Remnants of early Archaean (Akilia) iron-formation occur as enclaves within the c. 3700 Ma Amitsoq gneisses in the eastern Godthåb-Sukkertoppen region of southern West Greenland. Amphibole- and pyroxene-bearing assemblages are preserved respectively in these two areas. The amphibole-facies rocks comprise one, two, and three-amphibole-bearing assemblages, coexisting with magnetite and quartz (and locally garnet). Experimentally determined phase equilibria suggest that the amphibole-bearing types have not exceeded c. 700 °C, while distribution coefficients in the two-pyroxene ironformation indicate a maximum temperature of around 625 °C.

Mg-Fe distribution relationships between the phases are:

and

where the numbers are generalized distribution coefficients and in phase a). Mn distribution is:

and

The distribution coefficients are variable both from one rock to another and internally from one set of grain pairs to another. The development of the observed variable silicate phase assemblages is dependent upon a complex interaction of not only metamorphic grade (P and T) and element availability, but more importantly aH2o and fo2. In particular, the possibility of reactions between observed assemblages containing cummingtonite + actinolite, magnesian actinotite + magnetite and ferrohypersthene+ferrosalite suggest lesser or greater degrees of dehydration under oxidizing or reducing conditions. For example:

and

A local area of the Kap Edvard Holm Upper Layered Series gabbro has been converted into a quartz-albite-epidote ilmenite rock by leaching of iron and with a net mass loss. Among the textural changes is the dissolution of the magnetite matrix of magnetite-ilmenite lamellar intergrowths. This is an extreme example of a series of low-temperature changes occurring throughout the intrusion due to the reaction of the gabbro with a volatile-rich phase which separated during the magmatic stage and remained trapped within the walls of the intrusion. The Fe-rich fluid formed by this autometasomatic process is similar to those responsible for the genesis of Cornwall-type magnetite deposits. The probable temperature range for the process is 400–550°C.

Hylbrownite, ideally Na3MgP3O10·12H2O, the second known triphosphate mineral, is a new mineral species from the Dome Rock mine, Boolcoomatta Reserve, Olary Province, South Australia, Australia. The mineral forms aggregates and sprays of crystals up to 0.5 mm across with individual crystals up to 0.12 mm in length and 0.02 mm in width. Crystals are thin prismatic to acicular in habit and are elongate along [001]. Forms observed are {010}, {100}, {001}, {210} and {201}. Crystals are colourless to white, possess a white streak, are transparent, brittle, have a vitreous lustre and are nonfluorescent. The measured density is 1.81(4) g cm−3; Mohs' hardness was not determined. Cleavage is good parallel to {001} and to {100} and the fracture is uneven. Hylbrownite crystals are nonpleochroic, biaxial (−), with α = 1.390(4), β = 1.421(4), γ = 1.446(4) and 2Vcalc. = 82.2°. Hylbrownite is monoclinic, space group P21/n, with a = 14.722(3), b = 9.240(2), c = 15.052(3) Å, β = 90.01(3)°, V = 2047.5(7) Å3, (single-crystal data) and Z = 4. The strongest lines in the powder X-ray diffraction pattern are [d (Å)(I)(hkl)]: 10.530(60)(10,101), 7.357(80)(200), 6.951(100)(11, 111), 4.754(35)(10, 103), 3.934(40)(022), 3.510(45)(30, 303), 3.336(35)(41, 411). Chemical analysis by electron microprobe gave Na2O 16.08, MgO 7.08, CaO 0.43, P2O5 37.60, H2Ocalc 38.45, total 99.64 wt.%. The empirical formula, calculated on the basis of 22 oxygen atoms is Na2.93Mg0.99Ca0.04P2.99O9.97·12.03H2O. The crystal structure was solved from single-crystal X-ray diffraction data using synchrotron radiation (T = 123 K) and refined to R1 = 4.50% on the basis of 2417 observed reflections with F0 > 4 σ(F0). [Mg(H2O)3P3O10] clusters link in the b direction to Naφ6 octahedra, by face and corner sharing. Edge sharing Naφ6 Octahedra and Naφ7 polyhedra form Na2O9 groups which link via corners to form chains along the b direction. Chains link to [Mg(H2O)3P3O10] clusters via corner-sharing in the c direction and form a thick sheet parallel to (100). Sheets are linked in the a direction via hydrogen bonds.

We review some of the most recent developments in classical and quantum mechanical molecular dynamics simulations, in particular as applied to Earth-forming phases at conditions prevalent in the Earth's deep interior. We pay special attention to the modelling of high pressures and temperatures, elucidating the problems associated with both the classical and quantum approaches in view of the empirical potentials required for the former, and the limitations of finite temperature calculations for the latter. We show the current status of such calculations for major phases such as MgSiO3 perovskite.

Luetheite was found at a small prospect in Santa Cruz County, Arizona, as crystals in vugs in rhyolite porphyry. A few specimens were found on the dump, none seen in place. Occurs in silicified porphyry (quartzsericite-alunite) with chenevixite and hematite. Crystals indian blue inclining to greenish, H = 3, Dmeas = 4·28.

Crystals monoclinic 2/m and tabular on a {100}, also a plane of distinct cleavage; other forms are {110}, {140}, {011}. Space group perhaps P21/m with a = 14·743Å, b = 5·093, c = 5·598, β = 101° 49′; strongest lines are 3·498Å (10), 310, 111; 7·208 (7), 200; 2·507 (5), 120, 510. Feebly pleochroic in pale blue in thin section, γ = β > α. Indices are α = 1·752, β = 1·773, γ = 1·796; 2Vγ = 88° (calc.); dispersion is moderate ν > ρ. α ∥ [010], γ: [001] 10° in obtuse β. Duplicate chemical analyses averaged CuO 28·9%, Al2O3 18·4%, As2O5 40·5%, H2O 9·3% giving 2[Cu2Al2 (AsO4)2(OH)4·H2O].

Named for R. D. Luethe, geologist for Phelps Dodge Corporation. Chenevixite from Las Animas, Sonora, analysed to give Cu2Fe2(AsO4)2(OH)4·H2O. Powder data are close to luetheite, and the cell is monoclinic 2/m, probably P21/m, with a = 15·006A, b = 5·189, c = 5·724, β = 102°15. The measured specific gravity is 4·38, Dcale. = 4·59. Crystals tabular on a {100} with a habit very similar to luetheite. Indices are α = 1·92 , β = 1·96, γ = 2·04, 2Vγcale. = 75°; α ∥ [100], γ nearly ∥ [001].

A crystal chemical study of narsarsukite from the Murun alkaline massif, Russia has been carried out combining single-crystal X-ray diffraction, electron microprobe analyses, micro-Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The narsarsukite single crystals are tetragonal (space group I4/m) with unit-cell parameters: 10.7140(1) ≤ a ≤ 10.7183(2) Å and 7.9478(1) ≤ c ≤ 7.9511(1) Å. The XPS analysis showed that Fe occurs in the mineral as Fe3+, whereas the FTIR spectrum showed that the sample studied is anhydrous. The average crystal chemical formula of the Murun narsarsukite is: Na2.04K0.01(V0.015+Ti0.74Zr0.01Al0.01Fe0.223+Mg0.01)1.00Si4.00(O10.74F0.23OH0.03)11.00. Structural disorder at octahedral and interstitial sites was modelled and also discussed in consideration of the main substitutional mechanism Ti4+ + O2– ↔ Fe3+ + (F–, OH–) active in the structure of the mineral.

The petrographical and chemical characteristics of the tourmalinite pebbles from the Lower Devonian conglomerates of Belgium are presented together with selected trace element data. The tourmalinites are shown to represent metasomatically altered rocks of variable origin and composition. A model of subvolcanic hydrothermal alteration is proposed.

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

The cooling rates during titanomagnetite exsolution of the Taberg, Skaergaard and part of the Mt. Yamaska intrusions were calculated to be approximately 130, 12 and 6000°C per 1000 years respectively. These values are in good agreement with cooling rates calculated from heat flow models of the intrusions.

Understanding the behaviour of gas in a geological disposal facility (GDF) is an essential component of analysing the facility evolution and long-term (post-closure) safety performance. This includes the impacts of gas on the physico-chemical evolution of the GDF, and the release and migration of radionuclides in water and gas.

The Nuclear Decommissioning Authority Radioactive Waste Management Directorate is participating in the EC FORGE (fate of repository gases) project (www.forgeproject.org) and conducting independent research. Key research themes are modelling the impacts of different host rocks on facility evolution including coupled processes, and upscaling the effects of small scale features that can significantly influence the evolution of the whole facility.

Recent code developments have enabled coupled processes to be represented more realistically in models. This has significantly advanced understanding of facility evolution, as discussed in this paper, and will improve future assessment models. There is potential to further improve approaches to upscaling the effects of small scale features on strongly coupled processes, within the context of the EC FORGE project.

It is now well established that naturally—occurring sulphides—particularly galena—are frequently found in the deformed state and that at least part of this deformation can be eliminated by annealing in the laboratory.

The present contribution is concerned principally with galena, for which it is indicated: that tectonic deformation leads to natural work hardening, which may be reduced by simple heating in vacuo; that the rate of softening is related to the annealing temperature; that softening is related to recovery at low temperatures and to both recovery and recrystallization above 250–300 °C that single crystals of galena exhibiting minor slip and kinking recrystallize yielding new, unstrained grains elongated parallel to the old slips and kinks, i.e. a foliation involving unstrained grains may form under a regime devoid of compressive stress; and that where deformed galena and deformed sphalerite coexist, the galena may be made to recrystallize completely (e.g. at 325 °C in 50 days) while leaving the deformation in the sphalerite entirely intact; apparently the coexistence of a strained component A and an unstrained component B in a deformed ore or other metamorphic rock does not necessarily indicate differences in age or deformational history—it may simply indicate that post-deformational temperatures have exceeded the recrystallization temperature of one component but not of the other.

Deposition of two anhydrous sulphate-carbonate minerals, burkeite and hanksite, around a vapour escape in the pipe of a geothermal well of the Copahue field in Argentina is described. These minerals usually occur as efflorescences in saline soils or in continental lacustrine evaporite deposits, but have not been reported as products from geothermal fluids. Both minerals have been studied by means of X-ray diffraction, scanning electron microscopy and electron dispersive energy, and thermo-gravimetric analysis, and have been determined as burkeite, Na6(CO3)(SO4)2, and hanksite, KNa22(SO4)9(CO3)2Cl.

Gold occurrences have been reported in the northeastern part of Goiás State since the beginning of the 18th Century. The main mineralization is associated with Paleoproterozoic peraluminous, syntectonic granites of the Aurumina Suite and associated metasedimentary,graphite-bearing country rocks of the Ticunzal Formation. In the Buraco do Ouro gold mine, the mineralization is hosted in muscovite-quartz mylonite in a silicified shear zone near the contact between biotite-muscovite granite and paragneiss of the Ticunzal Formation. The ore mineralogy consistsof gold, paraguanajuatite (Bi2Se3), kalungaite (PdAsSe), isomertieite [Pd11Sb2As2], mertieite II [Pd8(Sb,As)3], sperrylite (PtAs2), padmaite (PdBiSe), bohdanowiczite (AgBiSe2), clausthalite (PbSe),krutaite (CuSe2), ferroselite (FeSe2), uraninite (UO2) and unnamed Ag-Pb-Bi-Se minerals. Local magnetite concentrations and rare chalcopyrite and pyrite are also associated with both mineralized and barren mylonites in a gangue consisting of muscovite, quartzand rare tourmaline. High TiO2 muscovite clasts in the ore are interpreted as the magmatic muscovite of the original granite, and the mineralization is considered to be synchronous with the syntectonic granite intrusion during syn-emplacement shearing and alteration. The associationbetween granitic rocks and platinum-group element (PGE)-bearing gold mineralization observed in the Buraco do Ouro mine is uncommon and unique in the context of the Aurumina Suite and the Ticunzal Formation, where gold deposits and occurrences are gold-only. The chemical data suggest the possibilityof a solid solution between paraguanajuatite and bohdanowiczite. In addition, a complex intergrowth occurs between paraguanajuatite, clausthalite and Ag-Pb-Bi-Se phases, one of which, a Pb-Bi-Se phase could represent a new mineral. Uraninite is identified for the first time in this mineralassemblage and its concentration in the ore seems important, as revealed by high gamma spectrometric measurements in the samples collected in the mine. The association between gold and uranium constitutes a regional signature, observed in both gold and uranium deposits in the Cavalcante region.

Strontium-rich epidote, including epidote-(Sr) and epidote with major amounts of Sr (i.e. epidote containing up to 17.3 wt.% SrO), was found in pumpellyite schist and epidote blueschist in a tectonic block in the serpentinite mélange of the Kurosegawa Zone, central Kyushu, Japan. The tectonic block is 20 m wide and made primarily of lawsonite blueschist, with subordinate amounts of pumpellyite schist and epidote blueschist. The pumpellyite schist typically occurs at the edge of the block and is composed mainly of pumpellyite with subordinate amounts of strontium-poor epidote, albite and chlorite, and thin veins of fine-grained calcite and clinopyroxene. Epidote-(Sr) forms rims around strontium-poor epidote, fills fractures in strontium-poor epidote and also occurs interstitially between pumpellyite aggregates and along the boundaries between pumpellyite and calcite-clinopyroxene veins. The epidote blueschist is found between the pumpellyite schist and lawsonite blueschist, and consists mainly of sodic amphibole, epidote and titanite, with albite veining. Strontium-rich epidote occurs as rims, replacing Sr-poor epidote near the albite vein. The bulk strontium contents of the rocks are as follows: lawsonite blueschist (200 ppm), epidote blueschist (2800 ppm) and pumpellyite schist (~10,700 ppm). The chemical and petrological characteristics of the Sr-rich epidote-bearing metabasites suggest that the infiltration of a metamorphic fluid promoted extensive Sr metasomatism during the later stages of high-pressure metamorphism.

Yeomanite, Pb2O(OH)Cl, is a new Pb-oxychloride found in the manganese pod mineral assemblage at Merehead (Torr Works) Quarry, near Cranmore, Somerset, England. Yeomanite is named in joint recognition of Mrs Angela Yeoman (1931–) and her company, Foster Yeoman, who operated Merehead Quarry for aggregate until 2006. The mineral is normally white, occasionally grey, with a white streak and a vitreous to transparent lustre. Invariably intimately associated with mendipite, yeomanite appears to be formed of small, twisted, rope-like fibres growing from the end of columnar mendipite masses, forming loose mats and strands resembling asbestos. Individual fibres are generally <8 mm long, but exceptionally may reach up to 15 mm. There is a perfect cleavage parallel to the long axis of the fibres but this is masked by the fibrous nature, especially as individual fibres break easily. The Dcalc for the ideal formula is 7.303 g/cm3. The mean RI in air at 589 nm is 2.27. The eight strongest reflections in the powder X-ray diffraction pattern [(d in Å) (Intensity) (hkl)] are: 2.880(100)(113); 2.802(78)(006); 3.293(61)(200); 3.770(32)(011); 2.166(22)(206); 1.662(19)(119); 2.050(18)(303); 3.054(17)(105) Yeomanite is orthorhombic, Pnma, a = 6.585(10), b = 3.855(6), c = 17.26(1) Å, V = 438(1) Å3, Z = 4. Yeomanite is a new example of the growing family of lead oxychloride minerals that have a structure based upon oxocentred OPb4 tetrahedra, which, in this mineral, jointly with OHPb3 triangles, form [O(OH)Pb2]+ chains similar to those observed in synthetic Pb2O(OH)I. Yeomanite is structurally related to sidpietersite, penfieldite and laurionite.

The system Pd-Fe-Ni-S was studied at 900 and 725°C by means of dry condensed charges. At both temperatures it is dominated by the phase relationships involving sulphide melt. Pd-Fe-Ni alloys with broad miscibility primarily coexist with the melt; they are relatively enriched in Pd, whereas the associated melt is enriched in Ni. With decreasing temperature the melt recedes from Fe-rich regions. The incompatibility of PdS (extensive solid solution with Ni) and mss at 900°C is replaced by their co-crystallization (± disulphide(s) of Ni,Fe or ± sulphide melt) at 725°C The Ni/Fe ratio in the melt changes regularly against that in mss with increasing S fugacity and Pd contents in these two phases. (Ni,Fe)3±xS2 and Pd4S play important roles at 725°C. The data offer an array of distribution coefficients and solubility values suitable for geological interpretations.

Cordierite+orthoamphibole (Crd+Oam)-bearing gneisses in the Cormacks Lake complex are regionally associated with metapelites containing prismatic sillimanite and K-feldspar, metabasites that locally contain metamorphic orthopyroxene, and other high-grade rocks in the Central Gneiss (Dashwoods) subzone, in the southwestern Newfoundland Appalachians. Retrograde features formed at the expense of the granulite-facies assemblages are ubiquitous. For example, in some migmatitic rocks, garnet is resorbed by Crd+Oam, and in metapelites, cordierite separates corroded garnet and sillimanite. Mineral thermobarometry suggests that, following granulite-facies metamorphism (T<785°C, P<7.5 kbar), retrogression occurred as the Cormacks Lake gneisses cooled through Mg-Fe diffusional blocking temperatures as they decompressed to a pressure of ∼3–4 kbar. Given the absence of Barrovian (or higher pressure) mineral assemblages in the metapelites, regional tectonic reconstructions involving the thrusting of a neighbouring terrane (Notre Dame subzone) over the Central Gneiss subzone appear to be supported only by the moderate pressure determined for the granulite facies event. Although scarcely discernible given re-equilibration effects and the imprecision of thermobarometers, subsequent decompression nonetheless had a marked impact on the mineralogy of the gneisses.

The general formula of the amphiboles of this series may be written as NaxMg2(Mg(5-y)Aly,)(Si(8-z)Alz)O22(OH)2, where Mg = Mg + Fe2+ + Mn2+ and Al = Al + Fe3+ + Ti. The individual <T–O> distances are linear functions of their [4]Al content, and the [4]Al content is strongly ordered in the following way: T1B > T1A » T2B » T2A. The <M1-O>, <M2-O> and <M3–O> distances are linear functions of the mean ionic radius of their constituent cations. End-member compositions may be written as follows: A☐Mg2Mg5Si8O22(OH)2O22(OH)2; A☐Mg2(Mg3Al2)(Si6Al2)O22(OH)2; ANaMg2Mg5(Si7Al) These compositions define a plane in xyz space across which the data of Schindler et al. (2008), measured on amphiboles from amphibolites, follow a tightly constrained trajectory. Anthophyllite–gedrite amphiboles equilibrated under significantly different P-T conditions (e.g. igneous rocks, contact-metamorphic rocks) follow trends that diverge from this trajectory, with greater Na and [4]Al contents and relatively smaller [6]Al contents. Detailed examination of the local bond topology involving the A and M2 sites indicates that the maximum degree of bond-valence compensation will occur for incorporation of ANa and M2Al in the ratio 4:10, and hence 2.5 ANa = M2Al in these amphiboles. This relation closely fits the data of Schindler et al. (2008), suggesting that the variation in chemical composition in anthophyllite–gedrite amphiboles is strongly constrained by the anion bond-valence requirements of the Pnma amphibole structure. We further suggest that different compositional trends for ortho-amphiboles equilibrated under different P-T conditions are the result of the valence-sum rule operating with (different) bond-lengths characteristic of these P-T conditions.

Sugilite relatively rich in manganese has been found at two new localities, the Hoskins and Woods mines in New South Wales, Australia. The occurrences are in manganese-rich silicate rocks of middle to upper greenschist facies (Hoskins mine) and hornblende hornfels facies (Woods mine). Coexisting minerals are members of the namansilite-aegirine and pectolite-serandite series, Mn-rich alkali amphiboles, alkali feldspar, braunite, rhodonite, tephroite, albite, microcline, norrishite, witherite, manganoan calcite, quartz, and several unidentified minerals. Woods mine sugilite is colour-zoned with pale mauve cores and colourless rims, whereas Hoskins mine sugilite is only weakly colour-zoned and pink to mauve. Within single samples, the chemical compositions of sugilite from both localities show wide ranges in Al contents and less variable ranges of Fe and Mn, similar to trends in sugilite from other localities. The refractive indices and cell dimensions tend to show systematic increases progressing from Al-rich to Fe-Mn-rich. The formation of the sugilite is controlled by the high alkali (especially Li) and manganese contents of the country rock, reflected in the occurrences of coexisting high alkali- and manganese-bearing minerals, and by high fo2 conditions.