Collaborative Research: Determining Mantle Rheology from Field and Microstructural Observations of Naturally-deformed Peridotites

合作研究：通过自然变形橄榄岩的现场和微观结构观察确定地幔流变性

• 批准号: 0409567
• 负责人: Julie Newman
• 金额: --
• 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: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409567&HistoricalAwards=false
• 关键词: Collaborative; Research; Determining; Mantle; Rheology

A crucial and unsolved question in global earth science is the relative strength of the different lithospheric layers that make up the tectonic plates. Rheology, the term used to describe material behavior, quantifies the relation between the observed deformation (strain) and the applied forces (stress). The principal investigators of this grant combine quantitative, field-based geologic studies with data from experimental rock deformation studies to constrain the rheology of naturally-deformed mantle rocks. The fieldwork provides analysis of deformation at geologic strain-rates, spatial scales, and levels of compositional heterogeneity, while laboratory studies provide data from controlled deformation experiments at known stresses and strain-rates for monophase materials. The lithospheric (uppermost) mantle is the focus of this study for three reasons. First, mantle rocks have a relatively simple mineralogy (typically only three minerals, volumetrically dominated by the mineral olivine). Second, a large amount of experimental data has been conducted on olivine, allowing calibration of the field studies. Third, because of the high strength of olivine in experimental studies, many current models assume that the lithospheric mantle dominates the material behavior of the tectonic plates. Two extremely well-exposed sections of upper mantle rocks, the Dun Mountain ophiolite body (Red Hills section) in New Zealand and the Twin Sisters dunite in Washington State, USA are investigated in this study. The two field areas provide different, but complimentary, constraints on mantle rheology. The Twin Sisters dunite is an ideal field locality to: 1) Quantify deformation in a mantle section, by using geological markers known as dikes; 2) Observe spatial variations in mantle deformation; and 3) Determine the effect of the 2nd mineral phase (orthopyroxene) on the bulk rheology of natural peridotites. The Red Hills section of the Dun Mountain ophiolite, New Zealand, allows the PIs to investigate two additional aspects of mantle deformation: 1) The rheological implications of large-scale structures (e.g., folds) present in naturally deformed mantle bodies; and 2) Why localization, as inferred from ductilely sheared markers, takes place in the mantle. From these data sets, the bulk rheology of lithospheric mantle will be constrained. The grant supports a graduate student and multiple undergraduate students at two universities. The funding forms the basis for international cooperation with a New Zealand university, allowing students to visit both universities.

在全球地球科学中，一个至关重要的问题是构成构造板的不同岩石圈层的相对强度。 流变学是用于描述材料行为的术语，量化了观察到的变形（应变）和施加力（应力）之间的关系。 该赠款的主要研究人员将基于现场的地质研究与实验岩石变形研究的数据结合在一起，以限制自然变形的地幔岩石的流变。 现场工作提供了地质应变率，空间尺度和组成异质性水平的变形的分析，而实验室研究则提供了来自已知应力和单相材料应变率的受控变形实验的数据。 岩石圈（最高）地幔是本研究的重点，原因有三个。 首先，地幔岩具有相对简单的矿物学（通常只有三个矿物质，由矿物橄榄石占主导地位）。 其次，已经在橄榄石上进行了大量实验数据，从而允许对现场研究进行校准。 第三，由于实验研究中橄榄石的强度很高，许多当前模型假设岩石圈地幔主导了构造板的材料行为。在这项研究中，研究了两个极为盛大的地幔岩石，即新西兰的Dun Mountain山地泥石体（红山区）和美国华盛顿州华盛顿州的Twin Sisters Dunite。 这两个田间领域对地幔流变学提供了不同但免费的限制。 双子姐妹Dunite是：1）通过使用称为二克的地质标记来量化地幔截面中的变形； 2）观察地幔变形的空间变化； 3）确定第二个矿物相（邻苯二烯）对天然橄榄岩的大体流变学的影响。 新西兰的邓山蛇绿岩的红山段允许PIS研究地幔变形的两个其他方面：1）在自然变形的地幔体中存在的大规模结构（例如褶皱）的流变学意义； 2）为什么通过导管剪切标记推断出的定位发生在地幔中。 从这些数据集中，将限制岩石圈地幔的大量流变性。该赠款支持两所大学的研究生和多名本科生。 资金构成了与新西兰大学国际合作的基础，使学生可以参观两所大学。