Major element compositions, minerals and trace elements at DSDP Leg 67 Holes

Mineralogical (microprobe) and geochemical (X-ray fluorescence, neutron activation analyses) data are given for 18 samples of volcanic rocks from the Guatemala Trench area (Deep Sea Drilling Project Leg 67). Typical fresh oceanic tholeiites occur in the trench itself (Hole 500) and in its immediate vicinity on the Cocos Plate (Site 495). Several samples (often reworked) of "spilitic" oceanic tholeiites are also described from the Trench: their mineralogy (greenschist facies association - actinolite + plagioclase + chlorite) and geochemistry (alteration, sometimes linked to manganese and zinc mineralization) are shown to result from high-temperature (300°-475°C) hydrothermal sea water-basalt interactions. The samples studied are depleted in light rare-earth elements (LREE), with the exception of the slightly LREE-enriched basalts from Hole 500. The occurrence of such different oceanic tholeiites in the same area is problematic. Volcanic rocks from the Guatemala continental slope (Hole 494A) are described as greenschist facies metabasites (actinolite + epidote + chlorite + plagioclase + calcite + quartz), mineralogically different from the spilites exposed on the Costa Rica coastal range (Nicoya Peninsula). Their primary magmatic affinity is uncertain: clinopyroxene and plagioclase compositions, together with titanium and other hygromagmaphile element contents, support an "active margin" affinity. The LREE-depleted patterns encountered in the present case, however, are not frequently found in orogenic samples but are typical of many oceanic tholeiites.

Indicators on community art practices: some reflections

From the Divercity project, the article reflects on methodology, good practices and indicators useful for community art practices. At first term, social exclusión is defined as well as community art, and which features it presents. Subsequently, the article reviews the indicators that are being used to measure the success or achievement of community arts practice, raising criticism from equality and including indicators that measure the well-being of women.

Crisis Económica en África Occidental: el caso de Dakar, 1929-1939

En este artículo se explora el impacto socio-económico de la crisis internacional de 1929 en Senegal y más concretamente en la ciudad-puerto de Dakar. Se analizan las consecuencias de la dependencia externa y la extroversión económica que caracterizaba a las estructuras productivas coloniales, destacando también la respuesta organizada de los movimientos sociales africanos. Por otra parte, se estudia la evolución de las infraestructuras y actividad portuaria, observando la metropolización regional de Dakar durante este periodo.

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests.

The seasonal climate drivers of the carbon cy- cle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combina- tion of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measure- ments and 35 litter productivity measurements), their asso- ciated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonal- ity in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rain- fall is < 2000 mm yr-1 (water-limited forests) and to radia- tion otherwise (light-limited forests). On the other hand, in- dependent of climate limitations, wood productivity and lit- terfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosyn- thetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest pro- ductivity in a drier climate in water-limited forest, and in cur- rent light-limited forest with future rainfall < 2000 mm yr-1.

Reescrita de textos-fonte e autoria: serão mesmo incompatíveis?

O que ocorre quando crianças de 8 anos são solicitadas a reescrever, em provas escolares, textos-fonte previamente lidos por sua professora? Analisando 116 textos escritos por 30 estudantes de terceiro ano do Ensino Fundamental em escola pública paulista, o estudo procurou investigar: 1) As operações de escrita utilizadas pelos participantes; e 2) A possibilidade de encontrar criação em textos cuja proposta inicial era a de reprodução parafrástica. Partiu-se de uma concepção de linguagem que a vê tanto como um trabalho linguístico, um elemento ontológico fundador do ser humano (ROSSI-LANDI, 1985) quanto salienta seu caráter voltado para à variação e para a criatividade (BENVENISTE, 1991). Concluiu-se que, mesmo em exercícios escolares nos quais aparentemente existe pouco espaço para a inventividade, o exercício da escrita autoral pode irromper, pois as brechas de incompreensão e/ou equívoco que os textos apresentam para as crianças abrem oportunidades para o surgimento da subjetividade. Palavras-chave: escrita; reformulação parafrástica; autoria.