bluuebunny/crossref_metadata_2025_split huggingface dataset:
Petrography, mineralogy and diagenesis of overpressured Tertiary and Late Cretaceous mudrocks from the East Shetland Basin
Authors: Huggett J. M. 
Published: November 2006

AbstractThe petrography, mineralogy and diagenesis of an overpressured Tertiary and Late Cretaceous mudrock sequence from a single well in the East Shetland Basin (North Sea) are described. The clay fraction is believed to be dominated by volcanic glass above 1400 m depth and by smectite below 1400 m. The smectite content increases with depth due to an increase in detrital smectite and toin situalteration of volcanic glass and grains; this commenced almost immediately after deposition and is still not complete at burial depths >2300 m. There is little evidence of alteration of the smectite to illite despite a local available supply of K+in the form of K-feldspar and the presence of K in the more deeply buried smectite. Very little leaching or precipitation of quartz has occurred. Microfossil tests filled with authigenic clays such as have been reported in other Tertiary mudrocks in the North Sea were not observed, though a few fossil cavities are filled with carbonate cements, and very rarely with microquartz. The suprisingly limited reactivity of this mudrock sequence may be due to the early development of overpressure, resulting in a “closed” system, and to the absence of interbedded higher permeability layers or open faults through which fluids could be exchanged.
Crystal chemistry and significance of cation ordering in Mg-Al rich spinels from high-grade hornfels (Predazzo-Monzoni, NE Italy)
Authors: Princivalle F. , Della Giusta A. , De Min A , Piccirillo E. M. 
Published: November 2006

AbstractTwo Mg-Al spinels (FAS1 and FAS2) in high-grade hornfels from the Toal de Mason skarn (Predazzo Monzoni, NE Italy) were investigated by means of single crystal X-ray diffraction and electron microprobe analysis in order to evaluate the last intra-crystalline closure temperature.The evidence provided by crystal chemical data from the investigated spinels, compared with that for two other spinels from a websterite dyke and a chlorite schist (TS2 and SP78a, respectively) with similar chemical characteristics, yielded a new empirical geothermometer. This allowed estimation of intra-crystalline temperatures as low as c. 400°C and indicates that the closure temperature of FAS1 and FAS2 is c. 500°C i.e. 150–200°C lower than the spinel crystallisation temperature.
Nomenclature of the micas
Authors: Rieder M. , Cavazzini G. , D’yakonov Yu. S. , Frank-Kamenetskii V. A. , Gottardi G. , Guggenheim S. , Koval’ P. V. , Müller G. , Neiva A. M. R. , Radoslovich E. W. , Robert J.-L. , Sassi F. P. , Takeda H. , Weiss Z. , Wones D. R. 
Published: November 2006

AbstractEnd-members and species defined with permissible ranges of composition are presented for the true micas, the brittle micas, and the interlayer-deficient micas. The determination of the crystallochemical formula for different available chemical data is outlined, and a system of modifiers and suffixes is given to allow the expression of unusual chemical substitutions or polytypic stacking arrangements. Tables of mica synonyms, varieties, ill-defined materials, and a list of names formerly or erroneously used for micas are presented. The Mica Subcommittee was appointed by the Commission on New Minerals and Mineral Names of the International Mineralogical Association. The definitions and recommendations presented were approved by the Commission.
Raman spectra of synthetic ‘braggite’, (Pd,Pt,Ni)S
Authors: Merkle R. K. W. , Pikl R. , Verryn S. M. C. , De Waal D. 
Published: November 2006

Abstract
Raman spectra of synthetic ‘braggite’ ((Pd,Pt,Ni)S) vary systematically with
changes in Pt/Pd ratios, but this change is less pronounced than in ‘cooperite’
((Pt,Pd,Ni)S). Compared to ‘vysotskite’ (ideally PdS), the incorporation of Pt
leads to broadening of bands but the spectra of ‘vysotskite’ and ‘braggite’ are
similar, and spectra of ‘cooperite’ and the ‘braggite/vysotskite’ solid-solution
series are sufficiently different to facilitate distinction of these platinum
group minerals by Raman spectroscopy.
Ag-Cu exchange equilibria between α-miargyrite, chalcostibite, pyrargyrite,
and high-skinnerite: constraints on Ag-Cu mixing in α-miargyrite and
chalcostibite
Authors: Harlov D. E. 
Published: November 2006

Abstract
Ag-Cu exchange equilibria between α-miargyrite AgSbS2
and pyrargyrite Ag3SbS3 and between
chalcostibite CuSbS2 and both pyrargyrite and high-skinnerite
Cu3SbS3 are reported for the
temperature range 150–350°C. All of these features are constrained by Ag-Cu
exchange experiments (evacuated silica tubes; variable mass ratio) over the
temperature range 120–400°C. Chalcostibite is found to take very little Ag into
its structure. Utilizing Ag-Cu data from this study as well as the Ag-Cu solution
models for pyrargyrite and high-skinnerite, a two-site Ag-Cu non-convergent
ordered solution model for α-miargyrite () and a one-site Ag-Cu mixing model
for chalcostibite ( = 25.0 kJ/gfw) are formulated.
These results are constrained by a miscibility gap between α-miargyrite and
chalcostibite from 225 to 325°C. The mixing model for α-miargyrite is expanded to
include As for which α-miargyrite has a limited solubility along the Sb-As join
with smithite AgAsS2.
The nature and significance of sulphate-rich, aluminous efflorescences from
the Te Kopia geothermal field, Taupo Volcanic Zone, New Zealand
Authors: Martin R. , Rodgers K. A. , Browne P. R. L. 
Published: November 2006

Abstract
Alunogen and meta-alunogen are the dominant phases present in transient
sulphate efflorescences that are the latest products of the alteration of
ignimbrite country rocks in the long-lived Te Kopia geothermal field.
Meta-alunogen pseudomorphs alunogen and both species occur as white, fibrous,
tangled masses, as prismatic, parallel growths, and as thin, platy, crystals, 8–15
μm across, that coalesce in an open cellular network. Small (<2 mm diam.)
spherical aggregates of radiating, acicular halotrichite
(Fe0.51Mg0.49Al2(SO4)4.22H2O),
potash alum, mirabilite, melanterite and tschermigite are present locally. The
cations needed to form these minerals derive from the host rocks with the
exception of sulphur and ammonia that come from H2S and
NH3 gases ascending with steam. The particular
efflorescence assemblage reflects the prevailing conditions and ionic activities
of a local micro-environment. Kaolinite formed by acid sulphate alteration is now
being altered by steam to yield alunogen. In turn, alunogen can react with silica,
or co-dissociate with silicic acid, to form kaolinite. The alternating dissolution
and reprecipitation of kaolinite and alunogen moves aluminium in and through the
surficial environment at Te Kopia.
Empirical calibration of the sulphur valence oxygen barometer from natural and
experimental glasses: method and applications
Authors: Matthews S. J. , Moncrieff D. H. S. , Carroll M. R. 
Published: November 2006

Abstract
New data on sulphur valence and magmatic oxidation state for Central Andean
volcanic rocks, in combination with published data for experimental and natural
samples, allow derivation of a simple relationship between magma oxidation state
and sulphur speciation. For a number of highly oxidized Central Andean volcanic
rocks fO2 has
been calculated using magnetite-ilmenite or olivine-spinel pairs and the sulphur
valence in glasses has been measured using the peak shift of S-Kα radiation
relative to a pyrite standard. Previously published experimental and natural data
have been incorporated with a wider range in
fO2 and
S valence. The variation in sulphur speciation (as S2- or
SO42-) as a function of log
fO2 is
described by an empirical polynomial fit which reproduces the data to within ±0.5
log units and allows use of electron microprobe measurements of the
S-Kα wavelength shift for estimation of magmatic
oxygen fugacities. This approach is applicable for
fO2
between FMQ-2 and FMQ+6, encompassing most terrestrial magmas. The method has been
used to calculate the in
fO2
conditions under which melt inclusions were trapped in andesitic magmas before
magma mixing in two Central Andean volcanoes, and to calculate the oxygen fugacity
of a slowly-cooled pyroclastic flow in which the Fe-Ti oxide phases have
subsequently re-equilibrated. In combination with Fe-Ti oxide data, two distinct
trends emerge for Lascar volcano. Basaltic andesite-andesitic magma chambers
follow T-fO2
trends which parallel the FMQ buffer curve, indicating ferrous-ferric iron
buffering of oxygen fugacity. Dacitic anhydrite-bearing magmas with admixed
basaltic andesite and andesite follow trends of increasing
fO2 with
decreasing temperature, indicative of buffering of
fO2 by
SO2-H2S in a co-magmatic gas phase.
This trend continues into the metamorphic aureole of the magma chamber, resulting
in highly oxidized (close to magnetite-hematite) conditions.
Surface oxidation studies of chalcopyrite and pyrite by glancing-angle X-ray
absorption spectroscopy (REFLEXAFS)
Authors: England K. E. R. , Charnock J. M. , Pattrick R. A. D. , Vaughan D. J. 
Published: November 2006

Abstract
The oxidation of chalcopyrite and pyrite was examined using
Fe-K- and Cu-K-edge
REFLEXAFS spectroscopy. The Fe XANES of the pyrite proved to be a very sensitive
indicator of oxidation, revealing the development of a goethite-like surface
species; the EXAFS data showed an increasing O:S ratio with the degree of
oxidation and gave Fe–O distances of c. 1.9 Å. On the
oxidized chalcopyrite surfaces, the development of Fe-O and Cu-O species was
observed, with both the XANES and EXAFS revealing the progressive development of
these species with oxidation. Differences in the sensitivity of the XANES and
EXAFS to the degree of oxidation can be related to the degree of long range order
and changes in the intensity of the pre-edge feature of the Fe are a function of
its oxidation state and coordination geometry in the surface species.
Fresh and weathered pyrochlore studies by Fourier transform infrared
spectroscopy coupled with thermal analysis
Authors: Nasraoui M. , Bilal E. , Gibert R. 
Published: November 2006

Abstract
Fresh and weathered pyrochlore from the Lueshe carbonatite complex (in the
northeast of the Democratic Republic of Congo) was studied by Fourier transfom
infrared (FTIR) spectroscopy and by a combination of FTIR spectroscopy and thermal
analysis. The former was carried out in the spectral range 400–4000
cm−1. The spectra for fresh and weathered pyrochlores were
very different. For the weathered pyrochlore, two bands were identified as OH
vibration modes, one broad band with a maximum at 3413 cm−1
and another finer band at 1630 cm−1. The fresh pyrochlore
does not show OH absorption bands. The presence of OH confirms the hydrated state
of the weathered pyrochlore suggested by previous microanalytical work. The
combination of FTIR spectroscopy and thermal analysis allows ‘real-time’
observation of gas emanations and solid-state transformations taking place during
heating up to 800°C. For fresh pyrochlore, no solid transformation was detected,
except a CO2 emanation from 242–576°C. For the weathered
pyrochlore a dehydration was observed between 234–565°C followed by an exothermic
peak in Differential Scanning Calorimetric (DSC) curve at 604°C. This exothermic
peak corresponds to the formation of a Nb oxide phase. At higher temperatures the
weathered pyrochlore is partly decomposed, forming a dehydrated pyrochlore and a
Nb oxide phase. The combination of FTIR and thermal analysis has provided useful
information on both fresh and weathered pyrochlore transformations which has
clarified our understanding of the water control of the structural stability of
pyrochlore minerals.
Monazite-(Ce)-huttonite solid solutions in granulite-facies metabasites from
the Ivrea-Verbano Zone, Italy
Authors: Förster H.-J. , Harlov D. E. 
Published: November 2006

Abstract
Composite populations of monazite-group minerals of both metamorphic and
metasomatic origin have been discovered in thin layers of granulite-facies
metabasites interlayered with metapelites, located in the Val Strona di Omegna
region of the Ivrea-Verbano Zone, Italy. In addition to monazite-(Ce), which is
uncommonly poor in Th and is probably formed by incongruent dissolution of
apatite, these populations include members of the monazite-huttonite series. The
latter minerals contain between 13 and 30.1 mol.% ThSiO4 [=
huttonitic monazite-(Ce)], and are known from only half a dozen other occurrences
worldwide. We propose that breakdown of primary monazite-(Ce) in the metapelites
during granulite-facies metamorphism mobilized Th and the
REEs, which were then transported by high-grade
metamorphic fluids into the metabasite layers to form the Th-rich minerals of the
monazite-huttonite series.
Magmatic gold grains in the El Tale lamproite, Fortuna, SE Spain
Authors: Toscani L. 
Published: November 2006

Abstract
Gold of magmatic origin has been discovered in the lamproitic dyke of El Tale
(Fortuna, Province of Murcia), a small outcrop of ultrapotassic rocks of tile
Tertiary magmatic province of southeastern Spain. It is the first finding of gold
grains in lamproite magmas from southeastern Spain, and indeed worldwide. Pure
gold occurs only in the glassy groundmass as very rare spherules and globular
grains (up to 5 µm). Despite the occurrence of gold grains, the bulk rock contains
not more than ∼19 ppb Au.
The magmatic origin of gold is inferred from the heterogeneous distribution
of the grains in the rock, the shape of the grains (which is comparable to that of
gold grains crystallized experimentally from mafic liquids) and from the
As-Sb-S-Cl-poor composition of the bulk rock. The Pd/Ir and Au/Pd ratios, little
affected by the early segregation of olivine (∼10 vol.%), support an Au- and
PGE-rich composition of the mantle source. The low
fO2
(≈IW) and the complexing with F and alkalies probably favoured partitioning of Au
and PGE into the lamproite magma.
Oscillatory zoned chrome lawsonite in the Tavşanlı Zone, northwest
Turkey
Authors: Sherlock S. C. , Okay A. I. 
Published: November 2006

Abstract
Blueschist-facies metabasite rocks from the Tavşanlı Zone of northwest Turkey
have been found to contain an abundance of lawsonite displaying oscillatory
zoning. Lawsonite normally adheres to the ideal composition of
CaAl2[Si2O7](OH)2.H2O.
In two samples from the Tavşanlı Zone,
Al3+-Cr3+ substitution has occurred.
The Cr3+ was probably present in the protolith as magmatic
chromite, became incorporated into lawsonite during subduction, and is a
metamorphic feature resulting from quantities of Cr in the protolith and local
fluid conditions.
The infrared absorption band at 3596 cm−1 of the recrystallized
quartz from Mt. Takamiyama, southwest Japan
Authors: Niimi N. , Aikawa N. , Shinoda K. 
Published: November 2006

Abstract
Micro-FTIR (MFTIR) measurements were carried out on the natural
recrystallized quartz in Ryoke granites from Mt. Takamiyama. The recrystallized
quartz always shows a very strong IR absorption band at 3596
cm–1 (2.10 abs. cm–1 (normalized
absorbance) under unpolarized conditions at room temperature). However, naturally
deformed quartz does not show this absorption band, but only a characteristic
broad band centred at 3400 cm–1. This shows that the
predominant forms of H-related species in the recrystallized quartz are different
from those in naturally deformed quartz. The 3596 cm–1 band
is not affected by room-temperature X-ray irradiation or by annealing at
temperatures of up to 600°C, and shows broadening and a positive peak shift with
temperature in in situ high temperature measurements.
Polarized-MFTIR measurement shows that the band has a strong polarization; the OH
dipole is oriented at 35° to the a-axis in the
plane and is isotropically
distributed in the (0001) plane. From the stability of the band at high
temperatures and against irradiation and its sharpness, the band is considered to
be due to the Al(H) type point defect with no alkali which might occupy a
structural position in the quartz structure.
Petrology and geochemistry of xenoliths in lamprophyres from the Deccan Traps: implications for the nature of the deep crust boundary in western India
Authors: Dessai A. G. , Vaselli O. 
Published: November 2006

AbstractAlkaline lamprophyre intrusives from the western Deccan Traps (Murud-Janjira, south of Bombay) host rare lithospheric xenoliths and megacrysts. The xenolith suite consists of clinopyroxenites and granulites which show eclogitic affinities. The former have transitional (porphyroclastic to equigranular) textures whereas the latter are porphyroclastic, xenomorphic to meta-igneous. The textural features provide evidence of ductile-brittle deformation. The protoliths of the pyroxenite and granulite xenoliths were formed as cumulates of alkaline and sub-alkaline magmas respectively.Mineral chemistry and geochemical data for the xenoliths bear testimony to the metasomatized nature of the deep crust. The xenolith data coupled with the geophysical evidence indicate that the lower crust beneath Murud-Janjira is dominated by mafic granulites and pyroxenites. The latter have under- and intra-plated the continental crust beneath the region.
Bi-Sb energetics in sulfosalts and sulfides
Authors: Ghosal S. , Sack R. O. 
Published: November 2006

Abstract
Experimental brackets (300–450°C) on Sb-Bi partitioning between
stibnite-bismuthinites (Sb,Bi)2S3 and
sulfosalts in the AgSbS2–AgBiS2 binary
subsystem (α-Ag(Sb,Bi)S2,
β-Ag5(Sb,Bi)4I(Sb,Bi)IIS10)
and extant constraints are used to define mixing properties and standard state
Gibbs energies of Sb-Bi exchange reactions. They are also used to construct a
phase diagram for Ag(Sb,Bi)S2 sulfosalts. We infer that the
non-ideality associated with Sb-Bi mixing is largest in minerals of the
β-Ag5(Sb,Bi)4I(Sb,Bi)IIS10
series, and is sufficient to produce miscibility gaps between an ordered
intermediate species
Ag5(Sb)4I(Bi)IIS10
and Sb- and Bi-end-members at T < 240°C (measured in
terms of symmetric regular-solution-type parameters
¼WBi−SbIβ =
WBi−SbIIβ ∼ 8.5 kJ/gfw). The
non-ideality associated with the Sb-Bi substitution in stibnite-bismuthinite and
α-Ag(Sb,Bi)S2 is ≈ 70% that in the
Ag5(Sb,Bi)4I(Sb,Bi)IIS10
series (WBi−SbBS ≈ 12.0 kJ/gfw;
WBi−Sbα ≈ 6.0 kJ/gfw). It is
insufficient to produce exsolution at temperatures of ore deposition
(T >
Tc ≈ 88°C), but most likely is
responsible for a preponderance in molar Sb/Bi ratios towards end-member
compositions. Finally, positive Gibbs energies of the Sb-Bi exchange reactions and
indicate that Bi is more
compatible in stibnite-bismuthinite sulfides than in
Ag(Sb,Bi)S2 sulfosalts.
Zn-spinel in the metamorphosed Zn-Pb-Cu sulphide deposit at Mamandur, southern
India
Authors: Chattopadhyay P. K. 
Published: November 2006

Abstract
At Mamandur, southern India, zincian spinel is associated with Zn-Pb-Cu
sulphide ores, metamorphosed to the granulite facies. The Zn-spinel
(XZn = 0.44–0.82) occurs in assemblages of: (a) cordierite
+ biotite + sillimanite + sphalerite + pyrite and/or pyrrhotite; (b) garnet +
biotite + sphalerite + pyrite and/or pyrrhotite; (c) hornblende + biotite +
sphalerite + pyrite and/or pyrrhotite; and (d) it also occurs in highly sheared
quartz veins with sphalerite + pyrite/pyrrhotite. Two texturally and
compositionally distinct modes of occurrence of Zn-spinel have been recorded from
the metamorphic assemblages: one shows a polygonal, granular (equilibrium) fabric
with Zn-spinel grains in textural equilibrium with cordierite in the granulite
facies assemblage; the other which is involved in the formation of coronas in
garnet- and hornblende-bearing assemblage of a younger paragenesis (presumably
belonging to a late retrograde stage), shows distinct compositional zoning with
depletion of Zn and enrichment in Fe and Mg from the rim inwards. A third mode of
occurrence is as perfectly euhedral grains embedded in a quartzose matrix in
quartz veins, often with sphalerite moulded over the Zn-spinel grains.
From textural evidence and consideration of stoichiometric balance, Zn-spinel
occurring in association with cordierite is suggested to have formed by the
prograde reactions: 0.46 biotite (Mg-rich) + 1.80 sillimanite + 3.01 quartz + 0.11
sphalerite = cordierite + 0.20 Zn-spinel + 0.80 K-feldspar + 0.06 pyrite + 4(OH,F)
or 0.48 biotite (Mg-rich) + 2.08 sillimanite + 2.72 quartz + 0.26 sphalerite =
cordierite + 0.50 Zn-spinel + 0.83 K-feldspar + 0.13 S2 +
4(OH,F) and, the Zn-spinels occurring in association with garnet and hornblende by
the retrograde reactions: garnet + 4.53
Al2SiO5 + 4.17 sphalerite = 5.38 Zn
(-Fe)-spinel + 0.22 Ca-feldspar + 0.92 pyrite + 7.06 quartz + 1.23
S2 and hornblende + 26.93
Al2SiO5 + 20.17 sphalerite + 0.88
pyrite = 25.93 Zn-spinel + 2 Ca-feldspar + 56.81 quartz + 11.32
S2 + 2(OH,F) Zn-spinel in the sheared quartz vein may be
of (meta-) hydrothermal origin. Formation of sphalerite through sulphurization of
gahnite is ruled out on the evidence of the perfectly euhedral nature of the
spinel and the absence of any breakdown product from the spinel.
Sideronatrite and metasideronatrite efflorescence formed in a coastal
sea-spray environment
Authors: Garvie L. A. J. 
Published: November 2006

Abstract
Sideronatrite
[Na2Fe(SO4)2(OH)·3H2O]
occurs as yellow botryoidal encrustations on low cliffs of weathered
pyrite-bearing mudstones at Barton-on-Sea, Hampshire, England. Extensive areas of
the cliffs, up to ∼100 m2, are coated with sideronatrite and
its low solubility in cold water secures its longevity. Dry samples of
sideronatrite convert readily to metasideronatrite
[Na2Fe(SO4)2(OH)·H2O],
the reaction to sideronatrite being reversible. Sideronatrite, it is suggested,
forms as a result of weathering of pyrite that is present in the argillaceous
sediments and reaction with Na from the sea-salt spray.
EXAFS of copper in hydrosulfide solutions at very low concentrations:
implications for the speciation of copper in natural waters
Authors: Mosselmans J. F. W. , Pattrick R. A. D. , Charnock J. M. , Solé V. A. 
Published: November 2006

Abstract
Cu K-edge extended X-ray absorption fine structure (EXAFS) spectra have been
obtained for two very dilute solutions of copper in hydrosulfide solutions using
beamline ID26 at the ESRF. The concentrations of the solutions (4.4 ppm {69 µM} pH
9.5, 1.2 ppm {19 µM} pH 7.4) are such that the experiments illustrate that, with
the advent of third generation synchrotron sources, natural systems can now be
studied by EXAFS. Analysis of the data indicates an average environment for the
copper of 2.3 S atoms at 2.22 Å in the pH 9.5 solution of 2.5 S atoms at 2.23 Å in
the pH 7.4 solution. These results are in accord with the solubility study of
Mountain and Seward (1999), who conclude that
Cu(HS)2− and
Cu2(HS)2S2− are
the principal copper species in such solutions.
Crystal structure of barstowite (3PbCl2·PbCO3·H2O)
Authors: Steele I. M. , Pluth J. J. , Stanley C. J. 
Published: November 2006

AbstractThe crystal structure of barstowite (3PbCl2·PbCO3·H2O,P21/m,a= 4.2023(5),b= 9.2020(7),c= 16.6608(6)(Å), β = 91.829(9)°) from Bounds Cliff, St Endellion, Cornwall, has been determined to an R = 0.036. The structure can be described in terms of three layers stacked along [001] in the sequence …CACBCACBC… to give a 16.7 Å repeat. Layer A consists of face-sharing PbCl8distorted square antiprisms. Layer B is composed of Pb coordinated to 5 Cl and 2 O each with two H to form H2O groups. Layer C is formed by Pb coordinated to 5 Cl and 3 O which are from CO3groups. The H positions are deduced and are H-bonded to O from carbonates. The structural details were in agreement with previous deductions based on infrared spectra.