Some parts of the mineralogy and the petrology of the Enåsen gold-deposit, northern Hälsingland, Sweden are described. The gold in Enåsen is extracted from a sillimanite-rich quartzite. The rocks in the stratigraphic foot-wall of the ore are described as a part of a stratigraphic column. It is suggested that the sillimanite-quartzite is a part of an overturned stratigraphic sequence. The temperature and the pressure during the main metamorphose is determined to 620-670º C and 5-6.5 kbar by use of the mineral paragenesis and the graphite geothermometer. It is shown that the ores are of epigenetic origin and it is suggested that the different ores were formed by one continous ore-forming process. The earlier stages of the ore-formation were caracterized by a relatively homogeneous infiltration of the ore-bearing fluids. During the late stage of the ore formation, the ore-bearing fluids were restricted to localized veins. These veins are now recognized as grey sillimanite-rich veins surrounded by sulphides and as calcite-altered veins with sulphides. It is also suggested that the presence of graphite in the undermost stratigraphic level of the foot-wall reduced the water-molefraction which directly caused the deposition of the sulphides and the gold.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-442799 |
| Date | January 1987 |
| Creators | Sädbom, Stefan |
| Publisher | Uppsala universitet, Geologiska institutionen |
| Source Sets | DiVA Archive at Upsalla University |
| Language | Swedish |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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