Showing papers in "Journal of Mineralogical and Petrological Sciences in 2015"

Cs–sorption in weathered biotite from Fukushima granitic soil

Abstract: The sorption characteristics of cesium (Cs) ions into weathered biotite with biotite–vermiculite interstratification collected from weathered granodiorite in Fukushima Prefecture, Japan has been investigated. Both single crystals and crushed powder forms of the weathered biotite were experimentally reacted with 20–2000 ppm CsCl aqueous solutions, and analyzed by powder X–ray diffraction (XRD), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) to examine the distribution of Cs inside the crystals. From the XRD pattern, the proportion of vermiculite unit layers in the weathered biotite was estimated at ~ 12%, with a tendency for segregation, and the whole XRD pattern was explained by the coexistence of biotite and vermiculite packets as well as the interstratified regions. Powder XRD of Cs–sorbed specimens showed that the 14.9 Å peak of the vermiculite packets was weakened at a low Cs concentration in the solution. Single crystals of the weathered biotite with a polished edge–surface were immersed in the CsCl solutions and examined using SEM and high–angular annular dark field (HAADF) imaging in STEM. Cs was not only incorporated in the vicinity of the exposed surface but also penetrated deeply inside the crystals. These analyses and observations revealed the Cs–sorption process in weathered biotite. At first, Cs preferentially replaced specific vermiculite interlayers in the vermiculite packets. With a higher Cs concentration in the solution, the Cs–substituted vermiculite interlayers increased in the vermiculite packets, and vermiculite layers interstratified in biotite also incorporated Cs.

Effect of temperature on the frictional behavior of smectite and illite

Abstract: We performed high–temperature friction experiments to investigate the effect of temperature on the frictional behavior of smectite and illite. Friction coefficients (μ) of these clay minerals increase with increasing temperature as a result of dehydration of absorbed and interstitial water. At a constant normal stress of 60 MPa, μ of Ca–smectite gouge increases from 0.27 at room temperature to 0.67 at 200 °C, and μ of illite gouge increase from 0.53 at room temperature to 0.68 at 200 °C. Velocity dependence of steady–state friction for smectite and illite gouges changes with temperature so that the transition from velocity–strengthening to velocity–weakening behavior occurs at 150 °C at a normal stress of 60 MPa. Temperature at which this change takes place corresponds to the temperature at the updip limit of the seismogenic zone along subducting plates. Thus, the effect of temperature on the frictional behavior of these clay minerals possibly play an important role in controlling the updip limit of subduction thrust earthquakes.

Raman spectroscopic thermometry of carbonaceous material in chondrites: four–band fitting analysis and expansion of lower temperature limit

Abstract: *Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo, Tokyo 113–0033, Japan **Department of Earth and Planetary Science, Graduate School of Environmental Studies, Nagoya University, Nagoya, Aichi 464–8601, Japan ***Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Hongo, Tokyo 113–0033, Japan Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560–0043, Japan

Geochemical behavior of zirconium during Cl–rich fluid or melt infiltration under upper amphibolite facies metamorphism — A case study from Brattnipene, Sør Rondane Mountains, East Antarctica

Abstract: *Department of Geology and Mineralogy, Graduate School of Science, Kyoto University, Kyoto 606–8502, Japan **Graduate School of Environmental Studies, Tohoku University, Sendai 980–9570, Japan ***Department of Geology, Faculty of Science, Niigata University, Niigata 950–2181, Japan Graduate School of Environment and Information Sciences, Yokohama National University, Yokohama 240–8501, Japan Department of Geology, University of Johannesburg, South Africa

Decarbonation and melting in MgCO 3 –SiO 2 system at high temperature and high pressure

Abstract: The decarbonation reaction boundary and the melting temperature in the MgCO3–SiO2 system were investigated up to 26 GPa using a multi–anvil apparatus. It was found that the decarbonation reaction (MgCO3 + SiO2 → MgSiO3 + CO2) occurs below 8 GPa, but it becomes a melting reaction above 8 GPa. The melting system shows a simple eutectic relation. The eutectic point shifts to a higher temperature and more MgCO3–rich composition with increasing pressure. The eutectic temperatures at ~ 9 GPa and ~ 26 GPa were found to be ~ 1700 °C and ~ 2000 °C, respectively. Our results show that magnesite remains stable through the mantle geotherm, at least up to uppermost lower mantle, and that carbon can be transported to the lower mantle as magnesite. If a hot plume brings magnesite back to the upper mantle, it generates carbonatite magma or CO2 fluid.

The mineralogical characterization of argentian cryptomelane from Xiangguang Mn–Ag deposit, North China

Abstract: Argentian cryptomelane as a quite rare variety is determined during the investigation of Mn–Ag ore samples from Xiangguang deposit along the northern margin of North China craton. The mineral observed by a polarizing petrographic microscope involves concentric ring–band, pisolitic and veinlet structures and greyish white color. The scanning electron microscopy reveals a large number of elongated nanocrystals in the forms of nanofibers and nanorods in this densely natural argentian cryptomelane. The specifically chemical features in two samples of XG–C–1 and XG–C–2 of cryptomelane are: (1) (K0.55Na0.08Ca0.06Zn0.04Ag0.03Pb0.02Mg0.01)0.79(Mn7.21Fe0.52Al0.09Si0.09)7.91O16•nH2O; (2) (K0.37Ca0.28Ag0.13Na0.07Mg0.07Zn0.06Cu0.02)1.00(Mn7.01Fe0.40Al0.39Si0.03Ti0.01Cr0.01)7.85O16•nH2O. The silver content ranges from about 0.22–3.15 wt%, which is much higher than that of other manganese oxides including ranciéite, chalcophanite and coronodite found in this deposit as well. Both of two argentian cryptomelane samples feature two main Raman scattering contributions at about 580 cm−1 and 630 cm−1, belonging to the Mn–O lattice vibrations within the MnO6 octahedral double chains, which can distinguish from other three manganese oxides. The Ag+ prefers to locate in the tunnel sites substituting K+ of cryptomelane due to its large radius and the same monovalent state with K+. Some chain–width disorders characterized by transmission electron microscopy are probably caused by these cation substitutions.

Crustal assembly of the Antananarivo and Masora domains, central–eastern Madagascar: constraints from U–Pb zircon geochronology and whole–rock geochemistry of meta–granitoids

Abstract: *Graduate School of Environment and Information Sciences, Yokohama National University, 79–7 Tokiwadai, Hodogaya–ku Yokohama 240–8501, Japan **Department of Solid Earth Geochemistry (D–SEG), Japan Agency for Marine–Earth Science and Technology (JAMSTEC), 2–15 Natsushima–cho, Yokosuka 237–0061, Japan ***Department of Earth Sciences, Faculty of Science, University of Antananarivo, PB 906 Antananarivo 101, Madagascar

XAFS study on the Zr local structures in tektites and natural glasses

Abstract: The local structures of tektites and natural glasses were studied by Zr K–edge X–ray absorption near edge structure (XANES) and extended X–ray absorption fine structure (EXAFS) measurements in order to obtain quantitative data on the Zr–O (bonding) distances and coordination numbers for the glasses. Zr4+ ions have different coordination environments. The structure of glass (tektite, impact–related glass, fulgurite, and volcanic glasses) is affected by the temperature during the glass–formation process. Differences in the formation processes for natural glasses result in different local structures for the zirconium ions. All tektites can be classified as being of the same type and as having 7–fold coordination Zr ions. The Zr– O distances in tektite glasses are 2.198–2.215 Å, and their XANES spectra are similar, too. Impact–related glasses can be classified into different types and are formed under different physical and geological processes at the impact event. Volcanic glasses, impact–related glasses, and fulgurite glasses have several local Zr structures with 6– and 7–fold coordinated Zr ions. It can thus be concluded that local structures of Zr in natural glasses are closely related to the formation temperature and quenching conditions of the glasses. The Zr XAFS spectra of natural glasses can be used to identify the naturalglasses.

Structural rationale for the occurrence of the elbow twins in cassiterite and rutile

Abstract: Elbow twins are a distinct feature of cassiterite and rutile. Their occurrence is justified by the reticular theory of twinning because of the existence of a common sublattice- the twin lattice - formed by the overlap of a large fraction of the lattice nodes of the individuals. Yet, the atomic basis for the existence of twins falls outside the possibilities of the reticular theory. We present here the analysis of the pseudo-eigensymmetry of the crystallographic orbits building the structure of the elbow twins and show that their occurrence is justified by the complete restoration of the structure near the composition surface, with a deviation of less than 0.7 angstrom.

Jadeite–bearing metaigneous rocks from the Northern Chichibu belt, SW Japan: implications for the lowest–grade Sanbagawa metamorphism

Abstract: Multiple generations of Na–Ca and Na pyroxenes (aegirine–augite, aegirine and jadeite) were found in a metamorphosed monzonitic dike from a coherent mafic layer of the Northern Chichibu belt in central Shikoku, Japan. The mafic layer was derived from alkaline basalt magma and its derivatives, and belongs to the Kamiyoshida unit (Middle Jurassic accretionary complex). The earliest–stage sodic pyroxene (jadeite–free Ti–rich aegirine–augite to aegirine) in the dike probably crystallized during a post–magmatic hydrothermal stage. Igneous Ti–rich augite phenocrysts were almost completely pseudomorphed by chlorite + phengite + Al–OH–rich titanite + sodic pyroxene (aegirine–augite with jadeite component) during early stages of subduction metamorphism. The earliest–stage sodic pyroxene and pseudomorphed Ti–rich augite were further overgrown by jadeite/ aegirine fringes during high–P/T metamorphism. Jadeite/aegirine pyroxene also occurs as small (~ 50 μm long) neoblasts within pseudomorphs (albite + phengite + pumpellyite ± Ba–rich K–feldspar) after igneous plagioclase. Individual grains of the fringe/neoblastic pyroxene are zoned with a jadeite core (up to 98% jadeite content) and an aegirine rim (down to 25% jadeite content). Jadeite–rich pyroxene (up to 92% jadeite content) was also found in basaltic rock from the mafic layer. The absence of quartz and the alkaline affinity of the protoliths suggest that the jadeite formation can be explained by the reaction analcime = jadeite + H2O. If H2O fluid was present, the decrease in jadeite content in the fringe/neoblastic pyroxene implies decompression from ~ 0.6–0.7 GPa at 300 °C to ~ 0.4 GPa at 210–260 °C. The formation of the jadeite–to–aegirine pyroxene during exhumation probably resulted from the lowest–grade Sanbagawa metamorphism.

3D chemical mapping of ‘Mn–caldera shaped zoning’ garnet found from the Sanbagawa metamorphic belt of the Besshi district, SW Japan

Abstract: Garnet with a complex compositional zoning was found from the northern edge of the Western Iratsu body in the Sanbagawa metamorphic belt of the Besshi district, southwest Japan. The studied garnet shows incipient Mn–reverse (increase) zoning from the center part and subsequent Mn–bell shape type (decrease) zoning towards the outer part, which is almost identical to the ‘Mn–caldera shaped zoning’ described by Xu et al. (1994) and Banno and Nakamura (2004). In order to display the chemical characteristics sterically, three–dimensional X–ray chemical mapping was performed for one very–coarse grain of garnet. The result clearly displays that there is a high–Mn layer with faceted euhedral shape of the garnet at the intermediate part, and that its composition continuously changes from the inside to the outside. Inclusion arrays in garnet getting across the high– Mn layer also suggest the continuous growth of the garnet. In the same sample, garnets without Mn–caldera shaped zoning are ubiquitously observed, which are relatively small in size up to 5 mm in diameter. Inclusion mineral assemblage in garnet and Raman barometry suggest the peak P–T conditions of the studied sample not having reached the eclogite facies, but being the epidote–amphibolite facies. The formation process of the ‘Mn– caldera shaped zoning’ can be best explained by the disequilibrium crystal growth under oversaturation of garnet in MnO–(MgO + FeO) binary system. Such oversaturation can be triggered by rapid heating. The finding of the remnant of rapid heating event would provide an important clue to discuss the exhumation history of the Sanbagawa metamorphic belt.

XAFS study of Zr in Cretaceous-Tertiary boundary clays from Stevns Klint

Abstract: The local structure of K–T boundary clays was studied by Zr K–edge X–ray absorption fine structure (XAFS) in order to provide quantitative data on Zr–O bonding distance, coordination number and oxidation state. The Zr XANES spectra in K–T boundary clays are similar to those from rhyolitic volcanic glass samples (obsidian and pitch stone) and tektite. Since tektite was formed at meteorite impact, those observations suggest that the thermal quenching history at meteorite impact is kept preserved as the local structure of Zr in K–T clays. The Zr–O distance in K–T boundary clays is 2.164 Å (4) and the average coordination number is 6.3. The threshold energy on Zr XANES spectra from the K–T clays is lower than those found on natural glasses, and total effective charge of zirconium ion (formally 4+) estimated from the shift of the spectrum is 3.8+ – 3.9+. The partial reduction of zirconium ion in K–T clays is ascribed to its formation environment, high temperature under reductive environment. Preservation of the partial reduction state also indicates quick quench of K–T clays at their formation, and this observation give as a clue to distinguish sedimentary rocks deposited at periods of so– called extinction events by investigating Zr local structure.

The effect of curing temperature of high alumina cement on the crystallization of stratlingite: In the case of curing temperatures of 10 °C and 60 °C

Abstract: Stratlingite is one of the constituent minerals of the bonding matrix of low–cement castables. In this study, the crystallization processes of stratlingite in hydrates of high alumina cement at 60 °C and 10 °C were analyzed using X–ray diffraction (XRD) and electron probe microanalyzer (EPMA). The stratlingite has crystallized in large quantities in the samples cured at 60 °C, while in the samples cured at 10 °C, stratlingite was not detected beyond the period of fifteen months.

Local structure around Ge in lithium germanate glasses analyzed by AXS and EXAFS techniques

Abstract: The local structure around Ge in xLi2O–(1 − x)GeO2 (x = 0, 0.17, 0.20, 0.24) glasses was investigated using AXS and EXAFS measurements. The averaged coordination number of the first nearest Ge–O pair increased with increasing Li2O content up to 24 mol% and the amount of six–coordinated Ge was proportional to Li2O content. The introduction of a GeO6 unit is suggested to be one of the most fundamental structural changes accompanying the so–called germanate anomaly detected in density measurements of alkali–germanate glasses.

Geochemical and Sr–Nd isotopic characteristics of Quaternary Magmas from the Pre–Komitake volcano

Abstract: The trace element and Sr–Nd isotopic compositions of Quaternary magmas from the Pre–Komitake volcano were investigated. The Sr and Nd isotope ratios ranged from 0.703320–0.703476, and 0.512885–0.513087, respectively, which are very similar to those of the lavas from Fuji and Komitake volcanoes that erupted subsequently. Enrichment of large ion lithophile elements, Pb and Sr, can be seen in the primitive mantle–normalized multi–element diagram of the Pre–Komitake, Komitake, and Fuji lavas. These collectively show island arc lava signatures; however, the middle to heavy rare earth elements are more depleted in the Pre–Komitake lavas, compared to those from Fuji. Positive Eu anomalies are observed, although the extents of these anomalies decrease with increasing SiO2 in the Pre–Komitake lavas, whereas this is not observed in Fuji lavas. The Sr/Y ratios of Pre–Komitake lavas increase from basalt to basaltic andesite, but decreases through andesite to dacite. This occurs in combination with a rapid increase in La/Yb ratios, followed by a more gradual increase. A gradual decrease in Dy/Yb ratios is also seen over the entire compositional range. These data suggest deep (>12 kbar) fractionation of garnet and amphibole followed by shallow (i.e., ~ 5 kbar) fractionation of amphibole and plagioclase. Such variations are not observed in the Komitake and Fuji lavas, for which deep fractionation of clinopyroxene and shallow fractionation of plagioclase have been suggested. All three lavas, including those from the Pre–Komitake volcano, show similar isotopic, major, and trace element compositions in the unfractionated basalts. The differing geochemical trends found in the Pre–Komitake lavas are likely to be due to different mineral fractionations occurring in the hydrous Pre–Komitake basalts compared to the dry Fuji and Komitake basalts.

Ruby–bearing feldspathic dike in peridotite from Ray–Iz ophiolite, the Polar Urals: Implications for mantle metasomatism and origin of ruby

Abstract: *Department of Earth and Environmental Sciences, Graduate School of Science and Technology, Kumamoto University, 2–39–1 Kurokami, Chuo–ku, Kumamoto 860–8555, Japan **Department of Earth Sciences, Kanazawa University, Kakuma, Kanazawa 920–1192, Japan ***ODS, JAMSTEC, 2–15 Natsushima, Yokosuka 237–0061, Japan Zavaritskii Institute of Geology and Geochemistry, Ural Branch, Russian Academy of Sciences, Russia

Petrogenesis and geotectonics of the Mikame ultramafic body, western Shikoku, Japan

Abstract: The Mikame ultramafic body, located in westernmost central Shikoku, Japan, forms a nappe accompanied by the Maana Formation and low– to medium–pressure Oshima metamorphic rocks. This body is divided into the Shigiyama and Korotokibana masses. The Shigiyama mass is composed of very fresh dunite, wehrlite and pyroxenite; whereas the Korotokibana mass is composed of antigorite–bearing meta–serpentinite derived from dunite and wehrlite. Estimated equilibrium temperatures are 600–700 °C for the Shigiyama mass and 400–500 °C for the Kototokibana mass, respectively. The geological and petrological characteristics of the Mikame ultramafic rocks are similar to those of the Higo belt in central Kyushu, rather than those of the Mikabu and Kurosegawa belts, and the Mikame body is possibly equivalent to the Higo belt. The Shigiyama ultramafic rocks are subdivided into Mg– and Fe–rich suites based on their olivine and chromian spinel compositions. The Mg–rich suite is characterized by magnesian olivines (Fo84–92) and high–Cr# [= Cr/(Cr + Al) = 0.5–0.8] spinels. On the other hand, the Fe–rich suite contains less magnesian olivines (Fo74–88) and low–Cr# (= 0.3–0.4) spinels. The Mg– and Fe–rich suites of the Shigiyama ultramafic rocks are cumulates formed from depleted and less depleted magmas, respectively. The chemistry of the chromian spinels in the Mikame ultramafic rocks indicates that they formed by crystal accumulation from magmas generated in an arc setting. The Korotokibana meta– serpentinites resemble those from the Mariana forearc regarding their mineral assemblage, and olivine and chromian spinel compositions. The Korotokibana meta–serpentinites experienced dehydration at 400–500 °C, after serpentinization caused by addition of H2O released from a subducting slab, whereas the Shigiyama ultramafic rocks contain no evidence for dehydration. The Mikame ultramafic body may have been the lower forearc crust produced by magmas with various degrees of depletion, later subjected to diverse hydration and dehydration processes.

Mieite–(Y), Y 4 Ti(SiO 4 ) 2 O[F,(OH)] 6 , a new mineral in a pegmatite at Souri Valley, Komono, Mie Prefecture, central Japan

Abstract: Mieite–(Y), ideally Y4Ti(SiO4)2O[F,(OH)]6, was found in a pegmatite at Souri Valley, Komono, Mie Prefecture, central Japan. It occurs as an amber yellow mass with adamantine luster, approximate size of 1 cm and white streak. The mineral is associated with quartz, albite, K–feldspar, muscovite, allanite–(Ce), gadolinite–(Y), and magnesiorowlandite–(Y). Cleavage is not observed and fracture is uneven. The Mohs hardness is 6. The calculated density is 4.61 g/cm3. It is biaxial and refractive indices are α = 1.694(2) and γ = 1.715(5) with non–pleochroism. The mineral displays anomalous blue interference colors. The empirical formula is (Y3.13Dy0.20Gd0.17 Yb0.08Nd0.08Sm0.07Er0.07Th0.05Tb0.03Ho0.03Lu0.03Ce0.02Tm0.02U0.02)Σ4.00(Ti0.52Al0.44Fe0.01)Σ0.97(Si1.92P0.12)Σ2.04O9 [F3.83(OH)1.91]∑5.74 on the basis of 7 cations and 9 oxygen atoms pfu after electron microprobe (WDS), FT/IR and crystal structure analyses by means of single crystal XRD data. The raw material is significantly metamictized to give extremely weak diffraction peaks. The unit cell parameters refined from powder XRD pattern of recrystallized material are; a = 14.979(6), b = 10.548(5), c = 6.964(3) Å, V = 1100.3(8) Å3 and Z = 4. The 7 strongest lines in the powder XRD pattern [d(Å) (I/I0) hkl] are; 2.68 (100) 331, 3.76 (85) 400, 3.54 (83) 002, 3.48 (82) 130, 2.16 (78) 023, 4.26 (68) 021, 5.46 (58)111. The crystal structure was refined in space group Cmcm to R1 = 0.0825 and 0.0735 for 491 and 581 reflections with I > 2σ(I ) single crystal XRD data of raw and recrystallized materials, respectively. The crystal structure of mieite–(Y) consists of infinite columns of corner– sharing TiO6 octahedra decorated by SiO4 tetrahedra. The columns are linked by two independent Y polyhedra with different coordination, YO2F5 and YO5F3. A coupled substitution of Ti4+ + F− = Al3+ + □ (vacancy) was suggested for mieite–(Y). Mieite–(Y) is isostructural with the ‘yftisite’, a discredited species. Mieite–(Y) can be classified in the Dana class 52.4.4.3 and Strunz class 9.AG.25, nesosilicates with additional anions.

Thermal equation of state of lawsonite up to 10 GPa and 973 K

Abstract: Thermal equation of state (EoS) of synthetic lawsonite [CaAl2Si2O7(OH)2·H2O] has been established using in– situ X–ray diffraction methods under high pressure and high temperature. Sodium chloride NaCl was used as the pressure standard in the experiments. The unit–cell volumes were measured up to 10 GPa and 973 K after the deviatric stress was released at high temperature. The P–V–T dataset was analyzed using a Birch–Murnaghan equation of state, yielding the room pressure volume V0 = 674.2(2) Å3 and the isothermal bulk modulus at room temperature K0 = 129(2) GPa (K′ set to 4). These values are comparable with the previous studies. When fitting the high temperature data, a second order temperature derivative of the bulk modulus was considered. Unlike Daneil et al. (1999) who reported a minimum value of bulk modulus at ~500 K, the bulk modulus decreases with increasing temperature at least up to 973 K. The dataset yields: V0 = 674.3(4) Å3, K0 = 128.7(15) GPa, (∂KT /∂T )P = −0.047(8) GPa K−1, (∂KT /∂T)P = 0.028(6) × 10−3 GPa K−1, α = 3.13(25) × 10−5 K−1, assuming K′ = 4. These data can be used to calculate the density and the stability of lawsonite under high pressure and high temperature conditions.