Repositorio Digital Sernageomin
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Characterization and distribution of adularia and other alteration minerals by X-ray diffraction analysis at the El Peñón Au-Ag epithermal deposit, northern Chile
No full textThe El Peñón low-sulfidation epithermal deposit, located in the Paleocene metallogenic belt in the Antofagasta region, northern Chile, consists of Au-Ag bearing veins and hydrothermal breccias hosted in volcanic rocks and surrounded by alteration haloes consisting of a series of minerals, such as adularia, carbonates and clay minerals. They are the result of metasomatism generated by the passage of reduced, and near neutral pH, hydrothermal fluids, that transported gold through structures and its interaction with the host rock. We investigated the spatial distribution of these minerals (mainly adularia) in the Aleste vein and its host rock, located in the northern part of the district, to establish their relationship with the Au-Ag ore and, thus, support the identification of new exploration targets. An X-ray diffraction technique to discriminate adularia from other K-feldspars in whole rock samples was developed by the detail study of the diffractogram patterns of an adularia standard. The study of an X-ray diffraction standard pattern allowed the recognition of this mineral by 4 secondary peaks. Our results indicated that adularia occurs in association with felsic volcanic rocks, and it is restricted in intermediate composition units. The spatial distribution of this mineral is correlated with the mineralized zones, being adularia semi-quantitative abundance in the range of 25 to 40% a good indicator of gold mineralization. Sericite and illite occur mainly where adularia is scarce or absent. The spatial distribution of these minerals showed the structural control in the evolution and flow path of the hydrothermal fluids toward the surface. Kaolinite is related to argillic alteration caused by steam-heated fluids, and the advanced argillic alteration associated with later supergene alteration. Chlorite usually is far from the mineralized areas; therefore, it could be a reliable indicator of the margins of the system. The characterization and spatial distribution pattern of the alteration minerals identified by the X-ray diffraction method in the veins of El Peñón deposit show the capability of this type of analyses in determining possible prospection targets.pp.185-20
Visita técnica a sectores de la comuna de Talcahuano Región del Biobío, afectados por remociones en masa durante Julio del año 2022
No full textRevisores: Mónica Marín y Carolina Jara. ; Informe Técnico27 p
Historical photographs by South African geologist Alexander L. du Toit taken along the Transandine Railway (Argentina-Chile) in 1923
No full textSouth African geologist Alexander du Toit spent three months in 1923 doing reconnaissance mapping in South America, which resulted in his seminal 1927 work “A Geological Comparison of South America and South Africa”. A few photographs taken by du Toit were published, but most were destroyed in a devasting fire in April 2021. Some surviving annotated images, giving locations, of a trip du Toit had made from Argentina to Chile on the Transandine Railway, in 1923, are reproduced here. They may help with recognizing landscape changes, such as due to melting glaciers, during the century since the photographs were taken.pp.288-29
Imágenes de anomalías magnéticas del área 35°30´-36°00´S y 72°00´-72°40´O, Región del Maule
Get PDFInforme Técnico -- Unidad Ejecutora: Unidad de Geofísica del Departamento de Geología General. Santiago14 p
Modelación 2D de anomalías gravimétricas en localidades de Pomaire, Santa Elvira y Melipilla, Región Metropolitana
Get PDFInforme Técnico -- Unidad Ejecutora: Unidad de Geofísica del Departamento de Geología General. Santiago23 p
Geoquímica y mineralogía de sedimentos fluviales de la cuenca del río Valdivia, regiones de La Araucanía y de Los Ríos, Chile
No full textInforme Registrado IR-22-10287 p
Evaluación de remociones en masa en Laguna Sin Nombre en Valle Exploradores, comuna Río Ibáñez, región de Aysén del General Carlos Ibáñez del Campo
No full textRevisor: Carolina Jara I. ; Informe Técnico10 p
Profesor Alfredo Lahsen Azar (1939-2022) Pionero de la energía geotérmica en Chile
No full textpp.463-46
Remotely sensed time series of rapid terrace formation : Laguna del Viedma valley (Patagonia)
Get PDFThe Patagonian Andes were affected by a range of geophysical drivers of landscape incision during the Last Glacial Interglacial Transition and Early Holocene. Deciphering drivers of river system response during this period is complex, and magnitudes and timescales of landscape change are poorly constrained. Herein, a remotely sensed time series of modern terrace formation is investigated from the Laguna del Viedma valley as a modern analogue of Late Quaternary landscape evolution in Patagonia. The aim of the research was to constrain the timing of terrace formation following lake level fall of the Laguna del Viedma over a 35 year period from 1985-2019. The objectives were to: 1) use satellite imagery from 1985-2019 to document glacier and lake changes in the study area; 2) map landforms of the Laguna del Viedma valley; and 3) analyse terrace elevations. In total seven terrace surfaces were distinguished, with the oldest four pre-dating the ALOS PALSAR DEM (February 2000) used. Landform evidence shows the highest, and vegetated, T1 terrace surface (+40-75 m) grades to the highest lake level and was likely the elevation of the valley floor during Holocene neoglacials. Viedma glacier recession then led to a phase of lake regressions/transgressions with an overall trend of lake level fall. The DEM shows ~20 m incision from the 1985 floodplain level (T3) to the T4 level floodplain by 2000. This constrains a minimum rate of incision of 1.33 m/yr, however, the satellite time series demonstrates rapid T3 terrace formation, with evidence for mass movements contributing to lateral terrace erosion by 1986. The implications of the data are discussed within the context of the Late Quaternary palaeohydrology of Patagonia where lake level falls of 10s to 100s of metres occurred within many large river systems of the Patagonian Andes from 42-52⁰ S. The data herein demonstrate that base level falls from sudden lake drainage events were likely a major driver of rapid landscape change in Patagonia during deglaciation.pp.169-18
