bluuebunny/crossref_metadata_2025 huggingface dataset:
The crystal structure of fedotovite, K2Cu3O(SO4)3
Authors: Starova G. L. , Filatov S. K. , Fundamensky V. S. , Vergasova L. P.
Published: December 2006

The crystal structure of fedotovite, K2Cu3O(SO4)3 has been determined, space group C2/c, a 19.037(6), b 9.479(2), c 14.231(5) Å, β 111.04(3)°, Z = 8, Dx = 3.09 g/cm3. The main units of the fedotovite structure are formed around two additional oxygen atoms and consist of edge-sharing [OCu4] tetrahedra and four [SO4] tetrahedra attached to them. The units are further connected by two [SO4] tetrahedra, building distinct layers parallel to the yz plane. These layers are interconnected by potassium atoms. In the fedotovite structure, the three kinds of copper atoms are fivefold (4 + 1) coordinated to oxygen atoms with a strong Jahn-Teller effect. The coordination polyhedra of Cu1 and Cu2 atoms are distorted and flattened orthorhombic pyramids with Cu-O distances varying from 1.912 to 2.333 Å, the sixth neighbour of the both atoms is the copper atom lying at 2.975 and 2.981 Å for Cu2 and Cu1 respectively. The coordination environment of the Cu3 atom is a distorted elongated orthorhombic pyramid with four Cu-O distances from 1.943 to 1.961 Å, a fifth at 2.558 Å, and further sixth and seventh neighbours (oxygen and copper atoms) at 2.809 and 2.806 Å, respectively.
Mineral chemistry and paragenesis of astrophyllite from Egypt
Authors: Abdel-Rahman Abdel-Fattah M.
Published: December 2006

Astrophyllite is a rock-forming mineral (3.4 vol.%) in the metasomatized wallrocks within 2 to 3 km of the contact with the Mount Gharib A-type complex in northeastern Egypt. In the peralkaline A-type granites of the main complex, astrophyllite occurs in accessory amounts (0.1 to 0.5 vol.%), mostly in association with arfvedsonite. Eighteen chemical analyses of astrophyllite from both rock units have been used to discuss mineral chemistry, compositional variations and isomorphism.

Substitutions in the astrophyllite unit cell [(Na,K)3Fe7Ti2Si8(O,OH)31] involve F, Ca, Mn, Zn, Mg, Nb, Zr, Sn and A1. The contents of the unit cell depart from ideal stiochiometry. Unusually high Nb contents (up to 5 wt.% Nb2O5) characterize the Egyptian astrophyllitcs. The replacement of Ti by Nb is balanced by cation vacancies (Nb5+→ Ti4++ □). The niobophyllite-astrophyllite relationship and the structure of astrophyllite in relation to mica and biopyriboles are discussed.

Astrophyllite may have been formed at the expense of alkali amphiboles by metasomatic reactions involving Ti-Nb-rich alkaline fluids and arfvedsonite;

Most astrophyllite reported in the literature occurs in association with alkali amphiboles, particularly arfvedsonite, thus suggesting that similar metasomatic reactions were responsible for the formation of astrophyllite in many other localities in the world.
Petrology of the nyböite-bearing eclogite in the Donghai area, Jiangsu Province, eastern China
Authors: Hirajima T. , Zhang R. , Li J. , Cong B.
Published: December 2006

Nyböite occurs as porphyroblasts in the Jianchang eclogite in the Donghai area, northeastern Jiangsu Province, eastern China. The Jianchang eclogite contains some inclusions of quartz after coesite in clinopyroxene, garnet and epidote. It has colourless to pale-violet pleochroism. A thin rim with violet pleochroism often develops around nyb6ite and is taramitic. It is further retrogressed by the symplectite which is mainly composed of hornblende, aegirine-augite and albite. Nyböite is associated with jadeitic pyroxene in the Jianchang eclogite, although other porphyroblastic amphiboles in other Donghai eclogites are barroisitic to katophoritic and are associated with omphacite.

Fe-Mg partitioning between garnet and clinopyroxene and the presence of coesite pseudomorphs indicate P-T conditions in the Jianchang eclogite of about 740 ± 60°C and more than 28 kbar. Similar P-T conditions were estimated for other porphyroblastic amphibole-bearing eclogites in the Donghai area. Nyböite can occur in the Na-Al-Fe-rich local bulk composition under the medium to high temperature and very high-pressure conditions. Retrograde rim amphibole is poorer in NaB, variable in Si content, and richer in NaA variable than the porphyroblastic amphibole in the Donghai area. This roughly implies a P-T path where P decreases without a large decrease of T.
A new occurrence of vesigniéite from the Gorob-Hope copper deposit, Namibia
Authors: Schneider G. I. C. , Lauenstein H.-J.
Published: December 2006

An iron-rich vesigniéite, [Ba(Cu,Fe)3(VO4)2(OH)2] with Cu : Fe near 4 : 1, was identified in samples from the submarine-exhalative Gorob-Hope copper deposit, Namibia. The olive-colour mineral occurs as mammillary encrustations and vein fillings in the gossan zone of this deposit; it often has a brownish oxidation coating. The main X-ray lines are 3.21 Å (100) [204, 113], 2.72 Å (63) [313,002] and 2.94 Å (61) [020, 311]. The cell parameters are a = 10.236, b = 5.905, c = 14.253 Å and B = 103.71°. The formation of vesigniéite took place during the alteration of the ore under strongly alkaline and slightly reducing to oxidizing conditions. While copper and barium were derived from the submarine exhalative mineralisation, vanadium was leached from the countryrock, a micea schist.
Petrogenetic implications of garnets associated with lithium pegmatites from SE Ireland
Authors: Whitworth Martin P.
Published: December 2006

Spodumene pegmatites, aplites and schists from the Aclare Li prospect of SE Ireland host sporadically developed, small, red, euhedral garnets. Chemical data indicate that the pegmatite- and aplite-hosted garnets are rich in spessartine and are similar to garnets in many African Li-rich pegmatites. Partial melting as a source of the garnets is unlikely due to the large spessartine component, the abundance of inclusions within the garnets and the generalP-T-Xevolution of the pegmatite body. It is suggested that an aqueous fluid was exsolved during pegmatite crystallisation and complexed available Mn. Movement of this fluid to the intermediate zone of the pegmatite body produced areas of high Mn concentrations which permitted the crystallisation of spessartine-rich garnets at low pressures (<3 kbar).
Reflected-light microscopy of uraniferous bitumens
Authors: Eakin P. A. , Gize A. P.
Published: December 2006

Uraniferous bitumens from Great Britain, Scandinavia and South Africa have been studied by oilimmersion reflected-light microscopy and categorised into those formed either by replacement of preexisting uraninite and pitchblende or by complexation/reduction mechanisms in pre-existing hydrocarbons. The former are characterised by displaying normal replacive textures, and containing high concentrations of non-mineral-bound uranium, or later, occasionally exotic, uraniferous fracturefilling phases. Uraniferous bitumens formed during complexation/reduction reactions display monotonous mineralogies and ordered mineral-inclusion distributions.

Radiolytic alteration of uraniferous bitumens induces both chemical and mechanical alteration. Early alteration is marked by the generation of mobile hydrocarbons during 'cracking reactions' with subsequent within-sample migration to form globular bitumens and dendritic interspersions of mineralrich and -poor uraniferous bitumen. Mobile hydrocarbons may act as lubricants during mechanical deformation. Advanced organic alteration is characterised by well-documented increased reflectance around uraniferous grains, and by fracturing of the bitumens.
The Tregonning granite: petrogenesis of Li-mica granites in the Cornubian batholith
Authors: Stone Maurice
Published: December 2006

Li-mica (zinnwaldite and/or lepidolite)—topaz—albite granites in the Tregonning—Godolphin pluton and similar rocks in the St. Austell pluton appear to be petrogenetically unrelated to the spatially associated biotite granites. Evidence is provided by lack of development of Li-mica granites at roof zones of biotite granites and markedly different trends and composition fields in bivariate plots such as Li vs. Cs, Rb vs. Sr and Nb vs. Zr. Thus, differentiation of biotite granite magma is unlikely to have generated Li-mica granite magma, as also, on its own, is partial melting of biotite granite or biotiteabsent residual lower crust. However, partial melting of biotite-rich residual rocks involving biotite breakdown could yield a trace alkali- and F-enriched melt, although this would require marked femic mineral, K-feldspar and anorthite fractionation, and Na-enrichment. It is proposed that volatiles derwed from either a mantle source or the crust/mantle interface have aided metasomatism of either residual S-type crust that earlier provided S-type biotite granite magma, or basic (biotite-rich) granitoid, to produce a low-temperature, low-viscosity Li-mica granite melt that rose rapidly in the crust soon after the emplacement of associated biotite granites.
Thiosulphates as precursors of banded sphalerite and pyrite at Bleiberg, Austria
Authors: Kucha H. , Stumpfl E. F.
Published: December 2006

Banded sphalerite from Bleiberg, Austria, contains ubiquitous relics of Fe-thiosulphates and Fesulphites up to 50 μm in size. Zn, Pb, Ni and As form admixtures ranging from a few to 12 wt.% in these compounds. It is suggested that banded sphalerite is formed by a replacement of banded thiosulphate and thiosulphite precursors. This suggestion is supported by a significant admixture of Fe 0.41-8.20 wt.%) and the presence of goethite inclusions in banded sphalerite. In contrast, crystalline ZnS intergrown with the banded variety is Ni-free and contains only 0.06-0.14 wt.% Fe.

Banded pyrite contains inclusions of Fe-thiosulphate up to 200 μm in size. These thiosulphates contain (wt.%): 0.09-1.92 Zn, and 2.67−4.02 Pb. Pyrite formed by replacement (breakdown) of Fethiosulphate precursors contains 3.69-3.83 wt.% Pb.

It is suggested that banded sulphides precipitate from solutions carrying sulphur with mixed valances, and crystalline sulphides grow from solutions where the dominant dissolved sulphur is in the form of sulphidic anions.
Maghemite in Icelandic basalts
Authors: Steinthorsson S. , Helgason Ö. , Madsen M. B. , Bender Koch C. , Bentzon M. D. , Mørup S.
Published: December 2006

Curie temperatures indicating non-titaniferous magnetite are common in Icelandic basalts of all ages, especially Tertiary ones. Yet, microprobe analyses of such samples have shown high titanium in the magnetite. To resolve this paradox, and the mechanism at work, the magnetic mineral fraction of eight basalt samples with Js-T curves characteristic for pure magnetite was subjected to a multi-disciplinary analysis including Mössbauer spectroscopy and X-ray diffraction. In most of the samples titanium in the magnetite, as analysed with the microprobe, ranged between 16 and 28 wt.%, indicating submicroscopic solvus exsolution in the titanomagnetite, beyond the power of resolution for the microprobe. More unexpectedly in view of the reversible Js-T curves, Mössbauer spectroscopy showed appreciable proportion of maghemite in the magnetic fraction. A three-stage mechanism is proposed for the formation of the mineral assemblages observed: (1) limited high-temperature oxyexsolution; (2) solvus exsolution during low-temperature hydrothermal alteration; and (3) maghemitization of the magnetite. Finally, the maghemite may transform to hematite with time. It is concluded that maghemite is much more common in Icelandic rocks than hitherto believed.
The zinc analogue of schulenbergite, from Ramsbeck, Germany
Authors: Livingstone A. , Jackson B. , Davidson P. J.
Published: December 2006

A blue-green scaly coating on a slaty specimen from the Bastenberg mine, near Ramsbeck, Germany, yielded an X-ray powder pattern akin to schulenbergite. Chemically it is the zinc analogue of schulenbergite. Electron-probe data, XRF and ICP/OES analyses are presented which demonstrate two distinct zinc-rich compositions. Thermogravimetric analysis, together with CHN results, suggest the phase may contain 3-4 water molecules. Powder data are indexed on a hexagonal cell with a 8.293(2) Å, c 7.247(4) Å and cell volume 431.6(2) Å3, with Z = 1.
Vitusite — an apatite derivative structure
Authors: Finch Adrian A. , Fletcher James G.
Published: December 2006

The uncommon sodium rare-earth phosphate mineral vitusite-(Ce) (Na3RE(PO4)2) can be considered as the extreme product of sodium and rare-earth substitution in the apatite structure. Lesser amounts of substitution provide sodium and rare-earth-bearing apatites up to about 80 mol.% exchange; beyond this point vitusite is the stable phase. The structure of vitusite, determined previously from a synthetic analogue, can also be considered as a derivative from apatite, but with cations exchanged on sites normally occupied by anions. Vitusite can therefore be considered as a sodium- and rare-earthrich apatite end-member, with a distinct, but apatite-derived, structure, formed in highly persodic and high rare-earth environments. From an examination of the literature on diffusion in apatite, vitusite in principle could be formed from apatite sensu stricto by subsolidus diffusion in response to late-stage Naand RE-rich hydrothermal fluids.
Layered rhyolite bands in a thick North Mountain Basalt flow: the products of silicate liquid immiscibility?
Authors: Greenough John D. , Dostal J.
Published: December 2006

The upper 35 m of a thick (≤175 m) Early Jurassic North Mountain Basalt flow at KcKay Head contains 25 cm thick differentiated layers that are separated by 130 cm sections of basalt. The lower layers are mafic, pegmatitic, and contain thin (2 cm), fine-grained 'rhyolite' bands. Evidence that the rhyolite represents a Si-rich immiscible liquid includes: (1) textures such as fiine-grained globules of Ferich pyroxene (once Fe-rich liquid) bordering pegmatite feldspar grains; (2) structureless, microcrystalline, interstitial, polygonal patches of Si-rich minerals and similar areas of Fe-rich stilpnomelane surrounding skeletal Fe-Ti oxide grains, with bulk chemical compositions (to a first approximation), relative proportions and total modat percentages suggesting they were once Si-rich and Fe-rich glasses respectively; (3) basalt and pegmatite compositions (particularly their Fe, and Ti contents) similar to rocks known to contain immiscible liquids; (4) rhyolite major element compositions generally consistent with formation from an immiscible Si-rich liquid; (5) mineral compositions and temperature of pegmatite formation compatible with immiscibility; (6) the inability of mass balance calculations (crystal fractionation) to explain rhyolite formation unless mesostasis stilpnomelane (representing the Fe-rich liquid) is included in the caculations. If, as we suggest, these rocks are the result of immiscibility, they shed light on the incipient formation of granophyres in mafic intrusions and support liquid immiscibility as an important rock-forming process.
Composition of fluids in quartz: discrimination of magma pulses in a Caledonian granitoid
Authors: Batchelor R. A. , Armstrong D. C. , McDonald M.
Published: December 2006

Fluids trapped inside fluid inclusions in quartz from the multiphase Starav monzogranite in Etive, Argyll, were extracted under vacuum and quantitative data for H2O and CO2 were obtained manometrically. Na and K were determined on an aqueous leach from the decrepitated grains. A bivariate diagram of H2O/CO2 versus Na/K discriminates between magma pulses and mirrors the whole-rock trace-element chemistry. This work shows that compositional variations of fluids in quartz from a weakly mineralised granitoid intrusion are sensitive indicators of its magmatic history and identify subtle changes in its mineralogical composition.
The stabilities of antlefite and Cu3SO4(OH)4.2H2O: their formation and relationships to other copper(II) sulfate minerals
Authors: Pollard A. M. , Thomas R. G. , Williams P. A.
Published: December 2006

The stabilities of antierite, Cu3SO4(OH)4, and a synthetic compound whose stoichiometry is here established as Cu3SO4(OH)4.2H2O, have been determined at 5°C intervals between 10°C and 45°C using solution methods. The results of the experiments show that antlerite is stable with respect to the compound Cu3SO4(OH)4.2H2O only at temperatures above 30°C Below 30°C a change in the relative stabilities of these two basic copper(II) sulfates occurs, and the compound Cu3SO4(OH)4.2H2O, although unknown at present as a mineral, instead, is stable. Under these conditions, it does not react to give antlerite if kept in contact with water. Once isolated from its mother liquor, however, the dihydrate undergoes rapid dehydration to yield antlerite. Thermodynamic quantities for the two phases have been derived from equilibrium measurements. At 298.2K, values of AfG° for the compounds Cu3SO4(OH)4.2H2O(s ) and antlerite are −1919.6(14) and −1445.0(10) kJ mol−1, respectively. The results have been used to construct stability field diagrams for the system CuO—H2O–SO3 at 25°C and at 35°C These diagrams have been used to illustrate the chemical conditions under which the two compounds might be expected to form in the oxidised zones of cupriferous base metal orebodies.
The crystal structure of russellite; a re-determination using neutron powder diffraction of synthetic Bi2WO6
Authors: Knight Kevin S.
Published: December 2006

The crystal structure of the displacive ferroelectric mineral russellite, Bi2WO6, has been determined using Rietveld profile refinement of high-resolution, time of flight, neutron powder diffraction data on the synthetic compound. Russellite is orthorhombic, Pca21, with a 5.43726(2) Å, b 16.43018(5) Å, c 5.458422) Å, Z = 4 and is isostructural with the bismuth molybdate mineral koechlinite, Bi2MoO6. The structure consists of layers of tilted WO6 octahedra sandwiched between layers of bismuth and oxygen with the tungsten displaced from the centre of the octahedron by 0.278 Å. The orientations of the lone-pair electrons in the Bi3+ cations have been inferred from the 3.0 Å coordination shells of both crystallographically independent bismuths, and have been found to be non-centrosymmetric, an effect which may give rise to the tilting of the WO6 octahedra. New laboratory source X-ray powder diffraction data are presented for russellite, which, with supplementary synchrotron powder diffractometry, corroborate the new space group and structure determination.
The crystal structure of klyuchevskite, K3Cu3(Fe,Al)O2(SO4)4, a new mineral from Kamchatka volcanic sublimates
Authors: Gorskaya M. G. , Filatov S. K. , Rozhdestvenskaya I. V. , Vergasova L. P.
Published: December 2006

The crystal structure of klyuchevskite, K3Cu3(Fe,Al)O2(SO4)4, was determined in space group I2 using the total of 715 independent reflections up to R 0.12. Klyuchevskite is a structural analogue of piypite (caratiite) K4Cu4O2(SO4)4MeCl with the substitution K+ + Cu2+ → (Fe3+,Al) + MeCl. Compared to piypite, the ordering of Cu2+ and Fe3+ cations in the klyuchevskite structure results in the distortion of the unit cell and in lowering the symmetry of the chains to 1.

This brings about a more compact packing of the chains. The chain-like arrangement of the structure determines physical properties of the mineral, its acicular habit, perfect cleavage, strong anisotropy of optical properties and orientation of optical indicatrix.
Geochemical characteristics and petrogenesis of the main granitic intrusions of Greece: an application of trace element discrimination diagrams
Authors: Baltatzis E. , Esson J. , Mitropoulos P.
Published: December 2006

Geochemical investigation of samples from 20 granitic intrusions in six tectonic zones of the Hellenides shows that both I-type and S-type granites occur in the region. The I-type granites from four of the zones, namely the Rhodope Massif (RM), the Serbomacedonian Massif (SMM), the Perirhodope Zone (PRZ) and the Attico-cycladic Zone (ACZ), show some systematic differences in their geochemistry. In particular, the Rb, Y, Nb, K and Ti contents increase in the sequence PRZ, SMM, RM and ACZ. The PRZ granites are of Jurassic age, those of the SMM and RM are Eocene to Oligocene and the ACZ ones are Miocene. The differences between zones are attributed to a combination of differences in partial melting and high-pressure fractionation processes. Geochemical differences within zones are explained by variable degrees of amphibole and apatite fractionation and accumulation.
Supergene gold mineralogy at Ashanti, Ghana: Implications for the supergene behaviour of gold
Authors: Bowell R. J.
Published: December 2006

At the Ashanti concession, Ghana, gold-bearing quartz veins and disseminated sulphide lodes occur in narrow (1-3 m) shear zones with altered argillites and metatholeiite host rocks. The mineralisation is concealed by up to 10 m of kaolinite-mica forest ochrosol soils, beneath which is a saprolitic zone of leached rock extending down 60-70 m to the hypogene ore zone. In the unweathered hypogene orebody, gold occurs as free grains in quartz, as sub-microscopic inclusions in the disseminated arsenopyrite, as gold tellurides and as aurostibite. The gold is released from the hypogene orebody by physical dissaggregation and chemical dissolution, the latter involving hydroxyl, thiosulphate, cyanide, and fulvate complexing. Dissolution and reprecipitation of the gold appears to have taken place largely in situ with little evidence of supergene enrichment. Consequently, the gold mineralogy of the soils is complex with residual and secondary gold grains exhibiting widely different textural and compositional characteristics. Residually enriched grains display pitted, rounded surfaces and have silver-depleted rims, while supergene gold grains are compositionally homogenous and have unpitted surfaces. The supergene grains display platelet, dendritic, irregular and octahedral habit. A fine grained spongy form of gold has also been observed from weathered telluride-bearing quartz veins. Much of the secondary gold is intergrown with iron oxides and hydroxides. The gold mineralogy of the Ashanti soils appears to be controlled by physico-chemical processes active during the lateritic pedogenesis producing residual and supergene enrichment of gold.
Compositional variation in chromite from the Eastern Desert, Egypt
Authors: Khudeir Ali A. , El Haddad Mervet A. , Leake Bernard E.
Published: December 2006

Electron microprobe analyses of chromite ores from Baramiya, Seifein, Siwigat, Ashayer, Um Salatit and Ras Shait, Egypt, reveal two compositional groups. The unaltered chromites from Baramiya and Seifein have high Al and low Cr contents [Cr/(Cr + Al) = 0.56] whereas the remainder have low Al and high Cr contents [Cr/(Cr + Al) = 0.73]. Such bimodality characterises Alpine-type peridotites. The second group probably crystallised at higher T and lower P than the first group and has a composition characteristic of a type III alpine-type peridotite, i.e. of arc or possibly ocean plateau origin but not of mid-ocean ridge origin. The crystallisation setting of the first group is less certain but not inconsistent with the same environment as the second group so that considering the likely higher pressure of crystallisation of the first group overall favours plutonic crystallisation in the roots of an arc for both groups.

Rim, patchy and fracture alteration of the chromite occurred possibly partly of late magmatic (deuteric) origin but mainly connected with fluid movements, serpentinisation and tectonism. The final composition of the resultant ferritchromite is variable and depends largely on the original chromite composition; the composition of the ferritchromite developed in highly cataclased chromites deviates markedly from that of the original chromite presumably due to unmixing and migration.
Ontogeny of baryte crystals grown in a porous medium
Authors: Prieto Manuel , Putnis Andrew , Arribas Jose , Fernandez-Diaz Lurdes
Published: December 2006

The development of the morphology of baryte crystals grown in a silica gel medium is related to the changes in supersaturation. Nucleation occurs when the supersaturation in the system exceeds a threshold value which depends on the supersaturation rate, i.e. the rate at which the supersaturation is changing at the nucleation site. During growth the supersaturation decreases, although a high level of supersaturation is maintained throughout. These experimental results compare well with the morphological development predicted from theoretical models based on the periodic bond chain theory. The ontogeny of natural harytes corresponds, in considerable detail, to the experimental observations made here and strongly suggests that similarly high supersaturations have prevailed in nature. This correspondence indicates that the technique of crystal growth in a porous silica gel medium provides a good experimental model of studying natural growth processes.
The metamorphism of pyrite and pyritic ores: an overview
Authors: Craig James R. , Vokes Frank M.
Published: December 2006

Pyrite, the most widespread and abundant of sulphide minerals in the Earth's surficial rocks, commonly constitutes the primary opaque phase in ore deposits. Consequently, an understanding of the behaviour of pyrite and its relationships with coexisting phases during the metamorphism of pyritebearing rocks is vital to the interpretation of their genesis and post-depositional history. Metamorphism is commonly responsible for the obliteration of primary textures but recent studies have shown that the refractory nature of pyrite allows it to preserve some pre-metamorphic textures. Pyrrhotite in pyritic ores has often been attributed to the breakdown of pyrite during metamorphism. It is now clear that pyrrhotite can be primary and that the presence of pyrrhotite with the pyrite provides a buffer that constrains sulphur activity during metamorphism. Pyrite-pyrrhotite ratios change during metamorphism as prograde heating results in sulphur release from pyrite to form pyrrhotite and as retrograde cooling permits re-growth of pyrite as the pyrrhotite releases sulphur. Retrograde growth of pyrite may encapsulate textures developed during earlier stages as well as preserve evidence of retrograde events. Sulphur isotope exchange of pyrite with pyrrhotite tends to homogenise phases during prograde periods but leaves signatures of increasingly heavy sulphur in the pyrite during retrograde periods.
Post-recrystallisation mobilisation phenomena in metamorphosed stratabound sulphide ores
Authors: Vokes F. M. , Craig J. R.
Published: December 2006

Metamorphosed stratabound iron- and base-metal sulphide deposits often exhibit microtextures in which fractures in cataclastically-deformed pyrite porphyroblasts are filled with matrix sulphides; chalcopyrite, sphalerite, pyrrhotite or galena. Discussions of such textures have mostly centred on whether solid-phase or fluid-phase mechanisms were responsible for the movement of the matrix sulphides.

The small Zn-Cu sulphide body at Gressli, in the central Norwegian Caledonides, shows these textural features to an extreme degree. Both chalcopyrite and sphalerite show heavy replacive relations to the cataclastically deformed metablastic pyrite, along fracture walls and grain boundaries. They also occur injected along the opened-up triple junctions of foam-textured pyrite. In addition, parts of the ore show patchy quartz with clear replacive relationship to all three sulphides, a feature not often reported from such ores. Such textures can be interpreted to support a mobilisation sequence chalcopyrite-sphalerite-quartz within the Gressli ore. Their extent and degree of development indicate that fluid-phase mobilisation of the three minerals must have played a dominant role. Chalcopyrite and sphalerite are most likely derived from within the ore-mass itself; an external source for the SiO2 seems most probable, in the form of metahydrothermal solutions moving along retrograde shear zones at or near ore-walls.
Preferred orientation of experimentally deformed Mt Isa chalcopyrite ore
Authors: Jansen E. M. , Siemes H. , Merz P. , Schäfer W. , Will G. , Dahms M.
Published: December 2006

Chalcopyrite samples from Mt Isa, Australia have been experimentally shortened by up to 30% at temperatures up to 450°C at a constant confining pressure of 300 (400) MPa, and different strain rates in the range from 10-5 to 10-8 sec-1. After deformation, the X-ray pole figures show a maximum of (220/204) perpendicular to the compression axis for each of the samples, which has already been described for room temperature experiments by Lang (1968). The overlapping pseudocubic peaks of chalcopyrite can be separated into true tetragonal peaks by neutron diffraction texture analysis using a position sensitive detector combined with profile analysis (Will et al., 1989). The five investigated samples each show a combination of two or four main orientations of the crystallites, which represent neither a pseudocubic nor a tetragonal fibre texture.
Deformation and metamorphism of massive sulphides at Sulitjelma, Norway
Authors: Cook Nigel J. , Halls Christopher , Boyle Alan P.
Published: December 2006

The copper-bearing stratabound pyritic massive sulphide bodies contained in metamorphosed basic eruptives of Ordovician age at Sulitjelma in Nordland County, Norway, form one of the important fields of sulphide mineralisation within the Köli Nappe Complex. The sulphide bodies and their enclosing rocks were subject to successive stages of penetrative deformation and recrystallisation during the cycle of metamorphism and tectonic transport caused by the Scandian Orogeny. Textures within the ores and the immediate envelope of schists show that strain was focused along the mineralised horizons. The marked contrast in competence between the massive pyritic sulphides and their envelopes of alteration composed dominantly of phyllosilicates, and the metasediments of the overlying Furulund Group, led to the formation of macroscale fold and shear structures. On the mesoto microscale, a variety of textures have been formed within the pyrite-pyrrhotite-chalcopyrite-sphalerite sulphide rocks as a result of strain and recrystallisation. Variations in pyrite:pyrrhotite ratios and in the texture and proportions of associated gangue minerals evidently governed the strength and ductility of the sulphide rocks so that the same sulphide mineral can behave differently, displaying different textures in different matrices. In massive pyritic samples there is evidence of evolution towards textural equilibrium by recrystallisation, grain growth and annealment during the prograde part of the metamorphic cycle. Later, brittle deformation was superimposed on these early fabrics and the textural evidence is clearly preserved. By comparing published data on the brittle-ductile transformation boundaries of sulphide minerals with the conditions governing metamorphism at Sulitjelma, it is concluded that most of the brittle deformation in the sulphides took place during or after D3under retrograde greenschist conditions. Grain growth of pyrite in matrices of more ductile sulphides during the prograde and early retrograde stages of metamorphism produced the coarse metablastic textures for which Sulitjelma is well-known. In some zones of high resolved shear stress, pyrite shows ductile behaviour which could be explained by a dislocation flow mechanism operating at conditions close to the metamorphic peak. In those horizons in which pyrrhotite is the dominant iron sulphide, the contrast in ductility between silicates, pyrite and pyrrhotite has led to the development of spectacular tectonoclastic textures in which fragments of wall rock have been broken, deformed, rolled and rotated within the ductile pyrrhotite matrix.
EPMA, micro-PIXE, synchrotron microprobe and TEM study of visible and invisible accumulations of Au and PGE in black shale and organic matrix, Kupferschiefer, Poland
Authors: Kucha H. , Przyblowicz W. , Lankosz M. , Van Langevelde F. , Traxel K.
Published: December 2006

The Kupferschiefcr contains from 0.3 to 30 wt.% of organic matter, with an average value close to 10 wt.%. The concentration of heavy metals increases strongly towards the base of a black shale horizon. Where the black shale rests directly on red sandstone, the bottom few mm of the shale may contain (ppm): Hg 8-1500, mean 174; Ag 310-5780, mean 1222; Au 1-3000, mean 40; Pd 2-1000, mean 37; Pt 2-340, mean 18. The shale, enriched in noble metals, is overlain by thucholite shale. The flotation sulphide concentrate contains 1-3 ppm Au and a detectable Pd and Pt content. Selected gravity concentrates from the black shale contain 4-56 ppm Au, up to 25 ppm Pd, while the Pt content does not exceed 1 ppm. A tightly intermixed clay-organic matrix of the noble metal-bearing shale contains small accumulations of Au, Pt and Pd presumably as organomctallic compounds.

Thucholite is present locally. It contains inclusions of uraninite, brannerite and noble metal minerals lcoated at the boundary between optically isotropic and anisotropic components. The optically homogeneous organic matrix of the thucholite contains discrete inclusions of UO2, brannerite, electrum and organic compounds of Au, U, Pt and Ni varying in size from 0.008 to 0.025 μm as shown by TEM. Gold occurs in a continuous Au-Ag series. Refractory Au is present as substitutions in native silver and in the organic matrix of the shale and thucholite. Palladium forms several arsenides and sulphoarsenides. Refractory Pd is present as substitutions in Ni-Co arsenides and in the organic matrix of the shale and thucholite. Platinum is present as substitutions in the organic matrix of the noblemetal- bearing shale and thucholite.

The average detection limits of micro-PIXE were 8-10 ppm, and those of the SXRFA from one to a few ppm. A major factor defining detection limits in the studied samples were minor uranium lines overlapping spectral lines of the studied elements.
A new occurrence of musgravite, a rare beryllium oxide, in the Caledonides of North-East Greenland
Authors: Chadwick B. , Friend C. R. L. , George M. C. , Perkins W. T.
Published: December 2006

Musgravite, Be(MgFeZn)2Al6O12, is associated with norbergite and minor chlorite in a Precambrian calcite marble within the gneissic basement in an internal part of the Caledonian mobile belt in Dove Bugt, North-East Greenland. It commonly occurs as vitreous black, idioblastic crystals (<7 mm in size) with combined rhombohedral and basal pinacoid forms. XRD data show that its space group is R3m and its unit cell dimensions are a 5.687 ± 0.002 Å and c 41.16 ± 0.02 Å. Electron microprobe and ICP-MS analyses have yielded BeO 5.51 wt.% and ranges in abundance (wt.%): Al2O368.74-70.63; Tot, Fe as FeO 6.76-7.89; MgO 12.17-13.98; and ZnO 3.22-4.47. ICP-MS analysis also revealed significant trace amounts of V 249 ppm, Cr 740 ppm and Ga 178 ppm. The crystallographic parameters and composition are broadly in accord with those of musgravite from the two other recorded occurrences, in Precambrian high-grade terrains in Australia and Antarctica, although mineral and rock associations in these localities differ from those in Dove Bugt. The source of beryllium in each of the musgravite occurrences is uncertain, although a metasomatic source related to granite emplacement is favoured for the occurrence in North-East Greenland.
Compositional zoning in Zn-chromites from the Cordillera Frontal Range, Argentina
Authors: Bjerg Ernesto A. , De Brodtkorb Milka K. , Stumpfl Eugen F.
Published: December 2006

Serpentinised ultramafic bodies containing zoned chromite grains occur in the Cordillera Frontal Range, western Argentina. Chromites show Zn-rich Al-chromite cores (4.04 wt.% ZnO) surrounded by ferritchromite rims (1.3 wt.% ZnO) and outer Cr-magnetite rims. In intensely altered chromites which are spatially related to sulphide mineralisation, the primary chromite cores have been replaced by Zn-rich ferritchromit (7 wt.% ZnO) and they are rimmed by Cr-magnetite. In the Al-chromites the mean [Cr/(Cr + Al] ratio is 0.53 and the [Mg/(Mg + Fe)] ratio is 0.53; they plot in the field of Alpinetype intrusions. Ferritchromit has a mean [Cr/(Cr + Al)] ratio of 0.93 and [Mg/(Mg + Fe)] ratio of 0.4. In Cr-magnetites the mean [Cr/(Cr + Al) is 0.98 and the [Mg/(Mg + Fe)] ratio is 0. Ferritchromit is always surrounded by a Cr-magnetite rim and it was formed as a reaction product owing to the irreversible dissolution of primary chromite cores. The dissolution of these cores provided the essential components for ferritchromit growth. Zn was introduced into the chromite cores and ferritchromit rims during the formation of the latter. Step-scan profiles have shown that the Zn content in the cores increases from the centre to their outer border, where they show the highest Zn values. It is suggested that Zn was introduced by the fluid phase involved in the alteration process that affected the cores and lead to the formation of the zoned chromite grains. This alteration process was also responsible for the changes in [Cr/(Cr + Al)] and [Mg/(Mg + Fe)] ratios.
Kinetic controls on the formation of metastable phases during the experimentally induced breakdown of chlorite
Authors: Waldron K. A. , Droop G. T. R. , Champness P. E.
Published: December 2006

The kinetics and reaction mechanisms of chlorite breakdown have been studied in a series of experiments at conditions similar to those achieved during contact metamorphism (T = 600-725°C P = 1 kbar). Cores of chlorite schist were used as starting material in order to simulate natural metamorphic systems and preserve reaction textures. Reaction products were analysed by electron microprobe, scanning- and transmission-electron microscopy (SEM, TEM). Although the texture of the original chlorite was preserved in experiments run below 680°C talc had replaced chlorite. Olivine and spinel formed along grain boundaries, indicating long-range diffusion of aluminium. Above 680°C the chlorite was replaced by patches of disordered, aluminous pyroxene. Olivine and spinel grew both within the pyroxene and along what are believed to be former chlorite grain-boundaries. Reactions relevant to the observed textures and assemblages are:

Thermodynamic calculations show that both of these reactions are metastable in the FeO-MgO-Al2O3-SiO2-H2O system in the P-T range of our experiments. In addition, previous experimental studies and our calculations indicate that the stable reaction is:

The absence of cordierite in the run products, and the formation of talc and orthopyroxene while thermodynamically metastable, show that the ease of nucleation of these phases controlled the reaction mechanisms in the early stages.
A metacolloidal dendrite-rich Bi-Ni-Co quartz vein, Pozoblanco, Spain
Authors: Oen I. S. , Kieft C.
Published: December 2006

A Bi-Ni-Co vein in the contact zone of a granite near Pozoblanco, Córdoba, Spain, shows a zoned structure with mm-thin quartz wall zones, up to 20 cm thick Bi-rich quartz zones, and a few cm thick quartz-bismuth transition zones grading into a central quartz vug zone. The Bi-rich zones show textures indicating a metacolloidal origin from a silica gel enriched in adsorbed Bi: (1) globular and chain aggregates of fine-granular allotriomorphic quartz represent morphological relics of a globulated silica gel; (2) quartz rosettes, chain rosettes and stringer-combs radiating from the quartz globules and chains represent crystallised silica gel matrix; (3) crack fillings of quartz, gersdorffite and platy bismuth dendrites represent precipitates of metal-saturated dilute hydrosols filling shrinkage cracks in the desiccating and crystallising gel; (4) quartz spherocrystals in rosettes and combs are clouded with colloidal particles inherited from the silica gel; (5) unsupported wall rock inclusions represent inclusions in a viscous silica gel precursor covering fissure walls. The thin wall zones are quartz fillings of cracks between shrinking gel and walls. The transition and vug zones are recrystallised colloidal silica crusts precipitated by fissure-filling rest-solutions. Tree-like bismuth-gersdorffite dendrites in the transition zones are precipitates of metal-rich solutions infiltrating from the Bi-rich zones into the recrystallising silica crusts. The pre-concentration of metals in silica gels explains the dendrite formation without assuming abnormally high metal concentrations in transporting solutions or long range diffusion processes.
Barian mica and distribution of barium in metacherts and quartzofeldspathic schists, Southern Alps, New Zealand
Authors: Grapes Rodney H.
Published: December 2006

Zoned barian muscovite (2.52-5.66% BaO) and unzoned biotite (0.99-1.77% BaO) occur in two amphibolite grade metacherts of the Alpine schists, Southern Alps, New Zealand. The Ba-micas are associated with quartz-chlorite-Mn-garnet-tourmaline-apatite-sulphide ± oligoclase ± rutile ± magnetite ± ankerite. Increasing Ba (core to rim) in the muscovite is accompanied by a decrease in Si, Ti, Fe + Mg, and K and an increase in [4]Al, [6]Al, and Na. The main substitution that accounts for entry of Ba into both micas is [A]Ba2+ + [4]Al3+ ⇋ [A]K+ + [4]Si4+ and possibly [A]Ba2+ ⇋ [A]K+ + □. Compositional variation of the muscovite is also governed by the substitutions, [6]Al3+ + [4]Al3+ ⇋ [6](Mg,Fe)2+ + [4]si4+, and [A]Na+ ⇋ [A]K+. The presence or absence of oligoclase, rutile, magnetite and Mg/(Mg + Fe) ratio of coexisting biotite control the Na, Ti, Fe and Mg contents of muscovite in the respective metacherts. Important variables controlling the occurrence of Ba-mica is the Ba-rich composition of the metacherts (1387 and 2741 ppm Ba) and metamorphic grade. In metacherts, siliceous and quartzofeldspathic schists with <1000 ppm Ba barium increases with increasing K2O content indicating that in K-feldspar-absent rocks barium is mainly contained in micas (<0.70% BaO). In greenschist facies metacherts and siliceous schists with high Ba (>1000 ppm) and low K2O, barian micas are not present and most of the Ba occurs in baryte ± barian carbonate with implication of a significant original hydrothermal-hydrogenous input. Although low grade illite/sericite/smectites containing Ba are the most likely precursor of the barian micas in the metacherts, strong marginal Ba enrichment in the muscovite indicates a later Ba-metasomatism resulting from the breakdown of baryte under reducing conditions during amphibolite facies metamorphism.
A retrogressive sapphirine-cordierite-talc paragenesis in a spinel-orthopyroxenite from southern Karnataka, India
Authors: Friend C. R. L. , Janardhan A. S. , Shadakshara Swamy N.
Published: December 2006

Within amphibolite facies Peninsular gneisses in the south of the Dharwar craton, units of Sargur supracrustal rocks contain ultrabasic enclaves. One of these enclaves is an orthopyroxenite which comprises bronzite, spinel and minor phlogopite preserving coarse-grained, relic textures of probable igneous origin. After incorporation into the gneisses the enclave evolved through several distinct stages, elucidation of which allow an assessment of its metamorphic history.

Firstly, deformation during closed system, anhydrous recrystallisation caused the coarse-grained textures to be partially overprinted by similar mineral assemblages but with a granoblastic texture. Secondly, open system hydration caused retrogression of the bronzite to alumino-gedrite at the margins of the enclave. Subsequently, the penetration of these fluids along grain boundaries caused reactions between spinel and bronzite to produce reaction pockets carrying assemblages of peraluminous sapphirine associated with cordierite and talc. The differences in the mineral assemblages in each pocket coupled with slight variations in their chemistry, suggest that equilibrium did not develop over the outcrop. Because sapphirine + magnesite is present in some pockets, it is evident that CO2was also a component of the fluid.

Phase relations from the MASH portion of the FMASH system, to which the chemistry of the reaction pockets approximates, suggest that the hydrous metamorphism causing the changes depended upon the assemblage enstatite + spinel + vapour which exists atPTconditions above the position of I16, ∼760°C at 3 kbar and below I21at ∼765°C at 5.6 kbar (Seifert, 1974, 1975), where sapphirine is replaced by kornerupine. The suggested path of reaction occurred between I18and I21. Subsequent reactions related to I20cause the formation of cordierite. Talc formation has to be modelled in a different reaction grid.

The metamorphism recorded by these reactions is thus at a maximum of amphibolite facies and is interpreted to have formed during the uplift and cooling history of the gneiss complex when hydrous fluids were free to migrate. Given the complex high-grade metamorphic history of this part of the Dharwar craton this event is likely to be late Archaean or Palaeoproterozoic in age.
Ferrian high sanidine in a lamproite from Cancarix, Spain
Authors: Linthout Kees , Lustenhouwer Wim J.
Published: December 2006

Na-poor, Fe-bearing high sanidine from a lamproite near Cancarix (Spain) has 2Vα‖(010) = 37-43° and C2/m, a = 8.598(15), b = 13.050(26), c = 7.209(17) Å, β = 116.00(18)° V = 727(2) Å3. Rims of sanidine crystals against vugs contain up to 60 mole % KFeSi3O8 and up to 10 at.% Si and 6 at.% K above the stoichiometric requirement; otherwise, they have up to 4 mole % □Si4O8 and 3 mole % K2O.Si4O8 in solid solution. Their MgO content may reach 0.46 wt.%. The skeletons of mm sized blocky crystals (Baveno habit) indicate formation under moderate undercooling at temperatures not much above 725°C Feldspar formation was facilitated by a high diffusion rate due to low viscosity in a highly perpotassic melt, supersaturated by pressure release and diopside fractionation, upon extrusion of a huge volume of lava in a crater. After titanian potassium-richterite largely filled the interstices in the sanidine fabric, crystals of dalyite (K2ZrSi6O15) and Fe-rich rims of sanidine and amphibole crystals were formed from an increasingly hydrous, silicic, ferric, and peralkaline residual melt. High rate nonequilibrium crystallisation caused the incorporation of excess SiO2 and K2O in the defect structure of the sanidine. Retrograde boiling initiated the escape of volatiles, causing the quenching, by which the disordered structural state and the nonstoichiometric composition of the sanidine were preserved.
New structural and spectroscopic data for eosphorite
Authors: Hoyos M. A. , Calderon T. , Vergara I. , Garcia-Solé J.
Published: December 2006

X-ray diffraction refinement of the crystal structure of eosphorite has been carried out with reference to the orthorhombic space group Cmca. The structure is similar to that previously described by Hanson (1960), but the standard deviations are improved. Optical absorption and photoluminescence have also been studied for this mineral. Two sharp emission lines, denoted as R1 and R2, superimposed to a broad band (630-750 nm) have been related to the presence of Cr3+ ions. The excitation spectrum of these emissions confirms that the absorption (excitation) bands centred at 431 nm and 585 are related to with 4A2 → 4T1 and 4A2 → 4T2 spin allowed transitions of this ion.
A corresponding states equation and compensation effects in crystal growth rates
Authors: Dearnley R.
Published: December 2006

Interpretation of grain size measurements in terms of the kinetics of grain growth depends on the ability to define the temperature variation of mineral growth rates. An outline is presented of the application to mineral growth rates of a corresponding states equation (CSE), which provides a relationship of growth rate to a reduced temperature function. Additionally, growth rates exhibit a 'compensation effect' between the pre-exponential constant and the activation energy in the standard Arrhenius equation, analogous to that shown by diffusion data. The general systematics of activation energy, equilibrium temperature and growth rate maxima are controlled by the relationships of the CSE, the standard Arrhenius equation and the compensation effect, and on this basis the temperature variation of growth rate between the equilibrium and the glass temperature may he estimated.