Igneous and metamorphic geochronologic evolution of granitoids in the central Eastern Segment, southern Sweden
2012 (English)In: International Geology Review, ISSN 0020-6814, Vol. 54, no 5, 509-546 p.Article in journal (Refereed) Published
The Eastern Segment abutting the Transscandinavian Igneous Belt (TIB) mostly consists of rocks with overlapping igneousages. In the Eastern Segment west of Lake Vättern, granitoids of clear TIB affinity exhibit strong deformational fabrics.This article presents U–Pb zircon ages from 21 samples spanning the border zone between these deformed TIB rocksin the east, and more thoroughly reworked rocks in the west. Magmatic ages fall in the range 1710–1660 million years,irrespective of the degree of deformation, confirming the overlapping crystallization ages between deformed TIB rocks andorthogneisses of the Eastern Segment. A common history is further supported by leucocratic rocks of similar ages. Prolongedorogenic (magmatic) activity is suggested by continued growth of zircon at 1.66–1.60 Ga. Six of the weakly gneissic rocksshow zircons with cathodoluminescence-dark patches and embayments, possibly partly replacing metamict parts of oldermagmatic crystals, with 207Pb/206Pb ages dominantly between 1460 and 1400 million years, whereas three of the gneisseshave zircon rims with calculated ages of 1440–1430 million years. Leucosome formation took place at 1443 ± 9 and1437 ± 6 Ma. The minimum age of SE–NW folds was determined by an undeformed 1383 ± 4 million years crosscuttingaplitic dike. Sveconorwegian zircon growth was not found in any of the samples from the studied area. To our knowledge,1.46–1.40 Ga metamorphism affecting the U–Pb zircon system has not previously been reported this far northeast in theEastern Segment. We suggest that the E–W- to SE–NW-trending deformation fabrics in our field area were produced duringthe Hallandian–Danopolonian orogeny and escaped later, penetrative Sveconorwegian reworking
Place, publisher, year, edition, pages
2012. Vol. 54, no 5, 509-546 p.
Research subject Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
IdentifiersURN: urn:nbn:se:uu:diva-142921DOI: 10.1080/00206814.2010.543785ISI: 000301950400002OAI: oai:DiVA.org:uu-142921DiVA: diva2:388560