bluuebunny/crossref_metadata_2025 huggingface dataset:
The thermal decomposition of chrysotile
Authors: Martin C. J.
Published: December 2006

The decomposition of chrysotile fibres heated in air has been studied in the range 100–1400°C by electron microscopy and infra-red absorption. The first observable change in the structure occurred at 580°C, where cavities started to open up between the (001) layers of chrysotile as the fibres were dehydrated, giving rise to strong low-angle diffraction. There was no evidence of any structure in the remaining material but some degree of the original atomic arrangement was preserved for the magnesium silicates, forsterite, and enstatite, later developed in certain preferred orientations. The manner of this crystallization was determined by the thermal treatment, for in samples held between 600°C and 800°C forsterite developed slowly with little further disruption of the fibre while above 800°C the remaining amorphous areas rapidly recrystallized to a mixture of forsterite and enstatite. It is suggested that the mechanisms described by other investigators to explain the development of forsterite in preferred orientations may serve simply to nucleate the crystallization and a similar mechanism to account for the nucleation of the enstatite crystallization is considered. At high temperatures a possible doubling of some of the lattice parameters of the silicates was observed.
An electron-diffraction study of a microcrystalline muscovite and its vermiculitized products
Authors: Kodama H.
Published: December 2006

After approximately 50% of K from the 1–2 μm fraction of a naturally occurring microcrystalline muscovite was extracted with BaCl2 solution at 98°C electron-diffraction patterns showed a honeycomb-shaped diffuse scattering as well as intense diffuse streaks. The diffuse scattering became pronounced with increasing K-depletion. It may be interpreted in terms of a short-range order distribution of interlayer Ba ions, using an analogy to the work by Alcover et al. (1972, 1976). Since the diffuse streaks still remained after re-entry of K to the K-depleted specimen they might be related to structural disturbance, particularly in the basal oxygen arrangements, resulting from the K-extraction. Subsequent conversions of Ba-saturated vermiculitized muscovite into Na-, Mg-, and Ca-forms revealed distinct extra diffraction spots midway between two ordinary diffraction spots. They were broader than the ordinary spots and elongated along the three directions of [01]*, [11]*, and [11]*. The diffraction pattern containing the extra spots was, therefore, interpreted as a composite one made up by superimposing three independent patterns, each of which was composed of ordinary Bragg diffraction spots and extra diffraction maxima elongated in one of the three directions. This situation does not require a superlattice but modified the original face-centred lattice symmetry to a primitive lattice symmetry. However, the presence of a real superlattice should also be possible. The elongation and broadness of the extra diffraction maxima may be related to the orientation and size of coherent domains defined by a certain ordering of interlayer cationic distribution, which took place during the hydration processes including extraction and conversion.
Metasomatism in the Wairere Serpentinite, King Country, New Zealand
Authors: Leach T. M. , Rodgers K. A.
Published: December 2006

Metasomatic zones formed at the borders of various mafic inclusions in the Wairere Serpentinite, central North Island, New Zealand, show eucritic and hornblende gabbros grading through distinct zones of altered gabbro (hydrogarnet-free) to coarse and finegrained rodingites (hydrogarnet-bearing). The hydrated, calcium-rich, aluminium-silicate mineral assemblages of each reaction zone change between the zones, with one mineral phase being altered to another at each replacement front. Initial alteration of the gabbros albitized, prehnitized, and epidotized plagioclase and chloritized hornblende and clinopyroxene. Continuing metasomatism garnetized prehnite and generated secondary amphibole and pyroxene while the original host harzburgite was highly serpentinized and, adjacent to the inclusions, the serpentinite was chloritized so as to form a further distinct zone between peridotite and gabbro. These mineral replacement reactions are reflected in the bulk chemistry of the reaction zones, which show that increasing alteration of the gabbro is accompanied by a marked increase in Ca and H2O, a possible small gain in Mg, and depletion in Si, Al, and alkalis. These trends are balanced in the host peridotite by Si enrichment and Ca loss upon serpentinization. Clinopyroxenes and hornblendes of the zones show an increase in Ca and Mg and a decrease in Si with increasing metasomatic alteration. Garnets also decrease in Si but chlorites show an increase in both Si and Mg. Additional minerals analysed from both primary and altered rocks include olivine, orthopyroxene, biotite, plagioclase, pectolite, rosenhahnite, sphene, and chrome spinel. The zones are regarded as the result of reaction between the inclusions and Ca- and Al-rich solutions derived, in turn, by action of alkaline, CO2-poor solutions, which percolated through fractures in the original host peridotite and, in the process of serpentinization, released Mg and enhanced Ca and Al levels. At the contact of the mafic inclusions, chemical gradients were generated down which various chemical species diffused to different levels forming the zonation. The reactions probably took place in the vicinity of 260 to 350 °C, 2 to 3 kb, and at constant volume. Cataclasis and brecciation of the outer zones indicate more than one metasomatic episode.
Hydrous cordierite with isotopically light oxygen from granulites, Strangways Range, Central Australia
Authors: Wilson Allan F.
Published: December 2006

Two new analyses of magnesian cordierites (MgO ∼ 12 %) reveal about 1% by weight of H2O +, and one sample contains 15 × 10−5 cm3STP/gm argon, which is twenty times in excess of argon expected for its age. Host granulites contain unexpectedly light oxygen, and three cordierites have δ 18O values of 2·0, 2·8, and 3·1 ‰, respectively.
Tučekite, a new antimony analogue of hauchecornite
Authors: Just J. , Feather C. E.
Published: December 2006

Synopses

Tučekite, Ni9Sb2S8, was found as microscopic grains in a mineralized Archaean chlorite schist at Kanowna (35° 35′ S., 121° 36′ E.), Western Australia, and in the gold-bearing conglomerates of the Witwatersrand System (26° S., 27° E.), South Africa.

The nickel mineralization at Kanowna is located in metamorphosed basic and ultrabasic rocks of the Morelands Formation, which is part of the Kalgoorlie-Yilgarn succession of the West Australian Archaean shield. The tučekite-bearing mineralization occurs as an approximately 2 cm thick zone of disseminated sulphides in a chlorite schist near its contact with a serpentinized ultramafic intrusive rock. Tučekite is here associated with millerite, pyrite, chalcopyrite, gersdorffite, pentlandite, magnetite, and supergene polydymite. Tučekite occurs as rims and irregular grains partly replacing millerite, and was apparently formed during the later stages of the ore-forming process by reaction of Sb-bearing solutions with millerite.

In the Witwatersrand the mineral was found in a heavy mineral concentrate prepared from ore from the Vaal Reef, Vaal Reefs mine, Klerksdorp (Far West Witwatersrand), and in a mixed concentrate from the Carbon Leader Reef and the Ventersdorp Contact Reef, Western Deep Levels Ltd., Carltonville (West Wits Line). Although rare free grains of tuSekite are found, the mineral is more commonly intergrown with gold, and in the Vaal Reef the mineral is also found intergrown with gersdorffite.

Empirical formula of the Kanowna mineral is (Ni, Fe, Co)9·05(Sb, Bi, Te)1·00(Sb, As)1·04S8; that of the Witwatersrand mineral is (Ni, Fe)9·00(Sb, Bi)1·00(Sb, AS)1·06S8. The structural formula is assumed to be ; Z = 1. The mineral is opaque, has a metallic lustre, and is pale yellow. Under the microscope in reflected light it is pale brownish-yellow; bireflectance not discernible; anisotropy very strong with deep brown and greyish-blue polarization colours; reflectivity high. Indentation hardness 718 kg/mm2 (20 g load); 417 kg/mm2 (10 g load).

Strongest Debye-Scherrer powder-pattern lines of the Witwatersrand mineral are 2·76 (10) 211; 2·38 (8) 112; 2·28 (8b) 221, 310; 1·850 (8) 222; 4·33 (7) 101; 1·793 (7) 400, 3o2. By analogy with hauchecornite, the pattern can be indexed on a tetragonal unit cell with a = 7·174 Å and c = 5·402 Å; ρ (calc.) = 6·15 g/cm3. Type material is preserved in the British Museum, London, and the National Museum, Prague (Czechoslovakia).
Tacharanite from the Gruppo di Voltri, Ligurian Alps, Italy
Authors: Lucchetti G. , Penco A. M.
Published: December 2006

Tacharanite in fractures in metagabbroic rocks filled by zeolitic assemblages has been found in the Gruppo di Voltri, Ligurian Alps. Optical properties, chemical analysis, and thermal data are reported, also mineralogical data on tobermorite found at another locality of the Gruppo di Voltri. Alteration of tacharanite into tobermorite and gyrolite was not observed, nor was an association of tacharanite and tobermorite.
Ferrierite: an Australian occurrence
Authors: England B. M. , Ostwald J.
Published: December 2006

An occurrence of the magnesian zeolite ferrierite at Unanderra, New South Wales, represents the first reported locality for this mineral in Australia. The ferrierite occurs in vesicles in latite and is associated with heulandite, laumontite, and calcite. Its crystal morphology is essentially similar to that of specimens from the type locality at Kamloops Lake in British Columbia. EPMA results are given for the Unanderra ferrierite and its chemistry relative to other known occurrences is discussed. Unanderra ferrierite contains appreciably more SrO2than other ferrierites, but is significantly lower in K2O and Na2O.
The optical constants of natural and artificial cuprite by an ellipsometric method
Authors: Roberts E. F. I. , Rastall P.
Published: December 2006

Ellipsometric measurements in the spectral range 250–850 nm have been made on polished single crystals of natural cuprite from Namibia and of artificial cuprite grown by a total-oxidation method from pure copper. Derived values of the refractive indices, absorption coefficients, normal reflectances, and the complex dielectric constants for the two materials are all closely similar, suggesting that the stoichiometry and purity are essentially the same. Values of the absorption coefficient at the red end of the spectrum are inconsistent with the observed transparency of the crystals, and are compatible with a 10 nm surface oxidation film of cupric oxide. This study is part of a wider survey of the effects of doping and stoichiometry on the optical parameters of cuprite.
Composition changes in a basalt melt contained in a wire loop of Pt80Rh20: effects of temperature, time, and oxygen fugacity
Authors: Donaldson Colin H.
Published: December 2006

Losses of FeO, Na2O, and K2O from an alkali olivine basalt melted above the liquidus temperature in Pt80Rh20wire loops are reported as a function of temperature, time, andPO2. Increasing temperature and decreasingPO2increase the losses. Compared to open capsules the wire-loop container reduces FeO loss to a minimum but may exacerbate Na2O loss. Nonetheless for most types of experiment involving melt these losses are acceptable.
A metallographic study of the iron meteorite Verkhne Dnieprovsk, BM 51183
Authors: Bevan A. W. R. , Kinder J. , Axon H. J.
Published: December 2006

The Verkhne Dnieprovsk material (BM 51183) in the collection of the British Museum (Nat. Hist.) is chemically group IIE and therefore distinct from Augustinovka. Structurally it is a finest octahedrite, with a kamacite band-width (0.05 mm) and bulk Ni content (Scott and Wasson, 1976) appropriate to a cooling rate of 830 K Myr−1. Subsequent pre-terrestrial shock has produced localized deformation and shock-heating effects, which include mm-size globules of metal-phosphide melt product with a dendritic texture indicating resolidification at c.10 000 K sec−1. It is suggested that the phosphides were already fissured at the time of shockmelting. The structure of Verkhne Dnieprovsk, although lacking silicates, is analogous to that of Kodaikanal.
Synthesis and properties of zektzerite, LiNaZrSi6O15, and its isotypes
Authors: Marr J. M. , Glasser F. P.
Published: December 2006

Synopsis

Zektzerite and its isotypes with Zr4+ replaced by Ti4+ or Sn4+ are readily synthesized by fusion of the constituent oxides at 1550 °C followed by recrystallization of the melt or quenched glass at 750–850 °C and I bar pressure. Indexed powder X-ray data for synthetic zektzerites are presented in miniprint Table I. The powder patterns are consistent with an A-centred orthorhombic symmetry. Refined cell dimensions are given in Table III.

The Ti, Zr, and Sn zektzerites melt incongruently. Table IV records melting-point data. The coefficients of thermal expansion of Zr and Ti zektzerite have been determined by X-ray dilatometry. Both have moderately low coefficients of expansion: numerical values are given in miniprint Table II.

Zektzerites contain a six-repeat unit doublechain silicate anion. Although they are chemically similar to milarites, the latter contain double-ring Si12O30 anions. Despite the difference in anion constitution both have structures in which many chemically similar atoms occupy similar positions. The effect of this similarity on the physical properties (e.g. X-ray powder pattern) is enhanced by the similar size and shape of their orthorhombic unit cells. The presence of vacant sites in zektzerite that are potentially available for cation occupancy suggests that chemically complex substitutions may occur; for example LiNa2ScSi6O15 has been synthesized and is believed to be isostructural with zektzerite and emeleusite, LiNa2FeSi6O15.
Anorthoclase megacrysts: physical conditions of formation
Authors: Bahat Dov
Published: December 2006

Previous interpretations relating to precipitation of anorthoclase megacrysts from alkaline basaltic magmas under high-pressure conditions are contradicted. It is proposed that these feldspars were crystallized above the solvus from hydrous melts at shallow depths, under low-pressure equilibrium conditions. These melts had been considerably enriched with volatiles of sodium, strontium, and barium, and to some extent also of rubidium.
Fluorian allanite from calc-granulite and pegmatite contacts at Garividi, Andhra Pradesh, India
Authors: Rao A. T. , Appa Rao G. , Prabhakara Rao P.
Published: December 2006

Synopsis

CALC-GRANULITES at Garividi are intruded by microcline granites and pegmatites. At the contacts fluorapatite, fluorian allanite, ferroan sahlite, and epidote occur; rarely, the epidote is associated with a partly metamict allanite, an analysis of which is given, also X-ray data for the unheated and heated mineral.
Ranunculite, AlH(UO2)(PO4)(OH)3 · 4H2O, a new mineral
Authors: Dellens Michel , Piret Paul
Published: December 2006

Ranunculite occurs as gold-yellow nodules. Mean diameter = 0.3 mm. Optically biaxial negative, 2V (calc.) = 56°. γ =1.670, β = 1.664, and α = 1.643. Monoclinic, pseudo-orthorhombic with a = 11.1 Å, b = 17.7 Å, c = 18.0 Å, and β ⋍ 90°. Z = 14. Measured density = 3.4 g/cm3. Calculated density = 3.39 g/cm3. The strongest lines of the X-ray powder pattern are (d, hkl, I): 9.00, 002–020 (100), 3.133, 330 (80), 470, 202–220 (50), 2.978, 006–060 (40), and 1.850, 600 (40). Chemical analysis by electron microprobe: Al2O3 9.9%, UO3 54.5%, P2O5 13.2%, H2O by thermogravimetry 20.3%. Formula: AlH(UO2)(PO4)(OH)3 · 4H2O. Ranunculite occurs at Kobokobo, Kivu, Zaïre, in pegmatitic rocks. The name after the colour (ranunculus = buttercup).
Truscottite: composition and ionic substitutions
Authors: Lachowski E. E. , Murray L. W. , Taylor H. F. W.
Published: December 2006

Eleven specimens of natural or synthetic truscottite or gyrolite-truscottite intergrowth were studied by analytical electron microscopy and X-ray powder diffraction. The results suggest that, in absence of substitution, the formula of truscottite is Ca14 (Si24O58)(OH)8 · ∼ 2H2O. Truscottite can accommodate Al and K in absence of each other to the extents of 1.4 atoms of Al or 0.5 atoms of K in the above formula. Substitution of Al causes a small increase in cell dimensions, which can approach those of reyerite, but substitution of K has negligible effect.
Spinel lherzolites from Xalapasco de la Joya, San Luis Potosi, SLP, Mexico
Authors: Greene George M. , Butler John C.
Published: December 2006

Ejecta associated with the Xalapasco de la Joya maar 33 km northeast of San Luis Potosi, SLP, Mexico, contain a diverse assemblage of nodules of postulated lower-crust/upper-mantle origin. Spinel lherzolites constitute the most abundant group of nodules and display chemical evidence that crystallization or equilibration took place at temperatures and pressures consistent with upper mantle genesis. Estimated equilibration temperatures and pressures range from 825 to 1025 °C and 7 to 19 kb.
The nature and significance of exsolved phases in some chrome spinels from the Rhum layered intrusion
Authors: Putnis A. , Price G. D.
Published: December 2006

Chrome spinels from seams in the Rhum layered intrusion, Inner Hebrides, generally contain very fine platelets of exsolved phases. Despite the low bulk Ti content (< 1%) of the spinel grains, analytical electron microscopy shows these platelets to be highly enriched in titanium. Electron diffraction indicates the presence of platelets of two different phases, one a magnesian ilmenite, the other a defect spinel intermediate phase. The platelets are the result of oxidation of the spinel at moderate (c. 600 °C) temperatures and their distribution suggests that oxygen fugacity gradients existed across some of the seams.
Rotated and extended model structures in amphiboles and pyroxenes
Authors: Law A. D. , Whittaker E. J. W.
Published: December 2006

The model for the amphibole and pyroxene structures based on close-packed oxygen layers introduced by Thompson is investigated systematically. It is shown that different features of it can best be understood in terms of three different symbolisms: the O and S rotations of tetrahedra; the A,B, C stacking notation for close-packed layers; and the c, h notation for the relationship of close-packed layers to their neighbours. The possible stacking arrangements and their space-groups are derived systematically. Relationships between the close-packed, fully rotated, model and the extended chain model are discussed, and some important drawbacks in the former model are pointed out, especially in connection with real amphibole structures.
The iron-rich blueschist-facies minerals: 3. Zussmanite and related minerals
Authors: Wood Robert Muir
Published: December 2006

Zussmanite has been found at only one locality: the Laytonville Quarry, Mendocino County, California. There are, however, present at this locality, two separate, but apparently inter-related minerals that from the evidence of chemistry, and limited diffraction information, appear to be zussmanite-type species. Their relative structural similarities are demonstrated within two rocks from the quarry in which a manganese concentration gradient has allowed ferrous-iron-rich zussmanites to develop partly contiguous overgrowths of one or other of these two minerals, one of which is a new form that has a provisionally determined ideal formula of
KAlMn3−5-8Si17O42(OH)14 and that is separated from ideal zussmanite compositions (of the form
Si17O42(OH)14) by an immiscibility gap. The other ‘zussmanite-type’ mineral has a composition that closely resembles a manganese-rich form of minne-sotaite.

The first zussmanite-type species (ZU2) has been separated and not unambiguous diffraction information obtained of its cell dimensions and powder lines, which are similar to those of zussmanite but appear to have an 8 % smaller cell-base and only a two-layer repeat (as in some of the zussmanite polytypes, and as in the talc structure). It is therefore considered possible that ZU2 has an altered compatibility between the tetrahedral and octa-hedral sheet overlap, perhaps from 13 (as in zussmanite) to 12. Whilst zussmanite appears to be a blueschist-eclogite mineral, ZU2 occurs under conditions at the low-pressure side of the blueschist facies.

An intermediate between zussmanite and the manganoan ‘minnesotaite’ is found in one rock in which the rims of zussmanite have been leached of potassium. As minnesotaite is more of a range of compositions than a structure (there is mounting evidence that it is not a simple talc-analogue) a consideration of the Laytonville manganoan minnesotaite as a zussmanite mineral is not unreasonable.
On the type locality and other occurrences of awaruite (FeNi3) in Westland, New Zealand
Authors: Rodgers K. A. , Hey M. H.
Published: December 2006

Awaruite is not known from Awarua River or Awarua Bay, Westland, New Zealand, but was first described from alluvial sands of the Gorge River and soon thereafter, in situ in serpentinite from the same valley. The name is a misnomer.
Clinopyroxene with Si < AlIV in the join CaFeAISiO6-CaTiAl2O6
Authors: Onuma Kosuke , Akasaka Masahide
Published: December 2006

Unusual clinopyroxenes were synthesized in the study of the join CaFeAlSiO6-CaTiAl2O6 in air at I atm. Clinopyroxene solid solution, hibonite solid solution, X-phase, perovskite, and corundum are present, and at subsolidus temperatures the clinopyroxene singlephase field extends up to about 19 wt% CaTiAl2O6. The CaTiAl2O6 component in the clinopyroxene however increases beyond the clinopyroxene single-phase field and attains 23 wt%. These clinopyroxene solid solutions are extremely poor in SiO2 and extremely rich in Al2O3, Fe2O3, and TiO2, and more than half of tetrahedral sites are occupied by AlIV, contravening the aluminium avoidance principle.
Mineralization at Le Pulec, Jersey, Channel Islands
Authors: Ixer R. A. , Stanley C. J.
Published: December 2006

Veins cutting the Brioverian sediments at Le Pulec, Jersey, were worked in the 1870s for silver and lead. Investigation of the mineralogy of both the sediments and cross-cutting veins has shown a complex mineralization history. Siltstones close to the contact with the North-West granite have been bleached, silicified, and dolomitized, and this has been accompanied by the introduction of pyrite, marcasite, and arsenopyrite. Later vein mineralization contains sphalerite and ferroan dolomite accompanied by lesser amounts of galena and chalcopyrite and minor quantities of argentian tetrahedrite, native antimony, bournonite, cubanite, plagionite, and stibnite. The mineral assemblage is unlike the other mineral occurrences of Jersey that have previously been described.
Unusual perovskite textural relationships in olivine melilitites from Namaqualand-Bushmanland, South Africa
Authors: Moore A. E.
Published: December 2006

Textural relationships shown by oxide phases in olivine melilitites from Namaqualand-Bushmanland, South Africa, indicate early crystallization of picroilmenite from a relatively reduced magma. Evolution of a CO2-rich vapour during magma ascent led to an increase in oxygen activity and liquidus temperatures, causing rapid crystallization of titanomagnetite. Higher oxygen activities, together with the increase in calcium activity following CO2 loss from the magma, resulted in perovskite replacing ilmenite as the stable Ti phase.
Edge dislocations in fibrous grunerite
Authors: Whittaker E. J. W. , Cressey B. A. , Hutchison J. L.
Published: December 2006

Sections perpendicular to [001] of ion-thinned specimens of fibrous grunerite (amosite) have been examined by high-resolution transmission electron microscopy. In this orientation, two kinds of dislocation have been observed with about equal frequency. One lies on [001] and has a Burgers vector a. The other is on [001] and has a Burgers vector ½a+½b Interpretation of features associated with these dislocations has been assisted by the use of two-dimensional models of I-beam cross-sections which can be interlocked to simulate the possible modes of stacking.
The plagioclase, forsterite, diopside, liquid equilibrium in the system CaO-Na2O-MgO-Al2O3-SiO2
Authors: Biggar G. M. , Humphries D. J.
Published: December 2006

Liquids in the system CaO-Na2O-MgO-Al2O3-SiO2which crystallize plagioclase and forsterite, often with diopside and sometimes with spinel, were studied. The movement of the plagioclase-forsterite saturation surface to higher plagioclase contents as albite replaces anorthite, and the concurrent expansion of the forsterite and diopside primary fields, are documented. The maximum temperature of the liquid in equilibrium with plagioclase, diopside, and forsterite decreases as the anorthite to albite ratio decreases and as enstatite is added, and was experimentally determined over part of its range from 1278 to 113°C The decrease was not linear, being generally small even when 67 mole% albite was present, and thereafter, it must decrease rapidly to reach the values reported for the system albite-diopside-forsterite.
Synthesis of Li2ZrSi6O15, a zektzerite-related phase
Authors: Quintana Patricia , West Anthony R.
Published: December 2006

Considerable recent interest has been shown in a group of double-chain silicate phases which includes the new mineral zektzerite, LiNaZrSi6O15 (Dunn et al., 1977; Ghose and Wan, 1978), and a family of isotypic phases (Marr and Glasser, 1979a and b). These phases are closely related structurally to Na2Mg2Si6O15 (Cradwick and Taylor, 1972), tuhualite, (Na,K)2Fe2+2Fe3+2Si12O30.H2O (Merlino, 1969), and emeleusite, Na2LiFeSi6O15 (Upton et al., 1978).
Reactions between uranium veins and their host rocks in Vendée and Limousin (France)
Authors: Cathelineau M. , Leroy J.
Published: December 2006

Hydrothermal uranium veins, associated with the Hercynian leucogranites show important variations in their mineralogical, chemical and structural features in relation to the host rock lithology. These are described with particular reference to the Chardon deposit, Vendée where the veins cut granite, basic lithologies, and shales. The following features are described:

1

Changes in the thickness of veins near to contact zones, particularly those between granites and basic lithologies, lamprophyres, and shales.

2

Changes in the gangue mineral assemblage with the preferential development of carbonate in veins cutting basic lithologies, and of silica in veins which cut granite.

3

Paragenetic zoning in the veins in passing from granites to their metamorphic aureoles.

Comparisons between deposits of Vendée, Limousin, and Erzgebirge allow the following generalizations to be made:

1

Open faults and subsequent mineralization are concentrated at boundaries between competent and more plastic lithologies.

2

Mineralizing fluids cause wall-rock alteration characterized by the removal of Si from granite and of Ca, Mg, Fe from metamorphic and basic rocks.

3

The chemical and structural characteristics of wallrocks are important controls on the mineralization but in acid lithologies the main controls on the pitchblende vein formation are the structural characteristics of the wallrock.
Pink zoisite from the Aar Massif, Switzerland
Authors: Abrecht J.
Published: December 2006

Veins in the Central Aar granite consisting of zoisite, plagioclase, albite, alkali feldspar, muscovite, tremolite, quartz, and calcite are described. The zoisite is a thulite with up to 0.20 wt% MnO. It is argued that the zoisite is derived from granite plagioclases and has recrystallized in veins during alpine greenschist metamorphism. By later increasing XCO2 or decreasing temperature zoisite decomposed to calcite, plagioclase, and muscovite.

Thulites from different localities were investigated by X-ray and by electron microprobe analysis. Both orthorhombic and monoclinic members of the epidote group having low MnO contents have been described as thulites. It is suggested that low MnO values in the range 0.05 to 0.9 wt% cause the pink colour of thulites, regardless of symmetry.
Silver sulphosalts from the Meerschaum Mine, Mt. Wills, Victoria, Australia
Authors: Birch W. D.
Published: December 2006

A rich vein of silver and silver-lead sulphosalt minerals was discovered in 1906 in the Meerschaum Mine, on the Sunnyside goldfield at Mt. Wills, in northeastern Victoria. Andorite, miargyrite, tetrahedrite (freibergite), owyheeite, and argentian gold are the main silver-bearing minerals present, and sphalerite, pyrite, arsenopyrite, and covelline also occur in the vein.

The vein was probably emplaced under epithermal conditions from ore fluids accompanying the intrusion of the Mt. Wills granite. The main silver-bearing minerals were probably deposited at temperatures ranging from about 350 ° to below 300 °C.
Cr-rich spinel and garnet in two peridotite xenoliths from the Frank Smith mine South Africa: Significance of Al and Cr distribution between spinel and garnet
Authors: Exley R. A. , Smith J. V. , Hervig R. L.
Published: December 2006

Peridotite xenoliths 73–106 and 73–109 have coarse textures. All minerals in 73–106 are very Ti-rich, and include olivine (Fo 87.6), orthopyroxene (En 90.0), garnet (core TiO2 0.8, Cr2O3 7; rim 1.4, 4 wt. %), spinel (TiO2 5, Cr2O3 38), clinopyroxene (A12O3 1–8) secondary mica (TiO2 6, Cr2O3 2.5 near garnet 0.5 away from garnet), and serpentine (FeO 5–12) enclosing perovskite-rimmed ilmenite and minute apatites. All minerals in peridotite 73–109 are Ti-poor, and include olivine (Fo 92.6), orthopyroxene (En 93.6), garnet (Cr2O3 3.1–3.8), spinel (55), ureyitic diopside, primary mica (TiO2 0.06, Cr2O3 1.0, BaO 0.5, Cl 0.04), and serpentine (FeO 2–23). Various thermometers indicate ∼ 1350K (73–106) and 1100K (73–109). The low Al2O3 in the orthopyroxenes gives 39–47 kb for 73–109 from the Wood-Banno barometer. In 73–106, the spinel lies in secondary mica next to the garnet rim, whereas the spinel of 73–109 occurs in grains enclosed by garnet. The former assemblage indicates diffusion-dependent disequilibrium, whereas the latter is attributed to simultaneous growth of spinel and garnet, perhaps consequent upon exsolution from orthopyroxene. Complex behaviour was found for the Cr/Al distribution in published analyses of garnet and spinel. The 73–109 pair lies near the Thaba Putsoa trend, and the 73–106 assemblages are displaced towards the kelyphite region in which garnet and spinel have similar Cr/Al. Spinel and garnet may coexist over a 30 kb pressure interval ranging from ∼ 16 kb for low bulk Cr to ∼ 40 kb for high Cr.
Exsolution in titanomagnetites as an indicator of cooling rates
Authors: Price Geoffrey D.
Published: December 2006

The scale and nature of the exsolution textures developed in some titanomagnetites have been used to calculate the rate at which the oxides were cooling at the time of exsolution. The cooling rates were calculated by evaluating a kinetic model, which describes the growth of an ulvöspinel-rich lamella in titanomagnetite during exsolution. The model was evaluated both by numerical techniques and by an approximate analytical method.

The cooling rates during titanomagnetite exsolution of the Taberg, Skaergaard and part of the Mt. Yamaska intrusions were calculated to be approximately 130, 12 and 6000°C per 1000 years respectively. These values are in good agreement with cooling rates calculated from heat flow models of the intrusions.
Uranium and selected trace elements in granites from the Caledonides of East Greenland
Authors: Steenfelt Agnete
Published: December 2006

The Caledonian fold belt of East Greenland contains calc-alkaline granite(sensu lato)intrusions with ages ranging fromc.2000 Ma toc.350 Ma. The Proterozoic granites have low U contents and the pre-Devonian Caledonian granites contents of U corresponding to the clarke value for U in granites. Some aspects of the geochemistry of U are discussed using U-K/Rb, U-Sr, U-Zr, and U-Th diagrams. Secondary enrichment and mineralization occurs in fractured and hydrothermally altered granites and rhyolites situated in or near a major NNE fault zone. The U is associated with iron oxides or hydrocarbons. It is suggested that the source of the mineralization was Devonian acid magma, which also acted as a heat source for circulating hydrothermal fluids.
Cuzticite and eztlite, two new tellurium minerals from Moctezuma, Mexico
Authors: Williams S. A.
Published: December 2006

The new minerals were found together in oxidized ores at the Bambolla mine, Moctezuma, Sonora. Both occur with various iron oxides, emmonsite, schmitterite, and kuranakhite. Cuzticite, Fe2TeO6 · 3H2O, is yellowish, H = 3, G = 3.9, occurring as crusts with a scaly structure. No single crystals were found, but X-ray powder data indicate a hexagonal cell a = 5.045, c = 14.63 Å. Strongest lines are 3.256 (10), 2.518 (7), 4.871 (4), 2.239 (3), and 1.564 (3).

Eztlite, Fe6Pb2(TeO3)3TeO6(OH)10 · nH2O, is blood red, as paper-thin sparkling crusts, H = 3, G = 4.5. A possible cell found by the Ito method is monoclinic a = 6.58, b = 9.68, c = 20.52Å, β = 90° 15′; strongest lines are 3.426 (10), 3.289 (10), 4.037 (9), 3.239 (9), and 2.445 (7B).

Both minerals and their names have been approved by the Commission on New Minerals and Mineral Names, IMA.
Al-Cr substitution in peraluminous sapphirines from the Bjørnesund area, Fiskenaesset region, southern West Greenland
Authors: Friend C. R. L.
Published: December 2006

Cr-rich Mg-sapphirines, which are more aluminous in composition than R2+:R3+:Si of 7:9:3 and are therefore considered to be peraluminous, are shown to have an inverse linear relationship between octahedrally co-ordinated Cr and Al. This balanced substitution, which has not previously been described, may be used to explain the major chemical variations exhibited in the described minerals. Since the peraluminous Cr-rich sapphirines are idioblastic it is suggested that they are stable members of the assemblages within which they occur. Peraluminous sapphirine is usually considered to be metastable but in this instance it is possible that chromium may assist in stabilizing its development.
Peisleyite, a new sodium aluminium sulphate phosphate
Authors: Pilkington E. S. , Segnit E. R. , Watts J. A.
Published: December 2006

A new sodium aluminium sulphate phosphate has been named peisleyite. It has the ideal formula Na3Al16(SO4)2(PO4)10(OH)17 · 20H2O. It occurs as fine-grained, compact, brittle, white material on dumps at Tom's Phosphate Quarry, near Kapunda, South Australia. Strongest X-ray diffraction lines are 12.63 Å (100) 010, 7.82(35) 11, 5.41(35) 004, 7.59(30) 111. Unit cell parameters are a 13.31 ± 0.006, b 12.62 ± 0.006, c 23.15 ± 0.01 Å, β 110.0°±0.03°, Z = 2.
Mineralogy and petrology of the Highland Border Suite serpentinites
Authors: Ikin N. P. , Harmon R. S.
Published: December 2006

Prior to serpentinization, the ultramafic rocks of the ophiolitic Highland Border Suite were depleted harzburgites, dunites, and orthopyroxenites. They may have been the residual mantle after melting of primary lherzolite that produced the basaltic rocks of the Suite. Serpentinization of these peridotites occurred at low temperatures (75±50°C) and produced pseudomorphic-textured lizardite serpentinites in which the minor-element compositions of the primary phases were preserved in the lizardite grains. Olivine was almost completely serpentinized before orthopyroxene was hydrated. Concomitant peripheral alteration of chromespinels, during serpentinization of orthopyroxene, caused release of Cr and Al cations which were incorporated into the lizardite. Under greenschist-facies conditions (c. 350°C at 3–4 kbar), the lizardite serpentinites were subsequently metamorphosed and recrystallized to nonpseudomorphic-textured antigorite serpentinites. Postmetamorphic processes included high-level brittle deformation that resulted in fracturing and cross-fibre chrysotile vein-formation, and ductile shearing (T ∼ 200 °C, P < 2 kbar) which produced talc-chrysotile shear zones.
New IR and XRD data for leadhillite of ideal composition
Authors: Russell J. D. , Milodowski A. E. , Fraser A. R. , Clark D. R.
Published: December 2006

The infra-red spectrum and X-ray powder pattern of a chemically analysed specimen of leadhillite, a lead carbonate sulphate hydroxide mineral from Leadhills, Scotland, are shown to be different from those in the literature. The IR spectra of several specimens suggest that mutual replacement of SO4, CO3, and OH may occur in this mineral, and it is thought that this might be responsible for the observed variation in X-ray spacings.
Some aspects of the silver mineralization in the Hällefors region (Bergslagen, Sweden)
Authors: Jasinski A. W.
Published: December 2006

Sulphide and sulphosalt mineralization in the Hällefors silver mining district occurs as stratabound bodies in skarn-like black carbonates and other carbonates in the eastern part of the district, and as epigenetic, tectonically controlled vein mineralization in tuffaceous metavolcanics and, to a lesser extent in slates, in the western part.

Previous work has suggested that the Ag-bearing Hällefors deposits were formed by the action of metamorphic solutions on sediments of volcano-sedimentary origin. At the stages of sulphosalt and sulphide formation, temperature and pressure conditions were probably in the ranges 500–440 K and 4.5–3.5 kbar. Examination of a logaS2-1/Tdiagram and of Ag-Sb phase relations combined with study of the ores suggest the paragenesis of the Ag-bearing minerals is as follows: allargentum and dyscrasite as exsolution bodies in silver bearing galena; Ag-containing tetrahedrite → freibergite → miargyrite → pyrargyrite → stephanite (from hydrothermal solutions).
Ganophyllite from Franklin, New Jersey; Pajsberg, Sweden; and Wales new chemical data
Authors: Dunn Pete J. , Peacor Donald R. , Nelen Joseph E. , Ramik Robert A.
Published: December 2006

Ganophyllite from Franklin, New Jersey, Pajsberg, Sweden, and the Benallt Mine, Wales, has been chemically reinvestigated. Twelve new analyses confirm the general structure of Kato (1980) and yield the tentative formula (K,Na,Ca)2Mn8(Si,Al)12(O,OH)32(OH)4·8H2O. There is little solid solution among octahedral cations, and the Si:Al ratio is nearly constant at 10:2. Ca and (Na + K) are apparently differentiated, but all examined ganophyllites are K-rich. Much of the water content is loosely bound and the upper limit of water content is not well defined. Ganophyllite is relatively invariant in chemical composition from locality to locality.
Fully oxidized chromite in the Serra Alta (South Portugal) quartzites: chemical and structural characterization and geological implications
Authors: Figueiras Jorge , Waerenborgh Joāo C.
Published: December 2006

Several quartzite bodies outcrop along the Ferreira-Ficalho Thrust Fault (South Portugal), a major accident of the Iberian Variscan Orogen. The sediment is a very pure quartz sandstone, with trace amounts of ultra-resistant heavy minerals and chromite. Chemical characterization (microprobe analyses and Mössbauer spectroscopy) showed the chromite to be unique: besides being Zn-rich, complexly zoned and a cation deficient spinel, all the iron was found to be fully oxidized to Fe3+. Structure refinement of single-crystal X-ray diffraction intensities unambiguously identifies the mineral as a chromite and the Mössbauer data are consistent with tetrahedrally coordinated Fe3+ in the spinel structure. Current geodynamical models see the Ferreira-Ficalho Thrust Fault as a first-order suture resulting from a complex collision of two distinct continental blocks with partial obduction of the intervening oceanic crust. The chromite grains could be envisaged as remnants of an early erosion of this obducted oceanic crust, but its unique chemical character does not allow any definite conclusion. Yet, the complete quartzite heavy mineral contents and its petrographic features are not consistent with their deposition within a continental collision situation.
Vaccine-delivered HIV envelope inhibits CD4+ T-cell activation, a mechanism for poor HIV vaccine responses
Authors: Fernando Kathy , Hu Haitao , Ni Houping , Hoxie James A. , Weissman Drew
Published: December 2006

The human immunodeficiency virus (HIV) causes impairment of the immune system in part by targeting CD4+ T cells for infection and dysfunction. HIV envelope (Env) present on free virions and infected cells causes dysfunction of uninfected bystander CD4+ T cells via interaction with both CD4 and coreceptors. Env is commonly used as part of a cocktail of HIV antigens in current vaccines. In DNA and viral vector vaccine approaches, antigen-presenting cells (APCs) and non-APCs in the vicinity of the vaccine delivery site and draining lymph node express vaccine-derived antigens. The studies here demonstrate that cell-surface expression of Env on APCs and non-APCs as part of the vaccine action causes an inhibition of antigen-induced CD4+ T-cell activation and proliferation mediated by CD4 binding and suggests a potential mechanism for reduced activity of Env-containing HIV vaccines. Similar studies using a functional Env lacking CD4 binding circumvented suppression, suggesting an alternative and potentially superior approach to HIV vaccine design.
Tissue-type plasminogen activator–mediated shedding of astrocytic low-density lipoprotein receptor–related protein increases the permeability of the neurovascular unit
Authors: Polavarapu Rohini , Gongora Maria Carolina , Yi Hong , Ranganthan Sripriya , Lawrence Daniel A. , Strickland Dudley , Yepes Manuel
Published: December 2006

The low-density lipoprotein receptor–related protein (LRP) is a member of the LDL receptor gene family that binds several ligands, including tissue-type plasminogen activator (tPA). tPA is found in blood, where its primary function is as a thrombolytic enzyme, and in the central nervous system where it mediates events associated with cell death. Cerebral ischemia induces changes in the neurovascular unit (NVU) that result in brain edema. We investigated whether the interaction between tPA and LRP plays a role in the regulation of the permeability of the NVU during cerebral ischemia. We found that the ischemic insult induces shedding of LRP's ectodomain from perivascular astrocytes into the basement membrane. This event associates with the detachment of astrocytic end-feet processes and the formation of areas of perivascular edema. The shedding of LRP's ectodomain is significantly decreased in tPA deficient (tPA−/−) mice, is increased by incubation with tPA, and is inhibited by the receptor-associated protein (RAP). Furthermore, treatment with either RAP or anti-LRP IgG results in a faster recovery of motor activity and protection of the integrity of the NVU following middle cerebral artery occlusion (MCAO). Together, these results implicate tPA/LRP interactions as key regulators of the integrity of the NVU.
Compensatory relationship between splice sites and exonic splicing signals depending on the length of vertebrate introns
Authors: Dewey Colin N , Rogozin Igor B , Koonin Eugene V
Published: December 2006

Background

The signals that determine the specificity and efficiency of splicing are multiple and complex, and are not fully understood. Among other factors, the relative contributions of different mechanisms appear to depend on intron size inasmuch as long introns might hinder the activity of the spliceosome through interference with the proper positioning of the intron-exon junctions. Indeed, it has been shown that the information content of splice sites positively correlates with intron length in the nematode, Drosophila, and fungi. We explored the connections between the length of vertebrate introns, the strength of splice sites, exonic splicing signals, and evolution of flanking exons.

Results

A compensatory relationship is shown to exist between different types of signals, namely, the splice sites and the exonic splicing enhancers (ESEs). In the range of relatively short introns (approximately, < 1.5 kilobases in length), the enhancement of the splicing signals for longer introns was manifest in the increased concentration of ESEs. In contrast, for longer introns, this effect was not detectable, and instead, an increase in the strength of the donor and acceptor splice sites was observed. Conceivably, accumulation of A-rich ESE motifs beyond a certain limit is incompatible with functional constraints operating at the level of protein sequence evolution, which leads to compensation in the form of evolution of the splice sites themselves toward greater strength. In addition, however, a correlation between sequence conservation in the exon ends and intron length, particularly, in synonymous positions, was observed throughout the entire length range of introns. Thus, splicing signals other than the currently defined ESEs, i.e., potential new classes of ESEs, might exist in exon sequences, particularly, those that flank long introns.

Conclusion

Several weak but statistically significant correlations were observed between vertebrate intron length, splice site strength, and potential exonic splicing signals. Taken together, these findings attest to a compensatory relationship between splice sites and exonic splicing signals, depending on intron length.
Molecular Markers of Urothelial Cancer and Their Use in the Monitoring of Superficial Urothelial Cancer
Authors: Black Peter C. , Brown Gordon A. , Dinney Colin P.
Published: December 2006

Multiple molecular markers have been described for use in bladder cancer patients. Some of these have been studied more extensively than others, and it is difficult for the clinician to maintain a perspective over the myriad findings that have been made. We have reviewed a selection of markers used for surveillance with an emphasis on clinical utility. The best studied markers and those with the most promising preliminary results were selected. Only studies that included surveillance for recurrence in patients with a history of bladder cancer were considered. Each marker is briefly described and its performance in monitoring bladder cancer patients is summarized. Several promising markers are available, although only four have obtained US Food and Drug Administration approval. The clinical applications that have been studied include replacement or reduction in the number of cystoscopies performed in the surveillance of bladder cancer patients, substitution for or complementary use with urinary cytology in the same setting, predicting disease recurrence and progression, and predicting and monitoring treatment response. None of the markers have been proved sensitive and specific enough to replace cystoscopy. Others, such as nuclear matrix protein 22 (NMP22) and UroVysion, appear to have some utility when used to complement or replace cytology. The other applications have not been adequately studied for any given marker. While multiple molecular markers exist for bladder cancer, their full clinical utility will not be realized until more multicenter prospective trials are conducted to verify their efficacy and safety in the monitoring of patients with superficial bladder cancer.