Comparative geochemical study on Furongian–earliest Ordovician (Toledanian) and Ordovician (Sardic) felsic magmatic events in south-western Europe: underplating of hot mafic magmas linked to the opening of the Rheic Ocean
<p>A geochemical comparison of early Palaeozoic felsic magmatic episodes throughout the south-western European margin of Gondwana is made and includes (i) Furongian–Early Ordovician (Toledanian) activities recorded in the Central Iberian and Galicia–Trás-os-Montes zones of the Iberian Massif,...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-12-01
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| Series: | Solid Earth |
| Online Access: | https://se.copernicus.org/articles/11/2377/2020/se-11-2377-2020.pdf |
| Summary: | <p>A geochemical comparison of early Palaeozoic felsic magmatic episodes
throughout the south-western European margin of Gondwana is made and
includes (i) Furongian–Early Ordovician (Toledanian) activities recorded in
the Central Iberian and Galicia–Trás-os-Montes zones of the Iberian
Massif, and (ii) Early–Late Ordovician (Sardic) activities in the Eastern
Pyrenees, Occitan Domain (Albigeois, Montagne Noire and Mouthoumet massifs)
and Sardinia. Both phases are related to uplift and denudation of an
inherited palaeorelief, and stratigraphically preserved as distinct angular
discordances and paraconformities involving gaps of up to 22 million years. The
geochemical features of the predominantly felsic Toledanian and Sardic activities
point to a predominance of magmatic byproducts derived from the melting of
metasedimentary rocks, rich in SiO<span class="inline-formula"><sub>2</sub></span> and K<span class="inline-formula"><sub>2</sub></span>O and with a peraluminous
character. Zr <span class="inline-formula">∕</span> TiO<span class="inline-formula"><sub>2</sub></span>, Zr <span class="inline-formula">∕</span> Nb, Nb <span class="inline-formula">∕</span> Y and Zr vs. Ga <span class="inline-formula">∕</span> Al ratios, and rare-earth element (REE) and
<span class="inline-formula"><sub><i>ε</i></sub></span>Nd<span class="inline-formula"><sub>(<i>t</i>)</sub></span> values suggest the contemporaneity, for both phases, of two
geochemical scenarios characterized by arc and extensional features evolving
to distinct extensional and rifting conditions associated with the final
outpouring of mafic tholeiite-dominant lava flows. The Toledanian and
Sardic magmatic phases are linked to neither metamorphism nor penetrative
deformation; on the contrary, their unconformities are associated with
foliation-free open folds subsequently affected by the Variscan deformation.
The geochemical and structural framework precludes subduction-generated
melts reaching the crust in a magmatic arc-to-back-arc setting and favours
partial melting of sediments and/or granitoids in the lower continental crust
triggered by the underplating of hot mafic magmas related to the opening of
the Rheic Ocean.</p> |
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| ISSN: | 1869-9510 1869-9529 |