Hf and Nd isotopes in Early Ordovician to Early Carboniferous granites as monitors of crustal growth in the Proto-Andean margin of Gondwana
We report the first study integrating in situ U-Pb and Hf isotope data from magmatic zircon and whole-rock Sm-Nd isotope data for granitic rocks of the Sierras Pampeanas, Argentina, in order to evaluate the Palaeozoic growth of the proto-Andean margin of Gondwana. Early-Middle Ordovician granitic ma...
| Authors: | , , , , , , , |
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| Format: | article |
| Status: | Published version |
| Publication Date: | 2013 |
| Country: | Argentina |
| Institution: | Consejo Nacional de Investigaciones Científicas y Técnicas |
| Repository: | CONICET Digital (CONICET) |
| Language: | English |
| OAI Identifier: | oai:ri.conicet.gov.ar:11336/14486 |
| Online Access: | http://hdl.handle.net/11336/14486 |
| Access Level: | Open access |
| Keyword: | CRUSTAL GROWTH HF AND ND ISOTOPES PROTO-ANDEAN MARGIN OF GONDWANA U-PB DATING ZIRCON https://purl.org/becyt/ford/1.5 https://purl.org/becyt/ford/1 |
| Summary: | We report the first study integrating in situ U-Pb and Hf isotope data from magmatic zircon and whole-rock Sm-Nd isotope data for granitic rocks of the Sierras Pampeanas, Argentina, in order to evaluate the Palaeozoic growth of the proto-Andean margin of Gondwana. Early-Middle Ordovician granitic magmatism is by far the most voluminous of the Sierras Pampeanas and represents the most significant magmatic event. These calc-alkaline granitoids were intruded at an active continental margin. εHft values range from -3.3 to -14.7 and εNdt from -3.3 to -6.3 (t=473Ma), with average TDM Hf and TDM Nd ranging from 1.5 to 2.2Ga and 1.4 to 1.7Ga, respectively. Middle-Late Devonian magmatism occurred in the foreland, away from the orogenic front in the west, and included F-U-REE rich A-type granites. The Achala granite, the largest batholith in the Sierras Pampeanas, has εHft and εNdt values ranging from -3.6 to -5.8 and -4.0 to -6.5, respectively (t=369Ma). Small scattered Early Carboniferous A-type granite plutons were intruded in a dominantly extensional setting and have εHft and εNdt values ranging from -6.7 to +2.2 and -0.5 to -3.6, respectively (t=341Ma). The generation of Ordovician and Devonian magmas dominantly involved crustal reworking and stabilization rather than the formation of new continental crust by juvenile material accretion, whereas Carboniferous magmatism resulted in part from reworking of supracrustal material, but with variable addition of juvenile magmas. © 2012 International Association for Gondwana Research. |
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