Tungsten and Ruthenium Isotopic Study of the Chemical Evolution of Earth

地球化学演化的钨和钌同位素研究

基本信息

批准号：
1624587
负责人：
Richard Walker
金额：
$ 46万
依托单位：
University of Maryland, College Park
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2016
资助国家：
美国
起止时间：
2016-07-15 至 2020-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1624587&HistoricalAwards=false
关键词：
Tungsten Ruthenium Isotopic Study Chemical

项目摘要

The Earth was likely built as a result of a series of a series of collisions of increasingly larger planetesimals, during the first 50 million years of Solar System history. Growth of the planet largely terminated after a final, giant impact that led to melting of much of the Earth and the creation of the Moon. Surprisingly, there is strong evidence present in the isotopic compositions of some elements in both ancient and young rocks that domains were created within the Earth?s mantle during the primary construction period of the Earth before the giant impact, and these domains have been somehow preserved to the present. This study will examine the tungsten and ruthenium isotopic compositions of rocks derived from these domains to provide new insights to processes occurring within the Earth as it grew, as well as help to constrain the genetic origins of the building blocks of our planet. Small variations in the abundance of 182-tungsten in terrestrial rocks likely reflects the decay of 182-hafnium, coupled with very early chemical fractionations of the two elements within the silicate portion of the Earth. Prior studies have suggested that modest variations in 182-tungsten among some primitive rocks may reflect processes occurring in early-formed magma oceans. This study will seek to more fully establish the causes of the isotopic heterogeneities, and assess why convective stirring of the mantle has not mixed away the heterogeneities in more than 4.5 billion years. The isotopic composition of Ru varies among planetary bodies in our Solar System as a result of the incorporation of diverse mixtures of nucleosynthetic components. Hence, if the Earth was built from genetically diverse materials, early-formed mantle domains identified by tungsten isotopic variations, may contain ruthenium that is isotopically distinguishable from the dominant composition of the mantle today. If so, the particular building block identified may be tied to a specific type of cosmochemical precursor.

在太阳系历史的前5000万年中，一系列越来越大的行星碰撞可能是由于一系列越来越大的行星碰撞而建造的。在最终的，巨大的影响后，地球的生长在很大程度上终止了，这导致了大部分地球和月球的创造。令人惊讶的是，在巨大撞击之前，在地球的主要建筑期间，在地球上创建了一些元素的同位素组合物中存在有力的证据，这些域已被保存在某种程度上到现在。这项研究将检查源自这些领域的岩石的钨和唯一同位素组成，以为地球随着地球的生长而在地球内发生的过程提供新的见解，并有助于限制我们星球基础的遗传起源。陆地岩石中182个丁香的丰度的微小变化可能反映出182 hafnium的衰变，以及地球硅酸盐部分内两个元素的早期化学分馏。先前的研究表明，在某些原始岩石中，有182种牙的适度变化可能反映了早期形成的岩浆海洋中发生的过程。这项研究将寻求更充分地确定同位素异质性的原因，并评估为什么在超过45亿年内，对流式搅动的震撼尚未消除异质性。 RU的同位素组成在我们太阳系中的行星体之间因核合成成分的各种混合物而变化。因此，如果地球是用遗传多样的材料建造的，则由钨同位素变异鉴定出的早期形成的地幔结构域，可能包含luthenium，与当今地幔的主要成分相同。如果是这样，则确定的特定构件可能与特定类型的宇宙化学前体相关。