Papers by Armando L S Rocha
ABSTRACT The Santa Eulália Plutonic Complex (SEPC) is a calc-alkaline granitic body, with an area... more ABSTRACT The Santa Eulália Plutonic Complex (SEPC) is a calc-alkaline granitic body, with an area of 400 km2, and is located in the north of the Ossa Morena Zone of the Variscan Iberian sector, near the limit with the Central Iberian Zone. SEPC is considered late-Variscan because it cross-cuts the regional variscan structures. The host rocks are metamorphic formations from Upper Proterozoic to Lower Paleozoic. The SEPC has two main granitic facies with different compositions and textures. From the rim to the core, there is a medium-to coarse-grained pink granite (G0), which involves large elongated masses of mafic to intermediate rocks (M); and a central grey monzonitic granite (G1) which presents a dominant medium granular facies, and also a slight porphyritic texture close to G0. AMS and IRM studies were conducted to characterise these rocks, from 61 sampling sites: 29 in G0, 27 in G1 and 5 in M. The Km values range between 41.6 and 7343.7 x 10-6 SI in granitic rocks: G0, with Km > 10-3 SI (mean: 1357.4 x 10-6 SI) which supports the presence of magnetite, and G1 with Km< 10-4 SI (mean: 97.0 x 10-6 SI). In M, Km values are homogeneous with a mean of 620.9 x 10-6 SI. The magnetic anisotropy (P%) and the ellipsoid shape (T) were only determined in granites. The mean values of P% are 6.2% and 3.1% in G0 and G1, respectively. T shows the strongest oblate ellipsoids in central G1 (mean: 0.365) and slightly oblate in G0 (mean: 0.099). The magnetic foliations are subvertical ENE-WSW-striking in G0 and G1. Magnetic lineations are subvertical in G0 and moderately plunge to the SE in G1.The saturation IRM (SIRM) mean values are 9.345 A/m in G0, 0.027 A/m in G1 and 2.634 A/m in M. In G0 and M, the IRM acquisition curves show saturation between 0.3 and 0.4 T, followed by a small increase in increasing fields, suggesting that the main carrier of remanence is low magnetite or Ti-magnetite. In G1, the acquisition curves demonstrate paramagnetic and antiferromagnetic fractions, but a small magnetite fraction can also be present. SIRM/K have mean values of 7.119 kA/m, 0.298 kA/m and 3.425 kA/m for Go, G1 and M, respectively. The AMS and SIRM data support that G0 and G1 have a distinct magnetic behaviour. G0 is controlled by a ferrimagnetic fraction. G1, with Km< 10-4 SI, shows a paramagnetic behaviour due to ferromagnesian minerals, such as biotite and ilmenite. In M, Km is typical of gabbros and granodiorites and is due to the high contents of ferromagnesian minerals. The magnetic behaviours of G0 and G1 suggest different redox conditions in the magma genesis. Magnetic anisotropy is higher in G0 due to the presence of magnetite, but microscope observations also show signs of a post-magmatic deformation in G0. Although magnetic foliations are subvertical ENE-WSW-striking in both granites, magnetic lineations are different. The differences reflect distinct redox processes at magmatic sources and different emplacement mechanisms of M, G0 and G1. Acknowledgements: PTDC/CTE-GIX/099447/2008 (FCT-Portugal,COMPETE/FEDER).
Preliminary studies of Anisotropy of Magnetic Susceptibility (AMS) were carried out in the Castel... more Preliminary studies of Anisotropy of Magnetic Susceptibility (AMS) were carried out in the Castelo Branco granite.
The magnetic susceptibility values characterize the difference between central facies and peripheric facies and are
due to the abundance of biotite and other ferromagnesian minerals such as cordierite in the peripheric facies. The high
magnetic anisotropy in the peripheric facies suggests a higher magma stretching in the border of the pluton. The
NNW-SSE magnetic foliations are parallel to the regional structures,which point out the role of the last ductile
Variscan deformation phase in the emplacement of this pluton. These magnetic foliations were developed in a
magmatic to submagmatic state as shown by the microstructures and the magnetic anisotropy values.
The main goal of this study was to quantify the magnetic fabric on rock samples of the upper subu... more The main goal of this study was to quantify the magnetic fabric on rock samples of the upper subunit of the
Conraria Formation, Silves Group, in the region of Coimbra. Studies of Anisotropy of Magnetic Susceptibility
(AMS) were carried out on 50 samples from 11 sites in order to characterise the magnetic fabric. The general
parallelism between an oblate fabric and stratification may indicate a combination between the primary
sedimentary arrangement and another one with origin in the diagenesis or even in components of earlier tectonic
origin.
Este estudo teve como objetivo principal apresentar exemplos que, sobretudo, pelo seu interesse g... more Este estudo teve como objetivo principal apresentar exemplos que, sobretudo, pelo seu interesse geomorfológico, constituem locais ímpares, no vale do rio Ceira, entre Coimbra e a Lousã. Os exemplos selecionados: 1) a Paisagem da Senhora da Candosa, marcada sobretudo pela atuação do rio Ceira, em que os quartzitos do Ordovícico do Maciço Hespérico, fortemente inclinados, se apresentam rasgados em vale profundo; 2) a secção do rio Ceira, em depressão, que se avista da Senhora da Candosa, 3) o Cabril do Ceira, onde o vale se apresenta encaixado nos quartzitos do Ordovício; 4) a discordância angular entre as unidades do Paleozoico e as do Cretácico da Bacia da Lousã; e 5) o sinclinal que deforma as unidades do Paleozoico, apresentam uma localização e acessibilidade adequadas e têm sido usados na construção de recursos, no âmbito do ensino das Geociências.
A importância científica de algumas das paisagens da cidade de Coimbra, Portugal Central, deve-se... more A importância científica de algumas das paisagens da cidade de Coimbra, Portugal Central, deve-se à singularidade das formas do relevo locais. Os objetivos gerais, deste estudo, foram selecionar os critérios de identificação e avaliação de "locais com interesse geomorfológico" (LIGs) no sentido de geomorphosites e revelar os LIGs selecionados, no âmbito das Cidades Educadoras. Os LIGs, como resultados de trabalhos de campo e da bibliografia e da cartografia, foram: 1) Penedo da Saudade; 2) Penedo da Meditação; 3) Miradouro do Vale do Inferno; 4) Colina do Polo I da Universidade de Coimbra; e 5) Vale do Mondego. Os principais critérios interrelacionados foram, a localização, a acessibilidade, a importância histórica, turística e cultural e, sobretudo, a adequação a estratégias e atividades educacionais.
The Santa Eulália Plutonic Complex (SEPC), located in the Ossa Morena Zone (south Portugal), is c... more The Santa Eulália Plutonic Complex (SEPC), located in the Ossa Morena Zone (south Portugal), is composed of a medium- to coarse-grained pink granite (G0-type) and a central grey
medium-grained biotite granite (G1-type). Available Rb–Sr data indicates an age of 290 Ma. An emplacement model for the SEPC is proposed, taking into account magnetic fabric, 2D gravity modelling and fluid inclusion planes studies. The G0 and G1 types demonstrate different magnetic behaviour: G0 is considered amagnetite-type granite and G1 is an ilmenite-type granite. The formation
of G0 required oxidized conditions related to the interaction ofmafic rocks with a felsicmagma. The 2D gravity modelling and subvertical magnetic lineations show that the feeder zone of the SEPC is located in the eastern part of the pluton, confirming the role of the Assumar and Messejana Variscan faults in the process of ascent and emplacement. The magma emplacement was controlled by ENE–WSW planar anisotropies related to the final brittle stages of the Variscan Orogeny. The emplacement of the two granites was almost synchronous as shown by their gradational contacts in the field. The magnetic fabric however suggests emplacement of the G0-type first, closely followed by emplacement of the G1-type, pushing the G0 laterally which becomes more anisotropic towards the margin. The G1-type
became flattened, acquiring a dome-like structure. The SEPC is a nested pluton with G0-type granite assuming a tabular flat shape and G1-type forming a rooted dome-like structure. After emplacement, SEPC recorded increments of the late Variscan stress field documented by fluid inclusion planes in quartz.
Soil is composed of different types of particles which are either natural or of anthropogenic ori... more Soil is composed of different types of particles which are either natural or of anthropogenic origin. Anthropogenic particles are often related to the presence of heavy metals and thus provide information on soil quality. Magnetic parameters can detect the presence of such particles and may be used as a proxy for environmental pollution. This study explores the relationships
between magnetic particles and the nematofauna of agricultural soils. Magnetic, pedological, microscopy and nematological analyses were conducted in soils collected from major regions of potato production in Portugal. The magnetic characterisation of soils identified regions with magnetic particles with possible anthropogenic origin. Microscopy analysis revealed the presence of spherical particles dominantly composed of Fe, O and C. A positive and significant relationship
was found between saturation isothermal remanent
magnetisation (SIRM) and mass-specific susceptibility (χ), confirming the importance the ferrimagnetic fraction to magnetic properties. The nematode communities were composed of nematodes belonging to four trophic groups (bacterial feeding, plant feeders, fungal feeders and omnivores/predators). The relationships between magnetic parameters and the nematodes showed that (1) S−25 has a linear correlation with number of nematodes per kilogram of soil and with plant feeders’ trophic group and (2) SIRM correlates with the bacterial feeders trophic group. This study reveals that magnetic proxies may provide means for detecting regions with higher levels of pollution, possibly related to heavy
metals. Due to the large background variability found in magnetic parameters, the sampling spacial mesh should to be further refined and the input of magnetic minerals needs to be locally calibrated.
Book chapters by Armando L S Rocha
Environmental magnetic methods have been particularly used since the 1980s. In this paper the goa... more Environmental magnetic methods have been particularly used since the 1980s. In this paper the goals are to present: magnetic methods; sampling and sample preparation methods; data
collection methods; data representation methods and the type of research problems that magnetic methods allow us to resolve. As conclusions, we note that magnetic methods are powerful in solving problems of current environments and paleoenvironments, especially in studies of pollution by
particles, in studies of evolution and pollution of soils and sediments and in studies of materials sources, such as in forensic studies. The magnetic parameters evaluated in various types of materials allow us to find the contribution of detrital ferrimagnetic materials, biological and anthropogenic in origin. The magnetic parameters determine the origin (the signature) of the materials, the size and the type of structure. For example, in studies of urban pollution, it is possible to construct the mapping of pollution, and know the origin of materials and magnetic parameters relating to the chemical composition. In soil studies, it is possible to sketch evolution models and contamination.
Teaching Documents by Armando L S Rocha
Para o desenvolvimento deste estudo foi seguido um plano de investigação quantitativo, não experi... more Para o desenvolvimento deste estudo foi seguido um plano de investigação quantitativo, não experimental, que envolveu 178 professores do grupo 520 a leccionar em 38 escolas. Os dados foram obtidos através de um questionário construído e validado no âmbito desta investigação. A análise factorial dos dados obtidos permitiu construir 4 dimensões: planificação, valorização, formação e motivação. A matriz de correlação de Pearson permitiu concluir que existem correlações positivas e estatisticamente significativas (p <0,01) entre as dimensões planificação, valorização e formação. Os resultados ANOVA e teste t de Student permitiram confirmar, pelo menos em parte, algumas das hipóteses previamente definidas.
Este estudo, sobre as concepções e as práticas dos professores, relativamente às aulas de campo n... more Este estudo, sobre as concepções e as práticas dos professores, relativamente às aulas de campo no
ensino da Geologia, foi desenvolvido segundo um plano de investigação quantitativo, não experimental, e envolveu 178 professores do grupo 520 a leccionar em 38 escolas de Portugal. Os dados foram obtidos através de um questionário construído e validado no âmbito desta investigação. A análise factorial dos dados obtidos permitiu construir 4 dimensões: planificação, valorização, formação e motivação. A leitura e
interpretação da matriz de correlação de Pearson permitiram concluir que existem correlações positivas e estatisticamente significativas.
Abstracts by Armando L S Rocha
The granite complex of Castelo Branco, central Portugal, is a zoned composite pluton constituted ... more The granite complex of Castelo Branco, central Portugal, is a zoned composite pluton constituted by a central facies of two-mica granite concentrically rounded by porphyritic two-mica granodiorites.
The Conraria Formation is the lower unit of the Grés de Silves Group (Silves Sandstones Group) of... more The Conraria Formation is the lower unit of the Grés de Silves Group (Silves Sandstones Group) of Upper Triassic age. It is the sum of two subunits which have mean thickness of 40 ± 5 m and 120 ± 15 m, respectively, in the Coimbra region.
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Papers by Armando L S Rocha
The magnetic susceptibility values characterize the difference between central facies and peripheric facies and are
due to the abundance of biotite and other ferromagnesian minerals such as cordierite in the peripheric facies. The high
magnetic anisotropy in the peripheric facies suggests a higher magma stretching in the border of the pluton. The
NNW-SSE magnetic foliations are parallel to the regional structures,which point out the role of the last ductile
Variscan deformation phase in the emplacement of this pluton. These magnetic foliations were developed in a
magmatic to submagmatic state as shown by the microstructures and the magnetic anisotropy values.
Conraria Formation, Silves Group, in the region of Coimbra. Studies of Anisotropy of Magnetic Susceptibility
(AMS) were carried out on 50 samples from 11 sites in order to characterise the magnetic fabric. The general
parallelism between an oblate fabric and stratification may indicate a combination between the primary
sedimentary arrangement and another one with origin in the diagenesis or even in components of earlier tectonic
origin.
medium-grained biotite granite (G1-type). Available Rb–Sr data indicates an age of 290 Ma. An emplacement model for the SEPC is proposed, taking into account magnetic fabric, 2D gravity modelling and fluid inclusion planes studies. The G0 and G1 types demonstrate different magnetic behaviour: G0 is considered amagnetite-type granite and G1 is an ilmenite-type granite. The formation
of G0 required oxidized conditions related to the interaction ofmafic rocks with a felsicmagma. The 2D gravity modelling and subvertical magnetic lineations show that the feeder zone of the SEPC is located in the eastern part of the pluton, confirming the role of the Assumar and Messejana Variscan faults in the process of ascent and emplacement. The magma emplacement was controlled by ENE–WSW planar anisotropies related to the final brittle stages of the Variscan Orogeny. The emplacement of the two granites was almost synchronous as shown by their gradational contacts in the field. The magnetic fabric however suggests emplacement of the G0-type first, closely followed by emplacement of the G1-type, pushing the G0 laterally which becomes more anisotropic towards the margin. The G1-type
became flattened, acquiring a dome-like structure. The SEPC is a nested pluton with G0-type granite assuming a tabular flat shape and G1-type forming a rooted dome-like structure. After emplacement, SEPC recorded increments of the late Variscan stress field documented by fluid inclusion planes in quartz.
between magnetic particles and the nematofauna of agricultural soils. Magnetic, pedological, microscopy and nematological analyses were conducted in soils collected from major regions of potato production in Portugal. The magnetic characterisation of soils identified regions with magnetic particles with possible anthropogenic origin. Microscopy analysis revealed the presence of spherical particles dominantly composed of Fe, O and C. A positive and significant relationship
was found between saturation isothermal remanent
magnetisation (SIRM) and mass-specific susceptibility (χ), confirming the importance the ferrimagnetic fraction to magnetic properties. The nematode communities were composed of nematodes belonging to four trophic groups (bacterial feeding, plant feeders, fungal feeders and omnivores/predators). The relationships between magnetic parameters and the nematodes showed that (1) S−25 has a linear correlation with number of nematodes per kilogram of soil and with plant feeders’ trophic group and (2) SIRM correlates with the bacterial feeders trophic group. This study reveals that magnetic proxies may provide means for detecting regions with higher levels of pollution, possibly related to heavy
metals. Due to the large background variability found in magnetic parameters, the sampling spacial mesh should to be further refined and the input of magnetic minerals needs to be locally calibrated.
Book chapters by Armando L S Rocha
collection methods; data representation methods and the type of research problems that magnetic methods allow us to resolve. As conclusions, we note that magnetic methods are powerful in solving problems of current environments and paleoenvironments, especially in studies of pollution by
particles, in studies of evolution and pollution of soils and sediments and in studies of materials sources, such as in forensic studies. The magnetic parameters evaluated in various types of materials allow us to find the contribution of detrital ferrimagnetic materials, biological and anthropogenic in origin. The magnetic parameters determine the origin (the signature) of the materials, the size and the type of structure. For example, in studies of urban pollution, it is possible to construct the mapping of pollution, and know the origin of materials and magnetic parameters relating to the chemical composition. In soil studies, it is possible to sketch evolution models and contamination.
Teaching Documents by Armando L S Rocha
ensino da Geologia, foi desenvolvido segundo um plano de investigação quantitativo, não experimental, e envolveu 178 professores do grupo 520 a leccionar em 38 escolas de Portugal. Os dados foram obtidos através de um questionário construído e validado no âmbito desta investigação. A análise factorial dos dados obtidos permitiu construir 4 dimensões: planificação, valorização, formação e motivação. A leitura e
interpretação da matriz de correlação de Pearson permitiram concluir que existem correlações positivas e estatisticamente significativas.
Abstracts by Armando L S Rocha
The magnetic susceptibility values characterize the difference between central facies and peripheric facies and are
due to the abundance of biotite and other ferromagnesian minerals such as cordierite in the peripheric facies. The high
magnetic anisotropy in the peripheric facies suggests a higher magma stretching in the border of the pluton. The
NNW-SSE magnetic foliations are parallel to the regional structures,which point out the role of the last ductile
Variscan deformation phase in the emplacement of this pluton. These magnetic foliations were developed in a
magmatic to submagmatic state as shown by the microstructures and the magnetic anisotropy values.
Conraria Formation, Silves Group, in the region of Coimbra. Studies of Anisotropy of Magnetic Susceptibility
(AMS) were carried out on 50 samples from 11 sites in order to characterise the magnetic fabric. The general
parallelism between an oblate fabric and stratification may indicate a combination between the primary
sedimentary arrangement and another one with origin in the diagenesis or even in components of earlier tectonic
origin.
medium-grained biotite granite (G1-type). Available Rb–Sr data indicates an age of 290 Ma. An emplacement model for the SEPC is proposed, taking into account magnetic fabric, 2D gravity modelling and fluid inclusion planes studies. The G0 and G1 types demonstrate different magnetic behaviour: G0 is considered amagnetite-type granite and G1 is an ilmenite-type granite. The formation
of G0 required oxidized conditions related to the interaction ofmafic rocks with a felsicmagma. The 2D gravity modelling and subvertical magnetic lineations show that the feeder zone of the SEPC is located in the eastern part of the pluton, confirming the role of the Assumar and Messejana Variscan faults in the process of ascent and emplacement. The magma emplacement was controlled by ENE–WSW planar anisotropies related to the final brittle stages of the Variscan Orogeny. The emplacement of the two granites was almost synchronous as shown by their gradational contacts in the field. The magnetic fabric however suggests emplacement of the G0-type first, closely followed by emplacement of the G1-type, pushing the G0 laterally which becomes more anisotropic towards the margin. The G1-type
became flattened, acquiring a dome-like structure. The SEPC is a nested pluton with G0-type granite assuming a tabular flat shape and G1-type forming a rooted dome-like structure. After emplacement, SEPC recorded increments of the late Variscan stress field documented by fluid inclusion planes in quartz.
between magnetic particles and the nematofauna of agricultural soils. Magnetic, pedological, microscopy and nematological analyses were conducted in soils collected from major regions of potato production in Portugal. The magnetic characterisation of soils identified regions with magnetic particles with possible anthropogenic origin. Microscopy analysis revealed the presence of spherical particles dominantly composed of Fe, O and C. A positive and significant relationship
was found between saturation isothermal remanent
magnetisation (SIRM) and mass-specific susceptibility (χ), confirming the importance the ferrimagnetic fraction to magnetic properties. The nematode communities were composed of nematodes belonging to four trophic groups (bacterial feeding, plant feeders, fungal feeders and omnivores/predators). The relationships between magnetic parameters and the nematodes showed that (1) S−25 has a linear correlation with number of nematodes per kilogram of soil and with plant feeders’ trophic group and (2) SIRM correlates with the bacterial feeders trophic group. This study reveals that magnetic proxies may provide means for detecting regions with higher levels of pollution, possibly related to heavy
metals. Due to the large background variability found in magnetic parameters, the sampling spacial mesh should to be further refined and the input of magnetic minerals needs to be locally calibrated.
collection methods; data representation methods and the type of research problems that magnetic methods allow us to resolve. As conclusions, we note that magnetic methods are powerful in solving problems of current environments and paleoenvironments, especially in studies of pollution by
particles, in studies of evolution and pollution of soils and sediments and in studies of materials sources, such as in forensic studies. The magnetic parameters evaluated in various types of materials allow us to find the contribution of detrital ferrimagnetic materials, biological and anthropogenic in origin. The magnetic parameters determine the origin (the signature) of the materials, the size and the type of structure. For example, in studies of urban pollution, it is possible to construct the mapping of pollution, and know the origin of materials and magnetic parameters relating to the chemical composition. In soil studies, it is possible to sketch evolution models and contamination.
ensino da Geologia, foi desenvolvido segundo um plano de investigação quantitativo, não experimental, e envolveu 178 professores do grupo 520 a leccionar em 38 escolas de Portugal. Os dados foram obtidos através de um questionário construído e validado no âmbito desta investigação. A análise factorial dos dados obtidos permitiu construir 4 dimensões: planificação, valorização, formação e motivação. A leitura e
interpretação da matriz de correlação de Pearson permitiram concluir que existem correlações positivas e estatisticamente significativas.