#ophiolite

[comfycat3]

mmmm serpentinite

[alexanderbayon]

image from here – thank you, victormalonso

[noosphe-re]

Ophiolite

[propalitetz]

first meeting

[artemistorm]

Ehehehe geology infodump time

Here, my friends, is a piece of the mantle of the earth.

This is peridotite with veins of serpentinite. This rock was born in the middle of the ocean in an oceanic ridge like where you find seafloor hydrothermal vents (aka black smokers) (ophiolite sequence babyyy) like these vv

Then the rock joined a mountain chain in the ocean that got smashed into the west coast of the North American continent and in the ensuing chaos, this rock ended up on the top of a mountain.

When I was on a field trip with my geology class and a couple of geo researchers, my teacher found this rock and the geologists were all geeking out over it. We used the rock in a class project and now that it is the end of the term I got to take this rock home!

[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.

[quasarlasar]

NO DINNER FOR CASCADIA TONIGHT

In a story I've been writing with San Andreas, Cascadia appears as this monstrous unstoppable juggernaut, an officer in Gaia's military with countless volcanoes, tsunamis, and faults as his soldiers.

But it's more fun cartoon-wise if Cascadia is depicted as slowly going insane due to not being able to eat subduct new chunks of the Juan de Fuca plate for hundreds of years. (There actually was a 1000-year gap between Cascadia earthquakes at one point...dude just had to go a millennium without dinner lol). Ophiolites are the chunks of mid-ocean ridges that don't get subducted, and are instead plastered onto the continent. If he couldn't subduct them before, it's doubtful he could now, but he's getting desperate...

In any case it's a moot point because this particular ophiolite rock is a piece of the Farallon-Pacific Ridge, aka San Andreas' dead mom. San Andreas of course does not let him have it, slicing through the ground and offsetting the ophiolite and Cascadia away from each other.

If you look closely, San Andreas' eye shines resemble a right-lateral strike slip focal mechanism, and he has a seismogram trace burning from his eye. He's normally a dork, but Cascadia has a tendency to get him really really mad*.

I should note Cascadia's not a selfish glutton. He cares a lot about his volcanoes, and they depend on the magma he creates using the oceanic crust he subducts. So he's literally eating for 20...or how many volcanoes you count as the Cascade range**.

*When the Cascadia subduction zone ruptures, the San Andreas typically does a few decades later from all the stress the former dumps on it.

** Something something an "an army marches on its stomach"...literally in this case since Cascadia eats by running things over and his mouth is on his underside.

[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,

[roccedelparmense]

ARGILLE ROSSE IN VAL CENO 

Affioramento di argille rosse in una bella zona di calanchi presso Serravalle in Val Ceno, salendo sulle colline il paesaggio all’orizzonte presenta tutto un sussegguirsi di versanti calanchivi dai colori caldi, in lontananza, a chiudere la parata,  svetta la mole ofiolitica del monte Prinzera. In questa zona è presente anche un caratteristico “fungo” d’argilla, non comune nelle nostre zone.

Outcrop of red clay rocks in a beautiful area of gullies near Serravalle in Val Ceno. Climbing up the hills the landscape on the horizon presents a succession of warm-colored gully slopes, in the distance, to close the parade, stands the ophiolitic mass of Mount Prinzera . In this area there is also a characteristic clay “mushroom”, not common in parmesan areas.

[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