Seismic Properties of Shear Zones in the Lower Continental Crust

下陆壳剪切带的地震特性

• 批准号: 8720703
• 负责人: David Fountain
• 金额: $ 10.35万
• 依托单位: University of Wyoming
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-07-01 至 1990-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8720703&HistoricalAwards=false
• 关键词: Seismic; Properties; Shear; Zones; Lower

Mylonite zones exposed within the granulite facies terrains of the Ivrea-Verbano zone, northern Italy, and the Bergen Arc, western Norway, provide examples of fault zones in the lower continental crust of extensional and compressional regimes, respectively. Within the Ivrea zone, the shear zones occur as mylonites of the Pogallo fault zone and as high temperature shear zones in the granulite domain of Valle d'Ossola. Deformed ultramafic rocks are also important constituents of deep structural levels of the Ivrea zone. Mylonites in the Bergen Arc are superimposed on an anorthositic complex and are characterized by an eclogite facies mineralogy. The research investigated the seismic properties of rocks from the these zones in order to evaluate the hypothesis that mylonite zones cause deep crustal reflections. The main phases of the work are 1) a sampling program in both regions; 2) investigation of preferred mineral orientations in the mylonitic rocks; 3) thin section and geochemical study of the composition of samples; 4) determination of the elastic constant tensor by measurement of P- and S-wave velocities at confining pressures up to 600 MPa; 4) construction of hypothetical velocity profiles through deformed and undeformed sequences.

在意大利北部伊维德里亚 - 维巴诺地区的颗粒岩相中暴露于颗粒状区域和挪威西部卑尔根弧的地形中，分别提供了延伸和压缩状态的下层大陆地壳中的断层区域的例子。 在伊维rea区域内，剪切带作为波加洛断层区的肌lon虫和瓦尔·奥索拉颗粒状结构域中的高温剪切区域出现。 变形的超镁铁质岩石也是图部区域深层结构水平的重要组成部分。 卑尔根弧中的甲状腺藻层叠加在垂线络合物上，其特征是叶绿石相矿物学。 该研究调查了这些区域中岩石的地震特性，以评估肌隆区引起深层地壳反射的假设。 工作的主要阶段是1）两个区域的抽样程序； 2）调查麦芽糖岩石中首选的矿物方向； 3）样品组成的薄片和地球化学研究； 4）通过测量P-和S波速度在高达600 MPa的限值下测量弹性恒定张量； 4）通过变形和未变形的序列构建假设速度曲线。