Wall-rock alteration and tungsten and molybdenum mineralizations associated with older granites in western Bergslagen, Sweden

Geochemistry, age, and origin of the Högberget granite, western Bergslagen, Sweden

“…The geologic setting, geochemical character, metallogenic association, and age of the Högberget granite are comparable to other Late Svecofennian granites related to W-Mo deposits in western Bergslagen. Models presented by Hellingwerf & Baker (1985) and Hellingwerf et al (1987), suggesting that the W-Mo mineralizations in western Bergslagen were formed in conjunction with the emplacement of the Early Svecofennian granites, must therefore be refuted. The traditional division of Late Svecofennian and post-Svecofennian granitoids in Bergslagen has become inadequate, because recent geochronological data show that the ages of these two groups overlap with each other.…”

“…While it had been generally assumed that this type of ore is genetically related to Late Svecofennian granites (e.g., Magnusson 1940;Ohlsson 1979), it was proposed by Hellingwerf & Baker (1985) that the W-Mo deposits in Bergslagen were formed closely associated with rift-related Early Svecofermian magmatism. This hypothesis was also adopted for the Wigstrom deposit by Hellingwerf et al (1987), who interpreted the small granite plutons close to the Wigstrom deposit as "old" (i.e.…”

“…Diagram according to Meinert (1992). mation of the Yxsjoberg tungsten skarn deposit, situated 5.5 km to the west of Pingstaberg (Lindroth 1922;Magnusson 1940;Hellingwerf & Baker 1985;Billstrom et al 1988;Romer & Ohlander 1994). The age of the Pingstaberg granite was determined by zircon U-Pb to 1781±46 Ma (Billstrom et al 1988 while the age of the Yxsjoberg tungsten skarn deposit was determined by U-Pb in titanite to 1789±2 Ma (Romer & Ohlander 1994).…”

“…The geochemical characteristics of the Skalhqjden granite (Sundblad et al 1993), particularly the characteristic REE pattern, are identical with those of the Hogberget granite. The Fjallberg granite is closely related to the Sandudden tungsten skarn deposit (Ohlsson 1987) and the Skalhqjden granite is closely related to molybdenite mineralization (Hellingwerf & Baker 1985;Sundblad et al 1993). The ages of the Fjallberg and Skalhqjden granites were determined by the U-Pb in zircon method to 174831 Ma (Aberg & Bjurstedt 1986) and 1758±8 Ma (Sundblad et al 1993), respectively.…”

“…Most authors have been of the opinion that this type of mineralization was formed from hydrothermal fluids generated by magmatic intrusives, implying a contact metasomatic origin (Lindroth 1922;Magnusson 1940;Ohlsson 1979;Hellingwerf & Baker 1985;Hellingwerf et al 1987;Billström 1991;Bergman 1994). Generally, a "younger" (Lateto post-Svecofennian) generation of granites is considered responsible for the ore formation (Ohlsson 1979;Billström et al 1988; Sundblad et al 1993) although Hellingwerf & Baker (1985) and Hellingwerfet al (1987) proposed a genetic link with the "older" (Early Svecofennian) generation of granites. In addition, Plimer (1980) suggested an exhalative-sedimentary origin as an alternative model for the W-Mo mineralizations in Bergslagen.…”