An updated genetic model for metamorphosed and deformed, c. 1.89 Ga magnesian Zn-Pb-Ag skarn deposits, Sala area, Bergslagen, Sweden
Document identifier: oai:DiVA.org:ltu-75923
Keyword: Natural Sciences,
Earth and Related Environmental Sciences,
Geology,
Naturvetenskap,
Geovetenskap och miljövetenskap,
Geologi,
Ore Geology,
MalmgeologiPublication year: 2019Abstract: This contribution presents an updated view on the genesis of stratabound Zn-Pb-Ag mineralization in the Sala area, Bergslagen, Sweden. Integrated legacy and new geological, geochemical and geophysical data reveal that the deposits are hosted by a complex array of magnesian skarn-altered zones in dolomitic marble. These mineralized zones parallel early faults and metavolcanic interbeds in the host marble, and converge downwards in the stratigraphy adjacent to a 1.89 Ga calc-alkaline granite-granodiorite batholith. Prograde alteration involved formation of early barren ferroan diopside- and forsterite-bearing skarns. Mineralization is mainly associated with subsequent alteration to tremolite, chlorite, serpentine, magnetite and calcite. The hydrous associations overlap mineralogically with assemblages formed during subsequent greenschist facies regional metamorphism between 1.87 Ga and 1.8 Ga. However, ferroan diopside and forsterite are unique to the alteration system, and indicate mineralization in conjunction with an early, high T, metasomatic alteration event at 1.89 Ga. The Sala deposits can be classified as Zn skarn deposits, albeit atypical in the magnesian nature of the skarns and the lack of minerals with essential Mn. The Fe and Mn content in magnesian silicates and carbonates is however sufficient to induce clear enrichment haloes of these elements around the deposits. The magnesian nature of the skarns probably reflect formation in a shallow marine continental backarc tectonic setting, and an importance of seawater in early pre-skarn alteration stages, such as dolomitization.
Authors
Nils F Jansson
Luleå tekniska universitet; Geovetenskap och miljöteknik
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Rodney L Allen
Volcanic Resources AB
Other publications
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Göran Skogsmo
Björka mineral AB
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Nils Vorbrodt
Björka mineral AB
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Mattias Bäckström
Björka mineral AB
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>>
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identifier: oai:DiVA.org:ltu-75923
datestamp: 2021-04-19T12:54:28Z
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recordCreationDate: 2019-09-09
identifier: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75923
titleInfo:
@attributes:
lang: eng
title: An updated genetic model for metamorphosed and deformed c. 1.89 Ga magnesian Zn-Pb-Ag skarn deposits Sala area Bergslagen Sweden
abstract: This contribution presents an updated view on the genesis of stratabound Zn-Pb-Ag mineralization in the Sala area Bergslagen Sweden. Integrated legacy and new geological geochemical and geophysical data reveal that the deposits are hosted by a complex array of magnesian skarn-altered zones in dolomitic marble. These mineralized zones parallel early faults and metavolcanic interbeds in the host marble and converge downwards in the stratigraphy adjacent to a 1.89 Ga calc-alkaline granite-granodiorite batholith. Prograde alteration involved formation of early barren ferroan diopside- and forsterite-bearing skarns. Mineralization is mainly associated with subsequent alteration to tremolite chlorite serpentine magnetite and calcite. The hydrous associations overlap mineralogically with assemblages formed during subsequent greenschist facies regional metamorphism between 1.87 Ga and 1.8 Ga. However ferroan diopside and forsterite are unique to the alteration system and indicate mineralization in conjunction with an early high T metasomatic alteration event at 1.89 Ga. The Sala deposits can be classified as Zn skarn deposits albeit atypical in the magnesian nature of the skarns and the lack of minerals with essential Mn. The Fe and Mn content in magnesian silicates and carbonates is however sufficient to induce clear enrichment haloes of these elements around the deposits. The magnesian nature of the skarns probably reflect formation in a shallow marine continental backarc tectonic setting and an importance of seawater in early pre-skarn alteration stages such as dolomitization.
subject:
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lang: eng
authority: uka.se
topic:
Natural Sciences
Earth and Related Environmental Sciences
Geology
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lang: swe
authority: uka.se
topic:
Naturvetenskap
Geovetenskap och miljövetenskap
Geologi
@attributes:
lang: eng
authority: ltu
topic: Ore Geology
genre: Research subject
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lang: swe
authority: ltu
topic: Malmgeologi
genre: Research subject
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Published
5
ISBN för värdpublikation: 978-0-85261-962-9
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Jansson
Nils F
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Luleå tekniska universitet
Geovetenskap och miljöteknik
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Allen
Rodney L
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affiliation: Volcanic Resources AB
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Skogsmo
Göran
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affiliation: Björka mineral AB
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Vorbrodt
Nils
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Bäckström
Mattias
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affiliation: Björka mineral AB
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titleInfo:
title: Proceedings of the 15th SGA Biennial Meeting 27-30 August
part:
extent:
start: 166
end: 169
originInfo:
dateIssued: 2019
publisher: University of Glasgow Publicity Services
location:
url: http://ltu.diva-portal.org/smash/get/diva2:1349675/FULLTEXT01.pdf
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form: electronic
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