Svecofennian intra-orogenic gabbroic magmatism:
a case study from Turku, southwestern Finland

A1 Journal article (refereed)


Internal Authors/Editors


Publication Details

List of Authors: JENNI NEVALAINEN, MARKKU VÄISÄNEN, YANN LAHAYE, ESA HEILIMO, SÖREN FRÖJDÖ
Publisher: Suomen Geologinen Seura
Place: Helsinki
Publication year: 2014
Journal: Geological Society of Finland
Volume number: 86
Issue number: 2
Start page: 93
End page: 112


Abstract

Using single-grain zircon U-Pb dating by LA-MC-ICPMS and whole-rock geochemistry, we
have studied the Palaeoproterozoic gabbroic rocks from Moisio in southwest Finland.
Three ages were obtained. The interpreted intrusion age is ~1.86 Ga, which places it in
the 1.87±1.84 Ga intra-orogenic period of southern Svecofennia. The other ages, ~1.89
Ga and ~1.83 Ga, are inferred to be inherited and metamorphic ages, respectively.
The K, LREE, LILE, Fe-, P-, Ti- and F-concentrations reveal two compositionally distinct
groups: (i) an enriched monzogabbro group and (ii) a less enriched gabbro group. The
composition of the monzogabbro group resembles the other intra-orogenic intrusions
from southern Svecofennia, whereas the unrelated gabbro group is more comparable to
the synorogenic rocks in the region. The magma source the monzogabbro experienced a
subduction related carbonate metasomatism, induced by sediment subduction and
subduction erosion. Evidently, the Moisio monzogabbro represent enriched, mantle
derived magmatism in southern Svecofennia as a part of the intra-orogenic igneous
activity. The intra-orogenic magmatism is considered to have conveyed considerable
amounts of heat from the mantle into the crust contributing to subsequent lateorogenic
high-grade metamorphism.a

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