geology 101
posted on
Apr 17, 2011 05:03PM
Little has been noted about the geology for the BL site other than that provided on the web page and in the NR's. Mineralization is basically found in a meta-conglomerate that is part of the Timiskaning sediments which are believed to be Archean in age which basically implies the oldest rock from the Precambrian, greater then 570 million years old. Info from one NR indicated the meta-conglomerate, where the drilling is being completed dips 50 degrees to the northeast so the intersections of mineralized zones are approximately true widths assuming the angle of the hole is about 40 degrees.
From Figure 1 on the web page for BL the mineralized bed can be traced to the northwest where it starts to bend north and then to the east. If one draws a line from the drill site across to the north side of the Borden Lake Horizon [BLH] and place all the beds, from the drill site, at a 50 degree dip and then connect thoes that show on the north side you would have a very simple SYNCLINE structure. In other words the known BLH on the southeast side goes to depth and back up the other side, a big U. The suspected depth to the bottom of the syncline is probably about 1500 to 2000 m assuming the BLH on the north side dips south at 50 degrees.
So what, you might say, well for starters the gold intersected to date appears to be associated with both pyrite and pyrrohite, the sulphide minerals. Figure 1 shows numerous AEM conductors around the NOSE of the fold, on the north limb and in the meta-sediments below the BLH. In addition the BLH around the Nose and the north limb appear to be thicker then where PRB is now drilling. The horizon under investigation now also goes to depth, how deep we don't know but I suspect it will be 1000 m plus, but will it contain gold at this depth. One point regarding the bottom of the syncline, this is where I would anticipate more fractures then on the sides of the syncline. Will the other identified AEM anomalies in the meta-sediments contain gold???
The biggest question since I believe there is lots of formation that might host gold is where did the gold come from as it is difficuly to believe both the gold and sulphides could have been part of the conglomerate make up as placer material. In the early 1900's geo's classified mineral deposits according to whether they were products of mechanical concentration or chemical. As one might suspect there is lots of controversy but migrating hydrothermal fluids with their load of minerals that move into areas of low temperature and pressure where structural and environmental conditions are correct for deposition might be one answer. Can areas of the BLH that have no sulphides contain gold, only the drill can tell us that.
One more question and prehaps PRB or others can answer; how does the granitoid, a fine grained granite and the amphibolite impact the mineralization? There is possibliliy no answer but fundamentally minerals are transported and deposited, a source is needed.
Something to ponder when next weeks trading gets underway. One point i'm sure off, there is a lot that we don't know now and so much more to learn.
All my rambling for a Sunday afternoon, jmho. Please do your own DD.
mh