The crystallization of pyroxenes and amphiboles in some alkaline rocks and the presence of a pyroxene compositional gap

Ca- and Na-rich pyroxene-amphibole compositions and textures from a range of felsic alkaline rocks have been studied in detail. The data indicate that in a single sample, when amphibole crystallizes, a gap is observed between Ca- and Na-rich pyroxene compositions. This break in composition is analogous to Aoki's (1964) immiscibility gap between Ca-and Na-rich pyroxenes and can be overlooked when considering pyroxene compositions from a suite of rocks. The role of volatiles in governing the stability and composition of amphiboles is discussed. The presence of late crystallizing Na-rich pyroxene is related to the development of peralkinity in the late-stage melts.On extrusion, many alkaline rocks lose their volatiles and amphibole is absent. In these rocks complete zoning from Ca-rich to Na-rich pyroxene compositions are observed within the one sample.     

Geological, mineralogical and geochemical characteristics of zeolite deposits associated with borates in the Bigadiç, Emet and Kirka Neogene lacustrine basins, western Turkey

The Bigadiç, Emet and Kirka lacustrine basins of western Turkey may be considered as Tibet-type graben structures that were developed during the Miocene within the Izmir-Ankara suture zone complex. The volcanic-sedimentary successions of these basins are made up of mudstone, carbonate (limestone and dolomite) and detrital rocks, and also of crystal or vitric tuffs about 135 to 200 m thick. The Degirmenli (Bigadiç), Emirler (Bigadiç) Köpenez (Emet) and Karaören (Kirka) tuffs constituting the zeolite deposits are situated beneath four borate deposits (colemanite, ulexite, borax). The most abundant diagenetic silicate minerals are K- and Ca-clinoptilolites in the zeolite deposits, and Li-rich trioctahedral smectites (stevensite, saponite and hectorite) and K-feldspar in the borate deposits. In the Degirmenli, Emirler. Köpenez and Karaören deposits, the following diagenetic faciès were developed from rhyolitic glasses rich in K and poor in Na: (glass + smectite), (K-clinoptilolite + opal-CT), (Caclinoptilolite + K-feldspar ± analcime ± quartz) and (K-feldspar+analcime+quartz). K-feldspar which is also rarely associated with phillipsite (Karaören) and heulandite (Degirmenli and Karaören), succeeds clinoptilolite and precedes analcime in these diagenetic facies where dioctahedral smectites, opal-CT and quartz are the latest minerals. No diagenetic transformations exist between clinoptilolite, K-feldspar and analcime that were formed directly from glass. The lateral facies distributions resulted from the differences in salinity and pH of pore water trapped during deposition of the tuffs, but vertical distributions in vitric tuffs seem to have been controlled by the glass/liquid ratio of the reacting system and the permeability or diffusion rate of alkali elements. The Bigadiç, Emet and Kirka zeolite deposits which were formed in saline basins rich in Ca and Mg ions, show similar chemical changes, i.e. loss of alkalis and gain in alkaline-earth elements that have taken place during the diagenetic transformation of rhyolitic glasses to dioctahedral smectites or clinoptilolite. The absence of sodic zeolites such as mordenite, erionite, chabazite and silica-rich phillipsite is mainly due to the very high K/Na ratio of the starting materials rather than initial alkaline conditions or high Na content in lake waters.     

Composition and origin of North Atlantic deep sea cherts

Rocks described as chert from the North Atlantic, recovered during the Deep Sea Drilling Project, consist of quartz or disordered cristobalite. They occur in a wide variety of sediment types; only a few are associated with radiolarian oozes. Some of the cristobalitic cherts contain abundant clinoptilolite or palygorskite and sepiolite.The cherts have a variety of origins. They are most probably replacement cherts at sites 5, 6, and 7; direct alteration products of radiolarian ooze at site 8; and either alteration products of volanic glass or direct precipitates from hydrothermal solutions at sites 9 and 12. Evidence for these diverse origins is preserved as unusual mineral assemblages in these geologically young rocks.     

Spatial variations in the geochemistry of quaternary lavas across the Sunda arc in Java and Bali

Since Mesozoic time, Java and Bali have formed part of an evolving system of island arcs comprising the Sunda arc of Indonesia. The present tectonic setting is relatively simple with subduction occurring at the Java Trench to the south. A north-dipping Benioff seismic zone delineates an underthrust lithospheric slab to depths of approximately 600 km beneath the Java Sea. Quaternary lavas of the normal island arc association range from tholeiites to high-K calc-alkaline lavas over Benioff zone depths from 120–250 km, respectively. More abundant calc-alkaline lavas lie between these extremes. High-K alkaline lavas are found over Benioff zone depths in excess of 300 km.Both within and between these groups of rocks there are consistent spatial variations in the observed geochemistry. For approximately 200 rocks, incompatible elements such as K, Rb, Cs, Sr, Ba, light REE, U and Th show an increase in abundance of almost an order of magnitude with increasing depth to the seismic zone. Abundances of compatible elements show little consistent variation and trace elements such as Ni, Co, Cr, and Sc are characteristically depleted except in some of the alkaline lavas. Major element abundances in rocks of the normal island arc association show little variation, except for K and P, which both increase in abundance across the arc and Al, which shows a relative decrease.The major and trace element data are inconsistent with the derivation of the analyzed rocks by partial melting of the crustal component of the subducted lithosphere. On the other hand, low Ni abundances (20 ppm) in the basalts suggest that most of the lavas are fractionated and few if any represent primary mantle-derived melts. The spatial variations in the geochemistry of erupted lavas across Java and Bali are best explained by a combination of two processes: melting of a geochemically zoned mantle source and smaller degrees of partial melting of that material at progressively greater depths. Primary tholeiitic magmas could be formed by 20–25% melting at depths of 30–40 km, primary high-K calc-alkaline magmas by 5–15% melting at 40–60 km depth, and primary alkaline magmas by 5% melting at depths of 80–90 km. The geochemical zoning in the mantle, which is also manifested by increasing ⁸⁷Sr/⁸⁶Sr ratios in lavas across the arc, is interpreted to result from the addition of a small melt fraction derived from the crustal component of the subducted lithosphere.     

On the occurrence of analcime in the northeastern Azerbaijan volcanics (northwestern Iran)

Euhedral, phenocryst-like crystals of analcime, as well as microlites, are rather common in phonolitic and tephritic lavas and in some anaicitic dikes and lenses of the Upper Cretaceous and Lower Tertiary volcanics of eastern Azerbaijan (Iran). The mineralogy and petrology of these extrusive rocks are described with the aim of establishing the origin of the big analcime crystals. While the mineralogical data (e.g. true symmetry, Al/Si disorder and Na atom distribution, structural refinements) are not conclusive, the paragenesis and microprobe analyses of analcime and associated phases, mainly feldspars, lead us to believe they are of a secondary, metasomatic origin. It is suggested that during late or post-magmatic stages analcime may have originated either from ion-exchanged leucite or by alteration or interaction between pre-existing Na-rich phases such as nepheline, feldspars and glass at subsolidus temperatures.     

Two-brine model of the genesis of strata-bound Zechstein deposits (Kupferschiefer type), Poland

These Kupferschiefer deposits were probably formed as a result of a mixing of two brines. The upper cold brine (UCB) is an unmineralized brine rich in Na, Ca, Cl and SO₄, with a pH>7 and originating from evaporites overlying the metal-bearing Zechstein rocks. The lower hot brine (LHB) rich in Mg, K, Cl, SO₄ and CO₃ with a pH<=7 formed in sediments in the central part of the Zechstein basin at a depth of 7,000 m. This brine was subjected to heating and upward convection toward the Fore-Sudetic monocline along the bottom of the Z₁ carbonates. During its migration, it caused albitization, serpentinization and leaching of the primary metal deposits in rocks underlying the Zechstein becoming enriched in heavy metals. The mineralization process, being a result of the mixing of the two brines (UCB and LHB), and catalytic oxidation of the organic matter of the black shale were initiated at shallow depths in the area of the Fore-Sudetic monocline. The boundary of the two brines generally overlapped the strike of the black shale.Parts of the deposit with shale-free host rock suggest that the action of two brines alone was capable of producing economic concentrations of Cu, Pb and Zn. Where the boundary of the two brines overlaps the autooxidation zone (the black shale bottom) and also coincides with radiation of thucholite, concentrations of noble metals result.The characteristic vertical distribution of the triplet CuPbZn from the bottom upward is universal in the Kupferschiefer environment.     

Probable Endogenic Origin of Conglomerate-type Rocks on the Southeastern Coast of the White Sea

The southeastern coast of the White Sea and Kii Island incorporates outcrops of conglomerate-type rocks similar to boulder dikes filling tensile fractures in the early Precambrian basement of the platform. They are related to the southwestern flank of the Onega Graben representing the southeastern segment of the Onega–Kandalaksha paleorift. Genesis of these conglomerate-type rocks, previously considered sedimentary ones, is problematic. Special study of the cement of these rocks revealed that it has probably an endogenic nature. It is dominated by carbonate material replacing ultramafic volcanic glass. Carbonatization and analcime mineralization took place at the regressive stage of cement formation within a temperature range of 450–550°C with active release of H₂O- and CO₂-saturated fluids. Data on the isotopic composition (¹³C and ¹⁸O) for carbonate material of cement from the brecciated rocks testify that the carbonatization was related to input of deep-seated carbon dioxide under subsurface environment. The studies carried out allow us to suppose that these rocks were formed as a result of consolidation of solid–gaseous suspensions inside fractures in the crystalline basement. Penetration of fluidized material along them produced dike-shaped bodies. Such rocks are recently called fluidizates. The sources of solid–gaseous suspension fluxes were basic magmas with a high content of volatiles. Discharge of gases from the magmas was caused by their decompression due to the appearance of tensile zones in lithosphere during rifting.     

Elemental and isotopic abundances of lithium in chondrule constituents in the Allende meteorite

Elemental and isotopic abundances of lithium in chondrule constituents in the Allende CV3 meteorite were determined using secondary ion mass spectrometry. Olivines and mesostasis dominated by a feldspathic phase are depleted in Li ( and , respectively). In contrast, low-Ca pyroxenes and mesostasis dominated by a Na-rich phase are enriched in Li ( and , respectively) and the interchondrule matrix is generally enriched in Li ( on average). The Li isotopic abundance of olivine ranges from to 21. The spatial distributions of elemental and isotopic abundances of Li in olivines within individual chondrules exhibit no systematic pattern. This suggests that the distribution of Li in olivine was not disturbed during aqueous alteration or thermal metamorphism on the Allende meteorite parent body. Although mesostasis is the last crystallizing phase from a chondrule melt and is expected to be enriched in Li, in the Allende meteorite it is generally depleted in Li. We suggest that during aqueous alteration on the CV asteroid, Li in mesostasis was leached out by aqueous fluids. The Li-enriched Na-rich mesostasis was probably produced later by infiltration of Na-rich fluids. It seems likely that aqueous fluids sequestered alkali elements from the Allende-chondrite region in the CV parent asteroid, although significant amounts of Li are preserved in ferrous olivine in the interchondrule matrix.     

Human sociogeophysics — Phase I: Explaining the macroscopic patterns of man on earth

The demography of man on earth is treated by a physical model for that forward transport for the subspecies in time. By examining the distribution of man and his Neanderthaler precursor, it is inferred, as a likely hypothesis, that the initial Phase I expansion of man on earth (40,000–15,000 ybp) was at a constant density of about 0.04 persons per sq.km with little or no remixing. We suggest that the nature of the physical process was a diffusion, a random walk process with a diffusive velocity of one roaming range (30 km) per generation, i.e., 1.5 km per year. The physics and physiology of the breeding process permits us to estimate the total earth population, the birth rate b, the death rate d, and the net difference (that is the Malthusian constant K, dP/dt = KP, where K = b-d, P = population, and dP/dt is the rate of change in population).     

The character of the fine fractions of the bottom sediments of the Bohemian part of the Labe (Elbe) river

The amounts of fractions with size 63 m in the bottom sediments of the Bohemian part of the Labe (Elbe) river is variable. The grain-size distribution is poorly to very poorly sorted with a mean particle size from 5.1 to 12.2 m.The crystalline phase of recent sediments of the Labe river draining various types of parent rocks has a simple mineral composition, with predominant mica/illite, quartz, kaolinite and chlorite (±vermiculite ±smectite). There are also very small amounts of interstratification of 10 Å and 14 Å sheet silicates (11–13.6 Å). Small amounts of Na-rich plagioclase, K-feldspar and calcite have also been found; accessory amounts of amphibole, authigenic gypsum and pyrite are also present. Opal in diatomic tests is an omnipresent constituent. In the amorphic inorganic phase, hydrated oxides predominate, where Si >Al >Fe >Mn in a ratio of 64:28:22:1. The greatest amount of amorphous inorganic and organic phases were found in the 4 m fraction.A considerable part of the detrital material originates from soils formed on various igneous, metamorphic and sedimentary rocks, transported to the Labe by other rivers or directly by erosion in the immediate vicinity of the Labe river.     

Probing fault zone heterogeneity on the Nojima fault: Constraints from zircon fission-track analysis of borehole samples

Fission-track (FT) thermochronologic analysis was performed on zircon separates from rocks in and around the Nojima fault, which was activated during the 1995 Kobe earthquake. Samples were collected from the University Group 500 m (UG-500) borehole and nearby outcrops. FT lengths in zircons from localities > 25 m away from the fault plane as well as one 0.1 m away from the fault in the footwall are characterized by concordant mean values of  10–11 μm and unimodal distributions with negative skewness, which showed no signs of appreciable reduction in FT length. In contrast, those adjacent (< 3 m) to the fault at depths on the hanging wall side showed significantly reduced mean track lengths of  6–8 μm and distributions having a peak around 6–7 μm with rather positive skewness. The former pattern is interpreted to reflect cooling through the zircon partial annealing zone (ZPAZ), without later, partial thermal overprints. The latter indicates substantial track shortening due probably to secondary heating by a thermal event(s) that locally perturbed the geothermal structure. Modeled zircon FT length and age data of partially annealed samples from the UG-500 borehole revealed a cooling episode in the ZPAZ that started at  4 Ma within  3 m from the fault plane, whereas those from the Geological Survey of Japan 750 m borehole record cooling started at  31–38 Ma within  25 m from the fault. On the basis of one-dimensional heat conduction modeling as well as the consistency between the degree of FT annealing and the degree of deformation/alteration of borehole rocks, these cooling ages in both boreholes are interpreted as consequences of ancient thermal overprints by heat transfer or dispersion via fluids in the fault zone. Together with the zircon FT data of a pseudotachylyte layer recently analyzed, it is suggested that the present Nojima fault system was reactivated in the Middle Quaternary from an ancient fault initiated at  56 Ma at mid-crustal depths. Also shown is a temporal/spatial variation in terms of the thermal anomalies recorded in the fault rocks, implying heterogeneity of hot fluid flows in the fault zone.     

Analcimes from some potassic igneous rocks and aspects of analcime-rich igneous assemblages

The mineralogy and chemistry of some analcime-rich igneous rocks — analcimites from the potassic Highwood province, Montana, and an analcime tinguaite from the Dunedin Volcanic Complex, New Zealand — have been investigated to obtain some indication of the KNa substitution in natural analcimes. The analcimes have potash-poor compositions, the K₂O revealed by the rock analyses being represented in the mode mainly by Or-rich feldspar (hyalophane or sanidine). These data and the evidence afforded by other analcime compositions confirm earlier conclusions based on experimental studies (Peters, Luth and Tuttle, 1966), namely that analcime solid solutions may contain up to approximately 2% K₂O. Some aspects of analcime-rich igneous assemblages are also discussed.     

Chemistry of micas and chlorite in Proterozoic acid metavolcanics and associated rocks from the Hästefält area,Norberg ore district,central Sweden

Microprobe analyses are performed on micas (biotite, muscovite and phlogopite) and chlorite from 1.9–1.8 Ga acid K- or Na-rich metavolcanics, cordierit-emica schists and manganiferous rocks from the Hästefält area in central Sweden. The results indicate that Fe-rich biotites and muscovites containing 10 to 25% celadonite and/or pyrophyllite are common in the K- and Na-rich metavolcanics. In the cordierite-mica schists the biotites are Mg-rich and the muscovites contain less than 10% celadonite and/or pyrophyllite. The predominant mica in the manganiferous rocks are phlogopite and less frequent rather pure muscovite. The chlorites show a wide range in composition, but principally those occurring in the K- and Na-rich metavolcanics are brunsvigite and diabantite and those in the cordierite-mica schists and the manganiferous rocks are mainly sheridanite and clinochlore. The chlorites of the manganiferous rocks show enrichment in Mn compared to those in other rock types. In general the compositional variations in the micas and less commonly chlorites are strongly controlled by rock type and fluid chemistry, particularly with respect to the ratio of FeO/(FeO+MgO). Estimates of maximum prograde metamorphic temperature, based on phyllosilicates and co-existing cordierite and garnets, indicate a value of up to 500° C.     

The zeolite deposits of Greece

Zeolites are present in altered pyroclastic rocks at many localities in Greece, and large deposits of potential economic interest are present in three areas: (1) the Evros region of the province of Thrace in the north-eastern part of the Greek mainland; (2) the islands of Kimolos and Poliegos in the western Aegean; and (3) the island of Samos in the eastern Aegean Sea. The deposits in Thrace are of Eocene-Oligocene age and are rich in heulandite and/or clinoptilolite. Those of Kimolos and Poliegos are mainly Quaternary and are rich in mordenite. Those of Samos are Miocene, and are rich in clinoptilolite and/or analcime. The deposits in Thrace are believed to have formed in an open hydrological system by the action of meteoric water, and those of the western Aegean islands in a similar way but under conditions of high heat flow, whereas the deposits in Samos were formed in a saline-alkaline lake.     

Characteristics and chronology of fracture — fluid infiltration in the Archean,Eye Dashwa Lakes pluton,Superior Province: evidence from H,C, O-isotopes and fluid inclusions

The Archean Eye Dashwa Lakes pluton (2672±24 Ma) has domains of mineralogically fresh isotropic granite, domains that have undergone bulk hydrothermal alteration, and at least eleven sets of sequential fracture arrays, each with distinctive mineral assemblages. Fresh granite is characterized by whole rock ¹⁸O=8.1 to 8.6 and primary magmatic quartz-feldspar (+1.3), quartz-biotite (5.2 to 5.4) and quartz-magnetite (+9.8) fractionations. Magmatic fluids had a calculated isotopic composition of ¹⁸O=7.9±0.5, and D=–80±5. These isotropic volumes of the granite have not experienced significant incursion of external thermal waters. Pegmatites, quartz-molybdenite veins, and phlogopite-muscovite coated fractures are sporadically distributed in the granite, and were precipitated from high-temperature magmatic fluids where ¹⁸O=8.0 to 10.3 and D=–80±5.The most abundant variety of fracture filling assemblage is epidote-quartz-chlorite±muscovite: fractures are bounded by domains of mineralogically similar bulk hydrothermal alteration of the granite. These minerals formed at 160 to 280° C, in the presence of NaCl, and NaCl-MgCl₂ brines (up to 25 wt% NaCl equivalent) of probable evolved marine water origin ( ¹⁸O=+0.4 to +3.8, D=–10 to –35) undergoing transient boiling. Upper plateau ⁴⁰Ar/³⁹Ar ages for the muscovite are 2650±15 Ma. Sequentially in the chronology of fracture-infiltration events, calcite-fluorite veins were deposited from boiling fluids at 340 to 390° C, isotopically characterized by ¹⁸O=4.7 and ¹³C=–5; and rare prehnite-chlorite lined fractures formed at 250 to 290° C. A generation of adularia-bearing veins precipitated at 140 to 230° C, from CaCl₂-NaCl brines, where ¹⁸O=0 to –6.5 and D=–10 to –30. Incremental ⁴⁰Ar/³⁹Ar age spectra on the K-feldspar yield an upper plateau of 1100 Ma. Subsequently, hematite developed during reactivation of earlier fractures, at 140 to 210° C in the presence of fluids characterized by ¹⁸O=–0.4 to –5.4 and D=–15 to –25. Arrays of open fractures partially occupied by gypsum and goethite reflect a fluid infiltration event at temperatures <50° C. Many of the earlier generations of fracture minerals have transgranular fracture infillings which record the presence of low temperature (88–190° C), hypersaline CaCl₂-NaCl brines. Narrow fractures lined with clays±calcite are sites for seepage of modern ground-waters. The isotopic signature of clay ( ¹⁸O=12 to 20, D=–80±5) plots near the line for modern kaolinites, confirming its formation in the presence of recent surface waters. Calcites coexisting with the clay minerals, and in fractured pegmatite show a common isotopic signature ( ¹⁸O=23±0.5, ¹³C=–13.6), indicating precipitation from modern groundwaters, where reactivated fractures have acted as conduits for infiltration of surface waters to depths of 200 m. Intermittent fracture-infiltration has occurred over 2.7 Ga. The early sequences of fracture-related fluid flow are interpreted in terms of devolatilization of the granite, followed by thermal contraction fracturing, incursion of marine water and convective cooling in the Archean. Hematite and adularia fracture fillings correspond to a stage when meteoric water infiltrated the volcanicplutonic terrain during Proterozoic and later times. Episodic fracture-fluid expulsion events may have been driven by seismic pumping, in response to magmatically and tectonically induced stresses within the Shield, with surface waters penetrating to depths of 15 km in the crust.     

Melt-vapor solubilities and elemental partitioning in peraluminous granite-pegmatite systems: experimental results with Macusani glass at 200 MPa

Vapor-saturated experiments at 200 MPa with peraluminous, lithophile-element-rich rhyolite obsidian from Macusani, Peru, reveal high miscibility of H₂O and silicate melt components. The H₂O content of melt at saturation (11.5+-0.5 wt.%) is almost twice that predicted by existing melt speciation models. The corresponding solubility of melt components in vapor decreases from 15 wt.% dissolved solids (750°–775° C) to 9 wt.% at 600° C. With regard to major and most minor components, macusanite melt dissolves congruently in vapor. Among the elements studied (B, P, F, Li, Rb, Cs, Be, Sr, Ba, Nb, Zr, Hf, Y, Pb, Th, U, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm), only boron has a vapor/melt partition coefficient (D[B]) consistently 1 at superliquidus temperatures (>645° C). Phosphorus and fluorine behave similarly, with D[P] and D[F]<0.5. Little or no significant vapor/melt fractionation is evident among most periodic groups (alkalis, alkaline earths, Zr/Hf, or the REE). The temperature dependence of vapor/melt partition coefficients is generally greatest for cations with charge +3 (except Nb and U); most vapor/melt partition coefficients for trace elements increase with decreasing temperature to the liquidus. Crystallization proceeds by condensation of crystalline phases from vapor; most coexisting melts are aphyric. Changes in the major element content of melt are dominated by the mineral assemblage crystallized from vapor, which includes subequal proportions of white mica, quartz, albite, and orthoclase. The volumetric proportion of (mica + or-thoclase)/albite increases slightly with decreasing T, creating a sodic, alkaline vapor. Vapor deposition of topaz (T500° C), which consumes F from melt, returns K/Na ratios of melt to near unity with the vapor-deposition of albite. The abundances of most trace elements in residual melt change little with the crystallization of major phases, but in some cases are strongly controlled by the deposition of accessory phases including apatite (T550° C), which depletes the melt in P and REE. Below the liquidus, boron increasingly favors the vapor over melt with decreasing temperatures.     

Leaching behaviour of a simulated nuclear waste glass in groundwater of 50–240°C

A simulated nuclear waste glass, developed by the Power Reactor and Nuclear Fuel Development Corporation of Japan, was leached at 50, 75, 95, 110, 160, 210 and 240°C under saturated vapor pressure in groundwater from a granitic terrain. Depth profiles of insoluble components in reacted glass surface were measured by EPMA, together with time-excursion of the solution composition. Except at 160 and 210°C, B, Na, Mo (as MoO₄²⁻), Li, K, Si and Cs were leached out readily, with increasing rate of leaching in this order, at all other temperatures. At the intermediate temperatures of 160 and 210°C, however, the leaching rates of the soluble components were significantly lowered. Surface layers formed on the reacted glass surface thickened and changed in composition and structure with increasing temperature of reaction. During 312 h leaching at 110°C, a leached layer, about 5 μm thick, formed which is depleted in the soluble components and enriched in immobile metals such as Ni, Mn and Fe, and in precipitated components such as Ca and Mg. At 160 and 210°C, the secondary layer is composed of two sharply defined sublayers: an inner leached layer and an outer KSiAlrich layer, probably formed on the leached layer by precipitation from solution. The 50-μm thick layer formed during 508 h of leaching at 240°C is composed of three broadly defined sublayers, an inner leached layer, an outer precipitation layer and a middle layer of intermediate composition between the former two. The significant suppression in leaching rate at 160 and 210°C is interpreted as a result of rapid formation of the precipitation layer on the glass surface which slowed the diffusive migration of solution species responsible for glass dissolution through the surface layer. At 240°C, the leaching rate of soluble species except for silica increased significantly after an initial stage of slow leaching. At this temperature, coarse crystalline analcime precipitated from solution probably in expense of the surface precipitate, thus preventing the formation of surface precipitation layer as impermeable to solution species migration as that formed at 160 and 210°C.     

Trace metals in suspended particulate matter and in sediment trap material from a permanently anoxic fjord — Framvaren, South Norway

Geochemical studies of the trace metal concentrations in suspended particulate matter (SPM) and sediment trap material from a permanently anoxic fjord, Framvaren, South Norway in 1989 and 1993 indicate that extremely high concentrations of zinc (max = 183920 mg/kg), copper (max = 4130 mg/kg), lead (max = 2752 mg/kg), and cadmium (max= 8.1 mg/kg) sometimes (1993) occur in the SPM collected in the anoxic water layer. The highest concentrations of Zn occur just below the redoxcline at 22 m water depth (in 1993), and copper, lead and cadmium have maximum concentrations between 30 and 80 m depth, where the amount of total SPM is at a minimum (about 0.3 mg/L). On a mass per volume (g/L) basis, the maximum concentrations of Cd, Cu and Fe occur at the interface (21m) and those of Zn occur just below the redoxcline (22 m depth). The SPM and sediment trap data suggest that the metals are precipitated as sulfide minerals in the anoxic water. The presence of particulate sulfides was confirmed by SEM studies that show the occurrence of discrete metal (Cu, Fe, Pb, and Zn) sulfide particles in size from 10–20 m as well as framboidal pyrites (1–5 m in size). Higher levels of metal sulfides at intermediate depths rather than in the deep water of Framvaren (> 100 m), may be due to input of trace metals by water exchange over the sill in the upper part of the water column. In the deep water, less metal sulfide precipitation takes place due to depletion of trace metals, and the dilution of particulate metal concentrations by organic matter and by the chemogenic formation of calcite.     

Compositional and textural evolution of pollucite in pegmatites of the moldanubicum

Summary Pollucite is found in five pegmatites in the Moldanubicum, all of them within the Czech Republic: Susice III (elbaite subtype) and Nová Ves near eský Krumlov (petalite subtype) in southern Bohemia, Jeclov I and Puklice II (lepidolite subtypes) and Vná I (beryl-columbite subtype) in western Moravia. Pollucite displays a broad range of primary compositions at these localities, with CRK = 100(Cs + Rb + K)/ cations variable from 72 to 85, and Si/Al from 2.43 to 2.60. Exsolution to Cs,Al-rich and Na,Si-rich components is not widespread: the maximum CRK is 92 at Si/Al of 2.30. However, Na-exchanged compositions and local veinlets of analcime are much more common; they reach CRK of 5 and 7, respectively. Three occurrences are comparable to the usual pollucite-bearing assemblages, except for the geochemically rather primitive pegmatites at Susice and Vná. At the latter locality, an extremely steep fractionation gradient generates minor amounts of a highly evolved Li-,Cs-,Be-, Ca-,Sr-,Ba-,Mn-,Bi-, REE-,Zr-,Sn-,Th-,W-,B-,P-,F-rich assemblage, with pollucite closely associated with chabazite and harmotome.

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Chemische und strukturelle Entwicklung von Pollucit in Pegmatiten des Moldanubikums

Zusammenfassung Pollucit ist nur in fünf Pegmatiten des Moldanubikums bekannt, die alle auf dem Gebiet der Tschechischen Republik liegen: Suice III (Elbait-Subtyp), Novä Ves in der Nähe von eský Krumlov in Süd-Böhmen (Petalit-Subtyp), Jeclov 1 und Puklice II (Lepidolith-Subtyp) und Vná I (Beryll-Columbit Subtyp) in West-Mähren. Pollucit zeigt ein breites Spektrum an primärer Zusammensetzung mit CRK = 100 (Cs + Rb + K)/ Kationen von 85–72, und Si/Al 2.43 bis 2.60. Entmischung von Cs,Al-reichen und Na,Si-reichen Komponenten ist nicht verbreitet; maximal erreicht CRK = 92 bei Si/Al = 2.30. Weitver-breiteter Na-Austausch in Mineralen und lokale Gängchen von Analcim erreichen CRK von 5 bzw. 7. Alle Vorkommen sind vergleichbar mit den üblichen Pollucit-führenden Vergesellschaftungen ausser dem geochemisch seltenen primitiven Pegmatit von Vná. Ein extrem steiler Fraktionierungsgradient erzeugt hier eine hochentwickelte Li-,Cs-, Be-,Ca-,Sr-,Ba-,Mn-,Bi-,REE-,Zr-,Sn-,Th-,W-,B-,P-,F-reiche Mineralisation mit Pollucit in enger Vergesellschaftung mit Chabasit und Harmotom.

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With 5 Figures