Phase equilibria in the system Fe-Zn-O at intermediate conditions between metallic-iron saturation and air

2005 ◽  
Vol 36 (2) ◽  
pp. 179-185 ◽  
Author(s):  
Robert Hansson ◽  
Peter C. Hayes ◽  
Evgueni Jak
Keyword(s):  
Phase Equilibria ◽  
Metallic Iron ◽  
Iron Saturation

scholarly journals Metallic iron limits silicate hydration in Earth’s transition zone

2019 ◽  
Vol 116 (45) ◽  
pp. 22526-22530
Author(s):  
Feng Zhu ◽  
Jie Li ◽  
Jiachao Liu ◽  
Junjie Dong ◽  
Zhenxian Liu
Keyword(s):  
Transition Zone ◽  
Metallic Iron ◽  
Water Distribution ◽  
Water Flux ◽  
Current Estimate ◽  
Structural Water ◽  
Apparent Contradiction ◽  
Iron Saturation ◽  
Iron Metal ◽  
Iron Hydride

The Earth’s mantle transition zone (MTZ) is often considered an internal reservoir for water because its major minerals wadsleyite and ringwoodite can store several oceans of structural water. Whether it is a hydrous layer or an empty reservoir is still under debate. Previous studies suggested the MTZ may be saturated with iron metal. Here we show that metallic iron reacts with hydrous wadsleyite under the pressure and temperature conditions of the MTZ to form iron hydride or molecular hydrogen and silicate with less than tens of parts per million (ppm) water, implying that water enrichment is incompatible with iron saturation in the MTZ. With the current estimate of water flux to the MTZ, the iron metal preserved from early Earth could transform a significant fraction of subducted water into reduced hydrogen species, thus limiting the hydration of silicates in the bulk MTZ. Meanwhile, the MTZ would become gradually oxidized and metal depleted. As a result, water-rich region can still exist near modern active slabs where iron metal was consumed by reaction with subducted water. Heterogeneous water distribution resolves the apparent contradiction between the extreme water enrichment indicated by the occurrence of hydrous ringwoodite and ice VII in superdeep diamonds and the relatively low water content in bulk MTZ silicates inferred from electrical conductivity studies.

Phase equilibria in partially open systems under pressure: the decomposition of stoichiometric GeO2 oxide

2003 ◽  
Vol 173 (12) ◽  
pp. 1359 ◽  
Author(s):  
Vadim V. Brazhkin ◽  
Roman N. Voloshin ◽  
A.G. Lyapin ◽  
Svetlana V. Popova
Keyword(s):  
Phase Equilibria ◽  
Open Systems
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