Global
An underground tunnel at Grasberg. The minerals district
at Grasberg includes two operating underground mines:
Deep Ore Zone (DOZ) and Big Gossan.
while two of his colleagues were injured.
In addition, IndustriALL claims that
the area surrounding the Grasberg is
volatile. The union mentions shootings
in October during which one policeman
was killed and six injured. Police allege
the shootings are linked to separatist
groups who believe exploitation of the
mine doesn’t benefit local people.
According to IndustriALL’s
general secretary, Valter Sanches,
the commission has made it clear
PT-FI has violated human rights
at the Grasberg mine. “We urge
the company to comply with the
recommendations of the commission
and immediately reinstate the
sacked workers. We also call on the
president of Indonesia to ensure
that PT-FI does so,” says Sanches.
A mining giant
Mining at Grasberg started in 1967.
Today, the Grasberg minerals district
includes three operating mines: the
open pit, the Deep Ore Zone (DOZ)
underground mine and the Big Gossan
underground mine. Operations at
Big Gossan restarted in the fourth-
quarter of 2016. Furthermore, PT-FI
initiated pre-commercial production at
the Deep Mill Level Zone (DMLZ)
underground mine in September 2015.
Mining of the Grasberg open-pit
started in 1990 and PT-FI is currently
in the final phase of mining the open
pit before transitioning to the Grasberg
Block Cave underground mine in 2018.
Production from the ore stockpiles,
which are located outside of the pit limits,
is expected to continue until early 2019.
The DOZ ore body lies vertically
below the now depleted Intermediate
Ore Zone. Production from the DOZ
ore body started in 1989 using open
stope mining methods. Production
was suspended, however, in 1991 when
the open pit started producing ore.
Production resumed in September 2000
and is expected to continue to 2021.
Using ore passes and chutes, load-haul-
dump units transfer ore into haul trucks.
The trucks dump into two gyratory
crushers and the ore is then conveyed to
the surface stockpiles for processing.
The DMLZ ore body lies below
the DOZ underground mine at the
2 590m elevation and represents
the downward continuation of
mineralisation in the Ertsberg East
Skarn system and neighboring Ertsberg
porphyry. In September 2015, PT-FI
initiated pre-commercial production
at the DMLZ underground mine,
which represents ore extracted
during the development phase to
obtain access to the ore body.
Targeted production rates once the
DMLZ underground mine reaches
full capacity are expected to be about
80 000 metric tons of ore per day in 2022.
Production at the DMLZ underground
mine is expected to continue to 2041.
The Big Gossan underground mine lies
adjacent to the current mill site. It is a
tabular, near-vertical ore body. Production
from the Big Gossan ore body, which
restarted in the fourth-quarter of
2016, is expected to ramp up to 7 000
metric tons of ore per day in 2022.
The Big Gossan mine uses a blasthole
stoping method with delayed paste
backfill. Stopes of varying sizes are mined,
and the ore is dropped down passes to
a truck haulage level. Trucks are chute
loaded and transport the ore to a jaw
crusher. The crushed ore is then hoisted
vertically via a two-skip production
shaft to a level where it is loaded onto a
conveyor belt. The belt carries the ore to
one of the main underground conveyors
where it is transferred and carried to the
surface mill stockpile for processing.
JANUARY 2018 MINING MIRROR
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