Boudinage and ore deposits
Don Findlay
Subject: Re: Proof of the ducking in the *&^*#%*?
Newsgroups: sci.geo.geology
Date: 2002-10-03 23:49:34 PST
Don Findlay <d...@tower.net.au> posta:
> Anyone feel like a comment on the validity of the comparison of
> 'boudinage structures' in the figures on this site?
>
> http://www.tower.net.au/~don/ore/brokenhill.html
>
> What do you reckon about the possible control on the mineralisation?
> Fact or fiction? Is this just "looks like" geology? (Looks like a
> duck, flies like a duck, and ^%$&^ like a duck? But how do we (would
> we) know it's really one at all?
>
Hi there,
Well, the overall sound of the site is quite agrressive ("I know the
truth and you don't") and this kind of attitude is generally strongly
correlated with pseudo geology without any scientific basis (see for
instance the posts of ... er .... some of the most noted contributors
of
this forum).
However, boudinaging has been observed at all scale, from outcrop to
the
whole crust (see some work about Galicia margin by G. Boillot for
instance). I've personnaly seen in alpine landscapes 100 m - wide
boudins. So, kilometer-sized boudins are not impossible.
This interpretation, however, needs to be substanciated. If they are
boudins, then the overall strain pattern should display a roughly EW
main elongation axis ("X") and a subvertical compression axis ("Z"),
that should be evidenced at the outcrop scale by foliation & lineation
trajectory, etc.
So, given the data available, my answer would be "this is not
impossible
but needs further demonstration before being believed !".
Cheers, JF
___________________________________________________
JF,
Thanks for the response and the cheerful signature. Let's see if we
can keep dodging the trolls and keep this on the coffee table (have a
ciggie...)
Well, ...belief and scientific basis...Kuhn wrote a book about this
way back, didn't he... saying that whether we believe something or
not is not based on
logic (science), but rather the other way round - the basis of science
resides in belief. So let's not demean it - the church doesn't have
copyright on belief by
any means. I guess science operates on a "I don't really believe it,
but that's the best explanation we can muster with the available data
at the moment" basis,
the reason being that there are always pieces of the jigsaw missing
(we understand we never have the whole story). What happens though
when you find a
missing piece, especially when it's an important one? Don't we jump
out of the bath and shout 'Eureka!'? I suppose that's what you're
referring to when
you mention 'truth'. But why is it one person can shout 'Eureka',
whilst others wonder what he's on about? I suppose the answer's
experience, and whether
the missing piece 'connects' in one's 'bigger picture'. It's what
allows us to make the cognitive leap to a bigger scale, and see the
whole, instead of the
anatomical parts. From then on our cognition operates on a different
place. We can be talking about the same thing, but the context is
different.
I guess what I was trying to do was ask folks if they see a connection
there that ties in with their own experience - not ask them if it
makes logical sense. I
don't think anyone would disagree that boudinage for epigenetic gold
makes logical sense, and recently there's been a tendency in that
direction in the oil
industry in their shift away from 'diapirism' to 'thin-skinned
extensional tectonics (boudinage by another word), but for things like
Broken Hill it tends to get
up people's noses. They find the suggestion an affront ( they've been
looking at it for a long time after all, and if it was boudinage then
they'd be the first to
know - "we are masters of this college, and what we don't know isn't
knowledge" - or soemthing).
So I guess that's the question: All you guys (and gals) out there -
does this look a teensy weensy bit like boudinage to you? And if you
reckon it does, what
then does it mean for explaining the location (and origin) of the
deposit? Your answer (JF) "Could be, let's look at it and see" is
miles in front of the one I
used to get. ....." A teensie weensie bit like boudinage?" Given
all the headscratching that's gone on over Broken Hill, you'd reckon
even if there was a
hint of a suspicion that boudinage might throw a bit of light on the
problem, that people *would* look at it closely. The only people who
can of course are
the people on the site. And they're not doing it. Why? It's been
freely on the table (in pubdom) for long enough (1982, 1994, 1998).
I reckon a lot of
people have a lot to gain by holding to the mystery (a bit like the
church). Seems so to me anyhow, ...if you come into a room full of
serious jigsaw players,
with the picture on the front of the box and start showing it around,
you're not everybody's friend. I used to think that's what people
were looking for. But
now I know they're not. Test it. Ask a Broken Hill afficionado to
include the possibility that that shape represents boudinage and see
what he says.
Since there's no thread on the topic Boudinage and ore deposits, I'm
changing the title to make one. Ducks can look after themselves.
Let's call it like it is.
By the way I tried to email you on this one instead of posting, but a
cut and paste on the address you give gets returned.
Don.
for what this is about:
http://www.tower.net.au/~don/ore/brokenhill.html