Selinsing and Buffalo Reef are located in the Central Gold Belt which is a major north-south trending structural zone up to 30km wide hosting numerous major gold mining districts. Several historical and current major gold mines such as Penjom and Raub have each produced over one millions ounces of gold.
The Central Gold Belt stretches 450km from Malacca in the south, to the west of Kota Bharu in the north. Major shear zones that cut through the Selinsing gold mining district have hydrothermal fluids and allow the concentration of gold.
Selinsing and Buffalo Reef are the primary gold projects for Selinsing gold mine, and the mineralization is still open in all directions.
Malaysia is endowed with a number of major sediment-hosted, orogenic gold deposits that lie parallel to but east of the Bentong-Raub Suture Zone on the gold central belt, North-South in central Malaysia, where Selinsing Gold Mine sits. Selinsing holds one of the major gold deposits in Malaysia laid around the intersection of the steep shear zone with a favourable, reactive body of rock.
Selinsing regional exploration covers a radius of 30km around the Selinsing Gold Mine at the Kuala Lipis and Koyan area.
Gold mineralization can be found preferentially within or immediately adjacent to the shear zones, especially where antiformal and synformal hinges in the preferential host rock create zones of dilation and brittle failure. Selinsing regional exploration continues to focus on discovering a major gold system by identifying the major shear zones that pass through the Selinsing area and mapping broad lithological packages with particular emphasis on medium to coarse-grained felsic volcanic tuff or felsic intrusions.
In the past years, Monument’s exploration has targeted the Selinsing-Buffalo-Peranggih shear zone among several other parallel shear zones that host gold mineralisation in the gold mining districts.
Medang Ridge system: The north-trending Medang ridge shear zone located 1km east of Selinsing and Buffalo Reef was identified by the previous operator. The mineralized structure runs for about 5km with several prospects being identified, namely Koyan South, Medang Ridge South, Central, and North. The shear zone extends south, and several deposits, namely Bukit Nangka and the Tersang-Chenua gold prospect, lie between Raub gold mine and Selinsing.
Rubber Hill-Ular Seluar system: The second parallel structure, 3km to the east of Selinsing and Buffalo Reef, host the Ular-Seluar and Rubber Hill prospects. Significant drilling was carried out by the previous operator in this area which showed promising results.
Selinsing-Buffalo-Peranggih system: 14km north to Selinsing and Buffalo Reef regional shearing structuring, Peranggih and Mentique have been identified as new oxide exploration targets. The gold mineralization is associated with a hydrothermal breccia system which however is distinct from the hydrothermal veins system that occurs at Selinsing and Buffalo Reef. Folding, shearing and vein formation in these rocks indicate that the deposit is of similar type and generation to the Selinsing structures.
Low and high grade gold mineralization is also hosted in both matrix and clast supported quartz breccia. The mineralised shear zone extends over a distance of approximately 1.2km in length with varying widths of between 25m to 50m with identified areas of high gold grade mineralization surrounded by a halo of lower grade mineralization. The mineralisation is open down dip and along strike.
Regional Exploration Programs
Regional exploration along the northern extension of Selinsing structures was initiated in 2010 to create new drill targets by conducting geochemical sampling and follow-up work on the Peranggih area and the northern part of Selinsing. The targets were identified by its previous predecessor Avocet through 14 reverse circulation (“RC”) holes for 906m. That confirmed gold mineralization closely associated with the brecciated shear zone.
From 2018 to 2019 The expansion of the geochemical sampling coverage was undertaken from north catchment of Sungai Mentique to the southwest of Peranggih, spaced at 50m x 200m, and from west of Satakto to the northeast of Peranggih spaced at 100m x 400m, covering a total area of 16km². As a result, a total of five different gold anomalous zones have been identified in the study area, two of them striking along more than 1.5km in a north west-south easterly direction, and up to 0.3km wide. Zone 1 (Peranggih extension) and Zone 2 (Mentique) are the most significant anomalies discovered.
Peranggih exploration is carried out in three separate zones within the main regional structure: Peranggih South, Peranggih Central, and Peranggih North.
Monument has undertaken a diamond drilling campaign starting in March 2014, with 21 holes completed for over 2,007m. Oxide trenching, pit geological mapping, surface sampling, and initial geological modeling program were executed during 2016 and 2017.
A subsequent close space 5m x 5m Percussion Rotary Air Blast (RAB) drilling program, 2,780m for 298 holes, was carried out in August 2017 at the Central zone to test 150m strike length x 80m width of the mineralization. This program initially indicated over 38kt @ 1.00g/t Au with a broad 15m-20m wide high-grade zone and multiple isolated high-grade zones, surrounded by a halo of lower grade gold mineralization. It proved the presence of disseminated gold in the breccia matrix.
From February 2018 to May 2018, a resource definition drilling campaign was conducted with 995m for 21 DD holes, and 1,810m for 37 RC holes covering a much larger area than the previous close space drilling. The drilling establishes that Peranggih has the potential for a mineralized hydrothermal breccia system along the same regional shearing structure hosting Selinsing and Buffalo Reef deposits.
It was noted that elevated gold grades are typically associated with higher intensity quartz veining and brecciation, however zones of veining/brecciation also occur in un-mineralized rocks. The zones of quartz veins are normally associated with higher hydrothermal alteration with sulfide minerals, including pyrite, chalcopyrite, arsenopyrite, and stibnite, and typically brecciated.
From January 2020 to March 2020, a trial mining campaign was carried out under which the bulk sample was extracted from the higher mineralized area at Peranggih Central delineated from previous GC drilling and fed into the Selinsing gold processing plant to confirm the average grade, quantify the presence of coarse gold, and test the metallurgical performance at plant scale. The bulk sampling result shows minor grade variance compared to the mineral inventory internally estimated based on grade control data. It has confirmed the phreatic nature of the breccia body and the reliability of the sampling and assaying method used for the project assessment. Out of 15,677 tonnes of material mined, 13,047 dry tonnes of material were processed at a reconciled head grade of 1.17g/t Au with an actual recovery of 89.8% from reconciliation compared to an average assayed grade gold of 1.22g/t Au with a processing recovery of 90.2%. Both gravity and leach responses were very encouraging.
Since June 2020, the grade control drilling has continued throughout the defined Peranggih shallow mineralization area. As of March 2021, a total of 39,978m was drilled indicating over 220kt @ 0.89 g/t Au being internally delineated. 101,644t @ 0.74 g/t for 2,423 oz Au was mined from Peranggih since then.
The Mentique Prospect was discovered in 2019 by a soil sampling campaign that was conducted in the Peranggih area between December 2018 and March 2019 to identify additional oxide exploration targets.
The campaign delineated a 1.8km by 0.8km gold soil anomaly located 1km west of the Peranggih deposit on a parallel north west - south east trending structure, with a peak value of 103ppb Au. Infill soil sampling, trenching, and geological mapping are planned to be carried at Mentique to create drill targets and determine the nature of mineralization in this area.
The northward extension of Peranggih-Mentique has not been adequately explored and is predominantly covered by thick jungle and forest reserve. Alluvial gold is known to exist extensively within the north trending Sungai Serau catchment, especially at its tributary, Sungai Cadu and the surrounding area. This shows the continuity of the mineralized structure, 30km north of the current known mineralization at Selinsing.
Near Mine Exploration
Selinsing/Buffalo Reef/Felda Block 7
The Selinsing and Buffalo Reef mineralization is north-south oriented and 1km east of the Raub-Bentong Suture. At Selinsing, the local structuring controls the shearing vein mineralisation and contains Permian sedimentary rocks and volcanic tuffs, contacting with limestone. The mineralised shear zone rocks consist of a series of finely interbedded argillites and very fine-grained arenites, sequences of quartz-rich variably silicified sediments, and a few thin beds of quartzite conglomerate. At the Buffalo Reef deposits the rocks are more clayey.
The geochemical characteristics of rocks within the tuffaceous package is most likely the reason this unit is strongly altered and mineralised. It appears a grain size is responsible for the hydrothermal fluid through the deposit and the formation of the orebodies. The orbodies show a correlation between increase in grain size and the intensity of alteration and veining.
The East-Northeast steeply dipping shear zones adjacent and within the deposits at Selinsing and Buffalo Reef are the primary structural controls on mineralisation. These steep shear zones are conduits for mineralising fluid during regional scale hydrothermal activity causing the development of “phyllite” and highly strained lithic tuff. The orebodies have a moderate plunge North-Northwest South-Southeast and dip East-Northeast or West-Southwest that reflects the geometry of folded host rock.
Felda Block 7 is adjacent east of Buffalo Reef Central (“BRC”) and Buffalo Reef South (“BRS”), and contains the extension of the Buffalo Reef oxide and sulphide ore bodies, within the same structure.
Near Mine Exploration Program
The Selinsing near mine exploration programs aim to optimize the economic results of the sulphide project, and expand the resources and reserves under and surround the current open pit areas as the mineralization is still open in all directions.
Sulphide mineralization at Selinsing and Buffalo Reef deposits are still open down dip and along strike. Future drill programs will focus on adding resources and defining sulphide mineralization below and around the existing pits, within gap zones, and to investigate underground opportunities with deep drilling at the Selinsing Pits and extensions to the south. An underground desktop study was internally carried out indicating potential in the Selinsing area. The sulphide exploration programs include down-dip and strike/plunge extension drilling programs, resource definition drilling for BRC, Felda Block 7 and Selinsing Deep’s high-grade sulphide gold resource. Drilling at Felda Block 7 will also enable the BRS open pits to be extended at depth.