Remote sensing can be used as a complementary tool in water quality monitoring of aquatic ecosyst... more Remote sensing can be used as a complementary tool in water quality monitoring of aquatic ecosystems. The aim of this study was to develop models to estimate the spatial distribution of chlorophyll-a concentration (Chl-a) in Los Molinos reservoir using Landsat 7 ETM + and ASTER imagery. Los Molinos reservoir (32 o 49 ‘S, 64 o 32’ W) is a multipurpose system used as the second source of water supply for Cordoba’s city. Physical, chemical and biological parameters were measured in the water body coinciding with the passage of the satellites by the study area. Using different statistical techniques, satellite information was related to field data obtaining algorithms that best explained the distribution of Chl-a. These models were validated and used to construct maps providing spatially rich information on patterns of water quality throughout the reservoir. Both sensors could be used for Chl-a monitoring. ASTER sensor, with higher spatial resolution that ETM+, showed a better relations...
Ponencia presentada en la 34a Sesion Cientifica de la Sociedad Geologica de Espana, celebrada en ... more Ponencia presentada en la 34a Sesion Cientifica de la Sociedad Geologica de Espana, celebrada en la Facultad de Ciencias de la Universidad del Pais Vasco, Campus de Leioa (Bilbao) el dia 30 de mayo de 2003
The goal of this paper is to present an objective analysis of micro-deformational fabrics observe... more The goal of this paper is to present an objective analysis of micro-deformational fabrics observed in the basement exposed in the center-east of the sierra de Comechingones. This basement is a metamorphic complex consisting mainly of metatexites, diatexites and minor bodies of gneisses rich in biotite and garnet, amphibolites, phyllonites, including small outcrops of marbles, and pegmatites. The assemblage of microstructures and microtextures developed during metamorphism and migmatization (poikiloblastic and symplectite textures) together with intracrystalline microstructures related to deformational stages (mechanical twinning, kinking, diffusion creep, recovery, among others) can be used to find the mechanisms and thermobarometric conditions that took place in the studied metamorphic complex. On this basis, the geological history of the complex has been divided in three stages. A first event M 1 - D 1 was developed in medium-grade conditions in almandine-amphibolite facies (6 kba...
The trophic state of a water body is determined by indexes, which allow an overall assessment of ... more The trophic state of a water body is determined by indexes, which allow an overall assessment of the quality of the reservoir. However, the main disadvantage of this methodology is its limited ability to expose spatio-temporal differences in the reservoir. Thus, there is a strong need to develop new technologies that can extend the scope of monitoring and management of water resources. The objective of this study is to determine the dynamic of the trophic state of Rio Tercero Reservoir (Cordoba, Argentina), from the combination of preestablished geostatistical models, constructed from remote sensing data, and trophic indexes. In addition, the generated models were validated using data collected in new sampling campaings. Variables were measured in 15 sampling sites during two sampling campaigns (dry and wet seasons). Measured chlorophyll a concentration (Chl a) was combined with Landsat ETM+ data and geostatistical models to determine the spatio-temporal distribution of this variabl...
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Landsat satellites, 5 and 7, have significant potential for estimating several water quality para... more Landsat satellites, 5 and 7, have significant potential for estimating several water quality parameters, but to our knowledge, there are few investigations which integrate these earlier sensors with the newest and improved mission of Landsat 8 satellite. Thus, the comparability of water quality assessing across different Landsat sensors needs to be evaluated. The main objective of this study was to assess the feasibility of integrating Landsat sensors to estimate chlorophyll-a concentration (Chl-a) in Río Tercero reservoir (Argentina). A general model to retrieve Chl-a was developed (R2 = 0.88). Using observed versus predicted Chl-a values the model was validated (R2 = 0.89) and applied to Landsat imagery obtaining spatial representations of Chl-a in the reservoir. Results showed that Landsat 8 can be combined with Landsat 5 and 7 to construct an empirical model to estimate water quality characteristics, such as Chl-a in a reservoir. As the number of available and upcoming sensors w...
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
The new Sentinel-2 satellites present a significant scientific opportunity for the study of water... more The new Sentinel-2 satellites present a significant scientific opportunity for the study of water quality. The objective of this study was to evaluate the suitability of Sentinel-2 imagery for estimating and mapping Secchi disk transparency (SDT) in Río Tercero reservoir (Córdoba-Argentina). Field observations and a dataset of atmospherically corrected Sentinel-2 images were used to generate and validate an algorithm to estimate water clarity in the studied reservoir. As a real application of the used methodology, the validated algorithm was used to obtain a spatial representation of water clarity in the reservoir during sampling campaigns. Results demonstrate capabilities of Sentinel-2 mission to make a substantial contribution to the current assessment and understanding of aquatic systems by estimating and mapping a water quality characteristic.
International Journal of Hydrology Science and Technology, 2018
Regular water quality monitoring programs are an important aspect of water management. Different ... more Regular water quality monitoring programs are an important aspect of water management. Different multivariate statistical techniques were applied for interpretation and evaluation of the data matrix obtained during a six-year monitoring program (2006 to 2011) in the principal reservoirs of the central region of Argentina. Eleven sampling sites located in two reservoirs were surveyed each climatic season for 18 parameters. Cluster analysis grouped the sampling sites into three clusters and classified the different climatic seasons into two clusters based on their similarities. Principal component analysis/factor analysis showed the existence of five significant varifactors (VF) which account for 79.3% of the variance, related to soluble salts, nutrients, physico-chemical parameters, and non-common source. Source contribution was calculated using multiple regression of sample mass concentration on the absolute VF scores. This study demonstrates the usefulness of multivariate statistical techniques helping managers to get better information about surface water systems.
Abstract The Guacha Corral shear zone (GCSZ) is represented by mylonites that were developed unde... more Abstract The Guacha Corral shear zone (GCSZ) is represented by mylonites that were developed under amphibolites facies conditions from migmatitic protoliths. In this contribution, geophysical, petrological and structural data were combined to determine the 3D geometry of the GCSZ. New gravimetric, magnetometric and structural studies, along an E-W profile, were integrated with existing magnetotelluric and seismological data from a representative regional database of the Eastern Sierras Pampeanas. The zonation of different fabrics across the GCSZ suggests that the pre-existing heterogeneities of the protoliths played a key role in governing the degree of metamorphism of different regions. The low gravity anomalies observed in the GCSZ suggest a transitional boundary zone between the migmatitic and mylonitic domains, where highly deformed shear bands are interspersed with undeformed rocks, presenting gradual contacts. The mylonites in this shear zone show a considerably reduced density when compared to the migmatite protoliths. The density of the rocks gradually increases with depth until it reaches that of the protolith. These changes in the gravity values in response to density changes allowed us to infer a listric geometry at depth of the GCSZ. Low gravity anomalies in the profiles, in regions where high density rocks (migmatites) outcrop at the surface, modeled as buried granitic plutons.
El distrito pegmatítico Comechingones, ubicado en el faldeo oriental de la sierra homónima, en la... more El distrito pegmatítico Comechingones, ubicado en el faldeo oriental de la sierra homónima, en la provincia de Córdoba, involucra pegmatitas graníticas correspondientes a la clase de Elementos Raros, tipo berilo, subtipo berilo-columbita-fosfatos, algunas en transición a la clase muscovítica, con mineralizaciones de Be-Nb-Ta-U y minerales industriales. Dos tipos de pegmatitas graníticas han sido descriptas en el sector sur del distrito: pegmatitas tipo I, con tamaños que en total pueden alcanzan los 1000 metros de longitud y superar los 50 de ancho, internamente zonadas y portadoras de Be, Nb-Ta y U; y pegmatitas tipo II, de menores dimensiones, no zonadas, ricas en cuarzo de alta pureza, carentes de mineralizaciones metalíferas, y asociadas espacial y genéticamente con leucogranitos aplíticos. En este trabajo se presentan y discuten los datos geoquímicos preliminares de ambos tipos de pegmatitas y granitos asociados. Los datos geoquímicos obtenidos, apoyados con descripciones de campo y petrográficas, permiten establecer que las dos tipologías de pegmatitas corresponden a dos eventos magmáticos diferentes (muy probablemente diacrónicos). El primero generó las pegmatitas tipo I, las cuales de sur a norte presentan un aumento en el grado de fraccionamiento desde pegmatitas poco evolucionadas y sin mineralizaciones de elementos raros, hasta pegmatitas evolucionadas con depósitos metalíferos de interés económico. El segundo evento dio origen a las pegmatitas tipo II y a los granitos aplíticos, y carece de especialización metalogenética, evidenciado por los indicadores de diferenciación magmática sistemáticamente inferiores a los de las pegmatitas tipo I y a la carencia de mineralizaciones metalíferas.
La caldera de Piedra Parada constituye el principal edificio volcánico del Complejo Volcánico-Pir... more La caldera de Piedra Parada constituye el principal edificio volcánico del Complejo Volcánico-Piroclástico del curso medio del río Chubut, situado en la provincia argentina de Chubut. Los materiales intracaldera están constituidos por coladas riolíticas, sills andesíticos, domos riolíticos y tobas de composición riolítica. Con objeto de investigar la estructura de la caldera, se han obtenido tanto datos magnéticos terrestres como aeromagnéticos. Los mapas magnéticos muestran que la caldera se encuentra definida por una anomalía magnética de forma circular interrumpida en su parte occidental por varias discontinuidades de dirección NNE-SSO a NE-SO. Los modelos magnéticos llevados a cabo sugieren que la base de la caldera está constituida por materiales de alta susceptibilidad magnética, mientras que el relleno de la misma viene definido por materiales de baja susceptibilidad. Tanto los materiales de la base de la caldera como del relleno afloran como cuerpos adyacentes limitados por planos subverticales, lo que parece indicar la existencia de un proceso de fragmentación y movimientos verticales diferenciales de la caldera.
From structural and magnetic fabric patterns, this work reports a complex folded structure in the... more From structural and magnetic fabric patterns, this work reports a complex folded structure in the La Fronda pluton, a small trondhjemite massif located in the Sierras de Córdoba which form the eastern part of the Sierras Pampeanas in Argentina. Isoclinal folds with no thickening at the hinge zones deform the compositional banding of these igneous rocks. Both the orientation of axial surfaces and fold axes vary from place to place and do not concur with the orientation of folds from the metamorphic country rocks. Microstructural data point to a fabric formed by grain-supported flow in a crystal-rich magma during the imprint of a vanishing regional stress field.
The application of remote sensing technology to water quality monitoring has special significance... more The application of remote sensing technology to water quality monitoring has special significance for lake management at regional scale. Water clarity expressed in terms of Secchi disk transparency (SDT) is a highly useful indicator of trophic status and ecosystem health. In this study, we related Landsat TM and ETM+ data with ground observations to develop a model for the estimation of SDT which can be used as a standardized procedure for regional-scale lake clarity assessment in the central region of Argentina. Samples were taken from two reservoirs of the region. Pearson correlation coefficients and step-wise multiple regression analysis were used to evaluate correlation between Landsat bands and measured SDT. Results suggested that Landsat band 3 plus the ratio 1/3 was a consistent and reliable predictor of SDT (R2 = 0.80). The algorithm was validated (R2 = 0.81) and applied to the November 10, 2010 ETM+ image obtaining a map that characterized water clarity of reservoirs within...
Resumen: El presente trabajo aborda las relaciones de campo y los rasgos petrológicos y estructur... more Resumen: El presente trabajo aborda las relaciones de campo y los rasgos petrológicos y estructurales del basamento cristalino encajonante del Batolito Cerro Áspero, Sierra de Comechingones, Córdoba. El complejo metamórfico está compuesto principalmente por metatexitas y diatexítas, de manera subordinada aparecen cuerpos de gneises biotíticos granatíferos, anfibolitas, filonitas, pequeños bancos de mármoles y cuerpos pegmatíticos graníticos. Se ha inferido para este conjunto litológico, un protolito heterogéneo que grada desde pelitas típicas a pelitas bajas en alúmina e inclusive grauvacas con cantidades subordinadas de rocas carbonáticas y vulcanitas. Estos estudios y las correlaciones regionales permitieron establecer una secuencia evolutiva para el área.
Resumen: En este trabajo se presenta un modelo descriptivo de vetas mesotermales portadoras de Pb... more Resumen: En este trabajo se presenta un modelo descriptivo de vetas mesotermales portadoras de Pb-Zn-Ag-Au hospedadas en milonitas de la Faja de Cizalla Guacha Corral (FCGC) a ~2 km al este del Batolito Cerro Áspero (BCA) en la Sierra de Comechingones, Córdoba. Las mineralizaciones conforman cuerpos tabulares de alto buzamiento, con un control estructural marcado y un desarrollo longitudinal discontinuo en dirección NOSE que alcanza los 8 km. Las vetas mayores poseen potencias entre 0,2 y 1 m y se asocian con vetillas menores que definen diversos juegos secundarios. Están compuestas principalmente de cuarzo que es portador de una variedad de sulfuros, óxidos y carbonatos, tanto de origen hipogénico como supergénico. Los mayores tenores de metales preciosos se registraron en las zonas de oxidación de los depósitos, con valores entre 1,63-3,57 g/t de Au y 149-216 g/t de Ag. La alteración hidrotermal de las rocas de caja es común y en sectores muy desarrollada. Consiste principalmente de sericitización penetrativa y hematización de moderada a fuerte intensidad que se desarrolla en venillas tensionales. Subordinadamente ocurren silicificación y carbonatación. Las relaciones de campo, evidencias estructurales, microestructurales y petrográficas sugieren que el emplazamiento de estos depósitos ha ocurrido posteriormente a la última fase de deformación de la FCGC, bajo un regimen de cizalla simple. La vinculación de las mineralizaciones con el BCA no ha podido establecerse aún en este modelo descriptivo. Los estudios a futuro están principalmente orientados a determinar la influencia del magmatismo devónico como un posible metalotecto de las mineralizaciones.
The Ángel pegmatite forms part of the Comechingones pegmatitic field, in central Argentina, which... more The Ángel pegmatite forms part of the Comechingones pegmatitic field, in central Argentina, which is made up of pegmatites characterized by low to intermediate degrees of fractionation, classified as beryl-columbite-phosphate subtype pegmatites. These pegmatites are syntectonic with a regional shear zone. The Ángel pegmatite contains associations with quartz, microcline, plagioclase, a first generation of muscovite (muscovite I), beryl, members of the columbite group, triplite, and montebrasite. This association is locally affected by two stages of replacement. The first replacement stage is characterized by early albitization, followed by the development of associations of cleavelandite, quartz, Fe-rich elbaite (elbaite I), a second generation of muscovite (muscovite II), topaz, lacroixite, fluorapatite, pollucite, columbite-(Mn), and Hf-rich zircon. Muscovite II replaces montebrasite and muscovite I, and is characterized by slight enrichments in F, Rb, and Cs. The second replacement stage generated a new mineral association characterized by muscovite III, Fe-poor elbaite (elbaite II), Cs-micas, and U-rich hydroxykenomicrolite. Muscovite III replaces muscovite II and is characterized by strong enrichments in F, Cs, and, to a lesser extent, Rb. In turn, muscovite III is replaced by the Cs-micas sokolovaite and nanpingite. The high F content of the nanpingite suggests that this could be the F-analogue of nanpingite, which would be a new mineral. The sequence of replacement is indicative of an increase in the F activity in the latest pegmatitic fluids. The high F activity of these fluids favored the transport of Ta, U, Bi, Hf, Rb, Cs, and Li, and the formation of F-rich micas could be the mechanism for precipitating these LILE and HFSE elements. The syntectonic emplacement of this pegmatite in a large shear zone could be a decisive factor in the migration of these late evolved fluids rich in F, LILE, and HFSE.
This study deals with the structure and emplacement of the Calmayo and El Hongo trondhjemite plut... more This study deals with the structure and emplacement of the Calmayo and El Hongo trondhjemite plutons (Famatinian belt of C ordoba, Argentina). It provides structural data from the granites and the country rocks and a study of the magnetic fabric in the plutons. New U/Pb geochronological data yield intrusion ages of 512.1 AE 3.4 Ma and 500.6 AE 4.5 Ma for the Calmayo and El Hongo plutons respectively. The El Hongo massif and the southern part of the Calmayo trondhjemite preserve magmatic structures, whereas the northern domain of Calmayo shows the imprint of solid-state deformation. The main foliation in the country rocks outlines a boudin-like pattern at the map scale and the granites are located along boudin necks, suggesting that the emplacement of these trondhjemite plutons was linked to large-scale boudinage of the country rocks.
Remote sensing can be used as a complementary tool in water quality monitoring of aquatic ecosyst... more Remote sensing can be used as a complementary tool in water quality monitoring of aquatic ecosystems. The aim of this study was to develop models to estimate the spatial distribution of chlorophyll-a concentration (Chl-a) in Los Molinos reservoir using Landsat 7 ETM + and ASTER imagery. Los Molinos reservoir (32 o 49 ‘S, 64 o 32’ W) is a multipurpose system used as the second source of water supply for Cordoba’s city. Physical, chemical and biological parameters were measured in the water body coinciding with the passage of the satellites by the study area. Using different statistical techniques, satellite information was related to field data obtaining algorithms that best explained the distribution of Chl-a. These models were validated and used to construct maps providing spatially rich information on patterns of water quality throughout the reservoir. Both sensors could be used for Chl-a monitoring. ASTER sensor, with higher spatial resolution that ETM+, showed a better relations...
Ponencia presentada en la 34a Sesion Cientifica de la Sociedad Geologica de Espana, celebrada en ... more Ponencia presentada en la 34a Sesion Cientifica de la Sociedad Geologica de Espana, celebrada en la Facultad de Ciencias de la Universidad del Pais Vasco, Campus de Leioa (Bilbao) el dia 30 de mayo de 2003
The goal of this paper is to present an objective analysis of micro-deformational fabrics observe... more The goal of this paper is to present an objective analysis of micro-deformational fabrics observed in the basement exposed in the center-east of the sierra de Comechingones. This basement is a metamorphic complex consisting mainly of metatexites, diatexites and minor bodies of gneisses rich in biotite and garnet, amphibolites, phyllonites, including small outcrops of marbles, and pegmatites. The assemblage of microstructures and microtextures developed during metamorphism and migmatization (poikiloblastic and symplectite textures) together with intracrystalline microstructures related to deformational stages (mechanical twinning, kinking, diffusion creep, recovery, among others) can be used to find the mechanisms and thermobarometric conditions that took place in the studied metamorphic complex. On this basis, the geological history of the complex has been divided in three stages. A first event M 1 - D 1 was developed in medium-grade conditions in almandine-amphibolite facies (6 kba...
The trophic state of a water body is determined by indexes, which allow an overall assessment of ... more The trophic state of a water body is determined by indexes, which allow an overall assessment of the quality of the reservoir. However, the main disadvantage of this methodology is its limited ability to expose spatio-temporal differences in the reservoir. Thus, there is a strong need to develop new technologies that can extend the scope of monitoring and management of water resources. The objective of this study is to determine the dynamic of the trophic state of Rio Tercero Reservoir (Cordoba, Argentina), from the combination of preestablished geostatistical models, constructed from remote sensing data, and trophic indexes. In addition, the generated models were validated using data collected in new sampling campaings. Variables were measured in 15 sampling sites during two sampling campaigns (dry and wet seasons). Measured chlorophyll a concentration (Chl a) was combined with Landsat ETM+ data and geostatistical models to determine the spatio-temporal distribution of this variabl...
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Landsat satellites, 5 and 7, have significant potential for estimating several water quality para... more Landsat satellites, 5 and 7, have significant potential for estimating several water quality parameters, but to our knowledge, there are few investigations which integrate these earlier sensors with the newest and improved mission of Landsat 8 satellite. Thus, the comparability of water quality assessing across different Landsat sensors needs to be evaluated. The main objective of this study was to assess the feasibility of integrating Landsat sensors to estimate chlorophyll-a concentration (Chl-a) in Río Tercero reservoir (Argentina). A general model to retrieve Chl-a was developed (R2 = 0.88). Using observed versus predicted Chl-a values the model was validated (R2 = 0.89) and applied to Landsat imagery obtaining spatial representations of Chl-a in the reservoir. Results showed that Landsat 8 can be combined with Landsat 5 and 7 to construct an empirical model to estimate water quality characteristics, such as Chl-a in a reservoir. As the number of available and upcoming sensors w...
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
The new Sentinel-2 satellites present a significant scientific opportunity for the study of water... more The new Sentinel-2 satellites present a significant scientific opportunity for the study of water quality. The objective of this study was to evaluate the suitability of Sentinel-2 imagery for estimating and mapping Secchi disk transparency (SDT) in Río Tercero reservoir (Córdoba-Argentina). Field observations and a dataset of atmospherically corrected Sentinel-2 images were used to generate and validate an algorithm to estimate water clarity in the studied reservoir. As a real application of the used methodology, the validated algorithm was used to obtain a spatial representation of water clarity in the reservoir during sampling campaigns. Results demonstrate capabilities of Sentinel-2 mission to make a substantial contribution to the current assessment and understanding of aquatic systems by estimating and mapping a water quality characteristic.
International Journal of Hydrology Science and Technology, 2018
Regular water quality monitoring programs are an important aspect of water management. Different ... more Regular water quality monitoring programs are an important aspect of water management. Different multivariate statistical techniques were applied for interpretation and evaluation of the data matrix obtained during a six-year monitoring program (2006 to 2011) in the principal reservoirs of the central region of Argentina. Eleven sampling sites located in two reservoirs were surveyed each climatic season for 18 parameters. Cluster analysis grouped the sampling sites into three clusters and classified the different climatic seasons into two clusters based on their similarities. Principal component analysis/factor analysis showed the existence of five significant varifactors (VF) which account for 79.3% of the variance, related to soluble salts, nutrients, physico-chemical parameters, and non-common source. Source contribution was calculated using multiple regression of sample mass concentration on the absolute VF scores. This study demonstrates the usefulness of multivariate statistical techniques helping managers to get better information about surface water systems.
Abstract The Guacha Corral shear zone (GCSZ) is represented by mylonites that were developed unde... more Abstract The Guacha Corral shear zone (GCSZ) is represented by mylonites that were developed under amphibolites facies conditions from migmatitic protoliths. In this contribution, geophysical, petrological and structural data were combined to determine the 3D geometry of the GCSZ. New gravimetric, magnetometric and structural studies, along an E-W profile, were integrated with existing magnetotelluric and seismological data from a representative regional database of the Eastern Sierras Pampeanas. The zonation of different fabrics across the GCSZ suggests that the pre-existing heterogeneities of the protoliths played a key role in governing the degree of metamorphism of different regions. The low gravity anomalies observed in the GCSZ suggest a transitional boundary zone between the migmatitic and mylonitic domains, where highly deformed shear bands are interspersed with undeformed rocks, presenting gradual contacts. The mylonites in this shear zone show a considerably reduced density when compared to the migmatite protoliths. The density of the rocks gradually increases with depth until it reaches that of the protolith. These changes in the gravity values in response to density changes allowed us to infer a listric geometry at depth of the GCSZ. Low gravity anomalies in the profiles, in regions where high density rocks (migmatites) outcrop at the surface, modeled as buried granitic plutons.
El distrito pegmatítico Comechingones, ubicado en el faldeo oriental de la sierra homónima, en la... more El distrito pegmatítico Comechingones, ubicado en el faldeo oriental de la sierra homónima, en la provincia de Córdoba, involucra pegmatitas graníticas correspondientes a la clase de Elementos Raros, tipo berilo, subtipo berilo-columbita-fosfatos, algunas en transición a la clase muscovítica, con mineralizaciones de Be-Nb-Ta-U y minerales industriales. Dos tipos de pegmatitas graníticas han sido descriptas en el sector sur del distrito: pegmatitas tipo I, con tamaños que en total pueden alcanzan los 1000 metros de longitud y superar los 50 de ancho, internamente zonadas y portadoras de Be, Nb-Ta y U; y pegmatitas tipo II, de menores dimensiones, no zonadas, ricas en cuarzo de alta pureza, carentes de mineralizaciones metalíferas, y asociadas espacial y genéticamente con leucogranitos aplíticos. En este trabajo se presentan y discuten los datos geoquímicos preliminares de ambos tipos de pegmatitas y granitos asociados. Los datos geoquímicos obtenidos, apoyados con descripciones de campo y petrográficas, permiten establecer que las dos tipologías de pegmatitas corresponden a dos eventos magmáticos diferentes (muy probablemente diacrónicos). El primero generó las pegmatitas tipo I, las cuales de sur a norte presentan un aumento en el grado de fraccionamiento desde pegmatitas poco evolucionadas y sin mineralizaciones de elementos raros, hasta pegmatitas evolucionadas con depósitos metalíferos de interés económico. El segundo evento dio origen a las pegmatitas tipo II y a los granitos aplíticos, y carece de especialización metalogenética, evidenciado por los indicadores de diferenciación magmática sistemáticamente inferiores a los de las pegmatitas tipo I y a la carencia de mineralizaciones metalíferas.
La caldera de Piedra Parada constituye el principal edificio volcánico del Complejo Volcánico-Pir... more La caldera de Piedra Parada constituye el principal edificio volcánico del Complejo Volcánico-Piroclástico del curso medio del río Chubut, situado en la provincia argentina de Chubut. Los materiales intracaldera están constituidos por coladas riolíticas, sills andesíticos, domos riolíticos y tobas de composición riolítica. Con objeto de investigar la estructura de la caldera, se han obtenido tanto datos magnéticos terrestres como aeromagnéticos. Los mapas magnéticos muestran que la caldera se encuentra definida por una anomalía magnética de forma circular interrumpida en su parte occidental por varias discontinuidades de dirección NNE-SSO a NE-SO. Los modelos magnéticos llevados a cabo sugieren que la base de la caldera está constituida por materiales de alta susceptibilidad magnética, mientras que el relleno de la misma viene definido por materiales de baja susceptibilidad. Tanto los materiales de la base de la caldera como del relleno afloran como cuerpos adyacentes limitados por planos subverticales, lo que parece indicar la existencia de un proceso de fragmentación y movimientos verticales diferenciales de la caldera.
From structural and magnetic fabric patterns, this work reports a complex folded structure in the... more From structural and magnetic fabric patterns, this work reports a complex folded structure in the La Fronda pluton, a small trondhjemite massif located in the Sierras de Córdoba which form the eastern part of the Sierras Pampeanas in Argentina. Isoclinal folds with no thickening at the hinge zones deform the compositional banding of these igneous rocks. Both the orientation of axial surfaces and fold axes vary from place to place and do not concur with the orientation of folds from the metamorphic country rocks. Microstructural data point to a fabric formed by grain-supported flow in a crystal-rich magma during the imprint of a vanishing regional stress field.
The application of remote sensing technology to water quality monitoring has special significance... more The application of remote sensing technology to water quality monitoring has special significance for lake management at regional scale. Water clarity expressed in terms of Secchi disk transparency (SDT) is a highly useful indicator of trophic status and ecosystem health. In this study, we related Landsat TM and ETM+ data with ground observations to develop a model for the estimation of SDT which can be used as a standardized procedure for regional-scale lake clarity assessment in the central region of Argentina. Samples were taken from two reservoirs of the region. Pearson correlation coefficients and step-wise multiple regression analysis were used to evaluate correlation between Landsat bands and measured SDT. Results suggested that Landsat band 3 plus the ratio 1/3 was a consistent and reliable predictor of SDT (R2 = 0.80). The algorithm was validated (R2 = 0.81) and applied to the November 10, 2010 ETM+ image obtaining a map that characterized water clarity of reservoirs within...
Resumen: El presente trabajo aborda las relaciones de campo y los rasgos petrológicos y estructur... more Resumen: El presente trabajo aborda las relaciones de campo y los rasgos petrológicos y estructurales del basamento cristalino encajonante del Batolito Cerro Áspero, Sierra de Comechingones, Córdoba. El complejo metamórfico está compuesto principalmente por metatexitas y diatexítas, de manera subordinada aparecen cuerpos de gneises biotíticos granatíferos, anfibolitas, filonitas, pequeños bancos de mármoles y cuerpos pegmatíticos graníticos. Se ha inferido para este conjunto litológico, un protolito heterogéneo que grada desde pelitas típicas a pelitas bajas en alúmina e inclusive grauvacas con cantidades subordinadas de rocas carbonáticas y vulcanitas. Estos estudios y las correlaciones regionales permitieron establecer una secuencia evolutiva para el área.
Resumen: En este trabajo se presenta un modelo descriptivo de vetas mesotermales portadoras de Pb... more Resumen: En este trabajo se presenta un modelo descriptivo de vetas mesotermales portadoras de Pb-Zn-Ag-Au hospedadas en milonitas de la Faja de Cizalla Guacha Corral (FCGC) a ~2 km al este del Batolito Cerro Áspero (BCA) en la Sierra de Comechingones, Córdoba. Las mineralizaciones conforman cuerpos tabulares de alto buzamiento, con un control estructural marcado y un desarrollo longitudinal discontinuo en dirección NOSE que alcanza los 8 km. Las vetas mayores poseen potencias entre 0,2 y 1 m y se asocian con vetillas menores que definen diversos juegos secundarios. Están compuestas principalmente de cuarzo que es portador de una variedad de sulfuros, óxidos y carbonatos, tanto de origen hipogénico como supergénico. Los mayores tenores de metales preciosos se registraron en las zonas de oxidación de los depósitos, con valores entre 1,63-3,57 g/t de Au y 149-216 g/t de Ag. La alteración hidrotermal de las rocas de caja es común y en sectores muy desarrollada. Consiste principalmente de sericitización penetrativa y hematización de moderada a fuerte intensidad que se desarrolla en venillas tensionales. Subordinadamente ocurren silicificación y carbonatación. Las relaciones de campo, evidencias estructurales, microestructurales y petrográficas sugieren que el emplazamiento de estos depósitos ha ocurrido posteriormente a la última fase de deformación de la FCGC, bajo un regimen de cizalla simple. La vinculación de las mineralizaciones con el BCA no ha podido establecerse aún en este modelo descriptivo. Los estudios a futuro están principalmente orientados a determinar la influencia del magmatismo devónico como un posible metalotecto de las mineralizaciones.
The Ángel pegmatite forms part of the Comechingones pegmatitic field, in central Argentina, which... more The Ángel pegmatite forms part of the Comechingones pegmatitic field, in central Argentina, which is made up of pegmatites characterized by low to intermediate degrees of fractionation, classified as beryl-columbite-phosphate subtype pegmatites. These pegmatites are syntectonic with a regional shear zone. The Ángel pegmatite contains associations with quartz, microcline, plagioclase, a first generation of muscovite (muscovite I), beryl, members of the columbite group, triplite, and montebrasite. This association is locally affected by two stages of replacement. The first replacement stage is characterized by early albitization, followed by the development of associations of cleavelandite, quartz, Fe-rich elbaite (elbaite I), a second generation of muscovite (muscovite II), topaz, lacroixite, fluorapatite, pollucite, columbite-(Mn), and Hf-rich zircon. Muscovite II replaces montebrasite and muscovite I, and is characterized by slight enrichments in F, Rb, and Cs. The second replacement stage generated a new mineral association characterized by muscovite III, Fe-poor elbaite (elbaite II), Cs-micas, and U-rich hydroxykenomicrolite. Muscovite III replaces muscovite II and is characterized by strong enrichments in F, Cs, and, to a lesser extent, Rb. In turn, muscovite III is replaced by the Cs-micas sokolovaite and nanpingite. The high F content of the nanpingite suggests that this could be the F-analogue of nanpingite, which would be a new mineral. The sequence of replacement is indicative of an increase in the F activity in the latest pegmatitic fluids. The high F activity of these fluids favored the transport of Ta, U, Bi, Hf, Rb, Cs, and Li, and the formation of F-rich micas could be the mechanism for precipitating these LILE and HFSE elements. The syntectonic emplacement of this pegmatite in a large shear zone could be a decisive factor in the migration of these late evolved fluids rich in F, LILE, and HFSE.
This study deals with the structure and emplacement of the Calmayo and El Hongo trondhjemite plut... more This study deals with the structure and emplacement of the Calmayo and El Hongo trondhjemite plutons (Famatinian belt of C ordoba, Argentina). It provides structural data from the granites and the country rocks and a study of the magnetic fabric in the plutons. New U/Pb geochronological data yield intrusion ages of 512.1 AE 3.4 Ma and 500.6 AE 4.5 Ma for the Calmayo and El Hongo plutons respectively. The El Hongo massif and the southern part of the Calmayo trondhjemite preserve magmatic structures, whereas the northern domain of Calmayo shows the imprint of solid-state deformation. The main foliation in the country rocks outlines a boudin-like pattern at the map scale and the granites are located along boudin necks, suggesting that the emplacement of these trondhjemite plutons was linked to large-scale boudinage of the country rocks.
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Papers by Lucio PINOTTI