1.90-1.88Ga arc magmatism of central Fennoscandia: geochemistry, U-Pb geochronology, Sm-Nd and Lu-Hf isotope systematics of plutonic-volcanic rocks from southern Finland

Geologica Acta

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Title 1.90-1.88Ga arc magmatism of central Fennoscandia: geochemistry, U-Pb geochronology, Sm-Nd and Lu-Hf isotope systematics of plutonic-volcanic rocks from southern Finland
 
Creator KARA, J.
VÄISÄNEN, M.
JOHANSSON, Å.
LAHAYE, Y.
O'BRIEN, H.
EKLUND, O.
 
Subject Fennoscandian shield; Svecofennian orogeny; Lu-Hf; U-Pb; Sm-Nd; geochemistry
 
Description The earliest Svecofennian magmatism in southern Finland has been dated at 1.90-1.88Ga. As an example of this, the Orijärvi (ca. 1.89Ga) and Enklinge (ca. 1.88Ga) volcanic centres comprise bimodal plutonic batholiths surrounded by volcanic rocks of comparable ages and chemical compositions. Here, we report geochemical and Sm-Nd isotope data from intrusive and extrusive samples, combined with zircon U-Pb and Lu-Hf isotopes for granodiorites from both study areas. The samples range from gabbros to granites and indicate a subduction-related continental margin setting. The zircons from the Orijärvi granodiorite define an age of 1892±4Ma whereas the Enklinge granodiorite yields an age of 1882±6Ma. Several inherited ages of 2.25-1.95Ga as well as younger ages of 1.86-1.80Ga were found in the Enklinge granodiorite. The initial εNd values from the mafic rocks from both locations fall in the range +1.1 to +2.9 whereas the felsic rocks exhibit initial εNd values of -0.4 to +1.2. The magmatic zircons from the Orijärvi and Enklinge granodiorites show average initial εHf values of -1.1 (at 1892Ma) and zero (at 1882Ma), respectively, each with a spread of about 7 ε-units. The initial εHf values for the inherited zircons from Enklinge range from +3.5 to +7.6 with increasing age. The Sm-Nd data indicate that the mafic rocks were derived from a “mildly depleted” mantle source while the felsic rocks show larger crustal contribution. Also, the variation in εHf values indicates minor mixing between mildly depleted mantle derived magmas and crustal sources. U-Pb ages and Hf isotopes for inherited zircons in the Enklinge granodiorite suggest the presence of juvenile Svecofennian “proto-crust” at depth.
 
Publisher Geologica Acta
Geologica Acta
Geologica Acta
 
Contributor Finnish Cultural Foundation
Turku University Foundation
SYNTHESYS: European Community –Research Infrastructure Action
 
Date 2016-10-09
 
Type info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion

 
Format application/pdf
 
Identifier http://revistes.ub.edu/index.php/GEOACTA/article/view/GeologicaActa2018.16.1.1
10.1344/GeologicaActa2018.16.1.1
 
Source Geologica Acta; Vol 16, No 1; 1-23, I-XIV
Geologica Acta; Vol 16, No 1; 1-23, I-XIV
Geologica Acta; Vol 16, No 1; 1-23, I-XIV
1696-5728
1695-6133
 
Language eng
 
Relation http://revistes.ub.edu/index.php/GEOACTA/article/view/GeologicaActa2018.16.1.1/22435
http://revistes.ub.edu/index.php/GEOACTA/article/downloadSuppFile/GeologicaActa2018.16.1.1/2317
http://revistes.ub.edu/index.php/GEOACTA/article/downloadSuppFile/GeologicaActa2018.16.1.1/2318
 
Coverage Fennoscandia; Southern Finland
Paleoproterozoic; Svecofennian
Plutonic; Volcanic
 
Rights Copyright (c) 2017 Geologica Acta
 

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