Rubicon Minerals Corporation (RMX:TSX | RBY:NYSE-AMEX) has provided a NI 43-101 compliant inferred mineral resource estimate for the F2 Gold System, part of its 100%-owned Phoenix Gold Project located in the heart of the prolific Red Lake Gold District of Ontario.
The inferred mineral resource estimate was prepared by Geoex Limited. ("Geoex") based on 166,886 metres of diamond drilling in 237 drill holes carried out between February 27, 2008 (the date of the initial discovery) and July 31, 2010. The estimate does not include approximately 41,702 metres of drilling completed since July 31, 2010. The inferred resource estimate was prepared using the polygonal calculation method (see below for details) which, in the opinion of Geoex, is the appropriate method and is typically used for this type of deposit. The cut-off used is considered to be an economically reasonable estimate of breakeven mining costs.
"We are very pleased with these initial results. They demonstrate that the F2 Gold System is already a significant sized gold deposit. Importantly, the gold grade of 20.1 g/t gold is high compared to most major gold deposits around the world and is consistent with the overall Red Lake camp average grade, which is Red Lake's key advantage. Our objective now, through our ongoing delineation program is to upgrade part of this large inferred resource, move towards development and to continue to expand the gold system. Underground development on the project has already cross-cut mineralized zones at the 305 metre level and delineation drilling is underway.
Geological Potential
In addition to the above referenced inferred resource estimate, Geoex carried out an evaluation of geological potential based on an analysis of the distribution of current drilling (strike length of 898 meters as of July 31,2010) and opportunity for infill and expansion drilling to depth. The system remains open along strike and to depth beyond the current limit of drilling.
The geological potential is based on the projection and extrapolation of the inferred resource present between 0 to 500 metres below surface as this area is considered well drilled and contains an inferred resource of 3,400,000 tonnes containing 2,680,000 oz at 24.4 g/t or 0.71 oz/ton. In the area between 500 and 1500 metres below surface, drilling is wider spaced and thus large parts of the system in this area have not been adequately drill tested, however, in the opinion of Geoex, based on a review of project data, experience from elsewhere in Red Lake and general observations on lode gold deposits, the grade and tonnage profile of the area above 500 metres is likely to be replicated to depth with additional drilling.
The potential tonnages, grades and ounces set forth in the analysis of geological potential are conceptual in nature, as there has been insufficient exploration to define a mineral resource and it is uncertain if further exploration will result in the target being delineated as a mineral resource.
"From the early days of the discovery, we have always recognized that we are exploring a very robust and large mineralizing system, which is why we have dedicated significant drilling efforts to the 9X target area. As suggested by Geoex, the current 4.01 million ounce inferred gold resource may be only a small part of the overall gold potential of the F2 Gold System. Large areas remain to be infill-drilled and the system is open in all directions. We should also point out, we own 40% of the exploration real estate in Red Lake giving us a unique opportunity to find the next F2 Gold Deposit," stated David Adamson, President and CEO.
Geoex will prepare an NI 43-101 compliant technical report in respect of the inferred resource estimate and geological potential discussed in this release which Rubicon will file on SEDAR within 45 days of the date this release was disseminated, and plans to complete a Preliminary Economic Assessment in respect of the F2 Gold System by the end of Q1, 2011.
Resource Calculation Methodology
The construction of the polygonal and block models was a product of collaboration between Rubicon and Geoex. Rubicon personnel included Matt Wunder P.Geo, V.P. Exploration and Eric Hinton P.Eng., Project Manager. All data in the resource evaluation were reviewed by Geoex with Mr. Peter George of Geoex assuming responsibility for the resource and geological potential estimates upon which the statements reported herein are based.
Polygonal Resource calculation
Source assay data were audited by a third party consulting firm (IoGlobal) specializing in data management and QA/QC analysis and composite intervals were calculated utilizing a minimum three and also a five gram cut-off and minimum 10 gram times metre product for all F2 system data to July 31, 2010. No top cut was applied to the data because, in the opinion of Geoex there is insufficient geostatistical data to properly determine an accurate top cut value at this time. The X, Y and Z centroid points were calculated and horizontal thickness for each composite interval was calculated utilizing a set of east-west cross sections (local mine grid). The composite intervals were classified by geological unit and centroid points for each composite interval were plotted on long sections for each geological domain utilizing AMine software. Individual zones were then interpreted in AMine.
The interpretation is largely based on a series of detailed cross sections confirming geological continuity vertically down dip and along strike (mine grid north-south). Polygons were plotted on long sections for each sub zone with ellipse parameters for the inferred resource of 75 metre vertical radius and 37.5 metre horizontal radius. Polygons were clipped where overlapping, clipped where the claim boundary and 15 metres below where the lake bottom surface was contacted. Polygon areas were calculated for each centroid point, horizontal thickness was applied to determine the volume, a specific gravity ("SG") of 2.85 g/cm3 was applied, being derived from the average SG in preliminary metallurgical studies (see news release dated October 19, 2010). The volume of each polygon was calculated and assigned a gold grade. The sum of the polygons constitutes the inferred resource.
Block Model calculation
In addition to the polygonal resource calculation, as a means of validating the inferred resource estimate by an independent method, a block model was calculated utilizing Surpac software resulting in 5,830,000 tonnes, 3,210,000 ounces at 17.2 g/t or 0.50 opt. The block model results are within 6.7% of the tonnage, 17.1% of the contained ounces and 24.9% of the grade of the polygonal estimate (6,200,000 tonnes, 4,007,000 ounces at 20.1g/t gold or 0.59 opt). While Geoex does not consider the block model the most appropriate method for this type of deposit, the results are considered to provide strong supporting validation for the preferred polygonal estimate reported above. It should be noted that the block model results do not differ significantly regardless of whether a northeast (East Bay trend) or northwest (F2 trend) oriented search ellipse is used in the block model.
Data were audited prior to completion of the block model. For this inferred resource estimate, the data were treated as one domain. Assay data were composited at 1.0 metre intervals (no top cut was applied) and variogram analysis was completed. Two times the variogram range was utilized for oriented search ellipse parameters (list parameters) for the inferred resource calculation. A block size of 2m (E-W) by 4m (N-S) by 12m (vertical) was selected through an optimization process. Data were constrained by the lake bottom surface, the claim boundary and a western boundary was included to exclude any unrelated drilling carried out prior to February 2008. A SG of 2.85 g/cm3 was utilized.
Source: Rubicon Minerals Corporation