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

9725811泰勒这项建议是了解地壳中水-岩石相互作用以及矿物和流体之间18O/16O交换机制的持续努力的一部分。最近，Pi和他的同事们在焊接的火山灰流凝灰岩中发现了一种新的18O/16O特征，即18O亏损的火山玻璃与保存了其原始岩浆18O/16O值的长石和石英斑晶共存。这意味着，大量低18O的大气地下水必须在高温(500(-650摄氏度)，在足够短的时间尺度(25年)，长石(18O)值没有受到干扰的情况下)才能在凝灰岩中循环，这表明类似于1912-1924年在芒特山万烟谷发生的壮观的烟雾化活动。阿拉斯加州卡特迈国家公园。目前的建议旨在在流出凝灰岩岩层上测试这些概念；这样的研究将更直接地类似于在Katmai表面看到的活动。加利福尼亚州有76万年历史、200米厚的毕晓普凝灰岩似乎是一个理想的野外区域，因为有很好的浅倾斜柱状节理地带。通过详细的~(18)O/~(16)O研究，绘制区域~(18)O/~(16)O图，并与已知的毕肖普凝灰岩喷发前地表地貌相比较，将研究这些系统中的岩浆水含量和这些化石富马罗尔的水文补给机制。这将测试这些化石气孔是否由地下水从新形成的龙谷湖向下流经可渗透的、部分焊接的火山灰流凝灰岩的上层。柱状节理在富马林大气-热液循环中的作用也将被研究。

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.