[meteorite-list] Two Questions

[Gerald Flaherty]

Hi Walter, Eric and List,
Would Martian Tectonic forces ie. subduction, be a possible mechanism to 
trap and transport atmospheric gases into the bowels of the planet, later to 
be be contained in a magma chamber?
Just an odd thought. Jerry
----- Original Message ----- 
From: <star-bits at comcast.net>
To: <meteorite-list at meteoritecentral.com>
Sent: Tuesday, May 24, 2005 1:26 PM
Subject: Re: [meteorite-list] Two Questions


> Walter Branch wrote:
>
> <I been researching but I can't find the answers to two questions.
>
> First, what is the mechanism by which atmospheric gasses
> are trapped in the formation of basalts?  I have been doing some
> lit reviews on martian meteorites and I find it interesting that some
> were formed in magma chambers deep undergound.  indeed, some are
> thought to have formed several kilometers down.  How does the
> Martian atmosphere get trapped in cooling rock so far underground.>
>
> Hello Walter
>
>    The mechanism for trapping gasses in Martian basalts is not entirely 
> clear.  One method that has been proven is implanting during shock events, 
> such as being blasted off Mars.  However there are some problems with this 
> as well such as sometimes the gasses are fractionated (Kr/Xe ratio changes 
> for instance).  So although impact is likely part of the answer it isn't a 
> clear winner.  Another suggestion is fluid (water) transplant, however the 
> gasses mostly reside in the water unaltered portions so this is likely not 
> the answer.  Trapping of mantle gasses during cooling has been suggested, 
> but mantle reservoirs of gasses should have different ratios than 
> atmospheric.   So the exact mechanism is undetermined.
>
> <Second, when determining Cosmic Ray Exposure ages, can atmospheric
> fragmentation and ablation of a meteoroid affect the results from such
> testing and if so, how are fragmentation and ablation taken into
> consideration when determiniing CREs?>
>
> Yes fragmentation and ablation can affect the results and must be taken 
> into account.  Cosmic rays generally penetrate 3-10 meters into asteroidal 
> bodies.  Parts buried more than 10 meters or so receive almost no cosmic 
> ray exposure so their CRE age is zero.   If depth isn't taken into account 
> a surface sample would show a older CRE than one at 5 meters.   One method 
> of determining depth is with Neon isotopes which have been shown to have a 
> constant relationship with burial depth and cosmic ray exposure.  So the 
> neon can be used to determine depth and the other elemental isotopes can 
> then be adusted for depth to give the CRE age.
>
>
> --
> Eric Olson
> ELKK Meteorites
> http://www.star-bits.com
>
>
>> Second try at posting this email:
>>
>> Hello Everyone,
>>
>> I been researching but I can't find the answers to two questions.
>>
>> First, what is the mechanism by which atmospheric gasses
>> are trapped in the formation of basalts?  I have been doing some
>> lit reviews on martian meteorites and I find it interesting that some
>> were formed in magma chambers deep undergound.  indeed, some are
>> thought to have formed several kilometers down.  How does the
>> Martian atmosphere get trapped in cooling rock so far underground.
>>
>> Second, when determining Cosmic Ray Exposure ages, can atmospheric
>> fragmentation and ablation of a meteoroid affect the results from such
>> testing and if so, how are fragmentation and ablation taken into
>> consideration when determiniing CREs?
>>
>> Thanks to anyone who can help me understand these processes.
>>
>> -Walter Branch
>>
>>
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