Repositorio Digital Sernageomin
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Visita técnica a Ruta Internacional CH-60 tras precipitaciones del 22 al 24 de junio, Comuna de Los Andes, Región de Valparaíso
No full textInforme Técnico -- Unidad Ejecutora: Unidad de Asistencias Técnicas y Emergencias Geológicas, Santiago24 p
Geology, hydrothermal alteration and mineralogy of the Sofía-Julia-Valencia Veins, Andacollo, Neuquén, Argentina
No full textThe Sofía-Julia-Valencia vein system, located in the Andacollo mining district in central west Argentina, is hosted by ENE-WSW oriented strike-slip faults which are the result of reactivation of normal faults affecting Carboniferous to Jurassic rocks during Upper Cretaceous-Paleogene. These veins contain a total resource of 22,900 Oz of gold with 5.5-6.7 g/t AuEq. Geologic mapping and a U-Pb age of 71±1Ma in zircon, obtained in an altered and mineralized dacitic dyke of the district, allowed to associate the mineralizing event to the Naunauco Andesitic belt magmatism (Upper Cretaceous-Paleogene) and to the Cretaceous-Paleogene Metallogenic Belt of the Andes in southwestern Argentina. The ore bodies are made up of multiple veins and veinlets that, from oldest to youngest, correspond to: (1) scarce early quartz+pyrite+molybdenite+iron poor-sphalerite veinlets, (2) quartz+epidote+calcite±albite (apatite+rutile+titanite+light rare earth elements bearing phosphates) associated with quartz+biotite, epidote (actinolite)+chlorite+calcite, with pyrite+pyrrhotite±chalcopyrite±(iron rich-sphalerite), marcasite veins. These veins are cut and reopened by (3) polymetallic veins and veinlets formed by quartz+sericite±carbonates (chlorite), with iron-gold rich sphalerite+silver rich-galena+chalcopyrite+pyrite, native gold±arsenopyrite±(pyrrhotite, bornite, argentite). Pyrite (4) and (5) carbonate+framboidal pyrite veinlets cuts all the previous ones. Multistage carbonate generation brecciate and cut previous veins and veinlets. Quartz shows granular, comb textures and some calcites developed platy textures. Four hydrothermal alteration types affected the veins host rock: (1) patches of early potassic alteration; (2) widespread propylitic alteration with disseminated sulfides; (3) later phyllic alteration overlapped to the previous ones; and (4) late supergene alteration. The sphalerite and chlorite composition in the veins (1 and 2) along with their mineral assamblages indicates they were formed by initially alkaline fluids (e.g., feldspar stable) with intermediate sulfur and oxygen fugacity and mesothermal temperature conditions (~400-240 °C), that evolved to conditions of lower sulfur (e.g., pyrrhotite stable) and oxygen fugacity, temperature <150 °C, with slightly acidic pH (<5). Fluid inclusions hosted in quartz, calcite and sphalerite from polymetallic veins and veinlets (3) in the western sector of ore deposit show they emplaced at ~1,400 m depths and originated by two discrete pulse of hydrothermal fluids: an early one with highest temperatures (390 to 260 °C) and salinities (4-11% NaCl eq.) and a later one of lower temperature (<220 °C) and salinity (<8% NaCleq.). During this second dilution and cooling event, took place the main mineralization stage. The overlapping of lower temperature veins/veinlets and hydrothermal alteration mineral assemblages to those of higher temperature observed in the SJV vein system, possibly evidence a telescoping process resulting from uplift and erosion of the Cordillera del Viento during the Upper Cretaceous-Paleogene compressional event.pp.93-12
Mediciones GPR en respuesta a Asistencia Técnica en Salto del Laja, Región del Biobío
No full textInforme Técnico -- Unidad Ejecutora: Unidad de Geofísica del Departamento de Geología General. Santiago14 p
Visita técnica por condición de estabilidad de laderas en cerro El Santo y ruta 126, comuna de Tomé, región del Biobío
Get PDFRevisor: Carolina Jara. -- Informe Técnico -- Unidad Ejecutora: Dirección Regional de Los Ríos, Valdivia17 p
On the validity of the Macrochorobates scalabrinii Biozone (early Huayquerian Stage/Age, Late Miocene). Multi-proxy analysis of the enigmatic Arenas Blancas site (Buenos Aires Province, Argentina)
No full textArenas Blancas is a poorly known fossiliferous site located in the lower reach of the Chasicó creek (Buenos Aires Province, Argentina), with great relevance from a biostratigraphic viewpoint. The Macrochorobates scalabrinii Biozone was defined in this site, proposed as the biostratigraphic basis of the early Huayquerian Stage/Age (Late Miocene); however, the geological context and faunal record of this site have never been studied in detail. In this work, we perform a multi-proxy analysis of the Arenas Blancas site, as well as a nearby site here called Curva de la Vaca, and provide new interpretations on their origin, age, and biostratigraphy. Sedimentological, stratigraphic, and geomorphological characteristics of both sites suggest that the sequences include fluvial/alluvial deposits that represent Quaternary terraces. The taxonomic analysis of the Arenas Blancas faunal assemblage evidences the presence of 14 mammal taxa, together with some fishes, reptiles, and birds; the assemblage is correlated with the assemblage from the Cerro Azul Formation assigned to the Chasicoan Stage/Age (Late Miocene), also recovered from the lower reach of the Chasicó creek. The use of the taxa proposed in previous works to characterize the Macrochorobates scalabrinii Biozone (including this species) is not supported due to their taxonomic status and/or temporal distribution. Taphonomic evaluation indicates that the assemblage is constituted by reworked specimens; in this frame, it is proposed that fluvio/alluvial events, occurred during the Late Pleistocene-Holocene, eroded the Upper Miocene substrate and reworked fossil remains. Based on the present evidence, the Macrochorobates scalabrinii Biozone is here rejected as a valid biostratigraphic unit.pp.22-5
Análisis de susceptibilidad de remoción en masa en ladera de humedal urbano Quebrada Gramado colindante con pasaje Machmar, comuna de Puerto Varas, región de Los Lagos
No full textInforme Técnico -- Unidad Ejecutora: Oficina Técnica Puerto Varas21 p
Remoción en masa del 24 de septiembre de 2023 en ladera Colón 535, comuna de Puerto Varas, región de Los Lagos
No full textInforme Técnico -- Unidad Ejecutora: Oficina Técnica de Puerto Varas10 p
Geología de las áreas Surire-Tignamar y Quilhuiri, regiones de Arica y Parinacota y de Tarapacá
No full textContiene Anexos: Anexo I.Dataciones Radiométricas ; Anexo II.Fósiles ; Anexo III.Análisis Químicos ; Anexo IV.Depósitos Minerales ; Escala: 1:100.000 ; Coordenadas: 18°30’ y 19°00’ S / 69°30’ O230 p
Caracterización de remociones en masa : Ladera Angelmó y calle Ecuador, comuna de Puerto Montt, región de Los Lagos
No full textInforme Técnico -- Unidad Ejecutora: Oficina Técnica de Puerto Varas15 p