The relationship of uranium isotopes to oxidation/reduction in the Edwards carbonate aquifer of Texas

The concentration of dissolved uranium and²³⁴U/²³⁸U alpha activity ratio (“A.R.”) were determined in water samples from 23 locations in the Edwards carbonate aquifer of south central Texas by isotope dilution methods and alpha spectrometry. This aquifer consists of two parts, an updip oxidized portion and a downdip reduced portion. At some places the boundary is associated with faulting and at others it is not. The boundary between the two portions of the aquifer can be located by an abrupt change in chemical properties of the water such as a large increase in concentration of Cl^?, SO₄^2? and total dissolved solids, the presence of H₂S and a decrease in Eh in moving from updip to downdip. Compared with the oxidized samples, the uranium concentration is much lower and the A.R. higher in the reduced samples so that the uranium from each portion falls in a distinct field. The oxidized aquifer samples show very little variation in the measured uranium parameters even though, in some cases, there is evidence that the water has flowed through some tens of kilometers of aquifer. Samples collected near the boundary at those places not associated with faulting yield dissolved uranium values which fall in neither field and which, for the most part, cannot result from mixing of the oxidized and reduced waters. These samples probably result from changes in location of the oxidation-reduction boundary.     

Volume relations between palagonite and authigenic minerals in hyaloclastites,and its bearing on the rate of palagonitization

Hyaloclastites are particularly suitable material for palagonitization. This process of alteration leads to the formation in broadly equal proportions of authigenic minerals and palagonite. When the palagonitization process reachs the stage where voids between fragments, and vesicles within fragments are completely filled with authigenic minerals so as to make the rock more or less impermeable to water, the rate of the palagonitization process is thought to slow down considerably. Depending upon the original texture and porosity of the hyaloclastite, sideromelane may or may not remain at this stage. This may explain why sideromelane, which otherwise would have been completely palagonitized, can be found in relatively old hyaloclastites. Further, study of palagonitization taking place around glassy vesicle walls strongly suggests that the process is post-cruptional, being initiated at the time the glass encounters an equeous environment, and proceeds at low temperatures.     

Magma dynamics, crystallization, and chemical differentiation of the 1959 Kilauea Iki lava lake, Hawaii, revisited

Using constraints from an extensive database of geological and geochemical observations along with results from fluid mechanical studies of convection in magma chambers, we identify the main physical processes at work during the solidification of the 1959 Kilauea Iki lava lakes. In turn, we investigate their quantitative influence on the crystallization and chemical differentiation of the magma, and on the development of the internal structure of the lava lake. In contrast to previous studies, vigorous stirring in the magma, driven predominately by the descent of dense crystal-laden thermal plumes from the roof solidification front and the ascent of buoyant compositional plumes due to the in situ growth of olivine crystals at the floor, is predicted to have been an inevitable consequence of very strong cooling at the roof and floor. The flow is expected to have caused extensive but imperfect mixing over most of the cooling history of the magma, producing minor compositional stratification at the roof and thermal stratification at the floor. The efficient stirring of the large roof cooling is expected to have resulted in significant internal nucleation of olivine crystals, which ultimately settled to the floor. Additional forcing due to either crystal sedimentation or the ascent of gas bubbles is not expected to have increased significantly the amount of mixing. In addition to convection in the magma, circulation driven by the convection of buoyant interstitial melt in highly permeable crystal-melt mushes forming the roof and the floor of the lava lake is envisaged to have produced a net upward flow of evolved magma from the floor during solidification. In the floor zone, mush convection may have caused the formation of axisymmetric chimneys through which evolved magma drained from deep within the floor into the overlying magma and potentially the roof. We hypothesize that the highly evolved, pipe-like ‘vertical olivine-rich bodies’ (VORBs) [Bull. Volcanol. 43 (1980) 675] observed in the floor zone, of the lake are fossil chimneys. In the roof zone, buoyant residual liquid both produced at the roof solidification front and gained from the floor as a result of incomplete convective mixing is envisaged to have percolated or ‘leaked‘ into the overlying highly-permeable cumulate, displacing less buoyant interstitial melt downward. The results from Rayleigh fractionation-type models formulated using boundary conditions based on a quantitative understanding of the convection in the magma indicate that most of the incompatible element variation over the height of the lake can be explained as a consequence of a combination of crystal settling and the extensive but imperfect convective mixing of buoyant residual liquid released from the floor solidification front. The remaining chemical variation is understood in terms of the additional influences of mush convection in the roof and floor on the vertical distribution of incompatible elements. Although cooling was concentrated at the roof of the lake, the floor zone is found to be thicker than the roof zone, implying that it grew more quickly. The large growth rate of the floor is explained as a consequence of a combination of the substantial sedimentation of olivine crystals and more rapid in situ crystallization due to both a higher liquidus temperature and enhanced cooling resulting from imperfect thermal and chemical mixing.     

A reply to the discussion of the [I,S] diagram by V.M. Oversby

Despite Oversby's [1] belief, the [I,S] diagram [2] is as much sensitive as the [α, β] diagram since both of them are based on the same isotopic evolution equations. Also, we do insist again on the greater simplicity of the [I,S] diagram in process in Pb-Pb data for whole rock series to study global isotopic evolution, and most particularly in the case where initial isotopic composition for the series considered cannot be measured.     

Distribution and significance of hydrothermal alteration minerals in the Tuzla hydrothermal system, Çanakkale, Turkey

Hydrothermal alteration zones have been investigated by X-ray diffraction, mineralogical–petrographical techniques, and geochemical analysis. Examination of cores and cuttings from two drill sites, obtained from a depth of about 814–1020 m, show that the hydrothermal minerals occuring in the rock include: K-feldspar, albite, chlorite, alunite, kaolinite, smectite, illite, and opaque minerals.In the studied area, silicified, smectite, illite, alunite, and opal zones have been recognized. These alteration mineral assemblages indicate that there are geothermal fluids, which have temperatures of 150–220°C in the reservoir.The distribution of the hydrothermal minerals shows changes in the chemical composition of the hydrothermal fluid, which are probably due not only to interaction with host rock, but also to dilution of the Na–K–Cl-rich hydrothermal fluid of the deep reservoir by cold sea water at shallow levels. Geochemical analyses of the solid and liquid phases indicate that the hydrothermal fluids of the Tuzla geothermal system are in equilibrium with alteration products.The tectonic structure of the studied area is caused by NW–SE and NE–SW directional forces. The volcanic rocks where hydrothermal zones are observed in the studied area are of Lower–Middle Miocene age comprise latite, andesite, dacite, rhyolite-type lavas, tuff, and ignimbrites.     

Inhibition of larval swimming activity of the coral (Platygyra acuta) by interactive thermal and chemical stresses

This study examined the interactive effects of copper and elevated temperature and subsequent depuration on Platygyra acuta coral larvae. Larval mortality and motility were significantly affected by copper alone (70% and 100% inhibition respectively). Their respective lethal/inhibitory concentration (LC₅₀/IC₅₀) were 10–130% and 86–193% higher than those reported for other larvae. Temperature (ambient, 27 °C and elevated, 30 °C) alone and the combination of temperature and copper did not significantly affect both endpoints. This study provides the first quantitative data on depuration effect on resumption of larval motility after copper exposure, although no sign of larval recovery was observed. These findings suggest that the effects of copper pollution outweigh the thermal tolerance of coral larvae. High LC₅₀ and IC₅₀ recorded may be unique for corals from marginal reefs like Hong Kong which have already been exposed to high levels of copper pollution.     

Theoretical grain size limits for single-domain,pseudo-single-domain and multi-domain behavior in titanomagnetite (x = 0.6) as a function of low-temperature oxidation

A theoretical model of grain size variation of domain transitions in titanomagnetite (x = 0.6) as a function of oxidation (z) is presented. The superparamagnetic (SP) to single-domain (SD) transition d_s, the SD to two-domain (TD) transition d₀, the TD to three-domain (3D) transition and the pseudo-single domain (PSD) to multi-domain (MD) transition are calculated as a function of z. It is shown that all the transition grain sizes increase with z, except for the PSD-MD transition for z > 0.6. The calculations predict that d_s increases from 0.044 to 0.197 μm, d₀ increases from 0.54 to 13 μm, the TD-3D transition increases from 1.6 to 49 μm as z varies from 0 to 0.8. The PSD-MD transition increases from 42 μm at z = 0 to 150 μm at z = 0.6, whereas between z = 0.6 to z = 0.8, the PSD-MD transition decreases to 49 μm. Qualitatively, the model explains some of the trends in magnetic properties of submarine basalts with low-temperature oxidation. Quantitatively, the model does give reasonable estimates of the PSD-MD boundary and d₀, which are close to the experimental values for x = 0.6 and z = 0. Furthermore, the model predicts that psarks or two-domain grains could be the major contributors to the remanence of oxidized submarine pillow basalts.     

Estimating thermal inflow to El Chichón crater lake using the energy-budget,chemical and isotope balance approaches

El Chichón crater lake appeared immediately after the 1982 catastrophic eruption in a newly formed, 1-km wide, explosive crater. During the first 2 years after the eruption the lake transformed from hot and ultra-acidic caused by dissolution of magmatic gases, to a warm and less acidic lake due to a rapid “magmatic-to-hydrothermal transition” — input of hydrothermal fluids and oxidation of H₂S to sulfate. Chemical composition of the lake water and other thermal fluids discharging in the crater, stable isotope composition (δD and δ¹⁸O) of lake water, gas condensates and thermal waters collected in 1995–2006 were used for the mass-balance calculations (Cl, SO₄ and isotopic composition) of the thermal flux from the crater floor. The calculated fluxes of thermal fluid by different mass-balance approaches become of the same order of magnitude as those derived from the energy-budget model if values of 1.9 and 2 mmol/mol are taken for the catchment coefficient and the average H₂S concentration in the hydrothermal vapors, respectively. The total heat power from the crater is estimated to be between 35 and 60 MW and the CO₂ flux is not higher than 150 t/day or ~ 200 gm^− 2 day^− 1.     

Trophic ecology of the swimming crab Polybius henslowii Leach, 1820 in Galician and Cantabrian Seas: Influences of natural variability and the Prestige oil spill

Diet and feeding intensity of the portunid crab Polybius henslowii were studied during the spring of 2004 along Galician and Cantabrian continental shelves (NW Iberian Peninsula) between 78 and 287 m. The area had been affected by the Prestige oil spill in November 2002, with different sectors at different levels of pollution: highest in between Miño River and Cape Finisterre (MF) and from there to Estaca de Bares Point (FE) and lowest from Estaca to Cape Peñas (EP). From 37272 specimens collected in 59 bottom hauls, 342 were analysed for stomach fullness and diet composition. Stomach fullness was lower in FE, but with no significant differences among sectors. Diet was a mixture of pelagic and benthic prey: cephalopods (Ilex coindetti), brachyurans (P. henslowii) and polychaetes (Glycera sp.). Other prey were beloniform eggs and fish remains. Two stress markers were also studied in some specimens: Acetylcholinesterase (a neurotoxicity marker) varied among sampled areas, while lipid peroxidation (an oxidative stress marker) did not. Changes in trophic variables, distribution and density were analysed in relation to depth, surface and bottom T, surface Chl a from satellite imagery and tar aggregate concentration in sediments. Along Galician and Cantabrian coasts prey availability, linked to productivity level, seems to be the main factor affecting P. henslowii diet and distribution. Interannual abundance variability seems to be controlled by large-scale climatic conditions (NAO index). This natural variability masks possible effects induced by the oil spill.     

Responses of benthic macrofauna and biogeochemical fluxes to various levels of mussel biodeposition: An in situ “benthocosm” experiment

An in situ experiment was done to evaluate the dose-dependent response of mussel biodeposition on benthic communities and biogeochemical fluxes. Natural benthic communities were exposed to 7 different levels of mussel biodeposition (equivalent to that produced by 0-764 mussels m⁻²) over 50 days. Benthic communities responded as predicted from the Pearson, T.H., Rosenberg, R., 1978. Macrobenthic succession in relation to organic enrichment and pollution of the marine environment. Oceanogr. Mar. Biol. Annu. Rev. 16, 229-311 model of organic enrichment. Total abundance and species richness decreased with increasing biodeposition. The abundance and biomass of opportunistic species (Capitella spp.) increased in the mesocosms subject to the greatest biodeposition. Sensitive species Tellina agilis and Pherusa plumosa tended to decrease in abundance and biomass with increasing biodeposition. The biotic index M-AMBI responded clearly to increased biodeposition and may be a useful tool for assessing the effect of mussel biodeposition on the benthic environment. These results are important for the construction of predictive models for determining environmental carrying capacity for bivalve aquaculture.     

Paleomagnetism of the type Pliocene/Pleistocene boundary section at Santa Maria de Catanzaro,Italy, and the problem of post-depositional precipitation of magnetic minerals

In order to assist in global correlation of the Pliocene/Pleistocene boundary, a paleomagnetic survey has been made of the world type section for the boundary, in Calabria, Italy. A total of 116 specimens from 36 sites were collected from the section, which as sampled is about 30 m thick. All sites possess stable remanent magnetism and northern hemisphere virtual geomagnetic poles, consistent with deposition during a period of normal polarity. If this period was during the Gilsa event, a minimum sedimentation rate of 17 cm per 1000 years would be required. Since a normal polarity chemical overprint, acquired during the last 0.69 m.y. could also explain the data, thermomagnetic analyses were made of selected samples. The results show the presence of highly unstable superparamagnetic material, which is most likely a product of post-depositional chemical precipitation. This observation enhances the possibility that any longer-duration precipitation could have created coarse and thus magnetically more stable components, the effects of which could not be readily distinguished from the original remanent magnetism.The difficulties of distinguishing between original depositional remanent magnetism and post-depositional chemical remanent magnetism, in outcropping marine sediments, as well as the large range of possible natural causes of the latter, is summarized in the form of a discussion of feasible Eh and pH changes occurring between original deposition at upper bathyal dephts and final sampling above sea level. It is considered that, in the absence of experimental means to distinguish the roles of original and chemically overprinted paleomagnetic signals, similarity of magnetic polarity stratigraphy between sections of sediments representing different paleoenvironments and sedimentation rates is a necessary if insufficient requirement for diagnosis of real geomagnetic behavior during deposition, as opposed to posidepositional effects.     

Comparison of the sediment composition in relation to basic chemical,physical,and geological factors

Sediment constitutes an interesting and valuable material for observation of human impact on the environment.Based on the sediment core samples in two Tatra Mountains lakes,determination of the selected elements(including cesium 137 radionuclide activity and heavy metals' concentrations) and dating of the obtained layers by the lead 210 method,chemometric analysis of the resulting data set was done.It was established,as a result of Cluster Analysis,that the variability of the determined parameters was distinct in the lakes with much higher concentrations of heavy metals in Smreczynski staw lake.Also,the influence of human activity(long distance transport of contaminants) is notable on the north slopes of the Tatras(Smreczynski staw lake) comparing to Popradske pleso lake.The examined elements can be divided into two groups-natural to the site origin(iron,manganese,and magnesium),and elements whose accumulation in the sediments can be related(at least in part) to human activity(~(137)Cs,zinc,copper,cadmium,lead,and chromium).The results confirm the existence of the so called "screen effect",meaning that the Tatra Mountains' crest delimits to a considerable extent further transport of pollutants to the south side of the Tatra Mountains slopes.     

Mercury in wahoo, Acanthocybium solandri, from offshore waters of the southeastern United States and the Bahamas

Wahoo, Acanthocybium solandri, are predatory oceanic fish that occur and are harvested in all tropical and subtropical oceans. Total mercury concentrations analyzed in dorsal muscle tissue of 208 wahoo from offshore waters of the southeastern United States and the Bahamas ranged from 0.021 to 3.4 mg/kg (wet weight), with a mean of 0.50 mg/kg (± 0.595 SD). Analyses indicated significant positive linear relationships between mercury and length, as well as, age of wahoo. The piscivorous nature, generally high trophic position, fast growth rate, and associated high metabolism of wahoo within tropical offshore pelagic environments may lead to comparatively higher concentrations of mercury over relatively short time periods. Mercury in wahoo, a highly mobile species consisting of one world-wide population, is regionally influenced by large-scale spatial differences in available mercury in selected prey fish species - many of which have been found to contain relatively high concentrations of mercury.     

Isolation and characterization of a novel hydrocarbon-degrading bacterium Achromobacter sp. HZ01 from the crude oil-contaminated seawater at the Daya Bay,southern China

Microorganisms play an important role in the biodegradation of petroleum contaminants, which have attracted great concern due to their persistent toxicity and difficult biodegradation. In this paper, a novel hydrocarbon-degrading bacterium HZ01 was isolated from the crude oil-contaminated seawater at the Daya Bay, South China Sea, and identified as Achromobacter sp. Under the conditions of pH 7.0, NaCl 3% (w/v), temperature 28 °C and rotary speed 150 rpm, its degradability of the total n-alkanes reached up to 96.6% after 10 days of incubation for the evaporated diesel oil. Furthermore, Achromobacter sp. HZ01 could effectively utilize polycyclic aromatic hydrocarbons (PAHs) as its sole carbon source, and could remove anthracene, phenanthrene and pyrence about 29.8%, 50.6% and 38.4% respectively after 30 days of incubation. Therefore, Achromobacter sp. HZ01 may employed as an excellent degrader to develop one cost-effective and eco-friendly method for the bioremediation of marine environments polluted by crude oil.     

Observations on the relations of some physico-chemical features and DVM of Paradiaptomus africanus in Lakes Bishoftu-Guda and Hora-Arsedi, Bishoftu, Ethiopia

Bishoftu-Guda and Hora-Arsedi are two crater lakes found in close proximity with each other in a locality known as Bishoftu, 50 km south of Addis Ababa, capital city of Ethiopia. The main objective of this study was to measure some physico-chemical features and discuss their relations with the dial vertical migration (DVM) behavior of Paradiaptomus africanus, the dominant macrozooplankton in both lakes. By depth measurements of dissolved oxygen and temperature showed that there is persistent stratification in these lakes. Secchi depth was shallow and the water chemistry as shown from conductivity and chemical analysis were comparable between the two lakes. These data were compared with previous reports to bring out the overall limnological scenario of the two lakes. Then, the relations of these data to the DVM of P. africanus in both lakes were discussed. It was found out that DVM of P. africanus occurred in Lakes Bishoftu-Guda and Hora-Arsedi mostly within a range of about 3 m very likely for two reasons, namely avoidance of solar radiation and ultimately vertebrate visual predation. However, the depth of DVM of P. africanus was found to be very shallow probably due to high water turbidity that provided this calanoid sufficient refuge by daylight from both dangers, while at the same time P. africanus remained in warm and oxygen-rich waters. Temperature was not much of a factor affecting DVM as it remained above 19 °C at all depths. As this study was conducted over limited time frames, seasonal studies regarding changes in physico-chemical parameters, plankton, vertebrate predators and human interference were recommended so that the information so gathered could be used in the management of the study lakes.     

Stability relations of ilmenite and ulvöspinel in the Fe-Ti-O system and application of these data to lunar mineral assemblages

The fO₂ stability relations of ilmenite and ulvöspinel were determined using C-O H-N gas-flow apparatus with fO₂ measured by a solid ceramic (calcia-zirconia) oxygen electrolyte cell. For Fe+TiO₂ + 1/2 O₂ =FeTiO₃ (from 850°–1050°C), 1/2 log fO₂=(−11,250/T) + 0.98 and for Fe+FeTiO₃ + 1/2 O₂ =Fe₂TiO₄ (from 850°–1210°C), 1/2 logfO₂ = (−12,170/T) + 1.93. These curves lie at significantly higher values of ?O₂ than determined by previous investigators (i.e., 3/4 and1/4 order of magnitude for ilmenite and ulvöspinel, respectively). In addition, for Fe+ 2TiO₂ + 1/2 O₂ =FeTi₂O₅ (1210°C), ΔG_r⁰=−45.8 ± 0.6 kcal. The QFI curve crosses the ulvöspinel reduction curve at ∼950°C and is at lower values of fO₂ below this temperature. The occurrences of fayalite reduction to SiO₂ + Fe in lunar rock 14053, as well as a new finding of this assemblage in 14072, are evidence for extreme sub-solidus reduction, whereas ulvöspinel breakdown alone occurs under less reducing conditions. The ‘complete’ reduction of ulvöspinel to TiO₂ + Fe occurs in 2 steps: first, to ilmenite + Fe and then, however more slowly, to rutile + Fe. Thus, the presence of ulvöspinel but lack of ilmenite reduction in lunar rocks cannot be used as evidence that the fO₂ was between the associated curves — only upper limits of fO₂ can be inferred.     

Holocene activities of the Taigu fault zone, Shanxi Province, and their relations with the 1303 Hongdong M =8 earthquake

The Taigu fault zone is one of the major 12 active boundary faults of the Shanxi fault-depression system, located on the eastern boundary of the Jinzhong basin. As the latest investigation indicated, the fault zone had dislocated gully terrace of the first order, forming fault-scarp in front of the loess mesa. It has been discovered in many places in ground surface and trenches that Holocene deposits were dislocated. The latest activity was the 1303 Hongdong earthquake M=8, the fault appeared as right-lateral strike-slip with normal faulting. During that earthquake, the Taigu fault together with the Mianshan western-side fault on the Lingshi upheaval and the Huoshan pediment fault on the eastern boundary of the Linfen basin was being active, forming a surface rupture belt of 160 km in length. Moreover, the Taigu fault were active in the mid-stage of Holocene and near 7 700 aB.P. From these we learnt that, in Shanxi fault-depression system, the run-through activity of two boundary faults of depression-basins might generate great earthquake with M=8. Foundation item: Chinese Joint Seismological Science Foundation (201017). Contribution No. 2003A004, Institute of Crust Dynamics, China Earthquake Administration.     

Phase relations and P–T conditions of the Ryoke pelitic and psammitic metamorphic rocks in the Ina district, Central Japan

The Ina district of the Ryoke Belt is divided into two mineral zones, based on the mineral parageneses of the pelitic and psammitic rocks at the peak metamorphism. A biotite–muscovite zone (quartz + plagioclase + biotite + muscovite with or without K-feldspar) constitutes the northwestern part, and a biotite–cordierite–K-feldspar zone (quartz + plagioclase + biotite + cordierite + K-feldspar) comprises the central to southern and eastern parts. The isograd reaction between two mineral zones is defined by a divariant reaction: Mg-rich biotite + muscovite + quartz = Fe-rich biotite + cordierite + K-feldspar + H₂O (1), which, in the K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O (KFMASH) system, occurs at ∼ 590 °C at 0.2 GPa and 660 °C at 0.4 GPa. Fibrolite accompanied by andalusite porphyroblasts in aluminous pelitic rocks of the biotite–muscovite zone and the low-grade part of the biotite–cordierite–K-feldspar zone, suggests that sillimanite was the stable aluminosilicate at the peak metamorphic condition throughout the area. In the high-grade part of the biotite–cordierite–K-feldspar zone, fibrolite mostly occurs as inclusions in cordierite or in plagioclase. The phase relations and the compositional zoning of plagioclase in relation to fibrolite inclusions suggest that fibrolite was formed under relatively high-pressure conditions, and that partial melting took place.