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

TaylorEAR-0106696我们正试图证明，使用力场模拟和红外和拉曼光谱振动频率的测量相结合的方法，可以准确地计算简单含铁络合物和铁金属之间的平衡铁同位素分馏。这一点很重要，因为它在解释其他工作人员对天然材料以及水溶液中的物种和离子交换树脂结合的物种之间的高精度铁同位素测量的令人兴奋的新结果方面具有相关性。我们还完成了内华达州和犹他州花岗岩的氧和放射性同位素研究，初步结果表明，在侏罗纪、白垩纪和新生代的三个岩浆作用阶段中，不同的源岩都有系统的参与。第三个目标是完成我们对在焊接的火山灰流凝灰岩上部发现的斑晶和基质中显著的氧同位素模式的理解，例如我们对毕晓普凝灰岩的研究(Holt和Taylor，1998)，在那里我们表明，低18O带与在凝灰岩最上层70-80米暴露的绘制的化石气相结构一一对应。我们正在研究阿拉斯加州万烟谷(VTTS)暴露的1912年火山灰流表的上部15米(根据直接观察，火山孔在喷发后大约15年终止)，从而将对VTTS中最近活跃的气孔进行的科学观察与毕晓普凝灰岩中的化石气孔联系起来。

TaylorEAR-0106696We are attempting to show that equilibrium iron-isotope fractionations among simple iron-bearing complexes and Fe metal can be accurately calculated using a combination of force-field modeling together with available measurements of vibrational frequencies from infrared and Raman spectroscopy. This is important because of its pertinence in interpreting the exciting new results by other workers of high-precision iron isotope measurements on natural materials and between species in aqueous solution and those bound to ion-exchange resins. We are also finishing up an oxygen and radiogenic isotope study of granitic plutons in Nevada and Utah for which preliminary results have shown a systematic involvement of different source rocks during each of three stages of magmatism in the Jurassic, Cretaceous, and Cenozoic. A third goal is to complete our understanding of the remarkable oxygen isotope patterns in phenocrysts and groundmass found in the upper parts of welded ash-flow tuffs, exemplified in our studies of the Bishop Tuff (Holt and Taylor, 1998), where we showed that the low-18O zones exhibited a one-to-one correspondence with mapped fossil fumarolic structures exposed in the uppermost 70-80 meters of the tuff We are in the process of examining the exposed upper 15 meters of the 1912 ash-flow sheet in the Valley of Ten Thousand Smokes (VTTS), Alaska (where the fumaroles are known from direct observation to have terminated about 15 years after eruption), thereby linking the scientific observations made on recently active fumaroles in the VTTS with the fossil fumaroles in the Bishop Tuff.