#ophiolite

[comfycat3]

mmmm serpentinite

[alexanderbayon]

image from here – thank you, victormalonso

[noosphe-re]

Ophiolite

[propalitetz]

first meeting

[iamthepulta]

wait no please explain mineral processing!!!

I gasped in delight at the ask, haha. I love mineral processing.

Mineral processing is the theory of economically getting your desired element out of whatever it naturally comes in. So Li out of spodumene, or Cu out of chalcopyrite. It's usually split into hydrometallurgy and pyrometallurgy (liquid chemistry and melting the fuck out of it, respectively), and often taught as hard rock extraction, but you need it for Every Element, really. So you can also focus on extracting phosphates, or nitrates, or uranium! It's chemistry++~

Personally, I know the most about copper extraction and my focus is on hydrometallurgy/geometallurgy, although pyrometallurgy is near to my heart. Copper is coincidentally a really good example of how the two work because it comes as so many natural minerals. (Further explanations under the cut...)

So for copper minerals! You have a whole slew of oxides and sulfides. They occur in different part of your orebodies under different states of oxidation/sulfidation. Take Chrysocolla, Malachite, Chalcocite, and Chalcopyrite. (Cu-silicate)(an oxide), (Cu-carbonate)(an oxide), (Cu-Sulfide), and (Cu-Fe-Sulfide).

Mines usually use hydrometallurgy for oxides by sticking them in a leach heap and pouring sulfuric acid over the whole thing. The acid selectively picks up the Cu ion from silicates and carbonates, leaving the primary tetrahedra alone. The sulfides can work with this chemistry if the mineral's comfort zone is outside of the current conditions (Chalcocite does leach, but usually leaves a Cu ion in the structure as CuS) but minerals like Chalcopyrite are very poor leachers because the outer rim of ions are ripped away, leaving a somewhat-hypothetical "passive layer" of Fe/S that won't react with the acid. So if you have a mine with a lot of Chalcopyrite, you'll be leaving money on the table unless you do something.

So people use pyrometallurgy! Which is what we've been using since the Bronze Age, really. You crush the rock to micrometer grains, use the hydrophobic properties of sulfur to "float" the sulfides in water, then send all of it to the smelter and melt the shit out of it, while adding particular chemicals and minerals to enhance copper recovery while suppressing sulfides you don't want, like sphalerite and galena.

It's REALLY cool. I'm biased of course, but I absolutely love the whole cycle. xD Being in mineral processing also gets you on the backside of geopolitics because you're the only person who understands how to GET things and WHERE to get them and why it's not as simple as pulling Cu out of the ground.

Feel free to ask questions!! I love processing so much, and mining in general, even though I'm only a master's student.

((And NO STUPID QUESTIONS. The mining industry is a goddamn black box DO NOT feel bad if you don't know what stuff means or formulas, or processes. I swear I learn one new word a week. They also have fifty names for everything too because 50 names are always better than 1. 👍)

[basicgeology]

Under the oceans

Have you ever wondered what exactly lies at the bottom of the ocean? Or, well, under the bottom of the ocean.

The oceanic crust is relatively thin, only between 2 and 10 km at most, with a global average of 7 km. Its density is between 2.8 and 3.2 g/cm^3 and it is theorized that it cannot be older than 250 millions of years, as oceanic ridges continuously form new crust, while the earth "reclaims" parts of it through subduction.

What is more interesting to me though, is what is actually inside of it.

The "Ophiolitic Sequence" is a reoccurring series of rock formations that can be consistently found through the oceanic crust. As opposed to its continental counterpart, the oceanic crust is relatively predictable from what is known, and usually the same formations can be found in the same order from surface to mantle.

Keep in mind that all of these formations aren't always found under the oceanic crust, in some areas some of them may be missing.

This is a very idealized rendition of what the ophiolitic sequence might look like:

From top to bottom we have:

Pelagic sediments: at the deepest parts of the ocean, this means mostly clay sediments and silicates. Rarely you can find limestone sediments in the ocean, especially at significant depths.

Pillow lavas: the most superficial ignenous formations, formed by lava emerging from the oceanic ridges. They care called this way because when the lava emerges, it comes into contact with water - water applies a hydrostatic pressure that forced the lava to solidify in a rounded shape, similar to the one of a pillow.

Basaltic dykes/dikes: dykes are vertical or semi-vertical magmatic intrusions, these are made of basalt which means they are particularly rich in plagioclase feldspar minerals, specifically rich in calcium.

Gabbroic rocks: gabbro is an intrusive rock, it is pretty much the intrusive counterpart to basalt, as it is also rich in high-Ca plagioclase feldspar minerals.

Moho: "Moho" is not a rock formation, but a geologic and chemical discontinuity that separates crust and mantle, the full name of the discontinuity is "Mohorovičić discontinuity", but most people refer to it as just Moho. It's definied by a significant change in the velocity of seismic waves that pass through it.

Peridotites: the top of the mantle is made up mainly by dunites and peridotites, which are both "ultramaphic rocks", as in rocks that are particularly rich in magnesium and iron. dunites are significantly rich in olivine minerals, while the term "peridotite" is used to refer to ultramaphic rocks that have both olivine and pyroxen minerals in relatively similar ratios. (There is honestly an entire essay that could be written about these rocks alone but maybe in a different post, they are my favorite rocks lol).

I hope this post was informative and interesting to read, if you have questions please don't hesitate sending asks to my inbox!

[earthscience-review]

Mineral spotlight on: Smectite♡

Last Thursday, researchers at MIT published findings that suggest this stylish clay mineral plays a significant role in reducing atmospheric CO2.

An ophiolite is a piece of ocean crust that has been moved onto continental crust by tectonic forces. They contain mafic and ultramafic rock (rocks high in magnesium and iron). And they are a suspect consistently on the scene during global cooling.

Previously, scientists had attributed the creation of ice-house climates during the Paleozoic period to the weathering of these ophiolites.

However, geochemical analysis illustrates that cooling happened through the burial of organic carbon, not weathering. This is where smectite (my beloved) comes in.

Turns out, the weathering of mafic rocks creates smectite clays with very high surface areas. Under a microscope, smectite looks like an accordion.

Carbon gets trapped inside these grooves and removed from the atmosphere! That’s another way the tectonic forces of the geosphere influence global climate.

[barstoolblues]

assorted diagrams from my marine geology course

descriptions below the cut:

1. convection of heat in the upper mantle

2. example distribution coefficients of elements graphed as functions of liquid magma/original rock concentrations over fraction of partial melting

3. different ophiolite formation mechanisms

4. classification chart of meteorites

5. diagram of how sonar works

6. graph identifying lithospheric rocks by their % mineral composition

7. depth profile of p-wave velocity through ocean lithosphere and its corresponding layers

8. diagram of earths magnetic field and the direction of magnetic field lines in different hemispheres

9. bathymetric profiles of mid-ocean ridges by type of spreading rate

10. ophiolite model of the rock layers of oceanic lithosphere

11. crust of the juan de fuca ridge color-coded by age found from magnetic field polarity reversals preserved via remnant magnetization. bars of the barcode on the left correspond to periods of normal (colored) polarity and reverse (white) polarity

12. degree of partial melting of the mantle during asthenospheric upwelling beneath mid-ocean ridges

[goinggoats]

earlier this year: I want to go to the Applegate area to find Applegate jade (serpentine) ^_^

earlier this week looking up notable ophiolites: ohhh it makes sense that there's cool serpentine in Applegate since it's (on? by?) the Josephine ophiolite

now after impulsively googling "serpentine wetland": I Need To Go To Josephine County Or I Might Die And If I See The Endemic Species There I Might Also Die

[butchharrydalton]

gabbro, granite, diorite, volcanic breccia, tuff, pumice, andesite, basalt, carbonatite, trachyandesite, trachybasalt, rhyolite, lamproite, kimberlite, microcline, orthoclase, plagioclase, muscovite, biotite, chlorite, ophiolite, grossular garnet, hessonite, uvaroite, feldspar, sanidine, sunstone, moonstone, labradorite, indigo gabbro, tangerine quartz, strawberry quartz, rutilated quartz, tourmalated quartz, rose quartz, amethyst, carnelian, sardonyx, onyx, picture jasper, obsidian, rainbow obsidian, starburst obsidian, snowflake obsidian, cumengite, torbernite, monazite, dolomite, augite, autunite, hornblende, amphibole, lithium include quartz, amphibole quartz, tourmaline, watermelon tourmaline, schorl, ametrine, citrine, lemon quartz, tiffany stone, charoite, beryl, chrysoberyl, alexandrite, emerald, aquamarine, larimar, bixbite, spinel, limestone, dendritic agate, heliodor, morganite, goshenite, enhydro quartz, shale, mudstone, sandstone, siltstone, shale, claystone, conglomerate, marble, graphite, galena, kyanite, lepidolite, stitchtite, mugglestone, helenite, calcite, blue calcite, crazy lage agate, ellensberg blue, zircon, topaz, mystic topaz, cinnabar, realgar, orpiment, cobalto calcite, mangano calcite, pyrite, pyroxene, jadeite, nephrite, chalcopyrite, clinopyroxene, diamond, herkimer diamond, peridot, olivine, peridotite, glaucophane, blueschist, greenschist, greenstone, schist, phyllite, staurolite, phosphophyllite, gneiss, slate, jet, shungite, desert rose, selenite, fluorite, yellow fluorite, rainbow fluorite, fire opal, fire agate, azurite, malachite, cuprite, pink opal, red jasper, ocean jasper, magnetite, sodalite, lapis lazuli, rutile, silver rutile, bismuth, rhodonite, rhodochrosite, pyrope garnet, sulfur, pegmatite, vesuvianite, manganese vesuvianite, turquoise, stony iron meteorite, carbonaceous meteorite, fossiliferous limestone, serpentine, serpentinite, halite, celestite, ruby, sapphire, yellow sapphire, padparadscha sapphire, corundum, blue lace agate, botswana agate, amphibolite, euclase, kunzite, antarcticite, ice, lawsonite, unakite, smoky quartz, sugilite, mossy agate, lodelite, dunite, angel aura quartz, dalmation jasper, bumblebee jasper, honey calcite, tanzanite, zoisite, danburite, apophyllite, ammolite, pietersite,

[daniperil]

Minerals and Rocks

Prehnite in an Ophiolite,

Thin section, XPL

[sagittariusboyfriend]

might be able to convince my boyfriend to go to lizard point as well and have a look at an actual ophiolite, how cool would that be

[six-demon-bag]

ophiolite

Pairing: Ernst Schmidt/Helmut Zemo

Summary: Thanks to an unfortunate rockslide, Zemo ends up captured by his enemy. Nothing in his life can ever be simple, and he goes into heat while in captivity. Somehow, not even that goes as expected.

Rating: Explicit

Tags: Crossover, Alternate Universe - Fantasy, Alpha/Beta/Omega Dynamics, Omega Helmut Zemo, Alpha Ernst Schmidt, Collars, Mating Cycles/In Heat, Mating Bond, Dubious Consent, Knotting, Biting, sad schmidty, but hes a slave so thats why, mean zemo, He gets better, Pining, Anal Sex, Masturbation, Mates, Happy Ending

Word count: 27796

Link: ophiolite

Excerpt:

Zemo turns his head against the ground to look despite himself. There’s a shorter man standing just back and to the side of James, quiet and definitely an alpha by the scent bleeding off of him. “My lovely prize alpha,” James says, watching Zemo’s face as he twirls a delicate leash in one hand. “Don’t you think so?” It takes Zemo a moment to catch up around the heat pheromones and the sheer oddity of that sentence. Alphas are never captives, yet somehow it’s clear James has one. The alpha doesn’t look like one of James’ usual alphas, standing next to James obediently. He’s probably barely even a captive, Zemo thinks with scorn.

[iamthepulta]

I zoomed out of context for a little bit and realized they've basically been mining the Oman Ophiolite for 6000 years. All the soapstone (historically called steatite) and chlorite that's mentioned in Mesopotamian literature. That's absolutely wild. I want Moses to smite the rock and it splits in two. (Because it's talc.) Absolutely glorious hodgepodge of history.

[jcmarchi]

A mineral produced by plate tectonics has a global cooling effect, study finds

New Post has been published on https://thedigitalinsider.com/a-mineral-produced-by-plate-tectonics-has-a-global-cooling-effect-study-finds/

A mineral produced by plate tectonics has a global cooling effect, study finds

MIT geologists have found that a clay mineral on the seafloor, called smectite, has a surprisingly powerful ability to sequester carbon over millions of years.

Under a microscope, a single grain of the clay resembles the folds of an accordion. These folds are known to be effective traps for organic carbon.

Now, the MIT team has shown that the carbon-trapping clays are a product of plate tectonics: When oceanic crust crushes against a continental plate, it can bring rocks to the surface that, over time, can weather into minerals including smectite. Eventually, the clay sediment settles back in the ocean, where the minerals trap bits of dead organisms in their microscopic folds. This keeps the organic carbon from being consumed by microbes and expelled back into the atmosphere as carbon dioxide.

Over millions of years, smectite can have a global effect, helping to cool the entire planet. Through a series of analyses, the researchers showed that smectite was likely produced after several major tectonic events over the last 500 million years. During each tectonic event, the clays trapped enough carbon to cool the Earth and induce the subsequent ice age.

The findings are the first to show that plate tectonics can trigger ice ages through the production of carbon-trapping smectite.

These clays can be found in certain tectonically active regions today, and the scientists believe that smectite continues to sequester carbon, providing a natural, albeit slow-acting, buffer against humans’ climate-warming activities.

“The influence of these unassuming clay minerals has wide-ranging implications for the habitability of planets,” says Joshua Murray, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences. “There may even be a modern application for these clays in offsetting some of the carbon that humanity has placed into the atmosphere.”

Murray and Oliver Jagoutz, professor of geology at MIT, have published their findings today in Nature Geoscience.

A clear and present clay

The new study follows up on the team’s previous work, which showed that each of the Earth’s major ice ages was likely triggered by a tectonic event in the tropics. The researchers found that each of these tectonic events exposed ocean rocks called ophiolites to the atmosphere. They put forth the idea that, when a tectonic collision occurs in a tropical region, ophiolites can undergo certain weathering effects, such as exposure to wind, rain, and chemical interactions, that transform the rocks into various minerals, including clays.

“Those clay minerals, depending on the kinds you create, influence the climate in different ways,” Murray explains.

At the time, it was unclear which minerals could come out of this weathering effect, and whether and how these minerals could directly contribute to cooling the planet. So, while it appeared there was a link between plate tectonics and ice ages, the exact mechanism by which one could trigger the other was still in question.

With the new study, the team looked to see whether their proposed tectonic tropical weathering process would produce carbon-trapping minerals, and in quantities that would be sufficient to trigger a global ice age.

The team first looked through the geologic literature and compiled data on the ways in which major magmatic minerals weather over time, and on the types of clay minerals this weathering can produce. They then worked these measurements into a weathering simulation of different rock types that are known to be exposed in tectonic collisions.

“Then we look at what happens to these rock types when they break down due to weathering and the influence of a tropical environment, and what minerals form as a result,” Jagoutz says.

Next, they plugged each weathered, “end-product” mineral into a simulation of the Earth’s carbon cycle to see what effect a given mineral might have, either in interacting with organic carbon, such as bits of dead organisms, or with inorganic, in the form of carbon dioxide in the atmosphere.

From these analyses, one mineral had a clear presence and effect: smectite. Not only was the clay a naturally weathered product of tropical tectonics, it was also highly effective at trapping organic carbon. In theory, smectite seemed like a solid connection between tectonics and ice ages.

But were enough of the clays actually present to trigger the previous four ice ages? Ideally, researchers should confirm this by finding smectite in ancient rock layers dating back to each global cooling period.

“Unfortunately, as clays are buried by other sediments, they get cooked a bit, so we can’t measure them directly,” Murray says. “But we can look for their fingerprints.”

A slow build

The team reasoned that, as smectites are a product of ophiolites, these ocean rocks also bear characteristic elements such as nickel and chromium, which would be preserved in ancient sediments. If smectites were present in the past, nickel and chromium should be as well.

To test this idea, the team looked through a database containing thousands of oceanic sedimentary rocks that were deposited over the last 500 million years. Over this time period, the Earth experienced four separate ice ages. Looking at rocks around each of these periods, the researchers observed large spikes of nickel and chromium, and inferred from this that smectite must also have been present.

By their estimates, the clay mineral could have increased the preservation of organic carbon by less than one-tenth of a percent. In absolute terms, this is a miniscule amount. But over millions of years, they calculated that the clay’s accumulated, sequestered carbon was enough to trigger each of the four major ice ages.

“We found that you really don’t need much of this material to have a huge effect on the climate,” Jagoutz says.

“These clays also have probably contributed some of the Earth’s cooling in the last 3 to 5 million years, before humans got involved,” Murray adds. “In the absence of humans, these clays are probably making a difference to the climate. It’s just such a slow process.”

“Jagoutz and Murray’s work is a nice demonstration of how important it is to consider all biotic and physical components of the global carbon cycle,” says Lee Kump, a professor of geosciences at Penn State University, who was not involved with the study. “Feedbacks among all these components control atmospheric greenhouse gas concentrations on all time scales, from the annual rise and fall of atmospheric carbon dioxide levels to the swings from icehouse to greenhouse over millions of years.”

Could smectites be harnessed intentionally to further bring down the world’s carbon emissions? Murray sees some potential, for instance to shore up carbon reservoirs such as regions of permafrost. Warming temperatures are predicted to melt permafrost and expose long-buried organic carbon. If smectites could be applied to these regions, the clays could prevent this exposed carbon from escaping into and further warming the atmosphere.

“If you want to understand how nature works, you have to understand it on the mineral and grain scale,” Jagoutz says. “And this is also the way forward for us to find solutions for this climatic catastrophe. If you study these natural processes, there’s a good chance you will stumble on something that will be actually useful.”

This research was funded, in part, by the National Science Foundation.