Hi edge,
I apologize for the tone of my last message. I am coming to realize that I have become more and more defensive during this discussion. I hope to be able to change that in the future.
I am presently considering starting another thread to continue the discussion of how much of this water (H2O or OH) in the mantle could feasibly (naturally) be brought to the surface in a short time. Before I state the OP, I would like to make sure that I am understanding most of the science of this topic.
edge writes:
Tell ya what. Why not consider me to be your scientific source until you've had an igneous and metamorphic petrology class.
I think I will take you up on that. I need a scientific source, and I do try to listen. I am hardheaded at times, but I am learning. I also get frustrated at times. You have probably figured out by now that I am not a Geologist, or a Chemist, or a Biologist, etc.
If you would like, maybe you can help me to understand this overall process a little better. It may also help those non-scientific people who have been reading this thread to have a better understanding of what is taking place, and what we have been talking about for many, many posts. Here goes nothing:
My original understanding was that the chemical bonding that takes place in these rocks with the water in the mantle was similar to the chemical solution that you would have with water in the ocean, or fluoride in drinking water, etc. I am sure it would be difficult to find any water that is 100% pure unless it was in a laboratory or something. This was the reason for my defensive tone. In my mind, I had two concepts for water. The first was form; Water could be liquid, frozen, evaporated, or gas. The second was purity; you can have ocean water, chlorinated water, fluoride water, etc. Therefore, I was seeing mantle water as in gas form and it was mixed with minerals or rocks.
Now it appears to me, from what I am being told, that after the water reaches a certain pressure and temperature it converts to OH. I truly had the impression from all of those articles that I read that H2O was present in the deep mantle. I thought that some of the water in the deep mantle was chemically bonded as H2O and some as OH. I gather this understanding was incorrect.
Here is a quote of something I read on the internet about the formation of magma. I think it is explaining (remember I am not a Geologist) this process in layman’s terms.
quote:
Water is introduced into the deep Earth when oceanic plates descend beneath continental plates, a process called subduction. Oceanic plates, such as the Juan de Fuca plate off the Oregon and Washington coasts, have thick, water-laden sediments at their surface. When these plates subduct, some of the sediments are dragged deep beneath the continents.
As a plate descends, the pressures and temperatures it experiences increase, and the water-laden sediments are baked (metamorphosed) and squeezed into new types of rock. At about 100 kilometers (62 miles) in depth, these metamorphosed sediments are transformed yet again, and during this second metamorphism, water is released from the newly formed metamorphic rock.
The released water immediately vaporizes at these temperatures and pressures, and the vapor rises. As the vapor moves upward, it enters hotter rocks, since the deeper rocks have not had time to warm up to the surrounding temperatures and have cooled somewhat due to energy being removed as rising water vapor. These shallower rocks are so hot (1,300C or 2,372F) that they are near their melting points. The presence of the water in its vapor phase causes the melting point to decrease and the rock to melt and absorb the vapor. Thus, 100 kilometers (62 miles) beneath the western parts of Oregon and Washington, magma is forming.
http://www.waterencyclopedia.com/...Volcanoes-and-Water.html
If I am reading this correctly and tying it into what you and others have said, this is what I understand:
- The water in the sediment that enters into the mantle through subduction is H2O.
- As the water and sediment sink, metamorphism takes place and the water becomes chemically bonded to the rock.
- When the newly metamorphic rock sinks to 100 kilometers, then a second metamorphism takes place and water vapor is released.
- The second metamorphosed rock with the remaining water chemically bonded continues to sink to the deep mantle.
- The released vapor rises and becomes chemically bonded with other rocks to form magma.
Now we have either H2O or OH in four places that I can see:
- The metamorphosed sediment that is sinking from the surface.
- The newly metamorphic rock sinking below 100 kilometers.
- The water vapor rising towards the surface which has not yet bonded to form magma.
- The magma near the surface.
Does this understanding sound correct? Can you tell me in these four places which would contain H2O, and which would have OH chemically bonded with the mineral (rock)?
Wumpini writes:
They all give the notation of H2O.
edge writes:
And with enough heat, you could drive the the hydroxyl out at water. The key would be a metamorphic reaction.
Could you explain this statement as it applies to what I have explained above?
edge writes:
Yes, water can degass during an eruption, but these effects are occurring very high in the mantle and at the surface, and have nothing to do with the bulk of the mantle rock where your 5 oceans worth of water are occurring.
This confuses me also. You may have already answered this question above when I talked about the different places that water appears to be present in the mantle. Some of that water seemed to be near the surface. The water vapor that had escaped and was rising, the water bound sediment from subduction that had not yet reached 100 kilometers deep, and the magma. All of these were within 100 kilometers of the surface, if my understanding is correct.
Then, I read statements such as this one that I quoted before about the silicates:
quote:
. combined with the recent recognition that quantities of water equivalent to several ocean volumes may be stored in the uppermost mantle in dense hydrous aluminum silicates .
You had told me before that these were probably high temperature hydrated minerals or dissolve hydroxide in magma.
I realize that the five oceans that were referenced earlier are in the deep mantle. However, other articles have mentioned significant other water. I know I read one article called the Bejing Anamoly where they said they found a reservoir (Some heavily saturated rock) equal to the Artic Ocean beneath Eastern Asia.
Would this not indicate that there is substantial water stored in the upper mantle near the crust? This would be water in magma, or in high temperature hydrated minerals, or water vapor that has not yet chemically bound to form magma.
edge writes:
This is a minute amount of water. How much of the mantle do you think you would have to expose to some kind of heating condition to generate 5 oceans of water from such minute amounts. What you don't understand is that the mantle is the largest residence of mass for the entire earth. Even tiny amounts of water in it would generate huge quantities. The point, however, is that this is simply 'water'.
I do not understand the part about a heating condition. What kind of heating condition could affect the deep mantle to release significant water? Is there such a thing? Is there some website that I can look at to see all of these relationships?
edge writes:
Regardless, you are talking about dessicating and changing the mineralogy of a significant part of the mantle. Then you need the reaction to go backward.... all in one year. Are you telling me that this does not sound silly?
I am being very careful to use the right tone.
To be quite honest it sounds less silly to me than the Big Bang Theory (without a supernatural cause), or Abiogenesis where you must theorize about nonliving matter coming together by chance, or nature putting together a complex structure like a wing through a lot of simple steps by natural selection when the wing would never function until it was complete. We have never witnessed or been able to repeat any of these theories of science. But, science allows for these theories. They are accepted.
However, with this process of earth degassing we have evidence. The water in the mantle is coming to the surface right now. We know that, and we can witness the process through volcanic activity. Scientists say another significant source is through the crustal metamorphic fluid system. Therefore, I can conclude with almost complete assurance that some of this water was coming to the surface 5000 years ago. I can also conclude with almost complete assurance that more of this water could come to the surface than is degassing today without causing a drastic change in the environment. I could also project different series of geological events that could result in the release of some of this water. How much more could come to the surface in what period of time? I have not figured that out yet. What would be the effect on the climate if more came to the surface? I have not figured that out yet either. I think we should give as much credence to scientific theories such as this as we do for Abiogenesis, and other very, very, very improbable events. If someone proposes that a Geological event could have occurred that resulted in a significant increase in this natural degassing process, then it is worth of consideration in my opinion. I do not think that is silly.
If someone proposed that five oceans of water could come up naturally from the mantle in 150 days (without some gigantic offsetting natural cooling agent) and not cause mass destruction? That is silly. It would take a miracle to bring that much water up and control the heat!
The question, in my opinion, is where we draw the line between silly and not silly!
edge writes:
Frankly, I don't care what you believe. When you show me your degrees in Geology, I will start to listen. Until then, you are just misconstruing isolated facts.
I wish it was that easy. It seems that to participate in these forums; I need degrees in Geology, Chemistry, Physics, Logic, Biology, Evolutionary Analysis, Cosmology, and who knows what else. I have been trying to work with what little I know, and I realize that it is taking me time to understand some of these concepts. It frustrates me at times, and I am sure it frustrates others. I have had some tell me that since I am not a scientist, I should stay out of these science forums. What do you think?
I do appreciate your assistance, and I once again apologize for my improper tone in my previous post.
P.S. - Here is another link dealing with Potassium storage in the upper mantle. You were remarking about the lack of information related to chemical bonds in other posts. I really am not sure whether this would help. It does have a lot of chemical symbols with H2O and OH.
Transport and Storage of Potassium in the Earth’s Upper Mantle and Transition Zone: an Experimental Study to 23 GPa in Simplified and Natural Bulk Compositions | Journal of Petrology | Oxford Academic
Edited by Wumpini, : No reason given.
Edited by Wumpini, : spelling
Edited by Wumpini, : Added bullets
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