权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Terrestrial Applications of the Triple Oxygen Isotope Geothermometer

三重氧同位素地温计的陆地应用

基本信息

批准号：
1551226
负责人：
Zachary Sharp
金额：
$ 25.99万
依托单位：
University of New Mexico
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2016
资助国家：
美国
起止时间：
2016-03-01 至 2020-02-29
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1551226&HistoricalAwards=false
关键词：
Terrestrial Applications Triple Oxygen Isotope

项目摘要

The oxygen isotope compositions of natural materials have been used for over 60 years as a quantitative 'thermometer' for ancient rock and mineral samples. The difference in the oxygen isotope composition (the 18O/16O ratio) of a mineral and the water from which it formed provides a temperature estimate that has a precision of ~1°C. The problem with application of this method to ancient samples is that the water - usually ocean water - is not preserved in the rock and needs to be inferred. This introduces some ambiguity to the derived paleotemperature estimate. Namely, was the oxygen isotope composition of the ocean water at the time the mineral formed the same as it is today? Researchers have been tackling this question for decades, and it is still unresolved. In this proposal, the team will use a novel, previously untried, technique in which all three naturally occurring oxygen isotopes are used for temperature determinations. It has long been thought that the rare isotope 17O provides no additional information to the commonly measured 18O/16O ratios. More recently, this team and other research groups have shown that there are subtle differences in the way temperature affects the 18O/16O and 17O/16O ratios. By accurately measuring all three isotopes, 16O, 17O and 18O, it is proposed to eliminate the uncertainties inherent in using the 18O/16O ratios alone. This award will help support the graduate theses of two students, one of whom is a woman, the other a minority. It will also include research opportunities for an undergraduate student, allowing them hands-on access to sophisticated laboratory equipment. Such an opportunity is invaluable for young potential scientists. Both the investigator and the graduate students will work closely with undergraduate students recruited over the three year time frame of this project. This is a new research avenue and there are many outstanding questions. As part of our research, they will calibrate the temperature dependence on the 18O/16O and 17O/16O ratios of quartz and water by experimentally equilibrating a quartz-water mixture at high temperatures and pressures. They will expand the preliminary tests of the technique to the very important mineral calcite. Marine carbonates are ubiquitous in the rock record, and if the approach works for calcite it will vastly expand the research potential of this new technique. Unfortunately, the analysis of calcite for 17O/16O ratios has proven to be very difficult. This research group will initially spend time conducting analytical tests to quantifying this measurement and reproduce it for a standard. Once the methodology is further established, they will proceed to analyze some of the most pristine, ancient samples in order to test the age-old question 'Is the oxygen isotope composition of ancient seawater the same as it is today?' At the same time, they will apply this work to high temperature systems as a way of retrieving both temperatures and fluid compositions (sources) in hydrothermal systems. This work will have important applications to the economic geology community which strives to understand how mineral deposits form.

天然物质的氧同位素组成作为古代岩石和矿物样品的定量“温度计”已经使用了60多年。矿物的氧同位素组成（18 O/16 O比率）与其形成的水的差异提供了约1°C精度的温度估计。将这种方法应用于古代样品的问题是，水-通常是海水-没有保存在岩石中，需要进行推断。这就给古温度的估计带来了一些模糊性。也就是说，矿物形成时海水的氧同位素组成与今天相同吗？几十年来，研究人员一直在解决这个问题，但它仍然没有得到解决。在这项提议中，研究小组将使用一种新的、以前从未尝试过的技术，其中所有三种天然存在的氧同位素都用于温度测定。长期以来，人们一直认为稀有同位素17 O对通常测量的18 O/16 O比率没有提供额外的信息。最近，该团队和其他研究小组已经表明，温度影响18 O/16 O和17 O/16 O比值的方式存在细微差异。通过精确测量所有三种同位素16 O、17 O和18 O，建议消除单独使用18 O/16 O比值所固有的不确定性。该奖项将帮助支持两名学生的研究生论文，其中一名是妇女，另一名是少数民族。它还将包括本科生的研究机会，使他们能够亲自使用先进的实验室设备。这样的机会对年轻的潜在科学家来说是无价的。研究人员和研究生将与本项目三年时间框架内招募的本科生密切合作。这是一个新的研究方向，有许多悬而未决的问题。作为我们研究的一部分，他们将通过在高温和高压下实验平衡石英-水混合物来校准石英和水的18 O/16 O和17 O/16 O比率对温度的依赖性。他们将把这项技术的初步试验扩大到非常重要的矿物方解石。海洋碳酸盐在岩石记录中无处不在，如果这种方法适用于方解石，它将极大地扩展这种新技术的研究潜力。不幸的是，方解石的17 O/16 O比分析已被证明是非常困难的。该研究小组最初将花费时间进行分析测试，以量化该测量并将其复制为标准。一旦方法进一步建立，他们将继续分析一些最原始的古代样本，以测试古老的问题“古代海水的氧同位素组成与今天相同吗？”同时，他们将把这项工作应用于高温系统，作为一种在热液系统中检索温度和流体成分（来源）的方法。这项工作将对努力了解矿床如何形成的经济地质界产生重要应用。