Browsing by Author "Araujo, M. F."
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- Geochemical characterization of surficial sediments from the southwestern Iberian continental shelfPublication . Machado, A.; Rocha, F.; Araujo, M. F.; Vitali, F.; Gomes, C.; Dias, João A.The impact of trace elements (Ba, Nb, Zr, Y, Sr, Rb, Pb, As, Zn, Cu, Ni, Co, Cr, V, La, Ce, Nd, Sm, Eu, Th, Yb and Lu) transported by the Guadiana, Tinto-Odiel and Guadalquivir rivers on sediments from the southwestern Iberian continental shelf has been studied. Shelf surficial sediments from three transects established right in front of the river estuaries were characterized by specific signatures relative to those trace elements. The Guadiana transect shows high Zr concentration values; the Tinto-Odiel transect shows high heavy metal (Pb, As, Zn and Cu) concentration values; and the Guadalquivir transect shows high Sr concentration values. Data from the statistical analysis indicate three distinct sources for trace elements: lithogenic, biogenic and anthropogenic.
- Micro-EDXRF investigation of Chalcolithic gold ornaments from Portuguese EstremaduraPublication . Valerio, P.; Soares, A. M. M.; Araujo, M. F.; Carvalho, AntónioChalcolithic gold artefacts assigned to the Bell Beaker Culture in Portuguese Estremadura were analysed by micro-energy dispersive X-ray fluorescence spectrometry. These high-status jewels comprise beads of tubular, spiral and double-conical type, a spiral ring and a wire fragment. The collection is mainly composed of gold with 8.7-16.3 wt% Ag and <0.04 wt% Cu. Additionally, there is a typologically uncommon double-conical bead showing a lower Ag content (6.7 wt%). The relative intensity of the Ag-K and Ag-L X-rays from artefacts established the existence of a surface layer depleted in silver, while the reasonable effective penetration depth of the Ag-K (about 25-30m) provided suitable results for such high fineness gold alloys. A uniform Au-Ag composition at the joint indicates that the double-conical bead was made by joining two sheets without solder. Overall, the collection shows a composition that is similar to known Chalcolithic gold in Portuguese Estremadura but different from coeval gold in Southwestern Iberian Peninsula. The distinct compositional pattern of Chalcolithic gold in Portuguese Estremadura seems to be inconsistent with the natural variability of silver content in alluvial deposits of gold in Iberian Peninsula, thus suggesting a continuous use of particular sources and limited exchange of nuggets and jewels with the neighbouring region. Copyright (c) 2017 John Wiley & Sons, Ltd.