Mineral reactions associated with hydrocarbon paleomigration in the Huincul High, Neuquén Basin, Argentina

• Autores: Rainoldi, Ana Laura; Franchini, Marta Beatriz; Beaufort, Daniel; Mozley, Peter; Giusiano, Adolfo Eugenio; Cesaretti, Nora Noemi; Patrier, Patricia; Impiccini, Agnes; Pons, María Josefina
• Año de publicación: 2015
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: MINERAL; REACTIONS; HYDROCARBONS; PALEOMIGRATION
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Bleaching of red beds by the migration of reducing pore fluids is a widespread phenomenon, with most previous work on the topic focused on detailed studies in the southwestern United States, and to a lesser extent Germany. Herein, we report on widespread bleaching of Cretaceous red beds in the Neuquén Basin and the relationship of this bleaching to hydrocarbon migration. In the Cerro Granito area of the Huincul High, Neuquén Basin, the basal deposits of the Neuquén Group (Candeleros and Huincul Formations) are bleached. This alteration was apparently controlled by fluid and host-rock composition as well as by the intensity and span of the fluid-rock interaction. Red, fine-grained sandstones and mudstones of the Candeleros Formation were deposited in fluvial and swamp environments and contain authigenic hematite, Na-rich corrensite, micro- and mesoquartz, calcite, and analcite. Coarse-grained sandstones and mudstones of the Huincul Formation, which overlie the Candeleros Formation, were deposited in a braided fluvial system, under more humid and acidic conditions than the Candeleros Formation. Sandstones are similar in composition and texture to the Candeleros sandstones, except they contain less basic volcanic detritusand lack corrensite. Bleached facies in both formations contain bitumen and clusters of calcite + bitumen concretions, and partially dissolved detrital clasts and most cements, including early Fe-oxides, which resulted in an increase in secondary porosity and bleaching of the red beds. Alteration of the Candeleros Formation is confined to medium- to coarse-grained sandstone in which corrensite is partially dissolved and its interlayer charge is satisfied by Ca instead of Na, as in corrensite from the red sandstones. Extensive dissolution occurred in the Huincul Formation, which favored the precipitation of new authigenic minerals such as smectite, mixed-layer chloritesmectite, and pyrite. Bleaching and associated alteration most likely resulted from interaction of hydrocarbons with the red beds. Hydrocarbon paleomigration in the Cerro Granito area occurred in higherpermeability portions of the Candeleros and Huincul Formations. The seal provided by the Lisandro Formation was breached during uplift driven by Tertiary tectonism, resulting in the exhumation of the Huincul and Candeleros Formations. This study highlights the importance of a variety of alterations, including complex clay mineral paragenesis, contemporaneous with bleaching of the red beds. Such alterations can potentially be used to provide evidence for the passage of chemically reducing fluids associated with hydrocarbons in other regions, including cases where the original red color has been completely removed.
Fil: Rainoldi, Ana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur; Argentina
Fil: Franchini, Marta Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina. Universidad Nacional del Comahue; Argentina
Fil: Beaufort, Daniel. Université de Poitiers; Francia
Fil: Mozley, Peter. Department of Earth and Environmental Science, New Mexico Tech; Estados Unidos
Fil: Giusiano, Adolfo Eugenio. Subsecretaría de Minería e Hidrocarburos; Argentina
Fil: Cesaretti, Nora Noemi. Universidad Nacional del Sur; Argentina
Fil: Patrier, Patricia. Université de Poitiers; Francia
Fil: Impiccini, Agnes. Universidad Nacional del Comahue; Argentina
Fil: Pons, María Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina. Universidad Nacional del Comahue; Argentina