Noble Gas, Halogen and Water Recycling into the Terrestrial Mantle

稀有气体、卤素和水回收进入地幔

基本信息

批准号：
NE/G018014/1
负责人：
Christopher Ballentine
金额：
$ 58.52万
依托单位：
University of Manchester
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FG018014%2F1
关键词：
Noble Gas Halogen Water Recycling

项目摘要

Incompatible and volatile elements like noble gases and the halogens are continually brought from the mantle to the Earth's surface at mid ocean ridges and other regions of volcanic activity. It has always been assumed that this is a one-way process for these species. This assumption is made when using these tracers to investigate planetary volatile origin, accretionary processes, mantle dynamics and atmosphere evolution in the case of the noble gases, or tracking the halogen budget of the oceans and assessing the role of ocean salinity in the evolution and sustenance of life in the oceans. Recent Manchester work suggests that surface noble gases are being subducted into the deep mantle and that this source dominates the mantle heavy noble gas budget (Ballentine et al., Nature 2005; Holland and Ballentine, Nature 2006). What is surprising is that the mantle shows an Ar/Kr/Xe signature identical to that of seawater. This is an elemental/isotopic composition unique in the solar system and we can rule this out as an original accretionary mantle component. Because of the volatile nature of noble gases we might expect this seawater ratio to be perturbed during the process of subduction. What then is the mechanism that preserves the seawater signature? Where in the oceanic crust are these gases found? How and why are they preserved in the subducting slab? We present new pilot data in our proposal showing that we can identify the same seawater signature in fluids released from dewatering slabs that have been taken to at least 100km depth in the mantle. With a technique pioneered at Manchester, we also show that the halogens in this fluid, which are equally susceptible to fractionation, are identical to values found in marine pore fluids. It would appear that noble gas and halogen subduction are linked. We propose the first complete and systematic analytical survey of the oceanic crust and associated sediment to identify the location and elemental character of the phases or hosts that dominate the noble gas and halogen budget of subducting material. For little extra effort we will also obtain the abundance and hydrogen isotopic composition of the associated water. We also propose to extend the pilot study results to two more terrains, with contrasting thermal regimes, where we expect to be able to sample and identify the noble gas and halogen composition of deep (~100km) subducted fluids. This combined data set will be the first to link noble gases, halogens and related water in a systematic way from subducting to subducted fluid composition in differernt thermal settings. This will enable us to identify the major carrier/ers of noble gas into the mantle and use our understanding of noble gas concentrations and convection behaviour in the mantle to start to model and identify the associated subducted halogen and water impact on the respective total mantle budget and the evolution of these tracers in the mantle system - systems that underpin our understanding of the Earth.

惰性气体和卤素等不相容的挥发性元素不断地从地幔带到大洋中脊和其他火山活动区域的地球表面。人们一直认为这对这些物种来说是一个单向过程。当使用这些示踪剂研究惰性气体的行星挥发物起源、增生过程、地幔动力学和大气演化，或跟踪海洋的卤素预算并评估海洋盐度在演化和维持中的作用时，会做出这一假设海洋中的生命。最近曼彻斯特的工作表明，地表惰性气体正在俯冲到地幔深处，并且该来源主导了地幔重惰性气体的预算（Ballentine 等人，Nature 2005；Holland 和 Ballentine，Nature 2006）。令人惊讶的是，地幔显示出与海水相同的 Ar/Kr/Xe 特征。这是太阳系中独特的元素/同位素成分，我们可以将其排除为原始增生地幔成分。由于稀有气体的挥发性，我们可能预计海水比例在俯冲过程中会受到扰动。那么，保存海水特征的机制是什么？这些气体是在洋壳的什么地方发现的？它们如何以及为何保存在俯冲板片中？我们在提案中提供了新的试点数据，表明我们可以在从地幔至少 100 公里深度的脱水板释放的流体中识别出相同的海水特征。通过曼彻斯特首创的技术，我们还表明，这种流体中的卤素同样容易发生分馏，与海洋孔隙流体中的卤素值相同。看来稀有气体和卤素俯冲是相关的。我们提出对洋壳和相关沉积物进行首次完整、系统的分析调查，以确定主导俯冲物质惰性气体和卤素预算的相或主体的位置和元素特征。只需付出很少的额外努力，我们还可以获得伴生水的丰度和氢同位素组成。我们还建议将试点研究结果扩展到另外两个具有对比热状况的地形，我们希望能够在其中采样并识别深（约 100 公里）俯冲流体的稀有气体和卤素成分。该组合数据集将是第一个以系统的方式将稀有气体、卤素和相关水从俯冲到不同热环境下俯冲流体成分联系起来的数据集。这将使我们能够识别进入地幔的惰性气体的主要载体，并利用我们对地幔中惰性气体浓度和对流行为的理解来开始建模和确定相关的俯冲卤素和水对各自总地幔预算的影响以及这些示踪剂在地幔系统中的演化，地幔系统支撑着我们对地球的理解。

项目成果

期刊论文数量（7）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Halogen Heterogeneity in the Lithosphere and Evolution of Mantle Halogen Abundances Inferred From Intraplate Mantle Xenoliths

岩石圈卤素异质性及板内地幔捕虏体推断的地幔卤素丰度演化

DOI：
http://dx.10.1029/2018gc007903
发表时间：
2019
期刊：
Geochemistry, Geophysics, Geosystems
影响因子：
0
作者：
Kobayashi M
通讯作者：
Kobayashi M

The contribution of hydrothermally altered ocean crust to the mantle halogen and noble gas cycles

热液蚀变洋壳对地幔卤素和稀有气体循环的贡献

DOI：
10.1016/j.gca.2016.03.014
发表时间：
2016-06-15
期刊：
Geochimica et Cosmochimica Acta
影响因子：
5
作者：
D. Chavrit;R. Burgess;H. Sumino;D. Teagle;G. Droop;Aya Shimizu;C. Ballentine
通讯作者：
C. Ballentine

Disequilibrium degassing model determination of the 3He concentration and 3He/22Ne of the MORB and OIB mantle sources

MORB和OIB地幔源3He浓度和3He/22Ne的不平衡脱气模型测定