THE GRUNDFORS Gold PROJECT
During its research of known gold prospects in Västerbotten Province, Goldore came across the old Grundfors goldmine, mined on a small scale in the 1920’s. Little is known about the earlier production and the old workings have caved in.
Grundfors caught the attention of Goldore due to the rumored very high grade and its location in the eastern part of the Skellefte district, the most productive gold district in Sweden.
Small and rich veins with limited environmental footprint and high value per ton are the exploration targets with the highest priority for Goldore.
Goldore now holds an exploration permit, Jakobsgroven 1, covering the old Grundfors mine itself. Immediately to the south, Goldore has applied over ground with mineralized outcrops, the Jakobsgroven 2 and Hällorna 1 permits. To cover up all potential ground, the same lithology to the south is covered by the Andersberg 1 permit.
North of the Skellefte River, the same lithology as at Grundfors is covered by the Långmyran 1 permit.
All in all, Goldore’s tenements over the Grundfors mine and its surroundings are covering 1096 hectares.
The area is centrally located just outside Skellefteå City and all permit areas are accessible by road. Power is readily available. The infrastructure must be regarded as excellent.
Still, the permit areas are all forested and in parts logged. There are no environmental issues whatsoever.
In the literature, Grundfors is sometimes referred to as Krångfors, another village nearby the old mine.
Map of Goldore’s Exploration Permits at Grundfors
Grundfors is located in the eastern part of the Skellefte district, which by several writers is interpreted as an early Proterozoic volcanic arc.
Styles of mineralization include gold rich massive sulfides (primarily in the western and central part of the district), vein-type epigenetic gold (primarily in the eastern part of the district). In addition, there are indications of porphyry copper-gold mineralization in the northwestern part of the more or less east –west trending district.
By far, the Skellefte district is economically the most significant ore district in Sweden, in respect to both base metals and gold.
Regional Geological Map
From Kathol & Weihed 2005
The famous and now mined out Boliden mine (more than 8million tons @ 15.5 g/t Au with Cu, Zn, Ag) is located around 12km northwest of Grundfors. The Boliden deposit could well be the result of epigenetic Au mineralization overprinting massive sulfides.
Volcanic rocks are dominating the central part of the Skellefte district, while the eastern part is dominated by sedimentary rocks. A north-south striking break in lithology occurs a few kilometers west of Grundfors. Several gold deposits are located near this break, such as Boliden (Boliden), Grundfors (Goldore), Åkerberg (Boliden), and Björkdal (Mandalay Resources).
Epigenetic gold deposits seem to dominate in the eastern part of the district while gold-rich massive sulfides are dominating in the central and western part of the district.
The quaternary glaciation of northern Europe resulted in deposition of till and glacifluvial sediments. Less than a percent of the bedrock in the district is actually outcropping. The use of geophysics is a must. The known mineralization at Grundfors is outcropping or found under a thin till-cover thou.
Typical terrain in the eastern part of the Skellefte district
The road at the Grundfors Prospect.
Geological map over the eastern part of the Skellefte District.
From Bergman-Weihed 2001
THE GRUNDFORS MINERALIZATION
Selected grab sampling in an old trench indeed confirmed that high grades can be found at Grundfors. Further, rumor has it that as rich material as 100g/t as head grade was mined from time to time in the 1920’s. The reported head grade was 30 g/t Au thou.
Grundfors has the potential to be a very rich gold deposit.
Mineralized outcrops can be found in a several kilometer long NNE-SSW trend.
The size potential is indeed there, considering thatGrundfors primarily is a narrow vein prospect.
Trench in fine grained mafic rock with a quartz vein and veinlets, Hällorna
In most cases, the host rock of the observed veins is amphibolite, which could well be interpreted as meta-andesite, as the Swedish Geological Survey did on the regional maps. There are also tuffs and volcanogenic conglomerate. Marine metasediments are dominating the eastern Skellefte district in general.
The lack of outcrop makes it difficult to determine the true extent of the vein-system at this early stage. There are indeed possibilities for earlier unknown veins.
Angular boulder of vuggy quartz in till.
400m straight south of the old trench, Hällorna
Outcrop of northeast trending vein, Hällorna
FURTHER WORK AT GRUNDFORS
Mapping and sampling of all available outcrops to produce an outcrop map. Structural observations will be essential.
This work should be coupled with ground magnetic measurements. The veins would be less magnetic than the surrounding amphibolite.
Around three months will be used for this work and the result to be compiled into a report, forming the basis for step 2.
Core-drilling, aiming at defining a resource. The orientation and location of the holes will depend on the results of step 1.
Bergman, J., 1992, Structural geology of Grundfors, a quartz vein related gold deposit in the Skellefte district, northern Sweden, Geologiska Föreningen i Stockholm Förhandlingar 114, 227-234.
Bergman- Weihed, J,. 2001: Palaeoproterozoic deformation zones in the Skellefte and Arvidsjaur areas, northern Sweden. In Weihed,P. (ed.): Economic geology research. Vol. 1, 1999–2000. Uppsala 2001. Sveriges geologiska undersökning C 833, pp. 46–68.
Hallberg, A., Bergman, T., Gonzalez, J., Larsson, D., Morris, G. A., Perdahl, J. A.,
Ripa, M., Niiranen, T. & Eilu, P. 2012. Metallogenic areas in Sweden. Geological
Survey of Finland, Special Paper 53, 139–206, 35 figures and 18 tables.
Högbom A. 1937. Skelleftefältet, med angränsande delar av Västerbottens och Norrbottens län, en översikt av berggrund och malmförekomster. SGU C 389. 122 p.
Kathol, B & Weihed, P., Description of regional geological and geophysical maps of the Skellefte District and surrounding areas, SGU Ba.57, 2005
Sundblad, K., Precambrian gold deposits in North-Central Sweden, excursion guide, NTNU, 1999.