Above is a data dump from what showed up in my QGIS - bit random but reflects the drilling and shows how the simplistic circa-50 and c-70m contours were generated from the passive seismic.
Passive seismic would not be my preference for a first pass geophysical tool. Geophysics measures properties, but only the drill bit (pre mr spock's tricorder era) will tell what is actually under the cover for economic elements.
For Luni (P2) gravity "worked", magnetics "don't", seismic tells depth to bedrock IMO. Neither gravity or magnetics seem to help ENR too much other than for broad targeting. Drilling on wide space fences from gravity is what has outlined the main zones with some guidance for depth from seismic.
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Transposing 2023 locations and schematic assay data onto the Passive Seismic section through the first Luni hole gives this rough image.
Selected assays for holes on section and projected 100m to section (both from west and east. Note while the red bars are shown vertical they are in fact inclined and hence will be shallower by a factor of approx. 0.8 which means most will end around the black dashed boundary shown.
Impressive set of relatively wide spaced (1-200m) assays over a wide zone. Perhaps a bit more patchy than the area being tested in the east but certainly going to receive more attention as priorities are modified IMO.
LURC23001
NSI
FR
TO
INTERVAL
NBx%
TREO%
1
1
LURC23002
61
92
31
4.59
1.68
1
2
LURC23003
incl
77
130
53
1.65
0.61
1
3
LURC23241
incl
41
52
11
3.12
1.05
1
4
LURC23241
114
115
1
1.09
0.17
1
5
LURC23242
36
70
34
2.92
1.05
1
6
LURC23242
124
128
4
1.54
0.3
1
7
LURC23243
NSI?
8
LURC23244
incl
54
59
5
1.15
0.4
1
9
LURC23244
and
77
99
22
1.18
0.73
1
10
LURC23245
38
130
92
1.17
0.52
1
11
LURC23245
and
82
90
8
2.55
0.87
1
12
LURC23246
incl
53
76
23
2.4
1.04
1
13
LURC23247
and
47
101
54
1.84
0.75
1
14
LURC23248
and
49
63
14
1.53
0.42
1
IMO the dashed black line and brown line are likely to be the transition zone from weathered to fresh. At least on this section.
Does the passive seismic help? Other than showing where bedrock may be deeper, perhaps not. Intersections like Holes 2, 242, 245 246 show long high grade intersections beginning well above the "contact" shown. If this is correct the passive seismic does not obviously reflect it. Perhaps some layering with transported in blue, some hints of zonation in the weathered profile, contact zone to fresh rock, variable zones in fresh rock (carbonatite vs complex vs country rock?) to a depth where passive seismic doesn't reach? Detail of the grade distribution down hole might reveal a different impression but not available from data released.
[As part of the MRE (and other studies?) WA1 will have done detail examinations of grade distribution. Perhaps even to see what the passive seismic was "saying".]
Passive Seismic is IMO a geophysical tool which does not add a huge amount of value. For WA1 it was useful to give an idea of depth to bedrock prior to the 2023 drill season. Possibly gave confidence that RC drilling would give good data.
How much did the survey cost? Would an aircore program on wide spacing have given similar data, plus early assay results, for an equivalent or only slightly more cost? Imagine ENR doing a passive seismic survey over Green and then going in with RC rather than aircore.
Gravity, magnetics, seismic, drilling are all useful tools. Multiple choices and limited budgets with no easy answer as to what to do in the early stages. WA1 are way beyond that now and are drilling out what will probably become a mine. Even this stage requires care not to overspend.
Western Mining stopped drilling at Olympic Dam after they had around a billion tonnes of resource. BHP are still drilling with the resource having reached 10+B and open at depth!
(20min delay)