Close or not so close? Provenance studies of megalithic monuments from Alentejo (Portugal)

There has been a significant amount of studies about megalithic tombs conducted in the Alentejo region. However the geological provenance of monoliths used in the construction of those tombs usually was not a priority among researchers with rare exceptions (Dehn, Kalb and Vortisch, 1991; Boaventura, 2000). Recent studies of dolmens (Oliveira, 1997 and 2006; Gonçalves, 2003) refer only to a brief characterization of rocks, such as "granite or schist slabs", highlighting certain types if the geological stratum is identical or not to the stone blocks. On the other hand, when the type of raw material appears to be similar with the bedrock, it is common and empirically assumed its local provenance. With the aim of testing and expand the knowledge about the provenance of the slabs used in the construction of megalithic tombs, several lithic samples from dolmen slabs and outcrops in their surroundings were collected for analysis and comparison. The samples were characterized by petrographic studies in thin section as well with a geochemical analyses performed by XRF that gives major elements as well some trace elements. The dolmens tested for this project are located roughly between the northeast to west of the town of Monforte (Upper region of Alentejo, Portugal) and are named, from south to north, as Serrinha, Rabuje group (1 to 5), Geodésico de Besteiros 3 and Velho. The field work and petrographic studies revealed that the slabs are constituted mainly by several types of granitoids (gnaissic, red, white, tonalitic), amphibolites and mottled schist shale. The comparison of chemical analyses between slabs and selected outcrops revealed that the provenances are in most of the cases from the nearby geological stratum. In fact, major elements (e.g. MgO, SiO2, CaO) as well trace elements (e.g. Sr, Y, Zr, Nb) compositions are similar on slab samples and in rocks from the outcrops. If in terms of major elements a similarity was already expectable, or easier to obtain, the trace elements (namely immobile elements such as Y or Nb) compositions corroborated that slabs and geological bedrock were alike. The capstone slab that covers the dolmen of Rabuje 1 group does not belong to the nearby geological stratum. Nevertheless, a probable matching source-outcrop was located sampled and characterized in terms of geochemistry and petrograpphy and compared with the megalithic capstone. This work allowed a better characterization of the rocks used in megalithic tombs as well as corroborat a pragmatic attitude of Neolithic populations in the search of the appropriate slabs for construction as proposed previously (Boaventura, 2000). When available, the megalithic stones were likely collected from the nearby stratum and therefore the distances traveled were small (in situ or less than 1-2 km). Nevertheless, when the type of stone needed was not available in the vicinity (e.g fracturing provided only smaller stones) it would be necessary to travel longer distances, up to 8 km (Boaventura, 2000), as in the case of the dolmen of Rabuje 1. Boaventura, R. (2000) - A geologia das Antas de Rabuje (Monforte, Alentejo), Revista Portuguesa de Arquelogia. Vol. 3;2.pp-15-23. Dehn, W.; Kalb, P.; Vortich, W. (1991) - Geologisch-Petrographische Untersuchungen an Megalithgräbern Portugals. Madrider Mitteilungen, 32, p. 1-28. Oliveira, J. (1997) - Monumentos megalíticos da bacia hidrográfica do Rio Sever. Ibn Maruan. Castelo de Vide. Special Edition. Oliveira, J. (2006) – Património arqueológico da Coudelaria de Alter e as primeiras comunidades agropastoris. [Évora]: Colibri

Layered granitoids: Interaction between continental crust recycling processes and

In this paper, field, petrographic, mineralogical, geochemical and isotopic (Rb–Sr and Sm–Nd) information from three areas within the Évora Massif (Iberian Variscan Orogen) is presented and discussed aiming at to unravel the relationships between granitoids and units mapped as migmatites and also to evaluate the interplay between mantle and crustal derived magmas. One of the areas – Almansor – displays a well-developed compositional layering (concordant with the regional Variscan structure) which was considered, in previous works, as an alternation of leucosome and melanosome. In this study, the layering is described as intercalation of diatexites, weakly foliated granitoids and trondhjemitic veins. Diatexites have characteristics of crustal melts plus restitic material and, according to geochemical and isotopic evidence, result from anatexis of Ediacaran metasediments. Weakly foliated granitoids and trondhjemitic veins from Almansor have calc-alkaline signatures and may be related to each other by crystal fractionation processes; however, the mixing between mafic (mantle-derived) and felsic (diatexitic melt) magmas revealed by the isotopic data may also explain their genesis. In the Alto de São Bento area, several igneous lithologies (tonalites, granodiorites, porphyritic granites and leucogranites) are present and show typical isotropic igneous textures. Despite structural and textural differences, geochemical data support, for most rocks, an origin from the same calk-alkaline suite, also present at Almansor. The Alto de São Bento leucogranites have an isotopic signature that, although different from that obtained in the Almansor diatexites, is still compatible with an origin involving melting of Ediacaran metasediments; compositions, with very low contents of usually incompatible elements, flat normalized REE patterns and strong negative Eu anomalies, suggest that the anatectic melt has undergone crystal fractionation processes before reaching the composition of the leucogranite magma. The Almansor outcrop is then interpreted as the remnants of a shear zone that operated as a pathway for melts that moved upward through the crust providing the locus for differentiation and mingling/mixing of magmas, whilst Alto de São Bento would correspond to the zone, at a higher crustal level, where magmas were trapped and forced to spread horizontally. At Valverde (the third area) foliated and non-foliated granitoids are spatially related and field criteria links these rocks to metamorphic protolith and anatectic melt, respectively. However, petrographic, geochemical and isotopic information shows that they all are compositionally identical trondhjemites with no evidence of metamorphic fabric. In the foliated rocks, mesoscopic features are interpreted as resulting from melt segregation structures formed in a crystallizing mush. In contrast to the previous areas, the Valverde trondhjemites probably do not belong to the main calc-alkaline plutonic suite of the Évora Massif, since they have a distinct Sr and Nd isotope signature

Proveniência geológica dos esteios de antas no Freixo-Redondo e em Monforte, Centro-Sul de Portugal

O projeto geoarqueológico MEGAGEO relaciona a distribuição de antas com os seus materiais de construção e a paisagem geológica, nas áreas do Freixo-Redondo e em Monforte. Estas áreas apresentam contextos geológicos que permitem uma abordagem interdisciplinar de caracterização e proveniência de megálitos. A área do Freixo-Redondo é constituída por rochas metamórficas (gnaisses, micaxistos, filitos e metagrauvaques), que são intruídas pelo maciço ígneo do Redondo [2]. Este, corresponde a um corpo granodiorítico, com uma pequena intrusão de gabro/diorito e frequentes encraves de rochas encaixantes. As antas estão preferencialmente implantadas no substrato granodiorítico, em torno da intrusão de gabro/diorito, ou nos gnaisses encaixantes e são essencialmente constituídas por granodioritos. Destacam-se deste contexto as antas de Godinhos e Candeira, que se localizam mais a norte, na auréola de metamorfismo (gnaisses, xistos porfiroclásticos, micaxistos e granitos moscovíticos) e que são essencialmente constituídas por rochas metamórficas. A área de Monforte é caracterizada pelo granito de Monforte, que corresponde a um granito rosa de grão médio a grosseiro, que intrui e metamorfiza por contacto o encaixante formado por gneisses, metapelitos, anfibolitos, rochas carbonatadas e calcossilicatadas [1]. As antas estão implantadas quer no granito quer no encaixante e são constituídas por granito, gnaisses, rochas carbonatadas e corneanas calcossilicatadas. Em ambas as áreas foram recolhidos dados de natureza arqueológica e realizados levantamentos de campo, envolvendo a caracterização dos esteios e dos prováveis afloramentos de proveniência. Após recolha de amostras representativas dos esteios e dos prováveis afloramentos de proveniência, realizou-se análise petrográfica pelos métodos convencionais de microscopia de luz polarizada e análises semi-quantitativas por SEM-EDS. Por último, foi efetuada a caracterização geoquímica de todas as amostras envolvendo análises geoquímicas elementares (ICP-MS). Os resultados obtidos, permitiram de um modo geral relacionar esteios com os afloramentos selecionados e confirmar a proveniência dos esteios. Para a região do Freixo-Redondo obtiveram-se, em média, distâncias menores aos afloramentos quando comparado com a região de Monforte

Aspectos sobre os métodos de refração sísmica

Os métodos de interpretação de refração sísmica têm vindo a ser desenvolvidos ao longo dos anos em paralelo com o aumento da capacidade de cálculo numérico. Inicialmente, foi desenvolvido o método tempo de intercepção, seguido por outros métodos mais robustos. A refracção sísmica tem sido aplicada em diversas áreas, nomeadamente em engenharia civil, ambiente, prospecção de petróleo, e arqueologia. Neste artigo são avaliados os resultados obtidos por alguns métodos, nomeadamente, o método tempo de intercepção, Plus-Minus, GRM e tomografia sísmica. Demonstra-se que é possível aplicar todos os métodos, dependendo unicamente do grau de exigência do objectivo, que pode passar pelo nível de resolução, ter em conta ou não a variabilidade lateral de velocidade, ou o tempo de realização das tarefas tanto em campo e como no processamento. São ainda apresentadas as vantagens e desvantagens para cada método bem como alguns pormenores de processamento e técnicas de aquisição de dados no campo

One-year rehospitalisations for congestive heart failure in Portuguese NHS hospitals: a multilevel approach on patterns of use and contributing factors

Identification of rehospitalisations for heart failure and contributing factors flags health policy intervention opportunities designed to deliver care at a most effective and efficient level. Recognising that heart failure is a condition for which timely and appropriate outpatient care can potentially prevent the use of inpatient services, we aimed to determine to what extent comorbidities and material deprivation were predictive of 1 year heart failure specific rehospitalisation.info:eu-repo/semantics/publishedVersio

Building monument materials during the 3rd-4rd millennium (Portugal)

Dolmens are the most conspicuous remains of the populations of the 4th and first half of 3rd millennia BCE. These tombs are impressive not only for their monumentality, but also because of the socioeconomic investment they represent for those Neolithic communities, namely from the Central-South of Portugal, who built them. Although dolmens have been studied for their funerary content and typologies, an interdisciplinary approach toward the geological characterization and sourcing of stones used in these constructions has not received enough attention from researchers. With MEGAGEO project a multidisciplinary group of geologist and archaeologists intends to assess the relationship between the distribution of dolmens in Central-South Portugal, their source materials, and the geological landscape. GIS will map the information gathered and will be used to analyse these relationships. The selection of the areas, with distinctive geologies (limestone vs granite), will allow to verify if human patterns of behaviour regarding the selection of megaliths are similar or different regionally. Geologically the first target area (Freixo, Alentejo) is dominated by a small intrusion of gabbro mingled/mixed within a granodioritic intrusion both related with variscan orogeny. Granodiorite exhibit several enclaves of igneous and metamorphic nature attesting the interaction between both igneous rocks as well with enclosing gneisses. Despite Alentejo region have a reduced number of outcrops the granodiorite provides rounded to tabular metric blocks. The gabbro is very coarse grained, sometimes with a cumulate texture, and their fracturing and weathering provide very fresh tabular blocks. The five studied dolmens (Quinta do Freixo #1 to #5) are implanted in a large granodioritic intrusion, around the gabbroic rocks, within an area of approximately 9km2. The medium grained granodiorite is ubiquity in all the dolmens slabs and occasionally it can be observed features of mixing and mingling mechanisms; interpenetration of different magmas and enclaves. There were not identified slabs of gabbros in dolmens slabs. In distances less than 100m from the dolmens, it is possible to identify an outcrop with equal features (petrographic as well geometric) with those found in the slabs. These observations agrees with previous authors (e.g. Boaventura, 2000) that favours a pragmatic attitude of Neolithic populations in the search of the appropriate slabs for construction

Crustal growth and deformational processes in the northern

The aim of this article is to present a compilation of available information on the Évora Massif based on structural mapping, whole-rock geochemistry, recognition of metamorphic mineral assemblages, and geothermobarometry. In our view, transcurrent movements responsible for strong orogen-parallel stretching were dominant and had a major role in the geodynamic evolution of this part of Ossa-Morena zone (southwest Iberian Massif). Cadomian and Variscan orogenic events separated by a period of intense rifting were the cause for the composite distribution of zones with contrasting metamorphic paths, the structural complexity, the variety of lithological associations, and the sequence of deformation events and magmatism. The proposed geodynamic reconstruction for this segment of the northern Gondwana continental margin includes three main stages in chronological order: (1) Neoproterozoic accretion and continental magmatic arc developing, dismantling, and reworking, followed by late-“orogenic” magmatism; (2) Lower Paleozoic crustal thinning, block tilting, and mantle upwelling, induced by generalized rifting, leading to the formation of marine basins with carbonate platform sediments and thick accumulations of volcaniclastic and terrigenous sediments, contemporaneous with normal and enriched mid-oceanic ridge basalt–type magmatism; and (3) Upper Paleozoic transpressional orogenesis resulting from obliquity of convergence and the geometry of the involved blocks. The third stage includes the tectonic inversion of Lower Paleozoic basins, crustal thickening, the exhumation of high- to medium-pressure rocks and partial exhumation of high-grade metamorphic lithologies (controlled by local transtension and major detachments), the formation of synorogenic basins fi lled with volcanicsedimentary sequences, and fi nally, the emplacement of late Variscan granodiorites and granites

Um estudo sobre a rede de colaboração científica dos pesquisadores brasileiros com currículos cadastrados na Plataforma Lattes

Analyses of scientific collaboration networks have been widelyexplored in researches within different knowledge fields for quite some time,taking into account its ability to identify how groups of researchers areperforming their work collectively. These studies make it possible to identifyhow collaboration occurs between individuals through investigations based onsocial network metrics. In this paper, at first, a general characterization of theanalyzed data is presented, and afterward, a temporal analysis of the BrazilianPhDs scientific collaboration network with registered curricula in the LattesPlatform is conducted. For this purpose, all their scientific publications wereused for the identification and characterization of the collaboration networks. Asa result, it is possible to visualize how the scientific collaboration of theanalyzed set was intensified over the years, highlighting the areas of activity ofeach Brazilian PhD.As análises sobre as redes de colaboração científica vêm sendo amplamente exploradas em pesquisas de diversas áreas do conhecimento há algum tempo, tendo em vista a sua capacidade de identificar como grupos de pesquisadores têm realizado seus trabalhos coletivamente. Tais estudos possibilitam identificar como ocorre a colaboração entre os indivíduos através de análises baseadas em métricas de redes sociais. Neste trabalho, inicialmente é apresentada uma caracterização geral do conjunto analisado e, após, é realizada uma análise temporal da rede de colaboração científica dos doutores brasileiros com currículos cadastrados na Plataforma Lattes. Para isso, todas as publicações científicas dos doutores foram utilizadas para a identificação e caracterização das redes de colaboração. Como resultado, é possível visualizar como a colaboração científica do conjunto analisado foi sendo intensificada ao longo dos anos, com destaque para as grandes áreas de atuação de cada doutor

A spatial data warehouse to predict megaliths slabs sources: mixing geochemistry, petrology, cartography and archaeology for spatial analysis

MEGAGEO - Moving megaliths in the Neolithic is a project that aims to find the provenience of slabs used in the construction of dolmens. A multidisciplinary approach has been carried out with researchers from the several fields of knowledge involved. In this work it is presented a spatial data warehouse specially developed for the project, which comprises information from national archaeological databases, geographic and geological information and new geochemical and petrographic data obtained during the project. Redondo area is used as a case study for the application of the spatial data warehouse to analyze relationships between geochemistry, geology and the dolmens of the regio

Chemical-physical agents and biodeteriogens in the alteration of limestones used in coastal historical fortifications

The alteration of rocks is usually due to the chemical-physical processes that are initially established on the outer surface of the stone and gradually proceed towards the inner matrix. The chemical alteration generated by the interaction with atmospheric agents (weathering) involves the transformation of the mineral phases constituting the rock that are less stable in the current climatic conditions. That often leads to the formation of new secondary phases more stable with respect to the alteration. However, among these phases are often present some very soluble and hygroscopic phases (i.e., soluble salts, clay minerals) that cause inner degradation of the rock, due to their physical-mechanical actions (inner crystallization pressure, hydration dilation). In the case of carbonate rocks (limestone, sandstone with carbonate cement, etc.), the dissolution is the more frequent process, especially when the monuments were located within the cities, due to the acid meteoric precipitations (with H2CO3, H2SO4) that lead to the sulfation of carbonate matrix with formation of gypsum, very harmful to the stone. When the rock (e.g., clay-arenaceous limestones) naturally contains hygroscopic phases inside the matrix (i.e., marine salts, phyllosilicates) and they are also porous (> 20%), the physical degradation is accelerated, with decohesion of the mineralogical matrix (between the crystalline granules) and consequent disintegration of the stone. In the rock-atmosphere interaction often occurs the presence of biodeteriogens (plants, fungi, lichens, micro- organisms, etc.), which negatively participate and in various ways in the processes of rock alteration. The research aims to define the chemical-physical alteration factors on the limestones exposed to different bioclimatic and biogeographic contexts (Mediterranean and Atlantic), taking two study-case monuments located in the Italian and in the Portuguese coasts. In the study presented in this paper the preliminary results of the case-study of Cagliari fortifications have been discussed. In the study the different vascular plants present on stone surface and crevices and their different role in the degradation of limestone rocks have been also studied