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Island-arc calc-alkaline dacites (66.7% SiO2, 3.4% Na2O, 1.9% K2O) form a subvolcanic body hosted within andesitic and trachyandesitic tuffs on the east of the Kara-Dag Volcanic Massif of the Crimean Mountains. These dacites characteristically contain many phenocrysts of plagioclase (bytownite Ca75–72Na24–27K0.5–1 confined to the cores and labradorite Ca67–52Na32–47K1 to the inner and outer rims) and low-Ti augite (augite Ca44Mg45Fe11 with 4.5% Al2O3 confined to the cores and augite Ca43–41Mg41–38Fe16–21 with 1–2% Al2O3 to the inner and outer rims). Titanomagnetite, ilmenite, and apatite are intergrown with augite. Low-Mg titanomagnetite is enriched in manganese (up to 4.5 wt % MnO) and zinc (up to 1.6% ZnO) and contains the ulvospinel endmember ranging between 39 and 28%. Low-Mn ilmenite contains 10 to 25 mol % of the hematite endmember, suggesting crystallization at elevated $${{f}_{{{{{\text{O}}}_{2}}}}}$$, that is, under water-saturated melt conditions. The Sr, Ce, and S contents in the apatite are low. The fluorine trend shows an increase in the F content from chlorine-hydroxyl-fluorapatite to fluorapatite. The groundmass of rhyolitic dacites (77.3% SiO2, 3.3% Na2O, and 2.5% K2O) consists of labradorite microlites Ca52–50Na46–48K2–3 with quartz, minor andesine Ca49–46Na49–52K2–3, oligoclase Ca27Na68K5, and anorthoclase in the interstitial spaces. An extremely high anorthite content of plagioclase that is typical of island-arc volcanic rocks is characteristic of these dacites. The crystallization temperature for augite is ~1050–950°C. Early crystallization of the coexisting titanomagnetite and ilmenite occurs at ~900°С with $${{f}_{{{{{\text{O}}}_{2}}}}}$$ 1 log unit higher than the QFM buffer. Their late crystallization occurs at ~880°С with $${{f}_{{{{{\text{O}}}_{2}}}}}$$ 2 log units higher than the QFM buffer.

Chenmingite (FeCr2O4; IMA 2017-036) is a high-pressure mineral, occurring as micrometer- to submicrometer-sized lamellae within precursor chromite grains along with xieite and Fe,Cr-rich ulvöspinel next to shock-induced melt pockets, from the Tissint martian meteorite. The composition of type chenmingite by electron probe analysis shows an empirical formula of (Fe2+0.75Mg0.23Mn0.02) (Cr1.60Al0.29Fe3+0.06Fe2+0.04Ti0.02)Σ2.01O4. The general and end-member formulas are (Fe,Mg)(Cr,Al)2O4 and FeCr2O4. Synchrotron X-ray diffraction reveals that chenmingite has an orthorhombic Pnma CaFe2O4-type (CF) structure with unit-cell dimensions: a = 9.715(6) Å, b = 2.87(1) Å, c = 9.49(7) Å, V = 264.6(4) Å3, and Z = 4. Both chenmingite and xieite formed by solid-state transformation of precursor chromite under high pressure and high temperature during the Tissint impact event on Mars. The xieite regions are always in contact with melt pockets, whereas chenmingite lamellae only occur within chromite, a few micrometers away from the melt pockets. This arrangement suggests that chenmingite formed under similar pressures as xieite but at lower temperatures, in agreement with experimental studies.

The metal-manufacturing method and smelting temperature of ancient metal-production processes have been studied by analyzing the principal elements and microstructures of slag. However, the microstructure of slag varies according to the solidification cooling rate and types and relative amounts of various oxides contained within the smelting materials. Hence, there is a need for accurate analysis methods that allow slag to be distinguished by more than its composition or microstructure. In this study, the microstructures of slag discharged as a result of smelting iron sands collected from Pohang and Gyeongju, as well as the slag excavated from the Ungyo site in Wanju, were analyzed by using metalloscopy, scanning election microscopy-energy dispersine X-ray spectroscopy(SEM-EDS) and wavelength dispersive X-ray fluorenscence(WD-XRF). Furthermore, the microcrystals were accurately characterized by performing Raman micro-spectroscopy, which is a technique that can be used to identify the microcrystals of slags. SEM-EDS analysis of Pohang slag indicated that its white polygonal crystals could be Magnetite; however, Raman micro-spectroscopy revealed that these crystals were actually ulvospinel. Raman micro-spectroscopy and SEM-EDS were also used to verify that the coarse white dendritic structures observed in the Gyeongju-slag were Wustites. Additionally, the Wanju slag was observed to have a glassy matrix, which was confirmed by Raman micro-spectroscopy to be Augite. Thus, we have demonstrated that Raman micro-spectroscopy can accurately identify slag microcrystals, which are otherwise difficult to distinguish as solely based on their chemical composition and crystal morphology. Therefore, we conclude that it has excellent potential as a slag analysis technique.

Replacement reactions occur during metamorphism and metasomatism in response to changes in pressure, temperature and bulk rock and fluid compositions. To interpret the changes in conditions, it is necessary to understand what phases have previously been present in the rocks. During fluid-mediated replacement, the crystallography of the replacement phases is often controlled by the parent reactant phase. However, excessive fluid fluxing can also lead to extreme element mobility. Titanium is not mobile under a wide range of fluid compositions and so titanium-bearing phases present an opportunity to interpret conditions from the most extreme alteration. We map orientation relationships between titanium-bearing phases from ore deposits using EBSD and use symmetry arguments and existing relationships to show that completely consumed phases can be inferred in ore deposits. An ilmenite single crystal from Junction gold deposit is replaced by titanite, rutile and dolomite. The rutile has the following well-documented orientation relationship to the ilmenite [0001]ilmenite // rutile and ilmenite // [001]rutile The anatase is a single crystal and shows a potential orientation relationship [0001]ilmenite = (0001)ilmenite // {211}anatase and ilmenite // anatase The single crystal orientation and lack of symmetrical equivalent variants suggest nucleation dominates the anatase production. Dolomite grew epitaxially on the ilmenite despite only sharing oxygen atoms suggesting the surface structure is important in dolomite nucleation. Titanite partially replaced ilmenite during metasomatism at Plutonic gold deposit. The titanite orientation is weakly related to the ilmenite orientation by the following relationship: [0001]ilmenite // titanite and { $$10{\bar{1}}0$$ }ilmenite // (001)titanite The prevalence of subgrain boundaries in the titanite suggests multiple nucleation points on an already deformed ilmenite needle leading to the formation of substructure in the absence of deformation. Existing known topotaxial replacement relationship can be used to infer completely replaced phases using the misorientation distributions of the replacement polycrystals. Orientation modelling for a cubic phase replaced by rutile in a sample from Productora tourmaline breccia complex shows misorientation distributions consistent with Rutile // cubic and Rutile // cubic Combining this with volume constraints and assuming Ti is immobile, the composition of the cubic phase is constrained as titanomagnetite with 85% ulvospinel. Complex microstructures with domanial preferred orientations can also be used to document the microstructure of replaced phases. An aggregate of rutile grains with two parts that share a common axis is interpreted as having replaced a twinned ilmenite grain. Modelling shows that the misorientation distribution for the aggregate is consistent with the above relationship replacing ilmenite with a { $$10{\bar{1}}2$$ } twin.

Geochemical and iron isotopic compositions of magnetite, ilmenite and pyrite separates from the Fe Ti oxide ores hosted in the Damiao anorthosite-type Fe Ti ore deposit were analyzed to investigate sub-solidus cooling history of the titanomagnetite. The Fe Ti oxides form two series of solid solutions, namely, ulvospinel-magnetite (Usp-Mtss) and hematite-ilmenite (Hem-Ilmss) solid solutions. The magnetite separates have 14–27 mol% ulvospinel, while the ilmenite separates have 5–8 mol% hematite. Major element compositions of the mineral separates suggest that the ilmenites were mainly exsolved from the Usp-Mtss by oxidation of ulvospinel in the temperature range of ~820–600 °C and experienced inter-oxide re-equilibration with the magnetites. Associated with the exsolution is the substantial inter-mineral iron isotope fractionation. The magnetite separates are characterized by high δ57Fe (+0.27 − +0.65‰), whereas the ilmenite separates have lower δ57Fe (−0.65 to −0.28‰). Two types of pyrite are petrographically observed, each of which has a distinctive iron isotope fingerprint. Type I pyrite (pyriteI) with higher δ57Fe (δ57Fe = +0.63 − +0.95‰) is consistent with magmatic origin, and type II pyrite (pyriteII) with lower δ57Fe (δ57Fe = −0.90 to −0.11‰) was likely to have precipitated from fluids. Iron isotopic fingerprints of the pyriteI probably indicate variations of oxygen fugacity, whereas those of the pyriteII may result from fluid activities. The iron isotopic fractionation between the magnetite and ilmenite is the net result of sub-solidus processes (including ulvospinel oxidation and inter-oxide re-equilibration) without needing varying oxygen fugacity albeit its presence. Although varying composition of magnetite-ilmenite pairs reflects variations of oxygen fugacity, inter-oxide iron isotopic fractionation does not.

Five compositional-textural types of ilmenite can be distinguished in nine kimberlites from the Eastern Dharwar craton of southern India. These ilmenite generations record different processes in kimberlite history, from mantle to surface. A first generation of Mg-rich ilmenite (type 1) was produced by metasomatic processes in the mantle before the emplacement of the kimberlite. It is found as xenolithic polycrystalline ilmenite aggregates as well as megacrysts and macrocrysts. All of these ilmenite forms may disaggregate within the kimberlite. Due to the interaction with low-viscosity kimberlitic magma replacement of pre-existing type 1 ilmenite by a succeeding generation of geikielite (type 2) along grain boundaries and cracks occurs. Another generation of Mg-rich ilmenite maybe produced by exsolution processes (type 3 ilmenite). Although the identity of the host mineral is unclear due to extensive alteration and possibility includes enstatite. Type 4 Mn-rich ilmenite is produced before the crystallization of groundmass perovskite and ulvospinel. It usually mantles ilmenite and other Ti-rich minerals. Type 5 Mn-rich ilmenite is produced after the crystallization of the groundmass minerals and replaces them. The contents of Cr and Nb in type 2, 4 and 5 ilmenites are highly dependent on the composition of the replaced minerals, they may not be a good argument in exploration. The highest Mg contents are recorded in metasomatic ilmenite that is produced during kimberlite emplacement, and cannot be associated with diamond formation. The higher Mn contents are linked to magmatic processes and also late processes clearly produced after the crystallization of the kimberlite groundmass, and therefore ilmenite with high Mn contents cannot be considered as a reliable diamond indicator mineral (DIM) and kimberlite indicator mineral (KIM).

Compositional zoning is common in magnetite from different geological environments, but its formation mechanism remains controversial. Here, we characterize micron- to nano-scale textural and chemical variations in zoned magnetite from the Sossego iron oxide-copper–gold deposit (Carajas, Brazil) using electron probe microanalyzer (EPMA) and transmission electron microscopy (TEM). Lack of porosity and of a reaction front at both the micron and nanometer scales indicates that compositional zoning in magnetite is a pristine texture formed during crystal growth, rather than a secondary texture due to dissolution and reprecipitation reaction. TEM energy dispersive X-ray spectrometry analyses and mapping identify four types of nanoinclusions in zoned magnetite: 1) Mg-Fe-Al silicates, most likely amphibole, 2) Fe-Ti oxides, mainly ilmenite, 3) pyroxene, 4) Si-rich magnetite. The formation of ilmenite nanoinclusions in Sossego magnetite is possibly due to oxy-exsolution of ulvospinel from Ti-rich magnetite, whereas nanoinclusions of other minerals likely formed by local supersaturation in the fluid boundary layer, followed by magnetite crystal entrapment. Compositional zoning in magnetite likely formed by a self-organization process where fluid composition fluctuations are feedback responses for an evolving fluid system far from equilibrium, rather than cyclic variations in external factors such as temperature and oxygen fugacity. Saturation of silicate minerals results in relative depletion of Si, Ca, and Al in boundary layer fluids, and formation of inclusion-poor zone depleted in these elements. Nanoinclusions in magnetite highlight the importance of textural characterization when using in situ chemical composition to discriminate the origin of magnetite. In addition, the assemblages of nanoinclusions in magnetite can be used to complement the discrimination of magnetite origins.

Tsangpoite, ideally Ca5(PO4)2(SiO4), the hexagonal polymorph of silicocarnotite, and matyhite, ideally Ca9(Ca0.5□0.5)Fe(PO4)7, the Fe-analogue of Ca-merrillite, were identified from the D'Orbigny angrite meteorite by electron probe microanalysis, electron microscopy and micro-Raman spectroscopy. On the basis of electron diffraction, the symmetry of tsangpoite was shown to be hexagonal, P63/m or P63, with a = 9.489(4) Å, c = 6.991(6) Å, V = 545.1(6) Å3 and Z = 2 for 12 oxygen atoms per formula unit, and that of matyhite was shown to be trigonal, R3c, with a = 10.456 (7) Å, c = 37.408(34) Å, V = 3541.6 (4.8) Å3 and Z = 6 for 28 oxygen atoms per formula unit. On the basis of their constant association with the grain-boundary assemblage: Fe sulfide + ulvöspinel + Al-Ti-bearing hedenbergite + fayalite-kirschsteinite intergrowth, the formation of tsangpoite and matyhite, along with kuratite (the Fe-analogue of rhönite), can be readily rationalised as crystallisation from residue magmas at the final stage of the D'Orbigny meteorite formation. Alternatively, the close petrographic relations between tsangpoite/matyhite and the resorbed Fe sulfide rimmed by fayalite + kirschsteinite symplectite, such as the nucleation of tsangpoite in association with magnetite ± other phases within Fe sulfide and the common outward growth of needle-like tsangpoite or plate-like matyhite from the fayalite-kirschsteinite symplectic rim of Fe sulfide into hedenbergite, infer that these new minerals and the grain-boundary assemblage might represent metasomatic products resulting from reactions between an intruding metasomatic agent and the porous olivine-plagioclase plate + fayalite-kirschsteinite overgrowth + augite + Fe sulfide aggregates. Still further thermochemical and kinetics evidence is required to clarify the exact formation mechanisms/conditions of the euhedral tsangpoite, matyhite and kuratite at the grain boundary of the D'Orbigny angrite. Fil: Hwang, Shyh Lung. National Dong Hwa University; República de China Fil: Shen, Pouyan. National Sun Yat-sen Universit; República de China Fil: Chu, Hao-Tsu. Central Geological Survey; República de China Fil: Yui, Tzen-Fu. Institute of Earth Sciences; República de China Fil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; Argentina Fil: Iizuka, Yoshiyuki. Institute of Earth Sciences; República de China

The titanomagnetites (Fe2-xTixO4,x⩽ 1) are a family of reducible spinel-structure oxides of interest for their favorable magnetic, catalytic, and electrical transport properties. To understand the stability of the system during low temperature deposition, epitaxial thin films of Fe2TiO4were deposited by molecular beam epitaxy (MBE) on MgO(001) at 250-375 °C. The homogeneous incorporation of Ti, Fe valence state, and film morphology were all found to be strongly dependent on the oxidation conditions at the low substrate temperatures employed. More oxidizing conditions led to phase separation into epitaxial, faceted Fe3O4and rutile TiO2. Less oxidizing conditions resulted in polycrystalline films that exhibited Ti segregation to the film surface, as well as mixed Fe valence (Fe3+, Fe2+, Fe0). A narrow window of intermediate oxygen partial pressure during deposition yielded nearly homogeneous Ti incorporation and a large fraction of Fe2+. However, these films were poorly crystallized, and no occupation of tetrahedral sites in the spinel lattice by Fe2+was detected by x-ray magnetic circular dichroism at the Fe L-edge. After vacuum annealing, a small fraction of Fe2+was found to occupy tetrahedral sites. Comparison of these results with previous work suggests that the low temperature deposition conditions imposed by use of MgO substrates limits the incorporation of Ti into the spinel lattice. This work suggests a path towards obtaining stoichiometric, well-crystallized Fe2TiO4by MBE by utilizing high substrate temperature and low oxygen partial pressure during deposition on thermally stable substrates.

This study describes textures and mineral chemistry of magnetite-ilmenite-bearing pods/pockets in mineralogically diverse feldspathic schist near Pathargora in the Singhbhum Shear Zone, eastern India. The textural and geochemical characteristics of the magnetite-ilmenite assemblage are the results of a protracted geological history involving magmatic crystallization and oxidation-exsolution of titanomagnetite, deformation-induced recrystallization and textural re-equilibration and hydrothermal fluid-induced hematitization of magmatic magnetite. The magnetite grains contain characteristic trellis and sandwich ilmenite lamella, which are interpreted to be the products of oxidation-exsolution of ulvospinel component of magnetite-ulvospinel solid solution. The exsolution process was accompanied by preferential partitioning of spinel elements such as Cr, Al and V in magnetite and Ti, Mn, Mg, HFS elements (Nb, Ta), transition elements (Sc, Co, Cu and Zn) and granitophile elements (Mo, Sn and W) in ilmenite. The deformed sandwich lamella is locally recrystallized and transformed into granular ilmenite close to fractures, micro-shear planes and magnetite grain boundaries. Coarse granules of ilmenite, within or associated with magnetite, are of two textural types: one invariably contains Fe-rich exsolved phase and may be of magmatic origin, while the other mostly formed by strain-induced, fluid-mediated expulsion (from the interior of magnetite to its boundary) and dynamic recrystallization of existing ilmenite lamella in magnetite, and dynamic recrystallization of primary ilmenite containing Fe-rich exsolved phases. Magnetite is variably hematitized. The highly porous nature and trace element geochemistry of hematite and mass-balance calculations suggest the hematitization was mostly redox-independent and was caused by infiltration of metal-rich, reduced and acidic fluid. The hematitization process was associated with significant enrichment and immobilization of U, Th, Pb, REEs, Cu, Mo and W and depletion of Ni, Cr, V in hematite.

The Martian meteorites comprise mantle-derived mafic to ultramafic rocks that formed in shallow intrusions and/or lava flows. This study reports the first in situ platinum-group element data on chromite and ulvospinel from a series of dunitic chassignites and olivine-phyric shergottites, determined using laser-ablation ICP-MS. As recent studies have shown that Ru has strongly contrasting affinities for coexisting sulfide and spinel phases, the precise in situ analysis of this element in spinel can provide important insights into the sulfide saturation history of Martian mantle-derived melts. The new data reveal distinctive differences between the two meteorite groups. Chromite from the chassignites Northwest Africa 2737 (NWA 2737) and Chassigny contained detectable concentrations of Ru (up to ~160 ppb Ru) in solid solution, whereas chromite and ulvospinel from the olivine-phyric shergottites Yamato-980459 (Y-980459), Tissint, and Dhofar 019 displayed Ru concentrations consistently below detection limit (

Kuratite, ideally Ca4(Fe2+10Ti2)O4[Si8Al4O36], the Fe2+-analogue of rhönite and a new member of the sapphirine supergroup, was identified from the D'Orbigny angrite meteorite by electron microscopy and micro-Raman spectroscopy. Based on the least-squares refinement of 25 d-spacings measured from selected-area electron diffraction patterns of 11 zone axes, the symmetry of kuratite was shown to be triclinic (space group by analogy to rhönite) with a = 10.513(7), b = 10.887(7), c = 9.004(18) Å, α = 105.97(13), β = 96.00(12), γ = 124.82(04)°, V = 767 ± 2 Å3 and Z = 1 for the 40 oxygen formula. The empirical formula based on eight electron microprobe analyses is (Ca3.88Na0.02REE3+0.03Mn0.03Mg0.01Ni0.02Zn0.01Sr0.01)∑4.01 (Fe2+9.989.9Ti2.00)∑11.98(Si7.80Al3.52Fe3+0.64P0.05S0.02)∑12.03O39.98F0.01Cl0.01. The simplified formula is Ca4(Fe2+10Ti2)O4[Si8Al4O36]. Micro-Raman spectroscopy showed four main bands resembling those of lunar rhönite but with higher frequencies due to different chemical composition. Analogous to the occurrence of kuratite in terrestrial basaltic rocks, kuratite coexisting with Al, Ti-bearing hedenbergite, ulvöspinel, iron-sulfide, tsangpoite, Ca-rich fayalite and kirschsteinite in D'Orbigny angrite most probably was formed at >1000°C by rapid cooling of an interstitial melt, which is subsilicic, almost Mg-free but enriched in Al-P-Ca-Ti-Fe.

Two types of composite Fe(Co)Ti(O x ,OH y ) nanoflakes were prepared using the mechanochemical synthesis. TEM, XRD, EDX, magnetisation and Mossbauer spectroscopy methods were applied for the characterisation of the as-synthesised and annealed samples. For the samples with Fe:Ti = 1:1 and Fe:Co:Ti = 1:1:1 atom ratios, the as-synthesised nanoflakes were composed of feroxyhytes δ-FeOOH and β-Co(OH)2, respectively, and amorphous Ti, Fe and Co oxides as well. According to Mossbauer spectroscopy, Ti, Fe and Co cations were considerably intermixed in both composites. The average diameter of the nanoflakes was 23 and 33 nm, respectively. Annealing the samples at 550 °C led to the full crystallisation forming TiO2/Fe2O3 nanocomposite and nanocrystalline ferrite of a mixed composition consisting of a solid solution of maghemitised ulvospinel and cobalt ferrite. The samples showed magnetisation consistent with their determined structure.

Titanium-rich magnetite from different magmatic Fe-Ti oxide-bearing intrusions consists of host magnetite (nearly pure Fe 3 O 4 ) and different types of exsolution. The exsolution of Ti-rich magnetite is indicative of the physical and chemical conditions at which the host intrusions formed. However, the mechanisms to form these types of exsolution have been debated. To examine the formation mechanisms of the different types of exsolution, multiple microanalytical techniques, such as electron microprobe analysis, micro Raman spectroscopy, and micro X-ray diffraction, were used to examine the chemical composition, morphology, and crystalline structure of exsolved minerals in Ti-rich magnetite from different Fe-Ti oxide-bearing intrusions in China. The characterization results indicate that pleonaste and ilmenite are the two dominant exsolution phases in the Ti-rich magnetite, whereas the ulvospinel phase is barely found. The ilmenite exsolution may have different origins: (1) the cloth-texture lamellae primarily exsolved as ulvospinel, which was oxidized to ilmenite later at 600 °C; (3) some ilmenite lamellae exsolved directly from cation-deficient solid solution due to the substitution of Ti 4+ + □ → 2Fe 2+ ; (4) sub-solidus re-equilibration of coexisting Fe-Ti oxides can also lead to ilmenite exsolution in Ti-rich magnetite and magnetite exsolution in ilmenite.

Perovskite (Prv) was discovered in an abyssal harzburgite from a “mélange” type blueschist-bearing accretionary wedge of the Western Carpathians (Meliata Unit, Slovakia). Perovskite-1 formation in serpentinized orthopyroxene may be simplified by the mass-balance reaction: Ca2Si2O6 (Ca-pyroxene-member)+2Fe2TiO4 (ulvöspinel molecule in spinel)+2H2O+O2=2CaTiO3 (Prv)+2SiO2+4FeOOH (goethite). Perovskite-2 occurs in a chlorite-rich blackwall zone separating serpentinite and rodingite veins, and in rodingite veins alone. The bulk-rock trace-element patterns suggest negligible differences from visually and microscopically less (“core”) to strongly serpentinized harzburgite due to serpentinization and rodingitization: an enrichment in LREE(La,Ce), Cs, ±Ba, U, Nb, Pb, As, Sb, ±Nd and Li in comparison with HREE, Rb and Sr. The U/Pb perovskite ages at ~135 Ma are interpreted to record the interaction of metamorphic fluids with harzburgite blocks in the Neotethyan Meliatic accretionary wedge. Our LA-ICP-MS mineral study provides a complex view on trace element behaviour during the two stages of rodingitization connected with Prv genesis. The positive anomalies of Cs, U, Ta, Pb, As, Sb, Pr and Nd in Cpx, Opx and Ol are combined with the negative anomalies of Rb, Ba, Th, Nb and Sr in these minerals. The similar positive anomalies of Cs, U, Ta, ±Be, As, Sb found in typical serpentinization and rodingitization minerals, with variable contents of La, Ce and Nd, and negative anomalies of Rb, Ba, Th, Nb and Sr suggest involvement of crustal fluids during MP-LP/LT accretionary wedge metamorphism. LA-ICP-MS study revealed strong depletion in LREE from Prv-1 to Prv-2, and a typically negative Eu (and Ti) anomaly for Prv-1, while a positive Eu (and Ti) anomaly for Prv-2. Our multi-element diagram depicts enrichment in U, Nb, La, Ce, As, Sb, Pr, Nd and decreased Rb, Ba, Th, Ta, Pb, Sr, Zr in both Prv generations. In general, both Prv generations are very close to the end-member composition. In spite of low concentrations of isomorphic constituents, Prv-1 and Prv-2 display the A(La,Ce)3++B(Fe,Cr)3+=ACa2++BTi4+ heterovalent couple substitution. A decrease of ferric iron in Prv-2 indicates increasing reduction conditions during rodingitization.

A three-dimensional model describing the homogenization of titanomagnetites with magnetite–ulvospinel exsolution structures in the course of thermomagnetic analysis is presented. The implications of the size and shape of the exsolution structures and the initial titanomagnetite composition for the temperature dependence of saturation magnetization during repeated heating is analyzed. It is found that the dimension of the exsolution structures has the strongest effect, whereas the shape and composition only have an effect in the case of the small exsolution structures. A method is suggested for estimating the dimensions of the exsolution structures from the thermomagnetic curve. A close consistency of the results is revealed by comparing the distributions of the dimensions of the exsolution structures estimated by the electron microscopy and by the analysis of the thermomagnetic curve for the same sample.

Magnetite from hydrothermal ore deposits can contain up to tens of thousands of parts per million (ppm) of elements such as Ti, Si, V, Al, Ca, Mg, Na, which tend to either structurally incorporate into growth and sector zones or form mineral micro- to nano-sized particles. Here, we report micro- to nano-structural and chemical data of hydrothermal magnetite from the Los Colorados iron oxide–apatite deposit in Chile, where magnetite displays both types of trace element incorporation. Three generations of magnetites (X–Z) were identified with concentrations of minor and trace elements that vary significantly: SiO2, from below detection limit (bdl) to 3.1 wt%; Al2O3, 0.3–2.3 wt%; CaO, bdl–0.9 wt%; MgO, 0.02–2.5 wt%; TiO2, 0.1–0.4 wt%; MnO, 0.04–0.2 wt%; Na2O, bdl–0.4 wt%; and K2O, bdl–0.4 wt%. An exception is V2O3, which is remarkably constant, ranging from 0.3 to 0.4 wt%. Six types of crystalline nanoparticles (NPs) were identified by means of transmission electron microscopy in the trace element-rich zones, which are each a few micrometres wide: (1) diopside, (2) clinoenstatite; (3) amphibole, (4) mica, (5) ulvospinel, and (6) Ti-rich magnetite. In addition, Al-rich nanodomains, which contain 2–3 wt% of Al, occur within a single crystal of magnetite. The accumulation of NPs in the trace element-rich zones suggest that they form owing to supersaturation from a hydrothermal fluid, followed by entrapment during continuous growth of the magnetite surface. It is also concluded that mineral NPs promote exsolution of new phases from the mineral host, otherwise preserved as structurally bound trace elements. The presence of abundant mineral NPs in magnetite points to a complex incorporation of trace elements during growth, and provides a cautionary note on the interpretation of micron-scale chemical data of magnetite.

Using a diamond-anvil cell and synchrotron X-ray diffraction, the compressional behavior of a synthetic qandilite Mg2.00(1)Ti1.00(1)O4 has been investigated up to about 14.9 GPa at 300 K. The pressure–volume data fitted to the third-order Birch–Murnaghan equation of state yield an isothermal bulk modulus (K T0) of 175(5) GPa, with its first derivative $$K_{T0}^{{\prime }}$$ attaining 3.5(7). If $$K_{T0}^{{\prime }}$$ is fixed as 4, the K T0 value is 172(1) GPa. This value is substantially larger than the value of the adiabatic bulk modulus (K S0) previously determined by an ultrasonic pulse echo method (152(7) GPa; Liebermann et al. in Geophys J Int 50:553–586, 1977), but in general agreement with the K T0 empirically estimated on the basis of crystal chemical systematics (169 GPa; Hazen and Yang in Am Miner 84:1956–1960, 1999). Compared to the K T0 values of the ulvospinel (Fe2TiO4; ~148(4) GPa with $$K_{T0}^{{\prime }} = 4$$ ) and the ringwoodite solid solutions along the Mg2SiO4–Fe2SiO4 join, our finding suggests that the substitution of Mg2+ for Fe2+ on the T sites of the 4–2 spinels can have more significant effect on the K T0 than that on the M sites.

One-, two-, and three-dimensional models of magnetite–ulvospinel exsolution structures are constructed based on the experimental data. The models describe the zero state and the state of remanent saturation magnetization. A distinctive feature of these models is the calculation of the magnetostatic interaction between the ferromagnetic matrices of magnetite separated by paramagnetic ulvospinel lamella. The critical sizes of matrix transition from a single-domain to two-domain state are calculated. Based on the calculations, it is concluded that the matrices can only have a singleor two-domain structure. The ratios M rs /M s for the matrices of various sizes and the dependences describing the growth in the induced magnetic moment M i in the fields of up to 25 mT are calculated. The sizes of the exsolution structures in two samples are estimated by electron microscopy. The values observed in the experiments closely agree with the predictions by the suggested models.

[Figure][1] Spinel is a very important rock-forming mineral that is found in basalts from Earth, Mars, the Earth’s Moon, and basaltic meteorites. Spinel can be used as a sensitive indicator of petrologic and geochemical processes that occur in its host rock. This paper highlights the role of increasing f O2 (from IW-1 to FMQ+2) in converting a >90% normal spinel to an ~25% magnetite (inverse) spinel, the trajectory of D Vspinel/melt as it relates to the ratio of V3+/V4+ in the melt, and the crystal chemical attributes of the spinel that control the intrinsic compatibility of both V3+ and V4+. This work examines the nuances of the V partitioning and provides a crystal chemical basis for understanding Fe3+, Cr, and V substitution into the octahedral sites of spinel. Understanding this interplay is critical for using spinels as both indicators of planetary parentage and reconstructing the redox history of magmatic systems on the terrestrial planets. Three potential examples for this use are provided. In addition, this work helps explain the ubiquitous miscibility gap between spinels with changing ulvospinel contents. [1]: pending:yes

The vanadium titano-magnetite (VTM) iron ore fines of 110–150 μm in diameter were reduced in a transparent quartz fluidized bed by 70%CO-30%H 2 (volume fraction) mixtures. MgO powders served as coating agent to solve sticking problem. Two coating methods were introduced in this experiment: high temperature injection method and briquetting→oxidizing roast→crushing method. According to the experimental results, the minimum effective coating amount of MgO was 0.1 mass%. The metallization ratio (MR) of the product rose from around 58% to above 90% with the above treatments. To investigate the sticking mechanism of fine ore, the morphology evolution was investigated. Instead of iron whiskers, an interlaced fibrous porous surface formed. The ulvospinel (2FeO · TiO 2 ) in VTM is more difficult to be reduced than FeO according to thermodynamic calculation. XRD results showed that MgO diffused into Fe 2 O 3 lattice before forming pleonaste (MgO · Fe 2 O 3 ) during oxidizing roast at 1273 K. The melting point of the pleonaste is 1986 K and that made contribution to prevent the sticking problem.

The Kovdor phoscorite-carbonatite ore-pipe rocks form a natural series, where apatite and magnetite first gradually increase due to the presence of earlier crystallizing forsterite in the pipe marginal zone and then decrease as a result of carbonate development in the axial zone. In all lithologies, magnetite grains contain (oxy)exsolution inclusions of comparatively earlier ilmenite group minerals and/or later spinel, and their relationship reflects the concentric zonation of the pipe. The temperature and oxygen fugacity of titanomagnetite oxy-exsolution decreases in the natural rock sequence from about 500 °C to about 300 °C and from NNO + 1 to NNO − 3 (NNO is Ni-NiO oxygen fugacity buffer), with a secondary positive maximum for vein calcite carbonatite. Exsolution spinel forms spherical grains, octahedral crystals, six-beam and eight-beam skeletal crystals co-oriented with host magnetite. The ilmenite group minerals occur as lamellae oriented along {111} and {100} planes of oxy-exsolved magnetite. The kinetics of inclusion growth depends mainly on the diffusivity of cations in magnetite: their comparatively low diffusivities in phoscorite and carbonatites of the ore-pipe internal part cause size-independent growth of exsolution inclusions; while higher diffusivities of cations in surrounding rocks, marginal forsterite-rich phoscorite and vein calcite carbonatite result in size-dependent growth of inclusions.

Titanomagnetites (TMs) [pseudobinary (1 - x)Fe 3 O 4 · xFe 2 TiO 4 oxides, where, e.g., TM75 corresponds to x-0.75] are magnetic minerals with a spinel structure. Ulvospinel (Fe 2 TiO 4 ) and TMs were made using a solid-state synthesis technique, and transmission electron microscopy (TEM) characterization and measurement of the TM samples were performed to further confirm the homogeneity of the samples and cation site occupancies. The Mossbauer spectra in the TMs exhibited an anomalous composition dependence at x=0.95, when fitted with two instead of three quadrupole split doublets. This result was reinforced by the obtained dependence of the recoilless fraction on the composition, which exhibited an extremum at x=0.95.

The solid-state reduction kinetics of pre-oxidized vanadium-titanium magnetite concentrate was studied. The phase and microstructure of the reduction product were characterized by XRD, SEM and EDS methods, based on which the mechanism of the solid-state reduction was investigated. The results showed that using coal as reductant at 950-1100 °C, the solid-state reduction of the pre-oxidized vanadium-titanium magnetite concentrate was controlled by interface chemical reaction and the apparent activation energy was 67.719 kJ/mol. The mineral phase transformation during the reduction process can be described as follows: pre-oxidized vanadium-titanium magnetite concentrate → ulvospinel → ilmenite → FeTi 2 O 5 → (Fe n Ti 1- n )Ti 2 O 5 . M 3 O 5 -type (M can be Fe, Ti, Mg, Mn, etc) solid solutions would be formed during the reduction process of the pre-oxidized vanadium-titanium magnetite concentrate at 1050 °C for 60 min. The poor reducibility of iron in M 3 O 5 solid solutions is the main reason to limit the reduction property of pre-oxidized vanadium-titanium magnetite concentrate.

Using a diamond-anvil cell and synchrotron X-ray diffraction, the compressional behavior of a synthetic ulvospinel (Fe1.94Ti0.03)Ti1.00O4.00 has been investigated up to about 7.05 GPa at 300 K. The pressure–volume data fitted to the second-order Birch–Murnaghan equation of state yield an isothermal bulk modulus (K T ) of 147(4) GPa (K′ T fixed as 4). This value is slightly larger than that previously determined by an ultrasonic pulse echo method (121(2) GPa; Syono et al., J Phys Soc Jpn 31:471–476, 1971), but substantially smaller than that recently determined by a synchrotron X-ray diffraction technique (251(3) GPa; Yamanaka et al., Phys Rev B 80:134120, 2009; Am Mineral 98:736–744, 2013). Combined with the K T of magnetite (Fe3O4; ~182(3) GPa), our finding suggests that the bulk modulus of the solid solutions Fe3−x Ti x O4 (0 ≤ x ≤ 1) along the join magnetite–ulvospinel decreases by ~20 %.

Five spinel single-crystal samples within the ulvospinel-qandilite series [(Fe 2− x Mg x )TiO 4 , 0.15 x 2+ and Fe 2+ , while the octahedrally coordinated site (M) is populated by Ti 4+ , Mg 2+ , Fe 2+ , and minor amounts of Fe 3+ . The inverse cation distribution is characterized by parallel substitution of Mg 2+ for Fe 2+ at both the T and M sites along the series. The variation in the unit-cell parameter from 8.527 to 8.495 A is mainly related to the occurrence of Mg 2+ at the M site rather than the T site. In fact, the substitution of Mg 2+ for Fe 2+ yields significant variations in M-O (from 2.045 to 2.034 A) and only limited variation in T-O (from 2.007 to 2.002 A). In conjunction with data from the literature, the present study provide a basis for quantitative analyses of the variation in T Mg-O bond distance from 1.966 A for Mg-poor ulvospinel to 1.990 A for the qandilite end-member.

Titanomagnetite from Fe-Ti-V ores of the Lanjiahuoshan deposit, Panzhihua layered intrusion, Southwest China, was investigated at the nanoscale. The objectives were to establish the composition of exsolution phases and their mutual relationships in order to evaluate the sequence of exsolution among oxide phases, and assess mechanisms of ore formation during magma emplacement. At the micron-scale, titanomagnetite shows crosscutting sets of exsolutions with ilmenite and Al-Mg-Fe-spinel (pleonaste), as well as overprint, both in terms of phase re-equilibration and remobilization of trace elements. Most complex textures were found in titanomagnetite surrounded by ilmenite and this was selected for high-angle annular dark field scanning transmission electron microscopy (HAADF STEM) imaging and STEM energy-dispersive X-ray spectrometry (EDS) spot analysis and mapping on a thin foil prepared in situ on a focused ion beam scanning electron microscope platform. Titanomagnetite revealed two sequential sets of exsolutions, {111} crosscutting {100}, which are associated with changes in phase speciation and trace element distribution patterns. Qandilite is the dominant spinel phase inside titanomagnetite, magnesioferrite is also identified. In contrast, Fe-poor, Al-rich, Mg-bearing spinel is present within ilmenite outside the grain. Vanadium enrichment in newly-formed magnetite lamellae is clear evidence for trace element remobilization. This V-rich magnetite shows epitaxial relationships with ilmenite at the contact with titanomagnetite. Two-fold super-structuring in ilmenite is evidence for non-redox re-equilibration between titanomagnetite and ilmenite, supporting published experimental data. In contrast, the transformation of cubic Ti-rich spinel into rhombohedral ilmenite imaged at the nanoscale represents the &ldquo, oxy-exsolution&rdquo, model of titanomagnetite&ndash, ilmenite re-equilibration via formation of a transient ulv&ouml, spinel species. Nanoscale disorder is encountered as vacancy layers in Ti-rich spinel, and lower symmetry in the Fe-poor, Al-Mg phase, suggesting that slow cooling rates can preserve small-scale phase equilibration. The cooling history of titanomagnetite ore can be reconstructed as three distinct stages, concordant with published models for the magma plumbing system: equilibrium crystallization of Al-rich, Mg-bearing titanomagnetite from cumulus melts at ~55 km, with initial exsolutions occurring above 800 &deg, C at moderate fO2 conditions (Stage 1), crosscutting {111} exsolutions resulting in formation of qandilite, attributable to temperature increase due to emplacement of another batch of melt affecting the interstitial cumulus during uplift. Formation of 2-fold superstructure ilmenite + V-rich magnetite exsolution pairs representing non-redox equilibration indicates resetting of the cooling path at this stage (Stage 2), and ilmenite formation from pre-existing Ti-rich spinel and ulv&ouml, spinel, illustrative of redox-driven cooling paths at &lt, 10 km (Stage 3). HAADF STEM provides direct imaging of atomic arrangements, allowing recognition of processes not recognizable at the micron-scale, and can thus be used to constrain exsolution models during ore formation.

A single-crystal neutron diffraction study of a synthetic ulvospinel sample of composition Fe 3+ 0.40 Fe 2+ 1.80 Ti 0.80 O 4 was performed to investigate the static positional disorder at the octahedrally coordinated M site. Anisotropic structural refinement was performed in the space group Fd 3 m against neutron Laue diffraction data collected at 298 K from two millimetric-sized crystals. Initial structure refinements were conducted with Fe and Ti sharing the M site (at 1/2, 1/2, 1/2), and their partial site occupancy was refined. The tetrahedrally coordinated T site (at 1/8, 1/8, 1/8) was modeled as fully occupied by Fe. For both crystals, the final R 1 index was about 3% for 9 refined parameters and 129 unique reflections, with no significant residuals. As the atomic displacement factors obtained were anomalously high, according to the previous experimental findings, F obs - and ( F obs – F cal )-difference Fourier maps of the nuclear density were generated. Fourier maps showed a significant minimum located out-of-center of the M site, and indicating a displacement of the Ti 4+ from the center of the octahedron. A further test refinement was successfully conducted with two mutually exclusive sites: M Ti out-of-center (at 0.49, 0.49, 0.49) and M Fe on the center (at 1/2, 1/2, 1/2). The resulting displacement of Ti from the octahedral center appears to be shorter than 0.15 A. Using bond-valence theory, the out-of-center distortion of M Ti 4+ is interpreted as a result of intrinsic distortions in the ulvospinel structure. The potential implication of the octahedral distortion on the behavior of ulvospinel at non-ambient conditions is discussed.

Kudryavtsevaite, ideally Na3MgFe3+Ti4O12, is a new mineral from kimberlitic rocks of the Orapa area, Botswana. It occurs as rare prismatic crystals, up to 100 μm m across, associated with Mg-rich ilmenite, freudenbergite and ulvöspinel. Kudryavtsevaite is opaque with a vitreous lustre and shows a black streak. It is brittle; the Vickers hardness (VHN100) is 901 kg mm−2 (range: 876–925) (Mohs hardness ∼6). In reflected light, kudryavtsevaite is moderately bireflectant and very weakly pleochroic from dark grey to a slightly bluish grey. Under crossed polars, it is very weakly anisotropic with greyish-bluish rotation tints. Internal reflections are absent. Reflectance values (%), Rmin and Rmax, are: 21.3, 25.4 (471.1 nm), 20.6, 24.1 (548.3 nm), 20.0, 23.5 (586.6 nm) and 19.1, 22.4 (652.3 nm).Kudryavtsevaite is orthorhombic, space group Pnma, with a = 27.714(1), b = 2.9881(3), c = 11.3564(6) Å, V = 940.5(1) Å3, and Z = 4. The crystal structure [R1 = 0.0168 for 819 reflections with I > 2σ(I)] consists of edge-sharing and corner-sharing chains composed of Mg, Fe3+ and Ti atoms coordinated by six atoms of oxygen and running along the b axis, with Na filling the tunnels formed by the chains. The eight strongest powder-diffraction lines [d in Å (I/I0) (hkl)] are: 7.17 (100) (301), 4.84 (70) (302), 2.973 (35) (901), 2.841 (50) (004), 2.706 (50) (902), 2.541 (50) (312), 2.450 (70) (611), and 2.296 (45) (612). The average results of 12 electron microprobe analyses gave (wt.%): Na2O 16.46(15), CaO 1.01(3), MgO 5.31(5), Fe2O3 22.24(32), Cr2O3 1.05(6), Al2O3 0.03(2), TiO2 53.81(50), total 99.91, corresponding to the empirical formula (Na2.89Ca0.10)Σ2.99(Ti3.67Fe1.523+Mg0.72Cr0.08)Σ5.99O12, or ideally Na3MgFe3+Ti4O12.The new mineral has been approved by the IMA-CNMNC and named for Galina Kudryavtseva (1947–2006), a well known Russian mineralogist and founder of the Diamond Mineralogy Laboratory and scientific school for investigation of diamond mineralogy and geochemistry at the Lomonosov State University in Moscow, Russia.

SummaryThe reliability and utility of diffuse reflectance spectra are briefly but critically reviewed. The results of measurements of diffuse reflectance over the wavelength range 200 < λ < 2500 nm are reported for wüstite, magnetite, hematite, maghemite, ilmenite, ulvöspinel, and α-FeO · OH (goethite), β-FeO 7sd OH, γ-FeO · OH (lepidocrocite), and δ-FeO · OH. The spectra have been assigned by reference to simplified molecular-orbital energy-level diagrams derived from recent SCF-Xα calculations.The specular reflectances reported in the Quantitative Data File (Henry, 1977) are related to the diffuse reflectance spectra in a rational way. Minerals that absorb strongly throughout the visible display little dispersion of specular reflectance, and their powders are dark (wüstite, magnetite, ilmenite, ulvöspinel); those that absorb much more strongly in the near ultraviolet than in the visible have specular reflectances that decrease monotonically from blue to red according to a simple dispersion relation derived by combining the Sellmeier dispersion and Fresnel reflexion equations; their powders are strongly coloured (hematite, maghemite, lepidocrocite, goethite) and their optical anisotropy is closely related to crystal structure.

Extraterrestrial (ET) noble gases (helium and neon) in 35 sediment samples from Central Pacific core LL-44 GPC-3 demonstrate the variable flux of interplanetary dust particles (IDPs) and major meteorite impacts over the past 70 Ma (21–72 Ma). Spinel mineralogical and chemical compositions clearly distinguish major impact events from the continuous flux of IDPs, including the well-established Cretaceous/Tertiary (K/T) and late Eocene (E/O) impact boundaries. No spinel grains with chemical or mineralogical evidence of a distinctly ET origin were found in an extensive survey of ‘background’ samples (i.e. non E/O or K/T boundary) suggesting that either the carrier grains for ET noble gas occur within the Fe–Ti oxide mineral fraction observed in this study (found to include ilmenite and ulvospinel) or are too small for identification by SEM. The presence of ilmenite and ulvospinel suggest lunar regolith is a potential source for ET noble gas-rich particles. Noble gas analysis on both the EMF (extractable magnetic fraction) and the Bulk minus EMF (Bulk − EMF) show that the He and Ne compositions are consistent with partially degassed noble gas signatures of zero-age magnetic grains (Z-MAG) and stratospheric interplanetary dust particles (IDPs). Conclusive evidence for a ‘planetary’ (Ne-A) noble gas signature is found only in the bulk sediments at the K/T boundary, although all GPC-3 K/T fractions (Bulk, EMF, and HF Digestion) plot along a mixing line between planetary (Ne-A) and solar wind (SW). Spinels from major impact boundaries (K/T; E/O) exhibit dendritic texture and elevated [Ni], consistent with previous reports. In contrast to the otherwise consistent [3He] signal from IDPs, the [3He] at the known impact boundaries (K/T and E/O) actually decreases. These anomalously low [3He] are accompanied by significantly elevated [Ne] and significantly lower (3He/20Ne)solar ratios (∼10× lower) produced by both preferentially degassing of He relative to Ne at times of increased flux of larger ET material. Degassed (“degassed-He/enriched-Ne profile”) noble gas characteristics occur in two sample intervals that do not correspond to any known impact events (47 and 71 Ma), explained by an influx of larger particles. SEM analysis of the 47 Ma sample shows spinels with dendritic textures, but without distinctive markers of large meteorite impacts (e.g. elevated Ni). Particle size increases and degassed signatures may be caused by major bolides, micrometeorites, comet showers; or simply a flux of larger IDPs, potentially with a different source.

This paper provides details of the trace element and total organic carbon (TOC) content of the Lower Callovian Kellaways Sand. Heavy metals are associated with mineral phases such as pyrite, iron and manganese oxyhydroxides, organic matter and clay minerals, and correlations are varied. Using a multi-disciplinary approach and geochemical comparisons it has been shown that the Kellaways Sand is particularly enriched in Cr. Cr concentration data suggest two separate components, one bound with Ni and MnO, and the other occurring as an accessory resistate phase Fe–Ti–Cr oxide (ulvospinel) with up to 4.7 wt% Cr 2 O 3 . The closest correlations between matrices are Zn and Ni with Fe 2 O 3 ; V, Ni, Rb and Ga with MnO, MgO and K 2 O; Ni and MnO with TOC; and Cd with Zn. Average concentrations for trace elements and TOC are generally enriched in both the Oxford and Kellaways clays. Variable concentrations of SO 4 in associated groundwaters indicate that oxidation of FeS 2 influences the ranges and concentrations of trace elements observed through Eh and pH controlled adsorption or desorption reactions. The natural and variable concentrations of the metals that also occur in associated groundwaters (including Hg, Cd, Ni, As and Pb) have important implications for the associated, risk-based hydrogeological assessments completed for landfill sites contained within the Oxford Clay, and affect the choice of priority determinants significantly for the monitoring control and trigger levels.

We report in situ Raman spectroscopic studies of ulvospinel in a diamond-anvil cell under hydrostatic conditions up to 57 GPa at room temperature. Two modes near 493 and 681 cm −1 are observed clearly at 1 GPa. In the cubic spinel structure, the lower frequency peak can be assigned to a mode of F 2 g symmetry and the higher frequency peak can be assigned to a mode with A 1 g symmetry. The remaining three modes could not be observed unambiguously in the measurements, although there are five Raman-active modes ( A 1 g + E g +3 F 2 g ) in the Fd 3 m space group of the spinel structure according to factor group analysis. The peak positions and shapes in the Raman spectra agree well with those measured under ambient conditions. With increasing pressure, the frequencies of the A 1 g and F 2 g modes increase continuously up to 9 GPa with pressure derivatives of 2.5 and 2.1 cm −1 /GPa, respectively. There is no obvious degradation of crystal symmetry or structural change observed within this pressure range. Upon increasing pressure to ~20 GPa, the F 2 g mode splits into B 1 g + E g modes, and then into B 1 g + B 2 g + B 3 g modes. The intensities of the Raman bands gradually decrease due to the tetragonal-orthorhombic phase transition. This mode completely disappears at a pressure of 29 GPa. The most striking characteristic of the Raman spectrum of ulvospinel is that compression leads to the extinction of the Raman-active mode derived from F 2 g symmetry. Only one peak resulting from the A 1 g mode can be observed continuously up to 57 GPa. The peak shift derived from the A 1 g mode and its full-width at half maximum (FWHM) values suggests another phase transition occurring around 30 GPa. The Raman spectrum of ulvospinel is in good agreement with the spectra of ZnCr 2 O 4 and ZnFe 2 O 4 spinels.

SUMMARY Active high-temperature (>150 °C) geothermal areas like the Krafla caldera, NE-Iceland, often show distinct magnetic lows in aeromagnetic anomaly maps suggesting a destruction of magnetic minerals by hydrothermal activity. The main alteration processes in such an environment are low-temperature oxidation (

Magnetite and hematite are common minerals in a range of mineral deposit types. These minerals form partial to complete solid solutions with magnetite, chromite, and spinel series, and ulvospinel as a result of divalent, trivalent, and tetravalent cation substitutions. Electron microprobe analyses of minor and trace elements in magnetite and hematite from a range of mineral deposit types (iron oxide-copper-gold (IOCG), Kiruna apatite–magnetite, banded iron formation (BIF), porphyry Cu, Fe-Cu skarn, Fe-Ti, V, Cr, Ni-Cu-PGE, Cu-Zn-Pb volcanogenic massive sulfide (VMS) and Archean Au-Cu porphyry and Opemiska Cu veins) show compositional differences that can be related to deposit types, and are used to construct discriminant diagrams that separate different styles of mineralization. The Ni + Cr vs. Si + Mg diagram can be used to isolate Ni-Cu-PGE, and Cr deposits from other deposit types. Similarly, the Al/(Zn + Ca) vs. Cu/(Si + Ca) diagram can be used to separate Cu-Zn-Pb VMS deposits from other deposit types. Samples plotting outside the Ni-Cu-PGE and Cu-Zn-Pb VMS fields are discriminated using the Ni/(Cr + Mn) vs. Ti + V or Ca + Al + Mn vs. Ti + V diagrams that discriminate for IOCG, Kiruna, porphyry Cu, BIF, skarn, Fe-Ti, and V deposits.

Silicate-oxide equilibria (abbreviated as QUIlF) have proven to be very powerful tools for reconstructing the temperature and oxygen fugacity evolution of magmatic systems containing magnetite and ilmenite with olivine, quartz, or pyroxenes. In this paper, we extend these QUIlF equilibria to include rocks where silica activity is controlled by equilibria between feldspars and feldspathoids. We present data on the orthomagmatic assemblage of titanomagnetite + ilmenite + feldspar + nepheline + compositionally variable olivine, which we call AUNIlF: \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[{NaAlSi\_{3}O\_{8}\_{Albite}^{}}\ +\ {4Fe\_{2}TiO\_{4}\_{Ulv{\o}spinel}^{}}\ =\ {NaAlSiO\_{4}\_{Nepheline}^{}}\ +\ {4FeTiO\_{3}\_{Ilmenite}^{}}\ +\ {2Fe\_{2}SiO\_{4}_{Fayalite}^{}}\] \end{document} The AUNIlF reference curve (with unit activities for albite, nepheline, and fayalite) is stable at oxygen fugacities ≥2 log units below the QUIlF surface at temperatures of about 700 to 800 °C, temperatures typical of late-magmatic stages. At temperatures > ~800 °C, the AUNIlF reference assemblage would only be stable at unrealistically low f O2 conditions more than 5 log units below FMQ (where FMQ is the fayalite-magnetite-quartz buffer), which explains the rarity or absence of orthomagmatic AUNIlF assemblages. We determine the most reduced conditions indicated by displaced AUNIlF assemblage from Mont Saint-Hilaire (Quebec, Canada) to be ΔFMQ = −1.15 at ~800 °C (olivine is Fa67 and a SiO2 = 0.41) and conclude that AUNIlF assemblages involving pure fayalite do not stably occur in terrestrial magmatic systems. The stability field of naturally occurring AUNIlF assemblages is a function of albite, nepheline, and olivine compositions and is controlled by the ratio of silica activity to fayalite activity ( a SiO2/ a Fa). At values higher than ~0.77 for a SiO2/ a Fa, olivine is Fa < ~70 when silica activity is buffered by the nepheline-albite equilibrium. In these situations, AUNIlF is stable at oxygen fugacities ≥ −1.15 (ΔFMQ). At values below a SiO2/ a Fa ~0.77, the AUNIlF equilibrium is shifted to lower oxygen fugacities and ilmenite becomes unstable relative to ulvospinel. Analogous to the construction and application of AUNIlF, a QUIlF-type reaction curve for potassic systems (KULIlF) involving leucite and alkali feldspar is presented and applied to naturally occurring assemblages. Potassic rocks invariably crystallize forsteritic olivine in the presence of ilmenite and magnetite, reflecting higher oxygen fugacities during crystallization than their sodic counterparts. As a result of low fayalite component in olivine, the a SiO2/ a Fa ratio becomes ≥4 in assemblages of potassic systems consisting of alkali feldspar, magnetite, leucite, ilmenite, and olivine.

The titanomagnetite of the Lac Dor&eacute, Complex, an Archean layered intrusion that is located in the Abitibi greenstone belt in Qu&eacute, bec (Canada), contains a wide variety of exsolution textures, which are the remnants of a complex cooling history. In the present study, we reconstitute the decomposition stages of the original solid solution in order to explain the formation of ilmenite, Al-spinel (hercynite and gahnite), and corundum exsolutions in magnetite. This was conducted through a detailed mineralogical and textural examination and in situ determination of mineral chemistry. Our investigation reveals two discrete types of ilmenite exsolutions, which are ascribed, respectively, to the oxidation of ulv&ouml, spinel at temperatures above and below the magnetite-ulv&ouml, spinel solvus. Exsolutions of Al-spinel result from either a decrease in the solubility of the (FeZn)Al2O4 components upon cooling, or local excesses of Al and Zn due to the removal of ulv&ouml, spinel during the early oxidation. The origin of corundum is ascribed to the oxidation of pre-existing hercynite exsolutions. The trace element composition of the titanomagnetite indicates stratigraphic reversals in Cr, Mg, Co, Ti, and Si and important changes in redox conditions. We interpret this as a direct consequence of a major event of magma chamber replenishment, which strongly influenced the distribution of exsolutions.

The phase composition of the vanadium-containing titanium slags that form upon the reduction smelting of the titanomagnetite concentrate from the Kuranakhsk deposit with an added CaCO3 flux is studied by optical microscopy, X-ray diffraction, and scanning electron microscopy. The laws of formation of the phase composition and the interphase distribution of vanadium and other elements are revealed as a function the CaO and FeO contents in the slags. It is shown that, at low CaO contents (up to 5%), the phase composition of the slags containing 15–30% FeO is mainly represented by spinelides (Al-V-Cr and Al-Ti-V spinels and (Fe,Mg)2TiO4 ulvospinel), anosovite, and glass. When the CaO content in slag increases, titanium is fixed into perovskite. At 17–20% CaO and ≤8.3% FeO in slag, a new crystalline phase, i.e., Ca-Al-V titanate of a complex composition, forms along with perovskite, the Al-V-Cr spinel, anosovite, and glass. Vanadium in the slags is mainly distributed between anosovite, the spinelides, and the Ca-Al-V titanate, and vanadium is absent in the glassy phase.

Composition of chromiferous spinel included in olivines of Mg-rich basalts and gabbros of the Deccan Traps (Gujarat and Western Ghats) are reported here. They vary from Al-rich compo- sitions (Al2O3 = 53 wt.%; Cr#, 100Cr/(Cr + Al) = 12) to Cr-rich compositions (Cr2O3 =5 1 wt.%; Cr# = 84), and from Cr-Al rich compositions towards Cr-rich Ti-magnetite (TiO2 up to 23 wt.%, ulvospinel up to 67 mol.%). The Mg# (100Mg/(Mg + Fe 2+ )) of spinel decreases from 81 to nearly zero. The highest Cr# has been found in the Bushe Fm., Thakurvadi Fm., and some high-Ti basalts of the Pavagadh section, whereas some of the low-Ti basalts of Saurashtra have Al-rich composi- tions typical of spinels found in mid-ocean ridge basalts. The chemical composition of the Deccan Trap spinels is completely different compared to that observed in mantle spinel suites, with very few exceptions. The decreasing Al and increasing Fe and Ti of spinel seems to be mainly the result of decrease of Mg in the locally coexisting melts and favourable cationic substitutions in the lat- tice. There is barely any evidence of general relationships between the composition of the Deccan spinels and inferred mantle sources of the host magmas. Pyroxene inclusions in spinels may wit- ness a high-pressure stage of crystallization, but the possibility of non-equilibrium crystallization, or even magma mixing, cannot be ruled out. Overall, the compositional ranges of chromiferous spinel in the Deccan Traps closely match those observed in the other Large Igneous Provinces having mafic/ultramafic intrusions and mafic magma compositions (e.g., Siberian Traps, Karoo, Emeishan).

Ordering of Fe{sup 3+} and Fe{sup 2+} between octahedral (Oh) and tetrahedral (Td) sites in synthetic members of the magnetite (Fe{sub 3}O{sub 4}) - ulvoespinel (Fe{sub 2}TiO{sub 4}) solid-solution series was determined using Fe L{sub 2,3}-edge X-ray magnetic circular dichroism (XMCD) coupled with electron microprobe and chemical analysis, Ti L-edge spectroscopy, Fe K-edge EXAFS and XANES, Fe{sub 57} Moessbauer spectroscopy, and unit cell parameters. Microprobe analysis, cell edges and chemical FeO determinations showed that the bulk compositions of the samples were stoichiometric magnetite-ulvoespinel solid-solutions. Surface sensitive XMCD showed that the surfaces of these oxide minerals were more sensitive to redox conditions and some samples required re-equilibration with suitable solid-solid buffers. Detailed site-occupancy analysis of these samples gave XMCD-Fe{sup 2+}/Fe{sup 3+} ratios very close to stoichiometric values. L{sub 2,3}-edge spectroscopy showed that Ti{sup 4+} was restricted to Oh sites. XMCD results showed that significant Fe{sup 2+} only entered Td when the Ti content was > 0.40 apfu while Fe{sup 2+} in Oh increased from 1 a.p.f.u in magnetite to a maximum of {approx}1.4 apfu in USP45. As the Ti content increased from this point, the steady increase in Fe{sup 2+} in Td sites was clearly observable in the XMCD spectra, concurrentmore » with a slow decrease in Fe{sup 2+} in Oh sites. Calculated magnetic moments showed a steady decrease from magnetite (4.06 {mu}{sub B}) to USP45 (1.5 {mu}{sub B}) and then a slower decrease towards the value for ulvoespinel (0 {mu}{sub B}). Two of the synthesized samples were also partially maghemitized by re-equilibrating with an oxidizing Ni-NiO buffer and XMCD showed that Fe{sup 2+} oxidation only occurred at Oh sites, with concomitant vacancy formation restricted to this site. This study shows the advantage of using XMCD as a direct measurement of Fe oxidation state in these complex magnetic spinels. These results can be used to rationalize the magnetic properties of titanomagnetites, and their oxidized titanomaghemitized analogues, in Earth's crustal rocks.« less

The V-Ti magnetite layers (lodestone) occur within the layered gabbro-anorthosites-ultramafic rocks emplaced into the migmatitic gneisses close to the high grade Archeaen Sargur supracrustal rocks in the Kurihundi area. The ore petrographic studies of the lodestone reveal the presence of primary Ti-magnetite, ilmenite, ulvospinel, pleonaste, hematite and pyrite, chalcopyrite, pyrrhotite and secondary Ti-maghemite, martite and goethite as well as secondary covellite. These layers contain Ti-magnetite (60%) and ilmenite (30%) with silicates (

Found during the 2004 U.S. Antarctic Search for Meteorites season, LaPaz Icefield (LAP) 04841 represents an addition to the LaPaz lunar basalts suite and brings the total mass collected to 1.93 kg. The presence of FeNi grains, troilite, and the anorthositic composition of plagioclase are evidence for the lunar origin of this meteorite. Pyroxene and olivine Mn/Fe values plot along the trend set for lunar basalts. Analyses of chromite grains provide a V/(Al + Cr) ratio of 1.33 ± 13, translating to an fO2 one log unit below the IW buffer, in accordance with previous fO2 estimates for lunar basalts. Application of the Zr-cooling speedometer, for ilmenite and ulvospinel pairs, gives a cooling rate of 5.2 °C/day, matching previous estimates of cooling rates for the LaPaz lunar meteorites and Apollo mare basalts. Mineral modes and chemistries, as well as trace-element patterns, provide compelling evidence for pairing of this meteorite to others in the LaPaz lunar basalt suite.

Spinel single crystals of 19 compositions along the magnetite-ulvospinel join were synthesized by use of a flux-growth method. To obtain quantitative site populations, the crystals were analyzed by single-crystal X-ray diffraction, electron-microprobe techniques, and Mossbauer spectroscopy. All results were processed by using an optimization model. The unit-cell parameter, oxygen fractional coordinate, and tetrahedral bond length increase with increasing ulvospinel component, whereas the octahedral bond length decreases marginally. These changes result in sigmoidal crystal-chemical relationships consistent with cation substitutions in fully occupied sites. As a first approximation, the Akimoto model T (Fe 1− X 3+ Fe X 2 + ) M (Fe 2+ Fe 1− X 3+ Ti X )O 4 describes the cation substitutions. Deviations from this model can be explained by an electron exchange reaction T Fe 2+ + M Fe 3+ = T Fe 3+ + M Fe 2+ , which causes M Fe 2+ ≠ 1 and T Fe 2+ /Ti ≠ 1. The resultant S-shaped trends may be related to a directional change in the electron exchange reaction at Ti ≈ 0.7 apfu. In general, variations in structural parameters over the whole compositional range can be split into two contributions: (1) a linear variation due to the T Fe 3+ + M Fe 3+ = T Fe 2+ + M Ti 4+ chemical substitution and (2) non-linear variations caused by the internal electron exchange reaction. In accordance with bond-valence theory, strained bonds ascribable to steric effects characterize the structure of magnetite-ulvospinel crystals. To relax the bonds and thereby minimize the internal strain under retained spinel space group symmetry, the electron exchange reaction occurs.

A model for the thermodynamic properties of rhombohedral oxide solid solutions in the system Fe2O3-FeTiO3-MgTiO3-MnTiO3 (containing minor amounts of Al2O3) is presented. The model accounts for temperature and compositionally dependent long-range cation-order and the related high to low symmetry structural phase transition. The model is calibrated from the cation-ordering data of Harrison and others (2000; Harrison and Redfern, 2001) and experimental data on Fe+2Ti ⇔ (Fe+3)2 exchange between rhombohedral oxide and spinel from Lattard and others (2005) and Evans and others (2006). Successful calibration require introduction of an energetic contribution attributed to short-range cation-order, which reduces the configurational entropy of the solid solution. The resultant thermodynamic model for the rhombohedral oxides is internally consistent with the model for spinel solid solutions of Sack and Ghiorso (1991a, 1991b) and with the endmember thermodynamic properties database of Berman (1988); a new model equation for the isobaric heat capacity of ulvospinel (cubic Fe2TiO4) is proposed and values of the enthalpy of formation, −1490.417 kJ/mol, and third law entropy, 184.199 J/K-mol, at 298.15 K and 105 Pa are recommended. The new model forms the basis of a revised FeTi-oxide geothermometer/oxygen barometer, which is applied to a newly compiled dataset of natural two oxide pairs from silicic volcanic rocks. Results are compared to previous formulations with the general conclusion that the new model gives a better estimate of oxidation state for magmas that equilibrated under conditions more oxidizing than the nickel-nickel oxide buffer. Estimates of oxygen fugacity are fairly insensitive to analytical uncertainties in oxide compositions. By contrast, temperature estimates are especially sensitive to analytical error and to the abundances of “minor” constituents. Application of the geothermometer to oxide pairs that grew under conditions where the rhombohedral phase was cation disordered (that is high temperature or at oxygen fugacities greater by about one log10 unit than the nickel-nickel oxide buffer) results in an uncertainty due solely to analytical error of at least 50°C and sometimes as high as 100 °C. Temperature estimates from the new geothermometer can be made using either the Fe+2Ti ⇔ (Fe+3)2 exchange or Fe+2 ⇔ Mg exchange between the two oxides. Comparison of the two temperature estimates provides a means of evaluating the internal consistency of coexisting oxide compositions and assessing the extent of disequilibrium. Temperatures calculated from the new model are found to be consistent with experimental phase relations for the stability of cummingtonite in silicic volcanics. Other petrologic constraints on derived temperatures are examined including limits on the width of the miscibility gap and the development of self-reversed remanent magnetization in the rhombohedral series. Software that implements the new thermodynamic model and the two-oxide geothermometer/oxygen barometer is available from http://www.ofm-research.org/.

We have performed five separate sets of experiments to elucidate the effects of magnetite, ulvospinel-magnetite solid solution, and pyrrhotite crystallization on the budgets of Au, Cu, and Ag at magmatic conditions. The experiments were done in both hydrous and anhydrous assemblages at temperatures between 800 and 1050 °C, pressures from ambient to 140 MPa, log f O2 from NNO-0.25 to NNO, and log f S2 from −1.5 to −3.0. Nernst-type partition coefficients (±1σ) at 800 °C in a water-saturated assemblage are D AgMt/melt = 2 × 10−4 ± 2 × 10−9, D CuMt/melt = 0.82 ± 0.69, D CuUsp/melt = 26 ± 17, D AuUsp/melt = 50 ± 31, D CuPo/melt = 174 ± 25. Nernst-type partition coefficients (±1σ) at 1050 °C in an anhydrous assemblage are D CuPo/melt ≥ 200, D AgPo/melt = 58 ± 8, D AuPo/melt = 120 ± 50. The calculated values for D AuUsp/melt and D CuUsp/melt indicate that the addition of Ti to magnetite increases significantly the Au- and Cu-scavenging potential of ulvospinel relative to end-member magnetite. Partition coefficients for Cu and Au between pyrrhotite and melt indicate that a temperature change from 1050 to 800 °C in an anhydrous and hydrous assemblage, respectively, results in no observable change in Cu partitioning. The calculated partition coefficients are used to model the effect of crystal fractionation on the concentrations of Ag, Cu, and Au. Model results suggest that the co-crystallization of magnetite and pyrrhotite sequester no more than 2% Ag, 7% Cu, and 37% Au from the melt over the first 25% solidification. If the melt reaches volatile saturation after 25% crystallization, the presence of end-member magnetite and pyrrhotite do not appear to inhibit the Cu-, Au-, and Ag-ore potential of the magma. Ulvospinel-magnetite, however, may reduce the Au concentration in the melt by approximately one-third relative to its initial value that decreases the overall Au available to partition into the volatile phase.

We examined the mode of occurrence, pattern of zoning and composition of magnetite and associated spinel-group minerals in three types of calciocarbonatite from the Kerimasi volcano, in Tanzania. In all samples, magnetite is one of the earliest phases to have crystallized, and shows an appreciable compositional variation. The majority of compositions correspond to magnetite with low to moderate proportions of magnesioferrite and ulvospinel components (10–28 and 2–28 mol.%, respectively) and 2 O 4 ). The two trace elements consistently present in appreciable amounts are V (400–2000 ppm) and Zn (700–3300 ppm); the abundances of other trace elements are much lower and very variable (≤15 ppm Cr, 170 ppm Ni, 220 ppm Co, 490 ppm Zr, 14 ppm Hf, 95 ppm Nb, 3 ppm Ta, and 80 ppm Ga). Magnetite is thus a minor host of Zr, Hf, Nb and Ta in carbonatites. The composition of magnetite crystallizing from carbonatitic magma evolves by becoming depleted in Mg and Ti, whereas its Al content inversely correlates with the V content and, thus, is sensitive to variations in f (O 2 ). The compatibility of V is interpreted to decrease, and that of Mn to increase, with increasing f (O 2 ). Covariation between the Mn and Zn contents suggests that the partitioning behavior of Zn is controlled by the coupled substitution Zn 2+ Mn 3+ Fe 2+ −1 Fe 3+ −1 . The Mg–Ti depletion trend is accompanied by a decrease in Zr and Ta contents at constant or decreasing levels of Nb and Hf, which has implications for the partitioning behavior of high-field-strength elements in carbonate melts. In addition to the magmatic evolutionary trend, the Kerimasi magnetite exhibits a previously unrecognized trend arising from a reaction of the magnetite with the carbonatitic magma. This trend involves enrichment of the peripheral parts of magnetite crystals in Mg, Al, Mn, Zr and Nb, and their mantling by Fe-rich spinel. This trend requires that a (Mg 2+ ) and a (Al 3+ ) in the magma increase with evolution, whereas a (SiO 2 ) remains low to impede the precipitation of Mg–Al silicates.

Spinel single crystals (up to 4 mm in size) of eight compositions along the FeFe 2 O 4 -Fe 2 TiO 4 solid-solution join, with more than 75 mol% ulvospinel, were synthesized by use of a flux-growth method. The crystals were characterized by electron microprobe and Mossbauer spectroscopy. Results demonstrated that these ulvospinels are statistically stoichiometric. The atomic proportions of Ti 4+ and Fe 2+ progressively increase from 0.75 to 0.94 and from 1.75 to 1.94 apfu, respectively. Concomitantly the Fe 3+ content decreases from 0.49 to 0.13 apfu. Consequently, the cation substitutions are restricted to the ideal classic substitution 2Fe 3+ ↔ Fe 2+ + Ti 4+ . An average equilibrium temperature from coexisting spinel-ilmenite pairs of about 950 °C was estimated using the QUILF95 and Ghiorso-Sack models. In contrast to previous studies based on non-stoichiometric samples sintered at higher temperatures, the present stoichiometric ulvospinel samples were grown from a melt under moderate temperatures. This fact indicates that the formation of vacancies is related to high-equilibration temperatures or growth mechanisms, whereas natural ulvospinel may very well be stoichiometric under normal magmatic conditions.

Grains ofrhonite have been discovered in magmatic inclusions in augite grains of the lunar regolith from Mare Crisium, returned to Earth by the Russian Luna 24 spacecraft. These rhonite grains are up to 8 μm long, pleochroic from tan to dark brown, and associated with ulvospinel and silica-rich glass. Electron microprobe analysis gives a composition near end-member ferroan rhonite: (Ca 1.9 Mn 0.0 Na 0.1 ) (Fe 2+ 4.5 Mg 0.1 Al 0.3 Cr 0.0 )Ti 1.0 (Si 4 . 0 Al 2.0 )O 20 . The Raman spectrum of these grains is like those of terrestrial rhonites, and distinct from titanian amphiboles. Compositionally, rhonite plus silica plus water or halogens (F, Cl) is equivalent to titanian amphibole plus pyroxene, so the presence ofrhonite in lunar basaltic rock is consistent with the known low abundance of volatiles in the Moon. When calibrated, mineral reactions involving rhonite and titanian amphibole may provide quantitative constraints on fugacities of water, F, and Cl in basaltic magmas from the Moon and other planetary bodies.

Results of microprobe analysis of titanomagnetites and hemoilmenites from Cenozoic basalts of Mongolia and Iceland, Eastern Siberia Permo-Triassic traps (the Norilsk borehole), and Proterozoic and Paleozoic dike basaltoids on the White Sea coast of the Kandalaksha Gulf (Por’ya Bay), as well as data on titanomagnetites of Primorski Krai basalts [Shcheka et al., 1980], are used to examine specific features of the implantation of impurity atoms into solid solutions with various concentrations of the ulvospinel component.

The Ulvo Gabbro Complex consists of alkali-olivine basaltic circular bodies ∼30–80 km in diameter. These intrusions were emplaced at shallow depths (∼3 km) as thin sheets (∼300 m). Among other things, the gabbroic cumulates of the complex display: modal layering, grain-size variations, trough structures, and slump structures. The crystallization sequence is olivine+plagioclase, ulvospinel, clinopyroxene, and apatite. A nearly continuous exposure across one of these intrusions, the Norra Ulvon gabbro, is subdivided into: a Lower Zone (LZ), a Rhythmically Layered Zone (RZ) and an Upper Zone (UZ). LZ and RZ were formed at the floor, while UZ grew from the roof downward. Major-element variations in the cores of the cumulus minerals define fractionation trends from the base of the intrusion to the RZ-UZ boundary interpreted as a “sandwich horizon”. Modeling suggests that a significant amount of crystallized interstitial liquid is required to produce the observed stratigraphic relations. Our results suggest that the small size and shallow emplacement depth of the intrusions of the Ulvo Gabbro Complex helped to preserve evidence of primary accumulation processes. However, it is also clear that despite the limited time available postcumulus processes such as diffusional homogenization and compaction of some grains were important.