Thank you, Bernd. You are a river to your fellow enthusiasts. Guido -----Original Message----- >From: Richard Montgomery <[email protected]> >Sent: May 21, 2013 5:21 PM >To: "Bernd V. Pauli" <[email protected]>, >[email protected] >Subject: Re: [meteorite-list] Chelyabinsk - slickensides or shock planes? > >Bernd, perfect summary. Thanks. > > >----- Original Message ----- >From: "Bernd V. Pauli" <[email protected]> >To: <[email protected]> >Sent: Tuesday, May 21, 2013 2:36 PM >Subject: [meteorite-list] Chelyabinsk - slickensides or shock planes? > > >Hello All, > >We had a similar discussion many, many years ago >(September 2001). Here's a short overview of our results: > >Summary: > >- broken surface is covered with glossy striations >- slickensides are identified by shiny mirror like surfaces > on an otherwise rough rock > >- they are the product of faulting in a rock body (as the crust > shifts, even slightly, the roughness of the rock tends to smooth) > >- slickensides are formed from the movement of rocks relative to each other > along fracture planes in fault zones > >- rub your finger along the grooves which make up the slickensides: > >* they feel rough when you move your finger in the direction opposite > to which the adjacent rock moved to form the slickensides > >+ they feel smooth when you rub in the same direction the adjacent rock > moved because it sheared off any microscopic projections or rough > edges as it moved > > => Not found in shatter cones! > >- slickensides are formed when opposite sides of rock faults > move in different directions > >- extreme pressure generates frictional heat as the rock faces are forced > past each other partially melting a thin veneer of rock at the interface > (result: smoothing of rough edges and a polished looking surface) > >- they are not formed by explosive breakup in the earth's atmosphere > (in such a breakup pieces would be flying apart from each other > whereas in slickensides the opposite is happening: the rock faces > are being forced against each other) but: see below ** > >- possible formation scenario: an impact event in space results in > movement of two adjacent parts of the stony meteorite relative to > each other along a preexisting fracture plane thus creating grooves > >- slickensides are polished, grooved surfaces that occur along shear planes > >- slickensides form along internal shear planes as opposite parts > move past one another > >- opposite parts rub against each other, their surfaces become smoothed, > lineated, and grooved > >- slickensides are formed when two planar sides grind past each other > >- slickensides can be created at the moment of breakup (not by the explosive > part of this breakup but rather when two parts of the meteorite grind past > each other along a pre- existing fracture - so-called shear rupturing) ** > >and here are some of the listees that participated in the discussion: > >Charlie Devine (started the discussion), Eric Olson, Robert Verish, >... to name a few. > >Cheers, > >Bernd > > > >______________________________________________ > >Visit the Archives at http://www.meteorite-list-archives.com >Meteorite-list mailing list >[email protected] >http://six.pairlist.net/mailman/listinfo/meteorite-list > >______________________________________________ > >Visit the Archives at http://www.meteorite-list-archives.com >Meteorite-list mailing list >[email protected] >http://six.pairlist.net/mailman/listinfo/meteorite-list
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