Mapping of multiple minerals in Gävleborg county

The project aims to demonstrate the geological processes that contribute to ore formation. This is done by examining various alterations, mineralisations, their relation to the stratigraphy and structures, and the structural framework and evolution of the bedrock. We also use 3D modeling to show how mineralisations and the surrounding bedrock are built up.

The investigation is conducted in four separate sub-projects, each with its specific conditions and possibilities.

Investigation of the sulfide deposits in Enåsenfältet

In the Enåsen gold-copper mine, which was in operation between 1984 and 1991, the ore minerals are disseminated in quartz-sillimanite gneiss. The occurrence has been classified by SGU as a gold deposit of national interest.

Southeast of the Enåsen gold-copper mine, there is a zone with deposits that is referred to as Enåsenfältet:

Deposit	Substance
Flomyra	Copper and gold
Enåsgruvan	Copper and silver
Ramsjögruvan, Nymyran and Felberget	Iron sulfide
Långtjärnen	Zinc

North of Enåsen, there is also Malsjöbodarna, which is a copper and iron sulfide occurrence.

Mineralised samples from outcrops, waste rock, and drill cores from all deposits in the area are analyzed. Around the Enåsen gold-copper mine, there are numerous drill holes, and many chemical analyses have been performed. A 3D model is made over the drilled part of Enåsen with the support of geophysical data. The work began in 2021.

Here you can access a report describing the background and with a summary of the first years field work (in Swedish)

Formation of the Los copper-cobalt mineralisations

The Los cobalt mine was in operation for over 30 years in the mid-1700s. The ore appears partly in a fracture zone up to 30 centimeters wide in metabasalt and can be traced for at least about 90 meters.

In the Los area, there are several mining fields, and 43 mineralisations of six different types are known:

Deposit	Substance
Losfältet and Ställstensbergets koppargruvor	Copper
Los koboltgruvor	Copper, cobalt, bismuth, nickel and arsenic
Nätsjögruvorna	Copper, lead, zinc, silver and gold
Losfältet	Copper, nickel and cobalt
Risbergets gruvor	Iron sulfide
Dåasgruvefältet, Risbergets gruvor and Björkbergs gruvor	Iron oxide

The planned activities include collecting mineralised samples from outcrops, waste rock, and drill cores from deposits in the area and better characterizing these through petrography, lithogeochemical analysis, and isotope analysis. Ore mineralogical observations and data from historical samples from the Los mines will also be collected. Structural geological investigations and geophysical measurements are carried out to enable 3D modeling in selected areas together with drill core data. This work began in 2022.

Here you can access a report describing the background and with a summary of the first years field work (in Swedish)

Investigation of the sulfide deposits in  Hamrånge group

In the Hamrånge area, which has well-preserved volcanosedimentary bedrock, there are 47 known mineralisations. These include sulfide-copper (± arsenic, gold, silver, lead, zinc, molybdenum, and iron), as well as gold, iron oxide (± arsenic, gold, silver, copper, zinc, and lead), and pegmatite containing lithium, tantalum, and niobium. For 17 of these, partial chemical analyses are available in the mineral resource database.

Several of the area's sulfide, precious metal, and iron occurrences are being investigated for the content of potential innovation critical elements in samples from outcrops, waste rock, and drill cores. If elevated levels of such elements are found, it may lead to more in-depth mineralogical and chemical investigations.

Exploration permits exist for lithium (Tasman Metals AB) and for lithium and tantalum (Leading Edge Materials). This project does not investigate this type of mineralisation. There are over 30 drill holes concentrated in an area of about 1 square kilometer around the precious metal-sulfide occurrence Rörmyran. There are good prerequisites for creating a 3D model here. Geophysical profile measurements, petrophysical sampling, and modeling are carried out. This work began in 2023.

Ore potential for the Grängsbo zinc-copper mineralisation

In the Grängsbo area, there are nine sulfide mineralisations with copper, zinc, and gold in fault breccia. There are results from the 1980s from bedrock mapping, ground magnetic field measurements, slingram, and four drillings. The proposed structure is an overturned synform; the mineralisation does not go deeper than the fold hinge. However, the hinge zone itself has not been drilled, but its distribution on the bedrock surface is interpreted from slingram data.

The mineralisation was previously interpreted as a stratiform complex mineralisation in a sedimentary environment, but after the drilling effort, it was reinterpreted as a fault-bound breccia mineralisation. In the current project, we will test and evaluate the existing model through structural geological investigation, drill core logging, and geophysical measurements. Petrophysical samples are taken to support geophysical and geological 3D modeling. Knowledge of the mineralisation is expanded through microscopic examination and chemical analyses of mineralised samples from outcrops, waste rock, and drill cores. If elevated levels of critical innovation elements (e.g., indium, gallium, or germanium) are found, it may lead to more in-depth mineralogical and chemical investigations. This work began in 2024.