[meteorite-list] CRE ages of Nakhlites and NWA 998

[Gerald Flaherty]

Help! CRE age??
Jerry Flaherty
----- Original Message ----- 
From: "Walter Branch" <waltbranch at bellsouth.net>
To: "Meteorite List" <meteorite-list at meteoritecentral.com>
Sent: Saturday, November 11, 2006 3:15 AM
Subject: [meteorite-list] CRE ages of Nakhlites and NWA 998


> Hello Everyone,
>
> I have been studying nakhlites in general and martian meteorite NWA 998 in 
> particular.  This paper,
> http://www-curator.jsc.nasa.gov/antmet/mmc/XXV_NWA998.pdf
>
> quotes a CRE of 9.3 m.y. using 38Ar.  This paper
>
> http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1137.pdf
>
> quotes a CRE age of 9.4 m.y, again using 38Ar.  However, the paper further 
> points out CRE ages using 3He and 21Ne are in better agreement (12.2 and 
> 11.7 m.y., respectively) and are in agreement with other nakhlite CRE 
> ages. The authors state, "All nakhlite CRE ages based on Ar are 
> significant (sic) younger than those based on He and Ne, an unexplained 
> characteristic also observed among some shergotite CRE ages."
>
> Does anyone know why this is?
>
> -Walter Branch
>
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