M.I. Dias

FIRING TESTS ON CLAY-RICH RAW MATERIALS FROM THE ALGARVE BASIN (SOUTHERN PORTUGAL): STUDY OF MINERAL TRANSFORMATIONS WITH TEMPERATURE

In cases where the provenance of raw materials used in the manufacture of local archeological ceramics is of interest, a detailed study of thermal transformations of minerals may be useful. The purpose of this study was to measure mineralogical transformations of different types of clays obtained during experimental firing runs, carried out at different temperatures, with the main goal of establishing Algarve reference groups based on the composition of raw material and high-temperature mineralogy, which may be compared with ceramics in studies of provenance. Eleven samples of clay-rich raw materials from the Algarve Basin (southern Portugal) were fired to temperatures ranging from 300 to 1100°C in increments of 100°C under oxidizing conditions. These were chosen to have variable chemical and mineralogical compositions, representing the main compositional range of the clay deposits from the region. Mineralogical and geochemical characterizations of the original clays were carried out by X-ray diffraction (XRD) and X-ray fluorescence (XRF), respectively. Mineral transformations on the fired products were also studied by XRD.Three groups of clays were distinguished according to the type of neoformed high-temperature minerals: (1) non-calcareous clays; (2) clays containing calcite as the only carbonate; and (3) clays with dolomite or dolomite + calcite. Firing of non-calcareous clays produced mullite at 1100–1200°C. Gehlenite and wollastonite formed by firing calcite-rich clays above 900°C, accompanied by anorthite or larnite in samples with small or large calcite contents, respectively. Firing of dolomite-rich clays at temperatures >900°C yielded a member of the gehlenite-åkermanite group and diopside. Anorthite, enstatite, periclase, forsterite, and monticellite may also form in the firing products.

Geochemistry and Mineralogy of Clays from the Algarve Basin, Portugal: A Multivariate Approach to Palaeoenvironmental Investigations

Lower Cretaceous and Triassic-Hettangian clays from the Algarve Basin (South Portugal) were deposited in distinct environments during basin subsidence due to Pangea break up. The mineralogy, geochemistry and granulometry of 45 samples of both clay groups were studied, using X-ray diffraction, instrumental neutron activation analysis, X-ray fluorescence and laser diffractometry by attenuation of X-rays. Multivariate statistical techniques (principal component analysis and K-means clustering), after scandium normalization of chemical contents, were used to study simultaneously all data, enabling to distinguish the different clay types by establishing the best discriminatory parameters: high contents (in decreased order) of kaolinite, quartz, Chemical Index of Alteration (CIA), Ti, goethite, Hf, Si, > 63 μm fraction and Zr, characterize the group of clays from Cretaceous; while high contents of hematite, Mg, mobile elements (K, Cs and P), illite, Ca, phyllosilicates in general, Mn and dolomite, are associated to Triassic-Hettangian clays. This approach revealed useful to facilitate the integration of all data, as was possible to confront the geochemistry with the mineralogy, enabling the best palaeoenvironmental interpretations. In fact, the clay mineral assemblage is significantly influenced by the domi- nant weathering process and provides information on changes in aridity/humidity patterns.

Clay resources in the Nelas region (Beira Alta), Portugal. A contribution to the characterization of potential raw materials for prehistoric ceramic production

Abstract Mineralogical and chemical compositions of residual and sedimentary clays (bulk and <2 μm fraction) from the Nelas region (schist, aplite-pegmatites, granites and Tertiary sediments from both Mondego River margins), Portugal, were studied, aiming to establish indicators for raw materials in ancient ceramic provenance studies. The mineralogy of bulk material does not provide a clear distinction between samples. Among clay minerals, kaolinite dominates, except in the aplite-pegmatites where illite prevails. Smectite was only found in sediments of the left river bank. A more successful result was the geochemical differentiation of clay types. The weathered schist presents greater enrichment in Cr, whereas the clay fraction of aplite-pegmatites shows enrichment in all the chemical elements studied. The sediments and weathered granites are not easy to differentiate; the best geochemical indicators are U (lower contents in clay-size fraction of sediments) and REE patterns in both bulk and clay-size fraction.

Chemical element accumulation in tree bark grown in volcanic soils of Cape Verde—a first biomonitoring of Fogo Island

Barks from Prosopis juliflora (acacia) were collected in 12 sites of different geological contexts over the volcanic Fogo Island (Cape Verde). Elemental contents of Ba, Br, Co, Cr, Fe, K, Na, Zn and some rare earth elements (REE)—La, Ce, Sm, Eu, Tb, Yb, and Lu, were obtained for biological samples and topsoils by using k0-standardized and comparative method of instrumental neutron activation analysis (INAA), aiming the evaluation of chemical elements uptake by acacia bark. This first biomonitoring study of Fogo Island showed that, in general, significant accumulations of trace elements present in high amounts in these soils occur. This can be partially explained by the semi-arid climate with a consequent bioavailability of chemical elements when rain drops fall in this non-polluted environment. REE enrichment factors (EFs) increase with the decrease of ionic radius. Heavy REE (HREE) are significantly enriched in bark, which agrees with their release after the primary minerals breakdown and the formation of more soluble compounds than the other REE, and uptake by plants. Among the potential harmful chemical elements, Cr appears to be partially retained in nanoparticles of iron oxides. The high EFs found in tree barks of Fogo Island are certainly of geogenic origin rather than anthropogenic input since industry and the use of fertilizers is scarce.

A micro-invasive approach using INAA for new insights into Palaeolithic flint archaeological artefacts

Instrumental neutron activation analysis of small flakes from the same flint fragment of archeological artefacts from Palaeolithic sites (“Abrigo de la Quebrada”, “Cova de les Cendres” and “Cova Negra”), and geological sources (Chelva, Valencia, and Alcoi, Alicante) from the eastern Spain, was performed. The chemical contents of 27 elements were obtained. Ga, Ce, Nd, Yb, Zr and Hf were discarded due to high variations within the same fragment. The identification of chemical fingerprints within heterogeneous flint fragments was able to differentiate flint types and variants (“Domeño” and “Serreta”), contributing to provenance and human mobility in ancient times.

RADIOCARBON AND BLUE OPTICALLY STIMULATED LUMINESCENCE CHRONOLOGIES OF THE OITAVOS CONSOLIDATED DUNE (WESTERN PORTUGAL)

The dune of Oitavos, the underlying paleosol, and Helix sp. gastropod shells found within the paleosol were dated using a combination of radiocarbon and blue optically stimulated luminescence (OSL). The organic component of the paleosol produced a significantly older age (~20,000 cal BP) than the OSL age measurement (~15,000 yr), while 14C age measurements on the inorganic component and the gastropods produced ages of ~35,000 yr and ~34,000 yr, respectively. Rare-earth element analyses provide evidence that the gastropods incorporate geological carbonate, making them an unreliable indicator of the age of the paleosol. We propose that the 14C age of the small organic component of the paleosol is also likely to be unreliable due to incorporation of residual material. The OSL age measurement of the upper paleosol (~15,000 yr) is consistent with the age for the base of the dune (~14,500 yr). The younger OSL age for the top of the dune (~12,000 yr) suggests that it was built up by at least 2 sand pulses or that there was a remobilization of material at the top during its evolution, prior to consolidation.

Post-depositional processes of elemental enrichment inside dark nodular masses of an ancient aeolian dune from A Coruña, Northwest Spain

This paper focuses on a residual ancient aeolian climbing dune from Punta Penaboa (A Coruna, Northwest Spain) showing evidence of post-depositional weathering, particularly the presence of dark brown nodular masses. The partitioning of trace elements between nodular masses and host sand during post-depositional weathering of the dune is investigated in this work, with the main objective of studying the elemental enrichment patterns in the dark masses. Data of the concentrations of chemical elements were obtained by instrumental neutron activation analysis (INAA) and complemented by mineralogical and microchemical studies, using X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) / energy dispersive X-ray spectrometry (EDS). The dune was dated by optically stimulated luminescence (OSL) , yielding an age of 300ka B.P.. The dark nodular masses preserved the dune sand structure, without defined concentric layers, suggesting an early stage of formation. They consist mainly of quartz grains cemented by clay materials enriched in the majority of the elements studied, especially in Mn, Co, Ba, Sb, Ce, Tb, Th, As, Zr and Hf. The post-depositional transformations of the dune were most likely influenced by migration of chemical compounds from the surrounding slope deposits and granitic rocks, as well as microbial activity that promoted metals concentration in the solutions percolating through the pore network of the dune. Seasonal changes in the redox potential were required to produce the accumulation of Mn and other trace elements in the dune pore network and to promote the fractionation between Ce4+ and trivalent rare earth elements that was observed in the geochemical patterns.

Middle Guadiana River Basin (Badajoz, Spain and Alentejo, Portugal) Network Interactions: Insights from the Chemical Analysis of Bell Beaker Pottery and the Lead Isotope Analysis of Copper Items from the Third Millennium BC

Several settlement networks from the Iberian Copper Age period are located alongside the Guadiana River (Iberian Peninsula) – i.e. Perdigoes, Reguengos de Monsaraz, Portugal (Dias et al.2005; Valera 2006), or Tierra de Barros, Badajoz, Spain (Hurtado 1995,1999). In this context, a clear relation has been found between the sites in terms of spatial organization (hierarchical, where La Pijotilla could be considered as a central place in a core-periphery system), a restricted stylistic distribution of the so-called Guadiana ‘eyed idol’ figurines (Hurtado 2008), or the distribution of bone based inlayed Bell Beaker pottery (Hurtado and Odriozola 2008; Odriozola in press).

Geochemistry of mudrock units from the Meso-Cenozoic Algarve Basin, Portugal

Geochemistry of mudrock units deposited in the sedimentary basin of Algarve (South Portugal) during Mesozoic and Cenozoic depositional cycles were studied, aiming a better knowledge of the evolution of the Basin. Two types of mudrock units were found: (i) silicic and Ca-poor (Cretaceous and Cenozoic), and (ii) calcareous (Middle–Upper Jurassic Ca-rich mudrock units and Upper Triassic to Lower Jurassic Mg-rich redbeds). LILE appear to be controlled by a K-bearing phyllosilicate, which is consistent with the abundant illite in the redbeds. Positive trends of: (i) Sc, Cr, Th, LREE with Al2O3 suggests their incorporation in clay minerals, and (ii) HREE with TiO2, Zr and Hf point to their presence in heavy minerals. The source area of the Algarve mudrock units was dominated by felsic rocks; features typical of a mafic source occur in some Upper Triassic to Lower Jurassic samples. Carboniferous metasediments of the basement were probably the first order source for the Algarve sedimentary basin. A more severe weathering in the Cenozoic and Cretaceous mudrock units occurred, whereas diagenetic enrichment in potassium is observed in the Upper Triassic to Lower Jurassic continental redbeds.

A device-specific prioritization strategy based on the potential for harm to human health in informal WEEE recycling

In developing countries, the recovery of valuable materials from Waste Electrical and Electronic Equipment (WEEE) is carried out via uncontrolled practices, posing potentially severe risks both to human health and the environment. The assessment of the risk, which depends on both the kind and hazardous properties of the substances contained in WEEE, is currently limited as the exposure scenario for the single informal practice cannot be fully characterized for this purpose. In this context, this work proposes and evaluates a strategy to identify the relative potential harm of different kinds of WEEE by their content in metals, selected as the target substances of concern. This was based on the individual metal content, primarily located in the printed circuit boards (PCBs) of the different devices. The metal composition of the individual PCBs was identified and the dominant unregulated metal recovery practices were reviewed to identify the most suitable parameter to express the toxicity of these metals. Based on a mass-normalized cumulative toxicity, via the inhalation route, individual components were assessed from compositional variation found in the literature. The results is a semiquantitative ranking of individual components, revealing significant differences in potential harm posed by different electronic appliances and an opportunity to provide prioritization strategies in future management.