only during the first 60 Myr of solar system history. A new MC-ICPMS analytical technique for Ag isotopic determinations, developed by the PI's, allows a factor of 10-20 improvement in isotope ratio precision compared to previously utilized approaches. If variations in Ag isotopic composition are observed that can be related to 107Pd decay, then Earth must have experienced significant geochemical differentiation within 50-60 Myr of solar system formation. Alternatively, if the observed Ag variation is due only to mass fractionation, then the volatile-element depletion of Earth, and terrestrial core formation, must have occurred 60 Myr after solar system formation. A post-doctoral associate will be employed and trained to assist with continued development of the chemical and mass spectrometric procedures for Ag isotopic analysis, and will assist us in disseminating this particular technique, and other new techniques for isotope analysis by ICP-MS, to the broader earth science community.