MARGINS: Controls on Magma Generation at Incipient Spreading Centers

边缘：对早期扩散中心岩浆生成的控制

• 批准号: 0948162
• 负责人: Axel Schmitt
• 金额: $ 2.49万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-02-01 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0948162&HistoricalAwards=false
• 关键词: MARGINS; Controls; Magma; Generation; Incipient

Intellectual merit. This study aims to identify the controlling parameters for magmatic diversity in two young rift basins (Salton Sea and Cerro Prieto) within the on-land extension of the Gulf of California. Despite similarities in basin structure and tectonic setting, magmatism in both locations differs strongly. Salton Sea surface and subsurface magmatic rocks are bimodal, whereas intermediate compositions predominate at Cerro Prieto. Because both magmatic systems are associated with economically important geothermal resources, dense three-dimensional sampling exists through geothermal well penetration. Drill cuttings from geothermal wells are invariably contaminated and rocks were exposed to intense alteration at high ambient temperatures. Thus, high spatial resolution uranium series geochronology coupled with oxygen isotopic analysis of zircon by secondary ion mass spectrometry (SIMS) has the strongest prospects for extracting reliable information on the temporal and spatial patterns of magmatic variability. Results from Cerro Prieto will complement existing data for the Salton Sea that indicate episodic rhyolite generation through remelting of hydrothermally altered basaltic crust since at least 400 ka. The integration of these results will provide insights into the changes in lithospheric structure during continental rupture, the composition and thermal state of the lower crust in rift basins, and the maturation of newly accreted crust during incipient ocean spreading.Broader impacts. This research impacts on strategies for renewable energy exploration, and fosters ties between academics and the geothermal industry. Users of the UCLA National Ion Microprobe facility will benefit from SIMS method development tailored to low-yield samples and in-situ analysis. This project provides opportunities for undergraduate research experience.

智力上的优点。本研究的目的是确定控制参数的岩浆多样性在两个年轻的裂谷盆地（索尔顿海和塞罗普列托）内的加州湾的陆地延伸。尽管在盆地结构和构造环境的相似性，岩浆在这两个位置有很大的不同。索尔顿海表面和地下岩浆岩是双峰，而中间成分占主导地位的塞罗普列托。由于这两个岩浆系统都与经济上重要的地热资源有关，因此通过地热井渗透进行密集的三维采样。地热威尔斯井的钻屑总是受到污染，岩石在高环境温度下暴露于强烈的蚀变。因此，高空间分辨率的铀系地质年代学加上二次离子质谱法（西姆斯）的锆石氧同位素分析具有最强的前景，提取可靠的信息的时间和空间格局的岩浆变异。从塞罗普列托的结果将补充现有的数据，索尔顿海表明，通过重熔热液蚀变玄武质地壳，因为至少400万年的幕式流纹岩代。这些结果的整合将有助于深入了解大陆断裂期间岩石圈结构的变化、裂谷盆地下地壳的组成和热状态以及海洋扩张初期新增生地壳的成熟。这项研究对可再生能源勘探战略产生了影响，并促进了学术界和地热行业之间的联系。加州大学洛杉矶分校国家离子微探针设施的用户将受益于西姆斯方法的发展，适合低产量的样品和原位分析。该项目为本科生提供了研究经验的机会。