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Goldfinger

The Weathering of Meteorites

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Hi Guys:

Does anyone have access to information or reports on the weathering of meteorites? As you know- most of the meteorites found in this country are located in your western states like Az- Nev- N Mex,etc. I can certainly understand why since there's a lot of arid BLM land with little or no vegetation where one can roam about.

My question is how much faster do meteorites weather in the other climates? Some meteorites have been known to have fallen 25,000 years ago. (or longer) If those same meteorites had fallen in the midwest where we get more precipitation- would we still be able to find pieces of them or would they have weathered away into nothing?

Steve

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I don't know of any specific studies. As you indicated, the weathering of meteorites is dependent on the local weather conditions, soil conditions and composition of the meteorite. Ninninger wrote of his efforts to get palentologists to have an awareness of fossil metorites and they did start finding some...in wetter climates the most likely older find would be an iron or stoney-iron...( an outdated term, but I like it), I have also read about some Australian meteorites that are being studied in relation to weathering rates...

Fred

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I am only a hobbyist when it comes to meteorites.

I had a similar question as yours a while back. Found quite an odd sample in Lake Erie last year.

I live in northern PA. Very wet here and the soil is quite acidic.

I feel it would be silly for people to think there aren't meteorites scattered in EVERY part of the world. As you said -- Arid dry climate is easier to spot them as well as to keep them preserved. Us "Northern" people are (hopefully) finding specimens quite different from specimens from arid climates.

So I fundamentally believe if you live in a damp climate:

1) Iron corrodes, even if it is from a from outer space.

2) Fusion crust may be non-existent. (Rust and weathering from underneath and the fusion crust crumbles off.)

3) Streak test a rusty meteorite and guess what color streak you will get? Reddish brown.

(I wonder how many meteorites were discarded that way...)

Just my two cents......

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goldfinger, i'm sure you've noticed that i've also been interested in their weathering for some time, but i've generaly come up empty handed in any searches for information. some of the thing's i have found, are that the oldest is lake murray, USA an IAB iron 110mya: this being found in shale i'd guess would have been covered quickly in the cretaceous.

also don't forget hoba, canyon diablo etc

it is interesting to note that the oldest exposed one is from what i've read-wolf creek iron 300kyr. mostly rusted. (excluding antarctic ones)

only study i've found was for chondrites in a US dessert, weathering of chondrites......

the only way of reaching a conclusion is to read about the chemicals and minerals in them and read about how resistant they are to being oxidized or how strong the matrix is. that's my 2c.

i hope it's helped somewhat.

regards alexander

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Hi Guys:

I'd like to think there's enough information availible from documented falls all over the world to reach some general conclusions about the subject. I'm assuming no one has taken any time to study it but all it takes is someone to do the research and put the pieces together. Since it probably hasn't been done yet- it's seems like it's a nonissue.

Steve

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i won't disagree that looking into that won't help, all the info is good. but witnessed falls are recent, very few, and far between well compared to finds, while takes it millennia for them to weather away. also i think most would have been collected b4 they disintegrated or for urelites......eaten!!

They can and do date terrestrial age of finds by, well i think by atmospheric chlorine radioisotope inclusions, all bet they don't date them too often, i couldn't find out how old willemite is for all my searching.

come across any interesting info yourself?

cheers

pallasite alex

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