An Apatite/Zircon (U-th)/He Thermochronometric Study of the Rapid Tectonic Denudation of an Oblique Crustal Section-Southern Sierra Nevada, California

加利福尼亚州内华达山脉南部斜地壳部分快速构造剥蚀的磷灰石/锆石 (U-th)/He 测温研究

• 批准号: 0230383
• 负责人: Jason Saleeby
• 金额: $ 25.47万
• 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: 2002
• 资助国家: 美国
• 起止时间: 2002-12-01 至 2005-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0230383&HistoricalAwards=false
• 关键词: Apatite; Zircon; th; He; Thermochronometric

PROJECT SUMMARYThe PI's propose to produce a series of (U-The)/He apatite and zircon thermochronologic profiles in the southernmost Sierra Nevada region as a test of the very rapid tectonic denudation of the Sierran batholithic rocks by low-angle detachment faulting in latest Cretaceous-early Paleogene time. This phase of denudation exposed an oblique crustal section through the southernmost Sierra Nevada batholith to a paleodepth of ~35 km. Apatite He studies in the greater Sierra Nevada region to the north have revealed the persistence of a high standing orogenic plateau with long wavelength-high relief fluvial dominated topography during the same time interval. In marked contrast the deepest level exposures of the batholith to the south had subsided to marine conditions by early Eocene time in conjunction with tectonic denudation. These profound along strike variations in the paleogeomorphology of the Sierran magmatic arc can be linked to the tectonic removal of the sub-batholithic mantle lithosphere beneath the southernmost Sierra-northern Mojave Desert region by a shallow flat-slab segment of the subductingoceanic plate, and the related tectonic underplating of Franciscan trench-affinitymetamorphic assemblages. The PI's have identified an array of known and apparent high-level batholithic detachment sheets along the southernmost Sierra and northern MojaveDesert region that appear to represent part of the upper crustal rocks that were displacedby the detachment system. They have also identified modern topographic anomalies andanomalous structural-textural overprints in the basement rocks of the southern Sierraregion which correspond to the onset of steep gradients in batholith emplacementbarometry and its implicit depth of denudation. They interpret these areas to represent theremnants of footwall complexes proximal to the breakaway zones where the northernmost detachment sheets calved off the edge of the orogenic plateau. Verticalapatite and zircon thermochronologic profiles are proposed across these zones as a test ofvery rapid cooling and tectonic denudation. These profiles will be extended southwardalong constant elevation profiles to the deepest exposed levels of the batholith in order tofurther test for regional rapid cooling, and to test for a possible southward migration inprogressively deeper levels of denudation with time. The broader goals are to relate thepaleogeomorphic evolution of the southern Sierra region to lithosphere-scale tectonicsand dynamics, and to relate these findings to the globally important problem of theupward migration and surface exposure of deep crystalline basement rock as related touplift, erosion, tectonic denudation, and the evolution of lower crust and upper mantle.The proposed research program runs for a period of three years and includes a vigorousprogram of sample collecting, mineral separation, geochemical analysis, and thesynthesis of the new data with existing geological and geochemical data sets. The projectwill entail partial efforts of the joint PI's and their technical staff, and constitute a majorcomponent of a Caltech Ph.D. Dissertation.

Project总结了PI的建议，建议在内华达州最南端的内华达州地区生产一系列（u-The）/He Apatite和锆石热量体剖面，以测试塞兰浴石像岩石的非常快速的构造剥离，这是通过低角度分离造成的，在最新的酿酒师 - 古凝胶时间中，低角度脱离。这种剥夺的阶段通过内华达州山利岩最南端的斜面露出了一个倾斜的地壳截面，到达了约35公里的古兴趣。他在北部内华达州大山脉地区学习的磷灰石揭示了高造型平台的持续存在，并在同一时间间隔内，较长的波长浮雕河流河流主导地形。与形成鲜明对比的对比度最深的水平暴露于南部的最深层次的暴露与始新世早期时期与构造剥夺的早期时期。这些深刻的沿着山脉岩浆弧的古形态学变化的变化可以与在最南端的米哈韦山脉沙漠地区下面的层层岩层岩石层下方的构造去除，这是由浅层平面板块的浅平板层的浅层平面板块的组成板和相关的结构板的构造构成了夫妻的范围。 PI已经确定了一系列已知且明显的高水平沐浴式支队沿着最南端的塞拉山脉和北部莫哈维德塞特地区，它们似乎代表了脱离系统流离失所的上层岩石岩石的一部分。他们还鉴定了现代地形异常和塞拉雷奇南部地下岩石中的杂结构质地覆盖，这对应于Batholith EmplacementBarometry及其隐式深度的陡峭梯度的发作。他们解释了这些区域，以代表距离距离区域近距离区域的训练区的训练者，那里最北端的支队从造山机高原的边缘平静了下来。在这些区域中提出了垂直磷灰石和锆石热量剖面，作为快速冷却和构造剥离的测试。这些轮廓将被扩展到向南的恒定高程曲线到最深的浴载水平，以便进行区域快速冷却，并测试可能随着时间的推移而向南迁移的迁移，并随着时间的推移而进行。更广泛的目标是将塞拉山脉南部地区的销售地球化学演变与岩石圈尺度构造和动态联系，并将这些发现与全球重要的迁移和深层晶体地下岩石表面暴露的问题联系在一起，与相关的touplift，touplift，ersectornic neprift，totectonic neplift，topift，topectics宣布的时期和近期的进化计划。并包括样本收集，矿物分离，地球化学分析以及具有现有地质和地球化学数据集的新数据的分析。该项目将需要联合PI及其技术人员的部分努力，构成了Caltech博士学位的重要组成部分。论文。