High-pressure experimental verification of rutile-ilmenite oxybarometer： Implications for the redox state of the subduction zone

• Published in: Science China. Earth sciences 2017-10, Vol.60 (10), p.1817-1825
• Main Authors: Tao, RenBiao, Zhang, LiFei, Stagno, Vincenzo, Chu, Xu, Liu, Xi
• Format: Article
• Language: English
• Subjects: Amphibolites; Atmospheric pressure; Buffers; Carbon dioxide; Computational fluid dynamics; Earth and Environmental Science; Earth Sciences; Eclogite; Fluids; Fugacity; High pressure; Ilmenite; Infiltration; Magma; Mantle; Metamorphic rocks; Oxidation; Oxidoreductions; Oxygen; Pressure; Redox properties; Research Paper; Rock; Rutile; Slabs; Solid solutions; Subduction; Subduction (geology); Subduction zones; 俯冲带; 地壳岩石; 地幔橄榄岩; 氧化还原状态; 金红石型; 钛铁矿; 验证; 高压实验
• ISSN: 1674-7313; 1869-1897
• DOI: 10.1007/s11430-016-9082-5

The more oxidized mantle peridotites above subducting slabs than stable continental areas have been attributed to the infiltration of some oxidizing fluids released from the subducting slabs. However, knowledge for the redox states of the slabs itself is very limited. Until now, few oxybarometers can be directly used to constrain the redox states of the subducting slabs.The rutile-ilmenite oxybarometer was proposed and successfully applied to constrain the oxygen fugacity of mantle assemblages.However, its application to rocks equilibrated at crustal P-T conditions has been hampered by some uncertainties in an early solid solution model of ilmenite. With a newly-released solid solution model for the ilmenite, we have conducted high-P experiments（at 3 and 5 GPa, and 900–1300°C） to test the accuracy of this oxybarometer. The experiments were performed with their oxygen fugacities controlled by the CCO buffer（i.e., C＋O2=CO2）. We demonstrated that the oxygen fugacities calculated for our high-P experimental products by using the rutile-ilmenite oxybarometer were in excellent agreement with the fO2 dictated by the CCO buffer, suggesting a wide applicability of this oxybarometer to crust rocks. As examples, the rutile-ilmenite oxybarometer has been used to constrain the oxygen fugacities of some metamorphic rocks such as eclogite, granulite and amphibolite usually observed from the subduction zones.