Oxygen and Hydrogen Isotope Studies of Igneous Rocks and Associated Hydrothermal Alteration

火成岩及相关热液蚀变的氧和氢同位素研究

• 批准号: 9725811
• 负责人: Hugh Taylor
• 金额: $ 27.77万
• 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: 1997
• 资助国家: 美国
• 起止时间: 1997-12-01 至 2001-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9725811&HistoricalAwards=false
• 关键词: Oxygen; Hydrogen; Isotope; Studies; Igneous

9725811 Taylor This proposal is part of a continuing effort to understand water-rock interactions in the Earth's crust and the mechanisms of 18O/16O exchange between minerals and fluids. Recently, the PI and coworkers have discovered a new type of 18O/16O signature was discovered in the welded ash-flow tuffs, namely the coexistence of 18O-depleted volcanic glass with feldspar and quartz phenocrysts that have preserved their primary magmatic 18O/16O values. This implied that large amounts of low-18O meteoric groundwater had tocirculate through the tuff at high temperatures (500(-650(C), on a short enough time scale ((25 years) that the feldspar (18O values were undisturbed, suggesting an analog to the spectacular fumarolic activity that occurred in 1912-1924 at the Valley of Ten Thousand Smokes, Mt. Katmai National Park, Alaska. The present proposal aims to test these concepts on an outflow-tuff sheet; such a study would be more directly analogous to the activity seen on the surface at Katmai. The 760,000 year old, 200-m thick Bishop Tuff in California appears to be an ideal field area, because of good zones of shallow-dipping columnar joints. The amounts of magmatic H2O in these systems and the mechanisms of hydrologic recharge for these fossil fumaroles will be investigated by making detailed 18O/16O studies, as well as making a regional 18O/16O map and comparing it to what is known about the pre-eruptive surface topography of the BishopTuff. This will allow a test as to whether these fossil fumaroles were fed by groundwater flow from the newly-formed Long Valley Lake down through the upper zone of permeable, partially welded ash-flow tuff. The role of columnar jointing in fumarolic meteoric-hydrothermal circulation will also be studied.

9725811泰勒这个提议是持续努力的一部分，以了解地壳中的水-岩石相互作用以及矿物和流体之间的18 O/16 O交换机制。 最近，PI及其同事在熔结灰流凝灰岩中发现了一种新的18 O/16 O特征，即贫18 O火山玻璃与长石和石英斑晶共存，这些斑晶保留了原始岩浆18 O/16 O值。 这意味着大量的低18 O的大气地下水必须在高温（500（-650（C）），在足够短的时间尺度（25年），长石（18 O值未受干扰，循环通过凝灰岩，这表明类似于1912-1924年发生在万烟谷，Mt.卡特迈国家公园，阿拉斯加。 目前的建议旨在测试这些概念上流出凝灰岩席;这样的研究将更直接类似于在表面上看到的活动在卡特迈。 加州的76万年历史、200米厚的Bishop凝灰岩似乎是一个理想的野外区域，因为有良好的浅倾柱状节理带。 这些系统中的岩浆H2O的量和水文补给机制，为这些化石微洞将进行详细的18 O/16 O的研究，以及制作区域18 O/16 O地图，并将其与已知的火山喷发前的表面地形的主教凝灰岩进行比较。 这将允许测试这些化石凝灰岩是否是由地下水流从新形成的长谷湖向下通过渗透性的，部分焊接的灰流凝灰岩的上部区域。 还将研究柱状节理在大气-热液循环中的作用。