A CORRELATION STUDY OF MAJOR AND TRACE ELEMENTS IN SEDIMENTS OF RIVER NESTOS, NORTHERN GREECE AND COMPARISON WITH OTHER FLUVIAL SYSTEMS

ABSTRACT Fourteen sediment samples from the banks of River Nestos, Northern Greece, were collected, extracted with HNO 3 and analyzed for their content in 10 major and 32 trace elements. The analytical techniques used were ICP-OES and ICP-MS. The calculation of the Pearson Correlation Coefficient amongst the analyzed elements has revealed that among the majority of the elements exist positive correlations, which explains why most of them have a similar distribution along the river course. A comparison between the results acquired for the River Nestos and other fluvial systems, national and international, has shown the similarity of the geochemical identity of the River Nestos sediments with these systems

The Abra del rock shelter, northwestern Argentina, a space ocuppied by hunter-gatherers that was hit by the large 4.2 ka Cerro Blanco eruption

Occupation sites have been rarely found during research on the prehistorical hunter-gatherer populations in the Andean intermontane valleys. Some reasons are the intense anthropization of the landscape and the scarce research efforts. Recent work opens new perspectives at the Abra del Toro rock shelter in the Yocavil valley (province of Catamarca, Argentina). Stratigraphy of rock shelter shows a 1 m thick volcanic ash deposit formed by wind transportation from primary ash-fall deposits. Geomorphological, sedimentological, textural, glass and mineral content, bulk chemical composition, and radiocarbon dating prove the tephra derived from the 4.2 ka BP eruption of the Cerro Blanco Volcanic Complex in the southern Puna. This is the world's largest documented volcanic eruption in the past five thousand years, and it covered the archeological site surroundings with an approximately 1-meter-thick ash-fall layer. Throughout the stratigraphic sequence of the Abra del Toro rock shelter, we can hypothesize that there were three main occupational moments: two hunter-gatherer moments, separated by the record of the large volcanic eruption, and a latern agro-pottery period. The evidence of the catastrophic volcanic event in the Abra del Toro rock shelter makes it possible to predict future impact on the contemporaneous communities.Fil: Carbonelli, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto de las Culturas. Universidad de Buenos Aires. Instituto de las Culturas; ArgentinaFil: Fernandez Turiel, Jose Luis. Consejo Superior de Investigaciones Científicas; EspañaFil: Belotti López de Medina, Carlos Raúl. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto de las Culturas. Universidad de Buenos Aires. Instituto de las Culturas; Argentin

New ages, morphometric and geochemical data on recent shoshonitic volcanism of the Puna, Central Volcanic Zone of Andes: San Jerónimo and Negro de Chorrillos volcanoes

International audienceShoshonitic volcanic centres are scarce within the back-arc mafic volcanism of the Puna Plateau in the Central Volcanic Zone of the Andes. San Jerónimo and Negro de Chorrillos volcanoes are two well preserved shoshonitic monogenetic edifices that developed mainly Strombolian activity and lava flows, which extended more than 9 and 4 km from the vent, producing a volume DRE (Dense Rock Equivalent) of 0.091 and 0.020 km3, respectively. The new unspiked K–Ar (groundmass) ages of San Jerónimo (144 ± 3 ka) and Negro de Chorrillos (51 ± 2 ka) eruptions presented in this work are both younger than those previously published. Petrographic and compositional features allow distinguishing between potassic and ultrapotassic suites in volcanic products of both eruptions. Phlogopite occurrence and low glass content characterize the ultrapotassic suite. Based on the crustal thickness of this part of the Puna and the experimental constraint, these magmas last equilibrated at Moho depths at around 50 km (the highest depth of spinel lherzolite stability field) for temperatures of 1100–1200 °C. Once in the crust, the K-rich magma underwent a minor interaction with a trachytic-trachydacitic melt, which is evidenced petrographically and geochemically, e.g., mismatch of mineral assemblages (co-occurrence of olivine and quartz), disequilibrium crystal textures (dusty zones in plagioclase, embayments in sanidine), and a wide range of compositional variation in the glasses. Ultrapotassic (i.e., phlogopite-bearing) and potassic lavas in the same eruption are interpreted as pulses of the same magma but with a longer mixing time with the trachytic-trachydacitic melt for the resulting ultrapotassic rocks within an eruptive time frame of hours or days. The singular shoshonitic character of these magmas could be related to their origin along an old terrane boundary. Afterwards, as occurs for other mafic magmas of the Puna, major NW-SE fault systems would favour their ascent to the surface

Multivariate factorial analysis to design a robust batch leaching test to assess the volcanic ash geochemical hazard

A method to obtain robust information on short term leaching behaviour of volcanic ashes has been developed independently on the sample age. A mixed factorial design (MFD) was employed as a multivariate strategy for the evaluation of the effects of selected control factors and their interactions (amount of sample (A), contact time (B), and liquid to solid ratio or L/S (C)) on the leaching process of selected metals (Na, K, Mg, Ca, Si, Al, V, Mn, Fe, and Co) and anions (Cl - and SO 4 2-). Box plots of the data acquired were used to evaluate the reproducibility achieved at different experimental conditions. Both the amount of sample (A) and leaching time (B) had a significant effect on the element stripping whereas the L/S ratio influenced only few elements. The lowest dispersion values have been observed when 1.0g was leached with an L/S ratio equal to 10, shaking during 4h. The entire method is completed within few hours, and it is simple, feasible and reliable in laboratory conditions.Fil: Ruggieri Flavia. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias de la Tierra Jaume Almera; EspañaFil: Gil, Raul Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; ArgentinaFil: Jose Luis Fernandez Turiel. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias de la Tierra Jaume Almera; EspañaFil: Julio Saavedra. Irnasa; EspañaFil: Domingo Gimeno. Facultad de Geologia; EspañaFil: Agustin Lobo. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias de la Tierra Jaume Almera; EspañaFil: Luis D. Martinez. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; ArgentinaFil: Alejandro Rodriguez Gonzalaez. Departamento de Fisica- Universidad de Las Palmas; Españ