Development of Gneissic Banding and its Significance for Rheological Stratification of the Lithosphere

片麻岩带的发育及其对岩石圈流变分层的意义

• 批准号: 9725661
• 负责人: Virginia Sisson
• 金额: $ 8.01万
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-02-15 至 2003-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9725661&HistoricalAwards=false
• 关键词: Development; Gneissic; Banding; its; Significance

9725661 Sisson This project will address the metamorphic and structural processes associated with the development of gneissic banding in the migmatitic core of a low-pressure/high-temperature metamorphic belt in the eastern Chugach Mountains, southern Alaska. Two processes which may be responsible for formation of the gneissic banding are: (1) injection of felsic melts or (2) segregation by diffusive mass-transfer. These mechanisms are not mutually exclusive and may occur simultaneously. These two mechanisms predict very different crustal rheologies for the ductile regions in the middle and lower crust. This difference in rheological properties will influence large scale mechanics of the lithosphere. This research will attempt to distinguish between the two mechanisms for development of gneissic banding by looking at textural and compositional differences throughout the transition zone from schistose to gneissic fabrics. The PI will investigate several regions where the width of the metamorphic belt changes from 15-25 km. The proposed work includes detailed flied work to elucidate kinematics of the gneissic transition zone, detailed petrographic studies of both textural and compositional difference, and high resolution computed x-ray tomography.

9725661 Sisson 该项目将研究与阿拉斯加南部楚加奇山脉东部低压/高温变质带混合岩带发展相关的变质和构造过程。可能导致片麻岩带形成的两个过程是：（1）长英质熔体的注入或（2）通过扩散传质进行偏析。这些机制并不相互排斥，并且可以同时发生。这两种机制预测中地壳和下地壳的韧性区域的地壳流变性非常不同。这种流变特性的差异将影响岩石圈的大尺度力学。这项研究将试图通过观察从片岩到片麻岩织物的整个过渡带的结构和成分差异来区分片麻岩带发展的两种机制。 PI 将调查几个变质带宽度在 15 至 25 公里之间变化的地区。拟议的工作包括阐明片麻岩过渡带运动学的详细飞行工作、结构和成分差异的详细岩相研究以及高分辨率计算机 X 射线断层扫描。