Mining Mirror January 2018 | Page 11

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 [9]