Experimental and Natural Deformation of Magnesian Carbonates

碳酸镁的实验和自然变形

• 批准号: 0911586
• 负责人: Julie Newman
• 金额: $ 39.99万
• 依托单位: Texas A&M Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911586&HistoricalAwards=false
• 关键词: Experimental; Natural; Deformation; Magnesian; Carbonates; Experimental; Natural; Deformation; Magnesian; Carbonates

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Shallow marine carbonate rocks that are deposited at continental margins are subjected to intense deformation at convergent plate boundaries, and a growing body of evidence indicates that these carbonate rocks are entrained in subduction zones to significant mantle depths. By comparison with rocks composed of silicate minerals, rocks composed of carbonates are weak, so that their deformation exerts a strong influence on the structures that develop in mountain belts resulting from continental collisions, and they may also influence deformation in the mantle during subduction. Carbonate rocks are composed largely of the minerals calcite, dolomite, and magnesite. These minerals have similar crystal structures, but are compositionally and mechanically different. While the rheology of calcite has been well established, the rheology of dolomite is less well constrained by experiments, and almost nothing is known about the rheology of magnesite, which is stable to greater depths in the mantle than calcite or dolomite. In order to accurately model deformation processes within the crust and mantle during subduction and mountain building processes, the rheology of dolomite needs to be refined, the rheology of magnesite determined, and then compared to the rheology of calcite. This project will use both experimental and observational approaches to achieve the following: (1) determine the rheology for dislocation creep of dolomite through experiments, in a triaxial rock deformation apparatus, to establish the temperature and strain rate dependence of this deformation mechanism in dolomite; (2) determine the mechanical properties of magnesite through experiments, in a triaxial rock deformation apparatus, over a wide range of pressures, temperatures and strain rates to establish the ranges of temperature and strain rate over which different deformation mechanisms operate; (3) investigate the microstructures and fabrics formed in experimentally shortened and sheared dolomite; and (4) compare the microstructures and fabrics formed during experimental deformation with those observed in natural dolomite shear zones to provide the foundation to apply laboratory determined rheologies to nature.This research will investigate, through deformation experiments and analyses of rocks deformed in nature, the strength and deformation processes of the carbonate minerals, dolomite and magnesite. Carbonate-bearing rocks make up a significant portion of the rocks that are deformed during mountain building at convergent plate boundaries. Therefore, the strength and deformation behavior of these rocks will strongly influence the structures that develop in mountains, which are responsible for the accumulation of natural resources. The data generated through this study will be used by theoretical modelers and field geologists to determine how and where resources accumulate. Carbonate rocks are also carried to significant depths in the earth?s interior within subduction zones, and their strengths and deformation behavior will thus exert a strong influence on processes such as subduction and mantle convection. Data on the deformation behavior of these rocks will enable theoretical modelers to more accurately predict the dynamics of these long-term geologic processes, including a better understanding of the dynamics of deep earthquakes.

该奖项是根据2009年的《美国回收与再投资法》（公法111-5）进行资助的。在大陆边缘存放的shallow海洋碳酸盐岩石在收敛板边界处遭受强烈的变形，并且越来越多的证据表明，这些碳酸盐岩石在俯冲芯片中被大量的大量矿物质的矿石装饰。 与由硅酸盐矿物质组成的岩石相比，由碳酸盐组成的岩石较弱，因此它们的变形对大陆碰撞导致的山带发展的结构产生了强烈的影响，并且它们也可能影响俯冲过程中地幔的变形。碳酸盐岩主要由矿物方解石，白云岩和镁石组成。这些矿物质具有相似的晶体结构，但在组成和机械上是不同的。尽管方解石的流变学已经很好地确定，但白云石的流变学受到实验的限制，几乎一无所知，关于镁铁矿的流变学，这比ictite岩的深度稳定，而不是方解石或白云岩。 为了准确地模拟俯冲和山地建筑过程中地壳和地幔中的变形过程，需要精炼白云石的流变学，确定镁铁矿的流变学，然后与方解石的流变学进行比较。该项目将使用实验和观察方法来实现以下方面：（1）通过在三轴岩石变形设备中确定白云岩的脱位的流变学，以确定公元石中这种变形机制的温度和应变率依赖性； （2）通过实验，在三轴岩石变形设备中确定镁铁矿的机械性能，在各种压力，温度和应变速率上，以确定温度和应变速率的范围，以使不同的变形机制运行； （3）研究在实验缩短和剪切的白云岩中形成的微观结构和织物； （4）将实验变形过程中形成的微观结构和织物与在天然白云岩剪切区中观察到的微观结构和织物进行比较，以提供基础，以将实验室确定的流变型应用于自然。这项研究将通过变形实验和分析在自然，强度和变形的岩石变形，强度和变形过程中的岩石变形过程中，这些研究的强度和变形过程。含碳酸盐的岩石构成了在收敛板边界上山区建筑期间变形的很大一部分。因此，这些岩石的强度和变形行为将强烈影响山区发展的结构，这些结构负责自然资源的积累。通过这项研究生成的数据将由理论建模者和现场地质学家使用来确定资源如何和何处积累。碳酸盐岩石在俯冲带中的内部内部也将碳酸盐岩带到显着的深度，因此它们的强度和变形行为将对俯冲和地幔对流等过程产生强大的影响。这些岩石的变形行为的数据将使理论建模者能够更准确地预测这些长期地质过程的动态，包括更好地理解深层地震的动态。