A series of titanium silicate glasses along the composition joins TiO2-SiO2, TiO2-Na2SiO3, TiO2-K2SiO3 and TiO2-CaSiO3, has been examined using oxygen K-edge X-ray absorption near edge structure spectroscopy (XANES) confined to the near-surface region. Sharp pre-edge features in the spectra can be used to determine the Ti coordination in the glasses. The presence of [4]Ti is indicated by a pre-edge peak at ∼534 eV while [5]Ti is indicated by a peak at ∼533 eV. Titanium exists in all these glasses as [4]Ti and [5]Ti with no [6]Ti being present. For alkali-containing glasses the [5]Ti site becomes more prevalent with increasing TiO2. TiO2-K2SiO3 compositions contain a greater proportion of [4]Ti than comparable Na2O compositions. This is consistent with earlier Ti L-edge findings. The TEY spectra for the TiO2-CaSiO3 compositions indicate the presence of significant amounts of [5]Ti at high TiO2 contents; however, comparison of TEY (near surface) and FY (bulk sample) XANES shows that the [5]Ti is confined to the surface of the glass sample with the bulk of the glass containing [4]Ti.

The Rocky Beach Metamorphic Melange contains metre-scale phacoids of high-P low-T metamorphic rocks embedded in chlorite-actinolite schist. The phacoids include eclogite, glaucophane schist and omphacitite and provide evidence for four episodes of metamorphism with mineral assemblages: M1 = actinolite-glaucophane-titanite-apaite, M2 = almandine-omphacite-lawsonite ±quartz, M3 = phengite- glaucophane-K-feldspar-quartz, and M4 = chlorite-actinolite-calcite-quartz-titanite-white mica ± albite ± talc. M1-M3 occurred at a Neoproterozoic-Early Palaeozoic convergent plate boundary close to the eastern margin of Gondwana. Peak metamorphic conditions were attained during the static phase M2, with temperatures of ~560°C and pressures in excess of 1.8 GPa, equivalent to a depth of burial of at least 54 km.

Blackhead Quarry exploits a small Miocene (~10 Ma) basanitic volcanic centre in the Dunedin Volcanic Group, New Zealand. Vesicles near the quarry top contain Ca– and Na-rich zeolites, abundant calcite and rare pyrite resulting from localized low-T hydrothermal alteration (<100°C). Mineral assemblages were characterized by EDS and laser Raman spectroscopy with the latter the most useful in determining the identity of fibrous zeolite species. Secondary mineral assemblages crystallized during final stages of lava cooling from aqueous solutions enriched in Ca, Na, K, Ba and (CO3)2–leached from surrounding calcareous rocks and basanite. Phillipsite-K (generation I) crystallized first (in some places directly on fresh basanite) followed by the Ca-rich zeolites, chabazite-Ca, calcian phillipsite–K (generation II), gismondine and thomsonite. Later Na-rich fluids crystallized gonnardite and natrolite, and finally calcite from late Ca-rich fluids. Zeolite composition is not reflected by morphology. For example, both phacolitic and pseudocubic chabazite are chabazite-Ca, and although all phillipsite crystals have a similar habit, their composition varies widely. Various lithologies comprising the Blackhead volcanic centre have unique secondary mineral paragenetic sequences controlled largely by the rock structure and solution chemistry.

Rhönite occurs in lower crustal pyroxenite xenoliths erupted in phonolite from the Mount Sidley composite volcano, Marie Byrd Land, Antarctica, as a localized breakdown product, with plagioclase, clinopyroxene, ± olivine ± Ti-magnetite + melt, of kaersutite, and as microphenocrysts (with olivine, plagioclase, clinopyroxene) in pockets of basanitic melt. Rhö nite after kaersutite has a more NaSi-rich/ CaAl-poor composition, lower Ti, and formed at higher oxidation (∼NNO) conditions than rhönite occurring as microphenocrysts in basanite. Comparison with experimentally determined rhönite stability in understaturated alkali basalt and as a reaction product after Ti-amphibole indicates that the Mount Sidley rhönite (and associated minerals) formed between 1090 and 1190°C at <0.5 kbar, presumably during temporary residence of the xenoliths in a shallow magma chamber below the volcanic edifice.

Backscattered electron imaging of cordierite-muscovite intergrowths near the margin of a schist xenolith in trachytic tephra of the Wehr Volcano, East Eifel area, Germany, show that they have undergone disequilibrium melting to form spinel + biotite + sillimanite/?mullite + peraluminous melt. Textures indicate that in the initial stage of reaction, spinel, biotite and sillimanite/?mullite formed with melt produced in cordierite and spinel + ?mullite with melt after muscovite, providing evidence of two different reaction pathways. Fe-Mg distributions between biotite/spinel, cordierite/spinel, cordierite/ biotite suggest a melting temperature of ∼770°C, implying overstepping of various calculated and experimentally determined mineral breakdown curves of between 30 and 170°C during short-term heating before the xenolith was quenched on eruption.

Adiabatic self-heating tests were carried out on five New Zealand coal samples ranging in rank from lignite to high-volatile bituminous. Kinetic parameters of oxidation were obtained from the self-heating curves assuming Arrhenius behaviour. The activation energy E (kJ mol–1) and the pre-exponential factor A (s–1) were determined in the temperature range of 70–140°C. The activation energy exhibited a definite rank relationship with a minimum E of 55 kJ mol–1 occurring at a Suggate rank of ∼6.2 corresponding to subbituminous C. Either side of this rank there was a noticeable increase in the activation energy indicating lower reactivity of the coal. A similar rank trend was also observed in the R70 self-heating rate index values that were taken from the initial portion of the self-heating curve from 40 to 70°C. From these results it is clear that the adiabatic method is capable of providing reliable kinetic parameters of coal oxidation.

A dolostone layer is found in spatial association with the Emirli epithermal Sb-Au deposit in western Turkey. It occurs within an argillic alteration zone adjacent to the major Emirli fault zone, which is the controlling structure for the deposit, and is composed of large closely packed subhedral to anhedral planar and nonplanar dolomites. Pyrite is the only accessory mineral in the layer and occurs as disseminations and veinlets up to 100 μm wide. Dolomite crystals are petrographically homogeneous and have consistent deep-red cathodoluminescence (CL) colour with no zoning which implies single-stage dolomitization of a calcitic precursor which is partly preserved as remnant patches of orange-coloured CL zones. Some crystal boundaries have dark (or no) CL colour. Electron microprobe line-scan analyses across these regions indicate intense enrichment of Fe and Mg depletion, revealing late-stage Fe-metasomatism (ankeritization) especially prevalent near pyrite veinlets and disseminations.

Dolomite crystals are composed of 52.4–55.0 mol.% CaCO3, 29.9 –41.2 mol.% MgCO3, 1.8 – 14.4 mol.% FeCO3 and 0.75 –3.2 mol.% MnCO3 indicating ferroan dolomite. The relationship between Ca and Mg is not stoichiometric due to substitution of Mg2+ by Fe2+ after dolomitization, as demonstrated by a strong negative correlation between Fe and Mg. Whole-rock Fe contents of the dolostone layer increases toward the Emirli fault zone.

The δ13C(PDB) compositions of the Emirli dolomite, calcitic marbles, and graphite-schists are in the ranges of –1.6 to 0.8‰, 1.5 to 1.5‰ and –6.6 to –23.5%, respectively, indicating that dolomite was formed due to interaction of light-carbon-enriched fluids with calcitic marbles; light-carbon may have been derived from decarboxylation of the graphitic schist layers. δ18O(PDB) values of dolomite and marble range –15.2 to – 11.2‰ and –2.4 to – 3.5‰, respectively. This large isotopic difference between dolomite and marble was probably inherited from oxygen isotope exchange between the dolomitizing fluid and the precursor calcites, as well as other minerals enriched in light-oxygen.

Fluid inclusions in dolomite are two-phase, and homogenize into liquid within the temperature interval 242 – 362ºC with a mode of 290ºC, and have salinities of 1 – 3 wt.% NaCl equiv. Using this modal temperature, the average δ18O(PDB) composition of water in isotopic equilibrium with the Emirli dolostone was estimated to be –19.4±2.1‰, which is interpreted as an indication of modified surface-waters; this interpretation is also supported by low fluid salinity and Na and Sr contents. These fluids migrated along graben-related faults, penetrating deeper levels where they were transformed into hydrothermal fluids due to the high heat-flow of the Küçük Menderes graben system, and flowed-up mainly through the Emirli and Haliköy faults that control mineralization in local deposits of Sb-Au and Hg, respectively. Due to interaction with chlorite-bearing graphite-schists, the fluid may have dissolved Mg2+ from chlorite and been enriched in isotopically-light carbon due to decarboxylation of graphite. Dolomitization occurred as a result of the interaction of these fluids with a calcitic marble band adjacent to the Emirli fault zone. Subsequent introduction of Fe2+ caused ankeritization along dolomite crystal boundaries during first-stage Sb-Au mineralization.

Compreignacite, a naturally occurring potassium uranyl oxide hydrate, is an expected alteration product of spent nuclear fuel subjected to oxidative corrosion in the presence of water. Ion-exchange experiments were performed using natural crystals of compreignacite in a 2 M CsCl solution at 180°C for 24 h, and in a 100 ppm CsCl solution at 90°C for 14 days. Exchange of Cs into crystals of compreignacite was demonstrated by crystal-structure analysis for a crystal from 2 M solution and chemical analysis for crystals from both exchange experiments. The structure of Cs-exchanged compreignacite is hexagonal, space group P2m, a= 14.1014 (18) Å, c = 15.127(3) Å, V = 2605.1(7) Å2. It was solved by direct methods and refined on the basis of F2 for all unique reflections to a final R1 = 6.37%. The structure determination demonstrated almost complete exchange of Cs for K in the interlayer of the structure, as confirmed by compositional analysis of the crystals, and provided the formula Cs6[(UO2)12(OH)10O10](H2O)3.5, Z= 2. The structure of Cs-exchanged compreignacite contains α-U3O8-type sheets of uranyl pentagonal bipyramids that are topologically identical, although compositionally distinct, to those in compreignacite. Compreignacite crystals placed in 100 ppm CsCl solution also incorporated substantial Cs by ion exchange. Ion exchange experiments, using Cs-exchanged compreignacite from earlier experiments, in 2 M KCl solution at 90°C for 14 days showed that compreignacite will retain significant Cs in the presence of a solution rich in K. These experiments indicate that formation of compreignacite structure-type phases in a geological repository due to alteration of nuclear waste may significantly impact upon the mobility of Cs, either by direct incorporation of Cs into growing crystals, or by exchange of Cs into earlier-formed crystals of compreignacite when they contact Cs-bearing solutions.

New constraints on the thermodynamic equation of state of water and the predicted water fugacity dependence of OH-solubility at elevated P-T conditions along with its influence on dislocation dynamics in olivine are reviewed. Water is shown to control the style of tectonics of a planetary lithosphere by switching on highly localized weak faulting instead of a broad, slow creeping flow. The transition occurs above a water concentration of 200 ppm H/Si. We argue that this changeover in style of tectonics has important implications for the mechanics of subduction and for plate tectonics in general. Efficient recycling of water is only given if the top strong part of the lithosphere can fail and be dragged down into the mantle in a steady way. Due to different starting conditions and differences in accretion through planetismals, Venus may have never have reached a water content above 200 ppm H/Si in the upper mantle while Mars would have now left the plate tectonic regime due to fast cooling.

Alluvial rubies and sapphires are found in palaeodrainage deposits along the Cudgegong-Macquarie River system, central eastern New South Wales, Australia. A pink to red suite contains Cr (up to 0.6 wt.% Cr2O3) as the main chromophore, exceeding Fe (up to 0.5 wt.%Fe2O3). Corrosive etching suggests a prior xenocrystic Mesozoic-Cenozoic basaltic transport, while Cr2O3/Ga2O3 to Fe2O3/TiO2 ratios indicate an original metamorphic source. Syngenetic mineral inclusions include Al-rich diopside, meionite and anatase. The Al-rich diopside (‘fassaite’) contains extremely high Al2O3 (20–21 wt.%). A blue-green suite contains Fe (up to 0.8 wt.% Fe2O3) as a dominant chromophore, while a rare nepheline-anorthoclase composite inclusion supports a magmatic phonolitic origin. The Cudgegong- Macquarie ruby formation is compared with a garnet granulite origin proposed for Thailand rubies and a xenolith of corundum-bearing garnet granulite from Ruby Hill, Bingara, Australia. Clinopyroxenecorundum thermometry suggests the Cudgegong-Macquarie rubies formed at T >1000–1300ºC, a high equilibration T for proposed lithospheric granulites. These rubies form a distinctive suite compared to other rubies from Australian and SE Asian basalt fields, but have some similarities with eastern Thailand rubies.

Ilmenite concentrates obtained from heavy mineral deposits in the Murray Basin, southeastern Australia contain appreciable quantities (up to 10 wt.%) of an unusual hydrated Fe titanate mineral in the form of orange to red coloured translucent grains. The grains are weakly magnetic and have a low apparent density (<3.3 g cm–3) due to microprosity, which enables them to be easily concentrated in a pure state. Samples from different deposits have similar analyses of 67–69% TiO2, 8 –9% Fe2O3, 2–3% FeO, 11 –12% H2O and 8 –9% of intra-pore impurities, mainly SiO2 and Al2O3. The powder pattern for the mineral closely matches that for pseudorutile; having a hexagonal subcell with a = 2.844 (1) Å, c = 4.575 (1) Å. The idealized composition range of the Fe titanate, calculated from analyses and structure refinements, is [FeTi6O12(OH)3].3H2O to [FeTi6O11(OH)5].2H2O. The molecular water is nonstructural, probably adsorbed on the surfaces of nano-scale domains of the mineral. Electron microprobe and scanning electron microscopy studies provide evidence for formation of the mineral by replacement reactions acting on MgO-rich ferrian ilmenite grains. The mineral represents a distinct intermediate in the chemical weathering of ilmenite, having a pseudorutile-like structure but a leucoxene-like composition. It is unusual in not having undergone any recrystallization to phases such as rutile and anatase.

Weakly peralkaline syenite ejecta within the plinian fall deposits of Agua de Pau volcano (São Miguel, Azores Islands) are divisible into (1) silica-undersaturated and (2) silica-saturated/oversaturated groups. The first group occurs in the pre-Fogo-A pyroclastic falls (15.2 ka) whereas the second occurs in the Fogo-A pumices (5 ka). The petrography indicates that the syenites of both groups crystallized at shallow depths and whole-rock geochemistry shows that they have compositions reflecting those of the Agua de Pau trachyte magmas. The syenites are inferred to be derived from solidification zones around the margins of the parental magma chamber. Mineral parageneses in both syenite groups permit distinction of three magmatic stages of crystallization: (1) an early crystallization stage; (2) a main crystallization stage during which most of the feldspar growth occurred; and (3) a late interstitial stage. Crystallization of the trachytic magmas yielded peralkaline residuals, highly enriched in volatiles, alkalis, HFSE and REE. In the silica-undersaturated syenites, the complex Zr-Ti silicate minerals, eudialyte and a låvenite-like mineral, crystallized interstitially from the residual magmas. In contrast, the zircono-silicate dalyite, and REE-rich minerals (chevkinite-(Ce), britholite-(Ce) and pyrochlore), together with thorite, were late-stage interstitial products of the silica-saturated/oversaturated syenites.

Fluoronyböite, ideally NaNa2(Al2Mg3)(Si7Al)O22F2, has been found in the Jianchang eclogite pod, Su-Lu coesite-eclogite province, China. It has been approved as a new mineral by the IMA. Single-crystal structure refinement and electron microprobe analysis were used for characterization: C2/m, with a = 9.666(4), b = 17.799(6), c = 5.311(2) Å, β = 104.10(3)º, V = 886.2(8) Å3, Z = 2, formula: A(Na0.78K0.06)Σ0.84B(Na1.53Ca0.47)Σ2.00C(Fe2+0.89Mg2.55Mn0.01Zn0.01Fe3+0.32Al1.21Ti0.01)Σ5.00T(Si7.14Al0.86)Σ8.00O22X(OH0.84F1.16)Σ2.00.

Fluoronyböite formed during UHPM conditions, and is preserved in the retrograded kyanite-bearing eclogite sample DJ102 together with clinopyroxene (Jd70Ae20Di10), garnet (Alm60Prp21Grs17Sps02), and rutile. Lower-pressure minerals are also present (fluoro-alumino-magnesiotaramite, apatite, paragonite), and symplectitic rims were also developed around clinopyroxene crystals. Cation ordering and the structural and physical properties of fluoronyböite are reported and discussed with reference to those of F-free nyböite from the type locality at Nyböin Norway, for which some as yet unpublished mineral data are also reported. Relations between composition and petrogenetic conditions of these rare high-pressure amphiboles are discussed.

The original description of nickelphosphide from the Butler meteorite [(Ni1.83Fe1.21)Σ3.04P0.96 to (Ni1.71Fe1.28Co0.01)Σ3.00P1.00] lacks detailed and accurate powder data – with only 11 observed reflections down to 1.37 Å. Consequently, no crystal structure information for this phase is available. Here we present the crystal structure for a synthetic analogue of the phase found in the Vicenice IID medium octahedrite (with a mean empirical formula of (Ni1.69Fe1.31)Σ3.00P1.00) and a hypothetical Ni3P end-member. Unit-cell dimensions of the synthetic analogue of Ni1.68Fe1.33P0.99 composition from individual peak profile fitting of XRD data collected with Cu radiation are a= 9.0168(2)Å, c= 4.4491(1)Å, V= 361.72(1)Å3 and those for Ni3P composition are a= 8.9546(1)Å, c= 4.38714(8)Å, V= 351.783(8)Å3. The space group of the mineral is I4¯ and Z= 8. The crystal structure refined from powder data by the Rietveld method is consistent with that refined and published for Fe3P and Ni3P synthetic compounds as well as Fe-dominant schreibersite from single-crystal data. However, because of the similarity of the scattering of iron and nickel, we were not able to refine directly the site occupancies in the synthetic analogue of the nickelphosphide from the Vicenice iron meteorite.

Small deviations from higher symmetry can be established by single-crystal diffraction methods by (1) measuring the metric of the unit cell with high, non-routine precision; (2) measuring a full reflection sphere of diffraction data and testing it for the presence or absence of symmetry elements in the dataset; (3) refining the structure in both the higher and the lower symmetry and comparing the results; (4) checking the refined crystal structures for the presence or absence of hidden symmetry elements. By these criteria it is not established that the v{120} growth sector of yugawaralite really has triclinic symmetry (Tanaka et al., 2002). On the contrary, the refined metrical parameters and the atomic positions conform to monoclinic symmetry within the margins of experimental error.

Dumortierite occurs as small nodules or thin layers along horizontal fractures in the altered volcanic rocks of the Milyang clay deposit, southeastern Korea. Textural evidence shows that dumortierite is associated with pyrophyllite, suggesting that the silica activity increased with decreasing B and Al activities during the hydrothermal alteration. Dumortierite chemistry shows a slight excess of Al, possibly due to common occurrence of Al-rich minerals in the clay deposit. The structural formula of dumortierite is recalculated as Al6.93(Fe0.03Mg0.07)B(Si2.99Al0.01)O18. An absorption peak at 1387 cm–1 in the IR spectrum indicates that B is present in three-fold coordinated sites. The 29Si MAS NMR spectrum has two peaks at –90.9 and –95.5 ppm, showing that Si in dumortierite is located in two different crystallographic sites and is linked to four octahedral Al atoms. The 27Al MAS NMR spectrum shows only one asymmetrical peak near 0 ppm, suggesting that there is no substitution of Al for Si. The 11B MAS NMR spectrum at 17.5 ppm shows a typical second order quadrupole pattern represented by the three-fold coordinated B. The 11B chemical shifts indicate that all of the B occupies such sites, indicating that the B sites are axially symmetric or nearly so in a very well defined site.

The chemical composition of unaltered biotites extracted from 18 Lower Palaeozoic metabentonites from Sweden, Norway and Scotland was determined. Discrimination based on FeO, MgO and TiO2 proved able to separate the metabentonites on the basis of their stratigraphical age. A triangular discrimination diagram using MgO, FeO and Al2O3 classified the biotites as calc-alkaline. Independent support for the discriminant power of FeO, MgO and TiO2 in biotite comes from Sr isotope ratios and Sr concentration data from cognate apatite crystals. Within this dataset Caradocian and Llandoverian metabentonites have unique biotite compositions, while Wenlockian samples can be characterized to a lesser degree. Biotite composition also supported the correlation of a pair of metabentonites from Norway known to form part of the same horizon. Biotite in metabentonites preserves the chemical signature of the host magmas in which it crystallized and can be used to discriminate between metabentonites of different ages and provenance.