Talk:Diapir
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OK - more to do. Need to separate the cold diapiric stuff from the hot diatremic stuff. Later - :-) Vsmith 12:53, 6 December 2005 (UTC)
Yeah, especially as diatremes are not diapirs. Rolinator 00:50, 22 December 2005 (UTC)
- True - separation is planned - I'm kind slow though :-). I see you have made a diatreme page - good, but it too needs a bit of a re-write. Ah well, someday ... Cheers, Vsmith 02:52, 22 December 2005 (UTC)
The original paper by Mrazec described diapirs from Roumania where salt cores have 'pierced across' and breached an overlying anticline. The folds are assymetric, compressive in style suggesting some 'tectonic energy' driving the intrusion. These pierced folds are very different to Gulf Coast salt domes.
Further, I don't believe that 'bouyancy' is essential for intrusion. The driving force for any intrusion is the weight of the adjacent overburden/cover which 'sinks' into the source layer, driven by gravity. The one factor that allows this release of gravitational energy is the MOBILITY of the intruding material. For example, sea water will rise up a hole/crack in an ice floe, forming an 'intrusion', yet the ice is less dense than the water otherwise the ice would sink. Even mercury will rise up a hole in a styrafoam block floating on it.
Sure, salt is less dense than typical host rocks/overburden, but its most important property, for intrusion, is its ability to flow(especially if wet and hot)in response to very low stresses. It is a time-dependant fluid, or 'rheid', rather like pitch/bitumen (and glass, marble etc). A tombstone (see old marble examples) or window (see glass in old cathedrals) of rock salt will droop and flow like treacle, given enough time
The lavalamp is a poor example of a 'diapir'.
A mobile intruding material that is LESS dense than the overburden simply has the potential to EXtrude (the cover sinks completely). If more dense, the intrusion will penetrate the cover to some point, then cease.
This is especially the case in extensive terrains where intrusion can be 'permitted' by tensional zones in the cover; even 'pull aparts' in compressive zones.
Forget about 'low density'; mobility is the key to intrusion.
Perhaps we should forget about 'diapirs' and just call them 'intrusions (salt, granite, shale, mud, breccia etc)'?
Cheers tmount 00:41, 27 February 2007 (UTC)
