| 项目编号: | 1550929
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| 项目名称: | Understanding Chromium Redox Systematics Mafic Magmas: Applications to Magmatic fO2 Calculations and Chromite Solubility |
| 作者: | Aaron Bell
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| 承担单位: | University of New Mexico
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| 批准年: | 2016
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| 开始日期: | 2016-07-01
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| 结束日期: | 2019-06-30
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| 资助金额: | 285761
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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: | study
; mafic magma
; fo2
; chromite stability
; oxidation state
; chromite
; layered mafic intrusion
; basaltic magmas
; chromite crystallization
; chromite deposit
; cr-redox behavior
; element chromium
; stratiform chromite ore deposit
; quantitative redox chronometer
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| 英文摘要: | Stratiform chromite deposits hosted in layered mafic intrusions are by far the most economically important source of the element Chromium (Cr). Chromium is a key ingredient required for the manufacturing of stainless steel alloys, as well as a myriad of other technologically important 'super alloys'. While it is widely accepted that the chromite deposits found in layered mafic intrusions are a crystallization product of a parental magma body, the fundamental geochemical processes that induce the crystallization of chromite in the magma bodies that host these deposits are still poorly understood and the subject of much scientific debate. One of the main objectives of this study is to quantify how variables such as the chemical composition of a silicate melt and the oxidation state of the Cr dissolved in the silicate melt affect the crystallization behavior of chromite. The results generated from this study can be used to deduce the chemical circumstances under which mafic magmas become saturated with and crystallize chromite. In a broader context, the results of this study can also be applied to quantifying the oxidation state of mafic magmas. Developing new tools to quantify the oxidation state of basaltic magmas is a foundational aspect of understanding the oxidation state of the earth?s mantle and a major step toward understanding the speciation and mobility of volatile elements between the deep earth and surficial reservoirs. This project will support a masters or doctoral student at the University of New Mexico, as well as an undergraduate student thesis. Both of these students will be trained in state-of-the-art analytical and experimental techniques and assist in research conducted at a U.S. synchrotron facility.
Understanding chromite stability is a critical aspect of developing models for the formation mechanisms of stratiform chromite ore deposits associated with layered mafic intrusions. Chromite stability in basaltic magmas is influenced by variables such as temperature, pressure, the chemical composition of the melt, and its oxidation state (i.e. fO2). The primary objective of this study is to produce a quantitative portrait of Cr-redox behavior and chromite stability in mafic magmas and how it relates to the aforementioned variables. This study combines high temperature-pressure petrology experiments conducted at the University of New Mexico with X-ray Absorption Near Edge Structure (XANES) measurements of Cr valence ratios in the experimentally grown olivine crystals and quenched melts. The XANES measurements will be conducted at the Advanced Photon Source, Argonne National Laboratory. The phase equilibria and Cr valence data generated by this study will be used to develop a new geochemical model of chromite crystallization in mafic magmas. Furthermore, the Cr valence measurements in olivine crystals will be used to develop a new tool for assessing the fO2 of basaltic magmas. A preliminary investigation has shown that the Cr-valence in olivine records changes in fO2 that may have occurred during pheoncryst growth. In this way, Cr valence measurements in olivine may be developed into a robust, quantitative redox chronometer for magmatic systems. |
| 资源类型: | 项目
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/92020
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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: | |
Aaron Bell. Understanding Chromium Redox Systematics Mafic Magmas: Applications to Magmatic fO2 Calculations and Chromite Solubility. 2016-01-01.
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