Sm-Nd, U-Pb and Pb-Pb isotopic evidence for the origin of the early Proterozoic Svecokarelian crust in Finland

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Authors:Huhma, Hannu
Author Affiliations:Primary:
Geological Survey oI Finland, Espoo, Finland
Volume Title:Bulletin - Geological Survey of Finland
Source:Bulletin - Geological Survey of Finland, Vol.337, 53p. Publisher: Geologian Tutkimuskeskus, Espoo, Finland. ISSN: 0367-522X
Publication Date:1986
Note:In English. Includes appendices. 142 refs.; illus., incl. 4 tables, sketch map
Summary:The isotopic compositions together with the U-Pb ages of zircons are reported for 30 samples from different tectonic settings in Finland. Analyses on primitive mafic rocks indicate that a time-integrated LREE-depleted mantle reservoir with epsilonNd(T) from +4 to +5 existed beneath the Baltic Shield during early Proterozoic times, and was the source of some 2100 m.y. old Jatulian and 1900 m.y. old Svecofennian basalts. The U-Pb zircon age of the majority of the granitic rocks in southern and central Finland is approx 1880 m.y., whereas that for the Proterozoic granites of N Finland is approx 1800 m.y. All the granitic rocks in southern and central Finland, and therefore not close to the Archaean craton, have epsilonNd(1.9) from -1 to +3, indicating that they consist largely of newly mantle-derived material. In contrast the granitic rocks from N and E Finland, close to the Archaean craton, have epsilonNd(T) from -3 to -10, indicating a significant contribution from recycled Archaean crustal material in the Karelian domain. [R.A.H.]
Subjects:Absolute age; Archean; Cratons; Crust; Dates; Gabbros; Galena; Genesis; Granites; Igneous rocks; Instruments; Isotope ratios; Isotopes; Lead; Mantle; Mass spectroscopy; Metabasalt; Metagraywacke; Metaigneous rocks; Metals; Metamorphic rocks; Metasedimentary rocks; Nd-144/Nd-143; Neodymium; Nesosilicates; Orogeny; Orthosilicates; Paleoproterozoic; Pb-206/Pb-204; Pb-207/Pb-204; Pb/Pb; Plate tectonics; Plutonic rocks; Precambrian; Proterozoic; Radioactive isotopes; Rare earths; Sample preparation; Silicates; Sm/Nd; Spectroscopy; Stable isotopes; Subduction; Sulfides; Svecofennian; Techniques; U/Pb; Upper Precambrian; Zircon; Zircon group; Europe; Fennoscandian Shield; Finland; Scandinavia; Western Europe
Coordinates:N594500 N700000 E0314500 E0190000
Abstract Numbers:88M/2201
Record ID:2015018901
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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