Oxygen and carbon isotopic systematics in the ultra-high temperature metamorphism

超高温变质作用中的氧和碳同位素系统学

基本信息

批准号：
10440160
负责人：
WADA Hideki
金额：
$ 8.9万
依托单位：
Shizuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

Based on the discovery of intracrystalline isotope zonations in metamorphosed marbles a decade ago (Wada, 1988, Nature), we have predicted that such zonation will have far reaching implications on the behavior of metamorphic fluid movement in the Earth's crust right from the micron scale and ending up in a *rustal scale model. This methodology of isotope zonation studies was more refined by using secondary ion mass spectrometer (SIMS) and the results advanced our knowledge on isotope diffusion process in crystals (Graham et al., 1998, Wada a co-author). In this respect, further studies on the fluid flow on marbles with a new emphasis on zonation profiles in high temperature contact metamorphic aureoles were presented at the Goldschmidt conference 2000 at Oxford, UK (Wada, 2000).During this year, we have succeeded in applying the carbon isotope geothermometry in ultrahigh temperature metamorphosed marbles from southern Indian granulite terrain. As shown in Satish-Kumar, M Wada, H and ot … More hers (2001), the temperature conditions were accurately determined for the region based on microscale isotope zonation profiles in calcite and graphite. The temperature conditions of such lower crustal granulites were as high as 1000℃, producing excellent matching with the petrologic mineral assemblages i ncluding the ultrahigh temperature index mineral of sapphirine. Thus the application of carbon isotope thermometry has provided a new tool in estimating accurately the ultrahigh-to high-temperature metamorphic conditions in the deep crust.Another project of this financial support involves the establishing of a precise and detail laser based oxygen extraction system for silicate mineral phases. This utilizes a technique of decomposition of silicate bonds in minerals to separate oxygen using laser ablation in a bromine penta-fluoride atmosphere. The *onstruction of the system is completed and testing the vacuum conditions is underway. The predicted reproducibility of this system will not be as good as for carbonates, where we are now getting a less than 0.1‰ The important hurdles for this low accuracy lies in the oxygen preparation system and in the oxygen to CO2 conversion system. There is necessity for such accurate data in modeling the isotope diffusion profiles and the effect of fluids in such process. In order to achieve accuracy comparable to those we have for carbonates oxygen isotopes should be measured directly, after decomposition from silicate phases. We need a special mass spectrometer designed to measure oxygen isotopes directly from oxygen gas. This will also benefit in elucidating the multiple isotope (16O, 17O ＆ 18O) effect in natural sample Less

基于十年前的变质大理石中晶体内同位素分区的发现（Wada，1988年，自然），我们预测，这种分区将对地球壳中的变质流体运动的行为产生很大的影响，这是从微米尺度与 *Rustal Scale模型结束的。通过使用二级离子质谱仪（SIMS）来更加精炼同位素分区研究的方法，结果提出了我们对晶体中同位素扩散过程的了解（Graham等，1998，Wada，Wada a a a a a a a a theror）。在这方面，对大理石上的流体流动的进一步研究，新的重点是高温接触中的分区变质化变质金黄色蛋白酶，在英国牛津的戈德施密特会议2000会议上（WADA，2000年）。如Satish-kumar，M Wada，h和ot…More Hers（2001）所示，基于钙和石墨中的显微镜同位素分区分析曲线的区域准确确定了温度条件。这种较低的地壳颗粒的温度条件高达1000°，与包括Sapphirine的超高温度指数矿物在内的岩石学矿物组合产生了极好的匹配。这就是碳同位素温度计的应用，为在深层外壳中准确估算超高到高温的变质条件提供了一种新工具。这项财务支持的另一个项目涉及建立用于硅酮矿物相的精确和细节基于激光的氧气提取系统。这利用矿物质中有机硅键的分解技术，在溴五氟化物气氛中使用激光消融分离氧。 *系统的建筑物已完成，测试真空条件正在进行中。该系统的预测可重复性不如碳酸盐那样好，现在我们得到的低于0.1‰的重要障碍在于氧气制备系统以及氧气到二氧化碳转换系统。在这种过程中，这种准确的数据在建模同位素扩散曲线和烟道的影响方面有必要进行这种准确的数据。为了实现与碳酸盐氧同位素相当的精度，应在硅酮相位分解后直接测量氧同位素。我们需要一个特殊的质谱仪，该质谱仪旨在直接从氧气中测量氧同位素。这也将受益于阐明自然样品中的多种同位素（16o，17o和18o）效应