ALBERT

Description: Es wird die These, daß Zinn-führende Granite eine besondere geochemische Spezialisierung aufweisen, an den Beispielen des Sarrabus- (1), San-Vito- (2), Quirra- (3), Arburese- (4) und Monte-Linas-Granites (5) in S-Sardinien geprüft. Sie repräsentieren herzynische Plutongranite mit relativ hohem Intrusionsstockwerk und scharf ausgebildeten Intrusivkontakten zu schwach metamorphen altpaläozoischen Rahmengesteinen der Grünschieferfazies. Zinnlagerstätten treten nur im Umfeld der Massive (4) und (5), Mo-W-Vererzungen im Bereich der Massive (3) und (5) auf. Petrologisch bestehen die Massive hauptsächlich aus Leukogranit, untergeordnet und lokal treten auch Monzogranit, Granodiorit und Tonalit auf. Typisch für die Massive (3), (4) und (5) sind Zweiglimmergranite und Greisenbildungen mit unbedeutenden Anreicherungen der Elemente Sr, Mo, W, Zn und Cu. Petrochemisch sind die Granitoide als raum-zeitliche Differentationsreihen kalkalkalischer Magmen aufzufassen, an deren Ende Zweiglimmergranite als höchst spezialisierte Differentiate stehen. Ihre Sr^87/Sr^96 - Zusammensetzung deutet auf eine krustale Herkunft der Ausgangsschmelzen hin. Die Konzentration signifikanter Elemente der Frühkristallisation (Ti, Zr, Mg, Fe, P, Ca, Ba und Sr) nimmt zu den sauren Differentiaten hin ab, die der Spätkristallisation (F, B, Sn, Rb, Li) diametral zu. Danach erreichte der Quirra-Granit ein höchstes Differentationsniveau. Die Entwicklung der Massive im Einzelnen wird von folgenden Mechanismen kontrolliert: 1. Durch in-situ-Differentation bei der Entwicklung aller Massive, 2. durch emanative Differentation bei der Entwicklung des Quirra- (3), Monte-Linas- (5) und, mit Einschränkung, auch des Arburese-Granites (4), 3. durch nachträgliche metasomatische Stoffverschiebungen hauptsächlich bei der Entwicklung des Quirra- (3), Arburese- (4) und Monte-Linas-Granites (5). Bei Letzteren treten auch anomale Zinngehalte in Flußsedimenten, im granitischen Festgestein und seiner Biotite sowie in den Kontaktgesteinen auf. Die Häufigkeit anomaler Werte von 17 Indikatorgrößen, ihre Mittelwerte und Streuungen sowie die Intensität der geochemischen Spezialisierung in Bezug auf Sn, Rb, Li und F grenzen die Massive (3), (4) und (5) einhellig als für weitere Prospektionsarbeiten interessante Gebiete ab. Die absolute Intensität der Spezialisierung erreicht aber nicht das Ausmaß bekannter Zinnprovinzen. So sind für diese Granite z. B. relativ niedrige Bor- und z. T. auch Fluorwerte charakteristisch. Allgemein sind die Indikatorgrößen deutlich vom Intrusionsniveau eines Granites abhängig. Der Vergleich mit Literaturdaten führt zu einer Klassifizierung in geochemisch spezialisierte Granite 1. und 2. Ordnung im Rb-Ba-Sr- und K/Rb-Rb/Sr-Diagramm. Zinn-führende Granite heben sich also innerhalb gewisser geochemischer Variationsbreiten deutlich von sterilen Graniten ab.

Description: Summary Summary The thesis that tin bearing granites exhibit a significant geochemical character is tested by investigations of the Sarrabus (1), San Vito (2), Quirra (3), Arburese (4), and Monte Linas (5) Granite, all situated in south Sardinia. These massifs represent Hercynian granitic intrusives of high intrusion level and knife-like contacts to the adjacent rocks of Lower Palaeozoic age of greenshist facies. Endogenous tin deposits exist only spatially to the massifs (4) and (5), Mo-W-mineralizations in connection to the massifs (3) and (5). Petrologically all massifs consist principally of leucogranite. Monzogranite, granodiorite, and tonalite are rare and occure only locally. A peculiarity within the massifs (3), (4), and (5) are muscovite biotite granites and greisen with unimportant concentrations of the elements Sn, Mo, W, Zn, and Cu. Petrochemically the granitoids represent a spatial and temporal suite of a calc-alkaline magma with the muscovite biotite granites as highest specialized members. The crustal origin of the primary magmas is proven by Sr^87/Sr^96 datas. Generally the concentration of significant elements characterizing the early cristallization of a magma (Ti, Zr, Mg, Fe, P, Ca, Ba, and Sr) increase in direction of the later differentiates. The granitophile elements (F, B, Sn, Rb, Li) against that are enriched. The magmatic evolution of the massifs is governed by the following processes: 1. By in situ differentiation in the formation of all massifs, 2. by emanative differentiation in the formation of the massifs (3) and (5), with reservation also massif (4), 3. by later metasomatic chemical changes that occurred during greisenization especially in the formation of the massifs (3), (4), and (5). Anomalous tin contents are observed in alluvial sediments, leucogranites, and their biotites and country rocks distinctly of massif (5). The abundance of anomalous values of 17 proximity indicators, their mean and dispersion values and the degree of total geochemical specialization of Sn, Rb, Li, and F in the leucogranites determine uniformely the massifs (3), (4), and (5) as most interesting prospects for further detail exploration activities. The intensity of metallogenetic specialization is not as high as in other provinces. So the intrusives have extreme low concentrations of B and relative low contents of F. Generally the proximity indicators are dependent on the intrusion level of the granites. Together with reference datas from other areas one can establish geochemically specialized intrusives of first and second order. Tin bearing granites are distinguished within certain levels of clustering distinctly from barren granites.

Description: thesis

Description: DFG, SUB Göttingen

Description: Zur Ermittlung von geochemischen "proximity indicators" für den erzhöffigen (oberen) Abschnitt des Alpinen Muschelkalks wurden 11 Probennahmeprofile aus den Nördlichen Kalkalpen sowie als Vergleich 2 Probennahmeprofile aus den Südlichen Kalkalpen bearbeitet. Die Probennahme erfolgte in annähernd homogenen Gesteinsserien systematisch, in inhomogenen oberen und mittleren Partien des Alpinen Muschelkalks auch (fazies-) differenziert. Aus insgesamt ca. 1750 Schichtmetern wurden 652 Proben zur geochemischen Analyse aufbereitet. Die Bestimmung des Mg- und der Spurenelementgehalte von Sr, Zn, Pb, Fe, Mn, Cu und Cr erfolgten mit einem Atom-Absorptionsspektrophotometer (AAS). Die Fluoranalyse geschah mit ionenselektiven Elektroden (potentiometrische Fluoridbestimmung). Der Anteil der unlöslichen Rückstände wurde gravimetrisch ermittelt und fallweise mit Hilfe eines Roentgendiffraktometers näher untersucht. Die Auswertung der ca. 10 600 Analysendaten erfolgte über EDV. Mit Hilfe von Rechenprogrammen wurden Ca-Gehalte, Korrelationskoeffizienten, geometrische Mittelwerte und Streuungen ermittelt. Ober die konventionelle Statistik der geochemischen Analysendaten mit Ermittlung r e g i o n a l e r Background- und Threshold-Daten hinaus wurden zusätzlich l o k a l e Background- und Threshold-Werte festgestel1t, um die l o k a l e n Anomalien der als regional repräsentativ angenommenen Profile herauszuarbeiten und vergleichbar zu machen. Die Obergrenze des Alpinen Muschelkalks mußte nach konventionellen lithologischen Gesichtspunkten angenommen werden. Eine genauere stratigraphische Korrelierung der Probennahmeprofile war jedoch durch Tuff-Lagen (Pietra verde) möglich, soweit diese aufgeschlossen waren. Korrelationsrechnungen gaben Hinweise auf die Bindung der einzelnen Elemente sowie ihre primäre und sekundäre Anreicherung im Sediment. Die Hauptelemente Ca und Mg stammen vorherrschend aus dem Calcit- und Dolomitanteil. Säureunlösliche Rück stände setzen sich neben Quarz hauptsächlich aus Tonmineralen der Illit-Gruppe (mixed layers) zusammen. Sr-Gehalte sind eindeutig an den Kalkanteil, Fe und Cr überwiegend an Tonminerale gebunden. Zn, Mn und Cu liegen gleichwertig in Bindung an Tonminerale wie an das Karbonatgitter vor. Pb scheint überwiegend an den Kar bonatanteil gebunden zu sein. Extrem hohe Spurenelementkonzentrationen ("Ausreißer") von Pb, Zn, Fe, Cu und Mn werden auf einzelne, zufällig erfaßte Sulfid-, Oxyd- und Karbonatminerale dieser Elemente zurückgeführt. Die Analyse der Pb-Daten erwies sich nicht in allen Belangen als befriedigend. Die Gehalte von Pb in Karbonatgesteinen bewegen sich für den Entwicklungsstand des hier benutzten Analysegeräts zu nahe an der Nachweisgrenze. Die Auswertung erbrachte: - Stratiforme Anomalien, die über mehrere Probennahmeprofile verfolgbar und an bestimmte stratigraphische Niveaus gebunden sind. - Diskordante Anomalien, die in der Umgebung von bekannten Erzkörpern durch primäre oder sekundäre Migration hervorgerufen wurden. Die oberen Partien des Alpinen Muschelkalks sind meist hornsteinführend, insbesondere in der räumlichen und zeitlichen Nachbarschaft der Vulkanite. Dabei ist besonders auffällig, daß der Si02-Anteil im Liegenden und Hangenden von Tuff-Lagen (Pietra verde, 4 Zyklen) ungewöhnlich ansteigt. Dort entnommene Karbonatgesteinsproben zeigen stratiform anomal erhöhte Spurenelementkonzentrationen von Pb und Zn, fallweise begleitet von anomal er höhten F-, Fe-, Mn- und Cr-Werten. Stratiforme Anomalien von Zn-Pb-F, lokal auch von Fe-Cu-Mn-Cr, konnten regional über die Flexenpaß-Profile, Profil Zugspitze N und Martinswand verfolgt werden. In gleichem stratigraphischem Niveau wurden an anderer Stelle (Profile Davos-Silberberg, Krabachjoch u. St.Veith) diskordante Pb-Zn, F-, Fe-Mn- oder Cu-Anomalien be obachtet. Durch die wesentlich höheren Spurenelementkonzentrationen in diskordanten Anomalien wird die hier zu erwartende stratiforme Anomalie verdeckt. Im unteren und mittleren Teil des Alpinen Muschelkalks lokal auftretende, anomal erhöhte Spurenelementkonzentrationen waren dagegen regional nicht stratigraphisch korrelierbar. Geochemische Untersuchungen an Karbonatgesteinen aus den Südlichen Kalkalpen (Profile Valle Ambata/Auronzo und Topla/Mezica) lieferten keine Hinweise auf die Möglichkeit der Korrelation mit den Stratiformen Anomalien der Nördlichen Kalkalpen. Gegenüber den Karbonatgesteinen, Mergeln und Tonsteinen zeigt die Pietra verde signifkant erhöhte Gehalte von Zn und F. Diese deuten einen genetischen Zusammenhang zwischen einer zeitgleichen Zufuhr mit den Pyroklastika und einer Konzentration von Zn und F in den zwischengeschalteten Karbonatgesteinen an. Die Elemente Zn und F zeigten untereinander eine deutliche Korrelation. Bei der Suche nach schichtgebundenen Pb/Zn-Vorkommen in Karbonatgesteinen kann daher die Analyse der F-Gehalte als geochemische Prospektionshilfe (proximity indicator) herangezogen werden.

Description: ABSTRACT In order to determinate geochemical proximity indicators of the ore-bearing (upper) parts of the 'Alpiner Muschelkalk' (Anisian s. str.) rock samples have been taken from 11 standard profiles in the 'Nördliche Kalk alpen', and for comparison 2 standard profiles in the 'Südliche Kalkalpen'. Sampling was done systematically in aproximative homogeneous carbonate sequences and (facies-) differentiated in inhomogeneous sequences in the middle and upper parts of the 'Alpiner Muschelkalk'. 652 samples collected over 1.750 meters in total have been upgraded for geochemical analysis. Contents of Mg and trace elements like Sr, Zn, Pb, Fe, Mn, Cu and Cr have been determined by atomic absorption spectrophotometry. The F-analysis was done by a fluoride ion activity electrode (potentiometric fluorid analysis). Insoluble residues have been determined gravimetrically and occasionally examined by x-ray-diffraction. The analysis of about 10.600 data obtained has been processed by computer programme. Ca-data, correlation coefficients, geometric means and scattering have been computed by mathematical systems. Besides conventional statistics of geochemical analysis data like determination of regional backgrounds and thresholds, local backgrounds and thresholds have been computed, too, for showing and making comparable local anomalies of regional representative standard profiles. The border to the hanging wall had to be determined by conventional lithological conception. A more exact stratigraphical correlation of standard profiles was made possible by tuffs as far as they outcropped. Correlation coefficients showed the mineralogical bounding of elements as well as the primary and secondary concentrations in the sedimentary sequences. The major elements Ca and Mg originate predominantly from calcite and dolomite. Insoluble residues consist essentially of clay minerals of Illite-group (mixed layers) and quartz. Sr is clearly bound to calcite, Fe and Cr are linked to clay minerals as well as to calcite. Extremely high trace element concentrations of Pb, Zn, Fe, Mn and Cu are considered to originate from accidently caught sulfides, oxides or carbonates of these elements. Analysis of Pb data was not satisfactory in each matter, as the contents of Pb in carbonate rocks are to close to the noise of used AAS. The evaluation showed: — Stratiform anomalies, which can be correlated in several standard profiles and which are bound to distinct stratigraphic levels. -Discordantanomalies, which are caused by primary or secondary migration from ore bodies nearby. In the upper parts of the 'Alpiner Muschelkalk occur cherty limestones, especially in regional and stra tigraphical neighbourhood of volcanics. It is conspicuous, that carbonates belonging to the foot wall and hanging wall of tuffs (Pietra verde) are unusual rich of silica. Carbonate samples of this matter show stra tiform anomalous high trace element concentrations of Pb and Zn, occasionally accompanied by anomalous high concentrations of F, Fe, Mn and Cr. Stratiform anomalies of Zn-Pb-F, in some profiles also of Fe-Mn-Cu-Cr, can be correlated regionally in the Flexenpass-profiles and the profiles Zugspitze and Martinswand. At the same stratigraphical level there have been observed anomalies of Pb-, Zn-, F-, Fe-, Mn- or Cu at other places (profiles Davos-Silberberg, Kra bachjoch and St. Veith). Here the expected stratiform anomalies are masked by the higher trace element con centrations of discordant anomalies. The trace element concentrations of the lower and middle part of the 'Alpiner Muschelkalk' however, are not stratigraphically correlated. Geochemical data of the two profiles from the 'Südliche Kalkalpen' (profiles Valle Ambata/Auronzo and Topla/Me2ica) do not indicate a correlation with stratiform anomalies of the 'Nördliche Kalkalpen'. In opposition to the carbonates, marls and clays, the 'Pietra verde' shows significant higher contents of Zn and F. This indicates a genetic connection between the pyroclastics and the concentration of Zn and F in the intercalated carbonates. The elements Zn and F exhibit an evident correlation. The analysis of F may find application as a proximity indicator for exploration of stratabound lead-zinc occurrences in carbonate rocks.

Description: thesis

Description: DFG, SUB Göttingen

Description: Methane (CH4) production in the ocean surface mixed layer is a widespread but still largely unexplained phenomenon. In this context marine algae have recently been described as a possible source of CH4 in surface waters. In the present study we investigated the effects of temperature and light intensity (including daylength) on CH4 formation from three widespread marine algal species Emiliania huxleyi, Phaeocystis globosa, and Chrysochromulina sp. Rates of E. huxleyi increased by 210% when temperature increased in a range from 10°C to 21.5°C, while a further increase in temperature (up to 23.8°C) showed reduction of CH4 production rates. Our results clearly showed that CH4 formation of E. huxleyi is controlled by light: When light intensity increased from 30 to 2,670 μmol m−2 s−1, CH4 emission rates increased continuously by almost 1 order of magnitude and was more than 1 order of magnitude higher when the daylength (light period) was extended from 6/18 hr light-dark cycle to continuous light. Furthermore, light intensity is also an important factor controlling CH4 emissions of Chrysochromulina sp. and P. globosa and could therefore be a species-independent regulator of phytoplankton CH4 production. Based on our results, we might conclude that extensive blooms of E. huxleyi could act as a main regional source of CH4 in surface water, since blooming of E. huxleyi is related to the seasonal increase in both light and temperature, which also stimulate CH4 production. Under typical global change scenarios, E. huxleyi will increase its CH4 production in the future.

Description: The Deep Blue (DB) aerosol retrieval algorithm has recently been applied to Advanced Very High Resolution Radiometer (AVHRR) data to produce a first version (V001) of a global aerosol optical thickness (AOT) data set. In this paper, we critically evaluate these AVHRR AOT data over China by comparison with ground-based reference data from China Aerosol Remote Sensing Network for the period 2006–2011. The evaluation considers the impact of the surface (type and reflectance) and the aerosol properties (aerosol loading, aerosol absorption) on the quality of the retrieved AOT. We also compare the AVHRR-retrieved AOT with that from Moderate Resolution Imaging Spectroradiometer over major aerosol source regions in China. We further consider seasonal variations and find, in general, a good agreement between AVHRR AOT and the reference data sets. The AVHRR retrieval algorithm performs well over dark vegetated surfaces, but over bright surfaces (e.g., desert regions) the results are less good. The AVHRR algorithm underestimates the AOT, with 32.1% of the values lower than the estimated error envelope of ±0.05 ± 0.25τ. In particular over the desert, the AVHRR-retrieved AOT is frequently underestimated and for AOT ≤ 0.6 the values are on average 0.05 too low due to the pixel filtering, and dust storms are missed. The comparison of the AVHRR AOT with MODIS collection 6 and CARSNET data indicates that improvements are needed for, for example, AVHRR calibration and cloud/aerosol flagging. The analysis presented in this paper contributes to a better understanding of the AVHRR AOT product over China.

Description: Deforestation influences surface properties such as surface roughness, resulting in changes in the surface energy balance and surface temperature. Recent studies suggest that the biogeophysical effects are dominated by changing roughness, and it remains unclear whether this can be reconciled with earlier modeling studies that highlighted the importance of a reduction of evapotranspiration in the low latitudes and a reduction of net shortwave radiation at the surface in the high latitudes. To clarify this situation, we analyze the local effects of deforestation on surface energy balance and temperature in the MPI-ESM climate model by performing three separate experiments: switching from forest to grass all surface properties, only surface albedo, and only surface roughness. We find that the locally induced changes in surface temperature are dominated by changes in surface roughness for the annual mean, the response of the diurnal amplitude, and the seasonal response to deforestation. For these three quantities, the results of the MPI-ESM lie within the range of observation-based data sets. Deforestation-induced decreases in surface roughness contribute substantially to winter cooling in the boreal regions and to decreases in evapotranspiration in the tropics. By comparing the energy balance decompositions from the three experiments, the view that roughness changes dominate the biogeophysical consequences of deforestation can be reconciled with the earlier studies highlighting the relevance of evapotranspiration.

Description: We show that there is a strong sensitivity of cloud microphysics to model time step in idealized convection-permitting simulations using the COnsortium for Small-scale MOdeling model. Specifically, we found a 53% reduction in precipitation when the time step is increased from 1 to 15 s, changes to the location of precipitation and hail reaching the surface, and changes to the vertical distribution of hydrometeors. The effect of cloud condensation nuclei perturbations on precipitation also changes both magnitude and sign with the changing model time step. The sensitivity arises because of the numerical implementation of processes in the model, specifically the so-called “splitting” of the dynamics (e.g., advection and diffusion) and the parameterized physics (e.g., microphysics scheme). Calculating one step at a time (sequential-update splitting) gives a significant time step dependence because large supersaturation with respect to liquid is generated in updraft regions, which strongly affect parameterized microphysical process rates—in particular, ice nucleation. In comparison, calculating both dynamics and microphysics using the same inputs of temperature and water vapor (hybrid parallel splitting) or adding an additional saturation adjustment within the dynamics reduces the time step sensitivity of surface precipitation by limiting the supersaturation seen by the microphysics, although sensitivity to time step remains for some processes.

Description: The isotopic composition of Si in biogenic silica (BSi), such as opal buried in the oceans' sediments, has changed over time. Paleorecords suggest that the isotopic composition, described in terms of δ30Si, was generally much lower during glacial times than today. There is consensus that this variability is attributable to differing environmental conditions at the respective time of BSi production and sedimentation. The detailed links between environmental conditions and the isotopic composition of BSi in the sediments remain, however, poorly constrained. In this study, we explore the effects of a suite of offset boundary conditions during the Last Glacial Maximum (LGM) on the isotopic composition of BSi archived in sediments in an Earth System Model of intermediate complexity (EMIC). Our model results suggest that a change in the isotopic composition of Si supply to the glacial ocean is sufficient to explain the observed overall low(er) glacial δ30Si in BSi. All other processes explored trigger model responses of either wrong sign or magnitude or are inconsistent with a recent estimate of bottom water oxygenation in the Atlantic Sector of the Southern Ocean. Caveats, mainly associated with generic uncertainties in today's pelagic biogeochemical modules, remain.

Description: The aeronautical community is currently researching technology that might lead to commercial hypersonic aircraft that would cruise at Mach 5–8 in the middle or upper stratosphere and would transfer passengers from London to New York or from Los Angeles to Tokyo in just a couple of hours. Depending on the engine technology to be adopted, these aircraft will potentially release substantial amounts of water vapor and nitrogen oxides around 30–40 km altitude. We show here that the operation of a large fleet of such aircraft could potentially deplete considerable amounts of ozone in the stratosphere, which would lead to a substantial increase in biologically damaging ultraviolet radiation reaching the Earth's surface. The calculations are based on a specific emission scenario, which carries large uncertainties but can easily be scaled to account for the type of aircraft engine to be eventually adopted, improved technology to be expected, and the size and operation conditions of the future aircraft fleet.

Description: A new microphysical cirrus model to simulate ice crystal nucleation, depositional growth, and gravitational settling is described. The model tracks individual simulation ice particles in a vertical column of air and allows moisture and heat profiles to be affected by turbulent diffusion. Ice crystal size- and supersaturation-dependent deposition coefficients are employed in a one-dimensional model framework. This enables the detailed simulation of microphysical feedbacks influencing the outcome of ice nucleation processes in cirrus. The use of spheroidal water vapor fluxes enables the prediction of primary ice crystal shapes once microscopic models describing the vapor uptake on the surfaces of cirrus ice crystals are better constrained. Two applications addressing contrail evolution and cirrus formation demonstrate the potential of the model for advanced studies of aerosol-cirrus interactions. It is shown that supersaturation in, and microphysical and optical properties of, cirrus are affected by variable deposition coefficients. Vertical variability in ice supersaturation, ice crystal sedimentation, and high turbulent diffusivity all tend to decrease homogeneously nucleated ice number mixing ratios over time, but low ice growth efficiencies counteract this tendency. Vertical mixing induces a tendency to delay the onset of homogeneous freezing. In situations of sustained large-scale cooling, natural cirrus clouds may often form in air surrounding persistent contrails.

Description: Within a rapidly changing Arctic climate system, snow on sea ice is an important climate parameter. A common method to derive snow depth on an Arctic-wide scale is based on passive microwave satellite observations. However, the uncertainties of this method are not well constrained. In this study, we estimate the influence of geophysical parameters, including ice, snow, and atmospheric properties on passive microwave snow depth retrievals using a Monte Carlo uncertainty estimation. The results are based on model simulations from the Microwave Emission Model for Layered Snowpacks, the SNOWPACK model, and from the Passive and Active Microwave TRAnsfer model. All simulations are based on in situ observations obtained during the N-ICE2015 campaign. The average uncertainty in potential snow depth retrievals is between 11% and 19%, depending on the microwave frequencies used and increases with increasing snow depth. For lower-frequency retrievals (including 6.9 GHz), unknown snow properties are the strongest source of uncertainty while for higher-frequency retrievals (including 36.5 GHz), the contribution of ice, snow properties, and clouds is equally strong.