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.

内华达山脉南部提供了一个倾斜的剖面，穿过年轻的岩基生成的唾液质地壳，从表面（火山）水平到深层（粒岩）水平。 区域测绘和 Pb/U 锆石年代学揭示了该地壳剖面的结构连续性，其火成变质岩组合约为 100 Ma，使其成为世界上最年轻的暴露大陆地壳剖面之一。 本节中观察到的成分和结构模式与地球物理和火山捕虏体数据相结合，对唾液质地壳成因和下大陆地​​壳的性质提出了重要问题。 拟议研究的一些具体目标包括（1）对在约 100 Ma 时添加到地壳的明显主要地幔衍生火成岩套件的同位素、石油化学和岩石学特征，并考虑其在粒状下地壳形成中的作用； (2) 研究该地幔火成岩套对各种预先存在的地壳物质施加的地壳熔融现象，这些物质已知可根据区域地图关系表征大部分前岩岩框架； （3）年轻地幔源成分与先存地壳物质混合模型的构建及其在大规模岩基成岩问题中的应用； (4) 将适当的温压计应用于深部暴露，作为地壳剖面模型的细化，并对峰值变质作用和地壳熔融的物理条件施加约束； (5) 对选定的韧性剪切带和断层系统进行结构和地质年代学分析，这些剪切带和断层系统似乎与岩基就位和火山喷发密切相关。 这项研究的大范围目标是对有助于南塞拉唾液酸地壳柱产生的主要成分和物质运输模式进行建模，并考虑这种现象对更广泛的大陆结构和演化问题的影响。