Noble Gas, Halogen and Water Recycling into the Terrestrial Mantle

稀有气体、卤素和水回收进入地幔

• 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

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.

在大洋中脊和其他火山活动区，稀有气体和卤素等不相容和易挥发的元素不断从地幔带到地球表面。人们一直认为，这对这些物种来说是一个单向的过程。在使用这些示踪剂研究行星的挥发性起源、吸积过程、地幔动力学和大气演化的情况下，或在追踪海洋的卤素收支和评估海洋盐度在海洋生命演化和维持方面的作用时，作出了这一假设。曼彻斯特最近的研究表明，地表惰性气体正被俯冲到地幔深处，这一来源主导着地幔重惰性气体的收支(Ballentine等人，《自然》2005年；荷兰和Ballentine，《自然》2006年)。令人惊讶的是，地幔显示出与海水相同的Ar/Kr/Xe特征。这是太阳系独有的元素/同位素组成，我们可以排除它是原始的吸积地幔成分。由于惰性气体的挥发性，我们可能会认为这个海水比例在俯冲过程中会受到干扰。那么，保存海水特征的机制是什么呢？这些气体是在洋壳的什么地方发现的？它们是如何以及为什么保存在俯冲板中的？我们在提案中提供了新的试点数据，表明我们可以在地幔深度至少100公里的脱水板材释放出的流体中识别出相同的海水特征。利用曼彻斯特首创的一项技术，我们还表明，这种流体中同样容易受到分馏影响的卤素，与在海相孔隙流体中发现的值相同。看来惰性气体和卤素俯冲是有联系的。我们建议对洋壳及其伴生沉积物进行首次全面和系统的分析调查，以确定控制俯冲物质惰性气体和卤素收支的相或宿主的位置和元素特征。只需很少的额外工作，我们还可以获得相关水的丰度和氢同位素组成。我们还建议将初步研究结果扩展到另外两个热状况不同的地形，在那里我们有望能够采样和识别深部(约100公里)俯冲流体的惰性气体和卤素成分。这一组合数据集将首次以系统的方式将惰性气体、卤素和相关水联系起来，从俯冲到不同热环境中的俯冲流体成分。这将使我们能够确定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了解，开始模拟和确定相关的俯冲卤素和水对各自的地幔总预算的影响以及这些示踪剂在地幔系统中的演化--这些系统支撑着我们对地球的理解。

项目成果

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

• DOI: 10.1016/j.epsl.2014.11.021
• 发表时间: 2015
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Weston B

Slab-derived halogens and noble gases illuminate closed system processes controlling volatile element transport into the mantle wedge

板片衍生的卤素和稀有气体照亮了控制挥发性元素传输到地幔楔的封闭系统过程

• DOI: 10.1016/j.epsl.2016.10.012
• 发表时间: 2017
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Kobayashi M

Eclogitic metagabbro from the Lanzada Window, eastern Central Alps: confirmation of subduction beneath the Malenco Unit

• DOI: 10.1007/s00015-014-0162-z
• 发表时间: 2014-08
• 期刊: Swiss Journal of Geosciences
• 影响因子: 3.1
• 作者: G. Droop;D. Chavrit

Halogen behaviour in subduction zones: Eclogite facies rocks from the Western and Central Alps

• DOI: 10.1016/j.gca.2018.09.024
• 发表时间: 2018-12
• 期刊: Geochimica et Cosmochimica Acta
• 影响因子: 5
• 作者: L. Hughes;R. Burgess;D. Chavrit;A. Pawley;R. Tartèse;G. Droop;C. Ballentine;I. Lyon

Seawater-derived noble gases and halogens preserved in exhumed mantle wedge peridotite

• DOI: 10.1016/j.epsl.2010.03.029
• 发表时间: 2010-05
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: H. Sumino;R. Burgess;T. Mizukami;S. Wallis;G. Holland;C. Ballentine