Dynamic Response Analysis of Interaction System of R.C. Gravity Single-Leg Platform

In this paper, the responses of the interaction system of R.C. gravity single-leg platform to seismic excitation are mainly analysed. A set of nonlinear equations for the interaction system are established by using the wave, one is the soil-structure interaction and the other is the fluid-structure interaction. The seismic response of the interaction system is analysed for the influence of the asymmetric structure, fluid action, etc. with the input of seismic SH waves in any direction. The numerical results are given for a simple example.     

Ship hull drag reduction using bottom air injection

The idea of bottom air injection to reduce ship hull resistance is not new. Early patents envisioned planing hull applications. Recent planing hull tests speed realized an increase of 7–12 knots. River barges and ship fitted with an air injection system results are presented to show a 10–15% reduction in the frictional resistance. Graphs for making initial estimates for displacement hulls with bottom air injection are presented. It is clear from these results that improvements in high speed planing catamarans and full form hull resistance can be realized by using bottom air injection.     

Total ozone variations in the tropical belt: An application for quality of ground based measurements

Summary The study of the regime of ozone variations in the huge tropical belt (25° S to 25° N), which are, in general, very small and zonally nearly symmetric, permits to establish a statistical model for estimating the ozone deviations using Total Ozone Mapping Spectrometer (TOMS) data. The equatorial stratospheric winds at 25 and 50hPa and the solar flux at 10.7 cm are used as major predictors and the linear trend was also estimated. The 10m/sec stratospheric wind change is related to1.2% ozone change at the equator, to practically no change in the 8–15° belts and up to 1.4% change with opposite phase over the tropics in spring but nearly zero change in fall. The solar cycle related amplitude is about 1.4% per 100 units of 10.7 cm solar flux. The ozone trends are negative: not significant over the equator and about –2% per decade (significant at 95% level) over the tropics. The latter could have been enforced by the 2 to 4% lower ozone values during 1991–1993, part of which might be related to the effects of the Mt. Pinatubo eruption, but might also be due to the strong QBO. The estimated deviations are verified versus reliable observations and the very good agreement permits applying the model for quantitative quality control of the reported ozone data from previous years. The standard deviation of the difference between observed ozone deviations and those estimated from the model is only 0.9–1.6% for yearly mean, that means instruments used for total ozone observations in the tropical belt should have systematic error of less than 1%. Cases when the discrepancies between the model and reported observations at a given station exceed 2–3% for time interval of 2 or more years should be verified.With 17 Figures     

Use of precipitation data for diabatic initialization to improve the tropical analysis of divergence and moisture

Summary First, we review the present status of diabatic initialization used for numerical weather prediction and conclude that the deficiency of diabatic initialization mostly stems from the shortcoming in evaluating diabatic heating rates accurately, particularly the release of latent heat by cumulus convection. This indicates the need to adjust the initial conditions for physical processes, and Krishnamurti and his colleagues introduced in 1984 the concept of physical initialization. Since cumulus convection is most sensitive to input data among many physical processes, the adjustment of atmospheric input data to a prediction model to produce desired initial precipitation rates is referred to as cumulus initialization.In this article we describe a general approach to diabatic initialization with a special emphasis on cumulus initialization. We present the results of forecasting experiments with a version of the NCAR Community Climate Model (CCM) to demonstrate the efficacy of a cumulus initialization procedure to ameliorate the spinup problern of precipitation. Finally, we discuss application of the present methodology of cumulus initialization for a stability-dependent mass-flux cumulus parameterization of CCM2 to pave the way to complete the diabatic normal mode initialization package for CCM2. Note that the present cumulus initialization scheme can be used to assimilate into the atmospheric analysis of the tropics the precipitation rates estimated by satellite radiometric imagery data.With 8 FiguresThe National Center for Atmospheric Research is sponsored by the National Science Foundation     

Effects of water on strength and failure mode of coarse-grained granites at 300°C

Summary Deformation experiments have been performed in a triaxial compression cell at a temperature of 300°C and confining pressures up to 65 MPa using samples of homogeneous, fresh two-mica-granite (RM) and monzogranite (CM). The cylindrical specimens (d=70 mm, h=140 mm, V=540 cm³) were tested undrained under dry (105°C), as received, and water saturated conditions at deformation rates between and . The mechanical behaviour of the two types of coarse-grained, crystalloblastic granites is critically influenced by mineralogical composition, porosity, and the amount of intergranular water present in the samples. The failure stress of the CM granite is at about 65% of that of the RM granite; in both rocks strength decreases with increasing porosity and water content.The presence of interstitial water causes a failure mode of non-localized, homogeneously distributed microcracking in the central parts of the samples, whereas, in runs with dry granites, strain localization along a single shear fracture was observed. When aqueous fluids are present, the macroscopic style of deformation of granites appears to be ductile even at lowP andT conditions. Strength and angle of internal friction are reduced to very low values. The style of deformation, as well as the reduction of strength of the water-saturated rock samples, is due to mechanical and chemical effects of intergranular water at elevated temperatures.The maximum differential stresses measured for these coarse-grained granites are much lower than the strength commonly reported for other granites, e. g. Westerly and Charcoal granites. Our data suggest that the strength of the granitic crust under differential stress is lower than currently deduced from laboratory experiments.     

Geochemistry and origin of the Proterozoic ultrapotassic rocks of the Churchill Province,Canada

Summary Early Proterozoic ultrapotassic dikes, lava flows, and pyroclastic rocks of the Christopher Island Formation (CIF) erupted throughout an area 600 × 300 km within the Churchill Province of the Canadian Shield at 1.84 Ga. The rocks range from mafic lamprophyres (mg # 60; SiO₂ 47–54%, mean K₂O/Na₂O > 4) with phenocrysts of phlogopite + diopside + apatite ± olivine ± magnetite, to phenocryst-poor felsic rocks and sanidine porphyries (SiO₂55–69%). All samples have high incompatible element contents and display large depletions of high field strength elements relative to K, Rb, Sr, Ba, and Th. The CIF has geochemical and petrographic characteristics of both minettes and lamproites, but overall most closely resembles young Mediterranean lamproites. Felsic rocks of the CIF were produced by crystal fractionation and crustal contamination of mafic ultrapotassic magma, and include both high-silica lamproites strongly enriched in Zr, U, and Th, and weakly potassic to sodic rocks of trachytic composition. Flows and feeder dikes have relatively homogeneous _{Nd, 1840 Ma} (–6 to –11) but highly variable ES., 1840 Ma (–40 to + 100); samples classified as lamproites have higher average _Sr. Dike samples have highly variable present-day Pb isotope compositions, ranging from moderately to strongly nonradiogenic. Geochemical and isotopic data are consistent with contributions from depleted Archean lithospheric mantle, and OIB-type convecting mantle, both metasomatized by subduction-related processes during the Early Proterozoic. The lithospheric mantle probably contained Archean enriched domains as well. Proterozoic enrichment may have accompanied shallow underplating of subducted oceanic lithosphere beneath the Churchill Province during amalgamation of the Laurentian supercontinent. There are strong analogies in isotopic composition, and interpreted source region history, between the CIF and lamproites and minettes of the Wyoming Province and western Greenland, which suggest the existence of a Laurentian ultrapotassic superprovince.

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Geochemie und Entstehung der Proterozoischen ultrapotassischen Gesteine der Churchill Provinz, Kanada

Zusammenfassung Altproterozoische, ultrapotassische Gänge, Lavaströme und pyroklastische Gesteine der Christopher Island Formation (CIF), eruptierten in einem Gebiet von 600 × 300 km in der Churchill Provinz des Kanadischen Schildes vor 1.84 Ga. Die Zusammensetzung dieser Gesteine variiert von mafischen Lamprophyren (mg > 60; SiO₂ = 47–54%, durchschnittliches K₂O/Na₂O > 4) mit Phänokristallent von Phlogopit + Diopsid + Apatit + Olivin + Magnetit, bis zu phänokristallarmen felsischen Gesteinen und Sanidinporphyren (SiO₂ = 55–69%). Alle Proben zeigen hohe Gehalte an inkompatiblen Elementen und zeigen beträchtliche Verarmung an high field strength Elementen relativ zu K, Rb, Sr, Ba und Th. Die CIF hat geochemische und petrographische Eigenschaften sowohl von Minetten wie von Lamproiten, aber im allgemeinen ähnelt sie am stärksten jungen mediterranen Lamproiten. Felsische Gesteine der CIF wurden durch Fraktionierung und Krustenkontamination aus mafischen ultrapotassischen Magmen gebildet. Letztere umfassen sowohl siliziumreiche Lamproite, die deutlich an Zr, U und Th angereichert sind und schwach potassische bis sodische Gesteine von trachytischer Zusammensetzung. Lavenergüsse und zufuhrgänge zeigent ein relativ homogenes _{Nd, 1840 Ma} (–6 bis –11) aber ein sehr variables _{Sr, 1840 Ma} (-40 bis + 100); Proben die als Lamproite klassifiziert wurden, zeigent höhere durchschnittliche _Sr-Werte. Proben von Gängen haben sehr variable Bleiisotopen-Zusammensetzungen, die von mäßig bis stark nichtradiogen variieren. Geochemische und Isotopendaten weisen auf Beiträge aus verarmtem archaischen lithosphärischen Mantel und aus konvektierendem OIB-Typ Mantel hin, die beide während des Alproterozoikums durch Subduktions-Vorgänge metasomatisiert wurden. Der lithosphärische Mantel enthielt wahrscheinlich auch angereicherte archaische Domänen. Proterozoische Anreicherungsvorgänge dürften seichtes Underplating subduzierter ozeanischer Lithosphäre unter der Churchill Provinz während der Amalgamation des laurentischen Superkontinentes begleitet haben. Es gibt starke Analogien in der Isotopenzusammensetzung und in der interpretierten Geschichte der Ursprungsregion, zwischen den CIF und Lamproiten und Minetten der Wyoming Provinz, und des westlichen Grönland. Diese weisen auf die Existenz einer laurentischen ultrapotassischen Superprovinz hin.

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With 7 Figures     

Synthetic zeolites formed from expanded perlite: Type,formation conditions and properties

Summary The starting material used was expanded perlite with a grain size < 40 m (74.5 wt.% SiO₂; 12.5 wt.% Al₂O₃). This material is a waste product obtained during the production of expanded perlite. The experiments were carried out with KOH solutions, mixtures of KOH and NaOH solutions (1:1) as well as NaOH solutions in the concentration range 0.5 N to 6.0 N at temperatures of between 100° and 140°C and with reaction periods of 2 hours to 13 days in closed system. In the experiments with KOH containing solutions zeolite ZK-19 (phillipsite), W (merlinoite), G (chabazite) and F (edingtonite) formed. Without addition of aluminium high percentages of zeolite ZK-19 (80–100 wt.%) and zeolite W (90–100 wt.%) were obtained. The addition of aluminium rendered possibly the formation of 90 to 100 wt.% of zeolite G and 85 to 100 wt.% of zeolite F, respectively. In the experiments with NaOH solutions analcime, zeolite Na-Pc (gismondine), zeolite HS (sodalite hydrate) and zeolite A formed. High percentages of zeolite Na-Pc (90–100 wt.%), zeolite HS (up to 100 wt.%) and analcime (up to 100 wt.%) were synthesized without addition of aluminium. The formation of high percentages of zeolite A (95–100 wt.%), however, needs the addition of aluminium, NaCI and seed crystals. The temperature stability of the zeolites decreases in the following sequence: K-F > K-W K-ZK-19 (Na), K-W Na, K-F G_si-rich (Na), K-ZK-19 >> Na-Pc G_si-poor. Zeolite A has a very good temperature stability up to temperatures of } 550 °C similar to that of zeolite K-W. At higher temperatures, however, its stability is very poor. The NH₄ ⁺-exchange capacities (meq/g) of the different zeolites amount to the following values: ZK-19:2.8 - 3.2; W:3.0 - 3.2; G:2.3 - 3.6; A:3.1 - 3.2; Na-Pc:3.5 - 3.6; F : 3.9 - 4.8.

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Zeolithsynthese aus Blähperlit—Art, Bildungsbedingungen und Eigenschaften

Zusammenfassung Ausgangsmaterial der experimentellen Untersuchungen war Blähperlit mit einer Korngröße < 40 ,m (74,5 Gew.-% SiO₂; 12,5 Gew.-% Al₂O₃). Dieses Material ist ein Abfallprodukt, das bei der Produktion von Blähperlit anfällt. Die Experimente wurden mit KOH-Lösungen, Lösungsgemischen aus KOH und NaOH (1:1) sowie mit NaOH-Losungen im Konzentrationsbereich 0,5 n-6,0 n bei Temperaturen von 100° – 140°C und über Reaktionszeiten von 2 Stunden bis zu 13 Tagen im geschlossenen System durchgeführt. In den Experimenten mit KOH-hältigen Lösungen bildeten sich die Zeolithe ZK-19 (Phillipsit), W (Merlinoit), G (Chabasit) und F (Edingtonit). Hohe Prozentgehalte an Zeolith ZK-19 (80 – 100 Gew.-%) und Zeolith W (90–100 Gew.-%) entstehen nur ohne Zugabe von Aluminium. Die Bildung von 90–100 Gew.-% Zeolith G bzw. 85–100 Gew. % Zeolith F ist dagegen durch die Zugabe von Aluminium möglich. In den Experimenten mit NaOH-Lösungen bildeten sich die Zeolithe Analcim, Na-Pc (Gismondin), HS (Sodalithhydrat) und Zeolith A. Hohe Prozentanteile an Zeolith Na-Pc (90–100 Gew.-%), HS (bis zu 100 Gew. %) und Analcim (bis zu 100 Gew.-%) wurden ohne Aluminium-Zugabe synthetisiert. Die Bildung von hohen Gehalten an Zeolith A (95–100 Gew. %) ist jedoch nur unter Zugabe von Aluminium, NaCl und Kristallkeimen möglich.Die Temperaturbeständigkeit der Zeolithe nimmt in der folgenden Reihenfolge ab: K-F > K-W - K-ZK-19 (Na), K-W Na, K-F G_si-reich (Na), K-ZK-19 >> Na-Pc G_si-am. Zeolith A weist bis zu Temperaturen von etwa 550°C eine gute Temperaturbeständigkeit auf, die in etwa der von Zeolith K-W entspricht. Bei höheren Temperaturen ist die Beständigkeit jedoch sehr gering.Die NH⁴⁺-Austauschkapazitäten (mÄqu/g) der verschiedenen Zeolithe erreichen folgende Werte: ZK-19:2,8 - 3,2; W:3,0 - 3,2; G:2,3 - 3,6; A:3,1 - 3,2; Na-Pc:3,5 -3,6; F:3,9 - 4,8.

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With 2 Figures     

Corona textures in Proterozoic olivine melanorites of the Equeefa Suite,Natal Metamorphic Province,South Africa

Summary Olivine-plagioclase and phlogopite-plagioclase coronas have been identified from olivine melanorites of the Mid- to Late Proterozoic Equeefa Suite in southern Natal, South Africa. Olivine, in contact with plagioclase, is mantled by a shell of clear orthopyroxene, in turn rimmed by pale green (pargasitic) clinoamphibole. Locally a third rim, composed of a fine pargasite-spinel symplectite is developed adjacent to the plagioclase. The second corona reaction has produced greenish-brown pargasite at phlogopite-plagioclase interfaces. A third, less obvious reaction, between olivine and phlogopite is also noted. Analytical data of all the mineral phases present, along with the coronas, are given. Two-pyroxene thermometry yields magmatic core temperatures ( 1120°C), with rim compositions indicating equilibration at 850°C. Consistent with this, the modelled olivine-plagioclase reaction occurs between 830–1050°C with a_waterbetween 0.1 and 1.0 at 7 kbar. The three reactions took place during a prolonged history of cooling and partial hydration of the magmatic olivine melanorites from over 1000°C down to 600°C. The P-T conditions indicated by the reactions suggest this cooling process was essentially isobaric, indicating that the area was not subjected to rapid uplift or burial throughout this entire period.

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Korona-Texturen in proterozoischen Olivin-Melanoriten der Equeefa Suite, Natal Metamorphic Province, Südafrika

Zusammenfassung Aus Olivin-Melanoriten der mittel- bis spätproterozoischen Equeefa Suite im südlichen Natal, Südafrika, wurden Olivin-Plagioklas und Phlogopit-Plagioklas-Koronartexturen beobachtet. Olivin, der mit Plagioklas im Kontakt steht, wird von einem klaren Saum vom Orthopyroxen ummantelt, der seinerseits von blaßgrünem (pargasitischem) Klinoamphibol umsäumt wird. Stellenweise ist ein dritter Saum, bestehend aus feinkörnigem symplektitischem Pargasit-Spinell im Kontakt mit Plagioklas ausgebildet. Die zweite koronabildende Reaktion resultiert in Bildung eines grünbraunen Pargasites an Phlogopit-Plagioklas Kornkontakten. Eine dritte, weniger auffällige Reaktion zwischen Olivin und Phlogopit wurde ebenfalls beobachtet. Zwei-Pyroxen-Thermometrie ergab magmatische Temperaturen der Kernbereiche ( 1120°C) und belegt eine Gleichgewichtseinstellung in den Randzonen bei ca. 850°C. Olivin-Plagioklas-Modellreaktionen liegen ebenfalls in einem Temperaturbereich von 830–1050°C bei Wasseraktivitäten von 0.1 bis 1.0 und einem Druck von 7 kbar. Die drei Reaktionen liefen im Zuge einer länger andauernden Abkühlung unter teilweiser Hydratisierung der magmatischen Melanorite in einem Temperaturbereich von 1000°C bis ca. 600°C ab. Die aus den Reaktionen ableitbaren P-T-Bedingungen sprechen für eine im wesentlichen isobare Abkhlungsgeschichte und zeigen, daß dieses Gebiet wáhrend dieser gesamten Periode keiner raschen Hebung bzw. keiner Versenkung unterworfen worden ist.

     

Crystal chemistry of a highly disordered Mg-Al natural spinel

Summary A Mg-Al spinel from a xenolith found in the Sacrofano volcanic area (Latium, Italy) was investigated by X-ray single crystal diffraction and electron microprobe. Its main structural parameters were: a₀ = 8.0922(3) Å and the oxygen coordinate u = 0.26213(4), which gave to tetrahedral and octahedral bond distances of 1.9220(6) Å and 1.9299(3) Å respectively. Cation distribution, obtained from structural and chemical data, showed a very high Mg-Al disorder, with an Al(T) content of 0.205 and an inversion parameter, i, of about 0.23. Comparison with the cation distribution of a spinel with similar chemical composition but occurring in chlorite schists (Shishimsk Mountains, Urals, Russia) with a₀ = 8.1003(3) Å and u=0.26330(3), and with data from the literature concerning spinels from metamorphosed limestones (Kalkbro, Sweden) and websteritic dikes (Balmuccia, Italy), all characterized by much lower Mg-Al disorder (i about 0.13–0.12), suggests a completely different thermal history, with rapid cooling rates and consequent high closure temperature of intracrystalline exchange, consistent with the Sacrofano geological environment.

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Kristallchemie eines stark ungeordneten, natürlichen Mg-Al-Spinells

Zusammenfassung Ein Mg-Al-Spinell aus einem Xenolith des Vulkangebiets von Sacrifano (Latium, Italien) wurde mit Röngten-Einkristallmethoden und der Elektronenmikrosonde untersucht. Die wichtigsten Strukturparameter sind a_o = 8,0922(3) Å und die Sauerstoffkoordinate u = 0,26213(4), was zu den tetraedrischen und oktaedrischen Bindungsabständen von 1,9220(6) Å bzw. 1,9299(3) Å führt. Die aus den strukturellen und chemischen Daten erhaltene Kationenverteilung zeigt eine sehr starke Unordnung Mg-Al mit einem Al (T)-Gehalt von 0,205 und einem Inversionsparameteri von ca. 0,23. Der Vergleich mit der Kationenverteilung eines Spinells ähnlicher chemischer Zusammensetzung, aber aus Chloritschiefern (Schischimsk-Berge, Ural, Rußland) mit a₀ = 8,1003(3) Å und u=0,26330(3), sowie mit Literaturdaten über Spinelle aus metamorphen Kalken (Kalkbro, Schweden) und websteritischen Gängen (Balmuccia, Italien), die alle durch eine viel geringere Mg-Al-Unordnung charakterisiert sind (i etwa 0,13–0,12), weist auf eine völlig andere thermische Geschichte hin, und zwar mit rascher Abkühlungsgeschwindigkeit und hoher Schließungstemperatur des intrakristallinen Austausches, was mit den geologischen Verhältnissen von Sacrofino in Übereinstimmung steht.

     

Geology of the volcanic-hosted Brockman rare-metals deposit,Halls Creek Mobile Zone,northwest Australia. l. Volcanic environment,geochronology and petrography of the Brockman volcanics

Summary Rare-metals mineralization of the Brockman deposit (Halls Creek Mobile Zone, NW Australia) is hosted in a fluorite-bearing, rhyolitic volcaniclastic unit informally termed the Niobium Tuff. The Tuff, more correctly described as a tuffaceous volcaniclastic deposit, is the lowermost unit of a sequence of trachyte-to-rhyolite lavas, trachyandesite subvolcanic rocks, and volcaniclastic units of the Brockman volcanics located within the Halls Creek Group, a thick, early Proterozoic volcano-sedimentary sequence. High precision SHRIMP ion-microprobe zircon dating of the Niobium Tuff gives an eruption age of 1870 ± 4 Ma. Regional geochronological constraints indicate the Niobium Tuff was deposited about 15 Ma before major orogenic activity affected the area. Despite folding, faulting and low-grade metamorphism, the Brockman volcanics show excellent preservation of primary volcanological features, including pillow-lavas and pillow-breccias, that suggest a dominantly subaqueous, below-wave-base emplacement environment. The style of eruption products and magma volume constraints suggest the trachyte-dominated volcanics were erupted from a small shield volcanic complex probably in a rift-related basin in a shallow-marine setting. The tectonic setting was intraplate but differs from most Tertiary to recent trachyte volcanic complexes which are largely subaerial, are built on relatively thick continental crust, and show no post-eruptive orogenic history. Brockman-style rare-metal deposits are characterized by preservation of subaqueous volcanics beneath a thick sedimentary sequence, eruption of early incompatible-element enriched products followed by less differentiated magmas, and fine-grained mineralogy influenced by alteration processes. Prospects exist for discovery of analogous deposits, particularly in early Proterozoic mobile belts and Tertiary intraplate shield volcanic provinces.

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Geologie der an Vulkanite gebundenen Seltene-Metalle-Lagerstätte Brockman, Halls Creek Mobile Zone, Nordwest-Australien. I. Vulkanologie, Geochronologie und Petrographie der Brockman-Vulkanite

Zusammenfassung Selten-Metall-Vererzung der Brockman-Lagerstätten (Halls Creek Mobile Zone, NW Australien) sitzt in einer Fluorit-führenden, rhyolitischen vulkanoklastischen Einheit auf, die informell als der Niob-Tuff bezeichnet wird. Es handelt sich hier um ein vulkanoklastisches Tuff-Sediment; dieses ist die unterste Einheit einer Abfolge vor Trachyt bis Rhyolit-Laven, trachyandesitischen Subvulkaniten and vulkanoklastischen Einheiten der Brockman Vulkanite innerhalb der Halls Creek Gruppe, einer mächtigen frühproterozoischen vulkanosedimentdren Abfolge. Prüzisionsdatierungen des Niob Tuffs mit der SHRIMP Ionen-Mikrosonde ergeben ein Eruptionsalter von 1870 +-4 Millionen Jahren. Regionale geochronologische Zusammenhänge zeigen, daß der Niob Tuff etwa 15 Millionen Jahre vor einer größeren Orogenese, die das Gebiet betroffen hat, abgelagert wurde. Trotz Faltung, Bruchtektonik and niedriggradiger Metamorphose zeigen die Brockman-Vulkanite einen hervorragenden Erhaltungszustand primärer vulkanologischer Erscheinungen. Diese urnfassen auch Kissenlaven und KissenBreckzien, die eine vorwiegend subaquatische Ablagerung in ruhigem Wasser erkennen lassen. Die Art der Eruptionsprodukte and das Magmavolumen zeigen, daß die Trachytdominierten Vulkanite von einem kleinen Schildvulkan stammer, wahrscheinlich in einem Becken in einer Rift-Situation im seichten marinen Milieu. Die tektonische Situation war intraplate, aber unterscheidet sich von den meisten tertiären bis rezenten trachytischen Vulkan-Komplexen, die hauptsächlich subaerisch sind, auf einer relativ mächtigen kontinentalen Kruste aufsitzen, and keine post-eruptive orogene Entwicklung zeigen. Seltene-Metalle-Lagerstatten des Brockman-Typs rind durch die Erhaltung subaquatischer-Vulkanite unterhalb einer machtigen sedimentdren Abfolge gekennzeichnet; welters durch frühe Eruptionsprodukte, die an inkompatiblen Elementen angereichert sind, auf die dann weniger differenzierte Magmen folgten, und schließlich durch einen feinkörnigen Mineralbestand, der vor Umwandlungsprozessen betroffen war. Es besteht die Möglichkeit der Entdeckung analoger Lagerstätten, besonders in frühproterozoischen mobilen Gürteln und in tertidren intraplate Schildvulkan Provinzen.

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Deceased