[meteorite-list] World record 1, 250g tektite from Philippines??

From: Aubrey Whymark <tinbider_at_meteoritecentral.com>
Date: Wed, 16 Feb 2011 03:42:31 +0000 (GMT)
Message-ID: <92532.99794.qm_at_web28508.mail.ukl.yahoo.com>

Hi

This size tektite is perfectly feasible from China, but it would have been a Muong Nong-type tektite, which I consider to be someway between tektites and impactites. It would not have been a true splashform.

If we take only true splashforms, ignore the incompletely melted and homogenised layered Muong Nong-types, then the largest tektites occur some 1,750 km from the impact site. This is true of the Australasian impact and the Chesapeake impact.

Why do the biggest tektites not occur closest to the impact?
Well, the reasons are complex, but basically as you move closer to the impact site the energy levels decrease as the energy of impact is spread over a wider area. The melt sheet is not ejected into 'space' before being disrupted. So proximal tektites form at lower atmospheric levels - they interact with the atmosphere and cascade into smaller forms. The large blocks of semi-melted material comprising Muong Nong tektites form at even lower energy levels - insufficient to even fully melt them.

Back to the medial distance Philippinites. The melt sheet just about reached space before being disrupted into tektite bodies. (Rare Philippinites show some plastic deformation during their exit). The viscosity was low (as Philippinites are mainly spherical), but not as low as Australites (which encourages further break-up). A large sphere remains as a sphere and will not interact with the atmosphere to form a disc that cascades into smaller spheres.

Move from the Philippines to Australia and tektites become progressively smaller as expected. The temperature of the melt was higher and the viscosity even lower. Also distal tektites were ejected at a lower angle and although no plastic distortion is recorded (perhaps due to them being exceedingly hot and the low viscosity), some atmospheric interaction, due to the lower ejection angle may have resulted in an early cascading effect.

So 1,750 km or thereabouts from the impact site is perfect for ejection angle, viscosity and exiting the atmosphere. Perhaps this is the magic 30 degrees whereas Australites were maybe ejected at c. 15-20 degrees??

Aubrey
www.tektites.co.uk



--- On Tue, 15/2/11, Yinan Wang <veomega at gmail.com> wrote:

> From: Yinan Wang <veomega at gmail.com>
> Subject: Re: [meteorite-list] World record 1, 250g tektite from Philippines??
> To: "meteorite list" <meteorite-list at meteoritecentral.com>
> Date: Tuesday, 15 February, 2011, 17:05
> Here's a big fish story for you all;
>
> About ten years ago I was visiting a mineral shop inside a
> park in
> china and they had a football (American football) shaped
> tektite
> slightly larger than a football. I was quite sure it was a
> tektite and
> not slag nor obsidian. Must've massed about 8-12 kilos. It
> was priced
> at the equivalent of $700 USD, but back then I didn't
> appreciate
> meteorites and tektites and thus I ignored it. Only
> recently did I
> realize the importance of it, oh well.
>
> -Yinan
>
> On Tue, Feb 15, 2011 at 7:28 AM, Aubrey Whymark <tinbider at yahoo.co.uk>
> wrote:
> > Hi
> >
> > Still seeking the new owner of a possible world record
> breaking tektite which came to light on 07 February 2011 in
> Paracale, Philippines. Very keen to know the true weight as
> the weight given by dealers here can be highly misleading.
> Certainly in the 900g to 1,250g range though and the weight
> estimate could well be realistic. You can let me know
> anonymously if you like - off-list. For the record the
> heaviest Philippinite is 1,070.54g and the heaviest of all
> tektites (excluding Muong Nong-type layered impactites) is
> either 1,070.54g (as above) or possibly a 1,200g Indochinite
> (shape is right, but might be a rolled/water worn Muong
> Nong-type).
> >
> > Also, I will be giving a presentation on tektites at
> Rizal Technological University on Boni Avenue in
> Mandaluyong, Manila, Philippines. It will be in the new
> building - Astronomy Centre at 9am (yes, very early) on
> Saturday 19th February. All welcome I am told.
> >
> > Regards, Aubrey Whymark
> > www.tektites.co.uk
> >
> >
> >
> >
> >
> >
> >
> > ______________________________________________
> > Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html
> > Meteorite-list mailing list
> > Meteorite-list at meteoritecentral.com
> > http://six.pairlist.net/mailman/listinfo/meteorite-list
> >
> ______________________________________________
> Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html
> Meteorite-list mailing list
> Meteorite-list at meteoritecentral.com
> http://six.pairlist.net/mailman/listinfo/meteorite-list
>


      
Received on Tue 15 Feb 2011 10:42:31 PM PST