Results of analyses of fluid inclusions from ODP Site 735B, Leg 118 and 176

Microthermometric and isotopic analyses of fluid inclusions in primitive olivine gabbros, oxide gabbros, and evolved granitic material recovered from Ocean Drilling Program Hole 735B at the Southwest Indian Ridge provide new insights into the evolution of C-O-H-NaCl fluids in the plutonic foundation of the oceanic crust. The variably altered and deformed plutonic rocks span a crustal section of over 1500 m and record a remarkably complex magma-hydrothermal history. Magmatic fluids within this suite followed two chemically distinct paths during cooling through the subsolidus regime: the first path included formation of CO2+CH4+H2O+C fluids with up to 43 mole% CH4; the second path produced hypersaline brines that contain up to 50% NaCl equivalent salinities. Subsequent to devolatilization, respeciation of magmatic CO2, attendant graphite precipitation, and cooling from 800°C to 500°C promoted formation of CH4-enriched fluids. These fluids are characterized by average d13C(CH4) values of -27.1+/-4.3 per mil (N=45) with associated d13C(CO2) compositions ranging from -24.9 per mil to -1.9 per mil (N=39), and average dD values of exsolved vapor of -41+/-12 per mil (N=23). In pods, veins, and lenses of highly fractionated residual material, hypersaline brines formed during condensation and by direct exsolution in the absence of a conjugate vapor phase. Entrapped CO2+CH4+H2O-rich fluids within many oxide-bearing rocks and felsic zones are significantly depleted in 13C (with d13C(CO2) values down to about -25 per mil) and contain CO2 concentrations higher than those predicted by equilibrium devolatilization models. We hypothesize that lower effective pressures in high-temperature shear zones promoted infiltration of highly fractionated melts and compositionally evolved volatiles into focused zones of deformation, significantly weakening the rock strength. In felsic-rich zones, volatile build-up may have driven hydraulic fracturing of gabbroic wall rocks resulting in the formation of magmatic breccias. Comparison of isotopic compositions of fluids in plutonic rocks from 735B, the MARK area of the Mid-Atlantic Ridge, and the Mid-Cayman Rise indicate (1) that the carbon isotope composition of the lower oceanic crust may be far more heterogeneous than previously believed and (2) that carbon-bearing species in the oceanic crust and their distribution at depth are highly variable.

Geochemical and isotopic composition of pore fluids of ODP Hole 131-808C

At the Western Nankai Trough subduction zone at ODP Site 808, chemical concentration and isotopic ratio depth profiles of D, O, Sr, and He do not support fluid flow along the décollement nor at the frontal thrust. They do, however, support continuous or periodic lateral fluid flow: (1) at the base of the Shikoku Basin volcanic-rich sediment member, situated ~140 m above the décollement, and particularly (2) below the décollement. The latter must have been rather vigorous, as it was capable of transporting clay minerals over great distances. The fluid at ~140 m above the décollement is characterized by lower than seawater concentrations of Cl- (>=18% seawater dilution). It is 18O-rich and D-poor and has a non-radiogenic, oceanic, or volcanic arc Sr isotopic signature. It originates from "volcanic" clay diagenesis. The fluid below the décollement has also less Cl- than seawater (>20% dilution), is more enriched in 18O and depleted in D than fluid, but its Sr isotopic signature is radiogenic, continentalterrigenous. The source of this fluid is located arcward, is deep-seated, where illitization of the subducted clay minerals, a mixture of terrigenous and volcanic clays, occurs. The 3He/4He ratio below the décollement points to an ~25% mantle contribution. The nature of the physical and chemical discontinuities across the décollement suggests it is overpressured and is forming a leaky "dynamic seal" for fluid flow. In contrast with the situation at Barbados and Peru, where the major tectonic features are mineralized, here, although the complex is extremely fractured and faulted, mineralized macroscopic veins, fractures, and faults are absent. Instead, mineralized microstructures are widespread, indicating a diffuse mode of dewatering.

A database of multi-year (2004-2010) quality-assured surface solar hourly irradiation measurements for the Egyptian territory

A database containing the global and diffuse components of the surface solar hourly irradiation measured from 1 January 2004 to 31 December 2010 at eight stations of the Egyptian Meteorological Authority is presented. For three of these sites (Cairo, Aswan, and El-Farafra), the direct component is also available. In addition, a series of meteorological variables including surface pressure, relative humidity, temperature, wind speed and direction is provided at the same hourly resolution at all stations. The details of the experimental sites and instruments used for the acquisition are given. Special attention is paid to the quality of the data and the procedure applied to flag suspicious or erroneous measurements is described in details. Between 88 and 99% of the daytime measurements are validated by this quality control. Except at Barrani where the number is lower (13500), between 20000 and 29000 measurements of global and diffuse hourly irradiation are available at all sites for the 7-year period. Similarly, from 9000 to 13000 measurements of direct hourly irradiation values are provided for the three sites where this component is measured. With its high temporal resolution this consistent irradiation and meteorological database constitutes a reliable source to estimate the potential of solar energy in Egypt. It is also adapted to the study of high-frequency atmospheric processes such as the impact of aerosols on atmospheric radiative transfer. In the next future, it is planned to complete regularly the present 2004-2010 database.

Composition of sediment pore water and isotopes in carbonate and benthic foraminifera at DSDP Holes 68-501, 69-505 and Site 69-504

Two sites on the southern flank of the Costa Rica Rift were drilled on DSDP Legs 68 and 69, one on crust 3.9 m.y. old and the other on crust 5.9 m.y. old. The basement of the younger site is effectively cooled by the circulation of seawater. The basement of the older site has been sealed by sediment, and an interval in the uppermost 560 meters of basement recently reheated to temperatures of 60 to 120°C. Although the thickness of the sediments at the two sites is similar (150-240 m versus 270 m), the much rougher basement topography at the younger Site 505 produces occasional basement outcrops, through which 80 to 90% of the total heat loss apparently occurs by advection of warm seawater. This seawater has been heated only slightly, however; the temperature at the base of the sediments is only 9°C. Changes in its composition due to reaction with the basement basalts are negligible, as indicated by profiles of sediment pore water chemistry. Bacterial sulfate reduction in the sediments produces a decrease in SO4 (and Ca) and an increase in alkalinity (and Sr and NH3) as depth increases to an intermediate level, but at deeper levels these trends reverse, and all of these species plus Mg, K, Na, and chlorinity approach seawater values near basement. Si, however, is higher, and Li may be lower. At the older site, Site 501/504, where heat loss is entirely by conduction, the temperature at the sediment/basement contact is 59°C. Sediment pore water chemistry is heavily affected by reaction with the basaltic basement, as indicated by large decreases in d18O, Mg, alkalinity, Na, and K and an increase in Ca with increasing depth. The size of the changes in d18O, Mg, alkalinity, Ca, Sr, and SO4 varies laterally over 500 meters, indicating lateral gradients in pore water chemistry that are nearly as large as the vertical gradients. The lateral gradients are believed to result from similar lateral gradients in the composition of the basement formation water, which propagate upward through the sediments by diffusion. A model of the d18O profile suggests that the basement at Site 501/504 was sealed off from advection about 1 m.y. ago, so that reaction rates began to dominate the basement pore water chemistry. A limestone-chert diagenetic front began to move upward through the lower sediments less than 200,000 yr. ago.

Hydrological and meteorological records from the Vernagtferner Basin - Vernagtbach station, for the years 1970 to 2001

The Vernagtferner region has a long tradition of glaciological research performed by groups from Munich. It started in 1889, when Prof. Sebastian Finsterwalder from the Technical University in Munich produced the first map of a complete glacier based on terrestrial photogrammetry. Since then, numerous maps of the glacier have been made, describing the change in surface elevation for more than a century. These maps form the basis of the geodetic method of glacier mass balance determination, which provides volume changes as average data for the period between two surveys, i.e. typically for 10 years. Since the start of the glaciological method on Vernagtferner in 1964, annual as well as winter and summer mass balance data are available continuously. But only since 1973, the construction of the Vernagtbach station, approximately 1 km below the glacier margin at that time, provided the means to record a larger number of hydrological and meteorological parameters with a temporal resolution of typically 1 hour.

137Cs concentrations in the southeastern Baltic Sea in 1997-2000

Variations of 137Cs concentration in the southeastern Baltic Sea were investigated over the period 1997-2000, i.e. in 11-14 years after the Chernobyl Nuclear Power Plant accident. Rate of "self-cleaning" proved to be very slow. Some results obtained in 1999 were almost the same as those measured after the accident, in 1986. Calculated results showed that "Chernobyl" caesium-137 would be "cleaned" in the Baltic Sea by 2020-2022. In 2000 average concentration had to be about 50-60 Bq/m**3. Sometimes mentioned concentrations were observed. In some cases higher concentrations averaging from 67 to 80 Bq/m**3 were registered in the southeastern Baltic Sea in 1999; and in some samples 137Cs concentrations were very high. They varied from 110 to 212 Bq/m**3. No steady correlation was observed between 137Cs concentration, salinity and temperature in surface water of the area. Distribution of radionuclide concentration sometimes depends on direction of water mass transport. Abnormally high concentrations of 137Cs in the southeastern Baltic Sea may result from additional radioactive waste discharge.

Stable Water Isotopologue data collected during HCCT-2010

Cloud samples for the isotopic analysis were collected in the framework of the Hill Cap Cloud Thuringia 2010 (HCCT-2010) campaign on Schmücke (50° 39'N/ 10° 46'E, 937 m a.s.l.; Germany) in September and October 2010 with a three-stage Caltech Active Strand Cloudwater Collector (CASCC) during 13 different cloud events with a temporal resolution of 1 to 3 hours. In a first step, we ensured that no additional fractionation occurred during sampling with the CASCC. The d values of the three sizes classes of the CASCC (4 µm to 16 µm, 16 µm to 22 µm and >22 µm) did not differ significantly, revealing that the cloud droplets of different sizes quickly equilibrate their delta value with the one of the surrounding vapor. delta values in the cloud droplets varied from -77 per mil to -15 per mil in d2H and from -12.1 per mil to -3.9 per mil in d18O and were fitted by d2H =7.8*d18O +13*10**-3. delta values decreased with temperature as well as towards the end of the campaign, representing a seasonal trend which is known from d values in precipitation. The deuterium excess of the cloud samples was generally higher than the Local Meteoric Water Line of the closest GNIP (Global Network of Isotopes in Precipitation) station. Rain decreases its deuterium excess during falling through an unsaturated air column, while the cloud droplets conserve the deuterium excess of the initial evaporation and thus have been found to be a good indicator for the airmass source region: higher deuterium excess was measured for polar air masses and lower deuterium excess for Mediterranean air masses. Changes in d values during one cloud event were up to 3.6 per mil (d2H) and 0.23 per mil (d18O), except for frontal passages, which were associated with increases of ~6 per mil per hour (d2H) and ~0.6 per mil per hour (d18O). Using a box model, we showed that the influence of condensation only was able to explain the variation in the isotope signal of two cloud passages. Consequently, we deduced that the water vapor "feeding" the cloud advected the measured changes. A trajectory analysis and moisture source diagnostic revealed that it is very likely that the variations were either related to rain out along the trajectories or to meteorological changes in the moisture source region. This was the first study using stable water isotopologues in cloud water manifesting their potential in the context of atmospheric water vapor circulation.

Chemical and isotope compositions of thermal and surficial waters from the Chukotka Peninsula

Twenty three groups of thermomineral springs in the eastern Chukotka with discharge temperature from 2 to 97°C and mineralization from 1.47 to 37.14 g/l are studied and compared with surface freshwater from their localities. dD and d18O values in surface waters vary from -121.4 to -89.5 per mil and from -16.4 to -11.1 per mil, respectively, while respective values in thermomineral waters range from -134.2 to -92.5 per mil and from -17.6 to -10.5 per mil. dD value in surface waters decreases from the east to the west, i.e. toward interior areas of the peninsula. Hydrothermal springs most depleted in deuterium (dD < -120 per mil) are localized in the geodynamically active Kolyuchinskaya-Mechigmen Depression. According to the proposed formation model of Chukotka thermomineral waters their observed chemical and isotopic characteristics could result from mixing (in different proportions) of surface waters with the deep-sourced isotopically light mineralized component (dD = ca. -138 per mil, d18O = ca. -19 per mil, ? = from 9.5 to 14.7 g/l). The latter originates most likely from subpermafrost waters subjected to slight cryogenic metamorphism.

Compilation of measurements from two interdisciplinary STAR-shaped surveys in the North Sea: The ZISCH - Dataset

The measurements were obtained during two North Sea wide STAR-shaped cruises during summer 1986 and winter 1987, which were performed to investigate the circulation induced transport and biologically induced pollutant transfer within the interdisciplinary research in the project "ZISCH - Zirkulation und Schadstoffumsatz in der Nordsee / Circulation and Contaminant Fluxes in the North Sea (1984-1989)". The inventory presents parameters measured on hydrodynamics, nutrient dynamics, ecosystem dynamics and pollutant dynamics in the pelagic and benthic realm. The research program had the objective of quantifying fluxes of major budgets, especially contaminants in the North Sea. In spring 1986, following the phytoplankton spring bloom, and in late winter 1987, at minimum primary production activity, the North Sea ecosystem was investigated on a station net covering the whole North Sea. The station net was shaped like a star. Sampling started in the centre, followed by the northwest section and moving counter clockwise around the North Sea following the residual currents. By this strategy, a time series was measured in the central North Sea and more synoptic data sets were obtained in the individual sections. Generally advection processes have to be considered when comparing the data from different stations. The entire sampling period lasted for more than six weeks in each cruise. Thus, a time-lag should be considered especially when comparing the data from the eastern and the western part of the central and northern North Sea, where samples were taken at the beginning and at the end of the campaign. The ZISCH investigations represented a qualitatively and quantitatively new approach to North Sea research in several respects. (1) The first simultaneous blanket coverage of all important biological, chemical and physical parameters in the entire North Sea ecosystem; (2) the first simultaneous measurements of major contaminants (metals and organohaline compounds) in the different ecosystem compartments; (3) simultaneous determinations of atmospheric inputs of momentum, energy and matter as important ecosystem boundary conditions; (4) performance of the complex measurement program during two seasons, namely the spring plankton bloom and the subsequent winter period of minimal biological activity; and (5) support of data analysis and interpretation by oceanographic and meteorological numerical models on the same scales.

Separating ITCZ- and ENSO-related rainfall changes in the Galápagos over the last 3 kyr using D/H ratios of multiple lipid biomarkers

We present a 3000-yr rainfall reconstruction from the Galápagos Islands that is based on paired biomarker records from the sediment of El Junco Lake. Located in the eastern equatorial Pacific, the climate of the Galápagos Islands is governed by movements of the Intertropical Convergence Zone (ITCZ) and the El Niño-Southern Oscillation (ENSO). We use a novel method for reconstructing past ENSO- and ITCZ-related rainfall changes through analysis of molecular and isotopic biomarker records representing several types of plants and algae that grow under differing climatic conditions. We propose that ?D values of dinosterol, a sterol produced by dinoflagellates, record changes in mean rainfall in El Junco Lake, while dD values of C34 botryococcene, a hydrocarbon unique to the green alga Botryococcus braunii, record changes in rainfall associated with moderate-to-strong El Niño events. We use these proxies to infer changes in mean rainfall and El Niño-related rainfall over the past 3000 yr. During periods in which the inferred change in El Niño-related rainfall opposed the change in mean rainfall, we infer changes in the amount of ITCZ-related rainfall. Simulations with an idealized isotope hydrology model of El Junco Lake help illustrate the interpretation of these proxy reconstructions. Opposing changes in El Niño- and ITCZ-related rainfall appear to account for several of the largest inferred hydrologic changes in El Junco Lake. We propose that these reconstructions can be used to infer changes in frequency and/or intensity of El Niño events and changes in the position of the ITCZ in the eastern equatorial Pacific over the past 3000 yr. Comparison with El Junco Lake sediment grain size records indicates general agreement of inferred rainfall changes over the late Holocene.

Hydrogen isotope composition of pore waters and interlayer water in sediments of ODP Leg 129 holes

Hydrogen isotope compositions have been measured on pore waters from sediments of Leg 129 sites in the Pigafetta and East Mariana basins (central western Pacific). Total water (pore + sorbed waters) contents and their dD have been analyzed for three samples that contain smectite but no zeolite so that sorbed water can be attributed to interlayer water. The H budget for pore and total waters implies that interlayer water is 20 per mil to 30 per mil depleted in D compared to pore water. Because the interlayer/total water molar ratio (0.25 to 0.5) in smectitic sediments is very high, interlayer water represents an important reservoir of D-depleted water in sediments. dD depth profiles for pore water at Sites 800 and 801 show breaks related to chert and radiolarite layers and are relatively vertical below. Above these chert units, pore waters are similar to modern seawater but below, they are between -10 per mil and -5.5 per mil. These values could represent little modified pre-Miocene seawater values, which were D-depleted because of the absence of polar caps, and were preserved from diffusive exchange with modern seawater by the relatively impermeable overlying chert layers. At Site 802, dD values of the pore waters show a decrease in the Miocene tuffs from 0 per mil values at the top to -8 per mil at 250 mbsf. Below, dD values are relatively uniform at about -8ë. Miocene tuffs are undergoing low water/rock alteration. A positive covariation of dD and Cl content of pore water in the tuffs suggests that the increase of dD values could result from secondary smectite formation. Low diffusive exchange coupled with D enrichment due to alteration of preglacial waters could explain the observed profile.

Geophysical investigations in the European Alps

Joint interpretation of magnetotelluric and geomagnetic depth sounding data in the western European Alps offer new insights into the conductivity structure of the Earth's crust and mantle. This first large scale electromagnetic study in the Alps covers a cross-section from Germany to northern Italy and shows the importance of the alpine mountain chain as an interrupter of continuous conductors. Poor data quality due to the highly crystalline underground is overcome by Remote Reference and Robust Processing techniques. 3d-forward-modelling reveals on the one hand interrupted dipping crustal conductors with maximum conductance of 4960 S and on the other hand a lithosphere thickening up to 208 km beneath the central western Alps. Graphite networks arising from Paleozoic sedimentary deposits are considered to be accountable for the occurrence of high conductivity and the distribution pattern of crustal conductors. The influence of huge sedimentary molasse basins on the electromagnetic data is suggested to be minor compared with the influence of crustal conductors. In conclusion, electromagnetic results can be attributed to the geological, tectonic and palaeogeographical background. Dipping direction (S-SE) and maximum angle (10.1°) of the northern crustal conductor reveal the main thrusting conditions beneath the Helvetic Alps whereas the existence of a crustal conductor in the Briançonnais supports theses about its palaeographic belonging to the Iberian Peninsula.

First results from stable-istope measurements on ice cores from Dronning Maud Land

The European Project for Ice Coring in Antarctica (EPICA) focuses on the drilling of two deep ice cores, the first at Dome C and the second at Kohnen station (75°00' S, 0°04' E) in Dronning Maud Land (DML). This paper deals with stable-isotope records from ice cores drilled in DML. In the first season, the deep EPICA DML core reached a depth of 450 m, recovering ice approximately 7000 years old. Generally, the d18O record indicates a stable Holocene climate and shows low variability. However, during the last 4000 years (based on a preliminary time-scale) the d18O values decrease continuously by about 0.6%, and the deuterium excess values increase by about 0.5%. The correlation between d18O and the deuterium excess d is investigated for a 50m long core section and the near-surface snow. High-pass filtered profiles are positively correlated, whereas the correlation between low-pass filtered profiles is negative. A post-depositional effect due to diffusion processes can be seen in a sub-annually resolved profile from snow-pit samples. Changes in the seasonality of the evolution of the snow cover and the consequences for stable-isotope content are demonstrated with data from ice core B31.