The iron-titanium oxides of some Dunedin (New Zealand) lavas, in relation to their palaeomagnetic and thermomagnetic character (with an appendix on associated chromiferous spinel)

1967 ◽  
Vol 36 (279) ◽  
pp. 425-435 ◽  
Author(s):  
J. B. Wright
Keyword(s):  
New Zealand ◽  
Low Temperature ◽  
Small Degree ◽  
Titanium Oxides ◽  
X Ray ◽  
Reversal Process ◽  
Titaniferous Magnetite ◽  
Unpublished Work ◽  
Cell Dimensions ◽  
Reversed Polarity

SummaryEarlier palaeomagnetic studies on the Dunedin volcano showed that a portion of the sequence is reversely or anomalously magnetized. Some of the rocks used for palaeomagnetic study were subsequently classified into groups according to their thermomagnetic behaviour (unpublished work).Cell dimensions and Curie-point curves have been measured for oxides separated from representative rocks of each group. The oxides are mostly homogeneous titanomagnetites containing between 40 and 55 mol. % of ulvöspinel, with a generally small degree of late low-temperature alteration. X-ray and thermomagnetic data also suggest that there was some early oxidation to titanomaghemite, probably during cooling.The thermomagnetic behaviour of rocks classified in the different groups is attributed to variable oxidation of the titanomagnetite during thermomagnetic treatment. The high Curie points of rocks used for palaeomagnetic studies may often be due merely to oxidation of titaniferous magnetite and not to nearly pure primary Fe3O4. Since there is insufficient oxidation in the lavas examined for any currently accepted self-reversal process to have been operative, the reversely magnetized part of the Dunedin sequence was probably erupted during a reversed polarity epoch, possibly between about 13 and 11 million years ago.The basanitic lavas contain minor amounts of chromiferous spinel, as inclusions in silicate phenocrysts and as cores to separate microphyric titanomagnetite; its significance is briefly discussed.

The determination of composition and thermal history of plagioclase by the X-ray powder method

1955 ◽  
Vol 30 (229) ◽  
pp. 648-656 ◽  
Author(s):  
J. Goodyear ◽  
W. J. Duffin
Keyword(s):  
Chemical Composition ◽  
Low Temperature ◽  
Similar Composition ◽  
X Ray ◽  
Naturally Occurring ◽  
Cell Dimensions ◽  
History Of ◽  
Unit Cell Dimensions ◽  
Ray Patterns

In a recent paper (hereafter referred to as GD) Goodyear and Dufiln (1954) described X-ray powder data for a number of synthetic and chemically analysed plagioclases of composition An0Abl00-Anl00Ab0. Important aspects of this work were a correlation of the X-ray patterns with chemical composition, and a distinction between the pattern of a naturally occurring material of low-temperature origin and that of a synthetic of similar composition. The investigation showed quite clearly that the unit-cell dimensions of a synthetic plagioelase depend but little on composition from An0Abl00 to An70Ab30, whilst they differ from those of the low-temperature modification greatly for albite, to a lessening degree as the composition approaches An70Ab30, and practically not at all in the range An70Ab30-Anl00Ab0.

The Preparation, Spectroscopic Characterization and X-Ray Structure of the Salt [Pt(η1 -C6H9)(Cy2PCH2CH2PCy2)(PPh3)]HCO3·3H2O Containing the Discrete, Uncoordinated, Hydrogen-Bonded Dimeric Bicarbonate Dianion [(HCO3)(H2O)3]22-

1999 ◽  
Vol 52 (10) ◽  
pp. 949 ◽  
Author(s):  
Martin A. Bennett ◽  
Glen B. Robertson ◽  
Pramesh N. Kapoor
Keyword(s):  
Low Temperature ◽  
Spectroscopic Characterization ◽  
Coordination Geometry ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
X Ray ◽  
Cell Dimensions ◽  
R Value ◽  
Unit Cell Dimensions ◽  
Hydrogen Bonded

Reaction of the cyclohexyne–platinum(0) complex [Pt(η2-C6H8)(Cy2PCH2CH2PCy2)]* with water and CO2 in the presence of triphenylphosphine gives the bicarbonate salt of the (η1-cyclohexenyl)platinum(II) cation, [Pt(η1-C6H9)(Cy2PCH2CH2 PCy2)(PPh3)] [HCO3] · 3H2O, which has been characterized by n.m.r. spectroscopy and single-crystal X-ray diffraction at low temperature. Crystals are triclinic, space group P1– with unit cell dimensions a 20.315(2), b 12.782(1), c 10.694(1) Å, α 66.61(1), β 104.73(1), γ 102.11(1)˚, and Z 2. The structure was refined to a final R value of 0.036 with use of 7553 reflections [I > 3σ(I)]. The cation has the expected, somewhat distorted planar coordination geometry; the anion consists of discrete, hydrogen-bonded dimers [(HCO3)(H2O)3]22-.

Powder diffraction data and Rietveld refinement of metastable t-ZrO2 at low temperature

1997 ◽  
Vol 12 (2) ◽  
pp. 96-98 ◽  
Author(s):  
J. Málek ◽  
L. Beneš ◽  
T. Mitsuhashi
Keyword(s):  
Low Temperature ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

Indexed X-ray powder diffraction data are reported for the low temperature tetragonal ZrO2 obtained by crystallization of zirconia gel. The structure was refined by the Rietveld technique on the basis of space group P42/nmc. Refined unit cell dimensions are a = 3.5984(5) Å, c = 5.152(1) Å, V = 66.71 Å3, Dx=6.135 g/cm3, F18=62 (0.012, 24), RP=8.99, Rwp=11.48, RB=3.13.

Nepheline solid solutions

1959 ◽  
Vol 32 (245) ◽  
pp. 93-109 ◽  
Author(s):  
Gabrielle Donnay ◽  
J. F. Schairer ◽  
J. D. H. Donnay
Keyword(s):  
Low Temperature ◽  
Cell Volume ◽  
Solid Solutions ◽  
Binary Systems ◽  
Calcium Content ◽  
Potassium Content ◽  
Chemical Analyses ◽  
X Ray ◽  
Cell Dimensions

SummaryPublished chemical analyses demonstrate that the nepheline formula should be written KxNayCaz□s-(x+y+z)Alx+y+2zSi16-(x+y+2z)O32, where □ stands for vacant sites. X-ray data are presented for the nepheline phase in four binary systems: Ne-CaAl2O4, Ne-An, Ne-Ab, Ne-Kp. Only in two of these systems do the cell-dimensions change with composition. In the first one, the cell-volume V increases linearly with increasing calcium content; in the last one, two singularities in the curve of V against x divide the phase Na8-xKxAl8Si8O32 into three subphases: subpotassic (0 < x < 0·25), mediopotassic (0·25 < x < 2·00), and perpotassic (2·00 < x < 4·73). Only in the subpotassic range are both high- and low-temperature forms found. Twenty-eight natural nephelines, for which chemical analyses and X-ray data are available in the literature, show that only the potassium content affects cell-dimensions. Although all analysed natural nephelines fall outside the subpotassic range, the re-examination of a Monte Somma specimen studied by Bannister (1931) reveals a few euhedral crystals of subpotassic nepheline in a mediopotassic phase.

Pyroxene and magnetite phenocrysts from the Taupo quaternary rhyolitic pumice deposits, New Zealand

1967 ◽  
Vol 36 (278) ◽  
pp. 180-194 ◽  
Author(s):  
A. Ewart
Keyword(s):  
Solid Solution ◽  
New Zealand ◽  
Solid Solutions ◽  
Primary Crystallization ◽  
Early Separation ◽  
X Ray ◽  
Subsequent Oxidation ◽  
Weathering Processes ◽  
Titaniferous Magnetite ◽  
Initial Iron

SummaryChemical data are presented for four hypersthenes and one coexisting hypersthene-augite pair, and chemical, X-ray, and thermomagnetic data presented for five titaniferous magnetites, all from various horizons of the Taupo pumice sequence. These phenocrysts are regarded as primary crystallization products, and not of xenocrystic origin. The hypersthenes range from Mg46·4Fe51·4Ca2·2 to Mg65·7Fe31·2Ca3·1; the augite composition is Mg48·5Fe12·3Ca39·2. The occurrence of such magnesian pyroxenes may be explained by the early separation of titaniferous magnetite, although it is also possible that the initial iron ratios of the liquids were already sufficiently low to precipitate these pyroxenes.The magnetites exhibit varying stages of oxidation. Data on the least oxidized specimens indicate they were initially magnetite-ulvöspinel solid solutions, with 40 to 50% (mol.) solid solution ulvöspinel. Subsequent oxidation has modified their compositions; there is some evidence that this could have occurred during normal weathering processes.

Unit cell volumes of synthetic orthoenstatite and low clinoenstatite

1966 ◽  
Vol 35 (274) ◽  
pp. 838-846 ◽  
Author(s):  
D. A. Stephenson ◽  
C. B. Sclar ◽  
J. V. Smith
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Confidence Level ◽  
Statistical Test ◽  
Transition Curve ◽  
X Ray ◽  
Metastable Form ◽  
Cell Dimensions ◽  
Experimental Transition ◽  
Cell Volumes

SummaryCell dimensions and densities derived from least-squares refinement of X-ray powder diffractometer patterns are: orthoenstatite, a 18·2249±0·0013, b 8·8149±0·0008, c 5·1746±0·0008 Å, V 831·30±0·14 Å3, D 3·208 g/cc ; low clinoenstatite, a 9·6065±0·0011, b 8·8146±0·0007, c 5·1688±0·0006 Å, β = 108·335± 0·009, V 415·46±0·09 Å3, D 3·210 gm/cc. Because orthoenstatite transforms reversibly to clinoenstatite at high pressure and low temperature, and because a statistical test shows that orthoenstatite is less dense than clinoenstatite at the 90 % confidence level (in accord with the direction of slope of the experimental transition curve), it is no longer possible to regard low clinoenstatite as a metastable form of MgSiO3.

Re-examination of the mineral tuhualite

1956 ◽  
Vol 31 (232) ◽  
pp. 96-106 ◽  
Author(s):  
C. Osborne Hutton
Keyword(s):  
New Zealand ◽  
Unit Cell ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions ◽  
Goniometric Measurements ◽  
Unit Cell Dimensions

SummaryX-ray study of tuhualite from Mayor Island, New Zealand, has shown it to be orthorhombic, space-group either . Unit-cell dimensions are a = 14·31 Å, b = 17·28 Å., c = 10·11 Å., and a : b : c = 0·828 : 1 : 0·585. Goniometric measurements give a : b : c = 0·8243 : 1 : 0·5658. a{100} dominant with forms s{011}, p{021}, c{001}, b{010}, n{101}, m{110}, q{111}. Crystals with b{010} dominant are rare. Three good cleavages, a (100), b (010), c (001). α = 1·608, β = 1·612, γ = 1·621; γ-α = 0·013. , positive; β = b, γ = c, α = colourless to pale lavender, β = violet, lavender, γ = intense purplish-blue; γ > β > α. Sp. gr. 2·89 (measured), 2·86 (calculated).An analysis of carefully purified material leads to the possible formula:H9(Na,K,Mn)12Fe″6(Al,Fe‴,Mg,Ti)9[Si8O8]15.Details of alteration phenomena and associated minerals are given. Occurrence is held to result by crystallization from magma quite impoverished in lime due to early fractionation of aegirine-hedenbergite, and perhaps aegirine-augite, in the intratelluric stage.

The External Shape of Human γ GI Immunoglobulin from Crystal Sections

1971 ◽  
Vol 29 ◽  
pp. 428-429
Author(s):  
L. W. Labaw
Keyword(s):  
Molecular Weight ◽  
Sodium Phosphate ◽  
Osmium Tetroxide ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
X Ray ◽  
Large Molecular Weight ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Crystallographic Axes

Crystals of a human γGl immunoglobulin have the external morphology of diamond shaped prisms. X-ray studies have shown them to be monoclinic, space group C2, with 2 molecules per unit cell. The unit cell dimensions are a = 194.1, b = 91.7, c = 51.6Å, 8 = 102°. The relatively large molecular weight of 151,000 and these unit cell dimensions made this a promising crystal to study in the EM.Crystals similar to those used in the x-ray studies were fixed at 5°C for three weeks in a solution of mother liquor containing 5 x 10-5M sodium phosphate, pH 7.0, and 0.03% glutaraldehyde. They were postfixed with 1% osmium tetroxide for 15 min. and embedded in Maraglas the usual way. Sections were cut perpendicular to the three crystallographic axes. Such a section cut with its plane perpendicular to the z direction is shown in Fig. 1.This projection of the crystal in the z direction shows periodicities in at least four different directions but these are only seen clearly by sighting obliquely along the micrograph.

Low temperature x-ray microanalysis of frozen-hydrated tobacco leaves

1984 ◽  
Vol 42 ◽  
pp. 284-285
Author(s):  
S. Edith Taylor ◽  
Patrick Echlin ◽  
May McKoon ◽  
Thomas L. Hayes
Keyword(s):  
Low Temperature ◽  
Lemna Minor ◽  
Root Tips ◽  
Tobacco Leaves ◽  
X Ray ◽  
Whole Cells ◽  
Carbon Coated ◽  
The Right ◽  
Beam Currents ◽  
The University

Low temperature x-ray microanalysis (LTXM) of solid biological materials has been documented for Lemna minor L. root tips. This discussion will be limited to a demonstration of LTXM for measuring relative elemental distributions of P,S,Cl and K species within whole cells of tobacco leaves.Mature Wisconsin-38 tobacco was grown in the greenhouse at the University of California, Berkeley and picked daily from the mid-stalk position (leaf #9). The tissue was excised from the right of the mid rib and rapidly frozen in liquid nitrogen slush. It was then placed into an Amray biochamber and maintained at 103K. Fracture faces of the tissue were prepared and carbon-coated in the biochamber. The prepared sample was transferred from the biochamber to the Amray 1000A SEM equipped with a cold stage to maintain low temperatures at 103K. Analyses were performed using a tungsten source with accelerating voltages of 17.5 to 20 KV and beam currents from 1-2nA.

Bulk standards for low-temperature biological x-ray microanalysis

1984 ◽  
Vol 42 ◽  
pp. 282-283
Author(s):  
P. Echlin ◽  
M. McKoon ◽  
E.S. Taylor ◽  
C.E. Thomas ◽  
K.L. Maloney ◽  
...  
Keyword(s):  
Phase Separation ◽  
Low Temperature ◽  
Analytical Method ◽  
Salt Solutions ◽  
Absolute Concentration ◽  
Cooling Process ◽  
X Ray ◽  
The Absolute ◽  
Analytical Procedures ◽  
Electrical Conductors

Although sections of frozen salt solutions have been used as standards for x-ray microanalysis, such solutions are less useful when analysed in the bulk form. They are poor thermal and electrical conductors and severe phase separation occurs during the cooling process. Following a suggestion by Whitecross et al we have made up a series of salt solutions containing a small amount of graphite to improve the sample conductivity. In addition, we have incorporated a polymer to ensure the formation of microcrystalline ice and a consequent homogenity of salt dispersion within the frozen matrix. The mixtures have been used to standardize the analytical procedures applied to frozen hydrated bulk specimens based on the peak/background analytical method and to measure the absolute concentration of elements in developing roots.

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