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.
About 350 km NE of Matagami, near the James Bay EM-1 power dam, the AU33West project covers 200 sq. km. Access to the project is by Hydro-Quebec gravel road linking Nemaska/Eastmain-1/LaSarcelle.
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. 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 3 day reconnaissance was carried on the sector at the head of the Eastmain-1 till gold train. From 40 representative samples grabbed from glacial (mineralized tonalite & basalt) floats, three 40-75 cm size tonalite boulders with 2-5% disseminated pyrite assayed 0.84 g/t Au, 1.5 g/t Ag ; 2.3 g/t Au, 1.6 g/t Ag ; and 2.3 g/t Au, 6.6 g/t Ag . Thin sections on auriferous 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 targeted the felsic (tonalite-granodiorite) igneous complex, diorites and volcanic belts found up-ice of gold-bearing till dispersal trains and boulders defined by DIOS’ earlier work. Outcropping auriferous mineralization comprises 1-2% pyrite as disseminations and fracture fillings, locally with minor chalcopyrite and malachite, and is associated with potassic alteration. Gold values are associated with silver grades and generally copper as well, suggesting a porphyry-type deposit. Osisko completed 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 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 (Looking West)
During spring 2013, Osisko carried out a 33km line-cutting and induced polarization survey over the Heberto area in the central part of the property. 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
Juxtapposition of structural measurements and magnetic data strongly suggests presence of buried intrusive domes within mineralized and altered area which are mainly developped along a north-south structural vector in the plutonic domain.
MAGNETIC DOME STRUCTURES VERSUS GOLD
Concentration of sulfidic mineralization along margins of distinctive magnetic intrusions is also coincidental with higher potassium content (ground spectrometry).
K2O VERSUS MAGNETICS
In 2014, detailed geological and structural mapping of Heberto stripping delineated the APEX ZONE: a north-south striking 7 m wide mineralized envelope grading 1.89 g/t gold (7 X 10 m), open along strike, at depth and to the west. The APEX ZONE is hosted within an open anticline structure, with limbs dipping 40-50° towards each side, suggesting potential for widening of gold mineralization close to surface. Previous diamond saw channel sampling on newly outlined mineralized structure returned up to 5.18 g/t gold over 5 m. The overall average for 72 one-meter channel samples (up to 21.4 g/t gold/ 1 m) over the 30 x 10 m Heberto stripping is 0.74 g/t gold. The APEX ZONEconsists of 1-5% disseminated pyrite associated with quartz stringers/stockworks and biotite-sericite alteration, hosted within sheared and altered quartz-diorite intrusive. The APEX ZONEis bordered to the east by lower grade mineralization (50-450 ppb gold) consisting of traces-1% pyrite associated with dilatational flat fractures. Two 2014 samples grabbed from quartz veinlets bearing quartz-diorite intrusives returned 7.89 and 8.06 g/t gold. The mineralized APEX anticline structure and dilatational flat fractures could result from an uplift related to a buried magmatic dome below the Heberto area.
The Heberto showing is located at the southern end of a non-outcropping weak 1 km long northsouth striking IP conductor, situated at the contact of a sub-circular magnetic high anomaly. Stronger chargeability anomalies (possibly associated with more sulphide content) were outlined along strike to the north and 400 m south of the Heberto showing. The IP conductor is considered a first priority target to be extensively tested in the upcoming drilling program. Gold-in soil anomalies are also coincident with the IP conductor. Located 3.5 km north, the geological setting of the Robino magmatic-hydrothermal breccia pipe (up to 37.6 g/t Au in grab sample; see September 17 press release) shares several similarities with the Heberto showing. Mineralized quartz-biotite-sericite stringers similar to the ones observed at Heberto were mapped at the northern margin of the Robino breccia pipe, hosted within a northsouth structure. The Robino breccia is coincidental with a 350-400 m circular magnetic low., Circular magnetic low anomalies located along ring structures were interpreted in the immediate vicinities of the Heberto showing from airborne geophysical data. All these geological observations may indicate the presence of a nearby mineralized breccia at Heberto.
In the upcoming future, DIOS will focus on the Heberto and Robino areas. Highly attractive drill targets were recently outlined, confirming the potential of the project. The presence of concentric structures, locally associated with gold mineralization, combined with the recent discovery of a magmatic-hydrothermal breccia pipe, suggest the presence of buried magmatic-porphyry domes. Detailed geological mapping in 2014 confirmed the presence of a diorite-tonalite complex on the road-accessible Au33W property, in which felsic intrusives were injected by dioritic plugs and related breccias. Brittle north-south structures seem to have controlled breccia setting, alteration and gold mineralization. Moreover, the significant regional gold in till train and the anomalous gold background in the fractured intrusive rocks are good indicators of a large buried mineralized system. The geological environment of the Heberto area is similar to the one of a structurally-controlled oxidized (IRG) intrusion-related gold system.
Induced Polarization versus Outcrops
IP VS GOLD SOILS
Horizontal Diamond Saw Channel Photos