Key points
- Placer Dome drilled and sampled the Solwara 1 prospect in January and February 2006 in about 1,600 metres of water within EL 1196, Papua New Guinea.
- Surface mapping defined two sulphide outcrop zones measuring 900 and 400 metres long with across-strike widths of 80 to 200 metres.
- Forty-nine surface samples averaged 15.5 g/t gold, 9.6% copper, 138 g/t silver, 5.1% zinc, 0.8% lead and 199 ppm molybdenum, with the highest sample grading 32.7 g/t gold and 23.9% copper.
- Drilling intercepted sulphide up to 19 metres below the seabed, including 11.6 metres at 9.1 g/t gold and 13.1% copper in hole SUZDD028, with 28 of 34 holes hitting significant mineralization.
Nautilus Minerals Inc. has received from Placer Dome Oceania Ltd. the results of its first drilling and sampling program at the Solwara 1 prospect. The drilling and sampling program was undertaken by Nautilus’s farm-in partner, Placer Dome, during January and February of 2006, in water depths of approximately 1,600 metres on the sea floor at the Solwara Project in EL 1196, within the territorial waters of Papua New Guinea.
This work has defined two zones of seabed sulphide outcrop 900 and 400 metres long, each with outcrop widths varying from 80 to 200 metres. Surface sampling of these zones has provided average metal grades of 15.5 grams per tonne gold, 9.6 per cent copper, 138 grams per tonne silver, 5.1 per cent zinc, 0.8 per cent lead and 199 parts per million molybdenum from 49 samples. The highest-grade sample returned 32.7 grams per tonne gold, 23.9 per cent copper, 92 grams per tonne silver, 0.2 per cent zinc, 0.08 per cent lead and 590 parts per million molybdenum. These results compare well with the Placer Dome dredge sampling program completed in 2005, which returned average grades of 15.5 grams per tonne gold, 12.2 per cent copper, 256 grams per tone silver and 4.2 per cent zinc from 39 sulphide samples.
SOLWARA I PROSPECT — FEBRUARY, 2006, SURFACE SAMPLING SELECTED RESULTS
Surface sample Au Cu Ag Zn Pb Mo
number Description (g/t) % % % ppm
Surface 16 Small chimney 4.5 27.5 39 0.3 0.1 100
Surface 09 Sulphide piece 7.2 26.5 66 0.9 0.2 109
Surface 03 Sulphide piece 32.7 23.9 92 0.2 0.1 590
Surface 28 Small chimney 40.8 9.1 151 0.7 0.3 104
Surface 14 Large chimney 36.1 18.2 172 6.3 0.5 142
Surface 12 Large chimney 38.3 18.7 178 1.6 0.5 229
Surface 29 Small double
chimney 3.0 0.6 226 35.0 5.6 16
Drilling returned significant sulphide intercepts up to 19 metres below the seabed, with a best intercept of 11.6 metres at 9.1 grams per tonne gold, 13.1 per cent copper, 13.6 grams per tonne silver and 77.9 parts per million molybdenum, with an average sample recovery of 58 per cent from hole SUZDD 028 which is open at depth. The highly variable and friable nature of the sulphide material presented significant challenges for the ship-based drilling system used by Placer Dome and resulted in poor sample recovery (average of 47 per cent).
SOLWARA I PROSPECT – FEBRUARY 2006 DRILLING SELECTED INTERCEPTS
Drill From To Interval Au Cu Ag Mo
Hole No. (m) (m) Recovery Description (m) (g/t) (%) (g/t) (ppm)
SUZDD002 0.0 15.2 7 Massive suiphide 19.2 4.8 5.0 21 113
with minor altered
volcanics hole
stopped in
massive sulphide
SUZDD004 0.0 14.3 14 Massive suiphide 14.3 3.7 8.5 11 91
and silca
alteration
including 0.0 6.5 12 Massive suiphide 6.5 6.2 14.4 18 141
hole stopped in
sulphide
SUZDD009B 0.0 13.0 42 Interbedded suiphide, 13.0 6.9 6.7 25 88
barite and
volcaniclastic
hole stopped in
sulphide
SUZDD0012A 0.0 16.8 24 Massive suiphide 16.8 5.4 6.8 16 175
hole stopped in
massive sulphide
SUZDD028 0.0 11.6 58 Massive and 11.6 9.1 13.1 14 73
unconsolidated
sulphide, barite,
minor clay altered
volcanic hole
stopped in massive
sulphide
SUZDD031 0.0 10.0 27 Massive suiphide 10.0 7.6 8.6 53 79
hole stopped in
massive sulphide
SUZDD034 0.0 17.5 64 Sediment, friable to 17.5 4.7 5.6 24 93
massive sulphide,
minor barite
including 3.0 15.5 64 Sediment, friable to 12.5 6.1 7.6 23 112
massive sulphide,
minor barite
Nautilus chief executive officer, David Heydon, comments: “Completion of this sampling represents a significant leap forward in our goal to be the leader in sea floor mining. The ROV-deployed sonar and camera program has outlined a significant area of sulphide exposed on the sea floor and sampling of this material has shown it contains high grades of both gold and base metals. Sampling of these zones returned average metal grades of 15.5 grams per tonne gold, 9.6 per cent copper, 138 grams per tonne silver, 5.1 per cent zinc, 0.8 per cent lead and 199 parts per million molybdenum, with the highest grade sample returning an impressive 32.7 grams per tonne gold, 23.9 per cent copper, 92 grams per tonne silver, 0.2 per cent zinc, 0.08 per cent lead and 590 parts per million molybdenum. Nautilus Minerals plans to focus activity on this high-grade zone and has commenced baseline environmental studies as the basis for potential permitting for a mining lease.
“Considerable sulphide thickness (up to 19 metres) intercepted in drilling indicates that there is significant depth extent to these systems, particularly when you consider that there is also up to 20 metres of chimney rising above the sea floor. Twenty-eight of the 34 holes intercepted significant mineralization: an impressive strike-rate for the first drilling campaign in a new belt. Many of the holes were terminated in sulphide, when sample could no longer be recovered, and some holes intercepted massive sulphides in areas where there was no surface sulphide exposed, indicating further potential laterally and at depth. We plan to better delineate this potential by deploying further drilling and geophysical techniques.
“The cutting tests demonstrated that the friable sulphide material, which lead to the poor drill recovery is readily disaggregated using existing rock-cutting technology. This supports our sea floor mining concept.
“We are very encouraged with these results from what is the first prospect that we have investigated within our tenement holdings. We have at least a dozen other areas of sulphide mineralization that have been discovered by marine scientists in the last 15 years, within our extensive tenement holdings in PNG. We look forward to exploring these and other areas in future programs.”
Surface (chimney) zone
Detailed bathymetric mapping using multibeam sonar, has mapped two zones of chimney outcrop totalling 1,300 metres in strike with an across-strike width of 80 to 200 metres. The chimney zones are readily discernable as areas of extreme topographic variation with individual chimney relief up to 20 metres. All chimney zones were visually inspected to confirm the presence of sulphide outcrop using a remote operated vehicle (ROV), which was also used for sampling.
The bathymetric map was generated using a Reson 8101 multibeam sonar system mounted on the ROV and operated by the experienced marine survey company Geo Century of Newfoundland, Canada. The sonar system was flown at a height of 50 metres above the sea floor along lines 50 metres apart, achieving a survey accuracy of better than one metre. The area covered by the survey was 1.6 by 1.1 kilometres.
Pieces of sulphide rubble up to 180 kilograms were collected from the sea floor using a manipulator arm mounted on the ROV. Samples were either placed in a sample basket or box on the front of the ROV or held in the claws of the manipulator arms and brought to the surface, where they were then processed on board the ship. Sample selection targeted material that was considered representative of the chimney field. In a number of locations multiple samples were taken and assayed.
Surface samples were of varying shapes and sizes, but most comprised pieces of sulphide rubble. A total of 51 representative subsamples, each of between 0.5 kilogram and two kilograms, were taken from these larger samples. Smaller pieces were halved using a diamond saw, and representative slices were taken from larger pieces. The remaining portions of each sample were retained for reference purposes.
Drilling
Thirty-four holes were completed for a total of 355 metres.
Coring operations were performed by Seacore Ltd., an England-based company, and a recognized expert in deep-sea core drilling. Core recoveries in the drilling program were low (averaging 47 per cent) due to the friable and highly variable nature of the sulphide material and the drilling technique, which used a surface vessel to deploy a 70-tonne drill pipe 1,600 metres to the seabed below. Nautilus is developing ROV-based drilling equipment which should produce improved bit control and better core recovery in future programs.
Many of the holes were terminated in sulphide when sample could no longer be recovered indicating further depth potential. Drill holes were vertical and core diameter was 65 millimetres, approximately equivalent to HQ size.
Due to the lower than expected recoveries, drill core was sampled on a drill-run basis rather than per metre. Thus (for example), for a drill run from three to five metres (two metres total drilled) with only 40-per-cent recovery, the 0.8 metre of recovered material was considered a single sample representing the interval three to five metres, and subsampled on that basis. A total of 287 drill core samples were submitted for analysis.
All core subsamples submitted for analysis were half core, with solid pieces halved longitudinally (parallel to the core axis) using a diamond saw, and loose material halved longitudinally using a spatula. The remaining material has been stored for reference.
Cutting trial sample
Approximately 15 tonnes of material was recovered from 13 sites by Placer Dome technical services engineers using an off the shelf pick cutting head situated on a marinised excavator arm attached to a 200 hoursepower ROV. The ROV was leased from and operated by Canyon Services for Placer Dome’s drilling and sampling operation. Samples were delivered to a bin on the ROV through a suction pump driven by the ROV assembly. There were considerable problems with this pump which was not sufficiently powerful, resulting in breakdowns during the cutter trials, and questionable sample recovery, particularly of the more dense material. Samples were hoisted to surface then the bin was emptied into drums on the deck of the ship.
The primary objective of the cutting trial was to test cutter configurations, on a range of rock types. As such the cutting sites were chosen as much for ease of access to varying rock types as they were for their proximity to massive sulphides. Because the sampling material was not the prime selection criteria for the cutting trials, the samples collected, a mix of mound material, chimneys and altered volcanics, are not necessarily representative of the Solwara 1 Prospect’s mineralized areas.
In total 13 sites were sampled with 34 drums of material being recovered. Each of the 34 barrels of material recovered during the cutting tests was subsampled. Due to the nature of the material, subsampling was a simple spear-grab sample taken from the upper half of each barrel: therefore, the subsamples might not be representative of the material in each respective bin.
Sample custodianship
All sampling, sample handling and analysis was completed under the supervision of Placer Dome. Sampling was carried out aboard the vessel DP Hunter, while at sea. All subsamples were placed into prenumbered calico bags. The bagged samples were then subsequently placed in groups of five into larger polyweave bags. The polyweave bags were sealed with security tags, which were then signed by the supervising geologist on site at the time. The bags were then placed into 120-litre polyethylene drums for transport to the laboratory.
Laboratory analysis
All analyses were carried out by ALS Laboratory Group in Brisbane, Australia. ALS operates quality systems based on international standards ISO/IEC17025:1999 “General requirements for the competence of calibration and testing laboratories” and ISO9001:2000 “Quality Management Systems — Requirements.”
QA/QC
External certified geochemical reference materials prepared by Geostats Ltd., of Perth, Western Australia, and independently tested, were interspersed at regular intervals between the 372 samples submitted for analysis. These reference materials comprised “Standards”, with known and statistically tested concentrations of the major base and precious metals, and “Blanks”, with extremely low concentrations of the major base and precious metals. Standards were submitted approximately every 10th sample. Blanks were placed with a similar frequency, but specifically after a drill core sample that appeared visually to be of higher grade. This frequency resulted in approximately 20 per cent of all samples submitted consisting of standards and blanks. Evaluation of these standards and blanks indicate that the quality of the analyses are within acceptable limits.
Qualified person
These results have been compiled under the supervision of Michael Johnston, vice-president, corporate development, of Nautilus. Mr. Johnston is a member of the Australasian Institute of Mining and Metallurgy, has 20 years experience in mining and exploration geology, and is a qualified person as defined under NI 43-101. He consents to his name being used in this release.
