Frederico Borges | Universidade do Porto (original) (raw)

Uploads

Papers by Frederico Borges

Journal of Structural Geology, 1980

... 143–170. Abstract | PDF (1547 K) | View Record in Scopus | Cited By in Scopus (68). S. White,... more ... 143–170. Abstract | PDF (1547 K) | View Record in Scopus | Cited By in Scopus (68). S. White, Grain size and subgrain size variations across a shear zone, Contrib. Mineral. Petrol. 70 (1979), pp. 193–202. ... Soc. franc. Mineral. Crist. 81 (1958), pp. 223–226. ...

The results of studies concerning the geo1ogic, geomorphologic, tectonic and hydrogeologic featur... more The results of studies concerning the geo1ogic, geomorphologic, tectonic and hydrogeologic features of Caldas do Moledo (Peso da Régua, Northern Portugal) hydromineral system are presented. The geo1ogical and structural study inc1uded the survey of struc-tura1 discontinuities and tectonic 1ineaments. A major granitic outcrop was identified and mapped (Cidade1he granite). An hydrogeo1ogic inventory was performed. The study of the hydrodinamic features of the discharge zone was carried out based on the results of several well flow tests. The hydrogeochemieal characterisation inc1uded the major ion and the 18 0, 2H, 3H and 14C contents. An hydrogeologic conceptual mode1 concerning, mainly, the hydromineral circu1ation is proposed.

The gold mineralizations of the Dúrico-Beirão mining district (North Portugal) are separated into... more The gold mineralizations of the Dúrico-Beirão mining district (North Portugal) are separated into two types: Sb-Au and Au-As , and two gold-poor types: Pb-Zn-(Ag) and W-Sn. The Au-As type deposits underwent an important litostratigraphical control by Lower Ordovician alternances along the eastern limb of the Valongo anticline. They are characterized by frequent lateral and vertical variations , by the presence of exhalative-sedimentary intercalations (black layers) , and by distal volcanogenic prints in the sediments. These black layers have a greater thickness in the eastern limb, with a very discrete presence in the nose, being absent in the western limb. A great part of the gold concentrates in these black layers, essentially in interbeded sub-concordant thin quartz "veins". Moreover, analytical data show that disseminated arsenopyrite and pyrite are gold-bearing.

Environmental Earth Sciences, 2010

High-mountain basins provide a source of valuable water resources. This paper presents hydrologic... more High-mountain basins provide a source of valuable water resources. This paper presents hydrological models for the evaluation of water resources in the highmountain Zêzere river basin in Serra da Estrela, Central Portugal. Models are solved with VISUAL BALAN v2.0, a code which performs daily water balances in the root zone, the unsaturated zone and the aquifer and requires a small number of parameters. A lumped hydrological model fails to fit measured stream flows. Its limitations are overcome by considering the dependence of the temperature and precipitation data with elevation and the spatial variability in hydrogeomorphological variables with nine sub-basins of uniform parameters. Model parameters are calibrated by fitting stream flow measurements in the Zêzere river. Computed stream flows are highly sensitive to soil thickness, whereas computed groundwater recharge is most sensitive to the interflow and percolation recession coefficients. Interflow is the main component of total runoff, ranging from 41 to 55% of annual precipitation. High interflows are favored by the steep relief of the basin, by the presence of a high permeability soil overlying the fractured low permeability granitic bedrock and by the extensive subhorizontal fracturing at shallow depths. Mean annual groundwater recharge ranges from 11 to 15% of annual precipitation. It has a significant uncertainty due to uncertainties in soil parameters. This methodology proves to be useful to handle the research difficulties regarding a complex mountain basin in a context of data scarcity.

Mineral Deposit Research: Meeting the Global Challenge, 2005

Preceeding the main Hercynian Au-As-Sb metallogenic hydrothermal event, metallic preconcentration... more Preceeding the main Hercynian Au-As-Sb metallogenic hydrothermal event, metallic preconcentrations (Au, Sb, Pb) occurred during the sedimentation of the Paleozoic, namely in the Precambrian (?) and/or Cambrian layers bearing volcanic prints, in the volcanosedimentary lower Ordovician and in the basal Carboniferous breccia. The most evident lithostratigraphic control in the Dúrico-Beirão mining district concerns the Au-As mineralization hosted by the Arenigian alternances along the Eastern limb of the Valongo Anticline, with important syn-diagenetic concentration of gold related to exhalative "black-layer" , with pyrite-arsenopyrite. Lithostratigraphic controls are not so evident for the Sb-Au mineralizations that occur west of the Western limb of the Valongo Anticline. Nevertheless, all the studied deposits are hosted by competent sequences, mainly conglomerates, arenites and pelites from the Precambrian (?) and/or Cambrian (Montalto Unit) with acid volcanic rocks intercalated in the base, and in some cases by the Carboniferous basal breccia (paleo-placer type).

Geofluids, 2003

Geochemical and isotopic studies have been undertaken to assess the origin of CO 2 -rich waters i... more Geochemical and isotopic studies have been undertaken to assess the origin of CO 2 -rich waters issuing in the northern part of Portugal. These solutions are hot (76°C) to cold (17°C) Na-HCO 3 mineral waters. The d 2 H and d 18 O signatures of the mineral waters reflect the influence of altitude on meteoric recharge. The lack of an 18 O-shift indicates there has been no high temperature water-rock interaction at depth, corroborating the results of several chemical geothermometers (reservoir temperature of about 120°C). The low 14 C activity (up to 9.9 pmC) measured in some of the cold CO 2 -rich mineral waters (total dissolved inorganic carbon) is incompatible with the presence of 3 H (from 1.7 to 4.1 TU) in those waters, which indicates relatively short subsurface circulation times. The d 13 C values of CO 2 gas and dissolved inorganic carbon range between )6& and )1& versus Vienna-Peedee Belemnite, indicating that the total carbon in the recharge waters is being diluted by larger quantities of CO 2 ( 14 C-free) introduced from deep-seated (upper mantle) sources, masking the 14 C-dating values. The differences in the 87 Sr/ 86 Sr ratios of the studied thermal and mineral waters seem to be caused by water-rock interaction with different granitic rocks. Chlorine isotope signatures ()0.4& < d 37 Cl < +0.4& versus standard mean ocean chloride) indicate that Cl in these waters could be derived from mixing of a small amount of igneous Cl from leaching of granitic rocks.

... Citation: Espinha Marques, J.; Duarte, JM; Constantino, AT; Martins, AA; Aguiar, C.; Rocha, F... more ... Citation: Espinha Marques, J.; Duarte, JM; Constantino, AT; Martins, AA; Aguiar, C.; Rocha, FT; Inácio, M.; Marques, JM; Chaminé, HI ... The study area (Manteigas – Nave de Santo António – Torre sector, Serra da Estrela Mountain, Central Portugal), presents specific geological ...

Jorge Espinha Marques1; José Manuel Marques2; José Martins Carvalho3; Javier Samper4; Paula M. Ca... more Jorge Espinha Marques1; José Manuel Marques2; José Martins Carvalho3; Javier Samper4; Paula M. Carrei-ra5; Paulo Emanuel Fonseca6, Fernando Monteiro Santos7, Hélder Chaminé3; Pedro Gabriel Almeida8; Rui Marques Moura1; Frederico Sodré Borges1; Ary ...

Journal of Structural Geology, 1980

... 143–170. Abstract | PDF (1547 K) | View Record in Scopus | Cited By in Scopus (68). S. White,... more ... 143–170. Abstract | PDF (1547 K) | View Record in Scopus | Cited By in Scopus (68). S. White, Grain size and subgrain size variations across a shear zone, Contrib. Mineral. Petrol. 70 (1979), pp. 193–202. ... Soc. franc. Mineral. Crist. 81 (1958), pp. 223–226. ...

The results of studies concerning the geo1ogic, geomorphologic, tectonic and hydrogeologic featur... more The results of studies concerning the geo1ogic, geomorphologic, tectonic and hydrogeologic features of Caldas do Moledo (Peso da Régua, Northern Portugal) hydromineral system are presented. The geo1ogical and structural study inc1uded the survey of struc-tura1 discontinuities and tectonic 1ineaments. A major granitic outcrop was identified and mapped (Cidade1he granite). An hydrogeo1ogic inventory was performed. The study of the hydrodinamic features of the discharge zone was carried out based on the results of several well flow tests. The hydrogeochemieal characterisation inc1uded the major ion and the 18 0, 2H, 3H and 14C contents. An hydrogeologic conceptual mode1 concerning, mainly, the hydromineral circu1ation is proposed.

The gold mineralizations of the Dúrico-Beirão mining district (North Portugal) are separated into... more The gold mineralizations of the Dúrico-Beirão mining district (North Portugal) are separated into two types: Sb-Au and Au-As , and two gold-poor types: Pb-Zn-(Ag) and W-Sn. The Au-As type deposits underwent an important litostratigraphical control by Lower Ordovician alternances along the eastern limb of the Valongo anticline. They are characterized by frequent lateral and vertical variations , by the presence of exhalative-sedimentary intercalations (black layers) , and by distal volcanogenic prints in the sediments. These black layers have a greater thickness in the eastern limb, with a very discrete presence in the nose, being absent in the western limb. A great part of the gold concentrates in these black layers, essentially in interbeded sub-concordant thin quartz "veins". Moreover, analytical data show that disseminated arsenopyrite and pyrite are gold-bearing.

Environmental Earth Sciences, 2010

High-mountain basins provide a source of valuable water resources. This paper presents hydrologic... more High-mountain basins provide a source of valuable water resources. This paper presents hydrological models for the evaluation of water resources in the highmountain Zêzere river basin in Serra da Estrela, Central Portugal. Models are solved with VISUAL BALAN v2.0, a code which performs daily water balances in the root zone, the unsaturated zone and the aquifer and requires a small number of parameters. A lumped hydrological model fails to fit measured stream flows. Its limitations are overcome by considering the dependence of the temperature and precipitation data with elevation and the spatial variability in hydrogeomorphological variables with nine sub-basins of uniform parameters. Model parameters are calibrated by fitting stream flow measurements in the Zêzere river. Computed stream flows are highly sensitive to soil thickness, whereas computed groundwater recharge is most sensitive to the interflow and percolation recession coefficients. Interflow is the main component of total runoff, ranging from 41 to 55% of annual precipitation. High interflows are favored by the steep relief of the basin, by the presence of a high permeability soil overlying the fractured low permeability granitic bedrock and by the extensive subhorizontal fracturing at shallow depths. Mean annual groundwater recharge ranges from 11 to 15% of annual precipitation. It has a significant uncertainty due to uncertainties in soil parameters. This methodology proves to be useful to handle the research difficulties regarding a complex mountain basin in a context of data scarcity.

Mineral Deposit Research: Meeting the Global Challenge, 2005

Preceeding the main Hercynian Au-As-Sb metallogenic hydrothermal event, metallic preconcentration... more Preceeding the main Hercynian Au-As-Sb metallogenic hydrothermal event, metallic preconcentrations (Au, Sb, Pb) occurred during the sedimentation of the Paleozoic, namely in the Precambrian (?) and/or Cambrian layers bearing volcanic prints, in the volcanosedimentary lower Ordovician and in the basal Carboniferous breccia. The most evident lithostratigraphic control in the Dúrico-Beirão mining district concerns the Au-As mineralization hosted by the Arenigian alternances along the Eastern limb of the Valongo Anticline, with important syn-diagenetic concentration of gold related to exhalative "black-layer" , with pyrite-arsenopyrite. Lithostratigraphic controls are not so evident for the Sb-Au mineralizations that occur west of the Western limb of the Valongo Anticline. Nevertheless, all the studied deposits are hosted by competent sequences, mainly conglomerates, arenites and pelites from the Precambrian (?) and/or Cambrian (Montalto Unit) with acid volcanic rocks intercalated in the base, and in some cases by the Carboniferous basal breccia (paleo-placer type).

Geofluids, 2003

Geochemical and isotopic studies have been undertaken to assess the origin of CO 2 -rich waters i... more Geochemical and isotopic studies have been undertaken to assess the origin of CO 2 -rich waters issuing in the northern part of Portugal. These solutions are hot (76°C) to cold (17°C) Na-HCO 3 mineral waters. The d 2 H and d 18 O signatures of the mineral waters reflect the influence of altitude on meteoric recharge. The lack of an 18 O-shift indicates there has been no high temperature water-rock interaction at depth, corroborating the results of several chemical geothermometers (reservoir temperature of about 120°C). The low 14 C activity (up to 9.9 pmC) measured in some of the cold CO 2 -rich mineral waters (total dissolved inorganic carbon) is incompatible with the presence of 3 H (from 1.7 to 4.1 TU) in those waters, which indicates relatively short subsurface circulation times. The d 13 C values of CO 2 gas and dissolved inorganic carbon range between )6& and )1& versus Vienna-Peedee Belemnite, indicating that the total carbon in the recharge waters is being diluted by larger quantities of CO 2 ( 14 C-free) introduced from deep-seated (upper mantle) sources, masking the 14 C-dating values. The differences in the 87 Sr/ 86 Sr ratios of the studied thermal and mineral waters seem to be caused by water-rock interaction with different granitic rocks. Chlorine isotope signatures ()0.4& < d 37 Cl < +0.4& versus standard mean ocean chloride) indicate that Cl in these waters could be derived from mixing of a small amount of igneous Cl from leaching of granitic rocks.

... Citation: Espinha Marques, J.; Duarte, JM; Constantino, AT; Martins, AA; Aguiar, C.; Rocha, F... more ... Citation: Espinha Marques, J.; Duarte, JM; Constantino, AT; Martins, AA; Aguiar, C.; Rocha, FT; Inácio, M.; Marques, JM; Chaminé, HI ... The study area (Manteigas – Nave de Santo António – Torre sector, Serra da Estrela Mountain, Central Portugal), presents specific geological ...

Jorge Espinha Marques1; José Manuel Marques2; José Martins Carvalho3; Javier Samper4; Paula M. Ca... more Jorge Espinha Marques1; José Manuel Marques2; José Martins Carvalho3; Javier Samper4; Paula M. Carrei-ra5; Paulo Emanuel Fonseca6, Fernando Monteiro Santos7, Hélder Chaminé3; Pedro Gabriel Almeida8; Rui Marques Moura1; Frederico Sodré Borges1; Ary ...