Talk:Salt tectonics
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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
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)
Retrieved from "http://en.wikipedia.org/wiki/Talk:Diapir"203.3.197.249 (talk) 21:12, 9 April 2008 (UTC)
