EAR-PF: A new oxybarometer to quantify spatial and temporal scales of redox variation in subducting slabs

EAR-PF：一种新的氧压计，用于量化俯冲板片中氧化还原变化的空间和时间尺度

• 批准号: 1855208
• 负责人: Megan Holycross
• 金额: $ 17.4万
• 依托单位: Holycross, Megan Elizabeth
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-06-01 至 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1855208&HistoricalAwards=false
• 关键词: EAR; PF; new; oxybarometer; quantify

Dr. Megan Holycross has been awarded an NSF EAR Postdoctoral Fellowship to investigate how subducting slabs record the Earth's deep oxygen cycle. Her research and public service will take place at the Smithsonian Institution and at Yale University. The availability of oxygen in the solid Earth influences the structure of the planet, the chemistry of rocks and ores as well as the composition of the atmosphere. Mass transfer of oxygen between the Earth's oxidized surface and its reduced interior takes place at subduction zones, but the oxidation state of the subducting slab itself, and its consequences for petrological, geochemical and geodynamic processes in subduction zones, is still poorly understood. Dr. Holycross will perform experiments to calibrate a new proxy for oxygen in eclogites, metamorphic rocks formed on subducting slabs that have made their way back to the surface. Following experimental calibration, she will apply the new proxy to determine how ancient and modern suites of natural eclogites track spatial and temporal variations in the oxidation state of subduction zones. During her tenure as an NSF Postdoctoral Fellow, Dr. Holycross will host educational events at both the National Museum of Natural History and the Yale Peabody Museum of Natural History to share the excitement of geoscience with the public. She will also develop a virtual peer-to-peer mentoring and support group to connect early career scientists at 8+ U.S. institutions. Eclogites form on subducting slabs during high-pressure and high-temperature alteration of oceanic basalts. Therefore they may retain important information about the oxidation state (or oxygen fugacity, fO2) of their basalt precursor, or alternately, their oxidation state may be a result of the mass transfer of oxidized materials throughout the subduction system. Comprehensive interrogation of the eclogite fO2 record, and understanding the geological significance of these values, requires an experimentally calibrated proxy that can be applied to natural samples using commonly available analytical tools. Eclogitic mineral assemblages (here, rutile, garnet and pyroxene) are excellent candidates for the development of a new fO2 proxy that will utilize the sensitivity of the multivalent trace element vanadium (V) to changes in redox environment. Vanadium shifts speciation (V2+, V3+, V4+, V5+) over Earth-relevant fO2s, and thus the incorporation of Vanadium in different phases should change as function of oxygen fugacity. Eclogite-melting piston-cylinder experiments will be run to calibrate the partitioning of Vanadium between rutile, pyroxene, garnet and silicate melt as a function of fO2, pressure and temperature. The new fO2 proxy will be applied to Archean eclogite xenoliths from West Africa and an exhumed Eocene terrane from the Cyclades subduction complex in Greece to probe redox changes in subducting slabs over time (scale of billions of years) and space (scale of a subduction zone).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Megan Holycross博士被授予NSF耳朵博士后研究金，以调查俯冲板如何记录地球的深氧周期。她的研究和公共服务将在史密森尼机构和耶鲁大学举行。固体地球中氧的可用性会影响行星的结构，岩石和矿石的化学以及大气的组成。地球氧化表面及其还原内部之间氧气的传质发生在俯冲带上，但是俯冲板本身的氧化态及其对俯冲锌酮中岩石学，地球化学和地球动力学过程的后果仍然很熟悉。 Holycross博士将进行实验，以校准氧气中的氧气代理，该氧气是在俯冲板上形成的变质岩石，这些岩石已恢复到表面。经过实验性校准，她将应用新的代理，以确定俯冲带氧化状态中的天然eclogites古老和现代套件如何跟踪空间和时间变化。在担任NSF博士后研究员期间，Holycross博士将在国家自然历史博物馆和耶鲁·皮博迪自然历史博物馆举办教育活动，与公众分享地球科学的兴奋。她还将开发一个虚拟的点对点指导和支持小组，以连接美国8多个美国机构的早期职业科学家。海洋玄武岩的高压和高温改变期间，在俯冲平板上形成了eclogites。因此，他们可以保留有关其玄武岩前体的氧化态（或氧赋形性，fo2）的重要信息，或者交替，它们的氧化态可能是整个俯冲系统中氧化材料的质量转移的结果。对Eclogite FO2记录的全面询问以及了解这些值的地质意义，需要实验校准的代理，可以使用常用的分析工具将其应用于天然样品。 Eclogitic矿物组合（此处，金红石，石榴石和辉石）是开发新的FO2代理的极好候选者，该代理将利用多价痕量元素钒（V）对氧化还原环境变化的敏感性。钒转移物种形成（V2+，V3+，V4+，V5+）在相关的FO2上，因此在不同阶段中掺入钒应随着氧散性的功能而变化。将运行Eclogite融合活塞缸实验，以校准金红石，辉石，石榴石和硅酸盐在FO2，压力和温度的函数之间校准钒的分配。新的FO2代理将适用于来自西非的大古岩石岩石组织，并从希腊的Cyclades俯冲络合物中挖掘出始新世的地形，以探测俯冲板的变化，随着时间的推移（数十亿年的规模）和空间（通过降低范围的规模）。智力优点和更广泛的影响审查标准。

项目成果

Experimental quantification of vanadium partitioning between eclogitic minerals (garnet, clinopyroxene, rutile) and silicate melt as a function of temperature and oxygen fugacity

• DOI: 10.1007/s00410-022-01888-8
• 发表时间: 2022-01
• 期刊: Contributions to Mineralogy and Petrology
• 影响因子: 3.5
• 作者: M. Holycross;E. Cottrell

Slab-derived devolatilization fluids oxidized by subducted metasedimentary rocks

• DOI: 10.1038/s41561-022-00904-7
• 发表时间: 2022-03
• 期刊: Nature Geoscience
• 影响因子: 18.3
• 作者: J. Ague;S. Tassara;M. Holycross;Ji‐Lei Li;E. Cottrell;E. Schwarzenbach;C. Fassoulas;T. John

Fe Kα XANES, Fe Kβ HERFD XANES and EPMA flank method determinations of the oxidation state of Fe in garnet

Fe Kα XANES、Fe Kβ HERFD XANES 和 EPMA 侧翼法测定石榴石中 Fe 的氧化态

• DOI: 10.1016/j.chemgeo.2024.121937
• 发表时间: 2024
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: Holycross, Megan;Cottrell, Elizabeth;Ague, Jay;Lanzirotti, Antonio;Newville, Matthew
• 通讯作者: Newville, Matthew

Garnet crystallization does not drive oxidation at arcs

石榴石结晶不会导致电弧氧化

• DOI: 10.1126/science.ade3418
• 发表时间: 2023
• 期刊: Science
• 影响因子: 56.9
• 作者: Holycross, Megan;Cottrell, Elizabeth
• 通讯作者: Cottrell, Elizabeth