Journal
GONDWANA RESEARCH
Volume 14, Issue 3, Pages 451-473Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.gr.2008.04.001
Keywords
Gondwana; ferrosilicic magmatism; Late Cambrian-Early Ordovician; Iberia; Puna
Categories
Funding
- Spanish Ministry of Science and Education [CGL2004-06808-CO4]
- [PIP-NO 6103 CONICET]
- [01350/1 CIUNSA]
- [PICT No 07-38131 ANPCyT]
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One of the most intriguing characteristics of the northern (Iberia) and southern (Puna) Gondwana margins is the presence of large volumes of Late Cambrian-Early Ordovician magmatic rocks with ferrosilicic composition, i.e., rocks with high iron and silica contents (FeO>4.0 wt.%, SiO>63 wt.%) for very low contents in calcium (CaO< 1.5 wt.%). Geological and geochemical features, as well as experimental results, show that ferrosilicic magmas resulted from near-total melting (80-90%) of crustal sources of metagreywacke and chamockite affinities, possibly derived from Neoproterozoic volcanoclastic sediments and/or their granulite facies equivalents, under very high temperatures (1000 degrees C-1200 degrees C) and at pressures of 1.0 to 2.0 GPa. A plausible tectonic setting for this peculiar magmatism is a back-arc region subjected to extension, with the ferrosilicic magmas ascending from a deep cold diapir or mantle wedge plume. Rifting in the back-arc progressed until the aperture of an ocean basin (the Rheic ocean) in the northern margin of Gondwana, but became aborted in Argentina. (C) 2008 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
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