Collaborative Research: Growth of oceanic lower crust: an integrated high-precision geochronologic and trace-element approach

合作研究：海洋下地壳的生长：高精度地质年代学和微量元素综合方法

• 批准号: 0960892
• 负责人: Samuel Bowring
• 金额: $ 18.66万
• 依托单位: Massachusetts Institute of Technology
• 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: 2010-08-15 至 2013-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0960892&HistoricalAwards=false
• 关键词: Collaborative; Research; Growth; oceanic; lower

Although oceanic lithosphere covers more than 60% of the earth's surface, models for its formation at mid-ocean ridges have been hampered by a lack of geochronological constraints on intrusive rocks that underlie volcanic rocks erupted on the seafloor. Recent advances in the U-Pb dating of zircons, refractory minerals that are found in gabbors and other intrusive rocks in ocean crust, now allow dates of intrusions to be measured. This research pursues this objective using a combined secondary ion mass spectrometry (SIMS) and thermal ionization mass spectrometry (TIMS) approach. Samples of intrusive gabbros from Hole 735B on the Southwest Indian Ridge from the Ocean Drilling Program will be analyzed. SIMS, which is a high resolution but large uncertainty technique that can measure geochemical differences on a micron scale, will be used to determine the trace element composition of zoning in zircons. High precision isotope dilution TIMS dating of the zircons will be used to determine the magmatic evolution of the samples. Uncertainties in the ages measured are expected to be 12,000 years or less. This precision will provide unprecedented insight into how long it takes for ocean crust to grow at slow spreading ridges. Broader impacts of the work include postdoctoral training and mentoring. It also fosters inter-institutional collaboration and will support two PIs, one of whom is from a gender under-represented in the sciences, from an EPSCoR state. Outreach to high schools in the Cambridge MA area will be carried out and educational materials for them will be created on geochronology. Results of the project will be archived in NSF-funded publicly accessible databases.

尽管海洋岩石圈覆盖了地球表面的60%以上，但由于缺乏对海底火山岩下的侵入岩的地质年代学限制，海洋中脊岩石圈形成的模型一直受到阻碍。锆石U-Pb测年的最新进展，发现在辉长岩和其他侵入岩在海洋地壳中的耐火矿物，现在允许入侵的日期进行测量。 本研究采用二次离子质谱（西姆斯）和热电离质谱（TIMS）相结合的方法来实现这一目标。 将对大洋钻探计划中西南印度洋脊735 B孔的侵入辉长岩样品进行分析。 西姆斯是一种高分辨率但不确定性大的技术，可以测量微米尺度上的地球化学差异，将用于确定锆石分带的微量元素组成。 高精度同位素稀释TIMS测年的锆石将被用来确定岩浆演化的样品。 预计测得的年龄将是12 000年或更短，这一精确度将为了解大洋地壳在缓慢扩张的海脊上生长所需的时间提供前所未有的见解。 这项工作的更广泛影响包括博士后培训和指导。 它还促进机构间合作，并将支持两名PI，其中一名来自EPSCoR州的科学界代表性不足的性别。将在马萨诸塞州剑桥地区的中学开展外联活动，并将为这些中学编写关于地质年代学的教材。该项目的结果将存档在国家科学基金会资助的公共访问数据库中。