The use of optical absorption spectroscopy for the study of the changes in local distortions during phase transformations is discussed, with particular reference to the P213-P212121 transition in K2Co2(SO4)3 langbeinite. In order to extend this technique to the study of cobalt-doped cadmium langbeinite, K2Cd2(SO4)3, the consequences of the doping with regard to site occupancies and low signal strength are discussed, and some details of data modelling are considered. The problem of modelling the spectrum of Finero sapphirine is taken as an example, and it is shown that even simple and evidently inadequate models can provide useful information.

The results of optical spectroscopic investigation of the P213-P212121 transition in K2(Cd0.98Co0.02)2(SO4)3 langbeinite are presented. The trigonal splitting of the spin allowed 4T1g(F)-4T1g(P) transition has been determined, and shows a linear increase with increasing temperature in the high temperature cubic phase, and a constant value in the low temperature phase. This is in good agreement with previous structural work on this material, and it is concluded that optical spectroscopy of doped materials can provide useful information about site distortions.

Electron microprobe analyses of micas from the Cairngorm pluton in the Eastern Grampian Highlands of Scotland show extensive compositional variation in biotite, despite a lack of chemical variation in the host granite. Biotite has high Fe/(Fe + Mg) (0.6–0.85) and Alvi (0.6–2.1 a.f.u.), and enrichment trends in these two parameters are attributable to the Al-Tschermak and dioctahedral-trioctahedral substitutions, the latter becoming dominant with increasing Alvi content. Ti content is low (0.2–0.4 a.f.u.), and is largely controlled by a Tschermak-type substitution. Biotite is also unusually rich in Mn (up to 2.57 wt. % MnO), which increases with both Alvi and Fe/(Fe+Mg). F contents generally range between 0.55 and 2.05 wt.% All compositional variation in biotite can be attributed to the extensive development of a fluid phase during the late-magmatic and subsolidus evolution of the pluton. The presence of an abundant fluid phase has resulted in the alteration of biotite to muscovite, which has occurred in response to de-stabilization of the biotite as octahedral R2+ cations are lost in favour of Al. Extreme build-up of this fluid phase has resulted in the crystallization of muscovite as a late, interstitial primary phase. Both primary and replacive muscovite have Fe/(Fe+Mg) > 0.50, 15–36 mol. % celadonite and <1 mol. %paragonite.

The vicinity of the 490 Ma Cashel gabbroic intrusion experienced pressures of about 4.05 ± 0.2 kbar and temperatures in excess of 850 °C. These conditions caused intense hornfelsing and partial melting of the surrounding Dalradian metasediments. From the study of the progressively changed composition of the aureole hornfelses it is deduced that elements were fractionated into the melts as follows: Si>K>Na>Ca>Mn>Al>Fe>Mg and Rb>Ba>Sr>Ga>Cr,Ni,Co. This order of fractionation, which is the opposite to that in magmatic crystallization, provides a detailed picture of the mode of interaction between a mantle derived basic magma and mid-crustal rocks, illustrating how one type of S-type granite can be produced. The rare earth elements (REE) were both removed and fractionated but Eu largely remained in the crystal fractions giving increasing positive Eu anomalies with rising partial melting and these trends can be explained by the extraction of a granitic melt from the hornfelses. Fission track mapping of U is used to study the behaviour of U within the aureole and the metamorphic recrystallization of detrital brown zircon to pink new zircon. The S-type Cashel microgranite sill is shown to have been derived by anatexis from the Dalradian rocks, to have preserved the Sr isotope ratios of the metasediments at 490 Ma, and not to be of the same composition as the leucosomes in the metasediments.

The Grenvillian granulite-facies complex on Holsnøy island, Bergen Arcs, W. Norway, has been metamorphosed at eclogite-facies conditions during the Caledonian orogeny (ca. 425 Ma). The granulite-eclogite facies transition takes place along shear zones and fluid pathways. Mineral thermobarometry indicates PT conditions of 800–900°C and 8–10 kbar for the Proterozoic granulite facies metamorphism and 700–800°C and 16–19 kbar for the eclogite-forming event. Quartz in the granulite facies complex contains CO2 fluid inclusions with less than 2.5 mole percent N2; the molar volumes are compatible with the PT conditions of the Proterozoic granulite metamorphism. Quartz in pegmatitic quartz + omphacite and quartz + phengite/paragonite veins coeval with shear-zone eclogites contain N2 ± CO2 fluid inclusions. Combined laser Raman microanalysis and microthermometry show that the least disturbed inclusions have XCO2 = 0.1–0.3, and molar volumes less than 40 cm3/mole, which may agree with the PT conditions during Caledonian high-pressure metamorphism. Younger, low-density N2 and N2-H2O fluid inclusions are the results of decrepitation and redistribution of early inclusions during the retrograde PT evolution of the eclogites.

Almandine- and grossular-rich garnet occurs as both a coronitic and non-coronitic phase in ferruginous, Grenvillian (c. 1050 Ma) granitoid rocks of the composite Potato Hill pluton of the Long Range Inlier, Newfoundland. The country rock includes garnetiferous gneiss, but garnets in the pluton are compositionally distinct (higher Ca and Mn, lower Mg), so none are interpreted as xenocrysts from the Long Range gneiss complex.

Coronal garnet, quartz and hornblende separate primary pyroxene, ilmenite and hornblende from feldspar in two-pyroxene charnockite. Balanced mass-transfer reactions based on microprobe data and modes for the pyroxene-centred corona structures suggest that corona sites gained Fe and lost Na. The flux of Fe apparently controlled corona growth in the charnockite. The corona structures are attributed to subsolidus cooling of the pluton rather than to a metamorphic overprint because the coronas are obliterated in high strain zones cutting the charnockite. Temperature of formation is constrained at c. 775–630°C by two-pyroxene and garnet-hornblende thermometry. Compositionally-similar coronas in rare, Fe-rich enderbite of the Long Range gneiss complex probably formed during cooling after early, high-grade metamorphism or following the regional emplacement of the Grenvillian plutons.

Non-coronitic garnets occur in equigranular and megacrystic hornblende-biotite granite. Garnets in the equigranular granite are large, well-formed, and in some instances are associated with compositional layering of probable igneous origin. These garnets are enriched in grossular (XCa = 0.28), and are therefore interpreted as phenocrysts crystallized at high pressure (>9 kbar?). They would nevertheless have been stabilized to lower pressures by their moderate spessartine content (XMn = 0.13).

Garnets in foliated megacrystic granite form tiny crystals depleted in Fe and Mg, and enriched in Mn and Ca, and in these respects are similar to garnet in deformed charnockite. These garnets are therefore interpreted to have formed (or re-equilibrated) during the late Grenvillian deformation. Garnet is absent in relatively magnesian Grenvillian granites (bulk XFe2+ = 0.50–0.85) elsewhere in the inlier. The restriction of garnet to the Potato Hill pluton (bulk XFe2+ = 0.88–0.94) therefore testifies to bulk compositional controls on the formation of both magmatic and subsolidus garnet in this intrusion.

This first report of the occurrence of a kimberlitic rock in Pakistan is supported by its field relations, textures and mineral chemistry. Linear dykes, lenses, conical and pipe-like bodies, plugs and sills intrude non-orogenic, early Jurassic limestone near the SW extremity of an Eocene-emplaced ophiolite on the transform-type Indian plate margin; far away from the stable Precambrian craton. The rock resembles ‘micaceous kimberlites’ petrographically and contains olivine, phlogopite, perovskite, chromian spinel, monticellite, chlorite, serpentine, calcite, apatite, pectolite, clinopyroxene, amphibole, nepheline, magnetite and titanomagnetite. The minerals and their microprobe analyses resemble those of kimberlitic rocks.

Preliminary fluid inclusion measurements have been made on quartz (whole rocks and segregations) and garnet from a blueschist terrain. Although further measurements are required, the fluids apparently associated with the blueschist event are aqueous with no thermometrically detectable CO2, a feature which is consistent with mineral-fluid equilibria studies. The salinity of the fluid inclusions is highly variable, from almost pure H2O to halite saturation, and a mechanism involving hydration reactions, such as proposed by Crawford et al. (1979), is suggested. Fluid inclusions associated with the greenschist overprint, which has affected the terrain, are also aqueous in nature.

Mössbauer spectroscopy and electron microscopy were combined to study one Al-poor anthophyllite and one Al-rich gedrite. TEM show that Al-rich gedrite is not homogeneous and that the complexity of its Mössbauer spectrum is due to sub-microscopic intergrowth of chlorite and lizardite.

The UG1 Footwall unit is a layered pyroxenite-norite-leuconorite-anorthosite sequence between the Middle Group 4 and Upper Group 1 chromitites of the Upper Critical Zone, and is c. 300 m thick at Rustenburg Platinum Mines, Union Section, where it shows an oscillatory fluctuation in whole-rock Mg/(Mg + Fe), Cr/Co, Ni/V and Fe/Ti ratios with stratigraphic height. This permits subdivision into 8 sub-cycles which match a subdivision based on cyclical variations in orthopyroxene and feldspar compositions. Constituent pyroxene grains of pyroxenites, norites and leuconorites alike contain rounded and embayed plagioclase inclusions in abundance. Sr-isotope disequilibrium prevails in some samples between the orthopyroxene and feldspar populations. Chemical and isotopic data support a model of pulsatory injection of limited volumes of a more primitive, mafic liquid into a resident column of depleted residua, from which sodic labradorite and Mg-poor bronzite were crystallizing. The depleted liquid is equated with the supernatant liquid residuum of buried cumulates (Sric. 0.7054) and the primitive liquid with magma parental to the UG1-UG2 lineage (Sri ⩾ 0.7068). The increase in leucocratic character of the 300 m column, with height, is attributed to the rising of low-density liquids enriched in the components of feldspar during separation of the pyroxenites. Deposition of the UG1 chromitite layers is attributed to mixing of a major influx of primitive liquid with a feldspathic residuum at the top of the UG1 Footwall unit. There is no evidence to indicate the participation of a discrete A-type liquid (Irvine and Sharpe, 1982) in this process.

Graphitic, quartz-rich black slate within the Late Ordovician Abercrombie Beds, Lachlan Fold Belt, southeast Australia, has undergone contact metamorphism adjacent to the Siluro-Devonian Wyangala Batholith. This produced porphyroblasts of andalusite and cordierite, and smaller grains of pale green phengitic mica. Later regional metamorphism caused complete retrogression of cordierite and partial retrogression of andalusite, with margarite replacing some andalusite.

The aluminous minerals andalusite, margarite and phengite all contain V and Cr substituting for Al. Andalusite has up to 1.39% V2O3 and 1.09% Cr2O3, margarite has up to 1.07% V2O3 and 0.37% Cr2O3, and phengitic mica has up to 6.93% V2O3 and 1.52% Cr2O3. This mica also has BaO contents of up to 1.96%.

Chemical analyses reveal very high SiO2 contents for these rocks (about 89%), carbon contents of about 2%, and extremely low CaO, FeO, MgO and Na2O. Although V and Cr are prominent in aluminous minerals, their concentrations in the rock are only about average for black shales. However, Ba values range from 2000 to 6000 p.p.m., well above average for black shales. It is suggested that V and Cr probably precipitated from sea water, but Ba may have been concentrated by planktonic organisms such as radiolaria.

The Kruidfontein volcanic complex is a Proterozoic collapsed carbonatitic caldera structure, the inner caldera of which is filled with carbonatitic bedded volcaniclastic rocks cut by carbonatite dykes, and the outer with bedded silicate tuffs. As well as numerous fragments of phonolitic pumice in the silicate tuffs, there are unusual banded fragments composed of alternating silicate and carbonate compositions which appear to have been originally glasses, and which give evidence for mechanical mixing of magmas which may originally have been magmas separated by liquid immiscibility. The fragments have also been strongly fenitized with the introduction of K and the replacement of Al by Fe.

Proterozoic amphibolites from Sweetwater Wash, in the Old Woman Mountains of southeastern California, contain a variety of mineral assemblages dominated by the low-Ca amphiboles anthophyllite, gedrite, and cummingtonite. Their Mg- and Al-rich, Ca-poor bulk compositions suggest that the amphibolites represent basalts that were altered prior to metamorphism. In addition to amphiboles, mineral assemblages include cordierite, biotite, garnet, Ca-rich plagioclase, and ilmenite ± rutile. Corundum, staurolite, and spinel occur locally in Al-rich enclaves associated with cordierite. Orthoamphiboles commonly exhibit complex microstructures, including twinning, intergrowths, and apparent exsolution; spot analyses show an unusually large range of chemical compositions, even within a single thin section, in several cases extending across the crest of the solvus in the orthoamphibole system. Ionic substitution within the orthoamphibole series was dominated by the Mg-tschermakitic and edenitic exchange reactions. The amphibolites are thought to have been subjected to metamorphic temperatures above the orthoamphibole solvus during both the Proterozoic and the Cretaceous. Cretaceous metamorphism was followed closely by rapid uplift and denudation, which may be responsible for the exsolution and range of compositions of the orthoamphiboles.

Physical, crystal-chemical and absorption spectroscopical properties of blue tourmalines from a new occurrence in the State of Paraiba, Brazil, are described. Refractive indices, birefringence and specific gravity have been determined as ne = 1.615–1.620, no = 1.632–1.640, Δn=−0.017 to −0.020 and 3.04–3.07g/cm3. Microprobe analyses proved the samples to be elbaites, which are relatively Mn-rich and contain 2.1 wt. % CuO and 0.5 wt. % Bi2O3. Lattice constants are ao = 15.854(4) and co = 7.102(1) Å. The blue colour is due to pleochroic absorption bands of Cu2+ and Mn3+ with maxima at 700 and 520 nm respectively.

Microthermometric characteristics of metamorphic to hydrothermal fluids and microfracturing were studied in a contact zone between metamorphic series and peraluminous granites, located in the southern part of the Mont Lozère pluton (Massif Central, France). Four major stages of fluid production or migration have been recognized: (1) N2-CH4 (±CO2)-rich fluids related to the metamorphism of the C-bearing shales, occurring as fluid inclusion along the quartz grain boundaries; (2) CO2-CH4-H2O vapours or liquids, with homogenization temperatures of 400 ± 20 and 350 ± 50°C respectively, related to the first hydrothermal stage produced by the late peraluminuous intrusions; (3) aqueous fluids having low salinities and Th in the range 150–330°C; (4) low-temperature aqueous fluids.

It is shown that the percolation of hydrothermal fluids occurs through a dense set of microfissures on a microscopic scale. The different stages of fluid percolation have been investigated by relating the deformational events to the observed fracturing. The nature of the hydrothermal fluid has been deduced by studying the trails of fluid inclusions. Analysis of the relationships of the fluid inclusion trails (F.I.T.) with structures associated with plastic deformation show that their propagation is independent of the intracrystalline anisotropies. Combined studies of their orientation in space and their microthermometric characteristics show that: (1) according to the direction, several generations of fluids are distinguished within each sample on the basis of their physical-chemical characteristics; they correspond to different stages of the hydrothermal activity and to different directions of micro-crack opening; (2) in bulk isotropic media (granite), fluid inclusion trails are essentially mode I cracks which can be used as excellent markers of paleostress fields; however, in bulk anisotropic media (quartz lenses in mica schists) the migration directions of the fluids are mostly dependent on the local reorientations of the stress fields.

The study of the contact zone between granites and a metamorphic series submitted to local abnormal heat flows shows that fluid characteristics are significantly different in the two environments. Migration of carbonic fluids from mica schists towards granites occurred but is relatively limited, whilst aqueous fluids mixed in variable amounts with carbonic fluids in the metamorphic zone.

The Iblean Plateau (Southeastern Sicily, Italy) consists of a thick Meso-Cenozoic carbonate sequence with interbedded volcanic horizons (alkaline and tholeiitic basalts). The alkaline basalts contain ultramafic (peridotites and pyroxenites) and mafic xenoliths. The peridotites are spinel-bearing lherzolites and lherzolitic harzburgites, with porphyroblastic to protogranular texture. Pyroxenites consist of Cr-diopside-bearing and Al-augite-bearing websterites. The mineral chemistry of the nodules indicates temperatures between 700 and 1050°C.

Fluid inclusions containing CO2 and (sometimes) various proportions of silicate glass have been studied in olivine, orthopyroxene and clinopyroxene. The secondary inclusions occur as trails of CO2-rich inclusions, often cross-cutting deformation lamellae. The few primary inclusions, generally empty, show clear evidence of decrepitation. Of the 390 inclusions examined, 97% homogenized to the liquid phase (Th → L = −43.9 to +30.9°C); 3% homogenized to the vapour phase (Th → V = + 20.5 to +30.3°C, yelding CO2 densities in the range 0.20–1.13 g/cm3. Assuming a trapping temperature of 1100°C, the corresponding trapping pressure for a pure CO2 system lies in the range 0.6–11.0 kbar, i.e. a depth of ∼2.2 to 42 km.

The majority of CO2 trapping events in the xenoliths occurred from 2.2 to 11.0 kbar, with no major trapping events at pressures less than 2.3 kbar, indicating the absence of a shallow magma reservoir below the Iblean Plateau.

Basal cleavage faces of apophyllite crystals were etched in the base etchant (dil HF) containing different concentrations of ammonium fluoride as a poisoning salt. At low concentrations, square pyramidal pits formed with their sides parallel to the <100> direction. At higher concentrations, pits with their sides parallel to the <100> direction were formed. The lateral growth of a pit is dependent on pH value of the etching solution. Activation energy for dissolution at a pit (active site) was found to decrease with increasing concentration of poison in the base etchant. The change in orientation of the pit is attributed to adsorption of aqueous complexes having different chemical constitutions which have different directional adsorption sites in apophyllite.

Two new occurrences of Zn-rich minerals are described from the SM6 lujavrite unit of the Motzfeldt alkaline centre, South Greenland. Zinc and beryllium complexes in the magma gave rise to the formation of interstitial grains of genthelvite (Zn4Be3Si3O12S), identified in samples by strong green cathodoluminescence. It is suggested that subsequent metasomatism leached Be from the genthelvite, giving rise to the formation of associated willemite (Zn2SiO4).

The Prins Christians Sund rapakivi granite pluton in South Greenland is a member of the early Proterozoic ‘Rapakivi Suite’ and is emplaced into early Proterozoic Ketilidian migmatites. The pluton is composed predominantly of black or dark brown monzonites and quartz monzonites (collectively, rapakivi granites), although a localised white facies is developed adjacent to metasedimentary xenoliths. The back rapakivi granites are extremely fresh and have an anhydrous primary mafic mineralogy of olivine and orthopyroxene, with rare inverted pigeonite and clinopyroxene; minor amounts of biotite and amphibole occur in most fayalite-bearing rapakivi granites. Feldspars in these rocks are black and non-turbid. The white rapakivi granites have a wholly hydrous mafic silicate assemblage and turbid, white or cream-coloured feldspars. Electron microprobe analyses of the mafic silicates in the black rapakivi granites show that they are Fe-rich, comprising fayalite (Fa93−96.5), orthopyroxene (Fs77−81), ferro-pargasitic and ferro-edenitic hornblende (Fe/(Fe + Mg) = 0.72−0.93), and biotite (Fe/(Fe + Mg) = 0.77−0.88). Both biotite and amphibole crystallised subsolidus, and often adopt symplectic morphologies. Biotite has formed in response to a fayalite-consuming reaction at temperatures below 650–700°C and fO2, of 10−16.5 to 10−17.5 bars, and continued to grow under reducing conditions below the QFM buffer to temperatures below 450–500°C. Orthopyroxene formed in response to a low-pressure fayalite-consuming reaction in the melt. The correlation of black, pristine feldspar with anhydrous mafic silicates, and of turbid feldspar with hydrous phases suggests either that the feldspars reflect the anhydrous nature of the parent magma, or more likely that the mafic mineralogy of the white rapakivi granites is secondary.