[meteorite-list] The scientific importance of subtype 3.00 meteorites and oxygen isotope analysis

From: Mendy Ouzillou <ouzillou_at_meteoritecentral.com>
Date: Sun, 16 Mar 2014 10:46:17 -0700 (PDT)
Message-ID: <1394991977.19719.YahooMailNeo_at_web162602.mail.bf1.yahoo.com>

Well, with the LPSC going on starting this week, I sure hope we get some participation from our scientific contributors to these questions.

Someone asked me to explain the scientific importance of meteoritic material with a 3.00 subtype. Reading through "The onset of metamorphism in ordinary and carbonaceous chondrites" by Grossman and Brearley 2005, I realized that a key tool used in the analysis of NWA 7731 and NWA 8276 was not present in the literature.

So, I'll start with this first part of questions:?
In my discussions with Dr. Agee, he mentioned that the heterogeneity of the oxygen isotope results is important because it indicates that the material has not been metamorphosed by heat or shock. Any heating would have caused the oxygen to begin to equilibriate. So, is the oxygen isotope analysis something that should be added to the list of factors used in evaluating low sub-types? Or is it a proxy for more complex tests? I am hoping that Karen Ziegler can also add some insights.

The second set of questions is perhaps more complex. What is the scientific importance of the 3.00 subtype??I can get this one kicked off, but would appreciate a more nuanced answer than what I can provide.
The subtype 3.00 represents the earliest glimpse of the properties of proto-planetary material in our solar system. A subtype of 3.00 means that the material has survived unchanged by heat (radioactive decay, pressure, impact/shock, etc.) or aqueous alteration since its formation. An implication of the unequilibrated nature of this material is that the parent body had to be quite small for it not to differentiate in any way.

Though both scientifically important, what different types of insights do we gain from CAIs versus subtype 3.00 material? The answer is I am sure that they complement each other, but in what way. Which is oldest?

The rarity of this type of material cannot be underestimated since between the only 3 known (Semarkona, NWA 7731 and NWA 8276), there is only 1,561g available for research and/or collectors. Of that total weight, Semarkona's 691g is almost unattainable. So, once again NWA delivers the goods!?

Regards,

Mendy Ouzillou?
Received on Sun 16 Mar 2014 01:46:17 PM PDT