Fabrica Magnetica y Microestructuras a traves de los Andes de Tierra del Fuego, Argentina.
Magnetic fabric and microstructures across the Andes of Tierra del Fuego, Argentina
| dc.contributor | en-US | |
| dc.contributor | es-ES | |
| dc.creator | Esteban, Federico | |
| dc.creator | Tassone, Alejandro | |
| dc.creator | Menichetti, Marco | |
| dc.creator | Rapalini, Augusto E. | |
| dc.creator | Remesal, Marcela B. | |
| dc.creator | Cerredo, Maria Elena | |
| dc.creator | Lippai, Horacio | |
| dc.creator | Vilas, Juan F. | |
| dc.date | 2011-03-22 | |
| dc.identifier | http://www.andeangeology.cl/index.php/revista1/article/view/V38n1-a05 | |
| dc.identifier | 10.5027/andgeoV38n1-a05 | |
| dc.description | Se presentan los resultados de una transecta de Anisotropia de Susceptibilidad Magnetica (ASM) realizada en los Andes Fueguinos, Argentina. Se midieron 240 muestras orientadas provenientes de 27 sitios de muestreo distribuidos entre Paso Garibaldi, al norte y el Canal Beagle al sur. El muestreo se focalizo esencialmente en la Formacion Lemaire del Jurasico Superior, con un unico sitio en la Formacion Yahgan del Cretacico inferior. Las litologias estudiadas incluyen basaltos, andesitas y rocas volcanoclasticas y sedimentarias afectadas por metamorfismo de bajo grado. Las mediciones de fabrica magnetica se complementaron con el estudio microscopico de muestras representativas con el proposito de caracterizar las microestructuras y las asociaciones metamorficas. La fabrica magnetica esta dominada por formas obladas y presenta una gran variacion en el grado de anisotropia (1,04-2). Los mayores valores de anisotropia estan asociados a la presencia de pirrotina secundaria, identificada por medio de ensayos magneticos. La foliacion magnetica muestra muy buena correspondencia con el clivaje medido en campo, confirmando el origen tectonico de la fabrica magnetica. Los modelos de distribucion de los ejes de ASM permitieron distinguir tres dominios geograficos. El dominio septentrional, entre Paso Garibaldi y Valle Carbajal, presenta lineaciones magneticas (k1) de orientacion N-S a NE-SW con buzamiento moderado hacia el S-SW, coincidente con determinaciones previas de lineaciones minerales asociadas con la deformacion andina. Este diseno de fabrica magnetica se vincula a la fase de deformacion principal responsable del desarrollo del clivaje pizarreno y de la faja plegada y corrida Fueguina en el Cretacico Tardio. Un segundo dominio corresponde al Valle Carbajal, caracterizado por foliaciones magneticas E-W, subverticales y lineaciones magneticas E-W (a ESE-WNW) subhorizontales que se interpretan como vinculados a regimenes localizados de transcurrencia. La fabrica magnetica en el tercer dominio, en la zona del Canal Beagle, presenta un caracter mas heterogeneo con foliaciones de orientacion tanto E-W como N-S; la presencia de una poblacion de lineaciones magneticas subhorizontales de rumbo E-W sugiere la existencia de un componente de rumbo significativo. | es-ES |
| dc.description | An anisotropy of magnetic susceptibility (AMS) transect was carried out across the Fuegian Andes, in Argentina, with the aim of studying its tectonic evolution. Two-hundred and forty oriented samples were collected from 27 sites distributed between the Paso Garibaldi to the north and the Canal Beagle to the south. The study was restricted to the Upper Jurassic Lemaire Formation, with a single site located in the Lower Cretaceous Yahgán Formation. Studied rocks comprised basaltic, andesitic, volcaniclastic and sedimentary rocks affected by low-grade metamorphism. AMS measurements were complemented with thin section analyses of representative samples in order to characterize the microstructures and metamorphic assemblages. In general, the magnetic fabric shows dominant oblate shapes and a large variation in the anisotropy degree from 1.04 up to 2. The anomalously high values were observed to be associated to growth of secondary pyrrhotite, which was identified by rock magnetic tests. Magnetic foliation was generally consistent with slaty cleaveage as observed in the field, confirming the tectonic origin of the magnetic fabric. Three geographic domains were distinguished in the study region on the basis of the pattern of the AMS axes distribution. In the northern domain, from Paso Garibaldi to Valle Carbajal, the orientation of the maximum susceptibility axis (k1), or magnetic lineation, is N-S to NE-SW with moderate plunge towards the S-SW and coincides with previous determination of mineral lineations associated with the Andean deformation and very low grade metamorphism. The magnetic fabric pattern can be correlated with the main deformational phase responsible for the development of slaty cleavage (main Andean deformational phase) and the tectonic transport due to progression of the Fuegian fold and thrust belt in the Late Cretaceous. A different character is shown along the Valle Carbajal domain, where subvertical E-W magnetic foliation planes and roughly E-W to ESE-WNW subhorizontal magnetic lineations are more difficult to correlate with the main folding phase and suggest its relation to an E-W, possibly localized, strike-slip regime during the main deformational and metamorphic phase. The magnetic fabrics in the third domain, close to the Canal Beagle, displays a more heterogeneous character with both E-W and N-S striking foliations; in this case a population of subhorizontal E-W magnetic lineation (k1) suggests the existence of a significant component of strike-slip deformation. | 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/V38n1-a05/1257 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V38n1-a05/html | |
| dc.source | Andean Geology; Vol 38, No 1 (2011); 64-81 | en-US |
| dc.source | Andean Geology; Vol 38, No 1 (2011); 64-81 | es-ES |
| dc.source | 0718-7106 | |
| dc.source | 0718-7092 | |
| dc.title | Fabrica Magnetica y Microestructuras a traves de los Andes de Tierra del Fuego, Argentina. | es-ES |
| dc.title | Magnetic fabric and microstructures across the Andes of Tierra del Fuego, Argentina | 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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