Portions of the carbonatitic fluids responsible for the deposition of apatite from the Tororo car-bonatite complex are trapped and preserved as minute (< 100 µm) inclusions within the apatites. These fluids consist predominantly of alkali-carbonate-bearing brines and demonstrate that water and alkalis played an important role in the formation of the carbonatites from this complex. Furthermore, the opinion that carbonatite ‘magmas’ are richer in alkalis and water than the chemistry of the carbonatites themselves reveal is clearly substantiated. The mean minimum formation temperature of the apatites from five separate carbonatite samples were determined from the homogenization temperatures of 200 primary aqueous inclusions. The results from Limekiln Hill samples (328 °C 321 °C 359 °C) are similar to those from samples of the separate carbonatite mass at Tororo Rock (353 °C, 365 °C).

Cathodoluminescence emission spectra and luminescence excitation spectra of Mn2+ in calcites, dolomites, magnesites, a manganocalcite and a rhodochrosite have been measured at both room temperature and 77 K. Ligand-field parameters have been calculated from the excitation spectra which reflect the size of the metal cation site in which the Mn2+ ion resides. The technique of luminescence excitation spectra has enabled the absorption profile of Mn2+ in Mg and Ca sites in dolomite to be separately determined. The variation of the distribution of Mn2+ between Mg and Ca sites in dolomites is demonstrated and discussed in terms of a simple model. It is concluded that the distribution of Mn2+ in dolomites may well provide information about its conditions of formation and/or subsequent alteration.

Itoigawaite, SrAl2Si2O7(OH)2·H2O, is a new member of the lawsonite group found in the Itoigawa-Ohmi district, central Japan. It is orthorhombic, Cmcm, a = 6.031(2), b = 8.945(2), c = 13.219(4) Å, Z = 4. The strongest lines in the X-ray powder diffraction pattern are 4.68 (s) (111), 4.26 (vs) (021), 3.31 (vs) (113), 2.75 (vs) (114, 202), 2.68 (vvs) (130), 2.63 (s) (131), 2.50 (s) (220, 203, 132), 2.45 (s) (221). Electron microprobe analysis gave SiO2 32.98, TiO2 0.87, Al2O3 27.67, Fe2O3 0.39, MgO 0.27, CaO 0.45, SrO 27.71, H2O (diff.) 9.66, total 100.00 wt.%, corresponding to (Sr0.97Ca0.03Mg0.02)Σ1.02 (Al1.97Ti0.04Fe0.02)Σ2.03Si1.99H3.89O10 on the basis of O = 10. It is transparent, blue in colour with vitreous lustre. The streak is white and the cleavage good in one direction. The hardness is 5–5.5. The calculated density is 3.3 g cm−3. It is colourless in thin section and optically biaxial positive with α = 1.664 (2), β = 1.674 (2), γ = 1.688 (2) and 2V(calc.) = 81°. It occurs in a thin veinlet cutting a lavender-coloured Ti-bearing jadeitite. The veinlet includes irregularly-shaped aggregates composed of minute tabular crystals of itoigawaite up to 50 µm across and minute jadeite crystals with interstitial natrolite aggregates. Itoigawaite is considered to be crystallized from fluid during later stage activity of high-P/T metamorphism. The name is for the locality.

The results of a microstructural study by backscattered scanning electron microscopy and a microchemical study using X-ray microprobe analysis of phyllosilicate intergrowths from sandstones, shales, metagreywackes, and low-grade schists are presented. The microstructural study revealed that the intergrowths thicken and become more coherent with metamorphic grade; the intergrowths change from incoherent to coherent in the anchizone. The increasing coherency is mirrored by an increase in the crystallinity indices of the illites/phengites. Chemical analysis of the individual intergrowth phases was difficult in the sediments and no systematic compositional variations were recorded. However, clear compositional trends with increasing metamorphic grade emerged in the phengites from the metagreywackes and schists, but in the chlorites only slight compositional changes were recorded.

Skaergaardite, PdCu, is a new mineral discovered in the Skaergaard intrusion, Kangerdlugssuaq area, East Greenland. It occurs in a tholeitiic gabbro associated with plagioclase, clinopyroxene, orthopyroxene, ilmenite, titanian magnetite, fayalite and accessory chlorite-group minerals, ferrosaponite, a member of the annite–phlogopite series, hornblende, actinolite, epidote, calcite, ankerite, apatite and baddeleyite. The mineral is found in composite microglobules composed of bornite, chalcocite, digenite, chalcopyrite, with rare cobalt pentlandite, cobaltoan pentlandite, sphalerite, keithconnite, vasilite, zvyagintsevite, (Cu,Pd,Au) and Pt-Fe-Cu-Pd alloys, unnamed PdCu3, (Pd,Cu,Sn), Au3Cu and PdAuCu. Skaergaardite occurs as droplets, equant grains with rounded outlines, subhedral to euhedral crystals and as irregular grains that vary in size from 2 to 75 μm, averaging 22 μm. It is steel grey with a bronze tint, has a black streak, a metallic lustre and is sectile. Neither cleavage nor fracture was observed. The mineral has a micro-indentation hardness of VHN25 = 257. It is isotropic, non-pleochroic and exhibits neither discernible internal reflections nor evidence of twinning. Skaergaardite varies from bright creamy white (associated with bornite and chalcopyrite) to bright white (associated with digenite and chalcocite). Reflectance values in air (and in oil) are: 58.65 (47.4) at 470 nm, 62.6 (51.1) at 546 nm, 64.1 (52.8) at 589 nm and 65.25 (53.95) at 650 nm. The average of 311 electron-microprobe analyses gives: Pd 58.94, Pt 1.12, Au 2.23, Cu 29.84, Fe 3.85, Zn 1.46, Sn 1.08, Te 0.28 and Pb 0.39, total 99.19 wt.%, corresponding to (Pd0.967Au0.020Pt0.010)Σ0.997(Cu0.820Fe0.120 Zn0.039Sn0.016Te0.004Pb0.003)Σ1.002. The mineral is cubic, space group Pm3m, a = 3.0014(2) Å, V = 27.0378 Å3, Z = 1. Dcalc is 10.64 g/cm3. The six strongest lines in the X-ray powder-diffraction pattern [d in Å (I)(hkl)] are: 2.122(100)(110), 1.5000(20)(200), 1.2254(50)(211), 0.9491(20)(310), 0.8666(10)(222), 0.8021(70)(321). The mineral has the CsCl-type structure. It is believed to be isostructural with wairauite (CoFe), synthetic CuZn (β-brass) and is structurally related to hongshiite (PtCu). Skaergaardite developed from a disordered Pd-Cu-rich metal alloy melt that had exsolved from an earlier Cu-(Fe) sulphide melt. Ordering of Pd and Cu (beginning at T ≈ 600°C) results in development of the CsCl structure from a disordered face-centred cubic structure.

The Qassiarsuk (formerly spelled Qagssiarssuk) complex is located in a roughly E–W trending graben structure between Qassiarsuk village and Tasiusaq settlement in the northern part of the Precambrian Gardar rift, South Greenland. The complex comprises a sequence of alkaline silicate tuffs and extrusive carbonatites interlayered with sandstones, and their subvolcanic equivalents, which represent possible feeders for the extrusive rocks. The Rb-Sr, Sm-Nd and Pb isotopic characteristics of 65 samples of extrusive carbonatite- and silicate tuffs and carbonatite diatremes have been determined by mass spectrometry. The Qassiarsuk complex can be dated to c. 1.2 Ga by Rb-Sr and Pb-Pb isochrons on whole-rocks and mineral separates, agreeing with previous isotopic ages for the volcanic rocks of the Eriksfjord formation in the Eriksfjord area of the Gardar rift, but not with previous, indirect age estimates of >1.31 Ga for assumed Eriksfjord equivalents in the Motzfeldt area further east. Recalculated isotopic compositions at 1.2 Ga indicate that the Qassiarsuk carbonatite- and alkaline-silicate magmas were comagmatic and derived from a depleted mantle source (εNd>4, εSr<−13, time-integrated, single- stage 238U/204Pb ≤ 7.4). The mantle-derived magmas were contaminated with crustal material, equivalent to the local, pre-Gardar granites and gneisses and sediments derived from these. The crustal component has a depleted mantle Nd model age of 2.1-2.6 Ga; at 1.2 Ga it was characterized by εSr = +76, εNd = −8.4, time-integrated, single- stage 238U/204Pb = 8.2−8.3. Strong decoupling of the Pb from the Sr and Nd isotopic systems suggests that the contamination happened only after carbonatitic and alkaline-silicate magmas had evolved from a common parent, by processes such as liquid immisicibility and/or fractional crystallization. Post-magmatic hydrothermal alteration (oxidation, hydration of mafic silicates, carbonatization of melilite) may have contributed further to the contamination of the carbonatite and alkaline silicate rocks of the Qassiarsuk complex.

Effenbergerite, ideally BaCu[Si4O10], structure determined by single crystal X-ray methods in space group P4/ncc, a = 7.442(2)Å, c = 16.133(5)Å, V = 893.50 Å3 Z = 4, is a new mineral from the Wessels mine, Kalahari Manganese Field, South Africa. It is associated with native copper, calcite, quartz and clinozoisite within pectolite veinlets, embedded in a matrix of braunite, sugilite and hausmannite. Effenbergerite occurs as transparent blue platelets with perfect cleavage parallel to {001} in sizes up to 8.0 × 8.0 × 0.1mm. It has a pale blue streak, subconchoidal fracture, a calculated density of 3.52gcm−3 and an estimated Mohs' hardness of 4–5. Effenbergerite is uniaxial negative with ω = 1.633(2), ε = 1.593(2), strongly pleochroic from intense blue (ω) to nearly colourless (ε). The strongest lines in the X-ray powder diffraction pattern (with refined lattice parameters a = 7.440(1)Å, c = 16.133(2)Å) are: (dobs/Iobs/hkl) (8.0624/100/002), (4.0325/39/004), (3.5443/29/104), (3.1998/44/114), (2.6892/21/006), (2.3943/41/116), (2.0169/34/008), (1.9466/22/108) and (1.4802/21/2.0.70).

Effenbergerite is the natural analogue to synthetic BaCu[Si4O10], isotypic with SrCu[Si4O10] and CaCr[Si4O10] as well as with the minerals cuprorivaite, CaCu[Si4O10] and gillespite, BaFe[Si4O10]. The structure consists of silicate sheets [Si8O20]8− parallel (001) formed by corner-linkage of silicate 4-membered rings. The copper(II) atom is nearly planar 4-coordinated; the barium atom has a distorted cubelike environment of oxygen atoms. The mineral is named for Dr. Herta S. Effenberger of the University of Vienna, Austria.

Diamonds from alluvial deposits near Wellington, New South Wales, have been characterized on the basis of morphological features, mineral inclusions, C isotope signatures, N content and aggregation state and internal structure. The diamonds are of two types. The larger group (Group A) is indistinguishable from diamonds found worldwide from kimberlitic and lamproitic host rocks. This group is inferred to have formed in a peridotitic mantle source in Pre-Cambrian subcratonic lithosphere. The second group (Group B) is unique in its internal structures (which show evidence of growth in a stress field and non-planar facets), has unusually heavy C isotopic compositions and contains Ca-rich eclogitic inclusions. This group is inferred to have formed in a subducting slab. Diamonds of both groups have external features (corrosion structures and polish) indicating transport to the surface by lamproitic-like magmas. The diamonds show evidence of long residence at the earth's surface and significant alluvial reworking: they are not accompanied by typical diamond indicator minerals.

Veins developed during contact metamorphism associated with the emplacement of the Cornubian granite batholith contain both H2O-rich and CO2-rich fluid inclusions. Microthermometric data indicate that unmixing of a low-CO2, low-salinity fluid occurred at 400–200°C and 1000–500 bars to produce low-density CO2-rich vapour and saline aqueous fluids (8–42 wt. % NaCl equivalent). Decrepitation-linked ICP analyses show that the cation composition of the brines is dominated by Na, K and Ca, but that significant amounts of Li, Sr, Ba, Fe, Mn, Zn and B are also present. Bulk volatile analyses confirm the dominance of CO2 over N2 and CH4 in the vapour phase, with CO2/N2 molar ratios of 15.3–28.7 and CO2/CH4 molar ratios of 66.9–292. The relative abundance of nitrogen suggests an aureole-derived ‘organic’ component is present.

The source of the fluids is ambiguous as they are intermediate in composition between ideal ‘magmatic’ and ‘metamorphic’ end-members. It is proposed that this is due to mixing of the two types of fluid in the contact aureole during granite intrusion. A model is suggested in which magmatic-metamorphic circulation occurred synchronously with granite emplacement and subsequently evolved to a meteoric-dominated system with the bulk of the ore deposits forming in response to the influx of meteoric fluids.

An inclusion of corundum (ruby) was found in a clinopyroxene xenocryst in alkali basalt from the late-Cenozoic Chanthaburi-Trat volcanics of eastern Thailand. The clinopyroxene is fairly sodic, highly aluminous and magnesian (0.12–0.14 Na, 0.31–0.33 AlIV and 0.36–0.40 AlVI per 6(O), and Mg/(Mg+Fe2+) > 0.9)) and is chemically similar to clinopyroxene inclusions in rubies from nearby alluvial gem deposits, suggesting a common origin for the two types of occurrence. Sapphirine (Mg/(Mg+Fe2+) = 0.91–0.94) and garnet (py56–67alm11–18grs18–23) also occur as inclusions in alluvial rubies. Thermodynamic calculation of the equilibrium 2 di + 2 crn = 2 cats + en constrains the temperatures of clinopyroxene + corundum crystallization to between 800 and 1150 ± 100°C. Use of other equilibria as stability limits places the pressures of crystallization between 10 and 25 kbar, implying depths of between 35 and 88 km. The most Fe-rich clinopyroxene crystallized at a pressure in the lower part of the range. The pyropic garnet inclusions in corundum crystallized at pressures of >18 kbar (i.e. at depths > ~63 km).

The xenocrystic clinopyroxene could have coexisted in equilibrium with garnet of similar composition to the observed inclusions at the deduced temperatures of crystallization. The rubies probably crystallized in rocks of mafic composition, i.e. garnet-clinopyroxenites or garnet-pyriclasites, within the upper mantle.

The crystal structure of coalingite (Mg10Fe2(OH)24(CO3)·2H2O) has been determined using single-crystal X-ray methods. The mineral is trigonal, with space group Rm, aH = 3·12, cH = 37·4 Å, Z = ½, and (0001) cleavage. The structure is of a layer type, and is based on a structural element about 12·5 Å thick in the c-direction and consisting of two brucite-like layers and one disordered layer containing carbonate ions and water molecules and resembling those in sjögrenite and pyroaurite. The unit cell comprises three of these structural elements stacked together in the c-direction. The Mg2+ and Fe3+ ions are randomly distributed among all the octahedral sites of the brucite-like layers. The structure closely resembles those of sjögrenite and pyroaurite, but has two brucite-like layers between each CO32−−H2O layer where these have one. There is a tendency to random interstratification, and the crystals appear to contain intergrown regions of brucite and of sjögrenite or pyroaurite. Coalingite-K probably has a similar structure, but with three brucite-like layers between each -H2O layer; its idealized formula is probably Mg16Fe2(OH)36(CO3).2H2O.

Crystallographic studies of micro-inclusions in diamond coat, carried out by analytical electron microscopic techniques, show that structures possessing rhombohedral symmetry form a significant fraction of the population of well-crystaUised particles. They are, however, less frequent than apatite or biotite, which were identified earlier by the same investigative methods. Thin-foil specimens of diamond coat were prepared by mechanical fine-polishing, and subsequently ion-beam milling, sawn and polished plates of coated diamonds oriented parallel to (100) or (110). The majority of crystalline inclusions analysed were ≤0.2 p,m in diameter. Data obtained on 15 individual inclusions, including composition analysis by energy-dispersive X-ray spectroscopy, are reported and discussed. The a-axis of the hexagonal unit cell, and the c/a ratio, were determined for all specimens, and are believed to be accurate to ≈1% in most cases. In 12 out of 15 specimens, the cations with Z ≥ 11 identified comprised substantially only Mg, Fe and Ca. Values of a in these specimens ranged from 4.81 to 4.92 Å; and for three of them the space group R, corresponding to the dolomite structure, was positively identified. These crystals are classed as ankerites. Representative Mg:Fe:Ca ratios in the ankerites are 28 : 18 : 54, with cell dimensions a = 4.87 Å, c/a = 3.37. The ankerites contained small amounts of Ba, typically 1-3%, and smaller amounts of Sr, typically 0.2-2%. Three out of the 15 specimens contained >10% Ba. In two of these, Ba and Ca concentrations were roughly equal, and in one of the two, which had cell parameters a = 5.11 Å, c/a = 3.50, the space group symmetry Rc, corresponding to the calcite structure, was verified.

The oxidation of amosite, crocidolite, and biotite has been determined at temperatures up to nearly 900 °C under both a vacuum (10−2 mm Hg) and oxygen (10 and 600 mm Hg). Infrared spectra gave the loss of constitutional hydroxyl under these conditions. The loss of tensile strength of the amphiboles with increasing temperature seems to be due to thermal decomposition. For the three minerals oxidation takes place progressively over a broad temperature range. Under vacuum there is a certain temperature above which the ferric iron previously formed is reduced; this temperature corresponds to the completion of the loss of hydroxyl. The crocidolite anhydride in the literature is most probably an oxycrocidolite formed by dehydrogenation, the truly dehydroxylated zones being amorphous.

The occurrence is reported of spectacular oriented needles of rutile within quartz veins and pods in granulite-facies rocks that have undergone partial melting under ultrahigh-temperature (UHT) conditions in the Karur region in southern India. Laser Raman spectroscopy and electron microprobe analysis confirm that (1) the mineral inclusions within quartz are pure rutiles, and (2) a secondcategory of quartz contains pure hematite inclusions. The rutile never coexists with the hematite inside the same quartz specimens. Fluidinclusions in the quartz are characterized as a CO2 + H2O mixture. Application of two geothermometric calibrations utilizing Ti in quartz yields minimum estimates of ~1190ºC, suggesting the formation of the rutile-quartz under UHT metamorphic condition. It is proposed that such Ti-rich quartz segregations couldbe another indicator for extreme crustal metamorphism at very high temperatures.

The hydrous calcium carbonate mineral ikaite (CaCO3.6H2O) forms in nature at low temperature in carbonate- and Ca-rich waters. Ikaite crystallizes in the spacegroup C2/c, and consists of CaCO3.6H2O units with Ca ions coordinated by eight oxygens, six from H2O and two from the carbonate group. Hydrogen bonding links CaCO3.6H2O moieties to form the crystal structure.

We have used synchrotron X-ray powder diffraction at T = 243 K to refine the monoclinic structure of ikaite, and have measured unit-cell parameters of ikaite between T = 114 K and T = 293 K. Anisotropic thermal expansion in ikaite is evident, with the smallest relative increase occurring along the b direction parallel to 2-fold axes. The contribution of hydrogen bonding to thermal expansion is assessed by comparison of our data with previously published data for deuterated ikaite, ice and gypsum. Ikaite exhibits a coefficient of volume expansion intermediate between that of ice (Ih) and of deuterated gypsum (CaSO4.2D2O) between T = 114 K and T = 293 K.

The Gaching high-sulfidation epithermal deposit in the Maletoyvayam ore field features a wide range of Se-containing minerals and selenides, as well as complex gold oxides, Au tellurides (calaverite, krennerite) and native gold typical for epithermal deposits. Pyrite included in quartzites and quartz-alunite rocks was probably formed during an early stage of the ore-forming process. During the following Au-rich stage, the $f_{{\rm S}{\rm e}_{\rm 2}}$/$f_{{\rm S}_{\rm 2}}$ increased with $f_{{\rm O}_{\rm 2}}$ being relatively high, resulting in the formation of very rare compounds that have not been previously described in nature. These include Au2Te4(Se,S)3, Se3Te2, AuSe and Au(Te,Se,S) phases. The Au2Te4(Se,S)3 compounds have some variations in composition: the complete isomorphic series between Au2Te4Se3 and Au2Te4S3 was observed. The gold and Au-minerals at the main ore stage can be stable within a range of log$f_{{\rm O}_{\rm 2}}$ of −27.3 and atmospheric oxygen (?); log$f_{{\rm S}{\rm e}_{\rm 2}}$ between −12.4 and −5.7; log$f_{{\rm T}{\rm e}_{\rm 2}}$ between −10.5 and −7.8; and log$f_{{\rm S}_{\rm 2}}$ between −12.8 and −6.8 (at 250°C). The increasing oxygen fugacity during the final stage of mineralization resulted in the formation of complex Sb,As,Te,S-bearing Au oxides. Gold-oxide formation occurs due to oxidation of Au-tellurides. The final products of this process are newly-formed secondary mustard gold and Te–Se solid solutions.

Boreal forest trees influence mineral weathering rates via exudation and uptake processes. Most trees in the boreal forest live in symbiosis with ectomycorrhizal (EcM) fungi that sheath most of the root tips and form the main interface between the tree and the soil. Current weathering models do not take into account the nature and scale of fungal-mineral interactions. Here we show for the first time grain-scale effects of EcM fungi in symbiosis with a host plant on mineral weathering under sterile conditions. EcM fungi actively direct their growth and energy flow towards mineral grains containing essential nutrient elements for the tree and fungus.

Massive stratiform and stratabound sulphide bodies in the central Appalachians exhibit a wide variety of metamorphic features which are typical of similar deposits world-wide. The ores occur as lens- to plate-like bodies which are concordant with the enclosing meta-sediments and volcanics and are interpreted as products of Late Precambrian to Early Palaeozoic submarine volcanism. Sulphide mineralization ranges from pyritic to pyrrhotinic bodies with variable, but Zn- and Cu-dominant, base-metal contents. The deposits have been subjected to metamorphism ranging from greenschist to amphibolite grade. The metamorphism has been pervasive and has resulted in thorough recrystallization of most ores and intense deformation of pyrrhotinic ores, but does not appear to have significantly altered original sulphide assemblages. Recrystallization has homogenized most sulphide minerals including pyrite and sphalerite, so that any original compositional zoning is no longer seen. The presence of chalcopyrite has apparently promoted an increase in grain size and has facilitated post-metamorphic retrograde re-equilibration. Consequently, sphalerite geobarometry is not reliable in Cu-bearing assemblages. Pyrrhotines, mostly hexagonal, have re-equilibrated to low temperatures but commonly display pressure twins and kink-banding, apparently due to the late stages of deformation. Characteristic mineralogical changes in the host rocks include changes in the abundance of minerals, changes in the Fe: Mg ratios, and the presence of gahnite.

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.