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Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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Author | Topic: World's Oldest Rock? | |||||||||||||||||||||||||||||||||||||
RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
The Oldest Rock In The World Tells Us A Story : Krulwich Wonders... : NPR
quote: Hyperbole slightly over the top, but cool info eh? Wonder how they dated the zircon ... Enjoy.by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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Adminnemooseus Administrator Posts: 3976 Joined: |
Thread copied here from the World's Oldest Rock? thread in the Proposed New Topics forum.
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foreveryoung Member (Idle past 611 days) Posts: 921 Joined:
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That is all interesting and mostly true. This is just a minor point, but a rock is not a single grain that is made of one mineral like zircon. That picture is of a grain of the mineral zircon. The rock that it was found in is probably not 4.4 billion years old; the zircon grain is. In order for the rock to be that old, it would have to be totally of an igneous nature. In all likelihood, the rock is a metasedimentary rock that first incorporated the zircon in a sedimentary layer and later underwent metamorphism to produce the rock we see today. If there is an igneous intrusion in the hill that the rock was found in, we can have an idea when the metamorphism took place that actually produced the rock they found.
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petrophysics1 Inactive Member |
Wonder how they dated the zircon ... A zircon is ZrSiO4, it is also the group name for tetragonal minerals with the general formula ASiO4 where "A" can only be Zr, Hg, Th, or U. Pb will not fit in this crystal structure. Suppose our little zircon has lead in it, where do you suppose it came from?
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petrophysics1 Inactive Member |
FEY, Do you work for Sunburst? If you do I know you. Would have sent you a PM but it's a PIA on this site.
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foreveryoung Member (Idle past 611 days) Posts: 921 Joined: |
Sunburst consulting? No. It looks like a nice place to work however. Do you know if they have internship positions available over the summer? I am looking for one. I have 3 semesters left before I earn by bachelors degree in geology.
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petrophysics1 Inactive Member
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FEY, I don't post here much, but I do read nearly everything. You seem like a nice kid. You need a geology job, maybe I can help you out.
Let's get you in the network, on facebook I'm Martin Granica on Linkedin I'm Martin P. Granica. I know more people than you can imagine in the oil and gas industry. Sometimes they are looking for a bright kid, for the summer or maybe more. BTW I don't care if people know my name, I'm a Conservative Republican and armed, and my name and address are a matter of public record since Feb. of 1963 when I got my first Amateur Radio Callsign WB2RJR from the FCC. For Admin: Who cares if this is off topic, I don't.
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JonF Member (Idle past 196 days) Posts: 6174 Joined: |
When they are dating zircons, they are using U-Pb dating, which Dr. Adequate covered briefly in Message 221 in the Geology thread.
Yeah, technically the zircon is a mineral, not a rock. Last I checked the oldest rocks came from the Great Slave Lake area of northwestern Canada; Priscoan (4.00-4.03 Ga) orthogneisses from northwestern Canada:
There have been reports of possibly older rocks, e.g. Neodymium-142 Evidence for Hadean Mafic Crust (free registration required for full text), but that's not generally accepted yet (Comment on Neodymium-142 Evidence for Hadean Mafic Crust).
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Pb will not fit in this crystal structure. Suppose our little zircon has lead in it, where do you suppose it came from? A possibility that had occurred to me, however I would still like to see it from the scientists that did the paper. Enjoyby our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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JonF Member (Idle past 196 days) Posts: 6174 Joined: |
Pb will not fit in this crystal structure. Suppose our little zircon has lead in it, where do you suppose it came from? A possibility that had occurred to me, however I would still like to see it from the scientists that did the paper. There is, of course, a really weentsy amount of lead mechanically trapped as the crystal grew around them (or whatever). That has a different isotopic composition than radiogenic lead and some other detectable properties, so correcting for "common lead" is very common ;-), and changes the raw date by a fraction of a percent or so. Buth these days the bleeding edge is sub-1% accuracy and every little bit of improvement is just that little bit of improvement more.
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
... but we still don't know if lead was used to date the rock. The article does not say what was used.
Enjoy.by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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JonF Member (Idle past 196 days) Posts: 6174 Joined: |
If It's Tuesday, This Must Be Belgium. If it's zircons, it's U-Pb.
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Dr Adequate Member (Idle past 313 days) Posts: 16113 Joined: |
What JonF said. How else do you date a zircon?
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Very likely, BUT nobody has provided a statement from the scientists that says so, and curiously THAT is what I am looking for, not assumptions.
I'd just like the actual data and method rather than rely on assumption and a journalistic article that is not peer reviewed. Capice? It astounds me that this is not understood ... Enjoyby our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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JonF Member (Idle past 196 days) Posts: 6174 Joined:
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I think I understand what you mean. It it's important to you, contact the author.
However, we know what the answer will be. For good reason. I'll expound if you are interested.
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