The Lower Mafic Succession of the Great Dyke is a 700 m thick sequence of gabbroic rocks which shows remarkably regular mineral compositional trends and trace element contents in whole rocks. Such chemical trends are strongly indicative of undisturbed fractionation having taken place within the magma chamber and contrast with the major development of cyclic units which characterize the underlying Ultramafic Sequence of the Great Dyke. The style of fractionation is quite different to that in the equivalent Main Zone of the Bushveld Complex with the latter possibly reflecting a ‘leaky’ input system, whereas in the Great Dyke the magma chamber was sealed. Major compositional reversals at the interface between the websterite layer (the topmost unit of the Ultramafic Sequence) and the base of the Lower Mafic Succession indicate a change in crystallization conditions at this level. Modal percentages of plagioclase and Al2O3 content of pyroxenes show the same trends indicating a strong control by temperature and magma composition.

Modelling of the fractionation processes and the influence of trapped liquid was carried out for Mg#, Cr2O3, and NiO in pyroxenes and for Zr in whole rock. The lowermost gabbroic rocks are adcumulates with effectively zero trapped liquid which contrasts with 10–15% trapped liquid in the underlying websterite There is a gradual rise in the amount of trapped liquid upwards in the Lower Mafic Succession. These results have implications for the mechanisms by which porosity is reduced in mafic cumulates. An injection of a small amount (10%) of new magma at the interface of the Ultramafic-Mafic Sequences of the Great Dyke was of a composition slightly different to that which gave rise to the cyclic units of the Ultramafic Sequence.

Strongly peraluminous, cordierite-bearing anatectic dacites from the offshore Tertiary Erlend volcanic centre, north of the Shetland Isles, are shown to contain graphite which is interpreted as being essentially a restite phase inherited from carbonaceous pelitic source rocks. The form and characteristics of the graphite are documented and graphite geothermometry applied to establish that the graphite records a minimum peak temperature of ∼800°C, confirming that temperatures at which anatexis occurs were attained. The different morphological forms of graphite observed suggest the possibility that minor amounts of fluid-deposited graphite may also be present. The chemistry of the Erlend dacites is compared with that of other known examples of graphite-bearing peraluminous silicic igneous rocks and briefly with experimentally generated peraluminous liquid compositions. The Erlend source rocks were probably subjected to a higher degree of partial melting than has occurred in the petrogenesis of many other anatectic peraluminous silicic rocks.

In contrast with igneous and metamorphic rocks, classical petrochemical calculation methods cannot be used for tropical weathering components (saprolite, bauxitic, ferruginous, siliceous and calcareous laterite) in converting whole-rock chemical analyses into normative mineralogical weight percentages. Weathering profiles are characterized by a mixture of primary and secondary minerals, which are not considered in the classical methods of mineralogical norm calculation. A new petrochemical calculation algorithm is proposed for the conversion of whole-rock chemical analyses into weathering norm (WN) for several components of the tropical weathering profiles. The normative minerals are represented by three primary minerals, six secondary minerals, four primary/secondary mineral pairs, and five minerals which can have both primary and secondary origin. This algorithm has been used in MINNOR, a WINDOWS application written in Visual Basic, which calculates the mineralogical norm. In order to test the program, several types of different chemical weathering profiles from South America and Africa have been selected. Special attention is paid to the weathering profile from Omai, Guyana, South America.

Perovskite group minerals, general formula ABX3, from the intrusive ultramafic alkaline Gardiner Complex, East Greenland, range from almost pure CaTiO3 (perovskite, sensu stricto), to the rare earth element (REE) variety, loparite-(Ce). Chemical zonation in the perovskites (sensu lato), is described by the substitutions 2Ca2+ = (Na+ + REE3+) on the A-site and 2Ti4+ = (Fe3+ + Nb5+) on the B-site. Other trace elements detected include Th, Sr, Al, Si, Zr, Ta and Sn. Excellent agreement was found between the determinations of the REE by electron microprobe and neutron activation analysis. Chondrite-normalized REE patterns display enrichment in the light rare earths for perovskite, loparite, apatite, melilite and diopside. Mean perovskite/apatite partition coefficients from four of the Gardiner rocks were calculated as La = 10.4, Ce = 13.8, Nd = 13.9, Sm = 9.9, Eu = 7.7, Gd = 5.2, Tb = 5.6, Tm = 5.5, Yb = 2.7 and Lu = 1.6, indicating that perovskite concentrates all REE to a much greater extent than apatite. Light-REE enrichment occurs in both perovskite and apatite.

The diagenetic to very low-grade metamorphic manganese ores of the Postmasburg manganese field provide a unique example of oxide-facies manganese ores in a Palaeoproterozoic palaeokarst setting. The ores are composed mainly of braunite group minerals, including braunite, partridgeite and bixbyite, with rare braunite II and Ca-poor, silica-depleted braunite. Iron-poor partridgeite is distinguished from Fe-rich bixbyite and the occurrence of Ca-poor, silica-depleted braunite is reported for the first time. Braunite and partridgeite formed during early diagenesis but remained stable under greenschist facies metamorphic conditions. In contrast, bixbyite is apparently a product of metasomatic remobilisation under peak metamorphic conditions. It is suggested that local variations of the metamorphic mineral association reflect variations of the host rock composition and that they are not related to changing P-T conditions of metamorphic alteration, a model promoted by previous authors. The phase chemistry of braunite, braunite II and bixbyite is explained by the existing polysomatic stacking model for the braunite group. However, the chemical composition of partridgeite and Ca-poor, silica-depleted braunite can only be explained by introducing a distinct module layer, with partridgeite composition, to the existing polysomatic stacking model.

The mineralogical status of ilmenite from a prominent modern placer deposit of India is illustrated using different techniques. Compositional, powder XRD, TGA and SEM analyses prove that consistent low temperature alteration took place in Chavara ilmenite leading to the formation of a pseudorutile-hydrated-ilmenite stage. Except for the indication of a geochemical zonation at the southern tip of the deposit, the Chavara ilmenite points to a common origin throughout its 22 km stretch along the coast. We advocate a major segregation activity by marine factors to the accumulated sediments in the shelf zone in order to originate such a huge deposit of homogeneous composition.

New intersectorial isotope data are presented for two calcites. Mendip calcite shows no detectable δ13C and δ18O differences between synchronous {214} and {014} sectors. Nottingham calcite shows a δ13C difference of 1.0‰ and a δ18O difference of 0.5‰ between synchronous {401} and {0001} sectors. Data now available for 5 different calcites show the magnitude of intersectorial fractionation is variable; the effect on δ13C is twice that on δ18O. All five natural calcites also show erratic isotopic differences between symmetrically-equivalent synchronous sectors. Intersectorial isotopic fractionation is probably widespread but its cause and quantification require further work. Synchronous intracrystalline isotopic differences should be accommodated in the interpretation of isotopic data and should influence future sampling strategy.

The FTIR spectra of synthetic BaMg(CO3)2 (norsethite) are measured at ambient temperature and atmospheric pressure, and the influence of formation conditions on the FTIR spectra is investigated. The results are compared with those for natural norsethite from Långban (Sweden) and Rosh Pinah (Namibia). The Raman spectrum of synthetic norsethite is reported, too. A number of first-order internal modes of the carbonate ion group (ν1, ν2, ν3, ν4) are found to be infrared and Raman active. Additonally, the (ν1+ν3) and (ν1+ν4) combination modes and the (2*ν2) overtone are observed in the FTIR and Raman spectrum, respectively. The carbon isotopic-shift coefficient for ν2 due to the substitution of 12C by 13C (ν2(13CO32-)/ν2(12CO32-) = 0.971 ± 0.002), observed by FTIR spectroscopy, agrees with the theoretical value of 0.969.

The proton microprobe has been used to determine contents of Ca, Ti, Ni, Mn and Zn in the olivine of 54 spinel lherzolite xenoliths from Australian and Chinese basalts. These data are compared with proton-probe data for Ni, Mn and Zn in the olivine of 180 garnet peridotite xenoliths from African and Siberian kimberlites. Fe, Mn, Ni and Zn contents are well-correlated; because the spinel lherzolite olivines have higher mean Fe contents than garnet peridotite olivines (average Fo89.6vs. Fo90–92) they also have lower Ni and higher Mn contents. Zn and Fe are well-correlated in garnet peridotite olivine, but in spinel peridotites this relationship is perturbed by partitioning of Zn into spinel. None of these elements shows significant correlation with temperature. Consistent differences in trace-element contents of olivines in the two suites is interpreted as reflecting the greater degree of depletion of Archean garnet peridotites as compared to Phanerozoic spinel lherzolites. Ca and Ti contents of spinel-peridotite olivine are well correlated with one another, and with temperature as determined by several types of geothermometer. However, Ca contents are poorly correlated with pressure as determined by the Ca-in-olivine barometer of Köhler and Brey (1990). This reflects the strong T-dependence of this barometer: the uncertainty in pressure (calculated by this method) which is produced by the ±50°C uncertainty expected of any geothermometer is ca ± 8 kbar, corresponding to the entire width of the spinel-lherzolite field at 900–1200°C.

Recent studies on albitite rocks located in the granodiorite complex of Central Sardinia have revealed that epidote has a widespread occurrence as a light rare-earth element (LREE)-bearing accessory common phase. Titanite has been recorded as a heavy rare earth element (HREE)-bearing mineral. The Hercynian granodiorite complex of Central Sardinia is composed chiefly of quartz, Ca-plagioclase, K-feldspar and biotite and of a wide variety of secondary assemblages, mainly allanite, titanite and zircon. Albitic plagioclase and quartz are the main mineral components of the albitites. Additional minerals include, besides allanite and epidote, a more calcic-plagioclase (oligoclase), K-feldspar, chlorite, titanite and more rarely muscovite. The mineral assemblages and REE-bearing minerals of albitites were analysed by wavelength dispersive spectrometry (WDS). Chemical data suggest that there is a near complete solid-solution between epidote and allanite whereas little variations in HREE of titanites were detected. In epidote-group minerals a pronounced zoning in REE was observed while titanite was recorded unzoned. Textural relations were studied by SEM to distinguish primary from secondary epidotes. Chemical criteria to recognize magmatic from alteration epidotes were also applied. The alteration epidotes mainly occur and generally originate from plagioclase alteration and from leaching of magmatic allanite. Comparison of textures using both the SEM technique and EPMA data showed that the characteristic ‘patchy zoning’, observed in epidotes, corresponds with different amounts of REE in these minerals.

The schematic model proposed for the epidote-forming reactions during the metasomatic processes that affected the granodiorites involves: (i) the instability of the anorthitic component of plagioclase; (ii) the simultaneous formation of albite; (iii) the leaching of the magmatic allanite with a redistribution of REE in the epidotes of the albitites.

Feinglosite, the zinc analogue of arsenbrackebuschite, was found lining a cavity in a sample of massive chalcocite from Tsumeb, Namibia. In this cavity it is associated with wulfenite, anglesite and goethite. The mean of seven electron-microprobe analyses (wt.%) is: PbO 61.4, ZnO 7.3, FeO 1.8, As2O5 22.1, SO3 5.3, H2O (by difference) [2.1], total = [100.00]%, leading to the ideal formula: Pb2(Zn,Fe)[(As,S)O4]·H2O. Feinglosite is monoclinic, space group P21 or P21/m, a 8.973(6), b 5.955(3), c 7.766(6) Å, β 112.20(6)°, with Z = 2. The strongest five reflections of the X-ray powder diffraction pattern are [d in Å (I) (hkl)]: 4.85 (50) (110), 3.246 (100) (112), 2.988 (60) (301), 2.769 (60) (300/211), 2.107 (50) (321). The mineral is pale olive-green, transparent, sectile, and has a white streak and adamantine lustre. It overgrows clusters of goethite crystals and forms globular microcrystalline aggregates up to 0.5–0.75mm in size. The hardness on Mohs' scale is 4–5: the mean micro-indentation hardness is 263 at VHN100. Its calculated density is 6.52 g cm−3. The mineral is pale brownish grey in reflected light (when compared with goethite). Visible spectrum reflectance data are presented. Feinglosite is named for Mark N. Feinglos who first recognised the mineral on a specimen in his collection.

The International Mineralogical Association's approved amphibole nomenclature has been revised in order to simplify it, make it more consistent with divisions generally at 50%, define prefixes and modifiers more precisely and include new amphibole species discovered and named since 1978, when the previous scheme was approved. The same reference axes form the basis of the new scheme and most names are little changed but compound species names like tremolitic hornblende (now magnesiohornblende) are abolished and also crossite (now glaucophane or ferroglaucophane or magnesioriebeckite or riebeckite), tirodite (now manganocummingtonite) and dannemorite (now manganogrunerite). The 50% rule has been broken only to retain tremolite and actinolite as in the 1978 scheme so the sodic calcic amphibole range has therefore been expanded. Alkali amphiboles are now sodic amphiboles. The use of hyphens is defined. New amphibole names approved since 1978 include nyböite, leakeite, kornite, ungarettiite, sadanagaite and cannilloite. All abandoned names are listed. The formulae and source of the amphibole end member names are listed and procedures outlined to calculate Fe3+ and Fe2+ when not determined by analysis.