Relationships between sanukitoids and crust-derived melts and their implications for the diversity of Neoarchaean granitoids: A case study from Surmansuo and nearby areas, Eastern Finland

We present new isotopic data (U-Pb and Sm-Nd) from the Neoarchean granitoids of the Lentua complex, which is a part of the Western Karelia subprovince of the Fennoscandian Shield. Compositionally, the samples are granitoids belonging to the sanukitoid suite and K-rich granitoids. Certain samples int...

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Bibliographic Details
Published in:Bulletin of the Geological Society of Finland
Main Authors: P. Mikkola, E. Heilimo, H. Huhma
Format: Article in Journal/Newspaper
Language:English
Published: Geological Society of Finland 2014
Subjects:
sanukitoids
granites
leucogranite
partial melting
geochemistry
absolute age
isotopes
U/Pb
zircon
Archean
Neoarchean
Finland
Geology
QE1-996.5
Fennoscandian
karelia*
Online Access:https://doi.org/10.17741/bgsf/86.1.002
https://doaj.org/article/680244ee5382467a8cde0a6503c6e079
Description
Summary:We present new isotopic data (U-Pb and Sm-Nd) from the Neoarchean granitoids of the Lentua complex, which is a part of the Western Karelia subprovince of the Fennoscandian Shield. Compositionally, the samples are granitoids belonging to the sanukitoid suite and K-rich granitoids. Certain samples interpreted as partial melts of pre-existing crust in this study display more mafic compositions than previously described from the surrounding areas. This indicates, at least locally, a source poorer in SiO2 than the TTG (Tonalite-Trondhjemite-Granodiorite) suite granitoids, which are the likely sources for the majority of the anatectic granitoids within the Lentua complex. Based on new geochronological data (LA-MC-ICPMS U-Pb on zircon), the sanukitoids and anatectic granitoids are at least partly coeval (2.69 Ga) in the area, but interaction between the two felsic magmas was limited. The dated sanukitoid sample is distinctly younger (2687±8 Ma) than the average age of the sanukitoids of the Western Karelia subprovince (2718±3 Ma) indicating, together with one previously published sanukitoid age, the existence of a younger sanukitoid phase. This study gives new important constraints to understanding the formation of the Western Karelia subprovince by expanding the observed compositional heterogeneity and the temporal overlap of the different Neoarchean granitoid suites.

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