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Mineralization, structural control, and 3D modelling of ore shoots in Julieta vein, Casposo district (Cordillera Frontal, San Juan, Argentina)
No full textThe Casposo District is located in the Cordillera Frontal, in the center-west of San Juan Province, Argentina. It is characterized by the presence of a low sulfidation epithermal system hosted in volcanic rocks of the Choiyoi Group, where the Mercado-Kamila and Julieta are the more important sectors, concentrating the largest resources of the district. Julieta consists of a quartz-calcite (Au-Ag) vein system, with colloform-banded and brecciated textures, as well as lattice-bladed replacements. In this study, a detailed analysis of the mineralogy and textures of the Julieta Vein system identifies 9 pulses grouped into 4 main events, 3 hydrothermal and 1 tectonic-hydrothermal. Pulses P1, P2 and P3 are barren and carbonated in nature. Pulses P4 and P5A are of chalcedony composition with a colloform-banded texture, where the last one shows cream-colored adularia bands and black ginguro bands, to which high Au (5,5 g/t) and Ag (52 g/t) values are associated. Pulse P5B is of silicic nature as well, although with a brecciated texture, whereas pulse P6 is siliceous carbonate. The composition of these pulses migrates to carbonates represented by P7 and P8, both of brecciated texture. Finally, the system closes with the tectonic-hydrothermal pulse P9. Julieta Vein has a dominant NW-SE strike, with minor subveins of E-W and N-S orientation, that can be divided into 3 segments: North, Central and South. The greater thicknesses, as well as the greater inclinations and high precious metals values are associated with inflections between the 3 segments. Concerning the ore shoots geometry, the structure has a main lithologically controlled subhorizontal ore shoot, while the secondary subvertical ore shoots are structurally controlled. Differences in the rheology of the host rock would control the vein morphology, forming a vertical jog. Factors such as the evolution of the mineralizing events, the vein morphology, and the precious metals distribution, allowed us to identify the importance of the lithological and structural controls in the development of mineralization in the Julieta Vein.pp.387-40
Mineralization, structural control, and 3D modelling of ore shoots in Julieta vein, Casposo district (Cordillera Frontal, San Juan, Argentina)
No full textThe Casposo District is located in the Cordillera Frontal, in the center-west of San Juan Province, Argentina. It is characterized by the presence of a low sulfidation epithermal system hosted in volcanic rocks of the Choiyoi Group, where the Mercado-Kamila and Julieta are the more important sectors, concentrating the largest resources of the district. Julieta consists of a quartz-calcite (Au-Ag) vein system, with colloform-banded and brecciated textures, as well as lattice-bladed replacements. In this study, a detailed analysis of the mineralogy and textures of the Julieta Vein system identifies 9 pulses grouped into 4 main events, 3 hydrothermal and 1 tectonic-hydrothermal. Pulses P1, P2 and P3 are barren and carbonated in nature. Pulses P4 and P5A are of chalcedony composition with a colloform-banded texture, where the last one shows cream-colored adularia bands and black ginguro bands, to which high Au (5,5 g/t) and Ag (52 g/t) values are associated. Pulse P5B is of silicic nature as well, although with a brecciated texture, whereas pulse P6 is siliceous carbonate. The composition of these pulses migrates to carbonates represented by P7 and P8, both of brecciated texture. Finally, the system closes with the tectonic-hydrothermal pulse P9. Julieta Vein has a dominant NW-SE strike, with minor subveins of E-W and N-S orientation, that can be divided into 3 segments: North, Central and South. The greater thicknesses, as well as the greater inclinations and high precious metals values are associated with inflections between the 3 segments. Concerning the ore shoots geometry, the structure has a main lithologically controlled subhorizontal ore shoot, while the secondary subvertical ore shoots are structurally controlled. Differences in the rheology of the host rock would control the vein morphology, forming a vertical jog. Factors such as the evolution of the mineralizing events, the vein morphology, and the precious metals distribution, allowed us to identify the importance of the lithological and structural controls in the development of mineralization in the Julieta Vein.pp.387-40
Remociones en masa desencadenadas por el evento meteorológico del 20 al 22 de agosto de 2023. Región del Maule
Get PDFInforme Técnico -- Unidades Ejecutoras: Unidad de Asistencias Técnicas y Emergencias Geológicas. Unidad de Peligros Geológicos y Ordenamiento Territorial. Unidad de Geología Regional66 p
Nematherium (Xenarthra, Folivora) from the Serravallian of La Venta, Department of Huila, Colombia; chronological and biogeographical implications
Get PDFThe restudy of a sloth specimen from the Honda Group (La Venta, Department of Huila, Colombia), more precisely from the upper levels of the La Victoria Formation and the lower levels of the Villavieja Formation (Serravallian, middle Miocene), suggests its assignment to Nematherium sp. (Mammalia, Folivora). This is the first record of Nematherium for Colombia, and given that until now the genus had been recorded from the Burdigalian (early Miocene) of southern South America, the record presented herein extends its geographic and chronological distribution.pp.436-44
Respuesta sísmica del área de Melipilla-Pomaire, región Metropolitana de Santiago
No full textInforme Registrado IR-23-105202 p
Evaluación geológica de puntos de encuentro transitorio en la comuna de Putre, Región de Arica y Parinacota, en caso de erupción del complejo volcánico Taapaca
No full textInforme Técnico -- Unidad Ejecutora: Unidad de Geología y Peligros de Sistemas Volcánicos, Santiago46 p
Análisis de remociones en masa y activación de quebradas durante evento hidrometeorológico del 21 al 24 de junio en la comuna de San José de Maipo, región Metropolitana de Santiago
No full textInforme Técnico -- Unidad Ejecutora: Unidad de Peligros Geológicos y Ordenamiento Territorial, Santiago76 p
The April 2015 Calbuco eruption pyroclastic density currents : Deposition, impacts on woody vegetation, and cooling on the northern flank of the cone
No full textThe 22-23 April 2015 eruption of the Calbuco volcano (Southern Andes, Chile) led to extensive pyroclastic density currents (PDCs) interactions with vegetation. We seek to describe the PDCs which affected both Tepu and Frío rivers, northern Calbuco, from their timing and deposition to cooling and erosion, as well as their impacts on forests. Our investigation is based on field stratigraphy, forest disturbance assessment, and geothermometry from degassing pipes and charcoal. These PDCs reached at least ~540-603 °C, as estimated from fumaroles, and consisted of both concentrated and dilute PDCs during the first pulse (22 April) at Tepu and mainly during the second pulse (23 April) at Frío. Effects of PDCs on forest vegetation recorded in Tepu consisted of heating, abrasion, burial, and impact force. On the valley floor, trees were buried with up to 4 m of deposits from the concentrated PDCs, and all trees in this deposition zone died with no subsequent sprouting. Conversely, in the margins of the valley, defoliated fallen trees and standing shrubs indicate scorching due to the passage of dilute PDCs, and some of them were later sprouting. Estimated impact forces required to produce toppling range from 1.5 to 3.7 kPa, and PDC velocities reached up to 36 m s-1. Charring of the buried wood involved an emplacement temperature of 400-550 °C within PDC deposits. The rapid watershed formation may have facilitated infiltration, decreasing the temperature in the basal part within the deposits at the Tepu river. Runoff during the subsequent months triggered lahars and caused the rivers to incise the deposits and transport sediment downstream. This set of observations provides valuable insights into how the interaction between volcanic phenomena and margine forest on the valley floors informs eruptive processes, dynamics, and impacts. Our study is also relevant to interpret the thermal history and potential hazards of PDCs.pp.319-34
Evaluación de remociones en masa en parque Glaciar Mosco, cerros Submarino y Santiago, comuna de O’Higgins, región de Aysén del General Carlos Ibáñez del Campo
No full textInforme Técnico -- Unidades Ejecutoras: Oficina Técnica de Coyhaique, Unidad de Asistencias Técnicas y Emergencias Geológicas18 p
Caracterización de sectores con erosión en la ribera del Lago Chapo, comuna de Puerto Montt, región de Los Lagos
No full textInforme Técnico -- Unidad Ejecutora: Oficina Técnica Puerto Varas27 p