Repositorio Digital Sernageomin
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A peculiar specimen of Panochthus (Xenarthra, Glyptodontidae) from the Eastern Cordillera, Bolivia
No full textPanochthus Burmeister is one of the most diversified and widely distributed glyptodonts in the Pleistocene of South America, which includes areas located at high altitudes (>4,000 m a.s.l.). Within the genus, eight species (P. intermedius Lydekker, P. subintermedius Castellanos, P. tuberculatus (Owen), P. frenzelianus Ameghino, P. greslebini Castellanos, P. jaguaribensis Moreira, P. hipsilis Zurita, Zamorano, Scillato-Yané, Fidel, Iriondo and Gillette, and P. florensis Brambilla, López and Parent) are currently recognized. Here, we report a dorsal carapace (UATF-V n/n) from the Pleistocene of the surroundings of Potosí, Bolivia, that shows some morphological particularities when compared to the carapace of P. intermedius, P. frenzelianus, P. subintermedius and P. tuberculatus, including: a) its maximum dorso-ventral diameter is at the anterior half, meanwhile in other species is at mid-point (e.g., Propalaehoplophorus) or at posterior half (e.g., Glyptodon); b) the dorsal profile is different in comparison to other glyptodonts (e.g., Glyptodon, Glyptotherium, Neosclerocalyptus, Propalaehoplophorus); c) the ornamentation pattern of the osteoderms shows a central figure surrounded by small polygonal figures along the most exposed surface of the carapace (except for the mid-dorsal region that shows reticular ornamentation pattern), being different from that of the remaining species: of Panochthus, in which central figures are limited to the caudal/cephalic and most lateral regions of the carapace. In summary, the combination of characters suggests that it could belong to a new species or, alternatively, to P. floriensis or P. jaguaribensis in which the dorsal carapace is not yet known. The phylogenetic analysis confirms its basal position among Panochthus and highlights the importance of these high elevation areas of the Andes in South America in order to understand the complex evolutionary history of glyptodonts.pp.57-7
Diagenesis of continental carbonates linked to the evolution of the flexural margin of the Triassic Sorocayense-Hilario rift sub-basin, Argentina
No full textThe lithostratigraphic units that conform the Sorocayense Group and fill the Sorocayense-Hilario sub-basin represent an alluvial-fluvial-lacustrine succession with significant volcanic supply during its deposition. They are namely the Cerro Colorado del Cementerio, Agua de los Pajaritos, Monina, Hilario and El Alcázar formations and present several carbonate levels. The genesis, diagenesis, and main controlling factors on continental carbonates present a means to understand basin evolution through the study of their petrography and chemical elemental composition through cathodoluminescence techniques. We have identified six microfacies: a) homogeneous micrite, b) bioclastic micrite, c) dolomicrite, d) laminated micrite, e) oncolitic packstone, and f) sparitic carbonate. Among these microfacies, six cementation and alteration phases have been identified: a) micritization, b) mechanical compaction, c) calcitic cementation, d) sparitic cementation, e) microsparitic cementation, and f) chemical compaction. This analysis allowed establishing a chronology of the diagenetic modifications undergone by the carbonates. Results support diagenesis was controlled mainly by tectonics showing major impact in carbonate facies identified at the flexural margin of the rift. The effect would have been linked to exertion of a paleohydrological effect favoring lateral meteoric water migration through faulting. The presence of dolomite in some of the microfacies is linked to the presence of montmorillonite as the dominant Mg-rich-phyllosilicate in clay assemblages most likely acting as the potential source. In turn, Mg is more likely to be replaced by Mn leading to luminescent carbonate microfacies.pp.269-29
Visita técnica por remoción en masa en la ruta CH-235, comuna de Palena, región de Los Lagos
No full textInforme Técnico -- Unidad Ejecutora: Oficina Técnica de Coyhaique, Unidades de Peligros Geológicos y Ordenamiento Territorial, Asistencias Técnicas y Emergencias Geológicas15 p
Remociones en masa : ¿Qué características tienen y dónde ocurren en la región de Antofagasta?
No full textCorresponde a anexo de BSNGM 16371 DVD: Zonificación de áreas expuestas a peligros de remoción en masa en la región de Antofagasta ; Xterrae Geologí
Geología del área Pichibelco-Cauquenes, región del Maule
No full textContiene Anexos: Anexo I.Dataciones Radiométricas ; Anexo II.Fósiles ; Anexo III.Análisis Químicos ; Anexo IV.Diagramas de Clasificación Geoquímica ; Anexo V.Depósitos Minerales ; Escala: 1:100.000 ; Coordenadas: 35º30’ y 36º00’ S / 72º00’ y 72º30’ O151 p
Remociones en masa : ¿Qué características tienen y dónde ocurren en la región de Los Ríos?
No full textCorresponde a anexo de BSNGM 16319 DVD: Zonificación de áreas expuestas a peligros de remoción en masa en la región de Los Ríos ; Xterrae Geologí
Zonificación de áreas expuestas a peligros de remoción en masa en la región de Los Ríos
No full textInforme Final ; Estudio FNDR COD. BIP 40016748 - 0 ; Estudio financiado por el Gobierno Regional de Los Ríos y su Consejo Regional ; Mandante: Gobierno Regional de Los Ríos, Chile ; Contraparte técnica: Servicio Nacional de Geología y Minería, Chile ; Empresa ejecutora: Xterrae Geología ([email protected]); 4 mapas escala 1:250.000 y 4 mapas escala 1:100.000 ; ANEXOS: - ANEXO A: GLOSARIO - ANEXO B: MAPAS TEMÁTICOS - ANEXO C: CATASTRO DE REMOCIONES EN MASA - ANEXO D: ANTECEDENTES BIBLIOGRÁFICOS - ANEXO E: SUSCEPTIBILIDAD - ANEXO F: TRABAJO DE CAMPO - ANEXO G: FICHAS DE ESTUDIOS ESTÁNDAR REQUERIDOS - ANEXO H: FACTORES DESENCADENANTES - ANEXO I: PRODUCTOS TRANSFERENCIA DE CONOCIMIENTO; Respaldo en DVD306 p
Visita técnica por condición de estabilidad de laderas en cerro La Virgen y caleta Punta Lavapie, comuna de Arauco, región del Biobío
Get PDFRevisor: Carolina Jara. -- Informe Técnico -- Unidad Ejecutora: Dirección Regional de Los Ríos, Valdivia15 p
Geoquímica y mineralogía de sedimentos fluviales de la cuenca del río Limarí, región de Coquimbo, Chile
No full textInforme Registrado IR-23-106122 p
Geology, hydrothermal alteration and mineralogy of the Sofía-Julia-Valencia Veins, Andacollo, Neuquén, Argentina
Get PDFThe 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