Sulphur isotope data of Proterozoic molybdenites from 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.…”

“…A close genetic relationship between the Hogberget granite and the adjacent Wigstrom W-Mo skarn deposit has been proposed by several authors (Ohlsson 1979;Andersson 1986;Hellingwerf et al 1987;Bergman 1994). The Wigstrom deposit exhibits the following characteristic features, which favour a close genetic link to the Hogberget granite (Bergman 1994): skarn mineral zonation, presence of exo-and endoskarn, garnet and pyroxene compositions, and variable mineral formation temperatures.…”

“…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. Early Svecofermian).…”

“…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.…”