Metallic iron limits silicate hydration in Earth's transition zone
Feng Zhu1, Jie Li2, Jiachao Liu2
1Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109; fzhuum@umich.edu.
Summary
Metallic iron in the Earth's mantle transition zone reacts with water, forming hydrogen and limiting silicate hydration. This suggests water is not evenly distributed, with wet areas near active slabs where iron has reacted.
Area of Science:
- Geophysics
- Mineral Physics
- Geochemistry
Background:
- The Earth's mantle transition zone (MTZ) potentially stores vast amounts of water in minerals like wadsleyite and ringwoodite.
- The MTZ's water content is debated, with some studies suggesting it might be iron-saturated.
Purpose of the Study:
- To investigate the reaction between metallic iron and hydrous wadsleyite under MTZ conditions.
- To determine the impact of iron on water storage capacity in the MTZ.
Main Methods:
- Experimental petrology simulating MTZ pressure and temperature conditions.
- Analysis of reaction products between metallic iron and hydrous wadsleyite.
Main Results:
- Metallic iron reacts with hydrous wadsleyite, producing iron hydride or molecular hydrogen and significantly reducing water content in silicates (to <10 ppm).
- Iron saturation is incompatible with significant water enrichment in the MTZ.
- Subducted water can be converted to hydrogen species by preserved early Earth iron, limiting bulk MTZ hydration and oxidizing the MTZ.
Conclusions:
- Heterogeneous water distribution in the MTZ is proposed, reconciling high water content near subduction zones with low bulk MTZ water content.
- Water-rich regions may exist where iron has been consumed by reactions with subducted water.
- The presence of metallic iron limits the overall hydration of the mantle transition zone.
Related Concept Videos
02:32Bonding in Metals
51.6K
Metallic bonds are formed between two metal atoms. A simplified model to describe metallic bonding has been developed by Paul Drüde called the “Electron Sea Model”.
51.6K
01:28Transition Zone
320
The transition zone in concrete is a critical area where aggregate meets cement paste, marked by a distinct porosity and weakness compared to the surrounding material. The adhesion around the aggregates is primarily due to Van Der Waals forces. The voids within this zone influence its robustness; initially, it is less durable than the surrounding bulk mortar due to larger voids. Initially, when concrete is compacted, a higher water-cement ratio near the aggregates leads to the formation of...
320
01:24Hydration of Cement
738
Hydration of cement is a chemical reaction between cement particles and water. This process occurs primarily through two mechanisms: through-solution and topochemical. In the through-solution process, anhydrous compounds dissolve into their constituents, hydrates form in the solution, and then precipitate from the supersaturated solution. The topochemical process involves solid-state reactions at the cement particle surface. The through-solution process dominates the topochemical process at the...
738
01:31Ferromagnetism
2.9K
Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...
2.9K
03:45Formation of Complex Ions
25.5K
A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...
25.5K
02:58Properties of Transition Metals
29.3K
Transition metals are defined as those elements that have partially filled d orbitals. As shown in Figure 1, the d-block elements in groups 3–12 are transition elements. The f-block elements, also called inner transition metals (the lanthanides and actinides), also meet this criterion because the d orbital is partially occupied before the f orbitals.
29.3K