Hydrothermal water and surface/mantle interaction

[wellwisher]

This idea came to me years ago and was based on research I did growing hydrothermal crystals. As we heat water to high temperatures and pressures, water becomes a very aggressive solvent for minerals found on the earth, such as silicates. The solvent power of supercritical or hydrothermal water increases if we add small ions to the hydrothermal water, such as sodium.

In the lab, one technique for growing quartz crystals (silicates) is a device as shown below. What you do is create a thermal gradient where the top is slightly cooler than the bottom, which is slightly hotter. The minerals dissolve more in the hotter bottom. They then float up within the convection of the water and cool at the top. At the top you have a tiny seed crystal, which is perfect. Because the top is cooler, nd the solubility is lower, the minerals precipitate out onto the crystal. The cooler water then convects downward, where it now has more solvent power when it reaches the hotter bottom of the device. This is slow and may take weeks since you may only use 1-10C thermal gradient with the device at 1000C.




If we look at this device, in terms of the earth's water, since the mantle of the earth is hotter and forms a thermal gradient to the cooler surface, hydrothermal water should eat downward and deposit minerals above itself, like the device. This would result in water eating its way into the mantle. This device and the thousands of runs by hundreds of scientists repeatably demonstrate the concept that hydrothermal water will eat in the direction of hotter.

The question is, what would be the impact of such hydrothermal water convection to the mantle. Does it act like a dissolving grease for plate movement? Also if a large slug of water finally breaches the mantle you get sudden non equilibrium.

[wlminex]

descending hydrothermal waters DO dissolve minerals in the mantle . . . . . . usually those minerals that are the last to crystalize (i.e, incompatibles, etc. --> hydrous mineral phases (first) --> silicates --> oxides (last). This process usually produces initial volatile-charged partial melts (or plumes) in the mantle. Eruption of these partial melts may be diamond-bearing kimberlite or lamproite, if formed within the diamond stability PT field, or non-diamondiferous magmas (e.g., non-diamindiferous kimberlites, lamproites, basalts, other etc.). Yes . . . it works very similar to your lab model.

[wellwisher]

The abilioty of hydrothermal water to follow the thermal gradient downward, suggests that the crust of the earth is floating on a water/mineral equilibrium based on the concentration of hydrothermal solvent water. Less water allows more crust material to precipiate making the crust stickier, while more water dissolves the crust adding some grease for slip.

One of the theories for how the earth got its water is connected to water rich asteroids hitting the earth. Picture large water ladden asteroids plunging into the crust, sealing themselves within the crust. Now a have large pools of hydrothermal water following the thermal, eating their way downward. Once these breech the crust/mantle interface, this alters the water/mineral equilibirum at the crust/mantle interface (move dissolving power) so it slide at a faster rate.

[origin]

The abilioty of hydrothermal water to follow the thermal gradient downward, suggests that the crust of the earth is floating on a water/mineral equilibrium based on the concentration of hydrothermal solvent water.

No, it does not suggest that at all. All evidence indicates that this is not what is happening. You took a swan dive off a cliff when you went from solution crystal formation to the crust of the earth is floating on water.

[wellwisher]

An interesting observation is a place on the ocean floor in the Atlantic ocean where there is no crust and the mantle of the earth interfaces the ocean water, directly. Water does touch the mantle.

http://www.sciencedaily.com/releases...0301103112.htm

[origin]

An interesting observation is a place on the ocean floor in the Atlantic ocean where there is no crust and the mantle of the earth interfaces the ocean water, directly. Water does touch the mantle.

http://www.sciencedaily.com/releases...0301103112.htm

Interesting, it does not support your idea but it is interesting.

[Trippy]

Interesting, it does not support your idea but it is interesting.

Crustal Evolution of the Mid-Atlantic Ridge near the Fifteen-Twenty Fracture Zone in the last 5 Ma

[Trippy]

An interesting observation is a place on the ocean floor in the Atlantic ocean where there is no crust and the mantle of the earth interfaces the ocean water, directly. Water does touch the mantle.

http://www.sciencedaily.com/releases...0301103112.htm

The water does not interface directly with the mantle. There is a layer of rock between the mantle and the crust. Serpentite, to be precise. This is important, and leads to the comments made about the crust being missing because Serpentite is rich in Serpentine, which is found in the upper mantle.

What it doesn't mean is that there is a stable seeting pool of upper mantle melt exposed directly to the ocean at this location.

[Trippy]

What they seem to be saying, is that if you consider this as a typical cross section:

Then what is missing is the basalt layers, and what we seem to be seeing is the underlying Gabbro's and Serpentized Peridotite, as well as some ultramafic accumulates.

[wellwisher]

The reason I inferred that there is water below surface in the mantle is because of the parallel between the layering within the earth, from the mantle to core, and the phases of water at the same conditions.

The mantle temperature near the surface is about 800C and reaches about 4000C at the outer core. The mantle material is solid with viscoplastic movement. Water above 1500C, will become is a superionic solid, where the oxygen of water forms a solid matrix, and the hydrogen protons diffuse freely in the solid. This accounts for solid and viscoplastic.

The outer core of the earth starts at about 4000C and reaches temperatures of about 6100C near core. The outer core is fluid. Water at 3500C becomes an ionic liquid, which accounts for the fluid outer core.

The core of the earth is at about 7300K. Water at 7000K becomes a metallic solid, just like the core.

This is not coincidence. The parallel apears to reflect aqueous phase changes playing a role in the inner layering of the earth. The link below will confirm these extreme aquoeus phases and discusses the catalytic properties of water at extreme conditions; superionic and ionic.

http://www.nature.com/nchem/journal/...nchem.130.html

[wellwisher]

Where I was heading with this is connected to the observation that the earth's core is spinning faster than the surface of the earth, lapping the surface about every 400-500 years. Any model for the earth needs to take this into account, since the required energy for a faster core rotation, should be at the forefront of the earth's internal energy economy. It takes a lot of energy to move a huge iron ball the size of the moon while being resisted by visco-plastic resistance. This can't be just inertia but will need an engine.

http://www.columbia.edu/cu/record/ar...Core_Spin.html

The phase changes of water, into an ionic fluid at the conditions of the outer core and then the phase change of water into a metallic solid, at the conditions of the core, suggest water plays a catalytic a role in the continuous energy production required for the core engine.

As a possible mechanism, metallic iron is electron rich. If there was a mechanism that could get the solid iron core to release electrons, and thereby rust into say iron oxide, we have the electric power needed for the core to spin. This would need to be catalyzed by the water phases near the core.

For example, if water diffused into the iron core at extreme conditions, we get an amalgam of metallic water and metallic iron/nickel. This interfaces a fluid ionic brine at the outer core. There is a flow of free energy.