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

火成岩及相关热液变质作用的氧和氢同位素研究

• 批准号: 8816413
• 负责人: Hugh Taylor
• 金额: $ 31.7万
• 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: 1989
• 资助国家: 美国
• 起止时间: 1989-01-01 至 1990-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8816413&HistoricalAwards=false
• 关键词: Oxygen; Hydrogen; Isotope; Studies; Igneous

We have developed equations for the kinetics of 18O/16O exchange between minerals and hydrothermal fluids that can be used as an "oxygen isotope clock". The 18 values of coexisting minerals represent isochrons that can measure the "life-times" and water/rock ratios of fossil hydrothermal systems without doing lengthy computer simulations. We wish to apply these concepts to various rift-zone environments, where enhanced fracture permeability allows deep circulation of surface waters. Shallow, short-lived systems have been well studied, but deeper, longer-lived, and hotter systems transitional to crustal melting are poorly understood. We intend to study such "hydrothermal- anatetic" magmas in: (1) Hercynian-age Metamorphic Systems in Europe, including the classic area of migmatites in the Black Forest, West Germany. (2) Volcanism in Rift-Zone Environments, notably in Iceland, the Great Basin in Nevada, and the Snake River Plain, Idaho. (3) Spreading Centers in Arabia, including a 22 Ma subaerial hydrothermal system (opening of the Red Sea), and a 95 Ma submarine system (Oman ophiolite complex). Also, we need to improve our understanding of the 18O/16O geochemistry of the continental crust and upper mantle, notably in: (4) Detrital Sedimentary Rocks of different types and metamorphic grades to better define the geochemical cycles of 18O/16O and D/H during digeneses, metamorphism and melting. (5) The Ivrea Zone, Northern Italy, perhaps the best available section through the lowermost continental crust. (6) Quaternary- Age Igneous Rocks of Italy. (7) Eclogite and Periodotite Xenoliths to better define fluid-rock interactions in the upper mantle, and to try to identify ancient subducted oceanic crust in these sub-continental lithosphere.

我们建立了矿物和热液流体之间~(18)O/~(16)O交换的动力学方程，可用作“氧同位素钟”。共存矿物的18个值代表等时线，可以测量化石热液系统的“寿命”和水/岩比，而不需要进行冗长的计算机模拟。我们希望将这些概念应用于各种裂谷区环境，在这些环境中，增强的裂缝渗透率允许地表水的深层循环。浅层、短寿命的系统已经得到了很好的研究，但对过渡到地壳融化的更深、更长、更热的系统却知之甚少。我们打算在：(1)欧洲的海西期变质系统，包括西德黑森林的经典混合岩地区，研究这种“热液-深安质”岩浆。(2)裂谷带环境中的火山作用，特别是在冰岛、内华达州的大盆地和爱达荷州的蛇河平原。(3)阿拉伯扩张中心，包括22 Ma的陆上热液系统(红海的开放)和95 Ma的海底系统(阿曼蛇绿岩杂岩)。此外，我们还需要提高对大陆地壳和上地幔18O/16O地球化学的认识，特别是在：(4)不同类型和变质级别的碎屑沉积岩，以更好地确定成岩、变质和熔融过程中18O/16O和D/H的地球化学旋回。(5)意大利北部的伊夫雷亚地带，可能是穿越最低大陆地壳的最佳可用地段。(6)意大利第四纪火成岩。(7)榴辉岩和方橄榄岩包体，以更好地确定上地幔流体-岩石相互作用，并试图识别这些次大陆岩石圈中的古代俯冲洋壳。