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Remociones en masa : ¿Qué son y por qué 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
Evaluación de remociones en masa en Población General Bernales, comuna de Coyhaique, región de Aysén del General Carlos Ibáñez del Campo
No full textInforme Técnico -- Unidad Ejecutora: Oficina Técnica de Coyhaique, Coyhaique14 p
Garnet composition from the Reflejos de Mar LCT-pegmatite, Ancasti district, Argentina and its implication for exploration of primary deposits of lithium
No full textThe Reflejos de Mar Li-pegmatite, located in northwestern Argentina, is part of the Villismán pegmatite group, Ancasti District, Pampean Pegmatite Province. Four garnet crystals from the outermost part of the pegmatite were analyzed by major and minor elements (SiO2, TiO2, Al2O3, Cr2O3, MgO, CaO, MnO, FeO) using electron microprobe. The pegmatite belongs to the rare-element class, spodumene type, LCT (Li-Cs-Ta) petrogenetic family. Based on their Mn and Fe contents, the analyzed garnet can be assigned to the spessartine-almandine serie. The cores and rims of the analyzed garnets show significant differences for the divalent components in VIII-coordination, especially, Mn and Fe. The average MnO and FeO contents in the cores of the grains is 34.6 and 8.29 wt%, respectively, while in the rims is 29.31 and 12.95 wt%, respectively. The Fe/Mn ratio at the core of the grains is 0.24 while at the rims it is 0.44. Cr2O3 and TiO2 contents are very low (˂0.17 wt%) and the values of SiO2 and Al2O3 are ~36 and ~21 wt%, respectively. The mean chemical and molecular formulas of the core can be expressed: [(Mn2.40 Fe0.57 Ca0.02 Mg0.02)3.01 (Al1.99 Cr0.002)2.00 (Si2.99 Ti0.01)3.00 O12]; {Sps79.8 Alm18.9 Grs0.7 Prp0.5}; and the rim as: [(Mn2.04 Fe0.89 Ca0.05 Mg0.04)3.02 (Al2.00 Cr0.002)2.00 (Si2.98 Ti0.005)3.00 O12]; {Sps67.6 Alm29.5 Grs1.6 Prp1.3}. The chemical composition of garnet from the Reflejos de Mar pegmatite is similar to other worldwide examples in similar rocks, especially LCT pegmatites, which are highly evolved and associated with Li mineralization. Therefore, its composition could be used as an additional tool in the exploration of Li-bearing pegmatites in the Pampean Pegmatite Province. The differences in Fe-Mn contents between core and rim of the crystals would be controlled by variations in composition of the pegmatitic melt and, in addition, by the simultaneous precipitation of other mineral phases, for example, schorl and Mn-Fe-bearing phosphates.pp.150-16
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
Evaluación de remociones en masa en laguna periglacial Huemules y alrededores, comuna de Tortel, región de Aysén del General Carlos Ibáñez del Campo
No full textInforme Técnico -- Unidad Ejecutora: Oficina Técnica de Coyhaique, Unidad de Asistencias Técnicas y Emergencias Geológicas15 p
Evaluación de remociones en masa en laguna periglacial Huemules y alrededores, comuna de Tortel, región de Aysén del General Carlos Ibáñez del Campo
Get PDFInforme Técnico -- Unidad Ejecutora: Oficina Técnica de Coyhaique, Unidad de Asistencias Técnicas y Emergencias Geológicas15 p
Taphonomic analysis of Spinicaudata from two Triassic lacustrine systems affected by different volcanic processes
Get PDFSpinicaudata are freshwater branchiopods. The growth and development of spinicaudata populations in freshwater environments depend on various physical, chemical, and biological factors. The action of volcanism modifies the limnological parameters in the process of fossilization of lacustrine deposits. This study identifies spinicaudatan assemblages in two Triassic lake systems in Argentina, and analyzes the dynamics of shell preservation according to the volcanic activity involved. Two taphonomic grades divided into three different second taphonomic grades were defined. The focus on taphonomic and chemistry studies addresses changes in spinicaudata abundance and richness through time, in different paleoenvironmental conditions, and shell preservation and chemical composition. The discussion highlights the importance of lava flow inflow and volcanic ash fall in the different lake systems. We emphasize the importance of taphonomic studies on the spinicaudata groups to understand their autochthonous and allochthonous populations in Triassic lake systems. In turn, we conclude that the post mortem processes experienced by the shells, the exposure time at the water-sediment interface, and the chemical alteration of the water into the paleolakes produced by the surrounding volcanic activity can explain the development and preservation of spinicaudata in these two Triassic lacustrine systems.pp.403-43
Zonificación de áreas expuestas a peligros de remoción en masa en la región de Antofagasta
No full textInforme Final ; Estudio FNDR COD. BIP 40018140-0 ; Apoyo financiero: Fondo Nacional de Desarrollo Regional FNDR Código BIP 40018140-0, Gobierno Regional de Antofagasta, Chile. Fondos sectoriales del Servicio Nacional de Geología y Minería, Chile ; Institución Mandante: Gobierno Regional de Antofagasta, Chile ; Contraparte técnica: Servicio Nacional de Geología y Minería, Chile ; Empresa ejecutora: Xterrae Geología ([email protected]) ; 4 mapas escala 1:250.000 ; ANEXOS: - ANEXO A: GLOSARIO - ANEXO B: ANTECEDENTES BIBLIOGRÁFICOS - ANEXO C: CATASTRO - ANEXO D: MAPAS TEMÁTICOS - ANEXO E: SUSCEPTIBILIDAD - ANEXO F: FACTORES DESENCADENANTES - ANEXO G: TRABAJO DE CAMPO - ANEXO H: PRODUCTOS TRANSFERENCIA DE CONOCIMIENTO - ANEXO Complementario A: CATASTRO DE REMOCIONES EN MASA - ANEXO Complementario B: ACTAS DE REUNIONES Y TALLERES - ANEXO Complementario C: CARTILLLAS DE MAPEO EN TERRENO ; Respaldo en DVD121 p
Long-term irrigation as an earthflow trigger in Chenque Malal, Northern Patagonia, Argentina
No full textBecause of their social, ecological, and economic impacts, landslides are an issue of global concern. Episodes occurring worldwide have been associated with natural and human causes, although the latter have been poorly explored. Despite recent scientific insight into intensive irrigation as a cause, research remains scarce. This paper focuses on determining the anthropogenic influence on the triggering of earth flows by long-term intensive irrigation, based on temporal and geospatial information. This analysis covers a sector of Northern Patagonia in Argentina, an area of transhumant pastoralism. Our results show that excessive water input creates favorable conditions for the triggering and evolution of earth flows in the region, even under water deficit conditions. As a result, on 22 September 2020, a collapse was recorded which mobilized ~19,000 m³ of earth debris along 360 m and produced economic losses estimated at 168,000 USD. Other landslides are expected to occur in the area if irrigation amounts remain at the same level.pp.372-38
Compositional and geothermobarometric analysis of the Upper Miocene tholeiitic volcanic products in the northern Andes at 5-6° N latitude : The Combia Volcanic Province
Get PDFThe Combia Volcanic Province (~11-5 Ma), is a volcaniclastic sequence located in northwest Colombia between the Central and Western cordilleras at 5-6° N latitude. Its source is associated with the volcanic activity of the magmatic arc produced by the subduction of the Nazca plate under the South American plate in the northern Andes. The distribution, composition, and chronostratigraphy of the province’s deposits are well-known, with the volcanic sequences characterized as compositionally bimodal. The older rocks (ca. 11-9 Ma) display tholeiitic affinity, whereas the younger (ca. 9-5 Ma) are mostly calc-alkaline, with some adakite-like signature recognized. While the magmatic system for the calc-alkaline magmas has been previously extensively studied, the processes that occurred during the magma stagnation and ascent are unknown for the tholeiitic magmas. This work bridges this gap by the study of tholeiitic lava flows outcropping at the center of the province, through petrography, mineral chemistry, whole-rock analysis, and geothermobarometry calculations of the crystallization conditions. Texturally, the rocks are porphyritic with plagioclase (An50-90) and clinopyroxene (augite and pigeonite) phenocrysts and microphenocrysts, embedded in a glassy and microcrystalline groundmass. Compositionally, the rocks vary from basaltic andesite to andesite (52.8-57.8 wt% SiO2), with relative enrichments of LILE to HFSE and REE to chondrite. Crystallization conditions, based on several plagioclase-melt and pyroxene-melt geothermobarometers, were estimated at T=1,095-1,153 °C and P=0.22-0.60 GPa for the plagioclase, T=1,046-1,131 °C and P=0.09-0.21 GPa for the augite, and T=867-1,039 °C and P=0.40-0.60 GPa for the pigeonite. These results suggest a relatively rapid magma ascent for the tholeiitic products as well as an evolution mostly through fractional crystallization. The LILE elements enrichment, the negative trend in the FeOt, TiO2 and CaO versus SiO2 content, together with some disequilibrium textures, are also evidence of crustal contamination and magma recharge. Thus it is proposed that the Combia Volcanic Province started as a simple magmatic system, where the tholeiitic products were generated by a relatively rapid magma ascent. Then, a more complex magmatic system linked to long-term magma stagnation, allowed melt evolution to form calc-alkaline magmas as previously defined.pp.181-20