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| DOI | 10.4067/S0718-71062010000100001 | ||||||
| Año | 2010 | ||||||
| Tipo | artículo de investigación |
Citas Totales
Autores Afiliación Chile
Instituciones Chile
% Participación
Internacional
Autores
Afiliación Extranjera
Instituciones
Extranjeras
Four Middle-to-Late Miocene barren plutonic complexes that occur between the giant porphyry copper deposits of the central Chilean Andes were selected for U-Pb LA-ICPMS geochronology and Hf-isotope systematics on single zircon grains. Major and trace elements and Sr-Nd-Hf isotope whole rock geochemical studies were undertaken to compare with Slightly Younger or coeval barren and fertile intrusive rocks between 32 degrees and 34 degrees S. The studied granitoids yield resolvable crystallization ages of 11.3+/-0.1 Ma (Cerro Meson Alto massif), 10.3+/-0.2 Ma (La Gloria pluton), 14.9+/-0.2 Ma/14.9+/-0.1 Ma (Yerba Loca stock) and 11.2+/-0.1 Ma/14.7+/-0.1 Ma (San Francisco Batholith). Major and trace elements discard an adakitic signature as suggested for coeval porphyric intrusions at 32 degrees S, slightly Younger mineralized porphyries at Rio Blanco-Los Bronces deposit and other Cenozoic adakites. Volcanic host rocks are less fractionated than the intrusive rock units. The same observation can be made for the unmineralized northern plutons compared to the Southern ones. Initial Sr-Nd isotope data show insignificant variation (0.703761-0.704118 and 0.512758-0.512882), plotting in the mantle array. Trace element enrichment can be explained by addition of subducted-slab fluids and/or terrigenous sediments to the mantle wedge prior to and/or slight crustal input during magma ascent. Zircon grains separated from these barren intrusives share a similar initial epsilon Hf-data variation for the younger age group ( 10- 12 Ma; 7.04-9.54) and show a more scattered range for the older one (14-15 Ma; 8.50-15.34) both sets plot between the DM and CHUR evolution lines. There is evidence that magma evolution was slightly distinct through time from older to younger barren magmatism, compared to a few fertile porphyritic rocks from Rio Blanco-Los Bronces porphyry copper deposit. It is suggested that chronological inconsistencies within these complexes might be related to differential shortening across the NE-SW-trending Yeso Valley transfer fault, assumed as coeval, which also explains the local lack of easterly magmatic arc front migration.
| Ord. | Autor | Género | Institución - País |
|---|---|---|---|
| 1 | Deckart, K. | Mujer |
Universidad de Chile - Chile
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| 2 | GODOY-PIRZIO BIROLI, ESTANISLAO FRANCISCO | - | |
| 3 | Bertens, Alfredo | Hombre |
Royal Holloway Univ London - Reino Unido
Royal Holloway University of London - Reino Unido Royal Holloway, University of London - Reino Unido |
| 4 | Jerez, Daniela | Mujer |
Oficina 803 - Chile
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| 5 | Saeed, Ayesha | Mujer |
Macquarie Univ - Australia
Macquarie University Sydney - Australia Macquarie University - Australia |
| Fuente |
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| FONDECYT |
| Fundación Andes |
| ARC LIEF |
| DEST, Macquarie University and Industry |
| ARC National Key Centre for Geochemical Evolution and Metallogeny of Continents |
| Agradecimiento |
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| This study was financed through the Fundacion Andes Project No. C-13960/32. Geologists M. Farias and A. Fock are thanked for assistance during field trips and J. Vargas for sample preparations in the facility of the Geology Department, University of Chile. We would like to thank N. Pearson and W. Griffin for supplying analytical work at GEMOC, Australia and F. Barra for the Os data on magnetite at the University of Arizona, USA. We appreciate the constructive comments of S.M. Kay and J.-P. Liegeois on a prior version of this manuscript. The authors acknowledge the critical review by S.M. Kay, R. Pankhurst and D. Morata. J. Le Roux is friendly thanked for having checked the English of this paper. This research used instrumentation funded by ARC LIEF and DEST Systemic Infrastructure Grants, Macquarie University and Industry. This is the contribution No. 618 from the ARC National Key Centre for Geochemical Evolution and Metallogeny of Continents. We acknow-ledge willingness from FONDECYT project 1095099 to include our results into its modelling. |