Publications
Indexed: 10 Non-indexed: 1 Conference Proceedings: 8
2025
Sequeira, M.D., Tavares, A.O., Castilho, A. & Dinis, P. (2025). Influência da seca
severa em indicadores de águas superficiais. Comunicações Geológicas 112 (Especial 1), 225-228.
During the drought that affected Portugal in the 2021/2022 hydrological year, five surface water monitoring campaigns were carried
out in the Mondego River Basin. Sampling took place from March to November 2022, and the measured water quality indicators were compared
to a geochemical baseline created using open data. During the drought period, surface waters tended to be more alkaline, potentially due to
reduced dilution or a bicarbonate influence from groundwater. In the same period, NO2 concentrations tended to increase, almost always
exceeding normal levels. At the beginning of the following hydrological year, with episodes of heavy rainfall and increased runoff, erosion,
and transport of soil particles, there was a rise in turbidity, with values above normal, associated with excessive concentrations of Al,
Fe, and Mn, while pH and NO2 levels returned to normal (translated).
View more (in Portuguese)
Comunicações Geológicas: IF: 0.300; Q4: Environmental Science; H Index: 20
Sequeira, M.D., Dinis, P., Castilho, A. & Tavares, A.O. (2025). The influence of rural
fires in surface water quality. Comunicações Geológicas 112 (Especial 1), 229-232.
This study focuses on the impact of rural fires on water quality in the Mondego River basin in Portugal. An analysis of water quality
was conducted to assess the interaction between fires, land use, geology, and precipitation. Data from a monitoring program conducted over
two hydrological years were statistically analyzed and compared to a geochemical background. The results reveal substantial increases in the
concentrations of Ca, K, Mg, NO3, SO4, and As in surface waters after the fires. These changes are accompanied by an increase in electrical
conductivity. While some parameters returned to normal concentrations in the following months, As kept with elevated grades in some sites, which
appear to reflect complex interactions between post-fire processes and geology.
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Comunicações Geológicas: IF: 0.300; Q4: Environmental Science; H Index: 20
2024
Sequeira, M.D. (2024). Surface water monitoring for evaluation of drivers of land use and
occupation change. [Doctoral dissertation, University of Coimbra].
Surface water monitoring plays a pivotal role in identify sources of pollution, guiding sustainable practices and preserving aquatic ecosystems.
This works aims at research the effectiveness of surface water monitoring in identifying land use and land cover changes and environmental pressures,
assessing the impacts of land use and occupation changes, identifying drivers of surface water indicators, and formulating responses to
these challenges. The Mondego River Basin located in central Portugal, characterized by diverse geology, land use, and significantly impacted by
the 2017 wildfires and the 2021/2022 drought, was selected as the study area. The research hypotheses were examined through extensive monitoring
and analysis, leading to practical recommendations. Systematic surface water monitoring revealed significant water quality indicators associated
with environmental pressures. These included increases in water turbidity, and aluminum (Al) and iron (Fe) concentrations associated with land cover
changes and increased soil erosion following the wildfires. There were also inputs of ions (e. g. NO3, SO4, Mn) associated with byproducts of
combustion during the fires. Land use conversion from fire-affected areas to agricultural areas was also reflected in surface water indicators,
such as increased concentrations of NO3 and arsenic (As). These indicators are particularly noticeable during periods of higher precipitation,
which demonstrated the role of precipitation in the mobilization of contaminants following land use and cover changes. Long-term monitoring has
proven particularly supportive in identifying the impacts of land use changes on surface water quality. By constructing geochemical baselines
using historical data from the same locations, it is possible to establish a comparison threshold for currently monitored data and assess the
impacts on surface water. Using data from surface water monitoring parameters as dependent variables, and precipitation data and geographical data
of the catchments as independent variables, it was possible to identify that the extent of the impact from wildfires is more significant when the fires
affect developed areas compared to forested areas, highlighting the resilience of ecosystems. Precipitation erosion and transport capacity are higher
after land cover changes due to wildfires, even compared to the first flush following a prolonged hydrological drought. The results of this study indicate
that surface water monitoring allows for the attribution of responses to issues regarding the relationship between land use and occupation
changes and surface water quality. The responses operations range from measures for soil preservation following wildfires, to maintenance of surface
water quality by rehabilitation of the surrounding ecosystems, and recommendations for agricultural restoration following the wildfires. Additionally,
community engagement and stakeholder involvement should also contribute to improve surface water quality in these contexts.
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Areia, N.P., Sequeira, M.D. & Tavares, A.O. (2024). Socio-psychological factors explaining public
engagement andsupport for drought disaster risk management. International Journal of Disaster Risk Reduction, 110, 104643.
Droughts have become a critical high-impact hydro-meteorological disaster and are projected to become more extreme in the near future. The
Iberian Peninsula is unarguably considered a pronounced hot spot for drought. Worrisome projections for drought risk come to emphasize the urgency
of building drought-resilient societies, through integrated risk management processes that bring together all societal spheres, including lay citizens.
However, citizens remain disengaged from climate risk and adaptation processes. Therefore, it is critical to understand how societies respond to
climate-related hazardous processes, such as drought, and to determine the predictors of citizens' engagement in disaster risk management.
To respond to this research need, this study sought to explore citizens' preferences for drought management policies and to ascertain the
psychosocial predictors of citizens' willingness to take action towards drought and support for drought risk management. A cross-sectional study
was implemented, in which 401 Portuguese participants enrolled in a survey questionnaire measuring predictor variables of citizens' willing-ness to
take action and support for drought risk management. A robust set of statistical analysis was implemented, mainly based on structural equation
modelling. Results demonstrate that citizens tend to prefer low-cost measures and policies that due not imply personal heightened burden, at a financial
and behavioral level. Moreover, personal experience with drought, risk perception, perceived urgency and emotional states play a critical role in
citizens’ engagement and sup-port for disaster risk management. Findings are discussed in light of their theoretical and practical implications,
particularly for risk communication and for risk management policymaking.
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International Journal of Disaster Risk Reduction: IF: 4.900; Q1: Geology; H Index: 101
2023
Sequeira, M.D., Tavares, A.O. & Castilo, A. (2023). Influência da seca severa em indicadores de águas
superficiais. XI Congresso Nacional de Geologia: Geociências e Desafios Globais. Livro de Resumos, 465-466.
Five surface water monitoring campaigns were conducted in the Mondego hydrological basin during the drought that affected Portugal in the hydrological
year of 2021/2022. Sampling took place between March and November 2022. Measured water quality indicators were contrasted with a geochemical background
created from open data. During the drought period, the water tends to become more alkaline, due to lower dilution and higher bicarbonate from groundwater
waters, NO2 concentrations kept increasing, exceeding the background; despite the low runoff, most minor ions were undetectable. In the following
hydrological year, with high rainfall events, an increased turbidity was verified, with values above the background, NO2 concentrations return to normal,
and some of the minor ions (Al, As, Fe and Mn) were detectable, some passing the background in all watercourses.
View more
(in Portuguese)
Sequeira, M.D., Dinis, P., Castilho, A. & Tavares, A.O. (2023). The influence of rural fires in surface
water quality. XI Congresso Nacional de Geologia: Geociências e Desafios Globais. Livro de Resumos, 463-464.
After the rural fires that affected Portugal in 2017, nine campaigns of surface water monitoring were conducted over a span of two years in 10
watercourses of the Mondego river basin. The results were analyzed alongside catchment basin characteristics and precipitation data to develop
regression models for each water parameter. It was observed that precipitation introduced Al and NO3 to the surface waters, leading to increased
turbidity while also exhibiting a dilution effect. Carbonate geology tended to elevate concentrations of Ca and HCO3 in the water, along with its
alkalinity, whereas igneous geology influenced the content of As in the water. Agricultural usage appeared to manifest in Cl, K, Na, and electrical
conductivity of the waters. The fire-affected artificial area proved to be the most impactful in the majority of models, seemingly responsible for
a significant portion of As, NO3,
SO4, Ca, K, and Mg, and consequently, for electrical conductivity.
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2022
Sequeira, M.D., Castilho, A., Tavares, A.O. & Dinis, P. (2022). The Rural Fires of 2017 and Their Influences
on Water Quality: An Assessment of Causes and Effects. International Journal of Environmental Research and Public Health, 20(1), 32.
As water is facing increasing pressures from population and economic growth and climate change, it becomes imperative to promote the protection, restoration
and management of this resource and its watersheds. Since water quality depends on multiple factors both natural and anthropic, it is not easy to establish their
influences. After the October 2017 fires that affected almost 30% of the Mondego hydrographic basin in Central Portugal, 10 catchments were selected for periodic
physical-chemical monitoring. These monitoring campaigns started one month after the fires and lasted for two hydrological years, measuring the electric
conductivity (EC), pH, dissolved oxygen (DO), turbidity (Turb), alkalinity (Alk), major and minor ions, and trace elements. The obtained data were then statistically
analysed alongside the geomorphological characteristics of each catchment coupled with features of land-use and occupation. From the results, it was possible to
establish that fire-affected artificial areas, through the atmospheric deposition and surface runoff of combustion products, had the most impact on surface water
quality, increasing As, K−, Ca2+, Mg2+, NO3−, SO42− and Sr, and consequently increasing electrical conductivity. Agricultural land-use seems to play a major influence
in raising the water’s EC, Cl, K− and Na2+. Regarding natural factors such as catchment geology, it was found that the extent of igneous exposures influences As,
and the carbonate sedimentary units are a source of Ca2+ and HCO32− concentrations and impose an increase in alkalinity. Rainfall seems, in the short term, to
increase the water concentration in Al and NO3−, while also raising turbidity due to sediments dragged by surface runoff. While, in the long-term, rainfall
reduces the concentrations of elements in surface water and approximates the water’s pH to rainfall features.
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International Journal of Environmental Research and Public Health: IF: 4.600; Q2: Pollution; H Index: 138
Sequeira, M.D., Castilho, A., Dinis, P. & Tavares, A.O. (2022). Impacte dos incêndios florestais na qualidade
das águas superficiais: um estudo na Bacia Hidrográfica do Mondego. Livro de resumos XX Simpósio Luso-Brasileiro de Engenharia Sanitária e Ambiental, 903-908.
In October 2017, the Central Region of Portugal was severely affected by several forest fires. Nearly 30%
of the Mondego River Basin was impacted. To understand the effects of these fires on surface water quality,
monitoring campaigns were conducted over two hydrological years. Physical and chemical parameters of surface
waters were analyzed at 10 monitoring points. Using 30 years of historical data on these parameters, geochemical
baselines were established to assess the impacts of the fires on surface waters. Immediately after the forest
fires, concentrations of Cl, NO3, SO4, Al, As, Fe, and Mn increased significantly above the geochemical baseline.
The rise in Cl, NO3, SO4, and Mn appears to be related to the combustion of organic matter. High concentrations
of Al and Fe, along with increased turbidity and low electrical conductivity during periods of heavier rainfall,
suggest these elements may be linked to sediment transport into watercourses following vegetation loss.
In the second hydrological year, most watercourses returned to normal levels compared to their geochemical baselines.
However, in watercourses within basins dominated by large agricultural areas, concentrations of NO3 and
As remained above baseline values, suggesting a partial association with agricultural activities (translated).
View more (in Portuguese)
2020
Sequeira, M.D., Castilho, A., Dinis, P. & Tavares, A.O. (2020). Impact Assessment and Geochemical
Background Analysis of Surface Water Quality of Catchments Affected by the 2017 Portugal Wildfires. Water, 12(10), 2742.
In October 2017, the Mondego hydrological basin was devastated by multiple wildfires. To understand the
impacts that these had on surface water quality, monthly monitoring campaigns were implemented in the affected
catchments. The campaigns oversaw the water’s physical characteristics and major, minor and trace constituents.
Analysis of major changes was performed, as well as comparisons with geochemical backgrounds, determined using
publicly available data collected prior to the fires. The backgrounds allowed us to verify which water parameters
were most influenced by the fires. Wildfires were responsible for increasing turbidity on all watercourses, and
electrical conductivity increased in watercourses with flatter, granitoid/sedimentary-dominated watersheds. Cl−,
NO3−, and SO42− surpassed background values in most monitored basins. Changes in Al, Fe, Mn, As, Ba, and Zn
concentrations were observed in all watercourses after the wildfires and decreases after intense rainfall.
Background values were particularly exceeded for Al in all monitoring points and As in basins with extensive
agricultural areas. Burnt plant material and organic matter partially account for the increases in Cl−, NO3−,
SO42−, Al, As, Fe, and Mn content. High Al, Fe and Zn with low water conductivity suggests that these elements
were associated with sediment loads after the removal of vegetation.
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Water: IF: 2.069; Q2: Water Science and Technology; H Index: 42
Sequeira, M.D., Castilho, A., Dinis, P. & Tavares, A.O. (2020). Study of superficial waters
quality in a post-wildfire scenario in Portugal Central Region. Comunicações Geológicas, 107, 133-136.
Following the major wildfires that affected the Central region of Portugal in 2017, a watercourse monitoring campaign was
initiated in November 2017 to determine changes in water proprieties in a post-fire scenario, and establish the persistence
of these effects. In the Mondego River basin, 10 points, from 6 watercourses, were chosen based on the size of the watershed
and the percentage of burnt area. Monthly water monitorization featured in situ parameters and major ions analysis. A higher
electrical conductivity was found in water in November 2017, before the first runoffs. Major ions have, in generally, decreased
from December to January. However, the Cavalos brook showed an increase in NO3 concentration, and the downstream of Mondego
River showing increase in Ca, HCO3 and NO3.
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Comunicações Geológicas: IF: 1.000; Q3: Environmental Science; H Index: 13
Dinis, P., Sequeira, M.D., Tavares, A.O., Carvalho, J., Castilho, A.M. & Pinto, M.M. (2020).
Post-wildfire denudation assessed from compositional features of river sediments (Central Portugal). Applied Clay Science, 193, 105675.
The wildfires of 2017 were responsible for vegetation clearance in a wide area of central Portugal,
leaving the weathering profiles more exposed to erosive action. In the present research, suspended loads
from a set of catchment areas affected by these fires with diverse geological and orographic features
were periodically sampled to evaluate spatial and seasonal variability in sediment production. Bulk
mineralogy reflected the geology of the source areas, but displayed high variability even for a single
sampling site, which can be partially linked to the grain-size control on sediment composition.
Clay mineralogy provided a better picture of the denudation at catchment scale. The predominance
of detrital illite with low I5/I10 (ratio of the intensities at 5 Å (002) and 10 Å (001)) indicated
very shallow weathering profiles. Chlorite was usually the second most common mineral, more common
in metasedimentary-derived sediments, whilst kaolinite was detected only in less steep catchment
areas with a predominance of granitic basement rocks or where previous-cycle depositional units
are also present. Year-long shifts in clay assemblages were attributed to different spatial
patterns of denudation. A depletion of kaolinite occurred in sampling sites mainly sourced by
granitoids. An opposite trend was observed where areas with Meso-Cenozoic deposits, less affected
by the wildfires than those with basement units, occupy significant proportions of the drainage
basins. This trend was ascribed to the wearing out of the weathering profiles covering the basement.
Regolith denudation was also testified by a progressive decrease in I5/I10. Shifts in clay mineralogy
linked with progressive surface denudation were found to be limited in areas with shallow soils,
but may complicate any paleoenvironmental reconstructions based on sediment composition when more
evolved weathering profiles have been eroded.
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Appl. Clay Sci.: IF: 4.180; Q1: Geology; H Index: 109
Sequeira, M.D., Castilho, A., Tavares, A.O. & Dinis, P. (2020). Assessment of superficial
water quality of small catchment basins affected by portuguese rural fires of 2017. Ecological Indicators, 111, 105961.
In October of 2017 a series of rural fires affected Portugal’s Central Region, leading to the destruction
of 40–60% of the forest area in some districts. A monitoring program was initiated in 5 catchments of the
Mondego drainage basin, in order to understand the temporal evolution of the water’s physical and chemical
characteristics in a post-fire scenario. This monitoring program was implemented in catchments with sizes
between 20 km2 and 160 km2 in areas 60%–99% burnt. For each catchment a gauging point was selected near the
mouth of the river. These 5 gauging points were assessed monthly, starting one month after the fire, in
November 2017, and ending in June 2018. In each campaign stream water was sampled for laboratory analysis
and in-situ physical-chemical proprieties were measured. Major ions in water samples were determined through
ion chromatography (IC) and molecular absorption spectroscopy, and inductively coupled plasma optical emission
spectrometry (ICP-OES). Trace elements were evaluated through ICP-OES and inductively coupled plasma mass
spectrometry. Total organic carbon and dissolved organic carbon were evaluated through the oxidation method
and polycyclic aromatic hydrocarbons were determined by high-performance liquid chromatography. The data
collected was crossed with the catchment’s morphometric, geological and land use data, including characteristics
of the burnt area. Results showed that these fires affected the surface waters in the studied catchments,
producing an increase in turbidity, and in the concentrations of Al, Fe, Mn and possibly NO3 and As.
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Ecol. Indicators: IF: 4.800; Q1: Ecology; H Index: 97
2019
Sequeira, M.D., Tavares, A.O., Castilho, A., & Dinis, P. (2019). Monitorização de cursos
de água em cenário de pós-incêndio: Lições do projeto Risk AquaSoil. CESContexto, 25, 21–32.
The 2017 wildfires that affected the Central Region of Portugal caused environmental, social, economic,
and institutional impacts. One of the recognized post-event effects was on the properties of surface waters.
This observation led to a watercourse monitoring campaign to determine changes in water properties, within
the scope of the INTERREG Risk AquaSoil project. For this purpose, 10 monitoring points were selected in the
Mondego River Basin, specifically along 6 watercourses, based on the size of the drainage basin and the percentage
of burned area. Monthly monitoring included in situ analysis of physico-chemical parameters and the determination
of major and minor ions, trace elements, dissolved gases, and other compounds. The results show an increase in
water turbidity, associated with the presence of ash and sediments; the introduction of Al (aluminum),
Fe (iron), and Si (silicon) through erosion processes; and As (arsenic) via transport by surface runoff.
All watercourses showed turbidity values above the legal threshold for public consumption, and some pH
values were below the established limits. Regarding metal concentrations, the Mondego River and Ribeira
de Cavalos showed levels above the legal standards for human consumption (translated).
View more (in Portuguese)
Areia, N.P., Intrigliolo, D., Tavares, A., Mendes, J. M., & Sequeira, M.D. (2019). The role
of media between expert and lay knowledge: A study of Iberian media coverage on climate change. Science of The Total Environment, 682, 291-300.
Individuals play a crucial role in combating climate change, but high levels of acknowledgment
and engagement are needed to lead to changes toward more sustainable behaviours. In this aspect,
media plays an important role in shaping individuals' awareness about climate change. This study
aims to analyse Iberian media coverage about climate change to further discuss its influence on
the public's engagement with the subject. A total of 449 news were collected from Iberian newspapers.
Their characteristics were analysed through quantitative content analysis. Data shows important journalistic
bias toward a national framing, mainly focusing on drought and its impact on agriculture. The debate is
focused on technological and political discourses. The gaps found on the Iberian media coverage may contribute
to public's low levels of acknowledgement and engagement, not enhancing the possibility of change in
individuals' behaviours for more sustainable actions.
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Sci. Total Envi.: IF: 6.551; Q1: Env. Chemistry; H Index: 205
2018
Areia, N. P., Sequeira, M. D., Mendes, J. M. & Tavares, A. O. (2018). Portuguese literacy
about climate change - An online media coverage study. 8th ICBR Proceedings.
Dinis, P., Sequeira, M. D., Tavares, A. & Castilho, A. (2018). Monitoring shifts in
sediment composition following the Central Portugal wildfires of 2017. Proceedings of the IX Symposium on the Iberian Atlantic Margin, 149-150.
Following the major wildfires that affected the Central region of Portugal in 2017, an environmental
monitoring campaign was initiated in November of 2017. Among other environmental issues, the program
aims to understand the shifts in sediment production. Mineralogical data obtained so far indicate
a progressive decrease in kaolinite and increase in feldspar contents in most sampling sites.
These trends point to a strong erosion in the areas affected by the wildfires during the high
rainfall events of late 2017 and early 2018.
Sequeira, M. D., Castilho, A., Dinis, P., Tavares, A. O. (2018). Study of superficial waters quality
in a post-wildfire scenario in Portugal Central Region. Vulcânica (2), 419-420.
The Portuguese Central Region was affected, in 2017, by major series of wildfires that contributed
to the largest burnet area of the last 10 years. After a wildfire, the loss of vegetation might lead
directly to soil erosion and subsequently contamination of superficial water. The reduction, or elimination,
of the vegetative cover diminishes evapotranspiration and rain drop’s interception, exposing soil
and increasing run-off, which associated with a decreased rugosity, due to the loss of organic matter
and soil debris, increases its erodibility. During the combustion phase, condensation of volatile
organic compounds in sublayers of the soil might lead to a hydrophobic soil. With the first rains it
is expected an increase in run-off which introduces sediments, ashes and other debris in the watercourses,
leading to an increase in turbidity, and diminished dissolved oxygen. Ashes transported by the
run-off carry nitrates and phosphates leading to an increased content of algae and water eutrophication.
The combustion of bioaccumulating species could lead to elevated concentrations of metals and
metalloids, dangerous for their toxicity and persistence. During a wildfire, polycyclic aromatic
hydrocarbon (PAH) could be formed, despite their insoluble nature, these can be found on soil or
watershed sediments, and pose a major concern due to their cancerogenic effects. To compare water
proprieties before and after the first run-offs and the water quality in subsequently months,
understanding what are the effects of the run-off in a post-fire scenario, and, if any, determine
the persistence of these same effects, a watercourse monitoring campaign was initiated in November
of 2017 in the Mondego River basin, which was affected with approximately 30% of burnt area.
For this, 10 monitoring points, from 6 watercourses, were chosen based on the size of the watershed
and the percentage of burnt area. The monthly water monitorization feature in situ analysis and
laboratory analysis of major anions, major and metallic cations, Total Organic Carbon (TOC),
Dissolved Organic Carbon (DOC) and PAHs. Due to their close relation between suspended sediments
and water characteristics and composition, a mineralogical analysis for these was also considered,
as well as a chemical and granulometric analysis in some cases. Bottom sediments are collected in
the beginning and the end of the major pluviosity period, and submitted to a granulometry and
mineralogic analysis, to perceive changes in erosion and transport of watercourses. Data obtained
so far shown a higher electric conductivity in the November, which could be associated with ashes
presence in the water, before the first run-offs, with a decreasing trend in the next months. This
is also supported in the lower pH values, in December, and a return to values similar to November,
in January. Most of the monitoring points have shown a decrease in concentration of Cl, Na, K, Mg,
Ca and SO4 from December to January, which might be related to a high mineralized run-off. Also,
the majority of the waters of the monitoring points changed their hydrochemical facies, for the
same time period, with a decrease in their chlorinate content.
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2017
Gomes, E. M., Silva, M. M. V., Sequeira, M., & Lopes, F. C. (2017). Representação de
rochas graníticas em cartas geológicas de Portugal, do século XIX à atualidade: o exemplo dos granitoides pré-variscos da Região Centro.
Memorias de la Real Sociedad Española de Historia Natural, (14), 225-244
Age determination and the petrogenesis of the granitic rocks of Portugal, especially of the
north and center, have been subjects of research and debate by groups of geologists, mainly in the
last decades of the 20th century. First, they were considered as a single intrusion, which was
reflected in the geological maps of Portugal, where all the granitoids were represented by the
same symbol. Reflecting the advances in the methods of radiometric dating and in the geological
knowledge, it is recognized today a range of ages to the granitoid rocks of northern and central
Portugal going from the Neoproterozoic to the late Paleozoic times. As examples of these studies,
we considered the granitic and gneissic rocks outcrop in the center of Portugal, in the region between
Coimbra and Nisa, in the vicinity of two firstorder tectonic accidents: the Porto-Tomar-Ferreira do
Alentejo shear zone (ZCPTFA) and the Tomar-Badajoz-Cordoba shear zone (ZCTBC). These structures
represent a border between two geotectonic zones of the Iberian Massif: the Central Iberian Zone
(ZCI) and the Ossa Morena Zone (ZOM). The aim of this study was to sketch the evolution of the
representation of these granitic and gneissic bodies in the geological maps of Portugal, scales
1:500.000 and 1:1.000.000, from the nineteenth century to the present day, and compare this representation
with the advances of geological knowledge. Granites and gneisses, in the geological maps at 1:1.000.000
scale, are included in large groups and it is not possible to distinguish the different bodies in respect
to its nature and age, with only some differentiation for the gneisses represented in the 2010 edition.
This distinction is achieved in the geological maps at 1:500.000 scale, especially, in the 1972 and 1992
editions. The evolution of the cartographic representation and maps legends reflect the advancement in
the application of K-Ar and Rb-Sr radiometric methods of dating, in the eighties and nineties of the
20th century, and U-Pb dating in early years of the 21st century. It also points out the advances in
petrography and geochemistry, which are also crucial to the edition of numerous geological maps of
Portugal, at a scale of 1:50.000. According to the available data, these rocks represent evidence of
magmatism during Neoproterozoic and Cambric-Ordovician times. It is concluded that there are significant
mismatches between the recent geological knowledge and the representation of these rocks in the last
editions of the geological maps of Portugal, thus justifying new maps editions, in particular, at a scale
of 1:500.000.
View more (in Portuguese)
Mem. Real Sociedad Española de Historia Natural: IF: 0.201; Q2: Earth and Planetary Sciences; H Index: 10
Gomes, E. M., Silva, M. M. V., Sequeira, M., & Lopes, F. C. (2017).Representação de rochas graníticas pré-variscas, aflorantes na proximidade do limite ZCI-ZOM,
no setor entre Coimbra e Nisa, em cartas geológicas de Portugal, do século XIX à atualidade. Livro de Resunoms da XII Bienal da Real
Sociedad Española de Historia Natural, 94-95
As rochas graníticas pré-variscas, aflorantes em território português, no limite da Zona Centro Ibérica (ZCI) com a Zona de
Ossa Morena (ZOM), têm constituído objeto de estudo e debate por várias “gerações” de geólogos, não existindo, até hoje, consenso
alargado relativamente à idade e enquadramento geotectónico da maioria dos corpos graníticos e gnaissicos que afloram ao longo
deste limite e na sua proximidade. Pretende- se, com este estudo, traçar a evolução da sua representação cartográfica em cartas
geológicas de Portugal, do século XIX até à atualidade, e confrontá-la com a evolução do conhecimento geológico. O estudo
focaliza- se na análise da Carta Geológica de Portugal, à escala 1:500.000, edições de 1876, 1899, 1972 e 1992, e na Carta
Geológica de Portugal, à escala 1:1.000.000, edições de 1952, 1968 e 2010. O estudo incidiu nos corpos graníticos aflorantes
na ZCI e nos gnaisses da ZOM. As edições das Cartas Geológicas de Portugal do século XIX são caracterizadas pela ausência de
diferenciação dos corpos graníticos e gnaissicos, pois a sua representação tinha como base, essencialmente, o trabalho de
campo. O mesmo se aplica à edição da Carta Geológica 1:1.000.000, de 1952. Estudos petrográficos de pormenor são notórios na
edição de 1972, enquanto as edições de 1992 e 2010 refletem a utilização de metodologias analíticas mais avançadas, como a
microssonda eletrónica e os métodos de datação radiométrica K-Ar e Rb-Sr, principalmente nos anos 70 e 80 do século XX. Na
ZCI, os granitos aflorantes a sul da falha da Lousã, Vila Nova, Coentral, Figueiró dos Vinhos, Pedrogão Grande e Bouçã, são
representados, na edição de 1972, como “granitos nordmarquíticos hercínicos”, enquanto na edição de 1992 são considerados
como “ortognaisses, às vezes ocelados, ante-hercínicos”. Na carta de 1968 são referidos como “rochas eruptivas hercínicas”
e na edição de 2010, estes granitos são identificados pela legenda “ortognaisses, granitos e dioritos deformados”, sendo
considerados pré-orogénicos, relativamente ao ciclo varisco, com um intervalo de idades de 490-470 Ma. Datações radiométricas
realizadas pelo método K-Ar (Pereira & Macedo, 1983; Gomes et al., 1991) e U-Pb (Reis et al., 2010) indicam a implantação
destes granitos no final do Neoproterozoico, destacando-se uma idade U-Pb de 542,2±0,8 para o zircão do granito de Vila Nova
e de 542±4 Ma (não publicado) para a monazite do granito de Coentral. Outros corpos graníticos, no limite SW da ZCI, incluem
o lacólito de Mação-Penhascoso e o maciço de Belver-Gavião. Relativamente ao primeiro, a legenda é idêntica à dos granitos
existentes mais a norte, em todas as edições, exceto na carta de 1992, onde é considerado prévarisco, sendo assinalado como
“ortognaisses e granitos do Ordovícico”. Abranches & Canilho (1981-82) referem uma idade Rb/Sr de 402 ±15 Ma e
Romão et al. (2010) mencionam uma idade U-Pb do zircão de ca. 483 Ma. Do maciço granítico de Belver-Gavião não se
conhecem datações radiométricas. Possui legenda idêntica ao anterior, nas cartas à escala 1:1.000.000, mas distingue-
se nas cartas de 1972 e 1992, sendo considerado “hercínico pós-estefaniano” e “tardi-hercínico”, respetivamente. Na ZOM,
distinguem-se os gnaisses de Arega, Beco, Sardoal, Carvalhal, Souto e Olalhas, identificados como “Precâmbrico xisto-arenito-porfiroide”,
na carta de 1972, e “gnaisses tonalíticos do Proterozoico médio”, na carta de 1992. A carta de 2010 atribui estes gnaisses ao
Neoproterozoico, mas não diferencia os gnaisses de Arega e Beco da Série Negra. Mendes (1967-68) apresenta uma idade Rb/Sr de
508 Ma para os gnaisses de Arega. Segundo Pereira (1987), idades K-Ar no intervalo 440-305 Ma, para Arega e Beco, traduzem
reestruturação varisca. Idades U-Pb ediacáricas para os ortognaisses do Carvalhal e do Sardoal, 569±3 Ma e 548±4 Ma,
respetivamente, são indicadas por Henriques et al. (2015). As cartas analisadas mostram uma evolução nas idades atribuídas
aos corpos graníticos, na área selecionada, de idades variscas para antevariscas paleozoicas. No entanto, estudos mais
recentes, indicam que os granitos a sul da falha da Lousã intruíram o Grupo das Beiras no final do Neoproterozoico. Estas
idades aproximam-se das idades dos ortognaisses da ZOM. No entanto, é relevante a ausência de estudos geoquímicos e isotópicos
recentes nos gnaisses das regiões de Arega e Beco.
2014
Volpe1, L., Garcia, A., Pereira Gómez, M. D., Sequeira, M., Török, Á., Vattai, A., Vaccaro, C. (2014). Study of
conservative conditions of “El patio de Escuela Menores” (Salamanca, Spain). VIII Congresso Nazionale di Archeometria
2013
Sequeira, M. D. (2013). Contaminação Ambiental Associada à Antiga Exploração Aurífera da Escádia Grande [Master thesis, University of Coimbra]
The old Escádia Grande gold mine, located in the Góis region, was exploited during the roman
occupation in the Iberian Peninsula, and again between 1939 and 1952, having been abandoned ever since.
The area is predominantly constituted by the “Complexo Xisto Grauvaquico” (CXG), consisting of phyllites
and metagraywackes, with intrusions of stockwork type veins that where explored. The mine has four entrances
to the galleries that are sealed, with drains at the bottom that pour mining drainage, as well as two
tailing occupying a total area of 25,000 m2, which are a mixed of the sterile material and the discarded
materials from the process of ore treatment. The presented study describes and evaluates the environmental
changes that have been generated by the mining activity and its abandonment in terms of water, stream
sediments and soils. The waters that travel through the mining area show a contamination that extends up
to 1.5 km South, with high levels of As, Cu, Pb and SO4, associated with a decrease in pH and an increase
in electrical conductivity. Due to the low pH values, and high concentrations of arsenic and nickel, the
water becomes unfit for human consumption, being, however, acceptable for irrigation. The stream sediments
are under the direct influence of the mine, presenting high geoaccumulation indexes of Ag, As, Au, Fe, Pb,
Sb and Zn, being the highest preoccupation the water line that crosses the mining area, with high
geoaccumulation of arsenic, antimony, silver and gold, occurring smaller contaminations of lead, iron and zinc.
The mining area and mineralized veins area present, generally, acid soils with low electric conductivity.
The Southern tailings causes, in the surrounding soils, an increase in concentrations of As, Au, Cu, Mn, Ni,
Pb, Sb and Zn, being the main focus of soil contamination. The Northern tailings causes an increase of Cu
and Ni concentrations in the nearby soils. While the mineralized veins increase the concentrations of Ag,
Au and Sb.
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