- KS Horizon
The Clearwater Property is underlain by typical Archean greenstone assemblages of the La Grande Group, which are essentially composed of volcanic rocks of basaltic to rhyolitic composition and related clastic and chemical sedimentary rocks, intruded by dioritic to granitic igneous rocks.
Cannard Deformation Zone (D2)
The D2 regional structural break, locally referred to as the Cannard Deformation Zone, has been traced for more than 100 km across the James Bay district. Eastmain has exposure to ~40 km of the break across the Clearwater and adjacent Clarkie properties. The Cannard Deformation Zone is 1 km south of the Eau Claire Project and hosts the Snake Lake, Clovis, Knight and Percival targets to the east of the Project, all within 14 km along the deformation zone.
Knight Serendipity Volcano-Sedimentary Horizon (KS Horizon)
The KS Horizon hosts the Percival Discovery and the Knight and Serendipity targets. It is an extensive package of metamorphosed felsic to mafic volcano sedimentary rocks hosting zones of hydrothermal gold mineralization (strong sulphide-silica alteration). A recently completed VTEM survey identifies a strong, 14 km-long anomalous electromagnetic trend that correlates well to the KS Horizon.
Geology of the Knight-Serendipity Horizon
The Knight and Serendipity areas are located at opposite ends of the KS horizon, a 14 km long L-shaped folded sequence. The KS Horizon is characterized by an extensive package of volcaniclastic and sedimentary rocks underlain by marine mafic metavolcanics. The Knight sector, including Percival, is located on the southwestern limb of the fold. This section of the fold is also located within, and is deformed by, the east-trending Cannard Deformation Zone. The Serendipity sector is located at the north end of the KS Horizon, extending north from the Cannard Deformation Zone, along the western side of, and parallel to, the NNW trending Hashimoto Deformation Zone. These two very large regional deformation zones intersect approximately 4 km east of Percival at the location of the KS Horizon fold closure.
In the Knight sector, the stratigraphic assemblage is comprised of felsic to mafic composition tuffs, mudstones and graphitic mudstones with basalt in a marine sedimentary environment. Local stratigraphy is highly deformed and affected by several phases of folding. Mineralization is composed of massive to semi-massive sulfide lenses, quartz, quartz + sulphide veins and veinlets. Sulphide phases are dominated by pyrrhotite with minor concentrations of pyrite, chalcopyrite and sphalerite. The geology suggests a syn-genetic volcanogenic sea-floor depositional environment. Airborne magnetic survey interpretation suggests numerous ESE-WNW trending shear zones as well as km scale folds are located in this area.
The Serendipity sector has a geological setting similar to the Knight sector, hosting a bimodal volcaniclastic/sedimentary environment characterized by an assemblage of felsic to mafic tuffs and graphitic black shales with nodular pyrite. Certain aspects of the sedimentary lithology indicate a more distal depositional environment than at Knight. Mineralization observed at Serendipity is composed of conformable massive to semi-massive sulphide lenses crosscut by smoky quartz veins primarily in sediments. Pyrrhotite with some pyrite, chalcopyrite and sphalerite are the sulphide minerals present. Mineralization is interpreted to be syngenetic and affected by all identified deformation phases. Gold enrichment was observed in fold hinges at the main Serendipity stripped area.
The Percival Discovery
Percival is located 14 km ESE of the Eau Claire deposit in the Knight sector of the Knight-Serendipity volcano-sedimentary Horizon (“KS Horizon”), on the Clearwater Property. The KS Horizon is characterized by an extensive package of metasedimentary and metavolcanic rocks metamorphosed from upper greenschist to lower amphibolite facies. The horizon is also affected by deformation related to major crustal scale structures specifically the Cannard Deformation zone at the Percival discovery. The stratigraphy at the Percival comprises foliated, predominantly south facing metasedimentary rocks underlain by marine mafic metavolcanics.
The Knight sector is interpreted to be at the south-western end of the prospective volcano-sedimentary sequence. Holes ER18-822 and ER18-823 were drilled on a single section to undercut gold mineralization exposed in a sequence of silicified metavolcanics and metasediments during the Company’s summer surface exploration program. These two holes intersected a silicified, sulfide rich, and gold mineralized brecciated interval of approximately 50 m in true thickness which extend from surface to a minimum vertical depth of approximately 100 m.
Holes ER18-824 to ER18-828 were drilled to flank Percival discovery holes ER18-822 and ER18-823, testing for the extension of the brecciated units over a NE strike length of 200 m and across stratigraphy over 250 m. Holes ER18-825 and ER18-828 highlight the absence of the mafic volcanic footwall seen in holes ER18-822 and others drilled further to the east. A NNW trending fault structure is magnetically inferred in this area and may represent a potential offset of stratigraphy and mineralization.
The following paragraphs present the preliminary descriptions and interpretation of units and mineralization associated with the Knight and Percival areas.
Geology of the Percival Discovery
a) Sedimentary Stratigraphy
Argillite, Graphitic Argillite
Argillites (mudstones) are commonly observed along the KS Horizon. They are typically fine grained, bedded to laminated, black to dark gray in color depending on graphite content. The argillite units are weakly magnetic, due to the presence of pyrrhotite. Sulphide content can range from disseminations to semi-massive pyrrhotite-pyrite present as thin bedded units and in fractures. Millimetre to centimetre diameter pyrite nodules are also commonly observed. Sulphide mineralization is often associated with carbonate.
Argillite supported breccia is commonly observed in the Percival area. These highly fragmented rocks are characterized by presence of mm to >10 cm sized sub-angular clasts of chert and quartz supported by an argillaceous matrix. Other clasts found in these breccias include polymictic sedimentary clasts. Amphibolitization and chloritization may cause local color and mineralogical variation, such as the appearance of mm to sub-cm size almandine garnet porphyroblasts which may grow into foliation parallel garnet bands. The presence of quartz and chert suggest proximity to an active source of syn-volcanic hydrothermal activity and deposition.
Lighter in color than argillite strata, siltstones commonly present as medium gray, fine grained, bedded units with variable sulphide content. Graded bedding in these units provides stratigraphic top orientations which consistently point south. Siltstones can potentially be prospective as gold bearing units when subjected to silicification and secondary sulphide deposition.
Greywackes are typically greenish gray, fine grained, moderately foliated and amphibolitized often with small disseminated garnets. Sulfides content in unaltered greywackes is typically low. Greywackes also display breccia sections in the Percival area and can be silicified.
In the Percival area, cherts are light gray-greenish in color and are locally observed in narrower intervals inside other types of sedimentary rocks, particularly argillites. Chert is also commonly observed as angular clasts in breccias. Some clasts and layers can be pyrite rich, with thin beds and laminations.
b) Mineralization Controls
Sedimentary breccias are intersected throughout the Percival area. Breccias are principally seen in argillite and mudstone units and to a lesser degree in siltstones and greywackes. Fragment components are polymictic and lithologies are generally representative of host units in the sequence, indicating the breccias are locally derived from slumping or mass flow. Breccias are identified as potential mineral hosts due to their relatively higher porosity which may create ideal traps for hydrothermal flow.
Silicified breccias are usually present as a medium gray, fine grained, fragmental rock which can be locally mistaken for felsic volcanic breccia. Very strong pervasive silicification can affect both clasts and matrix as seen in drill holes ER18-822 and ER18-823. Sericitization can also occur in breccia intervals and may indicate the presence of minor amounts of volcanic tuffaceous rock. Sulphide mineralization concentration in these units is commonly high and dominated by inter-fragmental and fracture filling (10 to 25% pyrrhotite-pyrite) with minor associated arsenopyrite and traces of sphalerite. Most silicified breccias intersected at Percival are gold mineralized, with pyrrhotite and pyrite present in both clasts and matrix, suggesting prolonged hydrothermal activity through evolution of the sedimentary package. Gold mineralization is observed to increase with intensity of silicification, in breccias in particular.
The Serendipity Prospect
The Serendipity Prospect is located along the western margin of NW-SE trending Hashimoto deformation zone (D3), at the intersection with the Natel deformation corridor (D2). Mineralization is strongly deformed and appears to be affected by all identified phases of regional deformation in the area. The Serendipity sector is hosted by bimodal volcaniclastic and deep-water marine sedimentary rocks comprising an assemblage of mafic volcanics, felsic to mafic tuffs and graphitic black shales with nodular pyrite, locally interbedded with stratiform and syngenetic massive sulfide lenses and chert, suggesting an exhalative mineralization in a deep-water marine environment with a potential to host gold-bearing, polymetallic VMS mineralization which may be remobilized and re-concentrated by folding during deformation events. The units are intruded by felsic porphyry dykes which have also been deformed along with the volcaniclastic sequence. Both are boudinaged and injected with mineralized, smoky quartz veins.
November 13, 2018 http://www.eastmain.com/_resources/news/Images/ER-181113-Clearwater.pdf
December 20, 2018 http://www.eastmain.com/_resources/news/Images/ER-181220-Percival.pdf
December 21, 2018 http://www.eastmain.com/_resources/news/Images/ER-181221-Serendipity.pdf,
February 25, 2019 http://www.eastmain.com/_resources/news/Images/ER-190225-Percival.pdf