Trace element zoning in pyroxenes from ODP Hole 735B gabbros: diffusive exchange or synkinematic crystal fractionation?

Major and trace element profiles of clinopyroxene grains in oceanic gabbros from ODP Hole 735B have been investigated by a combined in situ analytical study with ion probe, and electron microprobe. In contrast to the homogeneous major element compositions, trace elements (REE, Y, Cr, Sr, and Zr) show continuous core to rim zoning profiles. The observed trace element systematics in clinopyroxene cannot be explained by a simple diffusive exchange between melts and gabbros along grain boundaries. A simultaneous modification of the melt composition is required to generate the zoning, although Rayleigh fractional crystallization modelling could mimic the general shape of the profiles. Simultaneous metasomatism between the cumulate crystal and the porous melt during crystal accumulation is the most likely process to explain the zoning. Deformation during solidification of the crystal mush could have caused squeezing out of the incompatible element enriched residual melts (interstitial liquid). Migration of the melt along grain boundaries might carry these melt out of the system. This process named as synkinematic differentiation or differentiation by deformation (Natland and Dick in J Volcanol Geotherm Res 110(3–4):191–233, 2001) may act as an important magma evolution mechanism in the oceanic crust, at least at slow-spreading ridges.     

Differential modulation of eastern oyster (<Emphasis Type="Italic">Crassostrea virginica</Emphasis>) disease parasites by the El-Niño-Southern Oscillation and the North Atlantic Oscillation

The eastern oyster (Crassostrea virginica) is affected by two protozoan parasites, Perkinsus marinus which causes Dermo disease and Haplosporidium nelsoni which causes MSX (Multinucleated Sphere Unknown) disease. Both diseases are largely controlled by water temperature and salinity and thus are potentially sensitive to climate variations resulting from the El Niño-Southern Oscillation (ENSO), which influences climate along the Gulf of Mexico coast, and the North Atlantic Oscillation (NAO), which influences climate along the Atlantic coast of the United States. In this study, a 10-year time series of temperature and salinity and P. marinus infection intensity for a site in Louisiana on the Gulf of Mexico coast and a 52-year time series of air temperature and freshwater inflow and oyster mortality from Delaware Bay on the Atlantic coast of the United States were analyzed to determine patterns in disease and disease-induced mortality in C. virginica populations that resulted from ENSO and NAO climate variations. Wavelet analysis was used to decompose the environmental, disease infection intensity and oyster mortality time series into a time–frequency space to determine the dominant modes of variability and the time variability of the modes. For the Louisiana site, salinity and Dermo disease infection intensity are correlated at a periodicity of 4 years, which corresponds to ENSO. The influence of ENSO on Dermo disease along the Gulf of Mexico is through its effect on salinity, with high salinity, which occurs during the La Niña phase of ENSO at this location, favoring parasite proliferation. For the Delaware Bay site, the primary correlation was between temperature and oyster mortality, with a periodicity of 8 years, which corresponds to the NAO. Warmer temperatures, which occur during the positive phase of the NAO, favor the parasites causing increased oyster mortality. Thus, disease prevalence and intensity in C. virginica populations along the Gulf of Mexico coast is primarily regulated by salinity, whereas temperature regulates the disease process along the United States east coast. These results show that the response of an organism to climate variability in a region is not indicative of the response that will occur over the entire range of a particular species. This has important implications for management of marine resources, especially those that are commercially harvested.     

The oldest tylosaurine mosasaur (Reptilia; Lacertilia) from the Late Cretaceous of Belgium: Hermann von Meyer (1860) revisited

A mosasaurid parietal from the Late Cretaceous of Belgium, originally described by Von Meyer (1860), turns out to be assignable to the tylosaurine Hainosaurus cf. bernardi Dollo 1885. A small sediment sample, extracted from the bone, was analysed for coccoliths and revealed its early Late Campanian age. This is thus the earliest record of a tylosaurine mosasaur from Belgium.     

Production of carbonate and silica nano-particles in stirred bead milling

This paper presents the experimental results of the mechanical production of silica and carbonate colloidal particles below 100 nm using two types of stirred bead mills (i.e., DCP Superflow 12 and PML H/V). It is shown that the stirred bead mill with very small beads can be used as an efficient equipment for the production of the colloidal particles in nanoscale from the feed materials of several microns in sizes at high energy consumptions. The DCP Superflow mill with high power densities is superior for the effective size reduction and production rate, compared to the conventional PML H/V mill with lower power densities. The smaller particles could be produced by the DCP Superflow mill at the same level of high energy inputs as from the PML H/V mill. The “grinding limit” for the processes in the mills has been discussed.     

Natural and Post-Urbanization Signatures of Hypoxia in Two Basins of Puget Sound: Historical Reconstruction of Redox Sensitive Metals and Organic Matter Inputs

Hypoxia has been observed in Hood Canal, Puget Sound, WA, USA since the 1970s. Four long sediment cores were collected in 2005 and age-dated to resolve natural and post-urbanization signatures of hypoxia and organic matter (OM) sources in two contrasting basins of Puget Sound: Main Basin and Hood Canal. Paleoecological indicators used for sediment reconstructions included pollen, stable carbon and nitrogen isotopes (??¹³C and ??¹⁵N), biomarkers of terrestrial OM (TOM), biogenic silica (BSi), and redox-sensitive metals (RSM). The sedimentary reconstructions illustrated a gradient in RSM enrichment factors as Hood Canal > Main Basin, southern > northern cores, and pre-1900s > 1900?C2005. The urbanization of Puget Sound watersheds during the 1900s was reflected as shifts in all the paleoecological signatures. Pollen distributions shifted from predominantly old growth conifer to successional alder, dominant OM signatures recorded a decrease in the proportion of marine OM (MOM) concomitant with an increase in the proportion of TOM, and the weight % of BSi decreased. However, these shifts were not coincidental with an overall increase in the enrichment of RSM or ??¹⁵N signatures indicative of cultural eutrophication. The increased percentage of TOM was independently verified by both the elemental ratios and lignin yields. In addition, isotopic signatures, BSi, and RSMs all suggest that OM shifts may be due to a reduction in primary productivity rather than an increase in OM regeneration in the water column or at the sediment/water interface. Therefore, the reconstructions suggested the Hood Canal has been under a more oxygenated ??stance?? during the twentieth century compared to prior periods. However, these 2005 cores and their resolutions do not encompass the period of high resolution water column measurements that showed short-lived hypoxia events and fish kills in Hood Canal during the early twenty-first century. The decoupling between the increased watershed-scale anthropogenic alterations recorded in the OM signatures and the relatively depleted RSM during the twentieth century suggests that physical processes, such as deep-water ventilation, may be responsible for the historical variation in oxygen levels. Specifically, climate oscillations may influence the ventilation and/or productivity of deep water in Puget Sound and particularly their least mixed regions.     

Magnetic Characterization of Amphibolites from the Fomopéa Pluton (West Cameroon): Their Implication in the Pan-African Deformation of the Central African Fold Belt

The Fomopea granitic pluton is emplaced in gnessic and amphibolitic basement.These gneissic and amphibolitic basement rocks are represented in the pluton's body as sub-rounded,elongated or stretched xe...     

Stately home geology: Kelmscott Manor,Oxfordshire, UK

Kelmscott Manor on the banks of the Upper Thames in Oxfordshire is a place of pilgrimage for social historians and conversationalists as well as those who simply want to turn the clock back to a rural England long departed. The manor was leased to William Morris in 1871 to be his family home until long after his death in 1896—their escape from the hectic daily life in London. At that point, Morris spent the previous 10 years building up the crafts business for which he is best known, the patterned textiles and wallpaper designs and the basic wooden furniture we associate with the Arts and Crafts Movement. It can be difficult to remember that much of the respected craftwork was generated in the East End of London by gifted craftsmen.     

The removal kinetics of dissolved organic matter and the optical clarity of groundwater

Concentrations of dissolved organic matter (DOM) and ultraviolet/visible light absorbance decrease systematically as groundwater moves through the unsaturated zones overlying aquifers and along flowpaths within aquifers. These changes occur over distances of tens of meters (m) implying rapid removal kinetics of the chromophoric DOM that imparts color to groundwater. A one-compartment input-output model was used to derive a differential equation describing the removal of DOM from the dissolved phase due to the combined effects of biodegradation and sorption. The general solution to the equation was parameterized using a 2-year record of dissolved organic carbon (DOC) concentration changes in groundwater at a long-term observation well. Estimated rates of DOC loss were rapid and ranged from 0.093 to 0.21 micromoles per liter per day (μM d^?1), and rate constants for DOC removal ranged from 0.0021 to 0.011 per day (d^?1). Applying these removal rate constants to an advective-dispersion model illustrates substantial depletion of DOC over flow-path distances of 200 m or less and in timeframes of 2 years or less. These results explain the low to moderate DOC concentrations (20–75 μM; 0.26–1 mg L^?1) and ultraviolet absorption coefficient values (a ₂₅₄?<?5 m^?1) observed in groundwater produced from 59 wells tapping eight different aquifer systems of the United States. The nearly uniform optical clarity of groundwater, therefore, results from similarly rapid DOM-removal kinetics exhibited by geologically and hydrologically dissimilar aquifers.     

Establishing constraints on groundwater ages with Cl,C, H,and noble gases: A case study in the eastern Paris basin,France

Groundwaters from the Tithonian/Kimmeridgian, Oxfordian and Upper Dogger aquifers, within the eastern part of the Paris basin (France), were characterised using ³H, ¹⁴C and ³⁶Cl, and noble gases tracers, to evaluate their residence times and determine their recharge period. This information is an important prerequisite to evaluating the confinement properties of the Callovo-Oxfordian clay formation sandwiched between the Oxfordian aquifer and the Dogger aquifer, currently being investigated by the French nuclear waste management agency (Andra) for radioactive waste disposal. Data presented in this paper are used to test 4 hypotheses.