Logging in deep water wells in central Jutland, Denmark

During a search for unpolluted resources, new wells have been drilled to a deep confined aquifer in central Jutland. Since little is known about the extent and vulnerability of the deep reservoir, geophysical logging was used to supplement hydraulic well-testing. Gamma-ray, SP and resistivity logs were recorded in the boreholes. Gamma-logs were also recorded in two cased wells. Analysis of the logs, combined with information from samples, shows an unconfined aquifer of quartz and mica sand to a depth of about 55 m at Grindsted. Below this level there is a 40 m thick aquitard with an apparent southerly dip. The aquitard is composed of interbedded sand, silt and clay. The deep confined aquifer extends from 95 to 110 m below the surface at Grindsted. Both the aquitard and the deep aquifer are provisionally dated as Early/Middle Miocene. The electrical logs discriminate well between sand, silt and clay beds. If a suitable mud is used in the well it is possible to calculate the formation water resistivities in good agreement with water samples obtained after completion. From the resistivity logs formation factors were calculated in the range 3–5 using no-invasion departure curves. The high content of heavy mineralsin the Tertiary deposits makes it impossible to obtain precise lithological information from the gamma-ray log. On the other hand this log provides clear markers for identifying the hydrogeological units in the well-bores.     

THE EFFECT OF SYNOPTIC SCALE WEATHER SYSTEMS ON SUB‐SURFACE SOIL TEMPERATURES IN A DIURNAL FROST ENVIRONMENT: PRELIMINARY OBSERVATIONS FROM SUB‐ANTARCTIC MARION ISLAND

Marion Island in the South Indian Ocean has a maritime climate dominated by diurnal frost processes in the landscape. We test the hypothesis that synoptic time‐scale measurements are essential in understanding the drivers of diurnal frost processes. Preliminary results from automated microclimate measurements in a polar desert habitat show that diurnal soil surface temperatures on Marion Island are influenced by a complex interaction of radiation balance, air mass circulation, cloud cover and snow. The passage of synoptic scale weather systems influences soil thermal characteristics through changes in dominance of the radiation budget. Soil frost on Marion appears to be dependent on clear skies, while synoptic weather systems affect the duration and intensity of soil frost processes and non‐radiative heat fluxes. Air circulation patterns at Marion Island influence diurnal scale temperature fluctuations and its direct and indirect interactions with ecosystem processes. The data suggest that in a maritime sub‐Antarctic environment the climatic drivers of soil frost occur at a finertemporal resolution than for seasonal and permafrost environments and needs to be measured at a diurnal time‐scale to be meaningful.     

The Cocos and Carnegie Aseismic Ridges: a Trace Element Record of Long-term Plume-Spreading Center Interaction

The aseismic Cocos and Carnegie Ridges, two prominent bathymetricfeatures in the eastern Pacific, record 20 Myr of interactionbetween the Galápagos hotspot and the adjacent GalápagosSpreading Center. Trace element data determined by inductivelycoupled plasma-mass spectrometry in >90 dredged seamountlavas are used to estimate melt generation conditions and mantlesource compositions along the ridges. Lavas from seamount provinceson the Cocos Ridge are alkalic and more enriched in incompatibletrace elements than any in the Galápagos archipelagotoday. The seamount lavas are effectively modeled as small degreemelts of a Galápagos plume source. Their eruption immediatelyfollows the failure of a rift zone at each seamount province'slocation. Thus the anomalously young alkalic lavas of the CocosRidge, including Cocos Island, are probably caused by post-abandonmentvolcanism following either a ridge jump or rift failure, andnot the direct activity of the Galápagos plume. The seamountshave plume-like signatures because they tap underlying mantlepreviously infused with Galápagos plume material. Whereasplume heterogeneities appear to be long-lived, tectonic rearrangementsof the ridge plate boundary may be the dominant factor in controllingregional eruptive behavior and compositional variations. KEY WORDS: mantle plume; mid-ocean ridge; Galápagos; abandoned rift; partial melting of the mantle     

Effect of Clay Minerals on Transport of Surfactants Dispersed Multi-walled Carbon Nanotubes in Porous Media

Clay minerals can hinder the transport of various contaminants in soil and aquifer, but how clay minerals affect the transport of nanoparticles in aquifers has not been investigated in depth. In this paper, the transport of surfactants dispersed multi-walled carbon nanotubes (MWCNTs) in well-defined quartz sand and mixtures of quartz sand and clay minerals (kaolinite and montmorillonite) with varying ionic strengths was studied. Sodium dodecyl benzenesulfonate (SDBS) and octyl-phenol-ethoxylate (TX100) MWCNT suspensions can migrate through quartz sand easily, but the presence of less than 2% w/w clay minerals in quartz sand can significantly hinder the transport of MWCNT suspensions, especially at high ion strength (0.6 mM CaCl2). The inhibition mechanism of clay minerals for surfactant-dispersed MWCNTs in porous media is the interception of MWCNTs. Kaolinite has stronger inhibition effect for MWCNTs transport than montmorillonite because more kaolinite can be retained in the quartz sand. Adsorption of surfactants by clay minerals does not affect the transport of MWCNTs significantly. This finding is important for the environmental assessment of MWCNT transport risks in soils and aquifers.     

Mineral Equilibria in the Searles Lake Evaporites, California

The Searles Lake evaporites (late Quaternary) consist of salineand mud layers permeated by brines. Two mineral pairs (gaylussite-pirssonite,mirabilite-thenardite) are used as indicators of relative aH₂othroughout the stratigraphic column. Variations are attributedmostly to changes in brine salinity and partly to temperature. These aH₂o-sensitive minerals locally coexist with trona, nahcolite,burkeite, northupite, tychite, hanksite, and aphthitalite, whichare sensitive to both aH₂o and a_co. Such assemblages permitconstruction of schematic isothermal aH₂o-a_co, diagrams. Fieldboundary sequences are derived from both theoretical considerationsand observed assemblages; their slopes are determined by thestoichiometry of possible reactions. Predicted assemblages invariablyagree with observed assemblages. By means of these diagrams, present-day lateral and stratigraphicvariations in relative aH₂o and aco₂ in the deposit are reconstructed.They show that aH₂o and a_co2 vary independently. Many of thepresent activities reflect depositional conditions; some indicatepost-depositional events.     

Low-Temperature, Low-Pressure Metamorphism of Mn-rich Rocks in the Lienne Syncline, Venn--Stavelot Massif (Belgian Ardennes), and the Role of Carpholite

Low-grade Mn-rich metamorphic rocks of the Lienne syncline (westernpart of the Venn–Stavelot Massif, Belgian Ardennes) havebeen re-examined to evaluate the petrological significance ofcarpholite proper, Mn^2$ Al₂[Si₂O₆](OH)₄. Metamorphic P–Tconditions of these rocks are estimated to be {small tilde}300C1–2 kbar, which is in accordance with the exclusive occurrenceof carpholite in low-P rocks such as hydrothermal environmentselsewhere. Carpholite of the Lienne syncline exclusively occursin quartz-rich segregations. Its composition is close to end-member.Thermodynamic calculations confirm that carpholite is a stablephase at low-pressure–low-temperature conditions, in contrastto ferro- and magnesiocarpholite, which are high-pressure minerals.No information is available on the high-P behaviour of carpholite.The occurrence of carpholite is partly closely associated withspessartine-bearing country rocks, or carpholite is alteredto assemblages with spessartine, sudoite, chlorite, muscoviteand paragonite. Spessartine in these rocks contains minor amountsof hydrogarnet component {(H/4)/[Si$(H/4)] = 0.03–0.06}.The presence of carpholite-spessartine assemblages in theselow-P rocks is in contrast to high-pressure metamorphic rocksfrom other areas, where parageneses such as fem/magnesiocarpholite–chloritoidor magnesiocarpholite–chlorite–kyanite occur. Theappearance of carpholite–garnet assemblages in low-P Mn-richrocks can be explained by contrasting phase relations becauseof a high Mn–Mg partition coefficient between the mineralsunder consideration. In rhodo-chrosite-bearing veins in theLienne syncline, nearly complete replacement of carpholite byspessartine and chlorite is due to the continuous reaction carpholite$ rhodochrosite $ quartz = spessartine $ chlorite $ H₂O $ CO₂,which defines a very low X_co, in the temperature range underconsideration. It is suggested that spessartine (possibly containingsome hydrogarnet component), during prograde metamorphism atlow pressure, becomes stable at a temperature of {small tilde}300C KEY WORDS: carpholite; spessartine; sudoite; Venn–Stavelot Massif; Ardemes ^*Corresponding author. Fax: x49/531/3918131. e-mail: t.theye{at}tu.bs.de     

The Villalbeto de la Peña meteorite fall: I. Fireball energy,meteorite recovery,strewn field,and petrography

Abstract— An impressive daylight fireball was observed from Spain, Portugal, and the south of France at 16h46m45s UTC on January 4, 2004. The meteoroid penetrated into the atmosphere, generating shock waves that reached the ground and produced audible booms. The associated airwave was recorded at a seismic station located 90 km north of the fireball trajectory in Spain, and at an infrasound station in France located 750 km north‐east of the fireball. The absolute magnitude of the bolide has been determined to be ?18 ± 1 from a casual video record. The energy released in the atmosphere determined from photometric, seismic, and infrasound data was about 0.02 kilotons (kt). A massive fragmentation occurred at a height of 28 ± 0.2 km, resulting in a meteorite strewn field of 20 × 6 km. The first meteorite specimen was found on January 11, 2004, near the village of Villalbeto de la Peña, in northern Palencia (Spain). To date, about 4.6 kg of meteorite mass have been recovered during several recovery campaigns. The meteorite is a moderately shocked (S4) L6 ordinary chondrite with a cosmic‐ray‐exposure age of 48 ± 5 Ma. Radioisotope analysis shows that the original body had a mass of 760 ± 150 kg, which is in agreement with the estimated mass obtained from photometric and seismic measurements.     

Chronology of dimict breccias and the age of South Ray crater at the Apollo 16 site

Abstract— We report the noble gas isotopic abundances of five dimict breccias and one cataclastic anorthosite that were collected at the Apollo 16 landing site. Orbital and surface photographs indicate that rays from South Ray crater, an almost 1 km wide young crater in the Cayley plains, extend several kilometers from their source into the area that was sampled by the Apollo 16 mission. Previous studies have shown that South Ray crater formed 2 Ma ago and that a large number of rocks might originate from this cratering event. On the basis of cosmic-ray produced nuclei, we find that the six rocks investigated in this work yield the same lunar surface exposure age. Using literature data, we recalculate the exposure ages of additional 16 rocks with suspected South Ray crater origin and obtain an average exposure age of 2.01 ± 0.10 Ma. In particular, all nine dimict breccias (a type of rock essentially restricted to the Apollo 16 area consisting of anorthosite and breccia phases) dated until now yield an average ejection age of 2.06 ± 0.17 Ma. We conclude that they must originate from the Cayley formation or from bedrock underlying the Cayley plain. We determined the gas retention ages for the dimict breccias based on the ⁴⁰K-⁴⁰Ar and U,Th-¹³⁶Xe dating methods: rock 64425 yields a ⁴⁰K-⁴⁰Ar age of 3.96 Ga and rock 61016 a U,Th-¹³⁶Xe age of 3.97 Ga. These results, together with ³⁹Ar-⁴⁰Ar ages obtained by other workers for rocks 64535 (3.98 Ga) and 64536 (3.97 Ga), show that the dimict breccias formed 3.97 Ga ago.     

History of lunar meteorites Queen Alexandra Range 93069, Asuka 881757, and Yamato 793169 based on noble gas isotopic abundances,radionuclide concentrations,and chemical composition

Abstract— We investigated the characteristics and history of lunar meteorites Queen Alexandra Range 93069, Yamato 793169 and Asuka 881757 based on the abundances of all stable noble gas isotopes, the concentrations of the radionuclides ¹⁰Be, ²⁶Al, ³⁶Cl, and ⁸¹Kr, and the abundances of Mg, Al, K, Ca, Fe, Cl, Sr, Y, Zr, Ba, and La. Based on the solar wind and cosmic-ray irradiations, QUE 93069 is the most mature lunar meteorite studied up to now. The ⁴⁰Ar/³⁶Ar ratio of the trapped component is 1.87 ± 0.16. This ratio corresponds to a time when the material was exposed to solar and lunar atmospheric volatiles ～400 Ma ago. On the other hand, Yamato 793169 and Asuka 881757 contain very little or no solar noble gases, which indicates that these materials resided in the top layer of the lunar regolith only briefly or not at all. For all lunar meteorites, we observe a positive correlation of the concentrations of cosmic-ray produced with trapped solar noble gases. The duration of lunar regolith residence for the lunar meteorites was calculated based on cosmic-ray produced ²¹Ne, ³⁸Ar, ⁷⁸Kr, ⁸³Kr, and ¹²⁶Xe and appropriate production rates that were derived based on the target element abundances and the shielding indicator ¹³¹Xe/¹²⁶Xe. For QUE 93069, Yamato 793169, and Asuka 881757, we obtained 1000 ± 400 Ma, 50 ± 10 Ma, and <1 Ma, respectively. Both Asuka 881757 and Yamato 793169 show losses of radiogenic ⁴He from U and Th decay and Yamato 793169 also ⁴⁰Ar loss from K-decay. For Asuka 881757, we calculate a K-Ar gas retention age of 3100 ± 600 Ma and a ²⁴⁴Pu-¹³⁶Xe fission age of 4240 ± 170 Ma. This age is one of the oldest formation ages ever observed for a lunar basalt. The exposure history of QUE 93069 after ejection from the Moon was derived from the radionuclide concentrations: ejection 0.16 ± 0.03 Ma ago, duration of Moon-Earth transit 0.15 ± 0.02 Ma and fall on Earth <0.015 Ma ago. This ejection event is distinguished temporally from those which produced the other lunar meteorites. We conclude that six to eight events are necessary to eject all the known lunar meteorites.