Provenance and exhumation of an exotic eclogite-bearing nappe in the Caledonides: a U–Pb and Rb–Sr study of the Jæren nappe,
SW Norway
M.A. Smit
M. Bröcker
E. Kooijman
E.E. Scherer
10.6084/m9.figshare.3454952.v1
https://geolsoc.figshare.com/articles/dataset/Provenance_and_exhumation_of_an_exotic_eclogite-bearing_nappe_in_the_Caledonides_a_U_Pb_and_Rb_Sr_study_of_the_J_ren_nappe___SW_Norway/3454952
<p>The provenance and exhumation history of paragneisses that enclose the 471–458 Ma eclogites in the Caledonian Jæren nappe,
SW Norway, were constrained by performing U–Pb analysis on detrital zircon and Rb–Sr dating of mica. Zircon grains from four
samples were analysed by laser ablation inductively coupled plasma mass spectrometry, providing detrital U–Pb ages between
3130 and 620 Ma. These data suggest Laurentian provenance, implying the existence of an early Caledonian (Taconian) HP fragment
of Laurentian crust in the southern Scandinavian Caledonides. Several rims and recrystallized zircon patches yielded U–Pb
ages averaging at 469 ± 6 Ma (2σ). These are identical to the Lu–Hf ages of the eclogites and underscore the importance of
Taconian metamorphism in this part of the Caledonides. The main phengite Rb–Sr age cluster at 424.4 ± 4.6 Ma provides time
constraints on the amphibolite-facies recrystallization of former high-Si phengite. Five out of seven biotite Rb–Sr ages were
identical, yielding a weighted mean age of 413.6 ± 2.6 Ma. Low-Si phengite and biotite in three samples gave <em>c</em>. 400 Ma ages. The Rb–Sr data record the mid-crustal emplacement of the exotic Jæren nappe and its subsequent unroofing along
the western edge of Baltica during the backsliding and collapse of the Scandian orogenic front.
</p>
2016-06-21 12:27:51
Rb
SW Norway
recrystallized zircon patches
Caledonide
laser ablation inductively
plasma mass spectrometry
phengite
400 Ma ages
HP
Scandian orogenic front
Caledonian J æren nappe
Geology