Nautilus Minerals Inc. (TSX:NUS)(AIM:NUS) Deepwater seafloor drilling trials conducted at Nautilus Minerals' Solwara 1 Project in Papua New Guinea have confirmed the extension of high grade copper mineralisation beyond the project's previously identified massive sulphide system.
Nautilus' CEO, Steve Rogers, said the company is encouraged by the initial results from the trials.
"A number of milestones have been achieved," he said. "The drilling supports our view that the Solwara 1 resource is likely to extend beyond the previously identified limits and remains open at depth. The focus now is to optimise core recovery and drilling efficiency of the drilling system, to improve results so that we can enhance Nautilus' knowledge of the resource and other Bismarck Sea discoveries".
The trials involved 16 holes drilled at 13 locations approximately 1600 metres below sea-level and extending to a maximum depth of 45.2 metres below the seafloor.
Preliminary analysis of recovered drill core has shown the presence of high grade mineralisation at all sites, with four holes intersecting high grade copper well below the base of the previously modeled massive sulphide.
Copper grades of up to 30.5% were reported from individual sample intervals and results included an eight meter intercept averaging 12% copper. These results were based on hand held X-ray fluorescence (XRF) analyses.
2010 Trial Drilling Program
The drilling trials tested an improved seafloor drilling system, the Seafloor Geoservices' ROVdrill3.
Nautilus has been conducting the drilling trials since mid November on board the vessel Rem Etive, using the ROVdrill3 drilling system. TSMarine is providing the vessel, operating crew, Remotely Operated Vehicles (ROVs) and drilling equipment required for the project. The ROVdrill3 drilling system is a wireline diamond drill designed to recover up to 80 meters of 70mm diameter core. To date the following important equipment operational results have been demonstrated:
- The drilling rig can successfully land on the terrain typical of the Solwara 1 SMS system;
- It is functioning mechanically as designed, allowing the rig to collar and operate in ground conditions typical of the Solwara 1 mineralised system;
- It has demonstrated improved power performance over the previous ROV drills, enabling significantly deeper drilling. While the depth capability has not been fully tested, two holes deeper than 40 meters have been achieved.
- Core recoveries have been below design specifications and operational refinements are being implemented to lift recovery rates.
Nautilus announced the world's first NI43-101 compliant resource estimate for a Seafloor Massive Sulphide system at Solwara 1 in December 2007. The resource included:
Indicated Mineral Resource: 870 kt @ 6.8% Cu, 4.8 g/t Au, 23 g/t Ag, 0.4% Zn
Inferred Mineral Resource: 1,300 kt @ 7.5% Cu, 7.2 g/t Au, 37 g/t Ag, 0.8% Zn
Selection of Reported Intervals in Drilling Trials
Intervals were selected for reporting based on geological logging and handheld XRF analysis of pulverised quarter-core samples. XRF analysis of the pulps from samples within the selected intervals have generally returned greater than 3% Cu or greater than 9% Zn. Some lower-grade samples have been included in an interval where they were of similar material, compose only a minor portion of the interval, and if they did not reduce the overall grade of the interval to less than 3% Cu or 9% Zn. Intervals were broken where there was a length of core loss judged sufficient to lose continuity within the interval, or where there was a significant lithological or mineralogical change in the recovered material. Zones of core loss within an interval were assigned the average Cu and Zn grade of the recovered material either side of the core loss. Zones of core loss external to recovered material were not included in any calculated interval. All reported Cu and Zn values within the interval are length-weighted averages of individual samples.
Drilling Details
Core drilling for the 2010 drilling trial was undertaken using Seafloor Geoservices ROVdrill3, the next generation of Perry Slingsby's sub-sea diamond drilling rigs. All holes are drilled with less than a five degree variation from vertical. Drill core (69.9mm diameter) was processed entirely on the vessel, including geological logging, XRF analysis, geotechnical logging and geochemical sampling. All sampling and logging were performed under the supervision of senior Nautilus personnel and followed procedures first established in 2007 and updated for the new drilling program.
Treatment of Core Loss
Core loss was assigned to the top of the initial run of the drill hole and to the bottom of every subsequent run unless drill data or geological data suggested otherwise. This provides a conservative estimate of the thickness of mineralisation.
Sampling Procedure
Quarter-core samples are systematically cut from the drill core for geochemical analysis. As part of a documented QAQC program, certified reference material and field duplicates are inserted into the sample sequence. All material is prepared by an independent sample preparation facility onboard the vessel managed by Societe Generale de Surveillance (today, known as SGS). Samples are crushed and pulverised to provide a 150g pulp for certified analysis at an SGS facility in Australia. Samples are transported in sealed packages under a documented chain of custody. Final analysis results for samples from the trial drilling are currently awaited. The pulp residue that is not sent for analysis is returned by SGS to Nautilus for handheld XRF analysis.
Onboard XRF Analysis
A handheld XRF Analyser (NITON XL3t 900s GOLDD) is used to obtain indications of the grade of drill core. It does not provide the accuracy required to report assays. A XRF reading was taken on the pulp residues returned from the SGS preparation laboratory for each submitted sample, except in a small number of samples where residue material was not available due to a short sample interval. The pulp residue represents a well homogenised sub-sample of the drill core having been pulverised to 75 microns.
A suite of reference material, including certified reference materials are used to regularly test the calibration of the XRF analyser. These results indicate that the XRF tool is a reliable method for providing indicative results of the tenor of mineralisation.
The NITON XL3t 900s analyser is used by Nautilus in a calibration mode for rapid base-metal analysis at concentrations greater than 1%. Results may have low precision and accuracy in samples with base-metal concentrations of less than 1%.
Where pulp residues are not yet available for a sample interval, the XRF analyser is used to collect point-sample information on non-prepared drill core to provide guidance to Nautilus' geologists onboard the vessel.
Qualified Person
The exploration results reported in this announcement have been compiled under the supervision of Nautilus' Resource Leader Thomas Sant. Mr Sant a Fellow of the Geological Society of London, a UK Chartered Geologist and a registered European Geologist, has over 16 years experience in mineral exploration seeking hydrothermal systems, and is a qualified person as defined by National Instrument 43-101. Mr. Sant has reviewed and approved the technical disclosure contained in this news release.