Hi Vaughn,
I assume you are located in Yellowknife? I suggest you stop by and get some info from a NWT government geologist with kimberlite expertise (perhaps Jennifer Pell?). Some data on Type II kimberlites may of of some help to you in your understanding of Snap Lake. Type II kimberlite is what is at Snap Lake, and is, as far as I know, the first publicly noted occurance of this type of kimberlite outside of South Africa (ie. Type II kimberlite is the host in dyke mines such as Bellsbank). Type II kimberlite is very low in volatiles so it does not erupt in a phreatomagmatic manner, as does Type I kimberlite, which is high in volatiles and consequently forms pipes near surface. Also, there is a crudely circular, bowl shaped "roof pendant" of metasediments and metavolcanics sitting in the granites around Snap Lake. I suspect the main (cone) sheet is situated at the contact between the granite and the bowl of overlying metasediments and metavolcanics. Most likely, the deep seated fracture(s) in granite which controlled emplacement did not penetrate or continue into the overlying metasediments. The contact between the granite and the overlying crudely bowl shaped roof pendant of metasediments was probably the main zone of weakness for the kimberlite to intrude into. Thus the infamous cone.
I concur with your comments on the north shore. Should the rim of the cone project to surface or near surface, and maintain the average thickness of about 2.7 meters, pittable tonnage will dramatically increase.
Keep up the excellent posting. Thats all for now.
regards,
teevee |
