The extreme pressure and temperature conditions of the deep Earth,reaching up to∼350 gigapascals(GPa)and 6000 K,pose major challenges for in-situ detection and the investigation of physical and chemical processes[1]....The extreme pressure and temperature conditions of the deep Earth,reaching up to∼350 gigapascals(GPa)and 6000 K,pose major challenges for in-situ detection and the investigation of physical and chemical processes[1].Although numerous theoretical simulations and experiments have been conducted under extreme deep-Earth conditions,a centralized platform with practical tools for predicting the reactivity of substances on Earth and beyond is still lacking.Such tools are crucial for advancing our understanding of Earth’s structure,composition,energy exchange,and long-term evolution.展开更多
Subduction zones are important for oxygen cycling between deep and surficial Earth reservoirs.Highly oxidizing materials from Earth’s surface may be transported to the mantle along with the subducting slabs and alter...Subduction zones are important for oxygen cycling between deep and surficial Earth reservoirs.Highly oxidizing materials from Earth’s surface may be transported to the mantle along with the subducting slabs and alter the redox states of the mantle wedge and the 410–660 km transition zone.The circulation of oxygen or oxidizing fluids in subduction zones and how subducted materials influence the deep mantle are poorly constrained.Here we report growth of Fe-Mn garnet from highly oxidized pelagic ferromanganese chert within a high-pressure metamorphic complex in the Qilian Orogen,North West(NW)China.Two types of ferric-iron-rich garnets were identified.Type I is spessartine garnet that has clear compositional zonation of Al2O3-FeOt-MnO oscillatory growth.The Fe^(3+)/∑Fe ratio in the core is as high as 1.0,but decreases to 0.1 in the outer rim,along with an increase of Fe2+content and a significant decrease in Mn content.Type II is andradite-calderite garnet that contains extremely high Fe^(3+).Our results have two implications:(1)continuous reduction of Mn^(4+)(to Mn^(2+))and Fe^(3+)(to Fe2+)from the ferromanganese chert as garnet growth must be accompanied by releasing large quantity of oxygen or highly oxidized fluids during prograde high-pressure metamorphism in subduction zones,and(2)Fe^(3+)-rich garnets together with hematite in the subducting slab can remain stable over a large pressure range,and provide an alternative interpretation for the high content of Fe^(3+)in the deep mantle.Our results are significant for understanding the oxygen recycling in oceanic cold subduction zones,and the initiation of the Great Oxygen Event(GOE)as well.展开更多
基金supported by the National Science and Technology Major Project(2025ZD1010301)the Chinese Academy of Geological Sciences Basal Research Fund(JKYDM2025110)+2 种基金the National Natural Science Foundation of China(42372049,42192502,42302037,92351302,and 62271016)the China Postdoctoral Science Foundation(2023T160007 and 2023M740044)the Regional Special Program(KCX2024003).
文摘The extreme pressure and temperature conditions of the deep Earth,reaching up to∼350 gigapascals(GPa)and 6000 K,pose major challenges for in-situ detection and the investigation of physical and chemical processes[1].Although numerous theoretical simulations and experiments have been conducted under extreme deep-Earth conditions,a centralized platform with practical tools for predicting the reactivity of substances on Earth and beyond is still lacking.Such tools are crucial for advancing our understanding of Earth’s structure,composition,energy exchange,and long-term evolution.
基金supported by the National Key Research and Development Program of China(2023YFF0803803)the National Natural Science Foundation of China(91955202).
文摘Subduction zones are important for oxygen cycling between deep and surficial Earth reservoirs.Highly oxidizing materials from Earth’s surface may be transported to the mantle along with the subducting slabs and alter the redox states of the mantle wedge and the 410–660 km transition zone.The circulation of oxygen or oxidizing fluids in subduction zones and how subducted materials influence the deep mantle are poorly constrained.Here we report growth of Fe-Mn garnet from highly oxidized pelagic ferromanganese chert within a high-pressure metamorphic complex in the Qilian Orogen,North West(NW)China.Two types of ferric-iron-rich garnets were identified.Type I is spessartine garnet that has clear compositional zonation of Al2O3-FeOt-MnO oscillatory growth.The Fe^(3+)/∑Fe ratio in the core is as high as 1.0,but decreases to 0.1 in the outer rim,along with an increase of Fe2+content and a significant decrease in Mn content.Type II is andradite-calderite garnet that contains extremely high Fe^(3+).Our results have two implications:(1)continuous reduction of Mn^(4+)(to Mn^(2+))and Fe^(3+)(to Fe2+)from the ferromanganese chert as garnet growth must be accompanied by releasing large quantity of oxygen or highly oxidized fluids during prograde high-pressure metamorphism in subduction zones,and(2)Fe^(3+)-rich garnets together with hematite in the subducting slab can remain stable over a large pressure range,and provide an alternative interpretation for the high content of Fe^(3+)in the deep mantle.Our results are significant for understanding the oxygen recycling in oceanic cold subduction zones,and the initiation of the Great Oxygen Event(GOE)as well.
