Mencanggah Epithermal District

Updated: 300511

Initial exploration activities on the Mencanggah Epithermal District were started by Southern Arc in May 2009, involving sampling and geochemical mapping focusing on gathering detailed geo-structural data on multiple auriferous epithermal mineralized structural breccia (MSB) targets. The surface sampling work has identified at least 16 km of epithermal Au-Ag mineralization overprinting advanced argillic alteration and silica ledges. Phase 1 drilling at Mencanggah is testing a large number of MSB targets at shallow depths of approximately 50 m below surface. These targets were prioritized based on the previous detailed geological mapping and geochemical sampling.

Dr. Steve Garwin had arrived on site in May 2009 to assist in analyzing potential structural controls within the MSBs on higher-grade shoot development. This work involved an integration of all existing geological, geochemical and geophysical data and other information previously completed and compiled regarding the property.

A second, on-going DGPS mapping phase of Mencanggah has continued to focus on detailed mapping and sampling of vein phases within the MSBs at Tibu Serai, Bising and Waterfall targets. Routine infill topopgraphic control work such as creeks, ridges, and spur traverses was also carried out to facilitate processing of contour and digital terrain models for Mencanggah.

Intermediate to low-sulphidation vein phases within the MSBs are believed to be the source of most of the gold in these structures. The ongoing detailed mapping is aimed at quantifying this phase of mineralization. Surface prospecting and mapping have identifed the extent of epithermal quartz veining over a broad area 6.5 km long by up to 4.5 m wide, including an aggregate proven strike length of more than 15 km. 

Phase 1 and Phase 2 diamond drilling programs of the defined MSB targets is following the surface prospecting work and is being carried out in 2011, along with continued detailed DGPS surface mapping between Mencanggah north and Pelangan south. Preparations for the Phase 1 drilling program continue, being hampered by heavy rains and difficult access conditions, as well as some local people's concerns.

Three drilling rigs, separate from the rigs operating on the Pelangan gold prospect, have been mobilized to the Mencanggah prospect. Two medium-sized rigs capable of drilling to 400 to 450 m will be located on the Waterfall and Tibu Serai targets, respectively. The larger drill rig capable of drilling to 700 m will test the Bising target. The three rigs have been immediately set to carry out the Phase 1 drilling, and other rigs added to move to Phase 2 drilling with the objective of producing a NI 43-101 compliant resource estimate within 18 months. Therefore, another two drilling rigs have been commissioned to arrive very soon, for an initial total of five rigs operating on this very large prospect.

Phase 1 drilling at Mencanggah is testing a large number of MSB targets at shallow to medium depths of approximately 50 m to 450 m below surface. These targets were prioritized based on the previous detailed geological mapping and geochemical sampling. A total of 37 holes are planned, with fence spacing initially at a nominal 200 m, reduced locally to 100 m in well-mineralized areas. The veins are targeted to be pentrated at between 80 to 100 m down-dip of the collar point. The first 37 holes comprise a total drilling length of approximately 7,000 m, evaluating an aggregate MSB strike length of approximately 7,400 m. Subsequently, another 4,000 of drilling is intended as a follow-up in areas adjacent to areas from the first round of holes that return encouraging results.

Spectral analyses of surface rock alteration will be undertaken to establish vectoring for lithocap-related porphyry Cu-Au targets, together with ground IP/resistivity surveys, where warranted. Information gained from the drilling will also assist in the targeting of inferred porphyries below the advanced argillic capping. Four drilling sites have been located at Mahoni. These have been surveyed to generate sectional profiles in order to clear and construct the drill pads. Inclement weather affected access  further to the north of Mahoni, hence this work is ongoing. Intially a PMC200 drilling rig will be used to test this area because of the difficult access.

MSBs defined

Surface sampling and geological mapping identified up to 16 km of epithermal Au-Ag mineralization overprinting advanced argillic alteration and silica ledges. 

The Telekur Vein is located between Tebu Serai and South Raja. Initial mapping in the area identified lensoidal outcrops of multi-phase quartz breccia/stockwork over a 1 km strike length. The vein zone remains open to the northwest. Dimensions of individual vein lenses range from 50 to 120 m along strike, by 2 to 20 m width. Telekur could be the possible southern extension to the structure which hosts Raja Vein, 1.5 km to the northwest.

Tibu Serai comprises five sub-parallel northwest trending lensoidal veins within a 1,300 by 800 m area. Individual lens dimensions vary between 50 to 800 m, by 4 to 20 m thick. Semi-continuous rock chip-channel samples (1 to 5 m intervals across the vein strike) were collected at 50 m intervals along the vein. Follow-up infill chip-channel sampling and mapping has also been completed for this area.

Mapping and sampling were also carried out at Bising, with the vein being still open to the southeast. The Bising vein system comprises two major veins with east-west and north-northwest orientations. Rock chip and channel samples between 1 and 5 m lengths were collected across strike at 30 to 50 m intervals along vein lenses. Sample assays received defined an auriferous anomalous zone up to 400 m long in the southeast part of the vein, with a maximum gold value of 10.3 g/t Au. Previous Newmont trenching at this location returned 239 g/t Au from a 2 m channel sample.

Mapping along creeks within and on the periphery of the magnetic anomaly show well-exposed outcrops of fractured volcanics intruded by diorite. Altered polymictic breccias mapped on the east side of the anomaly host dacitic and rare marbleized limestone clasts. Alteration at creek level is predominantly propylitic to argillic with localized zones of moderately dense quartz-limonite stockwork in the diorite and volcanics. Silicic to argillic altered sub crops are seen on the surrounding ridges and hill tops. Magnetite is locally abundant in the diorite as disseminations and fracture-fill. Sulfides within the volcanics, diorite and breccia include variable amounts of pyrite, chalcopyrite, bornite and covellite as fracture-fill and disseminations. Localized malachite staining is also noted.

Nineteen semi-continuous chip-channel samples between 0.5 to 10 m lengths were collected from the altered diorite on the southern periphery of the anomaly. Preliminary assay results gave an average of 519 ppm Cu (maximum 1434 ppm) and 0.12 g/t Au (maximum 0.25 g/t) from the 19 assayed samples (see Mencanggah-Bising Vein System Geochemistry Compilation Map). Preliminary assay results of 181 rock chip samples collected in the central and western parts of the anomaly indicate low-level gold anomalism with a peak result of 0.56 g/t Au from an oxidized stockwork zone.

A 1.3-km long northeast trending multi-phase quartz breccia vein occurs 1 km east of Lepangan Geres. Quartz breccia lenses between 4 to 20 m wide host variable amounts of pyrite, chalcopyrite, bornite, covellite and fine-grained dark sulfides. A broad zone of silicic-argillic alteration envelopes the vein. Results from 23 submitted samples taken along the vein indicate a low to moderate level of gold anomalism, with an average of 0.46 g/t and a peak result of 1.38 g/t.

The Talat Talat Vein Zone located immediately east of Tebu Serai, comprises four sub-parallel northwest trending multi-phase quartz breccia/stockworks veins. The veins dip steeply to the southwest, with strike lengths ranging from 100 to 650 m and vein widths between of 2 to 25 m. Of 44 samples collected only two returned values greater than 0.4 g/t Au.

Lendek Bulan Vein Zone is located east of Gunayang and comprises two sub parallel northwest trending vein structures, characterized by discontinuous lenses of multi-phase quartz vein breccia and stockwork. The vein zone covers a strike length of 900 m with individual lenses between 100 and 300 m long by 5 to 70 m wide. Mineralization is characterized by partly oxidized highly siliceous vuggy quartz vein breccias and stock works, with locally up to 10% fine grained disseminated and fracture-filling cubic pyrite and lesser fine-grained dark sulfides (tellurides?). A broad oxidized silicic to argillic alteration zone is seen adjacent to the veining. Of the 46 rock samples assayed, three returned values greater than 1 g/t Au, with a peak value of 3.94 g/t Au. This vein zone is believed to be an extension of the Bising Vein.

Similarly, GPS mapping and continuous rock chip-channel sampling were previously carried out on several of the Gunayang; Aek Pertama and Lendek Bare vein targets during September 2006. One hundred and fourteen continuous rock chip samples (1 to 3 m intervals) were collected from quartz veins and altered diorite outcrops in the prospect area. Preliminary (Au only) results were received for these samples and also plotted on the  (see Mencanggah-Bising Vein System Geochemistry Compilation Map), along with results from historical Newmont soil sampling.

The Gunayang vein target comprises a northwest trending oxidized silicic alteration zone, over 1 km in strike length and open to the northwest and southeast. Discontinuous quartz vein outcrops are between 10 to 20 m wide and comprise quartz breccias with abundant iron oxides and locally disseminated sulfides. Maximum values reported to date include a chip-channel sample of 0.91 g/t Au.

The Aik Pertama-Lendek Bare area comprises six sub-parallel northwest trending veins, open to the northwest and southeast. Mapping to date has indicated vein dimensions between 400 to 1,300 m in strike length, with individual vein widths between 2 and 20 m. Veining is characterized by intensely silicified breccia clasts within a saccharoidal quartz matrix. These zones are cross-cut by quartz vein stockworks hosting black fine-grained sulfides (?tellurides). Located centrally within the vein zone is a strongly chlorite altered and brecciated quartz-feldspar porphyry. Initial results had reported a maximum tenor of 6.12 g/t Au from a 3m continuous chip sample.