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Plagioclase dissolution related to biodegradation of oil in Brent Group sandstones (Middle Jurassic) of Gullfaks Field, northern North Sea 总被引：1，自引：0，他引：1
Brent Group sandstones from the north side of the Gullfaks Oilfield contain mostly 5–8% albitic plagioclase, whereas plagioclase is almost absent in the same strata in the southern part of the field. Absence of plagioclase throughout the entire vertical extent of the Brent Group in the southern wells seems to rule out provenance as the principal explanation for differing plagioclase content, which is therefore interpreted as the result of diagenesis. Hypotheses for the nature of the inferred leaching event include epigenetic meteoric diagenesis and mesogenetic release of acid components from clay minerals or kerogen, but these explanations are unable to account for the observed spatial distribution of the plagioclase-bearing and plagioclase-free sandstone intervals. However, overall correspondence between the area lacking plagioclase and oil compositions having both anomalously high CO2 and organic geochemical indications of advanced biodegradation suggest a link between plagioclase dissolution and biodegradation of the present oil column. It is, therefore, proposed that acid components from biodegradation selectively reacted with albitic plagioclase to form kaolin, releasing sodium bicarbonate into the residual water. The plagioclase-free sandstones contain more kaolin than the plagioclase-bearing sandstones, as would be expected due to aluminium conservation. However, the wide and overlapping ranges of kaolin content in both groups suggest that most of the kaolin originated from processes other than biodegradation-driven plagioclase alteration, potentially including both epigenetic and mesogenetic dissolution, as well as deposition of detrital kaolin and kaolin precursors. 相似文献
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Wolfgang W. Ehrenberg 《Theoretical and Applied Climatology》1953,4(4):470-482
Zusammenfassung Die Erhöhung bzw. Verminderung der Strahlungsabsorption und-reflexion durch farbändernde Oberflächenschichten ist ein physikalisches Analogon zur positiven bzw. negativen Katalyse. Die Konsequenzen einer Farbänderung unter verschiedenen äußeren Bedingungen lassen sich durch Vergleich mit gewissen Grenzfällen charakterisieren.Die Verdunstungsverluste des Feuchtigkeitsgehalts von dunklem Erdboden ließen sich durch Weißbestäubung auf die Hälfte reduzieren. Für die mit abnehmender Schichtdicke zunehmende zusätzliche Heiz- bzw. Kühlleistung pro Farbgewicht gibt es bei gegebener Strahlungsintensität einen materialabhängigen oberen Grenzwert. Die von der färbenden Schicht im Laufe ihrer mittleren Lebensdauer zusätzlich in Wärme verwandelte bzw. daran verhinderte Energie betrug bei unseren Versuchen pro Gewichtsaufwand ein Vielfaches der mit chemischen Umsetzungen verbundenen Energien.
Summary Increase or decrease of radiation absorption and reflection by change of colour of the superficial layers is considered as a physically analogous case of positive or negative catalysis. The consequences of a colour change under different external conditions can be characterized by comparison with certain boundary cases. Losses of moisture content of dark soil by evaporation could be reduced to the half by covering the surface with white dust. There exists a material dependent upper boundary value of the additional heating or cooling effect per weight unit of colour increasing with decreasing thickness of the layer. With our experiments, the energy additionally transformed into heat or prevented from being transformed into heat by the colouring layer in the course of its life amounted, per unit of weight, to many times the multiple of the energies connected with chemical conversions.
Résumé L'accroissement et la diminution du pouvoir absorbant et réflexif de couches superficielles changeant de couleur est un phénomène analogue à la catalyse resp. positive et négative. On peut caractériser les conséquences d'un changement de couleur sous différentes conditions extérieures par une comparaison avec certains cas limites.Les pertes d'humidité par évaporation d'un sol sombre ont pu être réduites de moitié par aspersion de poussières blanches. Lorsqu'une couche de couleur diminuant d'épaisseur voit augmenter son pouvoir chauffant ou réfrigérant par unité de poids de couleur, il existe pour une intensité donnée de rayonnement une valeur limite supérieure dépendant de la substance. L'énergie supplémentaire transformée en chaleur, ou celle qui n'a pu l'être, par la couche de couleur au cours de sa vie moyenne s'est élevée dans nos essais à un multiple de celle qui résulte de transformations chimiques, par unité de poids.相似文献
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S.N. Ehrenberg 《Earth and Planetary Science Letters》1982,57(1):191-210
Mineral and whole-rock REE abundances in garnet lherzolite and megacrystalline nodules from The Thumb display broad correlations with major element compositions. Lherzolites with > 12 modal % clinopyroxene plus garnet (“high-CaAl lherzolites”) have relatively flat chondrite-normalized whole-rock REE patterns. Lherzolites poor in clinopyroxene and garnet (“low-CaAl lherzolites”) have lower HREE in clinopyroxenes and garnets and higher whole-rock LREE/HREE. It is concluded that the low-CaAl lherzolites may have undergone LREE metasomatism after depletion of the major element compositions by partial melting and that much of the garnet now present was originally dissolved in aluminous orthopyroxene. The high-CaAl lherzolites may be interpreted either as primordial mantle samples or as products of equilibration with very LREE-enriched liquids. The “megacrystalline” nodules are medium- to ultracoarse-grained intergrowths and megacrysts with mineral compositions similar to discrete nodule suites in kimberlites. The REE abundances of the megacrystalline minerals are consistent with an origin as cumulates from magma with extremely fractionated REE, similar to minette or kimberlite.The patterns of correlation of REE and major elements in this inclusion suite are similar to the patterns observed in the garnet lherzolite and discrete nodule suites of southern African kimberlites. Both of the subcontinental mantle provinces represented by these suites contain three distinct petrogenetic components: refractory garnet lherzolite enriched in LREE and depleted in HREE, fertile garnet lherzolite with generally chondritic REE abundances, and a suite of ultracoarse minerals precipitated from magma with extremely fractionated REE generally similar to the host magmas. 相似文献
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Some garnet peridotite nodules from The Thumb, a minette neck on the Colorado Plateau in the southwestern United States, contain
zoned minerals. Zoning does not exceed 1.5 wt.% for any oxide, but some relative changes are large: in one garnet TiO2 and Cr2O3 ranges are 0.05–0.65 and 3.5–5.0 wt.%, respectively. In two porphyroclastic nodules, garnet rims are depleted in Mg and enriched
in Fe, Ti, and Na compared to cores, and one garnet is irregularly zoned in Ti and Cr. Olivine crystals in these rocks are
unzoned, and pyroxene zoning is slight, yet matrix olivine and pyroxene contain more Fe and Ti and less Mg and Cr than inclusions
of these phases in garnet. In three coarse nodules, garnet rims are Ti-rich compared to cores, and Ca, Fe, Mg, and Cr zoning
patterns are complex. Several nodules appear to have partially equilibrated near 1200° C and 35 kb, and under these conditions
cation mobility in pyroxene was greater than in garnet.
The zoning partly reflects Fe and Ti metasomatism in the mantle. Calculations indicate that Fe-Mg gradients in garnet could
have persisted for only a short time in the mantle, perhaps thousands of years or less, so the metasomatism occurred shortly
before eruption. The minette host, a likely source of the Fe and Ti, is rich in light rare earth elements: since the nodules
are much poorer in these elements, little or no infiltrated minette was trapped in them. Diffusion is a possible mechanism
for nodule metasomatism. Some fertile peridotite nodules from kimberlites may have been affected by similar events. Compositional
differences between inclusions in garnet and matrix phases are intriguingly similar to some of the differences between most
peridotite inclusions in diamonds and common lherzolite phases. 相似文献
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In recent years, acoustic techniques have been used extensively to monitor and quantify fish stocks remotely. One of the parameters that is often measured is the target strength of the individual fish in the population. To obtain the target strength of a fish from its acoustic echo, the effect of the transducer beam-pattern factor must be removed from the echo amplitude. This paper discusses a number of different approaches for directly estimating the beam-pattern factor for an individual fish target. The effects of noise and interfering signals on the various estimation techniques are investigated. Expressions are derived for the bias and variance in the estimates of the beam-pattern factor as a function of signal-to-noise ratio and angular location of the target. Results of a Monte Carlo simulation of the effect of interference on the various processing techniques are presented. Some of the problems encountered in implementing the various techniques are discussed. 相似文献
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