Proterozoico medio y Paleozoico inferior de la sierra de Umango, antepais andino (29°S), Argentina: edades U-Pb y caracterizaciones isotopicas.
Middle Proterozoic and Lower Paleozoic of the Sierra de Umango, Andean Foreland (29°S), Argentina: U-Pb ages and isotopic characteristics.
| dc.contributor | en-US | |
| dc.contributor | es-ES | |
| dc.creator | Varela, Ricardo | |
| dc.creator | Sato, Ana M. | |
| dc.creator | Basei, Miguel A.S. | |
| dc.creator | Siga Jr., Oswaldo | |
| dc.date | 2010-06-29 | |
| dc.identifier | http://www.andeangeology.cl/index.php/revista1/article/view/V30n2-a07 | |
| dc.identifier | 10.5027/andgeoV30n2-a07 | |
| dc.description | En el basamento cristalino de la sierra de Umango se han distinguido varias unidades igneo-metamorficas, formadas principalmente entre el Proterozoico medio y el Paleozoico inferior. Incluye ortogneises graniticos, una sucesion de esquistos y marmoles, anfibolitas, y tres plutones graniticos de reducido tamano. Se han realizado analisis quimicos de granitoides y anfibolitas, y determinaciones de edad por los metodos U-Pb y K-Ar. La edad U-Pb en circon del Ortogneis Juchi (1108 ± 13 Ma) ratifica la asignacion al Proterozoico medio por anterior datacion Rb-Sr (1030& ± 30 Ma). La edad U-Pb en circon del Granito El Penon (473 ± 17 Ma) es ligeramente mayor que la obtenida por el metodo Rb-Sr (469 ± 9 Ma), aunque concordante si se tiene en cuenta el error de las determinaciones. Las edades K-Ar sobre muscovitas del Granito El Penon (409 ± 14 y 381 ± 11 Ma) son relacionadas a deformacion y metamorfismo ocurridos en el Devonico. Los isotopos de Nd y Sr permitieron establecer diferencias entre un conjunto de unidades relacionadas con el Ciclo Grenvilliano y otro con los Ciclos Pampeano-Famatiniano. Los datos obtenidos en la sierra de Umango indican que en las Sierras Pampeanas Occidentales hay nucleos de un basamento del Proterozoico medio (Ciclo Grenvilliano), mas una sucesion de esquistos y marmoles con anfibolitas, y plutones graniticos de reducido tamano, formados en el lapso Proterozoico superior-Devonico (Ciclos Pampeano-Famatiniano). La estructura interna de mayor relevancia, formada en el Ordovicico-Devonico muestra clara vergencia tectonica occidental y estaria relacionada con laminas de corrimiento (nappes) de una tectonica colisional. Las mismas se proyectarian desde el interior orogenico (Sierras Pampeanas Orientales) hacia el contiguo antepais de una de las placas interactuantes. Las sedimentitas clasticas del Ordovicico superior-Devonico en Precordillera (cuenca de antepais) completan el escenario geodinamico. | es-ES |
| dc.description | Igneous and metamorphic units formed mainly during the Middle Proterozoic and Early Paleozoic times have been distinguished in the Sierra de Umango crystalline basement. These include granitic orthogneisses, a sequence of schists and marbles, amphibolites, and three small granitic plutons. Geochemical analyses of granitoids and amphibolites, as well as age determinations using U-Pb and K-Ar methods were carried out. The U-Pb age in zircón of the Juchi Orthogneiss (1108±13 Ma) confirms the previous Rb-Sr Mesoproterozoic dating (1030±30 Ma). The U-Pb in zircón age of El Peñón Granite (473±17 Ma) is slighty older than the Rb-Sr age (469±9 Ma). The K-Ar mouscovite dates from El Peñón Granite (409±14 and 381±11 Ma) are related to a Devonian deformation and metamorphism. On the basis of Nd and Sr isotopic characteristics, two different sets of units can be identified, one related to the Grenvillian cycle and the second to the Pampean-Famatinian cycles. According to the data obtained for the Sierra de Umango, we interpret that in this part of the Western Sierras Pampeanas there are relics of a Mesoproterozoic basement (Grenville cycle), together with more important exposures of a schists and marble succession, with amphibolites and small granitic plutons, that were formed during Late Proterozoic to Devonian times (Pampean and Famatinian cycles). The major basement structure, formed during Ordovician to Devonian, shows a clear tectonic vergence toward the west, and consists of thrust sheets (nappes) typical of collisional tectonics. These sheets are transported from the inner parts of the orogen (Sierras Pampeanas Orientales) toward the contiguous foreland of the interacting terrane. The Upper Ordovician to Devonian sedimentary rocks of the Precordillera (foreland basin) could complete the geodynamic environment. | en-US |
| dc.format | application/pdf | |
| dc.format | text/html | |
| dc.language | eng | |
| dc.publisher | Servicio Nacional de Geología y Minería | en-US |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V30n2-a07/573 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V30n2-a07/html | |
| dc.source | Andean Geology; Vol 30, No 2 (2003); 265-284 | es-ES |
| dc.source | Andean Geology; Vol 30, No 2 (2003); 265-284 | en-US |
| dc.source | 0718-7106 | |
| dc.source | 0718-7092 | |
| dc.title | Proterozoico medio y Paleozoico inferior de la sierra de Umango, antepais andino (29°S), Argentina: edades U-Pb y caracterizaciones isotopicas. | es-ES |
| dc.title | Middle Proterozoic and Lower Paleozoic of the Sierra de Umango, Andean Foreland (29°S), Argentina: U-Pb ages and isotopic characteristics. | en-US |
| dc.type | info:eu-repo/semantics/article | |
| dc.type | info:eu-repo/semantics/publishedVersion | |
| dc.type | es-ES | |
| dc.type | en-US |
This item appears in the following Collection(s)
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Andean Geology
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