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.

南部的内华达州山脉提供了一个倾斜的部分， 来自地表的年轻岩基生成的硅铝质地壳（火山） 水平到深（粒状）水平。 区域制图和Pb/U 锆石地质年代学揭示了通过这种结构的连续性 ~100 Ma岩浆-变质组合的地壳剖面， 使其成为地球上最年轻的 世界上的部分。 成分和结构模式 在本节中结合地球物理和 火山岩捕虏体数据对硅铝质地壳提出了重要问题 下陆壳的成因和性质。 一些 建议的研究的具体目标包括（1）同位素， 岩石化学和岩相学特征 主要的地幔衍生的火成岩套，被添加到地壳， ~100 Ma，并考虑其在形成一个 麻粒岩下地壳;（2）地壳熔融现象研究 这套地幔火成岩套施加在各种预先存在的 地壳物质，已知的特点，大部分的前， （3）基于区域地图关系的岩基框架; 年轻幔源混合模型的构造 组分和先存地壳物质及其应用 这些模型的大规模问题的岩基 岩石成因;（4）应用适当的温压计， 作为地壳剖面模型改进的深层暴露 并对高峰期的物理条件进行限制 变质作用和地壳熔融作用; 对选定的韧性剪切带进行年代学分析， 似乎与岩基密切相关的断层系统 侵位和火山喷发 大规模的目标， 研究旨在对主要部件和材料运输进行建模 有助于南方生产的模式 Sierra sialic地壳柱，并考虑 这种现象对于更广泛的大陆结构问题， 进化