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http://hdl.handle.net/10174/13502
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Title: | Chronological link between deep-seated processes in magma chambers and eruptions: Pemo-Carboniferous magmatism in the core of Pangaea (southern Pyrenees) |
Authors: | Pereira, M.Francisco Castro, Antonio Chichorro, Martim Fernandez, Carlos Diaz-Alvarado, Juan Marti, Joan Rodriguez, Carlos |
Issue Date: | 2014 |
Publisher: | Elsevier |
Citation: | Pereira et al., 2014. Chronological link between deep-seated processes in magma chambers and
eruptions: Permo-Carboniferous magmatism in the core of Pangaea
(Southern Pyrenees). Gondwana Research 25: 290–308 |
Abstract: | In the Southern Pyrenees there are Upper Carboniferous–Lower Permian sedimentary basins with a significant
volume of volcanic material derived from explosive eruptions (rhyolitic ignimbrites and andesitic flows).
These basins are spatially associated with granodiorites and dacitic dykes emplaced in Variscan basement
rocks. U–Pb SHRIMP dating of zircons extracted from three granodiorites, an andesitic flow, a dacitic dyke
and six ignimbrites, revealed that magmatism occurred over an extended period of thirty eight million
years, from ca. 304 Ma to ca. 266 Ma (Upper Carboniferous–Middle Permian). A scattering of zircon ages in
each sample shows that the history of melt crystallization was complex, with more than one zircon-forming
event in each magma chamber. The prolonged crystallization history was transferred to the product of the
eruptions. A chronological link between the deep-seated magma chambers and processes in eruptions was
identified on the basis of four overlapping intervals at: ca. 309–307 Ma (Upper Carboniferous), ca. 304–
296 Ma (Upper Carboniferous–Lower Permian), ca. 294–282 Ma (Lower Permian), and ca. 276 Ma (Lower
Permian). The variation of zircon U/Th ratios exposes a tendency for an increase in mafic sources as crystallization
advances in the Permian. Zircons probably crystallized from melt phases related to both a felsicintermediate
metaluminous source from ca. 310–293 Ma (mostly 0.1 b Th/U b 0.6) to ca. 289–273 Ma (especially
in the range 0.6 b Th/U b 1) and a mafic source (mostly 1.2 b Th/U b 1) at ca. 266–265 Ma. U–Pb zircon
ages from volcanic and plutonic rocks of the Southern Pyrenees are consistent with the ages of the
post-Variscan magmatism of Iberia associated with orocline generation and subduction of the Paleotethys
Ocean (ca. 304–283 Ma), and in addition reveal a later magmatic event at ca. 276–266 Ma (Lower–Middle
Permian). The location of the Iberian orocline in the core of Pangaea and near the western end of the subduction
zone of the Paleotethys Ocean leads to the hypothesis that this later magmatic activity of the Southern Pyrenees
could provide the missing link between the Variscan and Cimmerian cycles that acted sequentially in Permo-
Carboniferous times. |
URI: | http://hdl.handle.net/10174/13502 |
Type: | article |
Appears in Collections: | GEO - Publicações - Artigos em Revistas Internacionais Com Arbitragem Científica
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