| 项目编号: | 1623110
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| 项目名称: | An Experimental Calibration of the Fractionation of Boron Isotopes among Granitic Melt, Aqueous Fluid, and Tourmaline |
| 作者: | David London
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| 承担单位: | University of Oklahoma Norman Campus
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| 批准年: | 2016
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| 开始日期: | 2016-06-15
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| 结束日期: | 2018-05-31
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| 资助金额: | 314562
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| 资助来源: | US-NSF
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| 项目类别: | Continuing grant
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| 国家: | US
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| 语种: | 英语
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| 特色学科分类: | Geosciences - Earth Sciences
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| 英文关键词: | tourmaline
; fractionation
; boron isotope
; aqueous solution
; boron
; diffusion-controlled fractionation
; stable isotope
; aqueous fluid
; mineral-melt equilibrium
; granitic liquid
; boron isotopic composition
; earth
; boron isotopic system
; consistent calibration
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| 英文摘要: | Understanding how the Earth evolves in time is central to the geosciences. Toward that end, there is always a need for analytical tools or methods that may shed light on those processes of change and how these processes operate on the natural environment. The relative abundance of stable isotopes of light elements tend to be fractionated between coexisting phases (i.e., different minerals, gas, magma, biota) by a number of organic and inorganic processes. These natural interactions that fractionate stable isotopes are occurring constantly as the earth and its biosphere evolve. For that reason, stable isotope distributions have played a very large role in elucidating some of the processes operating throughout the earth's chemical history. The stable isotope systematics of H, C, and O are widely studied, calibrated, and utilized. Recent studies have heralded the boron isotopic system, 10B and 11B, as potentially revolutionary. Boron is concentrated in ocean waters, altered oceanic crust, in marine sediments, and in silicate magmas and aqueous fluids that are derived from them. There is a hope among researchers that the fractionation of 10B and 11B among minerals, melts, and aqueous solutions may yield important insights into the chemical evolution of the continental crust. So far, the laboratory analyses of boron isotopes in natural samples have failed to provide an understandable and consistent picture of their chemical behavior. One body of work cites little or no fractionation of boron isotopic composition among coexisting aqueous solution, granitic liquid, and tourmaline, the principal mineralogical carrier of boron in the earth, while other analytical data point to very large ranges in the fractionation of boron isotopes in tourmaline, even within a single geologic occurrence. The goal of this research, therefore, is to complete an experimental program that yields an internally consistent calibration of the partitioning of the boron isotopes among granitic melt, aqueous solution, and tourmaline at elevated pressures and temperatures.
Three series of experiments will measure the fractionation of 10B and 11B between granitic melt and aqueous solution. The use of multiple experimental methods, and reversals in the direction of diffusive mixing of the isotopes, will provide robust tests of the attainment of equilibrium distributions. The fractionation of boron isotopes between tourmaline and melt will also be measured through synthesis experiments. These latter experiments will test a hypothesis that the wide range in the isotopic composition of tourmaline stems from diffusion-controlled fractionation of the isotopes of boron attending the crystallization of tourmaline at states far from the mineral-melt equilibrium. |
| 资源类型: | 项目
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/92037
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| Appears in Collections: | 全球变化的国际研究计划
科学计划与规划
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| Recommended Citation: | |
David London. An Experimental Calibration of the Fractionation of Boron Isotopes among Granitic Melt, Aqueous Fluid, and Tourmaline. 2016-01-01.
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