Neure Veröffentlichungen     

Hartmut Heinrich  Hartmut Klüger 《Ocean Dynamics》1986,39(4):179-181

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A komatiite component in Apollo 16 highland breccias: implications for the nickel-cobalt systematics and bulk composition of the moon     

A.E. Ringwood  Stefan Seifert  Heinrich Wnke 《Earth and Planetary Science Letters》1987,81(2-3)

The lunar crust at the Apollo 16 landing site contains substantial amounts of a “primitive component” in which the ferromagnesian group of elements is concentrated. The composition of this component can be retrieved via an analysis of mixing relationships displayed by lunar breccias. It is found to be a komatiite which is compositionally similar to terrestrial komatiites both in major and minor elements. The komatiite component of the lunar crust is believed to have formed by extensive degrees of melting of the lunar interior at depths greater than were involved in the formation of the lunar magma ocean which was parental to the crust. After formation of the anorthositic crust, it was invaded by extensive flows and intrusions of komatiite magma from these deeper source regions. The komatiites became intimately mixed with the anorthosite by intensive meteoroid impacts about 4.5 b.y. ago, thereby accounting for the observed mixing relationships displayed by the crust. The compositional similarity between lunar and terrestrial komatiites strongly implies a corresponding similarity between the compositions of their source regions in the lunar interior and the Earth's upper mantle. The composition of the lunar interior can be modelled more specifically by combining the komatiite composition with its liquidus olivine composition (as determined experimentally) in proportions chosen so as to produce a cosmochemically acceptable range of Mg/Si ratios for the bulk Moon. Except for higher FeO and lower Na₂O, the range of compositions thereby obtained for the bulk moon is very similar to the composition of the Earth's upper mantle.The effects of meteoritic contamination on the abundances of cobalt and nickel in lunar highland breccias were subtracted on the assumption that the contaminating projectiles were chondritic. The cobalt and nickel residuals thereby obtained were found to correlate strongly with the (Mg + Fe) content of the breccias, demonstrating that the Co and Ni are associated with the ferromagnesian component of the breccias and are genuinely indigenous to the Moon. The lunar highland Co and Ni residuals also display striking Ni/Co versus Ni correlations which follow a similar trend to those displayed by terrestrial basalts, picrites and komatiites. The lunar trends provide further decisive evidence of the indigenous nature of the Co and Ni residuals and suggest the operation of extensive fractionation controlled by olivine-liquid equilibria in producing the primitive component of the lunar breccias. Indigenous nickel abundances at the Apollo 14, 15 and 17 sites are much lower than at the Apollo 16 site, although rocks from all sites follow the same Ni/Co versus Ni trends. It is suggested that the primitive component at the Apollo 14, 15 and 17 sites was generally of basaltic composition, in contrast to the komatiitic nature of the Apollo 16 primitive component.  相似文献   

Neuere Veröffentlichungen     

Hartmut Heinrich  Jürgen Schulz-Ohlberg  Dietrich Voppel 《Ocean Dynamics》1987,40(5):235-239

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Post-drilling destabilization of temperature profile in borehole Yaxcopoil-1, Mexico     

Jan Šafanda  Philipp Heidinger  Helmut Wilhelm  Vladimír Čermák 《Hydrogeology Journal》2007,15(2):423-428

As part of the International Continental Scientific Drilling Program (ICDP), the 1.5-km-deep borehole Yaxcopoil-1, located in the Chixculub meteor impact structure in Mexico, has undergone further study after drilling operations ceased. Temperature logs were repeated ten times at intervals 0.3–0.8, 15, 24 and 34 months after borehole shut-in. The logs bear a distinct signature of transient heat transfer by groundwater flow manifested by a gradual distortion of the linear temperature profile when a cold wave of 0.8–1.6°C amplitude was detected propagating downward from 145 to 312 m at a rate of 4–6 m/month. To understand the nature of this moving anomaly, a 20-day monitoring of the cold wave was carried out at a depth of 307 m that showed further cooling of 0.6°C during the first 16 days of the passage followed by temperature stabilisation. As an explanation of this unusual phenomenon, a theory is proposed, whereby the drilling mud has accumulated within the overlying and cooler highly porous and permeable karstic rocks during the drilling and migrates downward. The observed migration rate suggests a permeability higher than 10^?11 m². This indicates a high vulnerability to contamination of the only freshwater aquifer in the Yucatan region.  相似文献   

Time-dependent thermal state of the lithosphere in the foreland of the Eastern Carpathians bend. Insights from new geothermal measurements and modelling results     

C. Demetrescu  H. Wilhelm  M. Tumanian  S.B. Nielsen  A. Damian  V. Dobric&#;  M. Ene 《Geophysical Journal International》2007,170(2):896-912

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Gas hydrate stability and the assessment of heat flow through continental margins   总被引：7，自引：0，他引：7  

Ingo Grevemeyer  Heinrich Villinger 《Geophysical Journal International》2001,145(3):647-660

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Grain boundary diffusion of Si, Mg, and O in enstatite reaction rims: a SIMS study using isotopically doped reactants     

R. Milke  M. Wiedenbeck  W. Heinrich 《Contributions to Mineralogy and Petrology》2001,142(1):15-26

Diffusion-controlled growth rates of polycrystalline enstatite reaction rims between forsterite and quartz were determined at 1,000 °C and 1 GPa in presence of traces of water. Iron-free, pure synthetic forsterite with normal oxygen and silicon isotopic compositions and quartz extremely enriched in ¹⁸O and ²⁹Si were used as reactants. The relative mobility of ¹⁸O and ²⁹Si in reactants and rims were determined by SIMS step scanning. The morphology of the rim shows that enstatite grows by a direct replacement of forsterite. Rim growth is modelled within a mass-conserving reference frame that implies advancement of reaction fronts from the initial forsterite-quartz interface in both directions. The isotopic compositions at the two reaction interfaces are controlled by the partial reactions Mg₂SiO₄=0.5 Mg₂Si₂O₆+MgO at the forsterite-enstatite, and MgO+SiO₂=0.5 Mg₂Si₂O₆ at the enstatite-quartz interface, implying that grain boundary diffusion of MgO is rate-controlling. Isotopic profiles show no silicon exchange across the propagating reaction interfaces. This propagation, controlled by MgO diffusion, is faster than the homogenisation of Si by self-diffusion behind the advancing fronts. From this, and using % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiramaaDa % aaleaacaWGtbGaamyAaiaacYcacaWGfbGaamOBaaqaaiaadAfacaWG % VbGaamiBaaaaaaa!3DD2! D_Si,En^VolD_{Si,En}^{Vol} at dry conditions from the literature, results a % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmirayaafa % Waa0baaSqaaiaadofacaWGPbGaaiilaiaadweacaWGUbaabaaaaOGa % eqiTdqgaaa!3CCD! D￠_Si,En dD'_{Si,En}^{} \delta value of 3᎒^-24 m³ s^-1 at 1,000 °C. The isotopic profiles for oxygen are more complex. They are interpreted as an interplay between the propagation of the interfaces, the homogenisation of the isotope concentrations by grain boundary self-diffusion of O within the rim, and the isotope exchange across the enstatite-quartz interface, which was open to ¹⁸O influx from quartz. Because of overlapping diffusion processes, boundary conditions are unstable and D´_Ox,En' cannot be quantified. Using measured rim growth rates, the grain boundary diffusivity D´_MgO' of MgO in iron-free enstatite is 8᎒^-22 m³ s^-1 at 1,000 °C and 1 GPa. Experiments with San Carlos olivine (fo₉₂) as reactant reveal lower rates by a factor of about 4. Our results show that isotope tracers in rim growth experiments allow identification of the actual interface reactions, recognition of the rate-controlling component and further calculation of D´' values for specific components.  相似文献   

Leaching and differential recrystallization of metamict zircon under experimental hydrothermal conditions   总被引：14，自引：0，他引：14  

Thorsten Geisler  Marcus Ulonska  Helmut Schleicher  Robert T. Pidgeon  Wilhelm van Bronswijk 《Contributions to Mineralogy and Petrology》2001,141(1):53-65

We report results of hydrothermal experiments on four alluvial zircons from Sri Lanka, which cover a wide range of radiation damage, at 450 °C and 1.3 kbar for 744 h with 2 M CaCl₂ solution as reactive fluid. After the hydrothermal treatment, the most metamict samples show micrometer-thick reaction rims, which surround apparently unreacted zircon, as revealed by cathodoluminescence (CL) and Nomarski differential interference contrast (NDIC) images. These rims have sharp, curved, and transgressive boundaries with unreacted zircon and are, in some cases, spread out along cracks. The thickness of reaction rims increases with increasing cumulated !-dosage of the starting materials. The reaction rims are strongly enriched in Ca (up to 7000 ppm) and a water species and depleted in radiogenic Pb, Zr, and Si, as revealed by electron microprobe analyses. A significant Th loss from the reaction rims was detected in the case of the most metamict sample, whereas U remained in the structure. FT-infrared spectrometry and X-ray diffraction measurements revealed that the bulk run products were recrystallized. Using micro-Raman spectrometry, we were able to demonstrate that differential recrystallization took place. The reaction rims are strongly recrystallized, whereas the unreacted grain interiors underwent only minor recrystallization. Recrystallization of the rims is accompanied by an enhancement of the integral CL intensity. It is suggested that recrystallization in the reaction rims was catalyzed by water infiltration and ion exchange and prevented significant congruent zircon dissolution under the given experimental conditions. Previous zircon studies have shown that (1) a transgressive morphology, (2) a reduced Th-U ratio, and (3) an enhanced CL emission are also characteristics of rims in zircons from high-grade metamorphic rocks. Based on these similarities between natural and experimentally produced rims, it is suggested that leaching-catalyzed recrystallization is an important alteration process in zircon under wet geological conditions and can account for many complex core-rim structures found in natural zircons. Furthermore, the strong enrichment of Ca in the reaction rims supports previous assumptions that high Ca concentrations in natural zircons are of secondary origin. It is suggested that lower U-Pb concordia intercept ages obtained from single-phase zircons with high Ca contents date a leaching event.  相似文献   

Historical record of polycyclic aromatic hydrocarbons (PAH) and heavy metals in floodplain sediments from the Rhine River (Hessisches Ried, Germany)     

Tilman Gocht  Klaus-Martin Moldenhauer  Wilhelm Püttmann 《Applied Geochemistry》2001,16(15):301

The depth-related content of polycyclic aromatic hydrocarbons (PAH) and heavy metals was determined for two soil profiles (i.e. one Fluvisol and one Gleyic Cambisol) which developed in sediments from floodplains located at an old meander of the Rhine river. The meander had been cut off from the main river in 1829. The separation of the meander from the main river caused a change in sediment deposition (i.e. from sand to silt) which is clearly visible in the soil-profiles. Since that time, approximately 100 cm of sediments have accumulated due to temporary flooding of the area. Each soil profile was separated into 18 samples. The samples were analysed for their content of PAH after solvent extraction. Additionally, several trace elements (Co, Ni, Cd, Pb, Zn, Cr and Cu) were determined in the same sample set, and depth-related concentration profiles for both PAH and trace elements were developed. The distribution patterns of PAH with more than 3 condensed rings did not provide any evidence for PAH biodegradation or vertical transport after deposition of the sediments. Thus, in the case of PAH, the historical record can be derived not only from subhydric sediments but also from floodplain sediments. It was not possible to distinguish between atmospheric and fluvial input of PAH into the sediments from the observed distribution patterns due to the same origin of PAH from pyrolytic processes. A source determination of the PAH was not possible except for perylene, for which biogenic formation can be assumed. A comparison of the results shows that the depth-related PAH and trace element concentrations display similar trends over most of the total profiles. In the uppermost section of the profiles, the concentration of most trace elements declines whereas the PAH concentration remains high. This indicates the presence of different sources for PAH and trace elements in the last decades.  相似文献   

A novel ozone sensor for direct eddy flux measurements     

Hans Güsten  Günther Heinrich  Ralf W. H. Schmidt  Ulrich Schurath 《Journal of Atmospheric Chemistry》1992,14(1-4):73-84

A small, lightweight (1.5 kg) and fast-response ozone sensor for direct eddy flux measurements has been built. The basis for detection is the chemiluminescence of an organic dye adsorbed on dry silica gel in the reaction with ozone. The chemiluminescence is monitored with a cheap and small blue-sensitive photomultiplier. At a flow rate of 100 l min^-1 the ozone sensor has a 90% response time of significantly better than 0.1 s with a detection limit lower than 50 ppt at S/N=3. There are no interferences from other atmospheric trace gases like NO_x, H₂O₂ and PAN. Water vapour and SO₂ enhance the chemiluminescence efficiency of the ozone sensor. Since their response times are 22 seconds and 30 minutes, respectively, no correlation between rapid ozone fluctuations and those of these two trace gases is noticed by the ozone sensor when operating at a frequency of 10 Hz.The ozone sensor was tested for several weeks in continuous measurements of ozone fluxes and deposition velocities over different croplands using the eddy correlation technique. Good agreement was found between ozone dry deposition velocities derived from profile measurements and by eddy correlation.  相似文献