Papers by Sandro Kucera Duarte
Journal of Sedimentary Environments, Jun 1, 2020
The Paraná Volcanic Province follows Siberia as the second largest in the continents and offers a... more The Paraná Volcanic Province follows Siberia as the second largest in the continents and offers a unique opportunity to study the hydrothermal relationship between basalt-rhyodacite lavas and buried erg-turned aquifer in an intraplate setting. Injected sand fluidized after basalt sealing and was succeeded by amethyst and agate geode opening and filling. Excellent exposures in the Herveiras cuesta, southern Brazil, allow the comparison of processes over long distances (1500 km) in the volcanic group. Fieldwork and basalt chemistry led to the identification of three hydrothermal processes-amygdales filling (H1), sand injection (H2) and amethyst geodes formation (H3). Sand injection was triggered by high temperature (150 ℃) and seismicity. These low-temperature processes identified in the Herveiras cuesta demonstrate the homogeneity of relationships between the paleoerg, giant aquifer and intraplate volcanic rocks across the volcanic province.
Compasso Lugar-Cultura eBooks, 2021
Geologia USP. Série Científica, Dec 1, 2014
Journal of South American Earth Sciences, Dec 1, 2021
Journal of South American Earth Sciences, Oct 1, 2020
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.
Journal of South American Earth Sciences, Apr 1, 2020
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.
International Geology Review, Nov 30, 2012
ABSTRACT
Journal of Volcanology and Geothermal Research, Sep 1, 2012
The Cretaceous interaction of the heated, giant Guarani aquifer with lavas, dikes and sills of th... more The Cretaceous interaction of the heated, giant Guarani aquifer with lavas, dikes and sills of the Paraná volcanic province is here evaluated based on the description of the large exposures in Torres, southernmost Brazil. Chalcedony silicified sandstone dikes, sills and breccias containing volcanic clasts in a sandstone matrix are common in the Paraná volcanic province. Sandstone layers mark either the contact between lava flows or the base of the vertically-jointed, massive core. In Torres, one basaltic andesite and one andesite lava flow of the low-Ti Gramado type, and basalt and basaltic andesite sills and dikes, are correlated over 10 km with rocks in the Graxaim quarry. Scintillometric emission rates vary systematically with contents of K, Th and U and are characteristic of each lava or intrusive rock. Major and trace elements are also characteristic of each lava. Three large outcrops of breccias display angular, amygdaloidal volcanic clasts immersed in a silicified sandstone matrix. No evidence was found of high temperature (1150°C) interaction of the lava with the loose, erg of the Botucatu Formation, such as fluidal volcanic clasts, quenched rims or thermal recrystallization of the sand; only a thin (5 mm) layer of thermally modified sand is present on top of a paleodune in Torres. In Torres, the interaction of andesite with wet sand occurred after degassing of the lava, because the breccia clasts are amygdaloidal. All evidence points to hydrothermal processes for the formation of the breccias, such as lozenge fractures filled with silicified sandstone, preserved detrital characteristics of the sandstone grains and cold (below 130°C) contact between the volcanic rock and the sand. Most significant is the timing of sand intrusion, because thin (1 mm) dikes of silicified sandstone cut fractures in the rock and the zeolitefilled amygdales. The sandstone dikes, sills and breccias are interpreted as a result of the ascent of overpressured heated water and its vapor from the huge, underlying Guarani aquifer, carrying fluidized sand and continuously silicifying the intruded sand. The three breccias are sills intruded into cold lava flows. The description and correlation of the magmatic bodies and the field relationships of the silicified sandstones establish the stratigraphy of the Paraná volcanic province in Torres and elucidate the processes responsible for the injection and effusion of sand in the Cretaceous.
Contribuições à Geologia do Rio Grande do Sul e de Santa Catarina, 2021
Alteration and very-low grade metamorphism of basaltic rocks in the southern Parana volcanic prov... more Alteration and very-low grade metamorphism of basaltic rocks in the southern Parana volcanic province led to the generation of giant amethyst geodes and to significant modification in geochemical composition of some elements. The two main amethyst and agate mining districts are Ametista do Sul (Brazil) and Artigas (Uruguay), 600 ton/month. In the Quarai amethyst district, the five lava flows present were submitted to intense hydrothermal processes that caused the chemical alteration of rocks. The five lavas (flows Mata Olho, Catalan, Cordillera, Muralha and Coxilha) were recognized in the field and positioned in correct stratigraphic succession. All rocks are low-Ti (< 2.0 wt % TiO2) of the Gramado type and belong to the Serra Geral Formation. Their SiO2 contents are 51.0, 57.5, 52.5, 56.0 and 54.5 wt %. The first flow is basalt, followed by andesite and the other are basaltic andesites. The mineralized andesite and basaltic andesite (flows Catalan and Cordillera) were intensely ...
Journal of South American Earth Sciences, 2021
Journal of Sedimentary Environments, 2020
The Paraná Volcanic Province follows Siberia as the second largest in the continents and offers a... more The Paraná Volcanic Province follows Siberia as the second largest in the continents and offers a unique opportunity to study the hydrothermal relationship between basalt-rhyodacite lavas and buried erg-turned aquifer in an intraplate setting. Injected sand fluidized after basalt sealing and was succeeded by amethyst and agate geode opening and filling. Excellent exposures in the Herveiras cuesta, southern Brazil, allow the comparison of processes over long distances (1500 km) in the volcanic group. Fieldwork and basalt chemistry led to the identification of three hydrothermal processes-amygdales filling (H1), sand injection (H2) and amethyst geodes formation (H3). Sand injection was triggered by high temperature (150 ℃) and seismicity. These low-temperature processes identified in the Herveiras cuesta demonstrate the homogeneity of relationships between the paleoerg, giant aquifer and intraplate volcanic rocks across the volcanic province.
Journal of South American Earth Sciences, 2020
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.
Journal of South American Earth Sciences, 2020
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.
Geologia USP. Série Científica, 2014
Journal of Volcanology and Geothermal Research, 2012
The Cretaceous interaction of the heated, giant Guarani aquifer with lavas, dikes and sills of th... more The Cretaceous interaction of the heated, giant Guarani aquifer with lavas, dikes and sills of the Paraná volcanic province is here evaluated based on the description of the large exposures in Torres, southernmost Brazil. Chalcedony silicified sandstone dikes, sills and breccias containing volcanic clasts in a sandstone matrix are common in the Paraná volcanic province. Sandstone layers mark either the contact between lava flows or the base of the vertically-jointed, massive core. In Torres, one basaltic andesite and one andesite lava flow of the low-Ti Gramado type, and basalt and basaltic andesite sills and dikes, are correlated over 10 km with rocks in the Graxaim quarry. Scintillometric emission rates vary systematically with contents of K, Th and U and are characteristic of each lava or intrusive rock. Major and trace elements are also characteristic of each lava. Three large outcrops of breccias display angular, amygdaloidal volcanic clasts immersed in a silicified sandstone matrix. No evidence was found of high temperature (1150°C) interaction of the lava with the loose, erg of the Botucatu Formation, such as fluidal volcanic clasts, quenched rims or thermal recrystallization of the sand; only a thin (5 mm) layer of thermally modified sand is present on top of a paleodune in Torres. In Torres, the interaction of andesite with wet sand occurred after degassing of the lava, because the breccia clasts are amygdaloidal. All evidence points to hydrothermal processes for the formation of the breccias, such as lozenge fractures filled with silicified sandstone, preserved detrital characteristics of the sandstone grains and cold (below 130°C) contact between the volcanic rock and the sand. Most significant is the timing of sand intrusion, because thin (1 mm) dikes of silicified sandstone cut fractures in the rock and the zeolitefilled amygdales. The sandstone dikes, sills and breccias are interpreted as a result of the ascent of overpressured heated water and its vapor from the huge, underlying Guarani aquifer, carrying fluidized sand and continuously silicifying the intruded sand. The three breccias are sills intruded into cold lava flows. The description and correlation of the magmatic bodies and the field relationships of the silicified sandstones establish the stratigraphy of the Paraná volcanic province in Torres and elucidate the processes responsible for the injection and effusion of sand in the Cretaceous.
International Geology Review, 2012
ABSTRACT
International Journal of Earth Sciences, 2013
ABSTRACT The capability of determining the flow-by-flow stratigraphy and the long-distance correl... more ABSTRACT The capability of determining the flow-by-flow stratigraphy and the long-distance correlation of lava flows in large continental volcanic provinces leads to a considerable advance in the understanding of processes related to generation and evolution of the lavas. The Paraná volcanic province is exposed along the Serra Geral cuesta of southern Brazil in a steeply inclined, 1,000-m-high section starting 40-m above sea level. Each of the 10–20 pahoehoe flows and rhyodacite flow units has a unique chemical composition. Integrated with field stratigraphy and gamma-spectrometric measurements, this leads to the establishment of the correct stratigraphic sequence in each of three different vertical sections. The number of flows integrating the three serras is 26 (“serra” is a mountain range in Portuguese). Each serra has basaltic andesites at the base, whereas rhyodacites are intercalated with basaltic andesites at the top. Three basaltic andesite flows and one rhyodacite flow unit are correlated between Serra Umbu and Serra Boa Vista (10 km). In the Serra Faxinal, a thick (170 m) sill at the base correlates with flow 13F, whereas a dike-sill in the Graxaim quarry (24 km distance) correlates with flow 3F. One basaltic andesite and two rhyodacite flow units correlate between Serra Faxinal and Serra Umbu (50 km). The results are most significant for the understanding of large tracts of continental volcanic provinces with use of common geochemical and gamma-spectrometric techniques.
Uploads
Papers by Sandro Kucera Duarte