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Gold/Mining/Energy : Winspear Resources -- Ignore unavailable to you. Want to Upgrade?

To: Mike Hermann who wrote (23970)	8/7/1999 12:14:00 AM
From: average joe	Read Replies (1) \| Respond to of 26850

That space diamond theory is twenty years old. The current theory is that meteorite bombardment of the earth 3 billion years ago either implanted diamonds in the mantle or the seeds of diamond in the mantle. Interesting discussion but it won't help teevee's mortgage problems. aj

To: Mike Hermann who wrote (23970)	8/7/1999 11:39:00 AM
From: Gee10	Respond to of 26850

Haggerty is not the first to discuss the subduction theory it was Smith et al back in 1974. John Gurney has written a few papers on this as well,("Diamonds deliver the Dirt", Nature etc etc..), Gurney's idea is that the carbon 13 ratios seem to imply that the carbon in a diamond has come from an organic source on the sea floor (high concentrations of Iodine in eclogitic diamonds also point to this source) of the oceanic plate. Now, as this plate subducts (pushed under the continental plate) it starts to move down into a very hot, high pressure zone beneath the continental plate. This cool subducting plate starts to de-gas, carbon dioxide is driven off. A series of Riedel shears develop and this is the mechanism that pushes this organic carbon into the diamond stability field (DSF). The DSF lies at the base of the continental lithosphere at around 180 - 200 kms below the earths surface and this, is where the diamonds are actually formed. This event is an Archean event (ie: took place at around 1.8 to 2.5 billion years ago). What this means, is that the diamonds have remained in the DSF since that time (and hence the expression "Diamonds Are Forever", I dont think De Beers had this in mind when they coined the phrase). The kimberlites/Lamproites have a variety of ages from around 1.8 billion (Guaniamo, Venezuela) to early cretaceous. After this along comes the Kimberlite (Pipe or Fissure) and as it travels through the DSF it picks up the diamonds and transports them to the surface. Thats why kimberlites/Lamproites and diamonds have really nothing to do with each other. The kimberlite is just a transport mechanism. Of course what this really!!!! means is that only the kimberlites that pass through the DSF have any chance of being economic. Locate the surface expression of the DSF and your in the money !!! The Holy Grail of diamond exploration. IMO this explains why so many kimberlites are barren. Have you never wondered why the prospective areas in the NWT were called the "Corridor of Hope", or as De Beers says "The Boulevard of Despair".