Engerne
The Engerne vein gold prospect lies due east of Akordat along the main Akordat-Keren road near the village of Aderde. To the south of Engerne lies an area of alluvial cover with more exposed veins to the south (Dallas) it is possible that this ‘blue sky’ area could host additional targets.
Geology
The bedrock in the Engerne – Garsay – Ketin area is a granitic pluton that is largely covered by alluvium to the east, and variable deformed mafic to intermediate volcanic and volcaniclastic rocks in the central and western parts. The Engerne vein gold arrays appear to lie at or near the volcanic-granite contact, within a major ductile deformation zone. The volcanic rocks are well-foliated and generally trend N-S and dip to the west at 80°. The main N-S trending vein system is hosted in altered granite-tuff-diorite-basalt complex in a contact zone ~200 m wide. In addition, plagioclase-phyric basalt dikes are present within the deformation zone. In the vicinity of the vein arrays, the host rocks have variable epidote, silica, sericite, and carbonate alteration, and disseminated pyrite (plus hematite/goethite after pyrite) is present in host rocks locally.
Mineralization
The ductile deformation zone that is host to the Engerne vein gold system extends for 7.5 km strike length, and a 5 – 20m and is oriented N-S. To the southwest, Garsay-Ketin is oriented NNW-SSE, and has a ~1 km strike length. The auriferous quartz veins are shear related and are hosted within meta-granite and meta-granodiorite. The Engerne main vein system has a total of 7.5km length and 5m-20m width. The outcrop has individual quartz veins of varying length, ranging from 60m to 200m, and aligned in a N-S trend. Most veins are N-S, although a few are oriented at 400 NE to the north. Most are oriented foliation parallel and dip steeply to the west. The northern end of Engerne vein system as well as Garsay-Ketin exposed vein body are highly fractured across their strike forming 5cm thick parallel planes. . Malachite can be seen at surface and there is considerable occurrence of oxidized sulfide material both in blebs and as fracture infill.
Several parallel ductile strike-slip shear zones are encountered in the Engerne and Garsay – Ketin gold prospect areas. The major ductile shear zone that hosts the main gold bearing quartz vein system is conspicuous at the northern end of the quartz vein outcrop. It is about 20m in thickness. The meta-granite at this zone is sericite-hematite altered, fine-grained and highly schistose; with significant kaolinitization and hematitization which is manifested in an array of colors, from reddish-brown, reddish-pink, white and light yellow. Texture and grain size reduction is also noted. Moreover, sillimanite and staurolite are well-developed. At Engerne, Staurolite is preferentially oriented N-S and horizontal on the foliation plane. Sillimanite crystals are up to 2cm in length. The aluminosilicate and staurolite development indicates that the rocks were subjected to iron enrichment and alkali depletion during deformation within a strong hydrothermal system.
The massive veins at the Engerne village locality are milky white, massive with abundant rusty after sulfide material and vuggy texture. It is composed of sulfides represented largely by pyrite. Cubic boxes (after pyrites) were noted in a hand specimen, as big as 2.0 cm wide and 3.0 cm long. Traces of chalcopyrite were also noted in some specimens. Visible free gold is rarely seen within limonitised material at the southern part of the vein system. Vugs filled with limonitised and hematitised sulfides are abundant throughout the vein. Disseminated and cubic hematitised pyrites were noted in the adjacent altered host rock.
It is notable that at Adi Enjera and Degesey. Adi Enjera, 1-2km east of the Degesey and 15km south of Engerne, there is active artisanal gold mining of alluvial material. The local gold miners pan alluvial soil and collect visible gold from the residue of washed soil. The Engerne auriferous quartz vein is the nearest known bedrock gold source. Further geology and prospecting may find another source for the alluvial gold workings.
Results
In total, 25 rock chip samples from gold quartz veins were taken throughout the target area. The gold in the quartz veins range from 0.01 to 100.91 g/t. The highest gold values are 100.9 and 25.9 g/t Au. Most of the high gold values are from the central portion of the vein outcrop, mainly from the Engerne village.
Gallery
