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RE: Monahans (1998)

Dear Listees,
I also searched Metbase, and came up with 'no records found' for the
presence of halite or sylvite in other meteorites.

Puzzling to say the least.

I thought I was looking at majorite or ringwoodite when I first saw the
specimen.

I have made a few inquiries regarding the Earth's ability to 'make' igneous
forms of halite and sylvite. I was told that there is a form of igneous
anhydrite, but the crystals are very small, not on the scale of the ones
found in Monahans. These are usually ash by-products, as chlorine is
released in eruptions, and settles to ground. First gases out of eruptions
are  CO2, then Cl, then S. 

Which leads to next question. If we follow earth model, is there a
possiblity that since this an impact melt, what are the chances that the
segregation and subsequent crystal formation were produced by impacts of
other masses with the parent body? With or without any vulcanism in parent
body history. If temps did not approach volatilization of Cl, would it
still be possible to see what we do in this particular meteorite? I could
not find any stability field references of these minerals, maybe someone
has some input on this.

Another thing, microprobes can detect metals and semi-metals. Stoichiometry
is used to assume cation. What did JSC do to determine chemistry? How much
Cl was there in the rock? Thin section may not be enough!

So, ah, what's going on here??

Walt