Ice is found deep within the hot interior of the earth. Let that statement sink in. In research published today, a form of super-compact ice, found embedded in diamonds, offers the first direct clue that there is abundant water more than 610 kilometers deep in the mantle.
This ice, identified by its crystal structure and called ice-VII, doesn’t exist at Earth’s surface. It forms only at pressures greater than about 24 gigapascals — corresponding to depths between 610 and 800 kilometers, researchers report today in Science. The structure of ice-VII comprises a hydrogen bond framework in the form of two interpenetrating (but non-bonded) sublattices. Hydrogen bonds pass through the center of the water hexamers (as shown above, and, to some degree below) and thus do not connect the two lattices.
Ice-VII's presence in diamonds suggests that there is water-rich fluid in the transition zone between the upper and lower mantle, and even into the top of the lower mantle.
“This is really the first time that we see water at such depths,” says Dr. Oded Navon, a mantle petrologist at the Hebrew University of Jerusalem.
When slabs of earth’s crust sink into the mantle layer below, they drag ocean water with them. How deep the slabs sink has been a long-standing question. Researchers have suspected that abundant aqueous fluid exists in the deep mantle, carried there by slabs bearing water-rich minerals that shed their water when they reach the transition zone. But scientists have not previously found direct evidence of that water.
That is where diamonds come in. Diamonds form at high temperatures and pressures, crystallizing in pockets rich in the mineral carbonate before being carried to the surface with erupting magma. As the diamond crystals form, they can enclose tiny amounts of fluid or rock from their surroundings. These impurities represent tiny capsules of mantle. Diamond inclusions are the only direct window scientists have into the fabric of earth more than a kilometer beneath the surface.
Dr. Oliver Tschauner, a mineralogist at the University of Nevada, Las Vegas, and his colleagues set out to study diamond inclusions, but they weren’t looking for ice. They were hunting for signs of a molecular form of carbon dioxide that might help reveal clues to the cycling of carbon from slabs into the mantle. The researchers used a variety of techniques, including X-ray diffraction, infrared spectroscopy and X-ray fluorescence, to try to identify the composition of the inclusions within three diamonds, one from China and two from southern Africa.
Instead of carbon dioxide, the team saw a telltale pattern in how some of the X-rays scattered as they passed through the diamond. That pattern pointed to ice-VII. The presence of that extremely high-pressure form of ice was a powerful clue to the depth at which the diamond must have formed. The diamonds also contained separate inclusions of fluids rich in certain salts, such as magnesium calcite and halite, and of carbon-rich fluids.
Water-rich fluids deep in the mantle could be important for driving the circulation that fuels the movements of tectonic plates and the eruptions of volcanoes. The presence of water can make it easier for rocks to melt, Dr. Navon says, by lowering the melting point of hot rock under pressure. Additionally, fluids can help redistribute heat within the mantle.
In addition, some large, heat-producing radioactive elements such as potassium, thorium and uranium don’t fit easily into the rigid crystalline structures of minerals, so scientists prefer melted rock when it’s available. “You just need a little bit of fluid, and they are moving into the melt,” Dr. Navon adds.
The study also raised another mystery. Fluid inclusions within diamonds originating at shallower depths, perhaps 150 to 200 kilometers below the surface, contain a mélange of water, salt, and carbonates. But Dr. Tschauner and his colleagues found that in their deep diamonds, the inclusions are sequestered individually: ice in one inclusion, carbonates in another, salts in yet a third. “We were surprised that they were all separate rather than occurring together,” Dr. Tschauner said.
Any ideas about this mysterious separation in the materials in inclusions?
And, how cool to have remnants of tectonic slabs as inclusions in your jewelry!
Steph
This ice, identified by its crystal structure and called ice-VII, doesn’t exist at Earth’s surface. It forms only at pressures greater than about 24 gigapascals — corresponding to depths between 610 and 800 kilometers, researchers report today in Science. The structure of ice-VII comprises a hydrogen bond framework in the form of two interpenetrating (but non-bonded) sublattices. Hydrogen bonds pass through the center of the water hexamers (as shown above, and, to some degree below) and thus do not connect the two lattices.
Ice-VII's presence in diamonds suggests that there is water-rich fluid in the transition zone between the upper and lower mantle, and even into the top of the lower mantle.
“This is really the first time that we see water at such depths,” says Dr. Oded Navon, a mantle petrologist at the Hebrew University of Jerusalem.
When slabs of earth’s crust sink into the mantle layer below, they drag ocean water with them. How deep the slabs sink has been a long-standing question. Researchers have suspected that abundant aqueous fluid exists in the deep mantle, carried there by slabs bearing water-rich minerals that shed their water when they reach the transition zone. But scientists have not previously found direct evidence of that water.
That is where diamonds come in. Diamonds form at high temperatures and pressures, crystallizing in pockets rich in the mineral carbonate before being carried to the surface with erupting magma. As the diamond crystals form, they can enclose tiny amounts of fluid or rock from their surroundings. These impurities represent tiny capsules of mantle. Diamond inclusions are the only direct window scientists have into the fabric of earth more than a kilometer beneath the surface.
Dr. Oliver Tschauner, a mineralogist at the University of Nevada, Las Vegas, and his colleagues set out to study diamond inclusions, but they weren’t looking for ice. They were hunting for signs of a molecular form of carbon dioxide that might help reveal clues to the cycling of carbon from slabs into the mantle. The researchers used a variety of techniques, including X-ray diffraction, infrared spectroscopy and X-ray fluorescence, to try to identify the composition of the inclusions within three diamonds, one from China and two from southern Africa.
Instead of carbon dioxide, the team saw a telltale pattern in how some of the X-rays scattered as they passed through the diamond. That pattern pointed to ice-VII. The presence of that extremely high-pressure form of ice was a powerful clue to the depth at which the diamond must have formed. The diamonds also contained separate inclusions of fluids rich in certain salts, such as magnesium calcite and halite, and of carbon-rich fluids.
Water-rich fluids deep in the mantle could be important for driving the circulation that fuels the movements of tectonic plates and the eruptions of volcanoes. The presence of water can make it easier for rocks to melt, Dr. Navon says, by lowering the melting point of hot rock under pressure. Additionally, fluids can help redistribute heat within the mantle.
In addition, some large, heat-producing radioactive elements such as potassium, thorium and uranium don’t fit easily into the rigid crystalline structures of minerals, so scientists prefer melted rock when it’s available. “You just need a little bit of fluid, and they are moving into the melt,” Dr. Navon adds.
The study also raised another mystery. Fluid inclusions within diamonds originating at shallower depths, perhaps 150 to 200 kilometers below the surface, contain a mélange of water, salt, and carbonates. But Dr. Tschauner and his colleagues found that in their deep diamonds, the inclusions are sequestered individually: ice in one inclusion, carbonates in another, salts in yet a third. “We were surprised that they were all separate rather than occurring together,” Dr. Tschauner said.
Any ideas about this mysterious separation in the materials in inclusions?
And, how cool to have remnants of tectonic slabs as inclusions in your jewelry!
Steph
That crystal lattice diagram above resembles a Cat's Cradle, but that's another story. It would take some Catch-22 (or at least 2) to turn Ice-7 into Ice-9. So it goes...
ReplyDeletejan, great observation; I can rel8.
DeleteI do like Ice-9 as a model for Mad Cow disease.
DeleteWow. Fascinating. I did not know Mad Cow disease is known as scrapie.
DeleteIhey're not the same disease, but they're both transmissible spongiform encephalopathies believed caused by prions. Same with chronic wasting disease in deer, elk, and moose, and Creutzfeld-Jacob disease and kuru in humans. Like Ice-9 (or other crystal structures), the "infectious" agent has the same molecular structure as the normal form, but induces the normal form to change just by sidling up to it, more or less. Different from viruses, which take over the genetic machinery of a cell the same way software viruses take over computers, but they're all non-living, non-organisms that challenge classical concepts of infection.
DeleteAh, I see. I'll have to read up on prions. More scary organisms.
Delete"sidling up to it" is a great expression, btw.
DeleteNon-organisms. Viruses and prions aren't living things, at least not by most definitions. They don't metabolize, grow, or autonomously reproduce.
DeleteRe: sidling: Yeah, they're basically just a bad influence.
DeleteA forced separation is very Hubbling. Sorry that's the best I got for this continuation of the Big Bang.
ReplyDeleteVery Hubbling, indeed. Thanks for the article, eco.
DeleteVery sad to read that Stephen Hawking has died
ReplyDeleteAnd on Pi Day, 3/14, in the U.K. . .
DeleteA colleague and friend from Wales, about the same age as Hawking, also has ALS. I worked with him before he had symptoms, when he first started showing symptoms but not diagnosed, and after the disease had taken over most of his body.
DeleteHe was +/- 57 when first diagnosed; like Hawking he was given a short life expectancy, but it's been 19 years now. It's a devastating disease, but he takes it with the aplomb for which the UK (he's 1/2 Welsh, 1/2 British) is famous. He wrote a book, "My Dying is Fun", and continues to write, lecture (with "translator"), and consult on design.
Speaking of British oddities, he is a very modest person, but in 2016 he sent a big blast that Queen Elizabeth had appointed him "to the Most Excellent Order of the British Empire." Not a full knighthood, but those Brits seem to cherish these chivalry awards.
Thanks, eco. I checked out Christopher Day's book description (including UK folks calling ALS Motor Neurone Disease). It's on my reading list!
DeleteBeen on my list too, but I choose to avoid it. I like his architecture books better, especially (selfishly) the ones that talk about our projects!
DeleteThis is not about science, but awwwww.
ReplyDeleteAh, but given their much higher flicker fusion frequency, do dogs get cinema? Let alone animation? I'm sure their human companions enjoyed the experience, but how many paws up or down did the dogs give the film?
Deletejan, those questions could make this about science, surely. Maizie doesn't seem to get what's going on on the tv screen unless it's a dog or wolf howling. Then, she joins in.
DeleteAnd, "dogged determination?" Sometimes, as with a bone to bury. But sometimes? Complete indifference. . .
DeleteI think they also prefer the films of Akita Kurosawa and David Malamute. Also, as I recall dogs don't have great vision at long distance. I suspect those patrons were more interested in other things.
DeleteSF used to have at least 20 art-house independent commercial theaters, the Roxie is one of the few that have survived - it's a great theater for programs. Sadly many of the more beautiful, elaborate theaters have closed.
eco, what an interesting experience to be around all those dog-human duos, though. I am glad the Roxie remains. Thankfully, we still have the Mayan and the Paramount, both built in 1930, here.
DeleteI wonder what they charged for Milk Bones at the snack bar?
DeleteYour Mayan and Paramount both look gorgeous, nicely maintained or more likely restored. Oakland has an incredible Art Deco Paramount Theater, seats over 3000 - every seat filled for Noam Chomsky a few years ago.
One of my clients owns a beautiful mid-century theater in a small town that's been struggling for many years (theater, not town). Rent doesn't even pay the tax bill. He asked me what he could do with it, and while housing is an obvious choice it's really difficult to convert the space, especially with no windows.
My best suggestion was to lease it as a growing facility. We're working on a trade with the city for increased development rights on his adjoining land.
Interesting that grow houses don't always use much natural light. There's a great organization here in Denver that grows food in a food desert for distribution to local Globeville residents. They also swap seeds and teach residents about urban farming. They had the name of The Growhaus before pot became legal in CO. The name has caused some confusion. It's a wonderful community-based group of folks.
DeleteI was thinking of a cash crop grow, but The Growhaus looks like a really nice project. With only 20,000 sf they probably have to control the light to maximize the intense growing for aquaponics and hydroponics. It also looks like they've focused on leafy greens and root vegetables, which generally need less light than, say, tomatoes.
DeleteI was the architect for a similar venture, Urban Adamah here in Berkeley, which has 2.2 acres, a bunch of buildings. It's primarily a teaching garden, but also distributes food through a farm fresh stand each week.
Urban Adamah looks equally intriguing especially with the addition of Jewish traditions.
DeleteHere in CO, "grow house" means pot 99.9% of the time. There's a very large operation on the road out to the Calhan Paint Mines near Peyton, CO..
New post on "Zeptonewtons: Tiny Units of Measure of FORCE" is now up.
ReplyDelete