Grain sizes and mineral composition of the basement of ODP Site 206-1256

Hole 1256C was cored 88.5 m into basement, and Hole 1256D, the deep reentry hole, was cored 502 m into basement during Ocean Drilling Program Leg 206. Hole 1256D is located ~30 m south of Hole 1256C (Wilson, Teagle, Acton, et al., 2003, doi:10.2973/odp.proc.ir.206.2003). A thick massive flow drilled in both holes, Units 1256C-18 and 1256D-1, consists of a single cooling unit of cryptocrystalline to fine-grained basalt, interpreted as a ponded lava, 32 m and at least 74.2 m thick, respectively. This ponded flow gives us a unique opportunity to examine textural variations from the glassy, folded crust of the lava pond recovered from the top of Unit 1256C-18 through the coarse-grained, thick massive lava body to the unusually recrystallized and deformed base cored in Unit 1256C-18. Some detailed descriptions of the textures and grain size variations through the lava pond (Units 1256C-18 and 1256D-1), with special reference to the recrystallization of the base of Unit 1256C-18, are presented here.

(Table T1) Trace-element abundances for igneous basement at ODP Site 206-1256

In this report, I present trace element data for basement samples at Ocean Drilling Program (ODP) Site 1256. The samples analyzed represent a subset of the group ("pool") samples from ODP Leg 206, and these trace element data are part of a more comprehensive data suite for the same samples, with analyses of stable and radiogenic isotopes (e.g., Sr, Li, and O) in progress or recently completed that will be presented elsewhere. The trace element analyses were performed in the GeoAnalytical Lab at Washington State University. The following elements were analyzed: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ba, Th, Nb, Y, Hf, Ta, U, Pb, Rb, Cs, Sr, Sc, and Zr. Trace element data indicate that the igneous basement at Site 1256 is geochemically normal mid-ocean-ridge basalt. A massive ponded flow sampled in both Holes 1256C and 1256D is distinguished by higher abundances of rare earth elements (REE) and most of the other trace elements analyzed. One interval of highly altered basalt has significantly higher concentrations of Cs, Rb, and Ba and lower concentrations of Sr, Pb, Zr, Hf, Sc, and most REE than the samples of background alteration or halos. No correlation is obvious between trace element abundance and macroscopic type of alteration within the background alteration or halos.

Geochemistry of oceanic crust of the Cocos Plate

New geochemical data from the Cocos Plate constrain the composition of the input into the Central American subduction zone and demonstrate the extent of influence of the Galápagos Hotspot on the Cocos Plate. Samples include sediments and basalts from Ocean Drilling Program (ODP) Site 1256 outboard of Nicaragua, gabbroic sills from ODP Sites 1039 and 1040, tholeiitic glasses from the Fisher Ridge off northwest Costa Rica, and basalts from the Galápagos Hotspot Track outboard of Central Costa Rica. Site 1256 basalts range from normal to enriched MORB in incompatible elements and have Pb and Nd isotopic compositions within the East Pacific Rise MORB field. The sediments have similar 206Pb/204Pb and only slightly more radiogenic 207Pb/204Pb and 208Pb/204Pb isotope ratios than the basalts. Altered samples from the subducting Galápagos Hotspot Track have similar Nd and Pb isotopic compositions to fresh Galápagos samples but have significantly higher Sr isotopic composition, indicating that the subduction input will have a distinct geochemical signature from Galápagos-type mantle material that may be present in the wedge beneath Costa Rica. Gabbroic sills from Sites 1039 and 1040 in East Pacific Rise (EPR) crust show evidence for influence of the Galápagos Hotspot ?100 km beyond the morphological hotspot track.

Diário da Constituinte [gravação de vídeo] : [programa n. 206]

O Ministro da Fazenda Bresser Pereira reuniu-se com os constituintes para tentar alterar o texto do substitutivo sobre a reforma tributária. Mas os parlamentares disseram que é difícil modificar o aumento de 33 para 50% da transferência de recursos da União para os Estados e Municípios. O Deputado Bernardo Cabral (PMDB-AM) foi ao Plenário defender-se das críticas sobre a quebra do acordo realizado com as Forças Armadas no texto do substitutivo referente à anistia. O Relator disse que não se comprometeu com ninguém, logo não houve traição. A Comissão das Nações Unidas para o Meio Ambiente está no Brasil para apresentar aos constituintes o relatório "Nosso Futuro Comum", que foi entregue ao Presidente da Assembleia Nacional Constituinte (ANC), Deputado Ulysses Guimarães. A representante da ONU Margarita Marino relata que é muito importante para a Comissão estar neste momento histórico no Congresso, quando aqui se prepara a Carta Magna. O Deputado Fábio Feldmann (PMDB-SP) considera importante que haja uma visão ampla de meio ambiente, que se incorpore ao planejamento nacional do desenvolvimento do país. Artistas foram à Assembleia Nacional Constituinte para reivindicar o fim de qualquer tipo de censura. A atriz Lélia Abramo informa que o povo brasileiro é livre e deve ter o direito de escolher o que lhe convém ou não. Sindicalistas apresentaram ao relator Bernardo Cabral diversas sugestões, que incluem a discordância com a retirada da estabilidade no emprego no texto do substitutivo e a reivindicação da jornada de 40 (quarenta) horas semanais. O Presidente da CNTI José Calixto informa sobre a exclusão de alguns direitos dos trabalhadores no projeto. O Deputado Paulo Paim (PT-RS) sugere que cada parlamentar apresente sua posição e vote sobre a estabilidade no Plenário da Assembleia Nacional Constituinte.