AU33West Gold project (HEBERTO target)
About 350 km NE of Matagami, near the James Bay EM-1 dam, the AU33West project totals 497 mining cells for 262 sq. km. Access to the project is by Hydro-Quebec gravel road linking Nemaska/Eastmain-1/LaSarcelle.
The AU33West property is located within the Lower Eastmain greenstone-belt wrapped around the Mistumis tonalite-granodiorite-diorite pluton of the Archean LaGrande Sub-province. The AU33West project hosts a regional east-west striking deep structure (Chain Lake Break) along which numerous significant gold occurrences such as Eastmain Clearwater and Virginia Mustang-Wabamisk gold systems are present. Along this favourable break, an area with complex cross-cutting NW-NNW-NS subsidiary structures was targeted and new gold showings were uncovered.
AU33W MAG VS CHAIN LAKE
Dios 2009-2010 till sampling outlined a 15 km x 3-7 km well-structured gold NE anomalous dispersal train near the EM-1 dam. The 2009 Eastmain-1 train consisted of 21 till samples averaging 524 ppb Au in heavy mineral concentrates. The 2010 Eastmain-1 gold train resulted in 47 till samples that averaged 0.48 g/t Au. The Eastmain-1 till gold train yielded: 16 samples (34%) > 0.5 g/t Au; 11 samples (23%) >0.75 g/t Au; and 7 samples (15%) >1.0 g/t Au including 1.085, 1.130, 1.255, 1.390, 1.600, 1.750, 2.090 g/t Au (all from heavy mineral concentrates). This gold dispersal train is N240-250 striking, same as the area reported glacial striaes average measurements.
Dios compilation of all available till data for the Lower Eastmain highlights the importance of this significant gold train.
AU33W TILL MAP
In 2010, a brief (3-days in July) reconnaissance was carried on the sector at the head of the Eastmain-1 till gold train. From 40 representative grab-samples collected from glacial (mineralized tonalite & basalt) floats, three 40-75 cm size tonalite boulders with 2-5% disseminated pyrite respectively assayed 0.84 g/t Au, 1.5 g/t Ag (#852878); 2.3 g/t Au, 1.6 g/t Ag (#852880); and 2.3 g/t Au, 6.6 g/t Ag (#852884). Thin sections on the aurifereous floats confirmed potassic (biotite, microcline) alterations.
From July 2011 till November 2013, Osisko had the option to acquire a 51% undivided interest in the property and incurred some 1.4 M$ in exploration expenditures.
In 2011, two prospecting campaign carried out on the AU33 WEST property during July and September targeted the felsic (tonalite-granodiorite) igneous complex, the diorites and volcanic belts found up-ice of gold-bearing till dispersal trains and boulders defined by DIOS’ earlier work. The outcropping auriferous mineralization comprises 1-2% pyrite as disseminations and fracture fillings, locally with minor chalcopyrite and malachite, and is associated with potassic alteration. The gold values are associated with silver grades and generally copper as well, suggesting a porphyry-type deposit. Osisko completed a field program including geological mapping-prospecting, soil geochemistry (2 grids; b-horizon & humus). Dios and Osisko discovered several gold showings in outcrops ( between 0.535 and 3.79 g/t gold) in the tonalitic rocks.
During the 2012 summer, a field program outlined five new gold showings in the tonalte-granodiorite complex. In the fall, further work revealed outcropping gold showings, with 34 of the mineralized outcrops concentrated in an 18-km2 area. All showings yielded values above 100 ppb gold (0.1 g/t Au), and seven yielded between 1.58 g/t and 23.6 g/t Au. These anomalous values represent 13% of the 260 samples collected from this part of the property. In the 2012 Fall, ten trenches were dug to test soil geochemical anomalies or to extend known showings. Some targets were not fully tested due to the overburden thickness and the accidental nature of the ground. On these trenches, 515 track-samples totalling 397.05 meters were collected. Best results were obtained from the Heberto showing (trench T7), a first priority target that returned 5.0 g/t gold (grams per tonne) over 5.25 m et 1.12 g/t gold over 4.5 m in a sheared tonalite (type of granite). Several anomalous results of 0.5 to 1.1 g/t gold over 0.75 to 2.25 m were also returned in other trenches in the granitic rocks.
GEOLOGY AND SHOWINGS MAP
PHOTO OF HEBERTO SHOWING
In the 2013 spring, Osisko carried out a 33km line-cutting and induced polarization survey over the Heberto area in the central part of the property. This showing is associated with a weak induced polarization conductor over a 1.4 km strike. In November 2013, Osisko terminated its option on the project due to cuts in its exploration budgets.
In 2014, DIOS reprocessed the available AU33West geological data. Mineral maps were used to define the geochemical characteristics of the auriferous fluids associated with large hydrothermal pathways within the project. They show good correlation between gold and the presence of pyrite, of chalcopyrite and/or magnetite-hematite (oxidized system) located at the margins of several intrusions. The intrusions are interpreted from total field & vertical gradient magnetics and geological mapping.
Pyrite-Chalcopyrite versus magnetics
Moreover, these mineralizations are located within large halos of potassic-feldspar, silica, epidote, magnetite-biotite and hematite alterations. The last three may be indicative of a large hydrothermal-magmatic system characterized by strongly oxidized fluids.
Hematite-Magnetite-Epidote ALTERATIONS MAP
Silica-Potassic Feldspar ALTERARIONS MAP
The juxtapposition of structural measurements and magnetic data strongly suggests the presence of buried intrusive domes within the mineralized and altered area which are mainly developped along a north-south structural vector in the plutonic domain.
MAGNETIC DOME STRUCTURES VERSUS GOLD
The concentration of sulfidic mineralization along the margins of distinctive magnetic intrusions is also coincidental with higher potassium content (ground spectrometry).
K2O VERSUS MAGNETICS
The main Heberto gold showing is composed of disseminated pyrite along quartz veinlets and returned up to some 5.0 g/t Au/5.25meters in diamond saw track-sampling. This showing is coincidental with a weak north-south induced polarization conductor (chargeability) located near the margin a sub-circular magnetic anomaly, itself enclosed within a low magnetic one. Several gold soils are coincidental with geophysical conductors associated with the mineralization. The E-W Chain Lake structure is also associated with good soil gold anomalies (B horizon).
Induced Polarization versus Outcrops
IP VS GOLD SOILS
The geological environment of the Heberto area suggests a structurally-controled oxidized (IRG) intrusion-related gold system. The presence of concentric structures associated with mineralized brittle ones (suggestive of buried domes), the juxtaposition of alterations halos, the significant regional gold in till train, and the anomalous gold background in the fractured intrusive rock are good indicators of a large system.
Horizontal Diamond Saw Channel Photos