The Geology of Uranium
Dr. Jesse Reimink: [00:00:00]
Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.
[00:00:30]
Dr. Jesse Reimink: [00:01:00] Chris. What's up man?
Chris Bolhuis: Uh, well a lot. I was gonna say not a lot, but there's a lot that's going on in my life right now,
Dr. Jesse Reimink: Yeah, you're in your, like your, your old childhood room right now. Recording. The scenery in the background has changed for you. What's going on?
Chris Bolhuis: Um, my house is getting work done on it, and so I cannot record. We had to record, you know, we just, this is what we had to do. I have the day off today, so we have a big day ahead of us, and my house is not suitable for recording right [00:01:30] now.
And so I am at my mom and dad's
Dr. Jesse Reimink: Your recording man. Cave booth downstairs is under construction.
Chris Bolhuis: it is. It'll be done today though, so that's exciting. this is the last day of it, so yeah, I'm in my old bedroom when I was at my childhood bedroom
and it's, it's very, it's interesting. Yeah.
Dr. Jesse Reimink: Some yellow shag carpet on the ground over there. What? What's going on? What do we got on the ground?
Chris Bolhuis: no, it's, it's red carpeting actually. It's the, it's the same carpeting that was there when I was a [00:02:00] kid.
Dr. Jesse Reimink: Amazing. Amazing. Well, it's a bit of a throwback for you then. This is fun.
Chris Bolhuis: it is. It is. So, Jesse, what do we have going on today? What are we gonna talk about today?
Dr. Jesse Reimink: Well, this is the next one in our line of the Geology of Fill in an Element, and this is the Geology of Uranium, which I put this. Together. I think I pitched this to you and Well, we've talked a decent amount about uranium in the past. We've had our ancient nuclear reactors, [00:02:30] ancient natural nuclear reactors episode.
We've talked about endocrinology quite a bit, so We've kind of beat around the bush, I guess, about uranium and how useful it is and like details about uranium, but we haven't really hit the Geology of uranium, like how it behaves out there in the, the systems that we talk about in Geology.
So I think that's kind of what we're gonna cover, right, Chris?
Chris Bolhuis: Uh, yes, we, we are. but, uh, I'm gonna say as just a, a forewarning that the chemistry of uranium, as we started digging into this and getting ready [00:03:00] for this episode, brought me back and it actually brought back some nightmares of, of college chemistry classes.
Dr. Jesse Reimink: Yes.
It
Chris Bolhuis: You probably felt so at home.
You know, you're, you're this nerdy little geochemist, you know, you, this is the stuff you really, really get into. So this took a bit of selling on your part to pitch this to me. I'm still
not a hundred percent sold on this. Uh, I'm just, I'm gonna tell you because, uh, you know, getting into the chemistry of uranium, I'm gonna tell you, [00:03:30] to be quite honest, this brought back some, some memories of college that are not all that great. I'm not.
Dr. Jesse Reimink: College chemistry. Chemistry 1 0 1 or Chemistry 1 0 2. Those like really kind of hard chemistry classes. Oh, man. Yeah.
Chris Bolhuis: I know I, you know, I'm gonna be honest, like, in thinking about this, I remember vividly sitting in
on chemistry. classes and, and just thinking, all right, I just have to do this because this, if I get through
this, it enables me to chase the dream of [00:04:00] Geology for me.
But I never really understood the appeal of chemistry.
Dr. Jesse Reimink: So that's, I, I, I was the exact
same way, Chris. And then I think chemistry is like one of these things that's like math. I, it never really. Made sense to me. Like I was kind of bored by it, like doing these proofs and stuff like that. It's like, okay, why do I care? Okay, took some recipe in the chemistry lab and I made a green solution blue.
Like, great, What the
heck? But then when I was in
grad school and I
realized how amazing chemistry is and how useful it is for Geology,
that's when I [00:04:30] was like all in on geochemistry. Like,
oh man, this is awesome. So that's what we're gonna kind of try and do
today is frame it that way.
Chris Bolhuis: Let me interrupt you a second, Jesse, because that is such a good point. Chemistry in context is amazing. Chemistry by itself
is not amazing. It's just not amazing. I, I apologize if I'm offending anybody out there that just really, really loves chemistry. But chemistry needs to have context. so geochemistry is amazing.
I, and [00:05:00] biochemistry too. It has amazing application, but it's not taught that way hardly ever. it's, it's just out of context and it stands alone, and then it's
like, ah,
Dr. Jesse Reimink: Yeah. What's the point? Yeah.
You're, you're learning about the hammer. You're, you're, you're learning like how a hammer is constructed, not like how to use the hammer. right. It's way more interesting to learn how to use the hammer.
So,
uranium,
Chris Bolhuis: so basically let me give a summary as to where we're gonna
go
here a little bit. We're gonna talk about uranium as a critical mineral, and there's a little bit of a discussion [00:05:30] around
that.
we're gonna talk then about like, well, why do we care what, you
know, why do we care so much about uranium?
And then finally, cuz this is a Geology podcast, we're gonna get into the geochemistry of uranium.
Dr. Jesse Reimink: that's right. And so let's start out
there
cuz I think the interesting part. About the
critical
minerals and critical minerals are
sort sort of a government defined thing. That critical means they're
critical to
our infrastructure or there's
some,
Chris Bolhuis: If you go back to our episode with Nadal Nassar, the critical mineral [00:06:00] person, for the U S G S,
We did a whole episode on this and it's, amazing.
Dr. Jesse Reimink: it's it's really, really cool. And so uranium is an interesting one. It was sort of mandated by the Trump administration in the US to be on the list as a critical mineral that was then removed under Biden by the US Geological Survey under the argument that uranium is quote unquote a fuel mineral.
And so therefore no fuel minerals can be on the critical minerals list. And you know, This is
a [00:06:30] hot button topic. I would
say, Canada lists uranium as a critical mineral. And to me, I, Chris, I think we've talked a little bit about nuclear power before. I think people know, I'm a Sort of a proponent of. it, but that's not a a, that's, that's like people find that
Chris Bolhuis: Sort of. Really is that that's that's where you're gonna go with that. You're sort of a proponent of it.
You are in love with
nuclear power
Dr. Jesse Reimink: Yeah.
Chris Bolhuis: You give you half a chance to talk
about nuclear energy and, and there goes your day. It's, it's just time.
You're never gonna get [00:07:00] back. It's amazing to me that we've politicized an
element. You know, um, because really if you think about this, it comes down to, I at least, I think you and I agree on this, it comes down
to nuclear power, and is that considered then a green energy? and that's why it's been politicized. at least that's the only reason I can make out of this whole discussion or debate about uranium.
It's kind of a hot button
Dr. Jesse Reimink: Completely agree with you on that one. And so whether it's a critical mineral or not, the United States Geological Survey and [00:07:30] many other geological surveys have big research programs dedicated to this to understanding uranium, finding new sources, and we're gonna talk about kind of why we care about that.
So, what's the main
reason we should care about uranium? I guess there's the science reasons, which we've talked about endocrinology, like I use uranium every day in my research lab. but there's societal reasons we should care as well.
Chris Bolhuis: Yeah, we already touched on it, but it comes down to nuclear reactors and
nuclear reactors rely upon uranium 2 [00:08:00] 35. And, do you want to talk a little bit about the chain reaction that goes on inside? I think we should just touch on it as a review purpose. I,
Dr. Jesse Reimink: Why don't, why don't you take it away, Chris? Cuz I think you have a really good
Chris Bolhuis: Um, an, do I have an analogy?
Dr. Jesse Reimink: you're the analogy king.
Chris Bolhuis: I don't know What, you're talking about. what analogy do I use with
this? basically, Uranium 2 35 is the fissionable flavor, if you will, of uranium. And so what happens is you [00:08:30] take a neutron moving very, very, very fast. It's gotta be moving at the right speed, and it slams into the nucleus of a uranium 2 35 atom, it quickly absorbs that neutron.
And so it becomes U 2 36 for just a really brief instant in time. But it's very, very unstable. Then U 2 36, it doesn't like that, and so it flies apart into two smaller isotopes. But the thing is that you get three more neutrons that come off. Well, actually [00:09:00] you get two additional neutrons. You have the one that got absorbed by the uranium 2 35, and then two more neutrons come off at that speed.
And those three neutrons, if they hit uranium 2 35, The process repeats itself. So one neutron led to three, three leads to nine, nine lead to 27, and so on, and so on and so on. That's the chain reaction of Uranium 2 35 inside of a nuclear reactor.
Dr. Jesse Reimink: Chris, I have a, real quick story about this [00:09:30] cuz I just took at a visitor,
one of my PhD supervisors was actually visiting Penn State and I took him and my research group, all the students, we went to the research reactor at Penn State. So there's a nuclear reactor that's a research reactor at Penn State.
Um, and so we went and
Chris Bolhuis: Wow, that's amazing. First of all, hold on. I did not know that. That is unbelievable.
Dr. Jesse Reimink: gotta come, when you come to visit Penn State or visit us here in Pennsylvania, we'll definitely go. they're totally open. I've gone on two tours now with these people. [00:10:00] It's unbelievable. So we walked in and you, you can like stand in the room with the pool. You're just in the room of the pool.
You're looking down. You could touch the water if you want to,
I mean, they don't want you to, but like, it wouldn't be dangerous, but you're looking down at the reactor down there, like 20 feet down in this big pool of water. and you can see it glowing blue like it's on. And so we're obviously amazed by this.
We're going over. And so
Chris Bolhuis: Okay. Why is it, why is it glowing blue? What does that
Dr. Jesse Reimink: There's, a radiation. Uh, it has something to do with the physics of [00:10:30] light traveling through water. the neutrons are traveling faster than the speed of light through water, and so it gives off. So I, I don't exactly understand the physics of it, but it has this, this kind of bluish glow when it's in the water.
but the story is we go back into the control booth and there's obviously an undergrad who's, like a trainee, an undergrad trainee who's working the reactor, and there's another guy there who's the main. The main controller of the reactor at this time. And so we're talking, asking a bunch of questions and he goes, the guy, the control booth guy says, well, [00:11:00] do you guys wanna see a pulse?
And so all of us are like, well, yeah, that sounds fun. What's a pulse? And he says, well, it's a, we, we'll do a $2 pulse for you guys. And we're like, what is a $2 pulse? And it turns out that a $2 pulse is, You can turn up the reactor, basically make it go critical where it would run away if it's the design of the reactor.
These research reactors can't have a runaway reaction, but it's kind of pushing it in that direction. And so we looked at the board and they have a count of like since 1950,
how many pulses they've [00:11:30] done. And this was like number, you know, 8,500 that they've done. But just did a pulse. And so we went out in the pool, looked down, and he said, okay, we're gonna pulse the reactor, which means we're gonna pull the control rods up really quickly, and then the reactor
will, and let it go, let it crank.
So there's just neutrons
everywhere. And he was,
Chris Bolhuis: Hold on. Can I just explain a second real quick what you
just said?
Just so that
everybody can follow the
control Rods
absorb the neutrons and, so this depends upon how much of the reaction you want to [00:12:00] go, because we use the heat from this, you know, splitting atoms to boil water and that turns the turbines and all that.
Right? And so the control rods control the neutrons. Because the neutrons do the splitting, and so if we need less power, we put more control rods in, they absorb neutrons, take 'em outta commission. If we need more heat, we take some of the control rods out and let the reaction go a little bit. What you're saying is let's take the control rods out and let it rip.
Dr. Jesse Reimink: so basically what they,
did is they just had this pulse of air that blasted a control rod [00:12:30] up out, and these are like gravity ones. So then it kind of sits up high out of the reaction So we go, everybody stands around the pool and he is like, turns the lights off. He says, okay, we're gonna count.
He's gonna count down 5, 4, 3, 2, 1. When he hits two, do not blink cuz you'll miss it. And so we're out there, we're like, my PhD supervisor turns to me and he goes, so this might be the dumbest thing I've ever done standing in the pool while this reactor's
gonna go Super critical. Yeah. Oh right. And it's like, well this is a way to go.
impossible for this to melt [00:13:00] down. Because of the design. So anyway, this thing pulsed such a bright, vibrant blue. This bright,
blue fa flash, and it was so, so cool. So anyway, uh, it's a long-winded way to say it's an amazing reaction that happens. and we're using uranium.
These rods are all uranium.
Chris Bolhuis: That's amazing. okay, so a question then. How long did it take to remove the control rods?
How, like he
counted down from
five, how long does it take to remove them?
Dr. Jesse Reimink: So they use a high pressure gas to
just blast it up so instantaneously, And, this
Chris Bolhuis: Okay, so [00:13:30] they're just instantaneously.
Yeah. And, so what you're saying then is the chain reaction went that fast.
Is that what you're
saying? That's the
Dr. Jesse Reimink: Instantaneously, yep.
Think about nuclear bomb type thing. You know, it,
Chris Bolhuis: Oh my gosh.
Dr. Jesse Reimink: goes instantaneously.
Chris Bolhuis: That's a really, really cool story, um, that I'm, I'm so glad that you brought that in.
I had no idea. I've always wondered
this, how long it takes for the chain reaction to go. Does it kind of like, is
this this kind of crescendo and you're saying,
no, it's
not. This happens really, [00:14:00] really
fast. That is unbelievable. So then he instantly takes 'em out and then he puts 'em right back
in then,
Dr. Jesse Reimink: no. This is the, the design of the reactor is such that when the reactor gets hot, it self regulates. So it has, it's a, I think it's a zirconium hydride, uranium. The rods are zirconium, hydrogen and uranium, and the hydrogen heats up and it, starts to.
it moderates the neutrons so when it gets hot, the neutrons get absorbed more and
they stop fis visioning.
so basically this thing pulses really high in [00:14:30] energy
and then it, It automatically brings itself back down. So this would not be good for a power reactor, or this would not be a good, for instance, bomb
design because it
self regulates.
Chris Bolhuis: It has nothing to do with the critical mass of the uranium then that's in the reactor,
or is that. why It won't go out of control.
Dr. Jesse Reimink: we're in the part where nuclear reactor physics are beyond me. I don't know exactly how much it has to do, but this particular design of the reactor with, I don't remember how
many control rods or how many rods they have, and they have five control rods, uh, amongst I think
60 [00:15:00] fuel rods.
But it's amazing. And you can see these,
this is
uranium, this is
uranium plus zirconium plus hydrogen on these rods. And that, that's what it's
Chris Bolhuis: Oh my gosh.
Okay,
so if I was not awake before this discussion, I am awake now.
Dr. Jesse Reimink: it's basically like you had your third cup of coffee over there.
Chris Bolhuis: I am so
excited. This
Dr. Jesse Reimink: Well, when you come, when you come, we're gonna do a tour and maybe we'll get
him to do a $2 pulse for us.
Chris Bolhuis: Okay. Well, what's a $5 pulse? Is that
possible?
Dr. Jesse Reimink: So the $2 is, um, another [00:15:30] interesting story is because back during the Manhattan Project, they used all these very common words to mean fancy physics things. Cuz if somebody intercepted, you know, a piece of paper where they're writing things on it, they wanted the word to be, to seem like a invoice chart, like a financial sheet.
So they use dollar means the number of. Critical, super critical neutrons. So it's like the number of excess neutrons in the system that create this super criticality. And so $2 means there's two more than [00:16:00] normal. So you described it as like there's like excess neutrons above the normal reaction like so.
Anyway, above the critical point. So critical is just self-sustaining. This
is super
critical. So there's two more neutrons per fission than the super critical version I think I explained that right. We'd have to go and talk to the nuclear physicist to
Chris Bolhuis: Unbelievable.
I.
Dr. Jesse Reimink: definition
Chris Bolhuis: That's a very cool story. I think pretty much everybody here learned something then I That's, that's amazing.
Dr. Jesse Reimink: So Chris, we're gonna [00:16:30] go do a tour when you come to Penn State, but this is how nuclear reactors work and nuclear power reactors globally produce about 400 gigawatts electric, and, and the reason it's called gigawatts electric is because they produce more energy. The
nuclear reactor is
producing more energy, but the electric power out of that is 400
gigawatts.
and they require.
67,000 tons of uranium per year to keep those operational. So
that's a lot of uranium.
Chris Bolhuis: Is that a lot of electricity? But we gotta put [00:17:00] that maybe in perspective
400
gigawatts.
Dr. Jesse Reimink: Yeah, that's a good, uh, that's a good question, Chris. So, one gigawatt of electricity is equivalent to 333 wind turbines and a hundred million LEDs.
And there's some funny, there's some funny like ways you could do this. 2000 Corvettes roughly 1.3 million horses. You know, there's some, all these funny little things about how to
define a gigawatt. so yeah, that's, [00:17:30] that's one
Chris Bolhuis: many, how many light bulbs did you say
that's,
Dr. Jesse Reimink: a hundred million LEDs
Chris Bolhuis: and
that's one
gigawatt. Okay.
Alright. That's amazing. Okay. So you have in here this, thing about small modular reactors. Can you talk about
that a second? Real quick? What is a
small modular reactor and why are they important maybe in bringing us down to lower carbon or
Dr. Jesse Reimink: Yeah, this, the argument goes that big nuclear reactors, like the [00:18:00] ones, there's a power nuclear reactor near you in Michigan. There's one near me. I live really close to three mile Island, which is no longer a a nuclear reactor. They got turned off in 2015. But these big nuclear reactors, they're like custom built.
Each one's different. Each site is different. They're huge. There's all sorts of regulations, obviously. Each one is kind of a custom job. The idea with the small modular ones is you make them smaller and then you can have them be kind of mass produced and you can stack them together. So you could have one small [00:18:30] modular reactor at some remote, you know, mine site, or you can have 15 at like a production scale energy factory.
So that's the idea is to sort of make them. Plug and play a little bit more. And there's a bunch of new companies kind of focusing on those things. That's sort of a, a rough summary, many of them rely on uranium. many of the designs still rely on uranium. And 43% of the world's uranium is currently mined in Kazaki Stan.
The rest [00:19:00] comes from a bunch of different countries. Canada's a big producer of this. There's a single mine in Canada that produces 10% of the world's uranium. It's called Cigar Lake. And we'll talk just briefly about that. but there's a few countries that dominate the production of uranium.
Hence this sort of discussion about criticality. Is it a critical mineral or not? Cuz anytime the supply chain is like sensitive to disturbance, that
becomes a potentially for an
important mineral to have resources.
Chris Bolhuis: All right, well let's move into Jesse talking about how rare. Uranium [00:19:30] is in the crust, like, you know, where do we find this? let's move into that a second. So it is not very abundant in the crust, right? And we can establish that we're talking about like 2.8 parts per million. So that means if you take a, you know, a million elements in the Earth's crust, only 2.8 of them are gonna be uranium madams. and and so that's that's not very abundant that obviously then, talking about how much uranium is consumed, we talked about that earlier with the whole 400 [00:20:00] gigawatts of of power produced, and it takes 67,000 plus tons of uranium per year, but it's in small concentrations in the yours crust.
That's obviously then a potential
problem.
Dr. Jesse Reimink: That's right. And your, you know, your average Granite has about that much. The continental crust is roughly Granite in composition, so it has, you know, three to five parts per million. And if you have a little Geiger counter, I've done this in some public talks, you know, you can hold your Geiger counter next to a Granite and it'll detect decay.
[00:20:30] That's, most of it's coming from uranium, a little bit from potassium maybe.
but a lot of that's uranium. there is background radiation there coming from uranium or What, we call, or o r e is, higher
Chris Bolhuis: what
what he is
talking about an an or is a
rock or a mineral that has enough
of an element so that we can make money by mining for that element
out of it.
Dr. Jesse Reimink: Exactly, exactly. So Chris, what are, what are some of the grades of, or when we talk about uranium, like what are the concentrations [00:21:00] relative to background stuff?
Chris Bolhuis: Okay. so a low grade ore, one of the words, one that's not, you know, it's not the most desirable thing, but it's still something that we can make money on. We're talking
about it has about,
0.1% uranium in it. In other words, about a thousand parts per million. Whereas a high grade ore this highly desirable, you know, make a lot of money off this stuff we're talking about 2% concentration, which is about 20,000 parts per million now.
I want to ask you, how does [00:21:30] it get to be that concentrated geologically? Can we, can we talk about
that or is that,
am I jumping the gun?
Dr. Jesse Reimink: so Chris, before we get to that, I think w we should unfortunately go back to high school chemistry or college chemistry and introduce just two terms.
So if, if you'll allow me, let's just talk about two terms. The first one is oxidation
state,
So that's an important one. We're gonna talk about that in solubility. That's another term. is that okay, Chris? Is that, are we bringing back flashbacks from college chemistry
here with these
two?
Chris Bolhuis: It doesn't make me feel good. [00:22:00] It really doesn't. I have very interesting emotions going on right now. I mean, at first you
brought me up really high by talking about this reactor at Penn State,
and now we're gonna go down to a really low
valley
Dr. Jesse Reimink: I know,
I
Chris Bolhuis: and you know, gaining and losing electrons.
Let's start with, let's talk about the oxidation states and the amount of electrons that uranium is capable of losing. Cuz this is actually very impressive and
amazing
cuz you
don't see this a lot in
basic
Dr. Jesse Reimink: No, that's right. So oxidation state, [00:22:30] you know, we've talked about cat ions and anions before. C ions are positive and
anions are negative, like we've talked
about this stuff before.
Positive,
positive.
I always say it positive.
It's positive
Chris Bolhuis: Yes,
Dr. Jesse Reimink: like a cat. Oh man. So uranium ends up being a cat. Uranium can have oxidation state just means what is the charge of the ion?
Is it negative or positive? And if it's negative, how negative? If it's positive, how positive? Uranium can have two [00:23:00] oxidation states, and that means it can have two different charges. One is four
plus and one is six plus, and that's really important
for the concentration. How does uranium get concentrated?
In deposits in the Geology of uranium. So four plus
and six plus are the two oxidation states we're gonna be dealing with here.
Chris Bolhuis: Okay. you might be sitting there
thinking, wait a second. We talk about in basic chemistry classes
like Iron for instance, iron oxidizes, it goes iron
two plus,
and then it goes iron three plus, it's very common [00:23:30] for elements to lose two electrons, one electron, or maybe even three electrons. But we're talking about losing six electrons and one of the oxidation states for uranium, and that that's a little bit mind blowing to be honest.
Like for me it is anyway, but. You have to remember where is uranium on the periodic table? We're talking about atomic number 92. So it has 92 protons, which means a neutral atom of uranium has 92 electrons.
You're talking about then many, many, many energy levels that are involved here [00:24:00] where the electrons reside.
And so because this is such a heavy element and it's such a big atom, it's capable of losing. More electrons than normal elements that
Dr. Jesse Reimink: Yes, and Chris.
Chris Bolhuis: common anyway.
Dr. Jesse Reimink: We were talking about this before, like how does it get to six plus? You know, that's interesting. And so we looked up the electron orbital shell configuration. If you go back to high school chemistry, remember that there's like different orbital shells that the electrons can be in, like PE and S and all these ones.[00:24:30]
And the electron configuration is crazy for uranium because there are so many shells. There's 92 electrons out there in this huge cloud. So no wonder it can lose a couple off the edges and not. be an unhappy atom. so
that's the first thing. Uranium can be six plus or four plus. Now soluble is another thing, another term that we should just quickly define soluble means, will a fluid pick it up is really kind of what it means.
Will the thing
if it's soluble.
Chris Bolhuis: [00:25:00] in a fluid
Dr. Jesse Reimink: If it's soluble, it will
dissolve. If it's insoluble, it will not dissolve. Or if it's soluble, it'll exist in the fluid. If it's insoluble, it will importantly
precipitate out of the fluid. It'll kind of become a crystal out of the fluid. and so you can work this
both ways.
Like fluids? Yeah. Let me just, so fluid can just pick this up, and fluid can drop stuff depending on the soluble or insoluble.
Chris Bolhuis: But the bottom line is, is that uranium is very soluble that's why this is important [00:25:30] and that's why it has the ability to concentrate in certain geologic
settings.
Dr. Jesse Reimink: That's the key point. This oxidation state, there's a difference in solubility between the two. Uranium six plus is very soluble in water, in all sorts of fluids. The water based fluids, uranium four
Plus is not at all soluble, so six plus happy in water, four plus unhappy in water, and that's
really the key to all of uranium concentration in oars.
Chris Bolhuis: All right, Jesse. [00:26:00] Well then talking about solubility
we need to, I think, talk about where this then happens in a geoscience or a Geology setting.
Where is uranium gonna concentrate in a fluid
C Can you hit that real
quick?
Dr. Jesse Reimink: So, yeah, Chris, let's break that up into two parts here. there's one which is kind of plate tectonic scale stuff where is this happening on earth? Sort of in a, in a general sense. And then there's one that we can talk about or formation, which is kind of a more local specific region or a local [00:26:30] specific process.
The first one is subduction zones. So there is, as we've talked about before, you know when an oceanic plate goes down, it has a lot of water. Bound up in the minerals in the oceanic crust, and that water is the key to producing these beautiful volcanoes along seduction zones. The Mount Shasta that you love is produced by fluid coming off of the downgoing slab.
That fluid goes into the mantle and melts the mantle now. I'll point everybody to our
Camp Geo [00:27:00] conversational textbook, cuz we have a whole chapter on plate tectonics and a bunch of episodes on this process and some really cool visuals that explain exactly what's going on here. So first link in your show notes, go to that if you wanna learn more about this process.
Chris Bolhuis: That's right. But the gist
of it is basically as subduction happens, water gets rung out
of this
subducting slab it, gets driven off, it rises
up into the mantle.
Very hot mantle there, but it's, it's not melted, but the addition of hot water, this kind of salty brine hot water.[00:27:30] Stimulates melting. It lowers the melting point of the minerals.
so we brought myself back into comfort zone.
Chris,
here,
this is
what we have now. Okay.
We left the chemistry a little bit. Now we're talking about subduction and plate tectonics and mount. You even brought in Mount Shasta. So we're, I'm back to being
happy, but
Dr. Jesse Reimink: Okay. that's,
good. Can,
Chris Bolhuis: what's going
on.
Dr. Jesse Reimink: I don't know if this will make you happier or not Chris, but the uranium in Mount Shasta because it's this process, because there's fluid involved in the production [00:28:00] of the lavas that come out of Ma Shasta. There's more uranium in there than there would be otherwise if there was no fluid.
So if you compare, uh, we don't really talk about absolute concentrations of uranium, but if you compare, for instance, uranium to another element that's kind of similar, uranium to thorium or uranium to Utopia or rare earth element or something. there'll be more uranium in the Shasta volcanic rocks than there will be in, for instance, the Pikes Peak batholith that we collected.
We collected a bunch of [00:28:30] rocks around Pikes Peak and we hiked around Pikes Peak in Colorado because
that's not a subduction zone magma. So anytime there's fluid involved in the production of magma, uranium will be enriched, and therefore, uranium's like a great tracer of subduction zones
back in time.
Chris Bolhuis: Okay, good. So we brought that back
to plate tectonics and subduction zones and how you can concentrate uranium. What
about now these oars, how
does it get
super concentrated? is this a good transition
then
Dr. Jesse Reimink: Uh, yeah, I think that's, and this is [00:29:00] kind of the end stage or the last thing. We're kind of bringing it all together in this episode. So we talked about uranium six plus being carried by fluids really easily,
but we also talked about the fact that. you can have anything in a fluid and it can drop out.
It can become insoluble. And I think. Chris, back to the high school chemistry or the college chemistry classes, you probably did this. You like supersaturated a liquid with sugar or something and then cool it down, drop a crystal in it and it, it all just
starts to crystallize, [00:29:30] right? that sugar or salt or whatever crystal you're making becomes insoluble and starts to crystallize out.
That's the process that typically generates uranium oars
Chris Bolhuis: Okay, hold on, let me interrupt
you a second. So this is how Pegmatites form. Okay. Super saturated, you know, watery
solution. Okay. And these crystals get really big, really fast. Uh, we did an earlier episode on Pegmatites.
I want to ask you then. So uranium [00:30:00] concentrated or deposits, so. Are they associated with Pegmatites then?
Dr. Jesse Reimink: No, not necessarily. And here's the thing Think about like where fluids are in the croston. We've talked about this before, fluids are kind of everywhere. You can have magmatic fluids that are coming off of magmas that form pegmatites, but there's like water circulating around through all of the sedimentary rocks underneath your feet.
In Michigan, underneath my feet in Pennsylvania. So there's fluids everywhere and fluids will go around and they'll [00:30:30] scavenge uranium. If there's uranium four plus in a rock, the fluid will hit out, it'll change it to a six plus oxidation state. It'll pick it up in the water and carry it away. So these fluids, That are flowing through rocks, have uranium in them.
In the six plus oxidation state, if that fluid changes, composition becomes more quote unquote, reducing meaning, it'll add more electrons to the elements, the ions in the solution, then uranium can go from six plus to four plus, and then it's [00:31:00] insoluble. It wants to be out of the fluid as fast as possible.
And so the way this happens is, The way I think about this at least, is we often think of, what are called redox barriers or changes in the oxidation state. So like a barrier that changes the chemistry of the fluid. So you've got this fluid flowing through a sandstone, it's super happy, it's oxidizing, it's picking up your uranium along the way.
That fluid then flows into something like a shale with a ton of organic matter, [00:31:30] and that organic matter is really reducing the decomposition of that.
Creates this reducing area all that fluid will continue flowing through there, but the uranium hits it and goes to four plus and gets dumped out of solution.
And there, this is kind of a conveyor
belt of this happening where over millions of years, you'll have fluids flowing through there, dropping off uranium, dropping off uranium, dropping off uranium, and it gets concentrated over time. And, and that's often how this happens.
Chris Bolhuis: so real quick then,
and we will [00:32:00] wrap
up this episode. Is it associated with shale, then you use
shale as an example of a reducing environment. Is uranium associated with that
Dr. Jesse Reimink: Yeah, it can be in the southwestern United States. So there's a bunch of uranium deposits. We were just talking about meandering streams. the last couple episodes here, Chris, and in a sediment deposit that used to be a meandering stream, you'll have like places where there's a, a an old stream bed channel that has a bunch of organic material and then above it you'll have a stream channel that has a bunch of sand on it so you can get these really [00:32:30] complicated patterns of sediment deposition in an ancient meandering stream environment. And that's a place where you can get. A pile of organic matter that's not a shale, it's just like somewhere the stream dropped off a bunch of sticks and leaves.
And that can be a place where this uranium gets
super concentrated. It can
also be magnetic gases can be reducing. So if sandstone fluid is flowing through and it hits an area where there's like a, a magma chamber, it can
dump off a
bunch of uranium as well there.
Chris Bolhuis: we did an [00:33:00] earlier episode on radon in your house.
In your homes, okay. And radon comes from the
decay of uranium. It's one of the steps along the way, which is how it can accumulate.
So is your house is built in clay, which is, it's like shale. Okay. It's a red, it's gotta be a reducing then kind of material.
will uranium concentrate then in those kinds of areas? And then does that make homes more susceptible? Is that why the Geology of,
Dr. Jesse Reimink: I think I know what you're asking. Yeah. And, and, and [00:33:30] it's kind of yes and no. I suppose uranium is going to be concentrated somewhere and then like the raddon is, is a more of a modern. Process like, you know, radon will happen over years, whereas this uranium concentration process happens over a much, much longer timeframe.
So hundreds of thousands of years. And this can also happen with unconformities. Chris, we have talked about unconformities before, where you've got, ancient old basement nices, metamorphic rocks, and then right on top of it, [00:34:00] sediments that barrier can be a. Oxidizing above it, reducing below it, the fluids.
The rock types can be very different above it. The chemistry, so that fluids can flow through the sediment on top. They hit that unconformity and all of a sudden all the uranium
gets dumped out. And this is one of them. The cigar lake deposit in Canada, where I
said 10% of the world's uranium is mined.
The ore there has 20% uranium in it. 20%. That's 200,000 parts per million. I mean [00:34:30] 20%. That's, that's an
astronomical amount of
Chris Bolhuis: What. kind of unconformity is it? Is it a nonconformity? Is it igneous and metamorphic? Basement
rocks.
Dr. Jesse Reimink: Yep. Igneous
and metamorphic basement rocks with a, with a big, sedimentary basin on top of it.
Chris Bolhuis: quick review then. So you have these really, really deeply formed rocks, granites, metamorphic rocks and, and igneous rocks. Then over time, they get brought to the surface. Okay? So all the rocks that were above these deeply formed metamorphic and [00:35:00] igneous rocks is gone. And then you have renewed deposition, much younger material on top of them, and that knife like kind of razors contact between the deeply formed rocks. Old stuff, pre camber basement stuff and the new sediments on top. That's an unconformity. And it's a gap in time. It's this missing rock record. And you're saying that zone right there is where uranium can get dumped off and concentrated. And that's what happened with Cigar lake, right?
Dr. Jesse Reimink: That's exactly right. So you [00:35:30] have all these fluids flowing through the, the sandstones above this unconformity, the younger rocks on top of the unconformity. They're picking up uranium six plus and they're happy, and then they hit the unconformity and there's reducing fluids in there. The basement nices have a very different fluid composition, and the uranium will convert from six plus to four plus and get dropped out right at that boundary. So that's how these things are, are typically forming.
Chris Bolhuis: so back to throwback, to high school chemistry
class. [00:36:00] Redox reactions actually do have an application.
Everybody,
Dr. Jesse Reimink: that's right. It's not just turning green
solutions blue. It's actually controlling
critical
Chris Bolhuis: right.
Dr. Jesse Reimink: and where uranium deposits are and where other many
other deposits are formed as well.
Chris Bolhuis: that's right. First, the uranium has to be oxidized and then it needs to be reduced and there's your redox reaction.
Beautiful application right
there.
There you go.
Dr. Jesse Reimink: one.
Chemistry is interesting. One applied to Geology.
Chris Bolhuis: Yes. When applied, that's right. When
[00:36:30] just when applied to anything, then
Dr. Jesse Reimink: Yeah, that's true. that's true. that's a good point.
Hey Chris, what do you think? Uh, we cover it there.
Chris Bolhuis: think so. It's a wrap. We'll see. If you have
any questions, don't hesitate to hit us up. Email us.
Uh, let us know what you think.
Dr. Jesse Reimink: Absolutely, you can send us an email, planet geo cast gmail.com. Go to our website, planet geo cast.com, and uh, like we said before, if you wanna learn all the basics of geoscience, wanna learn about plate tectonics and how the mantle is melting beneath the seduction zone, go to Camp [00:37:00] Geo, our conversational textbook for the geosciences.
It's the first link in the show notes.
Chris Bolhuis: Cheers.
Dr. Jesse Reimink: Peace.
