Assessing the diurnal evolution of surface radiation balance over the western region of Tropical Atlantic Ocean using in situ measurements carried out during the FluTuA balance Project

In this work, the diurnal evolution of the radiation balance components over the tropical Atlantic Ocean is described and analysed. The analysis is based on measurements carried Out on board a Brazilian Navy ship during the observational campaign of the FluTuA Project (`Fluxos Turbulentos sobre o Atlantico`), from 15 to 23 May 2002. The observations indicated that the albedo responds its expected to atmospheric attenuation effects with a diurnal evolution similar to the Fresnel albedo. In general, the observed longwave radiation values agreed better with the estimated values obtained without longwave reflection. In agreement with the literature, the average surface emissivity was around 0.97. The net radiation, estimated from published equations for albedo, atmospheric transmissivity and surface emissivity, agreed with the observations, indicating that these parameters are representative of the radiometric properties of the air-sea interface in the region between Natal (6 degrees S, 35.2 degrees W) and the Sao Pedro and Sao Paulo Archipelago (1 degrees N, 29.3 degrees W). Copyright (C) 2008 Royal Meteorological Society

Post-collisional lamprophyric event in Sierra Norte, Cordoba, Argentina: Mineralogical, geochemical and isotopic characteristics

Over 20 lamprophyre dykes, varying in width between a few centimeters and several meters, have been identified in central Sierra Norte - Eastern Pampean Ranges, Cordoba, Argentina. Their mineralogy and chemistry indicate that they are part of the calc-alkaline lamprophyres clan (CAL). They contain phenocrysts of magnesiohomblende +/- augite set in a groundmass of magnesiohornblende, calcic-plagioclase, alkali feldspar, and opaque minerals, which designate them as spessartite-type lamprophyres. Alteration products include chlorite, calcite and iron oxides after malfic phenocrysts, though some are partially replaced by actinolite. Feldspars are replaced by carbonate and clay minerals. The dykes are relatively primitive, and show restricted major element variation (SiO(2) 51.1-55.3 wt.%, Al(2)O(3) 12-16.6 wt.%, total alkalies 1.5-4.7 wt.%), high Mg# (55-77), high Cr contents (27-988 ppm) and moderate to high Ni contents (60-190 ppm). Lamprophyre LILE (e.g. Rb averages 110 ppm, Sr 211-387 ppm, Ba 203-452 ppm) are high relative to HFSE (e.g., Ta 0.2-1.6 ppm, Nb 4-11 ppm, Y 17-21 ppm), and are enriched in LREE (30-70 times chondrite). They are characterized by relatively high (208)Pb/(204)Pb (38.8-39.9), (207)Pb/(204)Pb(similar to 15.7), and (206)Pb/(204)Pb (18.7-20.1), combined with low (epsilon)epsilon(Nd) (-4.69 to -1.52) and a relative moderately high ((87)Sr/(86)Sr)(i) of 0.7055-0.7074. The Rb-Sr whole rock isochron indicates an Early Ordovician age of 485 +/- 25 Ma. The calculated T(DM) (1.7 Ga) suggests that these rocks appear to have originated from a reservoir that was created during a mantle metasomatism event related to the Pampean orogeny. The Sierra Norte lamprophyres show affinities with a subduction-related magma in an active continental margin. Their geochemical and isotopic features suggest a multicomponent source, composed of enriched mantle material variably contaminated by crustal components. The lamprophyric suite emplacement occurred at the dawning stage of the Pampean orogeny, in a regional post-collisional extensional setting developed in the Sierra Norte-Ambargasta batholith (SNAB) in Early Ordovician times. (C) 2008 Published by Elsevier Ltd.