Hingganite-(Ce), Ce₂[]Be₂Si₂O₈(OH)₂ or CeBeSiO₄(OH), occurs in a pegmatite at Hirukawa-mura, Gifu Prefecture, Japan. It is pale tan in color, vitreous and transparent, with a white streak. The Mohs hardness is 5-6, and the calculated density is 4.28 g/cm³. An electron microprobe analysis gave the empirical formula (Ce_0.82La_0.32Nd_0.13Pr_0.06Y_0.03Sm_0.01 Gd_0.002Dy_0.001Ca_0.60)Σ_1.97Fe_0.24Be_2.02Si_2.02O_8.20(OH)_1.52. The lattice parameters were determined by the Rietveld method coupled with the imaging plate Gandolfi XRD data: SG = P2₁/a, a = 9.8973(11), b = 7.6282(8), c = 4.7505(6) Å, β = 90.416(8)°, V = 358.64(7) ų, and Z = 2 for Ce₂[]Be₂Si₂O₈(OH)₂. The three strongest lines in the powder XRD pattern [d(Å), I/I₀, hkl] are (3.14, 86, 211 and 211), (2.85, 100, 121 and 121) and (2.56, 46, 311, 221 and 311). Hingganite-(Ce) is a new member of the gadolinite-datolite group of minerals. It is the Ce-analogue of hingganite-(Y), and ideally, is the Fe-free analogue of gadolinite-(Ce). A single crystal of hingganite-(Y) from the same locality showed a chemical composition of (Y_1.21Ca_0.28Nd_0.06Gd_0.06Dy_0.06Yb_0.05Er_0.04Ce_0.04Sm_0.03Ho_0.03Lu_0.02Pr_0.01Tm_0.01Tb_0.01La_0.01)Σ_1.92Fe_0.23Be_2.07Si_2.07O_8.19(OH)_1.55. A negative anomaly was observed for Ho in the lanthanide distribution pattern of hingganite-(Y). A single crystal structure refinement of hingganite-(Y) converged to R = 0.0329 with the lattice parameters of: a = 9.8830(16), b = 7.6091(9), c = 4.7423(9) Å, β = 90.342(14)°, and V = 356.62(10) ų.

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X-ray diffraction intensities were measured for single-crystal, spinel structure ringwoodite (γ-Mg_1.97SiH_0.03O₄) at pressures up to 7.9 GPa in the BL-10A synchrotron beam line of the Photon Factory. The isothermal bulk modulus calculated using the Birch-Murnaghan equation of state assuming K_T’ = 4 was K_T = 184(6) GPa. The difference between this result and the value for anhydrous ringwoodite is not significant within the limit of experimental error due to a minimal H₂O content. The oxygen positional parameter u was revealed to increase significantly with pressure, approaching the ideal value of 1/4 for cubic closest packing. The mean Si-O distance remained almost constant up to 7.9 GPa, with compression of the unit cell occurring in proportion to that of the MO₆ octahedron.

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The Rokko Mountains consist primarily of late Cretaceous granitic rocks. These are recognized as Nunobiki Granodiorite, Yahatadani Granite, Dobashi Quartz Diorite, and Rokko Granite. Based on grain size and texture, the Nunobiki Granodiorite is subdivided into a porphyritic and equigranular facies, whereas the vertically zoned Rokko Granite pluton is differentiated into fine-grained, medium -to coarse-grained, and micrographic facies. The fine-grained facies occurs at high altitude, and the medium -to coarse-grained granite is found at an intermediate to low altitude within the Rokko Mountains. The micrographic facies intrudes both of these varieties. The granitic rocks were analyzed for trace and rare earth elements and mineral composition. The fine and micrographic facies of the Rokko Granite have higher Rb, Nb, and Y, and lower Sr and Zr when compared with the medium -to coarse-grained facies equivalents and have strong negative Eu anomalies in chondrite normalized REE patterns. In the Rokko Granite the Rb content decreases with an increase in Sr. Whole-rock chemistry indicates that the Rokko granitic magma formed a zoned magma chamber due to plagioclase crystal fractionation. Results of the least-square mass balance calculation for the major elements are in good agreement with the analysis data for Eu. The Rokko granitic magma was rich in the volatile components, SiO₂, and K₂O at the top of the magma chamber, whereas the base was more intermediate in chemical composition. The fine-grained facies has a low An content, and biotite in the fine and micrographic facies is rich in Fe and poor in Mg. These chemical characteristics indicate that two facies are formed from a more differentiated magma than the medium -to coarse-grained facies.

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Pyrites from five localities were oxidized with dissolved oxygen (DO) in acidic solution at 298 K. The objective of this study was to compare the oxidation rates of pyrite samples with different impurity contents. Initial conditions were a solution pH adjusted to approximately 4 and air saturation. DO, Fe²⁺, Fe(III) (as Fe³⁺ and Fe(III)-OH complexes), and SO₄²⁻ concentrations in the experimental solutions were periodically measured along with pH and redox potential (Eh). On the basis of the relationship between DO concentration and reaction duration, the rate laws for the oxidation of the pyrites were obtained. The rate laws differed for the various pyrites and can be expressed as follows:

      Rate = −(1/f_DO) (V/A) (d[DO]/dt) = k[DO]ⁿ

where the unit of oxidation rate is mol m⁻² s⁻¹, f_DO is the stoichiometric coefficient for DO in the pyrite oxidation reaction, V is the volume (L) of the solution, A is the total surface area (m²) of pyrite, [DO] is the DO concentration (mol L⁻¹), t is time (s), k is a rate constant at pH ∼ 4, and n is the reaction order (0.5-1). The differences in the rate laws were due to differences in the oxidation rates of Fe²⁺ during the oxidation of the pyrites, and the differences in the oxidation rates of Fe²⁺ were related to the occurrence of impurities in the pyrites. Oxidation of Fe²⁺ was accelerated by increases in the total amount of impurities in the pyrite. Precipitation of the Fe³⁺ produced during the reaction was promoted by increased amounts of arsenic in the pyrites.

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We report high-Na gedrite (sodicgedrite) with up to 3.1 wt% Na₂O (∼ 0.81 Na^A pfu) in ultrahigh-temperature (UHT) Mg-Al-rich rocks from the northern margin of the Pan-African Madurai Block along the Palghat-Cauvery Shear Zone system, southern India. An amount of Na^A of the gedrite increases with increasing Al^IV. The sum of Na^A and Al^IV also increases linearly with decreasing Si suggesting the substitution of Na^AAl^IV ↔ Si. The negative correlation between Fe + Mg + Si and Al is probably due to the tschermak substitution ((Fe,Mg)^VISi^IV ↔ Al^VIAl^IV). The relatively coarse-grained nature and porphyroblastic occurrence of the sodicgedrite suggest that the mineral recrystallized at the peak UHT metamorphism. In contrast, retrograde gedrite with cordierite is less sodic with 1.1-1.6 wt% Na₂O (Na^A = 0.24-0.35 pfu). Our data suggest that high-Na content in gedrite is a possible indicator of UHT metamorphism.

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The Al-rich variety of perrierite has been found in sapphirine-quartz-bearing ultrahigh-temperature (UHT) gneiss from Mt. Riiser-Larsen in the Napier Complex, East Antarctica. The major constituents of this perrierite-bearing gneiss are quartz, orthopyroxene, sapphirine, and osumilite, with minor biotite, K-feldspar, and cordierite. Perrierite, zircon, monazite, and rutile are accessory phases. The perrierite grains have diameters in the range 50-500 μm and are pale brownish-orange in color. They have relatively high Al₂O₃ and MgO content, and low CaO and FeO content compared to other reported perrierite compositions. [The approximate formula is (La_0.7Ce_1.6Pr_0.2Nd_0.6Sm_0.1Y_0.3Ca_0.3)(Fe_0.5Mg_0.7Al_1.0)(Ti_2.0Al_1.0)Si_4.0O₂₂]. The perrierite yields U-Th-Pb chemical ages (ca. 2460 ± 110 Ma) and chondrite-normalized rare earth element (REE) patterns (Ce_n/Dy_n = 10-16) that are similar to those of monazite (ca. 2450 ± 30 Ma and Ce_n/Dy_n = 12-24). Both perrierite and monazite may have been stable accessory phases during UHT metamorphism, and the occurrence of perrierite in this sample is possibly controlled by the relatively low phosphorous and high REE and titanium contents.

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Several tens of float blocks of jadeite-quartz-K-feldspar rocks were recently found in and around serpentinite masses in the Kamuikotan Gorge area of the central Kamuikotan zone, Japan. They consist mainly of jadeite (Jd_95-100), quartz, K-feldspar, phengite, and lawsonite. Two stages of metamorphism are recognized. The metamorphic conditions during the first and the second stages are estimated at about 250-350 °C and more than 1.1 GPa, and 200-300 °C and 0.4-0.7 GPa, respectively. The rocks are relatively fine-grained, acidic in composition, and characteristically have many jadeitized pseudomorphs of probable rapakivi feldspar, suggesting a hypabyssal fine-grained granite or granite porphyry origin. K-feldspar-bearing granitic rocks have never been reported from the Kamuikotan zone. The discovery of jadeite-quartz-K-feldspar rocks in the zone provides important information about the source of the metamorphic protoliths. The inference is that these materials formed by the activity of felsic magma, which existed near the trench during Late Jurassic to Cretaceous time.

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Sapphirine + quartz bearing garnet granulite from the Central Zone of the Neoarchean Limpopo Belt contains three categories of fluid inclusions: dominant pseudosecondary inclusions in garnet and plagioclase, secondary inclusions in matrix quartz, and least dominant primary inclusions in the same quartz grains. The melting temperatures of the trapped fluids lie in the range of −58.6 to −56.4 °C. Homogenization of the pseudosecondary inclusions into the liquid phase occurs within the temperature range of +9.1 to +28.4, which correspond to CO₂ densities of 0.72 to 0.87 g/cm³. In contrast, primary inclusions homogenized at +6.1 ± 3.1 °C, which translates into slightly higher densities of 0.87-0.91 g/cm³. The fluid densities, when computed into isochores, indicate entrapment of CO₂ at lower pressure than the peak P-T condition of the rock. The results imply either influx of CO₂-rich fluids during post-peak uplift or density reversal of peak metamorphic carbonic fluid. Lack of aqueous fluid inclusions and abundant pseudosecondary carbonic inclusions in the rock confirmed that low-H₂O activity condition is necessary to form unique sapphirine + quartz assemblage.

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The above PDF file shows errata of Table 2 in the paper entitled “Cation vacancy and possible hydrogen positions in hydrous forsterite, Mg_1.985Si_0.993H_0.06O4, synthesized at 13.5 GPa and 1300 °C” by Yasuhiro KUDOH, Takahiro KURIBAYASHI, Hiroyuki KAGI and Toru INOUE (Vol. 101, no. 5, 265-269, 2006) Wrong:See PDF attached
Right:See PDF attached

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