The Upper Puruni Region hosts a number of mineralized systems in addition to the 6.9 million-ounce Toroparu Deposit. Several of these systems have been drilled and contain either satellite deposit gold reserves (Toroparu SE Zone) gold resources (Sona Hill), and gold mineralized intercepts in saprolite and fresh rock (Wynamu Hill and Ameeba gold anomalous features). Coinciding or overlapping geochemical gold anomalous features and geophysical anomalies indicate potential for additional mineralized systems along intrusive contact zones (e.g. at Timmermans and Otomung). Several of these areas have been mined historically for alluvial gold. Geologic evidence supports both definition drilling of existing mineralization system discoveries and exploration for additional deposits within the sigmoidal flexure structure in the northwest trending Puruni Shear.
Sona Hill drill core show widespread disseminated fine magnetite crystals within the hydrothermal halos and the strongly altered shear zone. The magnetite occurrence provides a potential geophysical marker that can help identify extensions of the gold mineralization system in the surrounding areas of Sona Hill.
Airborne magnetic surveys indicate elevated magnetic values extend around the Sona Hill area. Ground geophysical and infill geochemical surveys conducted in 2016, consisting of an 18-km ground Mag/IP pole-dipole (Induced Polarization) survey & 120 sample infill saprolite geochemistry program over a 1,000 x 1,500 m grid covering the Sona Hill Resource Area and areas to the west, northwest, and south confirm the elevated magnetic signature from airborne surveys.
The Magnetic, Induced Polarization, and saprolite geochemistry results from these surveys suggest the shear zone and hydrothermal halos with associated gold mineralization may extend both to the northwest, south, and down-dip to the west of the Sona Hill gold resource shell.
Additional drilling targeting anomalous areas identified within the Sona Hill Area are scheduled for reconnaissance and resource drilling during the next seasonal exploration campaign.
Wynamu Hill is an isolated geochemical gold anomaly situated '9 km north of the Toroparu deposit in the center of the interpreted Upper Puruni shear bending zone. It is one of several gold anomalies located within a large geochemically identified hydrothermal halo that extends for 20 km by 7 km around Toroparu.
Wynamu was first identified as a NNE oriented, 1 km x 500 m wide geochemical anomaly feature of continuous 100+ ppb values with a dozen high values of >500 ppb during regional geochemical surveys conducted in 2012 and 2013. Initial air-core test holes conducted in 2014 confirmed the presence of gold in saprolite and upper layers of bedrock.
A first phase reconnaissance drill program was conducted in 2016 consisting of 1,127 m in 14 inclined shallow diamond drill holes of average 80 m length along 3 NNW oriented drill fences. Gold was intercepted in saprolite and fresh rock in 6 of the 14 drill holes on the top and flanks of the Wynamu Hill feature.
Highlighted intercepts include 7.18 g/t Au from 0m - 21.5m in WYD013, 19.5 m of 1.18 g/t from 42.5m - 62 m in WYD003, and 9.0 m of 1.57 g/t from 32m - 41m in WYD014.
Bedrock drill core logging suggests gold mineralization is related to moderate quartz veining and fracturing, locally even brecciation, with abundant pyrite occurrence within and adjacent to felsic leucocratic and intermediate dyke sets.
The dykes intruded a sequence of layered, often porphyroblastic, volcanosediments (volcaniclastics) with some intercalations of intermediate composition lava flows. The dykes are often surrounded by halos of intense bleaching, carrying locally abundant pyrite crystals. Good gold grade is clearly related to abundant occurrence of pyrite and gold-pyrite mineralization.
The oriented core data indicate that most of these dykes have a NE to ENE orientation which corresponds to the orientation of the geochemical anomaly, with structural data indicating most of quartz-feldspar veins and veinlets are +/- E-W oriented steeply dipping structures, which corresponds to the vein style in the Toroparu deposit.
ICP multi-element analysis indicate gold-trace element association is Au -- Ag -- Te -- Bi and a weaker correlation with Mo, which is like the one marking the Sona Hill gold mineralization. ICP analyses indicates systematic sampling of Ag in the gold mineralized zones is warranted.
Initial leach test work on Wynamu saprolite core samples indicate a 91% extraction of gold at 106 microns grind over a 24-hour leach residence time.
Systematic infill drill fences have been selected for the next exploration campaign to model the extent and grade of mineralization the Wynamu Hill anomaly.
Regional litho-structural interpretations from all available regional data including airborne magnetics & radiometrics, DTM maps, satellite imagery (SRTM, JERS images), existing geological maps and regional geochemical data lead to the interpretation that the Toroparu Gold-Copper-Silver deposit and its satellites lie within the southern part of a regional sigmoidal flexure structure of the Puruni shear belt, which is interpreted as a restraining bending zone.
The Otomung Concession, located 20 km north-northwest of Toroparu, lies in an area that Sandspring's geologic model suggests may have similar conditions to those in the Toroparu area. Sandspring has conducted three systematic saprolite-geochemical surveys of the Otomung concession, with consecutive tighter survey grids focused on an interpreted elongated intrusive structure defined by multi-element saprolite geochemistry interpretation and airborne geophysics in the center of the concession.
Regional geochemical survey results including K-Th-U/Al trace element associations combined with the airborne radiometric data identify a possible elongated intrusive in the center of the Otomung concession, and the possible existence of similar plutonic structure further to the NW.
The Au-Mo signature from the geochemistry surveys along the northeastern contact of the interpreted intrusive revealed a potential 8 km long NW-SE trend. The gold-moly trend coinciding with a magnetic low lineament of the same orientation on the airborne maps adjacent to a mag high possibly characterizing late Paleo-Proterozoic intrusives indicates possibility of a significant regional structure related to Puruni shear corridor.
Further infill sampling on a 100 x50m grid along the 8km linear gold-moly anomaly and 50 x 50m grid on the small anomalous feature to the north of the concession is planned for the next exploration campaign. Results from these surveys are expected to allow the identification of a reconnaissance drill target zones.
On a district scale, the gold potential of the Guiana Shield is vast, but remains untapped. The Guiana Shield is analogous to the West African Shield, with which it shares a common geologic history. More than 30 gold deposits have been discovered in the West African Craton, which has undergone systematic surface exploration over the last decades. There are currently over 30 deposits in production in that region, which have collectively produced millions of ounces of gold in this now famous gold district. In contrast, alluvial miners have discovered most of the existing deposits in the paleo-proterozoic rocks of the Guiana Shield, which stretches northwest across French Guiana, over Suriname and Guyana to Venezuela, and has been exposed to very little systematic exploration. To date, the Guiana Shield has produced only a few multimillion-ounce deposits, suggesting there are numerous possibilities to discover more world-class gold deposits in these mineral districts.