Lu–Hf geochronology of ultra-high-pressure eclogites from the Tromsø-Nappe, Scandinavian Caledonides: evidence for rapid subduction and exhumation
Martinet, I.
Miladinova, I.
Sprung, P.
Froitzheim, N.
Fonseca, R. O. C.
Münker, C.
Janák, M.
Kullerud, K.
DOI: https://doi.org/10.1007/s00531-020-01866-0
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/10614
Martinet, I.; Institute of Geology and Mineralogy, University of Cologne, Cologne, Germany
Miladinova, I.; Institute of Earth Sciences, NAWI Graz Geocenter, University of Graz, Graz, Austria
Sprung, P.; Abteilung Hotlabor, Paul Scherrer Institut, Villigen, Switzerland
Froitzheim, N.; Institute of Geosciences, University of Bonn, Bonn, Germany
Fonseca, R. O. C.; Institute of Geology and Mineralogy, University of Cologne, Cologne, Germany
Münker, C.; Institute of Geology and Mineralogy, University of Cologne, Cologne, Germany
Janák, M.; Earth Science Institute, Slovak Academy of Sciences, Bratislava, Slovak Republic
Kullerud, K.; Norwegian Mining Museum, Kongsberg, Norway
Abstract
Geochronology of ultra-high-pressure metamorphic rocks is able to constrain the timing and rates of subduction-zone processes. Lu–Hf garnet dating has the potential to yield information about the timing of the prograde evolution of subducting rocks under increasing pressure. In combination with other methods, it thus allows constraining the complete P–T–t path with high precision. Ultra-high-pressure eclogites from the Tromsø Nappe, the structurally highest tectonic unit of the Scandinavian Caledonides in northern Norway, were dated using Lu–Hf geochronology on garnet. A sample from Tromsdalstind yielded an age of 448.3 ± 3.6 Ma, interpreted as dating prograde garnet growth due to preserved zoning in the major-element and Lu contents of garnet grains. A sample from the diamond-bearing locality Tønsvika yielded an identical age of 449.4 ± 3.3 Ma. Garnet from this sample shows a weak zoning in Ca content and near-homogeneous Lu content. These ages are identical within error among each other and with published U–Pb ages of peak-eclogite-facies zircon and rutile/titanite from exhumation-related leucosome veins. Consequently, the entire subduction–exhumation cycle leading to the ultra-high-pressure eclogites lasted only very few millions of years during the Late Ordovician.