The Unknown Early Earth - Jack Hills Zircons Part II
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[00:00:00]
Chris Bolhuis: Hey there, Dr.
Reimink, how are we doing?
Dr. Jesse Reimink: Christopher! What's up, man?
Chris Bolhuis: Chris Topher, not a whole lot.
Dr. Jesse Reimink: Hey, I have a question for you. On average, how long does it take for former students to stop calling you Mr. [00:00:30] Bolhuis?
Chris Bolhuis: Oh, so this is really interesting. I can't believe we just brought this up. Uh, there is a, we had somebody go on maternity leave right across the hall from me, so they hired a long term sub for her and she is a former student. And, she still calls me Mr. Bolhuis
Dr. Jesse Reimink: Really?
Chris Bolhuis: I'm like, you gotta, you have to stop.
You have to stop doing this. You know, every
time she comes into my room, she's
Dr. Jesse Reimink: uh, has it been since she was a student of
yours?
Chris Bolhuis: seven years, you know, at least. Right. And she comes in, Hey, Mr. Bolhuis, um, I got this [00:01:00] question for you. And like, no, stop doing
this. Like I'm Chris, My
name is Chris. Okay. And she's, she just looks at me and she's like, I can't do that.
I can't, I can't do
that. Well then. They just offered her a full time job. So she got hired and all the administrators came down and went into her room, you know, and, and I, looked across and I saw what was going on. So I poked my head in, I said, Hey, congratulations. That's awesome. And said, now it's
Chris, you're going to call it We
are, we
Dr. Jesse Reimink: Chris, yeah. That's so funny.
Chris Bolhuis: [00:01:30] So she said, fair,
fair enough.
All right, Jesse, can we get down to business here? Can we do this? So last episode, we talked about the Jack Hill zircons in Western Australia, this conglomerate, but the zircons didn't come from the conglomerate. the zircon grains came from an igneous rock, some other source.
It was exposed at the surface. It was broken down. It was carried and deposited in a very localized place in Western Australia. And. Jesse, [00:02:00] why is this, again, let's keep coming back to this, why are the Jack Hill's zircons so important, in the study of old earth?
Dr. Jesse Reimink: So we talked about this in our intro to the old rocks sort of chapter here. They're the oldest pieces of earth. They're the oldest fragments of earth we have. So if we want to understand the oldest rocks, we have are 4 billion years old, or maybe 4. 2 billion years old. These things are 4. 38. So we have like a period of time. 500 [00:02:30] million years of earth history, basically animal life on earth, that amount of time where we don't know much. And these zircons and a few other locations are basically the only samples we have of that time period. So
Chris Bolhuis: Alright, but what would you say to somebody that's like, well, so what? we learned about earth's oldest, or our first pages in the book,
right? Who cares? Why is this important?
Dr. Jesse Reimink: well, I mean, it's a, frankly, that's a good question. It's something I sort of struggle with in part, with doing all this research. [00:03:00] It's very important scientifically. Like the, how unique is Earth? Why is Earth unique? When we look at other planets, other exoplanets, or other planetary bodies in our own system, we need to understand, does that one look at all like Earth?
Or does it look more like Venus or Mars? And why? we need to understand the lifetime of our planet, right? The full life cycle of our planet to understand why is earth unique today compared to venus? So it's intimately related to The [00:03:30] origin of life and the origin of life on earth and why is earth unique? So we have to know that starting point Where the person is born has a lot of say in how they develop over their lifetime, right? this is what we're talking about. Like where did you spend the first five years of your life? What country are you in? What kind of culture?
What was your household like like those are really important time periods for human development, and the same goes for Earth. Now, the part I struggle with is answering questions like that, that's not curing cancer, right? there's, [00:04:00] there are other research fields which are much more societally relevant for everybody's day to day life. I think it's important from a humanitarian perspective to understand this, but I, we don't need Tons of people and tons of money being thrown at this particular
problem. So, you know, there's a, there's a tension there, right? Like
Chris Bolhuis: Yeah. I know you put this on yourself a lot. We've many discussions, late night discussions, actually, about this very thing about, you know, you struggled with this. I don't think so much anymore. I think But I do [00:04:30] remember that, uh, you know, maybe eight, nine, 10 years ago, this was something that was heavy on your mind.
Mm hmm.
Dr. Jesse Reimink: I think what happened is I've developed other research, avenues, which are more societally relevant, which helps, so, so this is a passion project, you know, the earlier thing, there's other projects that are more. I would say impactful maybe from everybody's day to day life type of a thing that are also ongoing so
Chris Bolhuis: So is it also, Jesse, too, that we only have earth. this is what we have. And so the more [00:05:00] we know about it, I think that we always need to strive to learn as much about our planet as possible. because, I mean, who knows where the answers to these questions, who knows where they lead?
You don't know.
I don't know, but we don't have another one. We don't have an alternative. And so this quest to find out everything that we can about the way our planet operates and the way it operated in the past, they're important to know just because our only one. And we don't know where [00:05:30] those answers are going to lead
us.
Dr. Jesse Reimink: and I think Chris the other thing about this is that we had actually got a nice email from a listener sort of pointed out the fact that like, understanding how Earth's, you know, tortured history is really kind of thought provoking and you can map it onto your own life. it's sort of calming in a way, to know
Chris Bolhuis: Calming and some people are horrified by
Dr. Jesse Reimink: Yeah, but I think it's, I think it's important to consider these things, to think about these problems, to think about how old the earth [00:06:00] actually is and what do we know and not know about it our origin story. I think it's just a very good question. Good exercise to do as a human being. At least I've found it useful. and so, part of the reason in putting this book together is let's, let's all think about the early earth and what we know and don't know. And, where we come from. So it's an important problem in that regard. So, uh, yeah, there's, it's a very interesting conversation to bring up for sure.
Chris Bolhuis: All right. All right. Well, Jesse, let's talk about We talked about this in our prior episode, how [00:06:30] it's a very, very isolated place in Western Australia where this Jack Hill's zircon, comes from. the discovery on this? I mean, I know that this was in the late 1900s, but how, how did we find this?
Dr. Jesse Reimink: so basically it's a technique development thing. Like much of the early earth or much of geology, technique developments are really important for making big discoveries. Basically, up until early 80s, you had to [00:07:00] dissolve a bunch of zircon grains to get an age measurement. To get enough uranium and lead out of a sample, you had to take a bunch of zircon grains and dissolve them up.
So you had to collect like a bucket of rock. People would collect a full five gallon bucket full of rock, crush all that up. It was just an inefficient crushing and separating process, so you'd get some zircon out of that. And then you'd dissolve up a bunch of those grains, and then you'd get one age, one number out of that.
That's clearly a mixture of all those
Chris Bolhuis: Which is, yeah, that's going to be an [00:07:30] average then of all this, because you can have zircons in one deposit that are, 300 million years
different in age.
Dr. Jesse Reimink: this really
limited people from looking at detrital grains. Like you wouldn't look at detrital grains cause you're, you're not just going to mix them all together. Cause as you said, you can have 300 million years age difference between them. So you knew you were
going to get a mixed
number there.
Chris Bolhuis: Yeah, right. Real quick. I just want to bring that back to where I, where I came up with 300 million years. You said that some of the zircons can be, [00:08:00] you know, 4. 38 billion years old, and some of them are, you know, 4. 0 billion years old. Well, 0. 3 billion years is 300 million years, which is an incredibly
long amount of time.
It's, it's
Dr. Jesse Reimink: much, so much, right? It's crazy.
Chris Bolhuis: wasn't just pulling 300
out of, out of a hat. I just,
Dr. Jesse Reimink: but it is, yeah, we got to be wary of talking about our decimal points here because
they're big numbers. So
Chris Bolhuis: 0. 1 billion years is a hundred million, you know, and the dinosaurs met their [00:08:30] extinction a mere 65 million years ago, you know?
Dr. Jesse Reimink: it's crazy.
it's.
crazy. so when you were doing stuff like that, even the technique develops that you could dissolve just one zircon grain, but even that were old grains. And I'll turn to image number one in the stack here. This is a gif that we made that shows the age variation in a zircon grain. So this one grain, this is the size of a grain of sand. The inner parts, there's two inner parts that are shown there in yellow kind of orange. Those are both four billion [00:09:00] years old. 4. 02 billion years old. The
outer part, the green part, the rim is 3. 2 billion years old.
And so if
you dissolve that whole grain, you're going to get a massive mixture of ages.
Um, and
Chris Bolhuis: You said, wait a minute. Hold on. Hold on. Hold on. Hold on. You said 4. 02 for the middle part, the middle two parts
4. 02 and then 3. 2 for the rim.
Dr. Jesse Reimink: Yeah, that's exactly
Chris Bolhuis: That's a massive amount of time.
Dr. Jesse Reimink: Huge, right? So
Chris Bolhuis: Okay. Can we, can we talk about that? I know what you're going to say. If you mix those two ages, you're going to get an average [00:09:30] and it's going to be really, really wrong.
But all right. I need to get to the other part of that. How do you get such a diversity from the center of the zircon grain to the outer edge? This is not just rate of
cooling. can't
Dr. Jesse Reimink: definitely not. No, this is the outer outer rim of that grain is metamorphic. It was formed during a metamorphic event where new zircon was kind of added on to this nucleus because other minerals broke down, released zirconium, and they grew zircon. So that's all metamorphically grown at 3.
2 billion [00:10:00] years old. And so, basically all old zircons have seen a metamorphic event at some point, because Chris, you pointed out, they've been around for hundreds and hundreds of millions of
years. They've been metamorphosed, even before they were broken down
and weathered in a stream.
Chris Bolhuis: Are you saying then that the rim of the zircon grain here was maybe melted and that reset the clock at some
Dr. Jesse Reimink: Yes, Or,
it's new growth. it's either been melted and recrystallized, so it it could be, like, resorbed and then recrystallized, or it can be new growth of zircon during [00:10:30] a high grade metamorphic event where there's, little bits of melt around in the rock.
So,
Chris Bolhuis: And then is that a common thing to see in zircons? Do you
see this as kind of I think of it as a zoning,
right? This looks like a zoning. So,
Dr. Jesse Reimink: really old zircons, for sure, because they're older, they've had more chance to see a metamorphic event in their
lifetime.
Chris Bolhuis: in this image, I'm looking at a bunch of what look like pits. What are those pits?
Dr. Jesse Reimink: Great segue. these pits are analytical spots. So if our techniques only allowed us to dissolve a grain, you'd get a [00:11:00] mixture of ages with these things,
but this thing called the ion microprobe came around in the early 80s and allowed, this is what we call an in situ technique that allows you to put little tiny spots, those are little pits, Pits, the squares and the little circles there are little spots that were placed with a high energy ion beam that blasts a little bit into the zircon and you can measure ages. in the individual zones of the zircon grain. And image number two is a photo of one version of these, which is called an ion microprobe. [00:11:30] This thing's huge. It takes up the size of a garage or a very large room in your house. This is a big
big machine, many millions of dollars
to purchase one of
these.
this?
one's in, in Australia. there's a couple of different models of them that are made now, and they're
kind of all over.
Chris Bolhuis: do you have an ion microbe?
Dr. Jesse Reimink: We do not have an ion Microprobe?
at Penn State. Um, Well, the material scientists might. We don't have one and that's like a geoscience focused one. So
Chris Bolhuis: Why is that? If I feel like you should have an ion microprobe.
Dr. Jesse Reimink: I would love one. They cost about [00:12:00] eight million dollars to buy
and then a whole bunch of money to support. You have to have two full time technicians work keeping them up and running and
a massive endeavor to get one of these
up and
going.
Chris Bolhuis: So looking at this image, I want to talk about this a little bit. Where is the detector? Is it on the right hand side or the left hand
side?
Dr. Jesse Reimink: left hand side is the detector. So the sample will go in on the right hand side
and ions will be generated.
Chris Bolhuis: the ions are generated and they're shot through that tube. And then that elbow, that 90 degree bend there, at the bend right [00:12:30] at the crook of the elbow.
You have magnets, right? Is that what's going
Dr. Jesse Reimink: So there's actually two bends in this. The, the magnet bend is inside the box, the big box
with the little lights on it. That's the magnet. The
other
bend, the bend you're, yeah, that says shrimp on it. The bend you're
referring to it filters for energy first. So it filters for energy with electric fields.
Then it filters for mass
in the big box in a magnet
Chris Bolhuis: Right. and so the idea then is that when you shoot these different ions or these different isotopes through the [00:13:00] magnet, the heavier ions will bend a little bit less than the lighter ions because of their, their momentum. And you know, the magnet's going to have a little bit less of an effect on the heavier ones.
And that's how you're able to, to kind of separate out these ions that have very similar
masses.
Dr. Jesse Reimink: exactly right. So you can separate uranium from lead, but you can also separate uranium 238 from uranium 235 and lead
206 from 207 from 204. So this development ushered in [00:13:30] a massive wave of of new research, including the discovery of these old grains, because people could go look at detrital zircon grains and analyze little spots in detrital grains.
And they realized, wait, some of these are really, really old. The first paper was published in 1983 on these Jack Hill's zircons. So that's kind of the discovery. And then there's been research on these things. I mean, there's thousands of papers that have been written on the Jack Hill zircons at this point, but, that's the discovery and people continue to work on these, these zircon grains.[00:14:00]
Chris Bolhuis: Very, very cool, Jesse. so there we go. I think we can move past the discovery phase now. Let's talk about, maybe let's get into the controversy. That's what we promised we were going to do. So let's do it. What's last episode, we talked about what is generally accepted with. These zircons and what we know where's the controversy then?
Dr. Jesse Reimink: Yeah, the controversy really is everywhere, everywhere else. And we covered, we know they're zircon, so we know they crystallized in sort of igneous, [00:14:30] felsic to intermediate rocks. That's accepted. We talked about the oxygen isotopes and how they record liquid water. Most people generally agree on that one. We talked a little bit about the hafnium isotopes that point to something older being around that was the source for these melts and then these zircons. Basically, since 1983, people have said, okay, we agree upon the ages. Well, there's a bit of debate about the ages for a decade, and then everybody in the 90s said, okay, yeah, we agree on microprobes are good and the ages are right. [00:15:00] Then people have thrown the geochemical book at these zircon grains, trying to come up with basically things you can use in zircon to tell you something about the magma. So people have used ratios of elements, and tried to figure out what was the amount of water in the magma? How much water was in the magma that crystallized these zircons? oxygen fugacity is another term for that. But how much water was in those? People have tried to develop a bunch of techniques to do that.
Chris Bolhuis: So can I ask a question then are these [00:15:30] zircons? They can't always be pure.
Dr. Jesse Reimink: that's right.
Chris Bolhuis: for instance, I have a bunch of fluorite from Southern, Illinois And they're beautiful these beautiful little crystals of fluorite and they've got pyrite inclusions in them Does Zircon have that kind of thing too?
Or like you get the same thing with quartz or even, even diamonds, diamonds have these little
inclusions
or little impurities inside of them. Right? we talked about this in our diamond episode a ways back a long time ago.
Dr. Jesse Reimink: So that's a really, great [00:16:00] point, Chris. And the answer is yes, these zircons have inclusions in them. And you can think about these in really simplistically, like Geology 101. If there's a mineral included in another mineral, which one came first?
Chris Bolhuis: well, the inclusion had to be there
Dr. Jesse Reimink: Exactly why? Because the second mineral grows around it, right? It grows around the, the other mineral. So there are inclusions in zircons, and these zircons we know are old and the inclusions, therefore they're probably just from the same [00:16:30] magma, but they crystallized earlier in the magma sequence in some way, shape or form.
The zircon grew around them, but you can tell a lot inclusions are kind of these mini rocks. So if you look at inclusions in the circon. And you see, people have done this, they've seen muscovite, and apatite, and quartz. Well, quartz and muscovite, that's a granite. If you see quartz, feldspar, muscovite, that's a granite. And so these are kind of like little mini rocks that it tells you something about what the rock was,
Chris Bolhuis: What the parent rock
was.
That's [00:17:00] right.
That's right.
Dr. Jesse Reimink: or an
Chris Bolhuis: Because again, these Zircons are in a detrital, conglomerate rock. They didn't come from that. They didn't form from that. They formed from something else. And this, these inclusions that are going to give you geoscientists an idea as to was this an intermediate rock
or was this a granitic rock?
And it's also probably going to tell you about, temperatures and pressures,
Dr. Jesse Reimink: That's exactly right. Exactly right. So there's debate about these because, these grains, and I'll point to image number three here quickly, because this is [00:17:30] a zircon that has an inclusion. So you can see the zircon is kind of has this nice sort of tree ring growth area. And there's a big white blotch in there.
That's an apatite grain. So it's a mineral, different mineral grain that's included in the zircon. The zircon grew around it. And so some people I have argued that these little mini rocks tell you a lot about the rock itself, the parental rock was. However, these grains have also been metamorphosed heavily, and so the minerals in the inclusions can get perturbed during [00:18:00] metamorphism, just like minerals in a rock get altered by metamorphism as well.
So, there's debate about that. The reliability of these inclusion signals, basically.
Chris Bolhuis: Okay. Can I, then I have a couple of questions then that I want to ask because I start to think about, all right. Why is there debate about this? Is it because of the, the source of the inclusions then? you know, maybe these inclusions don't represent the initial granitic rock. Maybe they formed because of some other process.
Before, such as plate [00:18:30] tectonics, which I think is, would be a super interesting
thing, you
Dr. Jesse Reimink: you're exactly,
Chris Bolhuis: plate tectonics is older than the zircon grain, which is like, that's kind of important to your studies.
Dr. Jesse Reimink: So you're exactly right, Chris. The debate comes as whether those grains, those inclusions are actually primary. Because we saw in the previous chapter, the previous episode, some of those images, you saw the zircon grains are cracked. And during metamorphism, um, Elements can get into those cracks and reset the little [00:19:00] mini rocks that are these inclusions,
and they can be altered changed.
And so there's a significant amount of debate about whether the inclusions are what we call primary. Are they the original thing? Do they represent the original rock or not?
Chris Bolhuis: Hold on, I got a thought on this then, because when I think about like minerals that formed later on, like these porphyro blasts in our gore mountain garnets,
right,
that, that gabbro rock, they're awesome. You have these red, beautiful almondine crystals, but you can tell [00:19:30] Jesse, when you look at the rock that it took.
Chemicals. It took elements out of the rock and use them to grow the garnets they're like eyeballs, right? can see this zone where the mineral took what it wanted from the rock.
Does that make sense?
What I'm saying? So shouldn't, you see that then if these are metamorphic process inclusions, we see that kind of zoning around the inclusions then also?
Dr. Jesse Reimink: these are so small that they're probably, you know, do that zoning, you [00:20:00] have to have some kind of scale of chemical reaction going on. These are so small that there probably were In chemical equilibrium. So they didn't really create this zoning pattern as you're beautifully describing there. if one got reset, they all got reset. Or if one part of the inclusion got reset, it all got reset because it's just so
small
Chris Bolhuis: if they grew that way, then they're really not inclusions
and they're not older than the, than the mineral
that they're in either.
Dr. Jesse Reimink: So that's the sort of debate is whether these inclusions are the, the same age as the zircon or if they're much younger and they've been kind of [00:20:30] overprinted during this metamorphic sequence. So a lot of debate on that one. The grains, the zircon grains also have, oh, I'll say quote unquote inclusions, they have other elements in them that substitute in, like uranium, substitutes in, and is found at the parts per million level in zircon, 500, 800 parts per million.
There are other
elements that do that too.
Chris Bolhuis: ionic substitution, Jesse is really an important
process in the field of geology. Um, you know, and so I dunno, I think about it this [00:21:00] way and I know this is really simplistic and you might not like it, but I'm going to do it anyway.
When you, when you think about.
Dr. Jesse Reimink: Yeah.
Chris Bolhuis: ionic substitution, okay, think of how dolomite forms when I think about ionic substitution, you know, limestone and dolostone are very common sedimentary rocks, but dolostone usually doesn't form directly.
It usually came from limestone and then got dolatum, Dolatumized? [00:21:30]
Dr. Jesse Reimink: Dolomitized.
Chris Bolhuis: Yeah. So what that means is that magnesium goes in and replaces the calcium in the structure of the magnesium calcium carbonate now. And it's done through ionic substitution. It's kind of like if you build a brick wall.
And then you go into the middle of the wall and you pull a brick out and you put a different brick in, maybe a different color, a little bit different size. Sometimes too, maybe it has to be same size or [00:22:00] smaller. It can't be bigger cause it won't fit. and you take the brick that you took out and you put it somewhere else on the wall.
Right. and this is kind of like how ionic substitution works. And it's just as, it's a really important process
in a lot of fields of geology. Yeah.
Dr. Jesse Reimink: of them. and the way to, to sort of think about this is that zircon in your brick wall analogy, which was a great one, Chris, I totally happy with that
analogy. I
like that. Yeah. Yeah. Yeah. No, no, no, not at all. Because this is exactly what's going on. The brick wall analogy here, if calcite [00:22:30] is a brick wall with no mortar in it.
Like it's just bricks set on top of each other. So it's easy to take them out and place them and replace them. Zircon is one with mortar in place. It's really hard to take a brick out of a brick wall that's, solid brick
wall that has mortar there. Exactly. It's really hard because once it's in the grain, elements don't really diffuse through it very much.
They just are locked in. So Zircon is really good at recording the primary chemistry. If you have a big pile of bricks that have different colors in them, [00:23:00] and the zircon is growing, we're just taking the bricks and putting them into the wall. So the wall will represent our pile pretty well. How random was the elemental composition of the pile? Different bricks, like the zircon will lock it in really well. But not perfectly, because there's, analogy, some bricks fit better, some bricks don't fit quite as well, bricks break a little bit easier, so there's all these different ways that you take a pile of bricks and make the wall, and that's magma to magma.
to zircon. And so people have used these chemical signatures. So [00:23:30] how much uranium is in zircon? How much thorium is in zircon? Metamorphic zircon has a very different thorium uranium ratio than igneous zircon. so people have used all sorts of different chemical signatures. Tracers to try and infer what the magma was.
What did the pile of bricks look like? And say something about that from looking at the wall. But there's a disconnect there, right? Like we're missing, we don't know that the wall is a perfect representation of the pile of bricks.
and I've done this, I've looked at uranium ytterbium ratios.
I've, can, you [00:24:00] can throw any number of ratios at
Chris Bolhuis: Now you're just making up words,
Jesse. You
just
make it up You
just,
Dr. Jesse Reimink: let me just say that my point is that there's tons of different colors of bricks that are in the zircon wall and people use all sorts of information from there.
And sometimes it's reliable, sometimes not.
Chris Bolhuis: Okay. So Jesse, um, let's, I have a question then that I want to throw at you here
and I'm, I'm going to limit you on this. I'm going to put in a 92nd
time limit on [00:24:30] this Okay. And I,
Dr. Jesse Reimink: frequently
Chris Bolhuis: I I don't know.
Dr. Jesse Reimink: out and pulled out
Chris Bolhuis: I haven't because I'm into it. I'm into the discussion. But, in order to move things along, give us this summary then of the, uh, how do I want to say this?
Give us a summary of the scientific debate
here surrounding the Jack Hill's zircons.
Dr. Jesse Reimink: What we're arguing about mostly, this all goes into one bin, one category is what was the composition of the parental rocks? Was it intermediate? Was [00:25:00] it felsic? Etc. People have argued about plate tectonics. They've proposed that these were formed by plate tectonics using mineral inclusions. They've also proposed that these zircon grains have been formed in meteorite impacts using a lot of the chemical signatures that we were talking about with the bricks and mortar and all that stuff. People have also proposed that these are from hydrous magmas, or hydrated magmas, which are again subduction zone magmas, or the ones that are formed by, water induced melting. And then people, I've, you know, published a paper saying that [00:25:30] these zircons formed in what we call Archean TTGs, which is just a category of rocks that are unique to the early Earth. they're sort of what you find when you walk across the Canadian Shield. I would say those are some of, those are just kind of a high level summary of like what people have proposed.
There are people who have proposed that there are diamonds in these grains, inclusions in these zircon grains. That was later refuted, but,
There's a whole bunch of proposals here, but they mostly are surrounding what was the rock that formed the zircons and what tectonic setting did it form in. And you can find[00:26:00]
any proposal you want in there, basically.
Chris Bolhuis: All right. Hey, good job,
Dr. Jesse Reimink: Was that a good summary? I did it. Okay,
Chris Bolhuis: to, your 90 seconds.
You stayed to your 90
Dr. Jesse Reimink: I'm perfect. Excellent. So Chris, I'm curious now, let me flip it to you.
you sort of let out by wanting to focus on and keeping us focused on why is this important? What do you think about that? Like, what do you think about the sort of what we know, which we talked about last chapter, and what we don't know, which we focused on this chapter, like how, are you more or less convinced that this is important? Or what is important in [00:26:30] it? Or what is not?
Chris Bolhuis: so I, I think my answer is going to surprise you a little bit.
When I think about the answering this question about, what is the formation? What's the, what was the parent rock for the Jack Hill zircons? And, was this early, early tectonics and, you answering when plate tectonics began on earth.
I think about why plate tectonics doesn't exist on the other terrestrial planets in a way similar to what we have here on earth. it's a really complicated thing. You know, uh, [00:27:00] and Mars. They're very different from planet earth because one they're different compositionally, especially Mercury, because it, formed much closer to the sun.
And so it had a different, condensation, temperatures. It, it didn't allow for the silicates to form. There's just too hot there. So I get that, but it's also different sizes, but what about Venus? Why doesn't, Venus is similar size, similar shape, you know, all of this stuff. And, and yet it doesn't have tech, we don't think anyway, tectonics in the way that we do.
[00:27:30] And just think about why. And so it's important from just the standpoint of planetary geology. I think we need to answer this question. I think it's an important question, but like you said, too, it's not critical to life. it's philosophical.
which I think is, I think is important.
But I don't, I don't know.
Dr. Jesse Reimink: It's
important to have
some people doing philosophy. It's not important
that everybody researches, you know, when I would not be a fan of having a huge, a number of people spending their lives, trying to [00:28:00] answer this question about the early earth,
think it's important that some people do for sure. and I think it's important that we have this conversation that people listen to this podcast and think about these things, but we don't need to be throwing vast amounts of resources, human and financial resources at people. This particular problem. it is really
important for the geologists, like where we start.
So
for sure, where did Earth start? for sure, Um,
Chris Bolhuis: let me turn this around a bit on you. Then have you thought about something that you're really interested [00:28:30] in answering a question, geological question that has societal relevance?
Dr. Jesse Reimink: the obvious one here. and I think a lot of people share this opinion is that when we think about critical resources, quote unquote critical elements, you know, lithium, neodymium, that's a really understudied problem, thinking about, not just where is neodymium, but why is it there?
Why is neodymium found in this weird magma composition or
this [00:29:00] weird carbonite complex?
Chris Bolhuis: know that.
We
need
to
know. because that's, certainly then changes how we look for
Dr. Jesse Reimink: How do we look for it. Exactly. So there's a feedback between the people doing the research and the, the companies, and there's, you know, a massive overlap. Companies do research and researchers go look for it too, there's a feedback between those two or communication between those two that I think is really an important one.
And a lot of people are moving into that space. A lot of people with sort of my expertise set are moving in that direction. And we're sort of thinking along the same lines too. So [00:29:30] that's the more, you know, societally relevant, um, yeah. thing. You know, back to the Jack Hill zircons, I kind of struggle with what's the path forward to answer these questions.
Like, how do we make progress? and
that I don't really know. I, I think one interesting, because these grains are small. They're tiny. They have a long tortured history. So we don't really know which signatures
are reliably original, or not. That's one of the big difficulties, and [00:30:00] each grain is different from the grain next to it. So you basically have to interpret one grain on its own, tell a story with one grain, tell a story with another grain. One of the paths forward that's pretty exciting that people should be aware of is that we're finding More and more really old zircons around the world, greater than four billion years.
There's probably like 15 locations now that they don't have as many of the, as the Jack Hills area does. That's still the sort of big dog, but we're finding more across the world. and they're found in [00:30:30] detrital much like the Jack Hills ones. And so there's a big space, I think, to discover more old grains and more old rocks.
I think that's an exciting space and that will help, help our further our understanding of the early earth, I guess.
Chris Bolhuis: And you know, too, What you said about neodymium and, and these other rare earth elements, in knowing how they form, I think the more we learn about plate tectonics too, though, Jesse
is going to become extremely important in [00:31:00] understanding more about how these rare earth
elements formed and where, to find them.
So. Answering this question about the, some of the questions about Jack Hills may actually lead us in a different direction that we never anticipated. I don't know. Is that, is that
Dr. Jesse Reimink: That's exactly right. I think, you know, how did, basically what we're talking about, we're talking about neodymium, we've, covered this a whole bunch in our, like, Geology of Critical Elements series. All these elements are distillate, getting enriched
neodymium and lithium, it's the last stage.
You don't need continental crust, you need distilled continental crust [00:31:30] to get those things. And that step is really interesting. There's a lot we don't know about how do you take all the neodymium in a crustal column and move it up to the top somewhere in some weird magma type? That's a really interesting scientific question. so yeah, there's a lot of stuff, I would say it's not just forming continental crust, it's distilling the continental crust, it's taking the continental crust and distilling it even more. that's, you know, an interesting sort of path forward. Anyway. Okay. We've strayed quite a ways from the Jekyll Zircons with this discussion, but it brings up a really interesting [00:32:00] point when we think about the early earth. Like, again, to summarize, I think it's really important philosophically that people understand this and think about this and at least, what we know and don't know.
And just consider what the early earth was like. 4. that we have a sample of earth that's 4. 38 billion years old. That's cool. That's really
cool.
Anyway, what do you think, Chris? Is that a wrap?
Chris Bolhuis: I think that's a wrap, Jess.
Dr. Jesse Reimink: Okay. Yeah, sounds good. The
Chris Bolhuis: Reimink right here. This, this episode
Dr. Jesse Reimink: way it
Chris Bolhuis: like, [00:32:30] Ha ha ha ha ha ha ha ha Okay.
Dr. Jesse Reimink: that I control the little button that says
record and not record, I just pause it when you're talking so I don't record when you're talking.
Chris Bolhuis: Well, actually, actually, Chris Bolhuis, just so everybody knows, was not even a part of this episode.
This was AI
Dr. Jesse Reimink: This is AI Chris, that's exactly right. You can tell because he just repeats himself.
I think that's, uh, I think that's pretty good wrap. hey, if you're listening to this on the podcast, you can find this chapter, with the images that we've talked about in the Camp Geo book on the Camp [00:33:00] Geo app there, you can download that first link in your show notes, head there. That's one way to support us. The other way is to go to our website, planetgeocast. com and You can support us. There's a button there. You can also send us an email at planetgeocast. gmail. com. We love getting listener questions and always appreciate that and follow us on all the social medias, Planet Geocast.
Chris Bolhuis: Cheers.
Dr. Jesse Reimink: Peace.
[00:33:30]
