运用轻便触探和静载荷试验研究黄土的湿陷性(英文)

黄土在应力作用下迂水时力学强度迅速下降 ,产生大范围的快速沉陷。这就是黄土的湿陷性 ,是黄土的诸多特性之一。鉴于对黄土湿陷性以往用各种实验室试验指标进行评价 ,这里提出运用动力触探和静载荷试验进行黄土湿陷性原位评价的一种简便的新方法。该方法的试验程序是 ,先用轻便可变动能触探仪在天然状态和饱水状态下进行触探试验 ,而后在触探孔完成静载荷压缩性试验。运用中国黄土高原黄土原位动力触探和静载荷试验测得的资料 ,详细分析了天然状态的黄土对探头阻力 qdnat,饱水状态的黄土对探头阻力 qdsat,实验室测得的湿陷性指数s压缩曲线参数 (即触探极限压力 ppf,触探蠕变压力ppl 和触探载荷模量Epn)的关系。结果证明所提出的方法适用于原位判定黄土的湿陷性。     

Gefüge und Vulkanotektonik im Vogelsberg (Niederhessen)

Zusammenfassung Am Vogelsberg wurde erprobt, inwieweit rheologische Gefüge-Untersuchungen den Bau von Vulkankomplexen aufzuhellen vermögen. Lineare Merkmale (Blasen, Rücken, Rinnen, Kontraktionsklüfte, Fluidaltextur) und vektorielle (Blasenröhren, Blasenzüge, Faltenvergenz) wurden an vielen Punkten in größerer Zahl gemessen und statistisch verarbeitet. Es ergab sich, daß alle Merkmale für örtliche Störungen stark anfällig sind. Trotzdem hat die Methode, kritisch verwandt, ihren Wert.Der Vogelsberg hat seinen gegenwärtigen rundlichen Umriß wohl einer späteren leichten Caldera-Senkung zu verdanken.

---

In the case of the Vogelsberg the question was discussed, if the observation of flow fabrics in lava may offer advantages for the understanding of volcano complexes. Linear characteristics (vesicles, ridges, channels, contraction joints, fluidal texture) and vectorial ones (spiracles, pipe vesicles, vergent folds) were measured and statistically evaluated. All flow characteristics are highly susceptible to local conditions. But nevertheless, rheological methods are, critically applied, valuable.The present circular outline of the Vogelsberg probably results from a slight postvolcanic caldera subsidence.

---

Résumé A propos du Vogelsberg on a abordé le problème, si la détermination des traces d'écoulement dans les laves peût éclaircir la genèse des complexes volcaniques. Des caractéristiques linéaires (amygdales, arêtes, sillons, fissures de contraction, texture fluidale) et vectorielles (spiracules, tubes à vésicules, plis vergents) furent mesurés et calculés selon les règles statistiques. Il en résulte, que toutes les traces rhéologiques dépendent sensiblement des conditions locales d'écoulement. Mais malgré cela, la méthode, employée avec critique, est précieuse. Le Vogelsberg a reçu son présent contour circulaire par un léger effondrement de caldéra.

---

. ( , , , ) ( ). . , .

---

---

Bei den Begehungen und Messungen waren dankenswerter Weise eine Reihe Bonner Geologie-Studenten behilflich, vor allem Dr.Clausen und Dr.Weber. Herrn Dr. W.Schenk-Hungen und Herrn Dr.Matthes-Wiesbaden danke ich für Erörterungen und Auskünfte.     

Quick-clay microstructure

The article deals with a quick clay which was originally deposited in sea water. By leaching in situ the salt content has been reduced to a very small value.

By using a special technique for step-wise replacement of pore water with acrylate plastic, 500Aothick sections were cut with a precision microtome. The sections were photographed in an electron microscope and the micrographs obtained could be used for a study of the clay microstructure.

The microstructure is characterized by a linkage of groups or chains of small particles in and between denser flocs or aggregates or between bigger particles. There is no preferential orientation either of small or of bigger particles.

A preliminary study of the quick clay and of unleached parts of the same clay stratum has not revealed any microstructural differences.

The extreme thinness of the clay sections means that the micrographs reveal pores larger than about 500Ao. Thus the micrographs give a fairly complete picture of the size and shape variation of the micropores in the clay. By measuring the maximum dimension of all pores which could be identified and by using suitable methods for statistical condensation, representative values of mean pore size and two-dimensional “porosity” were obtained. These characteristics are discussed in relation to the permeability and strength properties of the quick clay and of some fresh- and brackish-water deposited clays which have been investigated previously.

Finally, on the basis of the micrographs a hypothesis is made concerning the rate of settlement.     

Iodine Chemistry and its Role in Halogen Activation and Ozone Loss in the Marine Boundary Layer: A Model Study

A detailed set of reactions treating the gas and aqueous phase chemistry of the most important iodine species in the marine boundary layer (MBL) has been added to a box model which describes Br and Cl chemistry in the MBL. While Br and Cl originate from seasalt, the I compounds are largely derived photochemically from several biogenic alkyl iodides, in particular CH2I2, CH2ClI, C2H5I, C3H7I, or CH3I which are released from the sea. Their photodissociation produces some inorganic iodine gases which can rapidly react in the gas and aqueous phase with other halogen compounds. Scavenging of the iodine species HI, HOI, INO2, and IONO2 by aerosol particles is not a permanent sink as assumed in previous modeling studies. Aqueous-phase chemical reactions can produce the compounds IBr, ICl, and I2, which will be released back into the gas phase due to their low solubility. Our study, although highly theoretical, suggests that almost all particulate iodine is in the chemical form of IO-3. Other aqueous-phase species are only temporary reservoirs and can be re-activated to yield gas phase iodine. Assuming release rates of the organic iodine compounds which yield atmospheric concentrations similar to some measurements, we calculate significant concentrations of reactive halogen gases. The addition of iodine chemistry to our reaction scheme has the effect of accelerating photochemical Br and Cl release from the seasalt. This causes an enhancement in ozone destruction rates in the MBL over that arising from the well established reactions O(1D) + H2O 2OH, HO2 + O3 OH + 2O2, and OH + O3 HO2 + O2. The given reaction scheme accounts for the formation of particulate iodine which is preferably accumulated in the smaller sulfate aerosol particles.     

Hydrothermal alteration as a control of regional geochemistry and ore formation in the central Baltic Shield

In a geochemical study of the Proterozoic volcano-sedimentary Bergslagen ore province in central Sweden, more than 1000 eruptive rocks were analyzed for main and trace elements. The volcanic rocks form a bimodal suite dominated by rhyolites but deficient in andesites. Igneous geochemical variation bears little relevance to the occurrence and distribution of ores which mostly appear related to secondary alteration patterns. Hydrothermal metasomatic alteration occurs on a regional scale and has affected markedly more than half of the 732 analyzed, macroscopically fresh, porphyritic volcanic rocks. Metasomatism produced extreme Na- and K-differentiation, and Fe-Mg-Si relationships incompatible with igneous variation patterns. Enrichment in Na and Mg, and leaching of ore-forming metals are prominent in the lower parts of the volcanic pile, whereas meta-volcanics enriched in K and volcanogenic sediments associated with ores and marbles dominate the upper levels. The metasomatic alteration of the volcanic rocks and the formation of most ores are two aspects of a comprehensive process of hydrothermal convection which circulated sea water, extracted the ore-forming elements from the lower levels of the volcanic pile and enriched them at or close to the top of the volcanic sequence.

---

Zusammenfassung Über 1000 proterozoische Eruptivgesteine der vulkanisch-sedimentären Erzprovinz in Mittelschweden wurden auf Haupt- bzw. Spurenelemente analysiert. Die Gesteine bilden eine Folge mit Schwerpunkt auf basaltischen und insbesondere rhyolitischen Zusammensetzungen, während Andesite nur schwach vertreten sind. Die primärmagmatische Zusammensetzung hat wenig Bezug zu den Erzen, die genetisch größtenteils an sekundäre Veränderungen gebunden sind. Hydrothermale Metasomatose hat eine regionale Verbreitung. Auch von den makroskopisch intakten, 732 analysierten, sauren porphyrischen Eruptivgesteinen sind mehr als die Hälfte durchgreifend verändert. Die metasomatischen Prozesse führten zu extremer Natriumund Kaliumdifferenzierung und zu Fe-Mg-Si-Beziehungen, die nicht auf magmatische Differentiation zurückzuführen sind. Anreicherung von Na und Mg und Auslaugen der erzbildenden Metalle treten in den tieferen Teilen der vulkanischen Schichtenfolge auf. Die höheren Lagen werden von kalireichen Metavulkaniten, Karbonatgesteinen und vulkanogenen, erzassoziierten Sedimenten beherrscht. Metasomatische Gesteinsumwandlung und Erzbildung sind zwei Teilprozesse einer großräumigen hydrothermalen Konvektion, durch die Meereswasser durch die Schichtenfolge getrieben wurde. Die erzbildenden chemischen Bestandteile wurden dabei den tieferen Teilen des Vulkanitpaketes entzogen und an oder nahe der Oberfläche angereichert.

---

Résumé Dans le cadre d'une étude géochimique de la province protérozoïque volcano-sédimentaire minéralisée de Bergslagen (Suède centrale), plus de 1000 échantillons de roches magmatiques ont été analysés (éléments majeurs et traces). Ces roches volcaniques forment une suite dominée par les rhyolites et les basaltes, tandis que les andésites sont peu représentées. Les variations géochimiques montrent peu de relation avec la distribution des minerais, ceux-ci étant surtout engendrés lors de processus d'altération secondaires. En effet, une métasomatose hydrothermale s'est manifestée à l'échelle régionale au point d'affecter plus de la moitié des 732 porphyres volcaniques acides analysés, en dépit de l'aspect de fraîcheur qu'ils présentent macroscopiquement. La métasomatose se traduit par un fractionnement extrême de Na et K, ainsi que par des relations entre Fe-Mg-Si incompatibles avec la différenciation magmatique. La partie inférieure de la série volcanique stratifiée montre un enrichissement en Na et Mg ainsi qu'un lessivage des métaux des minerais. Dans la partie supérieure de la série, les termes dominants sont des métavolcanites riches en K, des marbres et des sédiments volcanogènes associés aux minerais. La modification métasomatique et la genèse des minerais sont deux aspects d'un vaste processus de convection hydrothermale qui a fait circuler l'eau de mer à travers la pile stratifiée, en enlevant les métaux des minerais dans la partie inférieure pour les concentrer dans la partie pouche du sommet.

---

1000 - . , , ; . ; . . 732 , . , , , . . , , , , , . — , , . .

     

Tektonische Standardnetze und Beanspruchungspläne für Erde und Mars

Zusammenfassung Bei einer Untersuchung der azimutalen Verteilung der Mars-Lineationen wurden markante Maxima bei 0°, 50°, 90° und 140° aufgefunden. Da die gleichen Richtungen auch bei Auswertungen tektonischer Messungen auf der Erde, besonders bei photogeologischen Untersuchungen häufiger zu beobachten sind, wird die Frage nach der Existenz eines tektonischen Standardnetzes aufgeworfen. Die photogeologischen und tektonischen Konsequenzen und die möglichen Ursachen eines Standardnetzes werden angesprochen und der für ein solches Netz wahrscheinliche globale Beanspruchungsplan diskutiert.

---

The azimuth distribution of Mars lineaments shows peaks at 0°, 50°, 90° and 140°. As the same master shear directions can be observed on the Earth, especially when using aerial photography or satellite imagery for tectonic analyses, the question of the existence of a tectonic standard net is raised.The consequences concerning photogeology and structural geology are discussed as well as the probable causes and the global stress/strain distribution leading to this form of a standard net.

---

Résumé Sur Mars, les directions principales des failles montrent des maxima de 0°, 50°, 90° et 140°. Comme on trouve les mêmes directions dominantes sur la Terre — surtout lors d'analyses photogéologiques — la question d'un «réseau standard» est soulevée.Les conséquences regardant la photointerprétation et la tectonique sont discutées ainsi que les causes probables et le plan global de la distribution des efforts tectoniques conduisant à un tel réseau.

---

0°, 50°, 90° 140°. .. , , , . .

     

Nitrogen and phosphorus distribution and utilization bySpartina alterniflora in a Louisiana gulf coast marsh

Nitrogen and phosphorus content ofSpartina alterniflora Loisel and soil nitrogen were measured along a transect perpendicular to a stream in a Louisiana salt marsh in order to provide information on differences between the so-called streamside and inland regions. Total plant nitrogen and phosphorus levels in June and September tended to be greater at streamside than inland sites. Total soil nitrogen on a dry soil weight basis increased with distance inland from a natural stream toward an interdistributary basin in the marsh. Soil extractable ammonium-nitrogen levels measured in June were very low in vegetated streamside and inland areas, but they were much higher in inland areas devoid of plants. Nitrogen and phosphorus utilization byS. alterniflora was also investigated at an inland location in the salt marsh. Labelled ammonium-nitrogen and phosphate-phosphorus were added in May at a rate of 200 kg/ha to the soil of replicated plots. Added nitrogen significantly increased total above-ground plant biomass and plant height by 28 and 25%, respectively, 4 months after application. The ratio of belowground macro-organic matter to total aboveground biomass was decreased from 5.7 to 4.7 by the additional nitrogen. Added phosphorus did not significantly affect plant height and biomass. The use of¹⁵N-depleted nitrogen tracers showed that about half of the nitrogen in the aboveground portion ofS. alterniflora from 1 to 4 months after the nitrogen addition was derived from the added ammonium-nitrogen. After 4 months, 28 and 29% of the added labelled nitrogen was recovered in the aboverground and belowground biomass ofS. alterniflora, respectively. Recovery of added nitrogen was overestimated with a non-tracer method based on the difference in total nitrogen uptake between nitrogen-amended plots and untreated plots. Soil organic nitrogen comprised the majority of the nitrogen in the salt marsh. Nitrogen in the standing crop biomass ofS. alterniflora represented only about 2% of the total nitrogen in the plantsoil system of an inland marsh to a 20 cm soil depth.     

Isotopic constraints on the genesis and age of autochthonous glaucony in the Oligo-Miocene Torquay Group, south-eastern Australia

The Oligo‐Miocene Torquay Group at Bird Rock in south‐eastern Australia comprises a sequence of fine‐grained skeletal carbonates and argillaceous and glauconitic sandstones, deposited in a cool‐water, mid‐shelf environment. The Bird Rock glaucony is autochthonous and consists predominantly of randomly interstratified glauconitic smectite, which constitutes bioclast infills and faecal pellet replacements. The results of Rb–Sr and oxygen isotopic analysis of samples taken from a single glauconitic horizon (the BW horizon) indicate that the glaucony developed through a series of simultaneous dissolution–crystallization reactions, which occurred during very early diagenesis in a closed or isochemical system, isolated from the ambient marine environment. The constituent ions of the glaucony were derived primarily from terrigenous clay minerals, but considerable potassium may have been sourced indirectly from sea water, through potassium enrichment of clay precursors. The pore fluids associated with glauconitization were marine derived, but progressively modified by the dissolution–crystallization of detrital clay minerals and autochthonous glaucony. Rb–Sr data for the BW horizon indicate that dating glauconies may be somewhat problematic, as co‐genetic glauconitic minerals can show a range of initial strontium compositions, which reflect the incorporation of strontium derived from mineralogical precursors and/or contemporaneous sea water. Rb–Sr isochrons indicate that the glaucony of the BW horizon formed at 23 ± 3 Ma. This age is in good agreement with both the established biostratigraphy and a ⁸⁷Sr/⁸⁶Sr age for the horizon (23 ± 1 Ma), but could only be determined using the independent age constraint and the estimate of the ⁸⁷Sr/⁸⁶Sr ratio of contemporaneous sea water provided by analysis of associated biogenic carbonate.