The Ok Tedi mining operations are centred on the Mt Fubilan deposit in the upper Fly River catchment in the remote Star Mountains, Western Province.

Mt Fubilan is a rich coppergold-silver deposit with several phases of mineralisation centred on two intrusions, known as the Fubilan monzonite porphyry, located in the northern half or Centre Pit area and the Sydney monzodiorite stockworks with subsequent alteration in the south. Majority of the ore is found in the sulphide skarns, located adjacent to the intrusions along the contacts with the limestone and siltstone units.

In 2020, OTML continued to target the discovery of new mineral resources within the Special Mining Lease One (SML1) to replace mined reserves and extend the project mine life.

The geology and exploration teams completed further resource definition drilling on the Darien and Wellington deposits during 2020 and submitted samples for laboratory analysis. Resourceestimates will be completed in early 2021. The focus for 2021 will be to continue deep resource drilling in the New York Breccia and other breccia targets.

Near-mine exploration in 2020 focused on the definition of previously indicated mineralisation in SML1. Thirty holes with a combined length of over 11,800 metres (m) were drilled during the year.

New York Breccia
Two new high-capacity LF90 drill rigs were mobilised in late 2020 to undertake systematic directional resource definition drilling to deeper levels within the New York Breccia deposit. Atotal of eight resource definition drill holes targeting the New York Breccia were completed in 2020.

A preliminary conceptual mining study identified potential mining options in the New York Breccia system, but additional exploration in 2021 will be needed to increase the volume of potentially mineable material.

Wellington
A total of 13 resource definition drill holes targeting the Wellington deposit were completed in 2020, with a maiden resource estimate to be finalised in 2021.

Mineralisation at Wellington consists of a complex series of magnetite skarn and calc-silicate endoskarns associated with the Taranaki Thrust and limestone / intrusive contacts.

Darien
Mineralisation at Darien consists of a small copper/gold porphyry system immediately west of the New York Breccia. Historic drilling has indicated copper mineralisation, but the extent of the system has never been accurately defined. Resource definition will be completed in conjunction with the Wellington skarn update.

Gilor Breccia
Resource definition of the Gilor Breccia was planned for early 2020. A drill pad and camp site were established but the program was shut down in March due to COVID-19 restrictions. The program will be reinstated in 2021.

Mining of the Mt Fubilan Ore Reserves continues to be carried out as a large open pit operation. Mining is conducted using conventional drill and blast techniques, with shovel and excavator loading equipment. Ore is mined and transported to a primary crusher as first stage processing or to a Run of Mine stockpile, where blending of various ore types can take place. Waste rock is characterised according to its Acid Rock Drainage (ARD) potential and disposed of in one of five waste dumps. Limestone waste rock is selectively dumped together with potential ARD waste rock to neutralise acid production.

The current pit design and pit sequencing has been developed to maximise value while meeting environmental constraints agreed with mine-affected communities.

With approximately 9,000 mm of rainfall per annum, incident rainfall and runoff contributes significant volumes of free water draining into the pit. Rainwater also permeates into the rock mass contributing to instability due to increased pore pressure.

Comprehensive monitoring of hydrological and geotechnical factors are incorporated in mining strategy and plans to ensure safe operations.

The ore is crushed in a primary crusher at a nominal 8,000 tonnes per hour and conveyed to a primary ore stockpile. The primary ore is then ground (two trains each comprising a SAG mill and two ball mills) to a final grain size of approximately 180 microns.

OTML commissioned and handed over the new Crusher Replacement Project (CRP) on December 14, 2020. Initially identified as a key focus area in the OTML 2017 strategic business plan, the project consists of a new gyratory crusher, screening plant, coarse ore stockpile, together with demolition and removal of the existing old crushing and conveyor system.

OTML’s business operations are centred on the Mt Fubilan deposit located in the Star Mountains. The deposit is mined as a large open pit with a flotation processing plant capable of treating in the order of 22 to 24 million tonnes per annum (Mtpa), and currently recovering copper and gold into a saleable concentrate using conventional technology. The throughput rate is highly dependent on the ore lithology delivered from the mine. The concentrate product contains approximately 25% copper with gold content in the range of 15 to 25 g/t.

Ore is mined and processed at an onsite flotation processing plant capable of treating up to 24 million tonnes per annum (Mtpa). The plant currently recovers copper, gold and silver into a saleable concentrate.

The primary ore is crushed and ground using Semi-Autogenous Grinding and Ball mills to a final grain size of approximately 180 microns.

The finely ground material is treated in two mineral floatation circuits to e ........