Distributed MT/DCIP Geophysical Surveys at Confederation Lake

Tribute Minerals- Dixie Lake

 

Introduction

As part of the Ontario Minerals Exploration Technologies Program (OMET), Quantec performed a dem-onstration survey of a new deep exploration geophysical technology (Titan) for Tribute Minerals Corp. at their Dixie and Ben Lake properties, near Red Lake, Ontario. The primary objectives of this demonstration survey were to showcase a new technology to the mining sector.

1. To demonstrate and evaluate the Titan system’s capability of mapping geology and detecting anomalous sulphide mineralization (massive or disseminated) in areas of thick overburden and Paleozoic cover within Ontario’s complex environment.
2. To demonstrate Titan system capabilities within a relatively unexplored green-fields environment.
3. To determine within the survey area if the new geophysical results support any additional drilling for South Bay -type volcanogenic massive sulphide deposits.

The Titan-24 system acquires three types of geophysical data, magnetotelluric (MT), direct current (DC) resistivity and induced polarization (IP). The MT and DC both measure the same physical property, resistivity, in two different ways, whereas the IP measures the chargeability, which is an indicator of metallic mineralization, either massive or disseminate.

Confederation Lakes Belt, Red Lake Area, Northern Ontario. The Dixie property contains several known areas of mineralization including a mineralized marker horizon, containing copper and zinc values in chalcopyrite and iron-rich sphalerite, respectively, which appears to extend for more than thirty kilometres to the east and northeast. The Dixie survey area overlain by a thick (10-50m) layer of conductive overburden, which has significantly limited exploration by conventional geologic mapping and geophysical methods, requiring a reliance on costlier diamond-drilling. The style and tenor of mineralization is similar to the Kidd Creek, Mattabi and Geco Mines, and hosted the past-producing South Bay Mine on Confederation Lake adjacent to the Tribute’s Boomerang Lake property.

 

Dixie Regional Geology Titan Survey Area

Plan view of Dixie project area, showing Titan Line locations and local geology

 

The Titan-24 approach has three valuable applications for property evaluation:

1. Guiding drill target designation - improving success rates
2. Sterilizing ground - drilling budgets not wasted
3. Accountable and scientific Re-analysis of geophysical results during and post-drilling to minimize follow-up holes.
   
   

The OMET project followed a relatively straight forward approach.

1. A 3D Earth model was constructed which best represented the known geology underlying the survey area, based on available geologic and drill hole evidence.
2. The results of each geophysical inversion stage were then reintroduced into the Gocad model for easy comparison against the geology and diamond drilling, as well as for simple query analyses.
3. With the 2D addition of resistivity and chargeability reference values, obtained during the physical property analysis stage, the Gocad model is ready for the future constrained 2D inversion stage, as well as for 2D-3D model sensitivity analyses.

 

 

The survey consisted of five (5) profiles on each property, for total of 10 lines, each 2500-2600 m long, separated by 200m and with 100m-station pit. These lines are oriented approximately N-S and are designed to cross-cut the known geology, which is believed to be steeply dipping.

Initial, unconstrained (not geologically referenced) 2D inversions of Titan data demonstrate excellent correlation between the known geology, buried beneath up to 50m of clay overburden, and linear zones of resistivity low and chargeability high, which characterize the volcanogenic massive sulphide zones which are sought after. DC resistivity and IP chargeability 2D inversion cross-sections specifically identify coincident polarizeable and conductive bodies, as well as fault-structures, at a relatively high resolution, owing to the high-density data acquisition, within the upper 350-500m of rock. The IP parameter, in particular, is useful in discriminating between resistivity zones relating to either non-mineralized, fault-fracture zones and mineralized, massive to disseminate sulphide or graphitic bodies ­ some of which have remained undetected using more conventional EM and magnetic techniques.

 

Titan Chargeability information provides information on the sulphide distribution in the surface to 800 metre range. Within the survey volume, drill testing of several of these features provided confirmation of non- economic sulphide intersections of 8 -12 metres thickness at depths of 250 metres

 

Dixie - 2D MT EVA-PW Resistivity Inversions (in 3D Gocad Model)

The most noticeable signatures observed in the MT results are the large, low resistivity features which are consistently detected along all profiles across the Dixie 18/20 horizon, near 1000N, at depths below 1km.

 

Ben Lake - 2D MT EVA-PW Resistivity Inversions (in 3D Gocad Model)

Ben Lake MT Inversions in the Earth Model indicate that the Ben Lake stringer zone does not have an extensive root in the survey volume. This type of zone, due to its extensive size and good assay returns has always begged additional drilling to find the source. Now the ground is sterilised and the project can finally move on. Additional drilling will not be required in this survey volume.

 

Dixie - Anomalous 2D IP and MT Isosurfaces (in 3D Gocad Model)

 

Dixie - Anomalous PW 2D MT Isosurfaces (in 3D Gocad Model)
Drill holes & sulphide intercepts

Iso surfaces are created to highlight specific areas of interest from the Titan survey. Anomalous 3D IP / MT Iso-surfaces in Gocad Model at Dixie provide excellent 3d understanding of potential sulphide distribution and relationships.

 

Survey Results

Specific to the Dixie and Ben Lake properties the system responded as follows:

• DCIP has proven to be the best indicator of anomalous conductivity and chargeability relating to volcanogenic and metasedimentary sulphides within the upper 350-500m of bedrock. Benefiting from superior shallow resolution, due to high redundancy data acquisition, and, thanks to the IP parameter, a greater sensitivity to more weakly mineralized/conductive Zn-rich bodies, the DCIP results,
• AMT/MT has proven to be the most reliable indicator of geologic structure and deep conductivity along the targeted felsic and metasedimentary units. Benefiting from superior depth-penetration (>1.5 km+) and advanced interpretation algorithms, the MT inversion results, in particular, have identified deep anomalies of interest within the Dixie 17/19 and Dixie 18 horizons. The deep MT anomalies at Dixie appear to be the most compelling signatures identified in the Titan 24 surveys at Confederation Lake
• At Dixie, there are five high-priority deep anomalies (>500m) associated with 1 to 2 distinct tar-gets along strike identified within the survey volume. All are situated along the Dixie 18 horizon. This includes a deep conductive anomaly identified along all lines at a 1km depth. A series of moderately buried (>100m) DCIP anomalies, associated with and lying below the known Dixie 19 Zone, have already been drill-proven for sulphides and probed with borehole TEM.
• A larger number of high priority signatures have been identified within the near surface (<250m). These anomalies tend to be small to moderate size (<200x300m) but they represent combined high chargeability, DC and MT low resistivity.
• In the mid depth range (250-500m) there are several additional high priority anomalies, which have been identified using primarily the IP chargeability, DC and MT resistivity.

Summary

1. This survey successfully demonstrates the capability of the Titan system to map geology and anomalous mineralization below thick overburden. Anomalies and targets have been identified to depths in excess of 1.5 km.
2. The Titan system was capable of identifying known mineralized resources as well as detecting additional exploration targets in a “green-fields” type environment. Integrated geologic and geophysical interpretation provides more information prior to drilling, thereby allowing drill programs to be more focussed.
3. The interpreted results require evaluation against the known drill and downhole EM database. Any un-drilled high priority targets should be evaluated for future drilling.
4. Additional DCIP and MT surveys are recommended, along strike from the current survey areas, where the mineral potential has not been fully drill-proven below 150m – below the penetration depth of conventional surveys. In addition, the application of this penetrating deep technology will be useful for delineating potential structure and sulphides associated with gold mineralization along the belt.
5. The survey system has overcome technical issues that significantly hamper other more traditional means of deep exploration. The spectacular results demonstrate that this new technology provides the mining sector with a means by which to essentially see deeper and clearer than previous capabilities allowed providing focused deep drilling.

• For information on the Titan system see Titan 24
• Download the complete executive summary.
• For more information on Tribute Minerals ongoing Confederation Lake Program please visit www.Tributeminerals.com