Lavas con bitumen en el Cretacico Inferior de Copiapo,Region de Atacama, Chile: petroquimica e importancia metalogenica.
Bitumen-rich lavas in the Lower Cretaceous of Copiapó, Atacama Region, Chile: petrochemistry and metallogenesis significance.
| dc.contributor | en-US | |
| dc.contributor | es-ES | |
| dc.creator | Cisternas, Maria Eugenia | |
| dc.creator | Frutos, Jose | |
| dc.creator | Galindo, Eduardo | |
| dc.creator | Spiro, Baruch | |
| dc.date | 2010-07-05 | |
| dc.identifier | http://www.andeangeology.cl/index.php/revista1/article/view/V26n2-a05 | |
| dc.identifier | 10.5027/andgeoV26n2-a05 | |
| dc.description | El nivel de andesitas cretacicas (70 m de espesor promedio), emplazado en la parte alta (Formacion Pabellon) del Grupo Chanarcillo en la Region de Atacama, ha sido considerado por mas de 30 anos como un filon-manto. Las principales evidencias, que confirman que se trata de una sucesion de coladas de lava derramadas sobre un fondo marino somero, son: la perfecta concordancia con las calizas supra e infrayacientes a lo largo de decenas de km, la presencia de autobrechas y tobas entre flujos lavicos sucesivos, la ocurrencia de endofosiles en posicion de vida en lentes calcareos que engranan lateralmente con las lavas o se intercalan entre flujos sucesivos y el reconocimiento de, al menos, un centro de emision (Quebrada Cerrillos), donde las lavas alcanzan 300 m de potencia. Petrograficamente, las lavas son andesitas porfiricas (ocoitas), derivadas de magmas calcoalcalinos ricos en K, con una impronta geoquimica de intraplaca mas que de subduccion, las cuales fueron eruptadas a traves de una corteza continental delgada en el sector de trasarco del sistema arco-cuenca del Cretacico Inferior. La presencia de migrabitumen hidrotermal, en globulos, ocupando vesiculas primarias o en venillas, es un rasgo caracteristico de estas lavas, y su ocurrencia coincide con mineralizacion metalica, principalmente sulfuros de Cu. Los resultados de geoquimica organica demuestran que el bitumen se origino de materia organica marina, emplazandose en las lavas antes que las soluciones mineralizantes que dieron origen a los sulfuros de Cu. La asociacion bitumen-sulfuros de Cu, particularmente notable en la region de Copiapo, donde demarca un metalotecto regional, se ha observado, tambien, otros yacimientos a lo largo de la franja de lavas ocoiticas del Cretacico Inferior entre Copiapo e Illapel, sugiriendo asi que dicha asociacion tiene un control ligado a la evolucion global de la cuenca de trasarco. | es-ES |
| dc.description | The bitumen-rich andesitic horizon emplaced in the upper part (Pabellón Formation) of the Lower Cretaceous marine sequences in the Atacama Region (Chañarcillo Group) has been formerly considered a sill. The main evidence for interpreting this horizon as submarine lava flows includes: perfect concordance with both the overlying and underlying marine limestones along kilometers, the presence of autobreccias, tuffs and thin chert beds between the flows, the presence of endofossils in undisturbed positions within calcareous lenses that grade laterally to lavas or between successive beds, and the recognition of, at least, one emission center in Quebrada Cerrillos where the lavas reach 300 meters thick. Petrographically, the lavas are porphyritic andesites, derived from K-rich calc-alkaline magmas. Trace and minor element geochemistry point to an intraplate more than to a subduction related origin. These lavas are associated with a back-arc environment and were emplaced in a relatively thin continental crust during the Early Cretaceous. The presence of hydrothermal bitumen is a distinct feature of this horizon in many localities between Copiapó and Illapel. The bitumen occurs as the infilling of vesicles or veins, and is directly associated with metallic mineralisation, copper sulphides essentially. Organic geochemical results demonstrate that the bitumen originated from marine organic matter, migrating and being emplaced before the Cu-rich hydrothermal fluids. This association between bitumen and copper sulphides has become a regional metallotect in the Copiapó region. The same association has been found in numerous deposits along the Lower Cretaceous porphyritic lavas between Copiapó and Illapel, suggesting that this is a regional control associated to the evolution of the back-arc basin. | 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/V26n2-a05/931 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V26n2-a05/html | |
| dc.source | Andean Geology; Vol 26, No 2 (1999); 205-226 | es-ES |
| dc.source | Andean Geology; Vol 26, No 2 (1999); 205-226 | en-US |
| dc.source | 0718-7106 | |
| dc.source | 0718-7092 | |
| dc.title | Lavas con bitumen en el Cretacico Inferior de Copiapo,Region de Atacama, Chile: petroquimica e importancia metalogenica. | es-ES |
| dc.title | Bitumen-rich lavas in the Lower Cretaceous of Copiapó, Atacama Region, Chile: petrochemistry and metallogenesis significance. | 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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