Åke Johansson: Svecofennian gabbroic rocks of Roslagen, east-central Sweden
Mafic and ultramafic rocks are messengers from the mantle. Their chemical and isotopic composition yields information about the mantle source from which their magmas originated, as well as their tectonic setting. While several studies have been made on younger mafic rocks from Fennoscandia, few modern studies exist of early Svecofennian mafic rocks, such as the gabbro massifs of the Roslagen region in east-central Sweden. These gabbro massifs, with a probable age around 1.9 Ga, have been described thoroughly in the older literature when it comes to field relations, petrography and mineralogy, but modern geochemical studies are totally lacking.The purpose of the current project is to sample and analyse these grabbros geochemically, including their Sr and Nd isotope composition, in order to characterize their source and tectonic setting, as well as the composition of the early Svecofennian mantle. Geochemical analyses are done externally, whereas the isotope analyses are done in our own laboratory.
This project is supported economically by grants from the Geological Survey of Sweden (SGU) and Magn Bergvalls Stiftelse.
Results (2011)
A report of the project is available from the website of the Geological Survey of Sweden (SGU) for downloading (http://www.sgu.se/sgu/sv/fou/extern/fourapporter.html)
:
Å. Johansson, U.B. Andersson & U. Hålenius, 2011: Ultrabasic-basic intrusions of Roslagen, east-central Sweden: mineralogy and geochemistry of early Svecofennian arc cumulates. Report to SGU of project 60-1544/2007.
A manuscript is under preparation.
Contact:
Åke Johansson
Print page