Microstructures of AIPO4 subjected to high shock pressures

Berlinite single crystal specimens were shocked to peak pressures 12 and 24 GPa. Specimens were placed in an Al capsule to minimize shock-wave reflections at interfaces between specimen and capsule. Shock pressures were achieved with a 6.5-m-long two-stage gun. The shock-induced microstructures in recovered specimens were then investigated by Transmission Electron Microscopy. In the sample shocked at 12 GPa, the prominent shock-induced defects are dislocations and basal a glide appears to be the only glide system activated. In contrast, the sample shocked at 24 GPa exhibits no dislocations. The material is partially converted into an amorphous phase occurring under the form of thin amorphous lamellae parallel to the }10 $\bar 1$ n{ planes (n=0, 2, 3, 4). This microstructure is very similar to the one observed in experimentally shocked quartz.     

Mechanical twinning in diopside Ca(Mg,Fe)Si2O6: Structural mechanism and associated crystal defects

Diopside twins mechanically on two planes, (100) and (001), and the associated macroscopic twinning strains are identical (Raleigh and Talbot, 1967). An analysis based on crystal structural arguments predicts that both twin mechanisms involve shearing of the (100) octahedral layers (containing Ca²⁺, Mg²⁺ and Fe²⁺ ions) by a magnitude of c/2. Small adjustments or shuffles occur in the adjacent layers containing the [SiO₄]^4? tetrahedral chains. While the (100) twins are conventional with shear parallel to the composition plane, this analysis predicts that (001) twins form by a mechanism closely related to kinking. A polycrystalline diopside specimen was compressed 8% at a temperature of 400° C, a pressure of 16 kilobars, and a compressive strain rate of about 10^?4/s. Transmission electron microscopy on this specimen has revealed four basic lamellar features:

1. (100) mechanical twin lamellae;
2. (100) glide bands containing unit dislocations;
3. (001) twin lamellae;
4. (101) lamellar features, not as yet identified.

The (001) twins often contain remnant (100) lamellae of untwinned host. Twinning dislocations occur in these (100) lamellae and in the (001) twin boundaries with very high densities. Diffraction contrast experiments indicate that the twinning dislocations associated with both twin laws glide on (100) with Burgers vector b=X [001] where X is probably equal to 1/2 on the basis of the structural analysis. Parallels are drawn between mechanical twinning in clinopyroxenes and clinoamphiboles. The exclusive natural occurrence of basal twins in shock-loaded clinopyroxenes and of analogous ( \(\bar 1\) 01) twins in clinoamphiboles is given a simple explanation in terms of the relative difficulty of the “kinking” mechanism as compared to direct glide parallel to the composition plane.     

Petrochemistry of the volcanic rocks of the Island of Principe,Gulf of Guinea

Principe is one of the volcanic centres comprising the Cameroun line in West Africa. The volcanic rocks can be divided into two stratigraphic units:

1. Younger lava series — basanite and nephelinite overlying.
2. Older lava series — transitional to mildly alkaline basalt and hawaiite.

These units lie on a basement of palagonite breccias of tholeiitic affinities. The basic lavas are intruded by plugs ranging in composition from tristanite to phonolite and are overlain by phonolite lavas. These rocks form two chemically and mineralogically distinct suites:

1. Phonolites which evolved by low pressure crystal fractionation of the younger lava series basanitic magma, and
2. Tristanite — trachyte — trachyphonolite suite which may have evolved by high pressure crystal fractionation of the older lava series magma.

     

Altération supergène des protores à grenats manganésifères dans quelques gisements d'Afrique de l'Ouest

The wet tropical weathering of Precambrian spessartite quartzites leads to the formation of secondary oxidized ores. These ores result from different successions of superimposed elementary processes, among them:

garnet hydrolysis: Mn, Ca, and Fe are leached, and only an amorphous, silicoaluminous phase remains.

lithiophorite neoformation: Added manganese combines with alumina of the amorphous, Si-Al products.

leaching: Voids appear in the central part of the weathered garnets. They may widen, leaving only the quartz matrix with polyhedric voids.

epigenic replacement: The quartz is replaced by cryptomelane, while the garnets may remain unweathered.

The various ore types are characterized by the sequence of transformations and by the volumes that each transformation affects. These transformations are old because they are observed not only in situ ores but also in removed detrital ores. In the same way the major part of the accumulated stocks of oxidized ores must be old.     

Kyanite eclogites

Prior experimental work has shown that in the laboratory the mineralogy of eclogites is sensitive to the ratio of CaO ∶ MgO ∶ FeO and that the reaction pyroxene + kyanite?garnet + quartz proceeds to the right at high pressures in rocks rich in magnesium and to the left in rocks rich in calcium and iron. Typical basalts crystallized at high pressure never contain kyanite. The chemistry and mineralogy of a large number of naturally occurring eclogites show they belong to three classes.

1. Kyanite-free magmatic eclogites, rich in magnesium, from:
2. kimberlites
3. dunites and serpentinites.
4. Kyanite-bearing eclogites and grosspydites rich in CaO and low in FeO with intermediate MgO from:
5. kimberlites
6. gneisses.
7. Kyanite-free eclogites of metamorphic origin rich in iron with low magnesium and intermediate amounts of calcium from:
8. glaucophane schists
9. gneisses.

     

The Araguainha astrobleme/Central Brazil

The following facts have supported the origin of the Araguainha circular structure in Central Brazil by a meteoritic impact:

1. the almost circular contour
2. the impact-morphologic sequence including a central uplift, ring walls and a basin rim of escarpments
3. outcrops of suevites and mixed breccias
4. the evidence of shock metamorphism
5. the presence of shatter cones, and
6. negative anomalies of the total intensity of the magnetic field at the center of the ring structure.

     

Zur Anwendung der Kathodolumineszenz in der Karbonatpetrographie

Mn-activated cathodoluminescence can be used in several fields of carbonate petrography. It may, for instance, be possible to recognize

1. cement sequences and their correlation (Tab. 1, Figs. 1, 2, 4; Tab. 2, Fig. 1)
2. growth fabrics of skeletons (Tab. 2, Figs. 2, 3, 4; Tab. 3, Figs. 1, 2)
3. dolomitisation processes and problems (Tab. 1, Figs. 1, 2; Tab. 4, Fig. 2)
4. transformation paths from Mg-calcite to calcite and from aragonite to calcite (Tab. 2, Fig. 1; Tab. 3, Figs. 3, 4; Tab. 4, Fig. 1)
5. growth structures in certain types of ooids (Tab. 1, Fig. 4; Tab. 3, Fig. 3; Tab. 4, Fig. 1)
6. reworked skeletal particles (Tab. 3, Fig. 4)
7. phantom grains and fossil-outlines in a micro- or macrocrystalline groundmass (Tab. 4, Figs. 2, 3)
8. healed fissures crossing micro- or macrocrystalline carbonate rocks (Tab. 4, Fig. 4).

These are, however, no general luminescence criteria indicating the depositional environment. Luminescence of calcite and dolomite requires 20–40 ppm Mn, with the equipments used in this study. Aragonite is not yet investigated systematically. Zonal luminescence in carbonate cements may indicate changes of the chemical composition of the aquifer and may be used for “cement stratigraphy”. In skeletons it rather indicates physiological changes. While aragonitic skeletons lose their luminescence Zonation during replacement by calcite, Mg-calcite skeletons may keep parts of it, because their replacement preserves the original crystal fabric. Blotchy luminescence developes in Mg-calcitic particles during their adjustment to lower Mg-calcites by dissolution-precipitation processes in solutions with changing Mn/Fe-ratios.     

Deformation of shock-loaded andalusite studied with X-ray diffraction techniques

The structural deformation of an andalusite single crystal, shockloaded up to 400 kb with shock wave direction approximately parallel to c, was investigated by means of X-ray powder (Guinier) and single crystal techniques (Weissenberg, precession). Exposure to the dynamic pressure revealed a fracturing of the crystal into lattice blocks, with a mean size >1,000 Å. No change of the lattice constants could be observed after pressure release. From the streaks of X-ray reflection spots measured within the hk0, h0l, 0kl, and hhl planes the shock-induced lattice deformation is interpreted in terms of rotational gliding and/or microfracturing. The distortion mode is highly structure controlled. It follows preferrably two different structural motion systems: (1) Gliding parallel to (001) occurs, which produces lamellae parallel to (001), mainly arranged in two sublattices with common c-axis. The stacking sequence of lamellae along c is irregular. The lamellae-type structure may also result from an orientated transformation into a high pressure phase of lower symmetry and subsequent inversion into the original phase after pressure release. (2) Gliding parallel to (100) occurs. In this case the deformation mode is asymmetrical with respect to the undistorted crystal. The common direction b of the (001) and (100) deformation planes is probably the main direction of the shock-induced lattice deformation.     

Geologische und geochemische Untersuchungen im Zentralgneis und in der Greiner Schiefer Serie (Zillertaler Alpen,Tirol)

Geologic, petrological and geochemical investigations have been carried out in the western part of the “Zillertaler Alpen”. Important results are:

1. The premetamorphic material of the Greiner series consists of conglomerates, breccias, arcosic-sandstones or greywackes, bituminous shales, volcanic lavas and tuffs.
2. The southern part of the “Zentralgneis” shows a differentiation trend from alkaline granite to quarzdiorite with predomination of granodiorite.
3. Chemical relationships of granodiorite to its restitic inclusions allow the supposition of a palingenetic origin of the granitic rocks.
4. At least two stages of metamorphism can be differentiated.
5. Parts of the Greiner series, covered by triassic metasediments, are supposed to be of Permian age. A lower age boundary can not yet be given.
6. Some vertical, northeast striking faults with throws of more than 1 or 2 kilometers produced southward verging drag folds.
7. Geodynamic aspects, revealed from regional metamorphism and tectonics, are discussed.

     

Forest condition and forest damages — contribution of remote sensing to different inventory approaches

The development of inventory activities in the field of forest damage assessment and monitoring during the last decade in Germany and the present state are recorded as far as remote sensing has been involved. Any forest inventory is influenced by external factors, and the resulting difficulties for an introduction of new technologies are described. The following tasks and/or methods are discussed:

-global approaches to deforestation monitoring

-working experience from local and regional case studies

-vegetation and vegetation-damage monitoring in ”urban forestry”

-sampling approaches for large areas

-the contribution of spectral signatures and satellite remote sensing to damage assessment

     

The structural geology of the Dalradian rocks of Slieve Gamph,Cos. Mayo and Sligo,Western Ireland

The paper presents novel information on the Caledonian orogeny in Ireland. A series of Dalradian (Upper Precambrian-Lower Cambrian) metasedimentary rocks occur as an envelope to a granitic igneous complex at Slieve Gamph, Western Ireland. These metasedimentary rocks have been deformed at several distinct times and evidence is shown for the following sequence of events:

1. formation of major nappe structures and a tectonic slide. The axial-plane traces of the folds probably trended N. E.-S. W.
2. formation of upright, gently plunging folds with axial-plane traces of the folds trending N. E.-S. W. Emplacement of the components of the Slieve Gamph igneous complex.
3. formation of a conjugate set of folds:
   1. Open folds with N. N. E.-S. S. W. trending axial-planes which dip to the east,
   2. Open folds with E.W. trending axial-planes which dip to the north.
4. formation of kink-bands, open and conjugate folds with an axialplane trace trending N. W.-S. E.

Late phase of faulting. No isotopic dates are available for these structural events.     

Low temperature\lg f_{O_2 } - pH diagrams of sulfur isotope evolution in an equilibrium hydrothermal system

According to Sakai-Ohmoto's theory regarding the evolution of sulfur isotopes in hydrothermal systems, in conjunction of new data on chemical resaction equilibrium constants and equilibrium isotopic fractionation factors as well as on individual ion activity coefficients of aqueous sulfur species, the following lgfo₂.-pH diagrams are constructed:

1. mole fractions of aqueous sulfur species (X _i ),
2. stability fields of some minerals in the Fe-S-O system,
3. diagram depicting the oxidation-reduction-state ratio for aqueous sulfur species (R′)
4. isotopic compositions of sulfur compounds ( \(\delta S_1 ^{34} \) ).

     

Environmental impacts by input of substances in landscapes of the District (Bezirk) of Leipzig,Germany

Problems of landscape and resource protection resulting from the intensification of land-use can be mastered only by intersectoral planning and a land management considering (landscape-)ecological principles right from the beginning. In the district of Leipzig ecological studies in the '80ies have focussed on:

1. Determination of the regional pattern of atmospheric immissions;
2. Registration of heavy metals in soil and vegetation;
3. Soil compaction, soil erosion;
4. Study of stress indicators in the aeration zone and in the top-most aquifer in order to examine barrier effects in the percolation process.

First results are discussed.     

China’s crust-and mantle-source pegmatites and their discriminating criteria

According to their material sources, China’s pegmatities can be divided into two broad types: (1) the crust-source pegmatites derived mainly from the upper continental crust, which can be subdivided into metamorphic differentiated, mixed metasomatic and anatectic magmadifferentiated pegmatites, and (2) the mantle-source pegmatites generated from the mantle, including those related to late differentiates and carbonatites. In space, carbonatites are usually accompanied with alkaii syenite. The criteria of discriminating the two-source pegmatites of China are listed as follows:

1. Rock-forming minerals (micas and feldspars);
2. REE distribution patterns;
3. Zr/Hf ratios in zircons; and
4. Species of apatite and REE contents.

     

Geochemistry and origin of granitic rocks,Scourian Complex,NW Scotland

Concordant granite sheets from the granulite facies Scourian Complex, N.W. Scotland exhibit the following features:

1. a common planar fabric with their host pyroxene granulites;
2. the presence of an exsolved ternary feldspar phase;
3. a low-pressure, water-saturated minimum composition;
4. K/Rb ratios (450–1,350) distinctly higher than most upper crustal granites but similar to the surrounding granulites;
5. low absolute concentrations of the rare earth elements (REEs), light REE enrichment, and large positive Eu anomalies.

It is proposed that the granite sheets have originated by anatexis of gneisses undergoing granulite facies metamorphism — gneisses that were already essentially dry and depleted in incompatible elements. Their unusual trace element chemistry may be explained by either disequilibrium melting and/or sub-solidus reequilibration of the granite sheets with the surrounding gneisses. Isotopic and trace element data suggest that cross-cutting, potash-rich pegmatites represent reworking of the granite sheets during a later amphibolitization.     

Natural hazard mapping

Systematic natural hazard mapping in Japan was started after WW II using aerial photographs. Analysing the interaction between disaster occurrence and land conditions is the most useful method for establishing the disaster prediction system for three types of disaster, flood disaster, mass-movement disaster, and earthquake disaster, which are strongly related to land conditions. A series of maps on natural hazards were established based on the results analysed. In our opinion, the following problems of natural hazard mappings remain so far unsolved:

1. No clear distinction is made between natural hazard mapping and land classification.
2. Organization of information for natural hazard prevention is not yet established.
3. There is no established earthquake disaster prevention map.
4. Utilization of new machines and tools is inadequate.
5. Effect of human activity is not estimated.

     

Palynology of the circum-mediterranean triassic: Phytogeographical and palaeoclimatological implications

Following a tentative evaluation of palynological information from Ladinian and, more particularly, Karnian successions, there seems to be every indication that qualitative and quantitative compositional differences of palynological assemblages could well be applied in testing concepts of Triassic phytogeography and palaeoclimatology. The following implications are emphasized:

1. There is sufficient palynological evidence that the Mediterranean region includes a domain of mixed northern (Laurasian) and southern (Gondwana) types of floras.
2. The concept of an essentially arid nature of a wide equatorial climatic belt during Triassic times finds palynological support.
3. Palynological evidence does not contradict a concept of pronounced decrease in precipitation towards the western part of the Mediterranean region.
4. In Europe, occurrences of hygrophytic palynofloras and coals within an arid climatic zone can be explained by the water-supply of extensive river-systems.

     

The “South-Italian City” — a cultural-genetic type of city

The “South-Italian city” is characterized at four different levels as an independent cultural-genetic city-type:

1. The characteristics arrangement of the functional areas and the residential areas of different social groups is represented in a model.
2. From the model, developments and changes in the arrangement of the functional areas can be identified which clearly deviate from those which are derived from the universal city model.
3. Some of the structural individuality can be directly explained by the peculiar features of the respective social and economic history.
4. Some of the special features must, however, be traced back to a wider historico-cultural background. Through this run processes which flow through the universal city development in similar forms, to the deviating structure of the “South-Italian city”.

     

La lherzolite à amphibole du gisement de Caussou (Ariège,France)

The Caussou outcrop consists mostly of a spinel-bearing lherzolite with irregular patches of amphibole lherzolite. The characteristic paragenesis of the latter is: forsterite + bronzite+Ti-rich K-bearing pargasite ± diopside, with 10 to 15% amphibole in the rock. Petrographic and chemical analysis of the two types of rocks and their constituent minerals lead to the conclusion that the spinel-lherzolite recrystallized locally as amphibole lherzolite in the presence of a gas phase containing water, and probably Ti and alkali elements as well, at approximately 7 to 8 Kb and 1100° C (for \(P_{{\text{H}}_2 {\text{O}}} = P_{{\text{total}}} \) ). Two hypothesis could account for this local recrystallization:

1. The amphibole lherzolite could represent a subsolidus recrystallization of the spinel lherzolite occuring in the stability field of plagioclase lherzolite at the time of the emplacement.
2. Or, in the same P-T conditions, the Ti-pargasite could precipitate from a liquid of nephelinite composition produced by limited partial melting of the spinel lherzolite.

In either case the original peridotite that produced the two existing types at Caussou could be considered as an undifferentiated fragment of the upper mantle.     

Utilisation of loess for soil amelioration

In Hungary loess has long been used for soil reclamation. The main steps of the method are: horizon A and B are removed from a suitable area and their material is stockpiled at the margins of the resulting pit. The loess (horizon C), this way exposed, is excavated and spread over the salt affected soils to be improved then mixed with their upper layer. The pit is named in Hungarian digó (pit). The name of the reclamation process is the digo method or spreading of yellow earth. Digó method is mainly used for the amelioration of salt affected soils with an acid A horizon and its benefits are as follows:

1. The acidity of the horizon A is eliminated
2. The soil structure is improved
3. The amount of calcium (a plant nutrient) is increased
4. Soil fertility is improved continuously
5. The soil depth is extended which adds to the relative volume of the ground water table.