[meteorite-list] Olivine, Quartz, and Enstatite... was Slump glass

[STARSANDSCOPES at aol.com]

Well said Elton!   Thanks    

Tom

In a message dated 2/8/2009 11:40:07 P.M. Mountain Standard  Time, 
mstreman53 at yahoo.com writes:

Good Question: "What about Olivine,  would the melt point of Olivine be 
higher than the glass?"

Molten olivine  at "silica glass" melting(aka"fusion")temperatures. 

Not at all as  olivine has the highest fusion temperature in Bowen's Reaction 
Series(BRS). Thus  it is the first to crystalize and precipitate out of 
magma.  This is why it  is used as a refactory material in making fire bricks. 
Olivine fuses at 1890*C,  well above where iron fuses.  The two minerals making up 
olivine:  forsterite and fayalite are very close in fusion temperatures as to 
be  negligible in general discussion.

Silica, aka "quartz" has the lowest  fusion temperature in BRS(1600*C +) and 
thusly rare in meteorites. That fact and  this:When olivine is forced to react 
with quartz in any of several situations  such as reheating,deep mantle 
pressures,extended cooling cycles,etc., the two  minerals reform to produce 
enstatite. (Does the H and E chondrite composition  and their parent bodies make more 
sense?) 

When this quality of olivine  and it's implications sink in, one might 
experience the "Eureka" effect.   It goes very, very far in explaining why meteorite 
petrology is the way it  is:Especially, pallasites.

Elton  

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