{"title":"Fe2+对铁镁石向菱镁石转变的影响及其俯冲动力学意义","authors":"Priyanka Pandit, Prathibha Chandrashekhar, Sparsh Sharma, Gaurav Shukla","doi":"10.1029/2024GC012010","DOIUrl":null,"url":null,"abstract":"<p>Seismic studies in cold subduction zones indicate several discontinuity structures near the 660-km boundary. Studies indicate that the akimotoite to bridgmanite transition may play a significant role in unraveling the complexity of this region. In this study, we used first-principles methods to explore the stability field of iron-rich analogs of akimotoite and bridgmanite (<span></span><math>\n <semantics>\n <mrow>\n <mfenced>\n <mrow>\n <mi>M</mi>\n <msub>\n <mi>g</mi>\n <mrow>\n <mn>1</mn>\n <mo>−</mo>\n <mi>x</mi>\n </mrow>\n </msub>\n <mi>F</mi>\n <msubsup>\n <mi>e</mi>\n <mi>x</mi>\n <mrow>\n <mn>2</mn>\n <mo>+</mo>\n </mrow>\n </msubsup>\n </mrow>\n </mfenced>\n <mi>S</mi>\n <mi>i</mi>\n <msub>\n <mi>O</mi>\n <mn>3</mn>\n </msub>\n </mrow>\n <annotation> $\\left(M{g}_{1-x}F{e}_{x}^{2+}\\right)Si{O}_{3}$</annotation>\n </semantics></math> under high-pressure-temperature conditions. The Fe<sup>2+</sup> inclusion significantly reduces the phase transition pressure. Overall, our calculated phase boundary and thermoelastic properties compare well with the available results from previous studies. The onset transition pressure and the width of the two-phase field exhibit a clear dependence on iron concentration, with the width of the two-phase field increasing as iron concentration increases. Our results indicate that the relatively high Fe<sup>2+</sup> (∼<i>x</i> = 0.5) found in natural Fe analogs of akimotoite and bridgmanite would not be possible under mantle transition conditions. However, Fe<sup>2+</sup> incorporation relevant for mantle composition (<10 mol.% FeO) may explain the slab stagnation above 660 km depth as well as seismically observed trends of velocity perturbations in the slabs of the northwest Pacific region around ∼500–600 km depth.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 3","pages":""},"PeriodicalIF":3.0000,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012010","citationCount":"0","resultStr":"{\"title\":\"Effect of Fe2+ on Akimotoite to Bridgmanite Transition: Its Implication on Subduction Dynamics\",\"authors\":\"Priyanka Pandit, Prathibha Chandrashekhar, Sparsh Sharma, Gaurav Shukla\",\"doi\":\"10.1029/2024GC012010\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Seismic studies in cold subduction zones indicate several discontinuity structures near the 660-km boundary. Studies indicate that the akimotoite to bridgmanite transition may play a significant role in unraveling the complexity of this region. In this study, we used first-principles methods to explore the stability field of iron-rich analogs of akimotoite and bridgmanite (<span></span><math>\\n <semantics>\\n <mrow>\\n <mfenced>\\n <mrow>\\n <mi>M</mi>\\n <msub>\\n <mi>g</mi>\\n <mrow>\\n <mn>1</mn>\\n <mo>−</mo>\\n <mi>x</mi>\\n </mrow>\\n </msub>\\n <mi>F</mi>\\n <msubsup>\\n <mi>e</mi>\\n <mi>x</mi>\\n <mrow>\\n <mn>2</mn>\\n <mo>+</mo>\\n </mrow>\\n </msubsup>\\n </mrow>\\n </mfenced>\\n <mi>S</mi>\\n <mi>i</mi>\\n <msub>\\n <mi>O</mi>\\n <mn>3</mn>\\n </msub>\\n </mrow>\\n <annotation> $\\\\left(M{g}_{1-x}F{e}_{x}^{2+}\\\\right)Si{O}_{3}$</annotation>\\n </semantics></math> under high-pressure-temperature conditions. The Fe<sup>2+</sup> inclusion significantly reduces the phase transition pressure. Overall, our calculated phase boundary and thermoelastic properties compare well with the available results from previous studies. The onset transition pressure and the width of the two-phase field exhibit a clear dependence on iron concentration, with the width of the two-phase field increasing as iron concentration increases. Our results indicate that the relatively high Fe<sup>2+</sup> (∼<i>x</i> = 0.5) found in natural Fe analogs of akimotoite and bridgmanite would not be possible under mantle transition conditions. 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引用次数: 0
摘要
在冷俯冲带的地震研究表明,在660公里边界附近有几个不连续构造。研究表明,钾辉石向桥辉石的转变可能对揭示该地区的复杂性起着重要作用。在这项研究中,我们用第一性原理方法探索了富铁类似物铁辉石和桥辉石(m1−x F)的稳定性场e x 2 + S i O 3$\左(M{g}_{1-x}F{e}_{x}^{2+}\右)Si{O}_{3}$。Fe2+包体显著降低了相变压力。总的来说,我们计算的相边界和热弹性性能与以前的研究结果比较好。起始过渡压力和两相场宽度与铁浓度有明显的相关性,两相场宽度随铁浓度的增加而增大。我们的研究结果表明,在地幔转变条件下,天然铁类似物中相对较高的Fe2+ (~ x = 0.5)是不可能存在的。然而,与地幔组成相关的Fe2+掺入(<10 mol.% FeO)可以解释660 km深度以上的板块停滞,以及西北太平洋地区在~ 500-600 km深度附近的板块中地震观测到的速度扰动趋势。
Effect of Fe2+ on Akimotoite to Bridgmanite Transition: Its Implication on Subduction Dynamics
Seismic studies in cold subduction zones indicate several discontinuity structures near the 660-km boundary. Studies indicate that the akimotoite to bridgmanite transition may play a significant role in unraveling the complexity of this region. In this study, we used first-principles methods to explore the stability field of iron-rich analogs of akimotoite and bridgmanite ( under high-pressure-temperature conditions. The Fe2+ inclusion significantly reduces the phase transition pressure. Overall, our calculated phase boundary and thermoelastic properties compare well with the available results from previous studies. The onset transition pressure and the width of the two-phase field exhibit a clear dependence on iron concentration, with the width of the two-phase field increasing as iron concentration increases. Our results indicate that the relatively high Fe2+ (∼x = 0.5) found in natural Fe analogs of akimotoite and bridgmanite would not be possible under mantle transition conditions. However, Fe2+ incorporation relevant for mantle composition (<10 mol.% FeO) may explain the slab stagnation above 660 km depth as well as seismically observed trends of velocity perturbations in the slabs of the northwest Pacific region around ∼500–600 km depth.
期刊介绍:
Geochemistry, Geophysics, Geosystems (G3) publishes research papers on Earth and planetary processes with a focus on understanding the Earth as a system. Observational, experimental, and theoretical investigations of the solid Earth, hydrosphere, atmosphere, biosphere, and solar system at all spatial and temporal scales are welcome. Articles should be of broad interest, and interdisciplinary approaches are encouraged.
Areas of interest for this peer-reviewed journal include, but are not limited to:
The physics and chemistry of the Earth, including its structure, composition, physical properties, dynamics, and evolution
Principles and applications of geochemical proxies to studies of Earth history
The physical properties, composition, and temporal evolution of the Earth''s major reservoirs and the coupling between them
The dynamics of geochemical and biogeochemical cycles at all spatial and temporal scales
Physical and cosmochemical constraints on the composition, origin, and evolution of the Earth and other terrestrial planets
The chemistry and physics of solar system materials that are relevant to the formation, evolution, and current state of the Earth and the planets
Advances in modeling, observation, and experimentation that are of widespread interest in the geosciences.