OPERATION FOCUS- CASCAVEL_proof 23/08/2016 09:32 Page 5
OPERATION FOCUS
It is smelting the concentrate on site to
produce a doré bar before having the gold
refined in Brazil and sold. Tailings are dry
stacked.
Orinoco has adopted a strategy of commencing a
modest mine very quickly, and is now focussed
on growing the mine to reflect the potential of
the system. The plant installed by Orinoco has
the capacity to cater for throughput of up to
~100,000 t/y.
Looking to the future, the plant has been
designed such that a doubling of its capacity
should only cost around A$2 million.
First gold
Gravity tower with the Gekko IPJ and ISP on the
top and a Knelson concentrator on the level
below
gravity recovery field.” The circuit includes
primary, secondary and tertiary crushing along
with primary, scavenging and cleaning gravity
circuits. The flowsheet has been specifically
designed to maximise recovery of available
gravity gold. Unfortunately the installation of
this plant was delayed by customs for a number
of months.
The gravity circuit consists of primary
concentration in a Gekko Inline Pressure Jig (IPJ)
with centrifugal Gekko Inline Spinners (ISP) and
a Knelson concentrator conducting the
scavenging and cleaning functions.
The IPJ rapidly and efficiently pre-concentrates
high-value ore particles using gravity separation,
mechanics and fluid dynamics. The high energy
cost of heavy crushing is eliminated by Gekko’s
IPJ, which processes coarse feeds of up to 30
mm. A higher-grade ore is produced because the
IPJ concentrates crushed deposits to a smaller
mineral-rich feed volume. The ore at Cascavel
supports gravity only processing which ensures
lowest operating costs.
The simple, low maintenance ISP is a costeffective tool for separating coarse and fine
particles. Adding an ISP to a circuit upgrades
recoveries from intermediate or low-grade ores
and further lowers operating costs. It requires no
water for elutriation, is fully automated and can
produce a high-grade smelter-ready product.
The crushing circuit was manufactured in
Brazil by Simplex and the gravity module,
electrical MCCs, installation supervision and
commissioning was provided by Gekko
Jaw and cone crushers with VSI on the far right
24 International Mining | SEPTEMBER 2016
Systems.
“There has been a strong synergy between
Orinoco and Gekko through our common Perth
office bases and Brazil relations with Gekko’s
longest serving agent, Minetec based in Brazil
and headed by Diego Mielke,” said Tim Bell,
Gekko’s Manager for WA & Asian Operations.
Because the gold is both free-milling and
coarse, no leaching is required to extract the
gold. This means that no cyanide is used,
resulting in a much lower environmental
footprint and appreciable capex and opex
savings. Nevertheless, the plant will recover
about 90% of the gold. Test work confirms
recoveries of +90% for coarse, free-milling gold
at particle size of 600 μm.
Orinoco hopes in the future to introduce a
cyanide circuit to recover the remaining 10% of
the gold.
Orinoco Gold poured its first gold from Cascavel
in July, resulting in the production of the
company's first bar of gold bullion.
This was a trial gold pour using some of the
gold concentra te produced during the plant
commissioning phase, derived from low-grade
development material.
The Cascavel gravity processing plant is now
running on a 24 hour basis while continuing to
process stockpiles of low grade development
material. High grade parcels of ore from
production stopes are now being processed and
assayed as the company commences its
production ramp-up.
The bigger picture
Drilling and exploration along strike from
Cascavel indicates that the gold-bearing
structures have considerable continuity, with
gold mineralisation shown to be occurring at
multiple points over more than 3 km immediately
along strike from Cascavel, and in the same
generation of mineralised shear zones 18 km to
the south at the Sertão gold mine. Similarly, the
down-plunge continuity of the gold-bearing
structures has been demonstrated in drilling at