The current Ok Tedi Mining Limited (OTML) exploration program is centered on five exploration licences covering 3,450 square kilometers. In 2013, the exploration tenement portfolio increased due to the granting of three additional tenements (EL 2256, EL 2289 and EL 2276).
In line with a re-invigorated exploration strategy that is focused on the near-mine environment where the mineralisation potential is highest and easily accessible, the majority of the exploration licences are located along the prospective 'Ok Tedi Corridor'. This corridor is a deep-seated geologic feature that trends north-northeast through the Ok Tedi deposit into the West Sepik Province where currently, all known copper and gold mineralisation in the region is located.
The Mt Fubilan open-pit deposit is one of the key future expansion opportunities for OTML.
During 2013, an extensive drilling campaign continued in and around the Mt Fubilan pit to upgrade the mineral resources according to the guidelines of the 2012 Joint Ore Reserves Committee (JORC) Code.
As at 31 December 2013, the Mt. Fubilan Mineral Resource estimate was 871Mt at 0.44% Cu and 0.54 g/t Au using a cut-off based on ‘net smelter return’ which is a composite parameter, simulating the return after processing. The cut-off used was USD 10 Net Smelter Return (NSR) per tonne.
OTML started focusing on geo-metallurgy in 2013. This strategy relates to combining geology and geo-statistics with extractive metallurgy, to create a geologically-based predictive model for the processing plant.
In terms of regional exploration the main focus for OTML will be the drilling of currently identified targets.
The Townsville Project (a site near the current mine) is the most advanced where the expectation is to grow and better define the copper-gold resource.
OTML will also embark on a review of historical exploration data, an exercise with the catch phrase “mining our data”, which will provide a better understanding of the controls on regional and prospect scale mineralisation and enhance the length of the mine life at Ok Tedi.
Near-mine - Mt Fubilan Mineral Resource Development and Exploration
Mt Fubilan is a rich copper-gold silver deposit with several phases of mineralisation centered on two intrusions, a Monzonite Porphyry and Monzodiorite stock works with subsequent alteration. The majority of the contained copper and gold is found within sulphide skarns, located adjacent to the intrusions along a contact with limestone and siltstone units. These skarns have been formed by the introduction of mineralised fluids along contacts and faults that have reacted with the host rocks.
Over 21,900m were drilled in 2013 from a completed 59 drill holes. The locations of the holes completed in 2013 are shown on the geology map of the Mt Fubilan mine area.
The drilling programme improved the understanding of the deposit and highlighted the extension of significant mineralisation to the North East of the current pit (Siltstone Ridge area) and to the south-southeast of the pit (southern Monzodiorite extension). These findings generated significant intercepts improving the potential for additional cutbacks for the current Mt Fubilan pit. The location of the section lines are shown in the geology map.
Information obtained from these drill holes was used to update the geological model, which is then used to update the annual Mineral Resource Statement. The design and development of the geological model and Mineral Resource estimates were carried out according to the guidelines of the JORC Code (2012). This estimate was completed, validated and signed off internally by OTML’s Competent Person.
As at 31 December 2013, the Mt. Fubilan Mineral Resource Estimate is 871Mt at 0.44% Cu and 0.54 g/t Au.
Near-mine Exploration - Townsville Prospect
The exploration focus in 2014 will be on targets within a five to ten kilometre radius of the mine and this includes the Townsville project. This prospect is hosted within the Pnyang Formation (Miocene age, 5 to 23 Ma), comprising of near-surface high-grade gold hydrothermal mineralisation and fault breccia’s grading up to 60g/t Au and deeper copper-gold calc-silicate skarns. Edit note: Calc-silicate is the term not calcium-silicate.
The main objective of the 2014 drilling at Townsville is to better define and grow the copper-gold resource and improve understating of the metallurgical properties of potential ore through metallurgical studies. The drilling in late 2013, resulted in one particular hole (TVLDDH81), returning the highest copper grade down-hole intercept (up to 12.1% copper) since drilling commenced at Townsville in 1992.
This result was 200m west from the main resource in an area referred to as the Titan Prospect, and will be the subject of follow-up drilling in 2014.
In addition to drilling and associated fieldwork, the Geology Team has planned other key work for 2014, commonly phrased as “mining our data”. A wealth of geoscientific exploration data has been generated over the last two decades by OTML. This important data will be subject to an internal review and analysis and incorporate the Geographic Information System (GIS) technology, together with the latest geological research findings on porphyry copper gold systems in the Indo- Pacific rim region.
This analysis will review data received from the 2009 aerial (helicopter) geophysical survey that was conducted over key portions of the Ok Tedi corridor. The aim of the “mining our data” project, is to obtain a better understanding of the controls on mineralisation from a regional-scale level down to an individual prospect-scale to assist in exploration drill targeting. It is expected that the outcomes from this programme will greatly enhance the length of mining operations at Ok Tedi through the provision of a host of new targets to feed into the exploration and project development pipeline.