10.6084/m9.figshare.3453551.v1
Trond Slagstad
Trond
Slagstad
Christian Pin
Christian
Pin
David Roberts
David
Roberts
Christopher L. Kirkland
Christopher L.
Kirkland
Tor Grenne
Tor
Grenne
Greg Dunning
Greg
Dunning
Simone Sauer
Simone
Sauer
Tom Andersen
Tom
Andersen
Tectonomagmatic evolution of the Early Ordovician suprasubduction-zone ophiolites of the Trondheim Region, Mid-Norwegian Caledonides
Geological Society of London
2016
Trondheim Region
variably tectonized ophiolite fragments
volcaniclastic sequence
475 Ma
480 Ma
Plagiogranite intrusions
Tectonomagmatic evolution
Hf
481 Ma
subduction zone
Trondheim Region ophiolites
oceanic arc
trondhjemite dykes
magmatic arc
granitoid body
unradiogenic Nd
SIMS
Geology
2016-06-21 11:30:26
Dataset
https://geolsoc.figshare.com/articles/dataset/Tectonomagmatic_evolution_of_the_Early_Ordovician_suprasubduction-zone_ophiolites_of_the_Trondheim_Region_Mid-Norwegian_Caledonides/3453551
<p>The Trondheim Region ophiolites in the Mid-Norwegian Caledonides represent variably tectonized ophiolite fragments. We present
high-precision thermal-ionization mass spectrometry and secondary-ion mass spectrometry (SIMS) U–Pb zircon dates, whole-rock
geochemical and Sm–Nd data and Lu–Hf zircon analyses that permit the timing and nature of various stages in the evolution
of the ophiolite to be elucidated. Plagiogranite intrusions dated at 487 and 480 Ma have relatively juvenile Nd and Hf isotopic
compositions (ε<sub>Nd(<em>t</em>)</sub>=6.3, ε<sub>Hf(<em>t</em>)</sub>=8.2–12.4). Geochemical data indicate a subduction-zone influence, suggesting formation in an oceanic back-arc setting. At
481 Ma, a granitoid body with a relatively strong unradiogenic Nd and Hf isotopic composition (ε<sub>Nd(<em>t</em>)</sub>=−2.6 to −4.0, ε<sub>Hf(<em>t</em>)</sub>=3.8–6.4) and subduction-zone geochemical signature intruded the ophiolite. We interpret this stage to reflect the formation
or migration of an oceanic arc above a subduction zone influenced by continentally derived sediments. At <em>c.</em> 475–465 Ma, a greenstone-dominated conglomerate and volcaniclastic sequence was deposited on the eroded ophiolite, indicating
obduction between about 480 and 475 Ma. At <em>c.</em> 468–467 Ma, the deformed ophiolite and its sedimentary cover was intruded by trondhjemite dykes and shoshonitic volcanic
rocks with intermediate Nd and Hf isotopic compositions (ε<sub>Nd(<em>t</em>)</sub>=3.0–3.9, ε<sub>Hf(<em>t</em>)</sub>=4.4–10.2). We interpret this magmatism to reflect subduction-polarity reversal and establishment of a magmatic arc at the
continental margin shortly after obduction.
</p>