Volatile cycling and oxygen fugacity of subduction zones using stable vanadium isotopes

使用稳定钒同位素研究俯冲带的挥发性循环和氧逸度

基本信息

批准号：
NE/H01313X/1
负责人：
Julie Prytulak
金额：
$ 36.73万
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Fellowship
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%2FH01313X%2F1
关键词：
Volatile cycling oxygen fugacity subduction

项目摘要

The outer shell of the Earth that we live on is made up of brittle 'plates'. The migration of these plates across the surface of the planet is directly linked to major geologic events such as earthquakes and volcanic eruptions. In some regions, two plates collide, forcing one beneath the other in a process called 'subduction'. Subduction zones are responsible for much of the explosive volcanism on Earth, including the infamous Pacific 'Ring of Fire'. However, these zones are also critical for the exchange and cycling of chemical elements between the surface and interior of the planet. As an oceanic plate subducts, it is subjected to high pressures and temperatures. During this process, the plate looses chemical components through fluids, degassing, reactions, and sometimes melting. One of the key parameters controlling how much of which elements are lost, is the available oxygen. Geochemists refer to the amount of available oxygen as the 'oxygen fugacity' of a system, which can be simply thought of as the partial pressure of oxygen. Oxygen fugacity has a large affect on the way the carbon (C), hydrogen (H), and other 'volatile' elements behave in a subduction system. Volatiles species (e.g., H2O and CO2) are those that vaporize at low temperatures. Combined with other physical and chemical conditions of subduction, oxygen fugacity controls how much H and C is lost through degassing during explosive volcanism, and how much can be dragged deeper into the Earth. There has been a long-standing debate over how much more oxygenated subduction zones are compared with the rest of the interior of the Earth. The fugacity of samples from subduction zone volcanoes tells us about present day processes and volatile cycling. Furthermore, if subduction zones are significantly more oxygenated than the rest of the interior of the Earth, then they may provide an efficient means of recycling oxygen into the interior of the Earth. Therefore, it is critical to constrain the oxygen fugacity of subduction zones to evaluate the whole Earth cycling of volatile elements and how this may change through time. It is essential to find a robust way of determining oxygen fugacity. Unfortunately, previous studies used methods that can be easily 'reset' by later events, so that they do not give a true indication of the original source. Consequently, there is considerable uncertainty in what the 'real' amount of available oxygen is in subduction systems. My previous research and expertise focused on the novel application of isotopes of chemical elements to solving Earth problems. I have continued in this broad avenue of investigation by working on a precise analytical method for the measurement of vanadium stable isotope variations. The measurements are not trivial, however they are very valuable. The power of vanadium stable isotopes in particular, is that their fractionation should be directly and robustly linked to oxygen fugacity. This fellowship analyses vanadium stable isotope variations in lavas, sediments and deep Earth samples from the Mariana (southwest Pacific), Aleutian (Alaska) and Mexican subduction zones. Through this work, better constraint can be placed on oxygen fugacity and how the Earth system behaves in terms of the fluxes of volatile elements such as carbon and hydrogen between deep and surface reservoirs of the Earth. This will help us tackle far-reaching present day issues related to how the carbon cycle works, and also potentially provide a means of investigating how the amount of oxygen in the Earth has changed over time, its links to the evolution of the atmosphere and ultimately to how our planet became able to sustain life.

我们所生活的地球外壳由脆弱的“板”组成。这些板在整个地球表面的迁移与重大地质事件（例如地震和火山喷发）直接相关。在某些地区，两个板碰撞，在一个称为“俯冲”的过程中迫使另一个板在另一个板上。俯冲带负责地球上许多爆炸性火山，包括臭名昭著的太平洋“火环”。但是，这些区域对于地球表面和内部之间的化学元件的交换和循环也至关重要。作为海洋板的俯冲，它受到高压和温度的影响。在此过程中，板通过液体，脱气，反应，有时甚至融化的化学成分。可用的氧气是控制哪些元素丢失了多少元素的关键参数之一。地球化学主义者将可用的氧气的量称为系统的“氧气散性”，可以简单地将其视为氧气的二压。氧气散热性对碳（C），氢（H）和其他“挥发性”元素的方式具有很大的影响。挥发性物种（例如H2O和CO2）是在低温下蒸发的物种。结合俯冲的其他物理和化学条件，氧气散发性控制了H和C在爆炸性火山爆发过程中通过脱气而损失了多少，可以将多少拖入地球。关于将氧化俯冲带与地球内部的其余部分进行了比较，一直存在一些辩论。俯冲带火山样品的散发性告诉我们当今的过程和挥发性循环。此外，如果俯冲带比地球其他内部的氧化更大，那么它们可能会提供有效的氧气方法，以将氧气回收到地球内部。因此，限制俯冲带的氧散性以评估挥发性元件的整个地球循环以及它如何随时间变化是至关重要的。必须找到一种确定氧散氧的强大方法。不幸的是，以前的研究使用了以后事件可以轻松“重置”的方法，因此它们不会真正表明原始来源。因此，俯冲系统中的“实际”可用氧气是什么不确定性。我以前的研究和专业知识集中在化学元素同位素在解决地球问题上的新型应用上。我通过使用一种精确的分析方法来测量钒稳定的同位素变化，继续进行了这一广泛的调查途径。测量并非微不足道，但是它们非常有价值。钒稳定的同位素的功率尤其是它们的分馏应直接且牢固地与氧气散发性相关。该研究金分析了来自玛丽安娜（西南太平洋），阿留申（Aleutian）（阿拉斯加）和墨西哥俯冲带的熔岩，沉积物和深层样品中的钒稳定的同位素变化。通过这项工作，可以将更好的约束放在氧气散热器上，以及地球系统如何在地球深处和表面储层之间的挥发性元素（例如碳和氢）的通量来表现。这将有助于我们解决与碳循环的工作原理相关的深远的当今问题，并有可能提供一种调查地球中氧气量如何随着时间而变化的方式，其与大气的演变以及最终与我们的星球能够维持生命的方式有联系。

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）

The stable isotope composition of vanadium, nickel, and molybdenum in crude oils

DOI：
10.1016/j.apgeochem.2015.04.009
发表时间：
2015-08
期刊：
Applied Geochemistry
影响因子：
3.4
作者：
G. Ventura;L. Gall;C. Siebert;J. Prytulak;P. Szatmari;M. Hürlimann;A. Halliday
通讯作者：
G. Ventura;L. Gall;C. Siebert;J. Prytulak;P. Szatmari;M. Hürlimann;A. Halliday

Melting versus contamination effects on 238U-230Th-226Ra and 235U-231Pa disequilibria in lavas from São Miguel, Azores

亚速尔群岛圣米格尔熔岩中熔化与污染对 238U-230Th-226Ra 和 235U-231Pa 不平衡的影响