bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metasomatism in the Wairere Serpentinite, King Country, New Zealand
Authors: Leach T. M. , Rodgers K. A. 
Published: December 2006

SummaryMetasomatic 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

SummaryTwo 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

SynopsesTučekite, 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

SummaryTacharanite 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

SummaryAn 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

SummaryEllipsometric 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

SummaryLosses 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

SummaryThe 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

SynopsisZektzerite 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

SummaryPrevious 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

SynopsisCALC-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

SummaryRanunculite 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

SummaryEleven 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

SummaryEjecta 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

SummaryChrome 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

SummaryThe 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

SummaryZussmanite 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

SummaryAwaruite 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

SummaryUnusual 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

SummaryVeins 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

AbstractTextural 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

AbstractSections 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

AbstractLiquids 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.
Reactions between uranium veins and their host rocks in Vendée and Limousin (France)
Authors: Cathelineau M. , Leroy J. 
Published: December 2006

AbstractHydrothermal 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:
1Changes in the thickness of veins near to contact zones, particularly those between granites and basic lithologies, lamprophyres, and shales.2Changes in the gangue mineral assemblage with the preferential development of carbonate in veins cutting basic lithologies, and of silica in veins which cut granite.3Paragenetic 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:
1Open faults and subsequent mineralization are concentrated at boundaries between competent and more plastic lithologies.2Mineralizing fluids cause wall-rock alteration characterized by the removal of Si from granite and of Ca, Mg, Fe from metamorphic and basic rocks.3The 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.