Chemistry of interstitial water of samples from DSDP Leg 38

Interstitial waters recovered during Leg 38 show large changes in major ion composition and also in oxygen isotope composition. Increases in Ca[++] and Sr[++] and decreases in K[+], Mg[++], and O18/O16 are interpreted in terms of extensive diagenesis of terrigenous, volcanic, or basaltic igneous materials in the sediments and underlying basalts. Slight, but well-established increases in chlorinity with depth indicate that these postulated weathering reactions involve uptake of water to a measurable extent. Interstitial waters from sites drilled on the Inner Voring Plateau suggest the infusion of fresh waters by aquifers from the mainland of Norway.

(Table 1) K-Ar age of alkaline igneous rocks from the Jan Mayen fracture zone

Bottom morphology of the Jan Mayen transform fracture zone and rock chemistry data show that petrological and chemical specific features of igneous rocks can result from higher permeability of the transform fracture zone and deeper penetration of ocean water into the lithosphere in comparison with rift zones of the Kolbeinsey and Mohn's mid-ocean ridges. Age of alkaline magmatism of the Jan Mayen fracture zone is similar to that of rift zones due to palingenesis of metamorphosed and hydrated mantle and crustal rocks.

Chemical composition and isotopic ratios of basic lavas from Iceland and the surrounding ocean floor

Major and trace dement data are used to establish the nature and extent of spatial and temporal chemical variations in basalts erupted in the Iceland region of the North Atlantic Ocean. The ocean floor samples are those recovered by legs 38 and 49 of the Deep Sea Drilling Project. Within each of the active zones on Iceland there are small scale variations in the light rare earth elements and ratios such as K/Y: several central complexes and their associated fissure swarms erupt basalts with values of K/Y distinct from those erupted at adjacent centres; also basalts showing a wide range of immobile trace element ratios occur together within single vertical sections and ocean floor drill holes. Although such variations can be explained in terms of the magmatic processes operating on Iceland they make extrapolations from single basalt samples to mantle sources underlying the outcrop of the sample highly tenuous. 87Sr/86Sr ratios measured for 25 of the samples indicate a total range from 0.7028 in a tholeiite from the Reykjanes Ridge to 0.7034 in an alkali basalt from Iceland and are consistent with other published ratios from the region. A positive correlation between 87Sr/86Sr and Ce/Yb ratios indicates the existence of systematic isotopic and elemental variations in the mantle source region. An approximately fivefold variation in Ce/Yb ratio observed in basalts with the same 87Sr/86Sr ratio implies that different degrees and types of partial melting have been involved in magma genesis from a single mantle composition. 87Sr/86Sr ratios above 0.7028, Th/U ratios close to 4 and La/Ta ratios close to 10 distinguish most basalts erupted in this part of the North Atlantic Ocean from normal mid-ocean ridge basalt (N-type MORB) - although N-type MORB has been erupted at extinct spreading axes just to the north and northeast of Iceland as well as the presently active Iceland-Jan Mayen Ridge. Comparisons with the hygromagmatophile element and radiogenic isotope ratios of MORB and the estimated primordial mantle indicate that the mantle sources producing Iceland basalts have undergone previous depletion followed by more recent enrichment events. A veined mantle source region is proposed in preference to the mantle plume model to explain the chemical variations.

Mineralogy of ODP Leg 104 holes

The mineralogical and geochemical study of samples from Sites 642, 643, and 644 enabled us to reconstruct several aspects of the Cenozoic paleoenvironmental evolution (namely volcanism, climate, hydrology) south of the Norwegian Sea and correlate it with evolution trends in the northeast Atlantic. Weathering products of early Paleogene volcanic material at Rockall Plateau, over the Faeroe-Iceland Ridge and the Voring Plateau indicate a hot and moist climate (lateritic environment) existed then. From Eocene to Oligocene, mineralogical assemblages of terrigenous sediments suggest the existence of a warm but somewhat less moist climate at that time than during the early Paleogene. At the beginning of early Miocene, climatic conditions were warm and damp. The large amounts of amorphous silica in Miocene sediment could indicate an important flux of silica from the continent then, or suggest the formation of upwelling. Uppermost lower Miocene and middle to upper Miocene clay assemblages suggest progressive cooling of the climate from warm to temperate at that time. At the end of early Miocene, hydrological exchanges between the North Atlantic and the Norwegian Sea became intense and gave rise to an important change in the mineralogy of deposits. From Pliocene to Pleistocene, the variable mineralogy of deposits reflects alternating glacial/interglacial climatic episodes, a phenomenon observed throughout the North Atlantic.

Solubility of carbon dioxide, ethane, methane, oxygen, nitrogen, hydrogen, argon, and carbon monoxide in 1-butyl-3-methylimidazolium tetrafluoroborate between temperatures 283 K and 343 K and at pressures close to atmospheric

Experimental values for the solubility of carbon dioxide, ethane, methane, oxygen, nitrogen, hydrogen, argon and carbon monoxide in 1-butyl-3- methylimidazolium tetrafluoroborate, [bmim][BF4] - a room temperature ionic liquid - are reported as a function of temperature between 283 K and 343 K and at pressures close to atmospheric. Carbon dioxide is the most soluble gas with mole fraction solubilities of the order of 10-2. Ethane and methane are one order of magnitude more soluble than the other five gases that have mole fraction solubilities of the order of 10-4. Hydrogen is the less soluble of the gaseous solutes studied. From the variation of solubility, expressed as Henry's law constants, with temperature, the partial molar thermodynamic functions of solvation such as the standard Gibbs energy, the enthalpy, and the entropy are calculated. The precision of the experimental data, considered as the average absolute deviation of the Henry's law constants from appropriate smoothing equations is of 1%. © 2005 Elsevier Ltd. All rights reserved.