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Dolerites (1.27-1.25 Ga) and alkaline ultrabasic dykes (c. 1.14 Ga) related to intracratonic rifting

Magnus Ripa and Michael B. Stephens
Dolerites (1.27-1.25 Ga) and alkaline ultrabasic dykes (c. 1.14 Ga) related to intracratonic rifting (in Sweden; lithotectonic framework, tectonic evolution and mineral resources, M. B. Stephens (editor) and J. Bergman Weihed (editor))
Memoirs of the Geological Society of London (2020) 50: 315-323

Abstract

Doleritic sills, lopoliths and dykes were emplaced into the Paleoproterozoic craton in central Sweden at 1271-1264, 1259-1256 and c. 1247 Ma, a complex temporal zonation occurring in a WSW-ENE direction. The dolerites are subalkaline to alkaline and show predominantly gabbroic, with a trend towards monzogabbroic and quartz monzodioritic, compositions. Positive epsilon (sub Nd) and epsilon (sub Hf) values suggest a significant depleted mantle component in the source volume of the parental magmas. Dyke orientations indicate extension, at least locally, in a northwesterly direction, consistent with a magma flow direction determined using the anisotropy of magnetic susceptibility values. Intracratonic rifting linked to the break-up of the supercontinent Columbia, back-arc extension above a subduction boundary in a westwards-retreating mode or a mantle plume tail above a continental hotspot have all been proposed for the tectonic setting. Renewed intracratonic rifting at c. 1.14 Ga in the coastal area in northeasternmost Sweden resulted in the emplacement of alkaline ultrabasic dykes, including carbonatites (beforsites), silico-carbonatites and lamprophyres, in a north-south direction along an older shear belt. The broader tectonic setting of this extensional event is not known.


ISSN: 0435-4052
Coden: GSLMAD
Serial Title: Memoirs of the Geological Society of London
Serial Volume: 50
Title: Dolerites (1.27-1.25 Ga) and alkaline ultrabasic dykes (c. 1.14 Ga) related to intracratonic rifting
Title: Sweden; lithotectonic framework, tectonic evolution and mineral resources
Author(s): Ripa, MagnusStephens, Michael B.
Author(s): Stephens, M. B.editor
Author(s): Bergman Weihed, J.editor
Affiliation: Swedish Geological Survey, Uppsala, Sweden
Affiliation: Lulea University of Technology, Lulea, Sweden
Pages: 315-323
Published: 2020
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 47
Accession Number: 2020-042955
Categories: Igneous and metamorphic petrologySolid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch maps
N55°15'00" - N69°15'00", E11°00'00" - E24°15'00"
Secondary Affiliation: Lulea University of Technology, SWE, Sweden
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 2020
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