RUI: Integrated Strain and Fluid Composition, Temperature and Pressure Histories of Orogens

RUI：造山带的综合应变和流体成分、温度和压力历史

• 批准号: 0409390
• 负责人: William Peck
• 金额: --
• 依托单位: Colgate University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409390&HistoricalAwards=false
• 关键词: RUI; Integrated; Strain; Fluid; Composition

The investigators present a plan of research aimed at determining the strain, fluid composition, fluid temperature and fluid pressure history of orogenic belts. The presence of fluids and fluid pressure are believed to exert strong controls on a variety of tectonic phenomena, including earthquake cyclicity, the geometry of accretionary prisms and both brittle and ductile rock deformation. Fluid migration is also a significant factor in the transfer of heat and matter in the lithosphere and is one of the more significant factors in the formation of mineral deposits. However, determining the nature and conditions of fluids at depth in actively deforming regions remains highly difficult. Even when drilling does yield information about fluid composition, temperature and pressure we are given only a brief snapshot rather than an indication of possible fluid variations over geologic time. Some information has been gleaned from the study of fluid inclusions and stable isotopes in veins, but the timing and duration of vein formation in a structural sequence is obscure in most cases. The PI's propose that analysis of fluid inclusions and stable isotopes in fibrous strain fringes around rigid objects is the best way to get a nearly complete record of fluid conditions over the course of orogeny. They have conducted an incremental strain, stable isotope and fluid inclusion study of some unusually large strain fringes in the Taconic slate belt of Vermont and New York, with interesting results. The data indicate a very strong correlation between the directions of principal elongation and fluid pressure and temperature. Their methods rely, however, on being able to serially section the strain fringes and measure O isotopes in coexisting quartz and calcite using laser fluorination of quartz and carbonate dissolution. This precludes using most strain fringes, because they are either too small or contain other minerals, such as chlorite or white mica. Stable isotope analyses of such features become quite difficult because pure mineral separates in small volume must be produced. The PI's propose using the ion microprobe to overcome these drawbacks. Doing so will allow unprecedented spatial resolution in large strain fringes and will allow the use of smaller strain fringes as well. They will also be able to use strain fringes with more mineralogical diversity, opening up new avenues for research. They propose performing a test of this method by conducting both silicate laser fluorination and carbonate dissolution stable isotope analyses along with ion microprobe stable isotope analyses on identical samples of unusually large strain fringes from the Taconics. Following this, they will expand their geographic coverage in the Taconics to test the hypothesis that strain and fluid conditions are inter-related and controlled by motion on the Bird Mountain thrust fault. They will also analyze samples from well studied sites in the Pyrenees and Helvetic Alps, with both very simple and complex strain histories. The PI's believe that this work will demonstrate the utility of this approach, opening new avenues to other workers. They also plan to include undergraduates in the research and contend that this will provide a stimulating and significant research experience for three students each summer. Each year one student will work on each aspect of the research; incremental strain, fluid inclusion and stable isotope analysis, working in close collaboration with one of the PI's. Broader impacts of the proposed work include expanding the utility of the ion microprobe, taking full advantage of NSF-purchased stable isotope and SEM instrumentation at Colgate, exposure of undergraduates to research, inclusion of faculty from an undergraduate institution in research and expansion of techniques available for the study of orogenic fluids.

研究人员提出了一项研究计划，旨在确定造山带的应变、流体成分、流体温度和流体压力历史。 流体和流体压力的存在被认为对各种构造现象施加强有力的控制，包括地震周期性、增生棱柱体的几何形状以及脆性和韧性岩石变形。 流体运移也是岩石圈中热量和物质传递的重要因素，是矿床形成的重要因素之一。 然而，确定活跃变形区域深处流体的性质和条件仍然非常困难。 即使钻井确实产生了关于流体成分、温度和压力的信息，我们也只能得到一个简短的快照，而不是地质时期可能的流体变化的指示。 通过对脉体中流体包裹体和稳定同位素的研究已经获得了一些信息，但在大多数情况下，构造层序中脉体形成的时间和持续时间是模糊的。 PI建议，分析刚性物体周围纤维状应变条纹中的流体包裹体和稳定同位素是在地壳运动过程中获得几乎完整的流体条件记录的最佳方法。 他们对佛蒙特州和纽约的塔科尼克板岩带中一些异常大的应变边缘进行了增量应变、稳定同位素和流体包裹体研究，得到了有趣的结果。 这些数据表明，主伸长方向与流体压力和温度之间有很强的相关性。 然而，他们的方法依赖于能够连续地分割应变条纹，并使用石英和碳酸盐溶解的激光衍射来测量共存的石英和方解石中的O同位素。 这就排除了使用大多数应变条纹，因为它们要么太小，要么含有其他矿物质，如云母或白色云母。 对这些特征的稳定同位素分析变得相当困难，因为必须生产小体积的纯矿物分离物。 PI建议使用离子探针来克服这些缺点。 这样做将允许在大应变条纹中实现前所未有的空间分辨率，并且还将允许使用较小的应变条纹。 他们还将能够使用具有更多矿物多样性的应变条纹，为研究开辟新的途径。 他们建议通过对Taconics异常大应变条纹的相同样品进行硅酸盐激光散射和碳酸盐溶解稳定同位素分析沿着离子微探针稳定同位素分析来测试该方法。 在此之后，他们将扩大他们在Taconics的地理覆盖范围，以测试应变和流体条件是相互关联的，并由鸟山逆冲断层上的运动控制的假设。 他们还将分析来自比利牛斯山和海尔维蒂阿尔卑斯山研究地点的样本，包括非常简单和复杂的应变历史。 PI相信这项工作将证明这种方法的实用性，为其他工人开辟新的途径。 他们还计划将本科生纳入研究，并认为这将为每年夏天的三名学生提供一个刺激和重要的研究经验。 每年将有一名学生从事研究的各个方面;增量应变、流体包裹体和稳定同位素分析，并与其中一位PI密切合作。 拟议工作的更广泛的影响包括扩大离子微探针的效用，充分利用NSF购买的稳定同位素和高露洁的SEM仪器，使本科生接触研究，将本科院校的教师纳入研究和扩大可用于造山流体研究的技术。