The Hampyeong project covers the western sector of a 120 sq. km Cretaceous volcano-sedimentary basin that is bounded by the north-east trending transpressional Yeongdong Fault Zone of the Ogcheon Fold Belt. No prior drilling or systematic exploration has occurred on the area prior to Southern Gold’s exploration efforts.
Korean Government Geological Organisation (KIGAM) mapping suggests there are a number of small porphyry feeder plugs. These intrusions are probably part of the Cretaceous Bulgugsa igneous event and have been interpreted to be responsible for the generation of hydrothermal systems and potential epithermal gold mineralisation. The “pull-apart” basin is interpreted to be a fault bounded graben structure, with the western boundary a fault contact with Jurassic Daebo granitoids.
Preliminary field reconnaissance and mapping in May 2017 identified several corridors of hydrothermal alteration. Furthermore, a number of new epithermal quartz vein structures have been identified, including the A’Cha vein, which shows a true width >8 m wide of epithermal quartz veining. Two granted tenement blocks have been acquired over historic workings (Figure 1). The Hampyeong area was selected as a high priority target and a further series of tenement blocks was applied for (Figure 1).
On the basis of the preliminary program of field mapping and sampling, the Naju 136 tenement block was granted early in 2018. The detailed field mapping had revealed numerous targets within kilometre-scale low sulphidation epithermal gold-silver mineralised structurally controlled quartz veins and vein/breccia zones (Figure 2, central inset). High assay results have returned up to 13.4 g/t Au and 27.7 g/t Ag (see Table 1) with several high-grade samples returned from the Nabi and Saseun Vein Zones in particular.
Key geological and structural features that are highly prospective for gold-silver epithermal mineralisation have been recognised and further work, including drilling was planned to progress the target area. There were several, encouraging reasons why this area was selected as being so prospective:
- The area exhibits a good macro-structural context with the right ‘plumbing system’ for the potential to emplace significant precious metal deposits;
- Significant grades of gold and silver are being returned at surface in a district that has never been drill tested;
- The veins systems display good vein widths and there are several of these across a large area and along strike in vein corridors;
- Systematic exploration over the area has helped define several ‘walk up’ drill targets; and
- The topography of the area allows for easy access and relatively straight forward drill testing.
Figure 1: Hampyeong project geology and tenements.
Table 1: Rock Sample Assays (>1.0 g/t Au) from rock samples at Hampyeong (Naju 136 block).
Figure 2: Hampyeong project geology and surface sampling.
A maiden diamond drilling program was completed at Hampyeong in May 2018, with this round of drilling targeting the A’Cha and Nabi quartz veins hosted within Cretaceous volcanic rocks and a granitoid.
Drilling intersected gold mineralisation in all three holes with a peak result of 0.95m @ 5.33 g/t Au from 32.6 m from the Nabi Vein Zone (Table 2, Figure 3 and 6).
A three-hole, 276 m maiden scout diamond drilling program targeting the A’Cha and Nabi quartz vein zones is complete. Drilling has been conducted with environmental and social considerations, including consultation with the local village, noise reduction measures and monitoring, sediment traps and pre-approved documented rehabilitation plans submitted to local council (Figure 3). The approval for the program required a pre-drilling report with registered surveyors documenting land clearance and proposed rehabilitation programs and forms part of the permitting processes.
Broad intervals (>10m) of A’Cha quartz vein breccia and anomalous gold were intersected in all three drillholes (Figures 4, 5 and 6). The A’Cha vein is a deep-level, low-sulphidation epithermal quartz vein and vein breccia system hosted predominately by sericite-illite-pyrite ± silica altered felsic volcanics and volcaniclastics. Vein textures indicate multiple phases of vein development and hydraulic brecciation with minor pyrite and trace sphalerite and galena present in certain phases of veining. The peak gold result returned from drilling of the A’Cha vein zone was 0.70 m @ 2.47 g/t Au from 119 m in HPDD003 with the vein open in all directions.
The secondary drill target was the Nabi vein zone that has peak surface rock chip results of up to 13.4 g/t Au. Drillhole HPDD003 successfully intersected the Nabi quartz vein down-dip of surface exposure, returning 0.95 m @ 5.33 g/t Au from 32.6m downhole. The Nabi vein is an epithermal quartz vein and vein breccia hosted system within a silica-sericite-clay altered granitoid. The Nabi vein remains open in all directions, and additional core samples are being taken to confirm the potential extents of mineralisation into the hangingwall and footwall to the veins.
Table 2: Hampyeong Diamond drill program best intercepts (>.
All interval widths are downhole widths, unless otherwise stated.
Figure 3: Hampyeong project geology, surface sampling and diamond drill traces.
Figure 4: Cross-section of HPDD001, A – A-1.
Figure 5: Cross-section of HPDD002, B – B-1.
Figure 6: Cross-section of HPDD003, C – C-1. Geology in Figures 3, 4, and 5 are the same as Figure 3.
Southern Gold is highly encouraged by the results that have been achieved at Hampyeong. The initial three-hole scout drill program has confirmed the continuity of quartz veining mapped and sampled at surface, and the overall significant strike extent as well as the down dip continuity. The majority of results returned from the A’Cha vein show wide intervals of sub 0.5 g/t Au, confirming the kilometre-scale structure is anomalously mineralised. All veining intercepted remains open along strike and down dip. Potential future work at the Hampyeong project will focus on further drill testing the Nabi and A’Cha veins along strike and down dip, and first-round drill testing of the Saseun vein that outcrops about 4 m wide and reports surface rock chip results up to 6.8 g/t Au.
The Hampyeong project is located in the south-western part of South Korea, within the Okcheon Fold Belt proximal to the country-transecting Yeongdong Fault, and is hosted within a 100 square kilometre pull-apart Cretaceous volcanic basin (Figure 1, central inset). These are the same belt-scale host rocks to the currently producing Eunsan-Moisan epithermal gold-silver mines 60 km to the south, and Weolyu, 175 km to the north-east. The Eunsan-Moisan deposits were a maiden discovery by Ivanhoe Mines in early 2000 and are now currently producing 90 % of South Korea’s gold and silver. A google earth image of the Eunsan mine is also shown on Figure 1 to demonstrate deposit and operational scale.
The A’Cha and Saseun Vein corridors are located along the southwestern flank of a Cretaceous Volcanic Basin. The basin’s south-eastern margin is bounded by the Yeongdong Fault, a deep-seated tectonic-scale northeast-southwest sinistral step fault (see Figure 1, central inset).
Both the A’Cha and Saseun Vein corridors are large gold-silver mineralised vein systems that display excellent structural continuity, significant outcropping widths and kilometre-scale strike lengths, plus show evidence of localised high-grade shoot development. The vein corridors are most likely sinistral fault sets that host a jog-like upward thickening wedge between them, the Nabi Vein Zone.
This mineralised wedge hosts a complex sequence of well-developed multi-directional quartz veining, with a maximum width of approximately 200 metres where mapped in detail. Northeast-southwest and minor northwest-southeast striking veins within this wedge have been noted intersecting the A’Cha Lode Zone at North Ridge and immediately north of the Main Vein, with increased gold values indicative of localised shoot development.
Lode textures indicate an early crackle to rotational brecciation event, followed by at least two phases of hydraulic over-pressuring and crystalline quartz flooding, cut by several phases of later discrete multi-orientation quartz veining. It is likely that the intersection zones of these veins with the lode structures localise the high-grade gold and silver values.
Figure 7: KRS202218. 13.40g/t Au, 27.70g/t Ag. Nabi Vein - vein breccia with silicified & strongly limonitic granitoid fragments flooded by crystalline quartz veins.
Figure 8: KRS202212. 11.50g/t Au, 16.20g/t Ag. East of Main Vein - vein breccia, crystalline interlocking quartz with ghosted limonite-rimmed wallrock fragments to 0.5 cm.
Figure 9: KRS202237. 4.61g/t Au, 1.30g/t Ag. Saseun Vein – vein breccia, silica-sericite altered, limonitic rhyolitic tuff breccia; cut by crystalline quartz veining with intense limonite staining.
Figure 10: KRS202233. 1.50g/t Au, 10.10g/t Ag. South of Main Vein - Hydraulically brecciated, silica-sericite altered, limonitic rhyolite; flooded and cut by crystalline quartz veining.