Since mid 1800's, Oko Mountains, situated
just above the Oko-Cuyuni gold prospect, were producing vein, eluvial and alluvial gold.
In early times, only shallow deposits adaptable to labor intensive manual mining, with
gold grades higher than 1.0 g/m3, were exploited. Later, more deep alluvial deposits of
large creeks were mined. A much deeper large river deposits are being mined now.
The four large volume suction dredging operations, mining alluvial deposits in at the
present time Guyana, are within five largest producers of gold. Definitively, the profit
is in a large volume dredging of alluvial gold deposits located within medium to large
river systems.
General information:
The prospect is situated below Oko river mouth on both sides of Cuyuni river. It
covers extensive (over 4,400 acres) Cuyuni river flats (primary alluvial terraces). The
area just above the prospect; Oko Mts., Oko river, Aremu river and Ekribisi river was and
is alluvial gold producing. Oko Mts. (Warirri Cr.) was a first place where gold was
discovered in Guyana in mid 1800's. Now two operations are active in Oko Mts., one
operation is active in upper Oko river after mining out the middle part and a second
operation is planned in lower Oko river. Active river channel dredging, few years ego,
along the prospect, was profitable. Average mining gold grade was: (~850mg/m3)
Access:
One of the advantages of this alluvial prospect is an easy access. Few miles of
river from Bartica, and 37 miles of road from Kartabo Point to Oko River mouth,
which is near the prospect.
Geology Summary:
Variegated schists, amphibolites and
quartzites forming rugged hills capped by laterite. Dolerites intrude above rocks. Some
places are overlain by the white sands formation. Hornblende biotic gneisses form a large
complex group south of Oko Mts. Gold is associated with Barama-Mazaruni assemblage.
Alluvial deposits of Cuyuni river are ~ 15 m. deep and are mineralized with fine gold
trough the whole vertical section. An overall alluvial gold grade in Matope-Arawak creek
(draining Oko Mts. into Cuyuni river, above the prospect.) is above 1 gram per cubic
meter. Gold is in small chips and is stained with limonite. Its source is an extensive
complex of large quartz formations and veins within Oko Mts. The primary deposit is most
probably of a quartz-gold and/or quartz-gold-pyrite type. I observed large quartz veins in
purple schists between Oko Mts. and Oko river. The alluvial material which forms the
prospect was contributed by Cuyuni, Oko and Ekribisi rivers. It is trapped in a natural
riffle between two belts of harder rocks (doleritic dikes) through which Cuyuni river had
to break in falls and rapids. Flat topped hills indicate an extensive erosion cycle in the
area and my experience suggests a strong possibility of one or two "false
bottoms" with gold rich gravel below them. In Potaro River (few hundred km. away)
gold grade, just below the first hard clay ("false bottom"), was 87 times higher
than the top gravel grade! Aerial photos show, within the prospect, a system of
paleochannels related to Cuyuni River's lateral movements.
Estimated gold grade:
The expected overall (over a total volume of material) gold grade should be between
0.35 and 0.85 gram per cubic meter. Paleochannel has a higher gold grade than active river
channel where constant addition of sterile alluvium dilutes overall gold grades.
A bulk sampling pit, within a paleochannel just below Oko river, produced 261 ozs. from
~7,000 m3 of sand/gravel. (1.16 gram per cubic meter) The active river channel was dredged
during late 70's and early 80's with 6 inch jet pumps. The average production, for a 15 h.
work-day, was between 10 and 15 ozs. per day. Later, 8 inch gravel pump dredges reworked
tailings, and in the same lenght work-day produced 4 to 6 ozs. per day. At the end of
1997, few dredges were reworking old tailings for a 1.5 to 2 ozs. per day production.
Geochemistry Summary:
Geophysics Summary:
Drilling Summary:
Reserves Summary
+/- overall gold grade is 0.8g/m3 Over 200,000,000 m3
Other:
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