Interaccion entre la Granodiorita Pinchal y el Xenolito kilometrico de Cerro Negro, Sierra de Moreno, Region de Antofagasta, Chile.
Interaction between the Pinchal Granodiorite and the Kilometric Xenolite of Cerro Negro, Sierra de Moreno, Antofagasta Region, Chile.
| dc.contributor | en-US | |
| dc.contributor | es-ES | |
| dc.creator | Niemeyer, Hans | |
| dc.creator | Nava, Marcelo | |
| dc.creator | Soto, Ivan | |
| dc.date | 2010-06-30 | |
| dc.identifier | http://www.andeangeology.cl/index.php/revista1/article/view/V33n1-a01 | |
| dc.identifier | 10.5027/andgeoV33n1-a01 | |
| dc.description | Se estudian los procesos asociados a la interaccion entre la Granodiorita Pinchal (GP) y el Xenolito kilometrico de Cerro Negro (XKCN). La GP se enfrio durante el Carbonifero Superior en tanto que la edad del XKCN no se conoce hasta el momento. El XKCN se presenta en la cupula de la GP. Esta formado por una secuencia estratificada de rocas corneas de 600 m de areniscas, pelitas y conglomerados corneos. Al microscopio, las areniscas se caracterizan por el desarrollo de una matriz de fabrica granoblastica con minerales recristalizados de, plagioclasa, cuarzo, biotita, actinolita, hornblenda y granate. Estos minerales constituyen asociaciones mineralogicas generadas comprendidas dentro del rango de temperatura de 320 a 550°C. La GP es de composicion predominantemente granodioritica y, en menor proporcion, monzogranitica. En el flanco occidental del XKCN, la GP presenta facies porfirica, en tanto que en su contacto oriental este pluton exhibe facies faneritica equigranular. En el borde occidental, el contacto del XKCN con la GP corresponde a una zona de cizalle ductil desarrollada en la facies porfirica de la GP. En el borde oriental, el contacto se caracteriza por asimilacion, presencia de xenolitos de metasedimentitas e inyecciones de material granitico. En el borde oriental del XKCN, el contacto se caracteriza por asimilacion, presencia de xenolitos de metasedimentitas e inyecciones de material granitico. Este ultimo se caracteriza por presentar estructuras megascopicas tales como plegamiento sinclinal y deflexion de capas en su parte septentrional, que se asocian a la caida gravitacional del XKCN en el magma de la GP por el mecanismo de 'stoping'. En cambio, la actitud homoclinal del XKCN en su parte meridional, con aumento de manteo de las capas entre el borde occidental y el borde oriental, se interpreta como debido a la extension, relacionada con el basculamiento hacia el sureste durante su caida. La foliacion y lineaciones metamorficas dentro del XKCN representan fabricas penetrativas ductiles originadas durante esta deformacion. Ademas, en el XKCN se observan venas ptigmaticas, pliegues y 'boudinage'. Tambien afloran estructuras de caracter fragil-ductil como grietas de tension. Sobre la base del analisis de 'strain' en conglomerados deformados se establecio una deformacion coaxial con desarrollo de un elipsoide de 'strain' prolado. Se trata de tectonitas LS. Se reconstruye la historia del proceso de 'stoping' del XKCN, desde su desprendimiento de la roca de caja, metamorfismo, deformacion y, finalmente, hundimiento y detencion dentro de la masa del pluton. Con el caso de estudio abordado en el presente trabajo se demuestra que el 'stoping' magmatico puede darse en gran escala en la cupula de un pluton. | es-ES |
| dc.description | The processes associated with the interaction between the Pinchal Granodiorite (PG) and the kilometric Cerro Negro Xenolith (KCNX) are studied. The PG was cooled during the Late Carboniferous, whereas the age of the KCNX remain until now unknown. The KCNX is immersed in the top of the PG. It is formed by a 600 m thick stratified succession of hornfels including sandstones, pelites and conglomerates. The sandstones are observed in the hornfels showing granoblastic fabric with recrystallized plagioclase, quartz, biotite, actinolite, hornblende and garnet. These minerals were formed at temperatures comprised between 320 and 550°C. The PG is mainly granodioritic and, in minor proportion, monzdioritic. In the western flank of the KCNX a porphyritic facies is present in the PG, whereas in its eastern contact the pluton mainly exhibits equigranular facies. In the western edge, the contact of the KCNX with the PG corresponds to a ductile shear zone. In the eastern edge, the contact is characterized by assimilation, presence of metasedimentary small xenoliths and injections of granitic material. In the latter, magmatic foliation and oblate enclaves are observed, whose deformation is related with the flow associated to the descendent movement of the KCNX. The KCNX display megascopic structures such as synclinal folding and deflection of layers in its northern part, which are interpreted as due to the gravitational fall of the KCNX in the magma of the PG by a stoping mechanism. The homoclinal attitude of the KCNX in its southern part, with increase of the dip of the layers between the western edge and the eastern edge, is interpreted as stretching that accompanied the tilting towards the southeast during its fall. Foliation and lineations within the KCNX represent ductile penetrative fabrics during this deformation. In addition ptigmatic veins, centimetric folds and boudinage are observed. Also structures of fragile-ductile character as tension gashes are present. On the basis of the analysis of strain in deformed conglomerates a coaxial deformation with a prolate ellipsoid developed. Tectonites are classified as LS. The history of the process of stoping of the KCNX is reconstructed, which started with its loosening of the country rock, metamorphism, deformation and, finally, collapse and halting within the mass of the PG. The present work demonstrates that magmatic stoping can occur on a great scale in the upper part of a pluton. | 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/V33n1-a01/741 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V33n1-a01/html | |
| dc.source | Andean Geology; Vol 33, No 1 (2006); 3-18 | es-ES |
| dc.source | Andean Geology; Vol 33, No 1 (2006); 3-18 | en-US |
| dc.source | 0718-7106 | |
| dc.source | 0718-7092 | |
| dc.title | Interaccion entre la Granodiorita Pinchal y el Xenolito kilometrico de Cerro Negro, Sierra de Moreno, Region de Antofagasta, Chile. | es-ES |
| dc.title | Interaction between the Pinchal Granodiorite and the Kilometric Xenolite of Cerro Negro, Sierra de Moreno, Antofagasta Region, Chile. | en-US |
| dc.type | info:eu-repo/semantics/article | |
| dc.type | info:eu-repo/semantics/publishedVersion | |
| dc.type | es-ES | |
| dc.type | en-US |
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Andean Geology
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