Petrogenetic and Tectonic Studies in an Exposed Cross- Section of Young (approx. 100 Ma) Continental Crust - Southern Sierra Nevada, California

年轻（约 100 Ma）大陆地壳裸露横截面的岩石成因和构造研究 - 加利福尼亚州内华达山脉南部

• 批准号: 8904063
• 负责人: Jason Saleeby
• 金额: $ 16.49万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-07-01 至 1991-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8904063&HistoricalAwards=false
• 关键词: Petrogenetic; Tectonic; Studies; Exposed; Cross

The southern Sierra Nevada offers an oblique section through young batholith-generated sialic crust from surface (volcanic) levels to deep (granulitic) levels. Regional mapping and Pb/U zircon geochronology reveal structural continuity through this crustal section for igneous-metamorphic assemblages of ~100 Ma, making it one of the youngest exposed continental crustal sections in the world. Compositional and structural patterns observed in this section in conjunction with geophysical and volcanic xenolith data pose important problems on sialic crustal genesis and the nature of lower continental crust. Some specific aims of the proposed research include (1) isotopic, petrochemical and petrographic characterization of an apparent major mantle-derived igneous suite that was added to the crust at ~100 Ma, and consideration of its role in the formation of a granulitic lower crust; (2) study of crustal melting phenomena imposed by this mantle igneous suite on a variety of pre-existing crustal materials that are known to characterize much of the pre- batholithic framework based on regional map relations; (3) con- struction of mixing models between the young mantle-derived component and pre-existing crustal materials and the application of these models to large-scale problems of batholith petrogenesis; (4) application of appropriate thermobarometers to deep-level exposures as a refinement of the crustal section model and for placing constraints on the physical conditions of peak metamorphism and crustal melting; and (5) structural and geochronological analysis of selected ductile shear zones and fault systems which appear to be intimately related to batholith emplacement and volcanic venting. Large-scale goals of this research are to model the major components and material transport patterns that contributed to the production of the southern Sierra sialic crustal column and to consider the implications of such phenomena for broader issues of continent structure and evolution.

内华达山脉南部通过年轻的Batholith生成的唾液壳从表面（火山）水平到深（颗粒状）水平提供倾斜的部分。 区域映射和PB/U锆石的年代学通过此构架截面揭示了〜100 Ma的火成岩构成组合的结构连续性，使其成为世界上最年轻的大陆甲壳截面之一。 在本节中观察到的组成和结构模式以及地球物理和火山异种石的数据在唾液地壳起源和下大陆壳的性质上提出了重要问题。 拟议的研究的一些具体目的包括（1）同位素，石化和岩石学表征明显的主要地幔衍生的火成岩套件，该套件被添加到约100 mA的地壳中，并考虑了其在颗粒状下皮形成中的作用； （2）研究该地幔火成岩套件对各种既有的地壳材料施加的地壳融化现象的研究，这些套件已知，这些材料是基于区域地图关系的许多预先沐浴石的框架的表征； （3）在年轻地幔衍生的成分和预先存在的地壳材料之间结合混合模型，并将这些模型应用于Batholith Pitrogenogeny的大规模问题； （4）将适当的热压计应用于深层暴露，作为地壳截面模型的改进，并将约束对峰值变质和地壳熔化的物理条件放置； （5）似乎与沐浴石的隔离和火山通风密切相关的选定延性剪切区和断层系统的结构和年代学分析。 这项研究的大规模目标是建模有助于产生南部塞拉西亚缝线柱的主要组成部分和材料运输模式，并考虑这种现象对大陆结构和进化的更广泛问题的含义。