Worth reading and re-reading and re-reading and ....
Author: jspec -- Date:1999-04-03 18:15:14
Subject: Spatial Sheet Geometry
It has been ably demonstrated by WillP that at the relatively slight down-dip of the Snap Lake dyke(sill,cone sheet or whatever)that the true thickness of vertical drill hole kimberlite intersections varies only very slightly from the reported thickness-3 percent or less not the 10 per cent stated by WSP- as cosine 15 degrees is 0.97.This for a 15 degree down-dip. This analysis by WillP should impel WSP SHs to closely examine the math and conclusions of the WSP technical staff and by extension to all resource stocks we follow.
In a previous post I had questioned the conclusion of WSP that results indicate multiple sheets and a depth anomaly in that CL98-17(L16) hole is 150 meters deeper than what should be expected. Based on their stating of a 23 dip on the southeast and a warped sheet,I postulated a warped bowl shape to this deposit. Not so. Led down the geometry primrose path by accepting their statements.
The calculations and conclusions that follow will demonstrate,I think, a spatial view superior to flower petals and be suggestive of and reinforce expectations of great tonnage at Snap Lake. In a uniform decline the distance from the beginning of the down-dip to the drill hole,the hole length and the decline line form a right angle triangle. Slde opposite the decline angle(the depth side) divided by the horizuntal distance from the angle equals the tangent of the triangle.In this treatise there is no intent to denigrate the abilities of the technical staff of WSP.IMO they are highly capable,but in the arena of fact discovery pertinent observatiobs can come from diverse directions.
In following math and conclusions herein it should be noted that the scale of the two maps(1/26 and 3/26) is different. Tangent 12 degrees=0.213,tan 13 derees=0.231, tan 14=0.25,and tan 15 degrees equals 0.268. To begin:
1.Cluster C(1/26 map).The down-dip from C to hole 98-17(L16) is not the implied 23 degrees.The distance to CL98-17 is about 1700 meters. The average depth of intersections in cluster C below lake surface is about 50 meters(per telephone conversation with WSP). Depth of L16 hole intersection is 478 meters.478 minus 50 is 428,dividing by 1700-0.25 or 14 degrees down-dip from C to CL98-17. Hence the WSP statement that the 478m depth 150 meters below expectation suggests a second sheet with drill missing the 1st sheet or a change in attitude(decline) is not corroborated.
Analyzing 98-17 from another angle(no pun intended),the NW peninsula(NWP)-the center of NWP is about 2000m from L16 hole. 478 over 2000 is 0.23 or 13 degrees. Even using a 1850m distance the tangent is 0.258-less than 15 degrees. Where is the 150m discrepance? Nowhere. Change in attitude is contraindicated.
2.Cluster B. B distance from CL98-17 is about 1850m,depth estimated at 40m(farther up-dip than C).478 minus 40=438 438 over 1850=0.237 or about 13.5 degrees.
3.Cluster A.Distance ca.2050 maybe 2100. Depth 25-30m. 448 divided by 2050=0.21 or 12 degrees down-dip to CL98-17.
Conclusion. Cluster A,B,C analysis indicates a remarkably uniform down-dip consistent with that from NWP.We can construct a rough estimate tangent chart that will work to the source depth which is certainly greater than 478 meters. And quess the approximate source site. In l16/L17 near midpoint of 16/17 line.Distance about 2300 meters from edge of deposit.
Conclusion. The dyke is bowl shaped. Considering the North Shore cluster of 3 in the equation the bowl is circular or nearly so.If elongated, it is only slight with the axis of elongation to the northeast.
Conclusion. There will be dyke extensions to north,northeast,east,etc. This bowl is not about to be chopped off in mid-bowl.Tonnage implications? HUGE. Like that postulated long ago by some. HUGE HUGE HUGE The Pix2.3km squared or 16.6 square kilometers is in sight.
Conclusion. The rim of the bowl goes thru the N/O,12/13 intersection region and off map to the north(Q/R16/17) circling back onto the map at O21 and offmap again to L22 on the east and soforth.
CHART
Distance from Rim Depth Distance from Source
200m 50 2100
500 115 1800
700 175 1600
1000 230 1300
1200 275 1100
1400 320 900
1500 345 800
1750 405 550
1800 415 500
2000 460 300
2100 480 200
2200 505 100
2300 530 0
Employing 13 degrees.Source depth estimate will vary depending on angle used.500 to 525.Using the chart. {f working down-dip use Rim distance.Up-dip use Distance from source column.Source depth at 12.5 degrees is 510 meters.
SUMMARY
Whatever the sheet terminology employed this a bowl shaped body.The western half is quite symmetrical. The eastern half is blue sky. Looking from anywhere on the rim on straightline through the source to opposite rim is about 4600m or down-dtp/updip and strike length is also about 4600 meters.
With thanks to WillP for crystallizing a growing feeling not to accept the conclusions of the WSP staff w/o checking. BAH to flower petals.
regards
jspec
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