Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 125 (8732 total)
Current session began: 
Page Loaded: 02-19-2017 6:52 AM
278 online now:
PaulK (1 member, 277 visitors)
Chatting now:  Chat room empty
Newest Member: timtak
Post Volume:
Total: 798,806 Year: 3,412/21,208 Month: 1,807/1,605 Week: 7/376 Day: 7/64 Hour: 0/0


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
1
2Next
Author Topic:   World's Oldest Rock?
RAZD
Member
Posts: 18124
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.1


Message 1 of 18 (687813)
01-16-2013 10:04 PM


http://www.npr.org/...est-rock-in-the-world-tells-us-a-story

quote:
... It's a zircon, from the Persian word "zargun" meaning "golden colored," an extremely durable mineral found all over the world. This one turned up in a dry, hilly region of Western Australia. It was sitting inside a larger rock, and when scientists checked, it turns out this little grain formed around 4.4 billion years ago. That would make it the oldest rock we've ever seen on this planet, old enough to know secrets about early Earth, old enough to tell us a little something about how life started here.

After all, this planet, geologists say, is only 4.5 or 4.6 billion years old. So this little grain has been around since almost the beginning — but not quite.

When geochemists Bruce Watson and Mark Harrison looked more closely at this grain, they could see where it "started." Crystals are minerals that grow, or harden from a hotter, liquid state, and this crystal got its start on the lower left, in the spot marked "core."

Geochemists know that zircons will grab more titanium when it's hotter, less titanium when it's colder, so if you count your titanium concentrations, you can figure out how hot it was when the rock formed: X amount of titanium, for example, means it was 600 degrees Celsius when it grew; Y amount of titanium means it was 350 degrees Celsius. Scientists call this equation "the titanium thermometer."

So Watson and Harrison counted titanium concentrations in a bunch of these very old zircon grains, matched them to the thermometer, and discovered that when these zircons formed, the temperatures ranged from about 680 degrees Celsius, plus or minus 20.

Rocks that crystallize at these temperatures have been exposed to water. This is something geologists know. ...

So, all of a sudden, here was evidence that the red hot, lava-laced, boiling, lifeless Earth of 4.4 billion years ago had water on it! What's more, Watson says, "we feel our results point more strongly toward the idea of surface water."

Here's why: It is now possible to imagine that life began on Earth almost as soon as the Earth began — that life (in the presence of water) is, if not inevitable, at least very insistent. Once you've got a planet with water — BINGO!

If that's true, chances for life in the universe suddenly improve — dramatically.

Here on Earth, life could have formed, been blown away, then formed again — and one of those times, down at the bottom of some temporary ocean, sitting by a warm vent — it stayed.

That's what this teeny chip of a rock is now allowing us to think: that life has such potency, such urgency, that as soon as life is possible — life happens!

That's a mighty big story to find in a pebble.


Hyperbole slightly over the top, but cool info eh?

Wonder how they dated the zircon ...

Enjoy.


we are limited in our ability to understand
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) • • •

Replies to this message:
 Message 4 by petrophysics1, posted 01-16-2013 11:26 PM RAZD has responded

  
Adminnemooseus
Director
Posts: 3733
Joined: 09-26-2002
Member Rating: 2.4


Message 2 of 18 (687815)
01-16-2013 10:14 PM


Thread Copied from Proposed New Topics Forum
Thread copied here from the World's Oldest Rock? thread in the Proposed New Topics forum.
    
foreveryoung
Member
Posts: 875
Joined: 12-26-2011


(1)
Message 3 of 18 (687817)
01-16-2013 11:12 PM


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.
Replies to this message:
 Message 5 by petrophysics1, posted 01-17-2013 12:07 AM foreveryoung has responded
 Message 8 by JonF, posted 01-17-2013 9:54 AM foreveryoung has acknowledged this reply

    
petrophysics1
Member
Posts: 342
From: Boulder, Wy
Joined: 04-05-2006


Message 4 of 18 (687820)
01-16-2013 11:26 PM
Reply to: Message 1 by RAZD
01-16-2013 10:04 PM


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?


This message is a reply to:
 Message 1 by RAZD, posted 01-16-2013 10:04 PM RAZD has responded

Replies to this message:
 Message 9 by RAZD, posted 01-17-2013 2:45 PM petrophysics1 has not yet responded

    
petrophysics1
Member
Posts: 342
From: Boulder, Wy
Joined: 04-05-2006


Message 5 of 18 (687824)
01-17-2013 12:07 AM
Reply to: Message 3 by foreveryoung
01-16-2013 11:12 PM


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.
This message is a reply to:
 Message 3 by foreveryoung, posted 01-16-2013 11:12 PM foreveryoung has responded

Replies to this message:
 Message 6 by foreveryoung, posted 01-17-2013 12:12 AM petrophysics1 has responded

    
foreveryoung
Member
Posts: 875
Joined: 12-26-2011


Message 6 of 18 (687826)
01-17-2013 12:12 AM
Reply to: Message 5 by petrophysics1
01-17-2013 12:07 AM


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.
This message is a reply to:
 Message 5 by petrophysics1, posted 01-17-2013 12:07 AM petrophysics1 has responded

Replies to this message:
 Message 7 by petrophysics1, posted 01-17-2013 3:13 AM foreveryoung has acknowledged this reply

    
petrophysics1
Member
Posts: 342
From: Boulder, Wy
Joined: 04-05-2006


(5)
Message 7 of 18 (687836)
01-17-2013 3:13 AM
Reply to: Message 6 by foreveryoung
01-17-2013 12:12 AM


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.


This message is a reply to:
 Message 6 by foreveryoung, posted 01-17-2013 12:12 AM foreveryoung has acknowledged this reply

    
JonF
Member
Posts: 3404
Joined: 06-23-2003
Member Rating: 3.3


Message 8 of 18 (687859)
01-17-2013 9:54 AM
Reply to: Message 3 by foreveryoung
01-16-2013 11:12 PM


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:


(They used the Tera-Wasserberg from of the concordia diagram, which you may not find familiar).

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”).


This message is a reply to:
 Message 3 by foreveryoung, posted 01-16-2013 11:12 PM foreveryoung has acknowledged this reply

  
RAZD
Member
Posts: 18124
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.1


Message 9 of 18 (687894)
01-17-2013 2:45 PM
Reply to: Message 4 by petrophysics1
01-16-2013 11:26 PM


one possibility
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.

Enjoy


we are limited in our ability to understand
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) • • •

This message is a reply to:
 Message 4 by petrophysics1, posted 01-16-2013 11:26 PM petrophysics1 has not yet responded

Replies to this message:
 Message 10 by JonF, posted 01-17-2013 6:20 PM RAZD has responded

  
JonF
Member
Posts: 3404
Joined: 06-23-2003
Member Rating: 3.3


Message 10 of 18 (687913)
01-17-2013 6:20 PM
Reply to: Message 9 by RAZD
01-17-2013 2:45 PM


Re: one possibility
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.


I think he/she is saying that the lead could only come from radioactive decay, which is the mainstream view.

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.


This message is a reply to:
 Message 9 by RAZD, posted 01-17-2013 2:45 PM RAZD has responded

Replies to this message:
 Message 11 by RAZD, posted 01-17-2013 8:24 PM JonF has responded

  
RAZD
Member
Posts: 18124
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.1


Message 11 of 18 (687929)
01-17-2013 8:24 PM
Reply to: Message 10 by JonF
01-17-2013 6:20 PM


Re: one possibility
... but we still don't know if lead was used to date the rock. The article does not say what was used.

Enjoy.


we are limited in our ability to understand
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) • • •

This message is a reply to:
 Message 10 by JonF, posted 01-17-2013 6:20 PM JonF has responded

Replies to this message:
 Message 12 by JonF, posted 01-18-2013 8:33 AM RAZD has acknowledged this reply

  
JonF
Member
Posts: 3404
Joined: 06-23-2003
Member Rating: 3.3


Message 12 of 18 (687977)
01-18-2013 8:33 AM
Reply to: Message 11 by RAZD
01-17-2013 8:24 PM


Re: one possibility
If It's Tuesday, This Must Be Belgium. If it's zircons, it's U-Pb.
This message is a reply to:
 Message 11 by RAZD, posted 01-17-2013 8:24 PM RAZD has acknowledged this reply

Replies to this message:
 Message 13 by Dr Adequate, posted 01-18-2013 4:38 PM JonF has not yet responded

  
Dr Adequate
Member
Posts: 15370
Joined: 07-20-2006
Member Rating: 3.3


Message 13 of 18 (688025)
01-18-2013 4:38 PM
Reply to: Message 12 by JonF
01-18-2013 8:33 AM


Re: one possibility
What JonF said. How else do you date a zircon?
This message is a reply to:
 Message 12 by JonF, posted 01-18-2013 8:33 AM JonF has not yet responded

Replies to this message:
 Message 14 by RAZD, posted 01-19-2013 4:18 PM Dr Adequate has not yet responded

  
RAZD
Member
Posts: 18124
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.1


Message 14 of 18 (688150)
01-19-2013 4:18 PM
Reply to: Message 13 by Dr Adequate
01-18-2013 4:38 PM


data, method
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 ...

Enjoy


we are limited in our ability to understand
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) • • •

This message is a reply to:
 Message 13 by Dr Adequate, posted 01-18-2013 4:38 PM Dr Adequate has not yet responded

Replies to this message:
 Message 15 by JonF, posted 01-19-2013 5:47 PM RAZD has acknowledged this reply
 Message 16 by petrophysics1, posted 01-21-2013 2:28 PM RAZD has acknowledged this reply

  
JonF
Member
Posts: 3404
Joined: 06-23-2003
Member Rating: 3.3


(1)
Message 15 of 18 (688154)
01-19-2013 5:47 PM
Reply to: Message 14 by RAZD
01-19-2013 4:18 PM


Re: data, method
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.


This message is a reply to:
 Message 14 by RAZD, posted 01-19-2013 4:18 PM RAZD has acknowledged this reply

  
1
2Next
Newer Topic | Older Topic
Jump to:


Copyright 2001-2015 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2017