Official journal of Japan Association of Mineralogical Sciences (JAMS), focusing on mineralogical and petrological sciences and their related fields. Journal of Mineralogical and Petrological Sciences (JMPS) is the successor journal to both “Journal of Mineralogy, Petrology and Economic Geology” and “Mineralogical Journal”. Journal of Mineralogical and Petrological Sciences (JMPS) is indexed in the ISI database (Thomson Reuters), the Science Citation Index-Expanded, Current Contents/Physical, Chemical & Earth Sciences, and ISI Alerting Services.

View full abstract

Compositional and textural characteristics of the zonal structure and inclusions of garnet in metapelites from areas of high-grade greenschist facies (garnet zone) to areas of epidote-amphibolite facies (albite-biotite and oligoclase biotite zones) located along the Asemi-gawa route were examined using EPMA and Raman spectroscopy to investigate evolution of the P-T history of Sanbagawa metamorphism. Garnet grains exhibit two types of compositional zoning patterns: bell-shaped and composite types with spessartine variation. Bell-shape zoning is characterized by a monotonous decrease in the spessartine component from the crystal core towards the margin. Almandine and pyrope components exhibit the opposite trend. The grossular content reaches a maximum at an intermediate position between the core and the rim, and then decreases towards the outermost rim. The composite-zoned garnet is divided into core and mantle parts and it exhibits discontinuous compositional variations according to the associated boundary, evidencing resorption of the core and overgrowth of the mantle during crystallization; implying a two-stage growth of garnet during the Sanbagawa metamorphism. Composite-zoned garnet is characteristically observed in metapelites from a part of the albite-biotite zone, and quartz grains included in its core retain a higher residual pressure than those in garnet from other mineral zones. Isolated paragonite crystal occurs particularly as an inclusion in the core part of this composite-zoned garnet. These data suggest that part of the Sanbagawa metamorphic rocks in the Asemi-gawa region recrystallized under higher-pressure conditions up to the eclogite facies, prior to regional metamorphism from the greenschist, to the epidote-amphibolite facies that formed the regional thermal structure of the Sanbagawa belt of central Shikoku.

View full abstract

Calciborite was found as a veinlet or a mass in crystalline limestone associated with gehlenite-spurrite skarns at the Fuka mine, Okayama Prefecture, Japan. Calciborite occurs as milky white aggregates up to 1 mm in diameter with shimazakiite, fluorite, bornite and calcite. An electron microprobe analysis of calciborite gave an empirical formula (Ca_0.999Mn_0.001Co_0.001)_Σ1.001B_1.999O₄ based on O = 4. The unit cell parameters are a = 8.373(2), b = 13.811(8), c = 5.012(4) Å. The mineral is optically biaxial (-), α = 1.594(2), β = 1.654(2), γ = 1.672(2) and 2V_calc. = 56°. The Vickers microhardness is 177 kg mm^-2 (50 g load), and the Mohs hardness number is 3.5. The measured and calculated densities are 2.88(2) and 2.881 g cm^-3, respectively. The calciborite from the Fuka mine was probably formed by a reaction of boron-bearing fluids with limestone at a temperature between 250 and 300 °C.

View full abstract

Cathodoluminescence (CL) measurements of zircon sample with two different geological ages have been conducted to clarify the polarization effect of different types of luminescence centers and the effects of electron-irradiation on CL. Polarization of CL has been confirmed in the emissions related to both defect and impurity centers in zircon. Prolonged exposure of electron irradiation reduces the CL intensities of broad bands related to intrinsic defect centers in the blue region and those of narrow bands attributed to Dy³⁺ activator, whereas CL intensity of the broad bands attributed to metamictization in the yellow region increases with prolonged irradiation. Therefore, electron irradiation has a different effect on the emission mechanisms of defect centers observed in the blue and yellow regions.

View full abstract

This study investigated the distribution and mineralogy of radioactive Cs in a core sample from reservoir sediment affected by the Fukushima Daiichi Nuclear Power Plant accident. The sample was obtained 19 months after the accident from a reservoir in Iitate-mura, Fukushima Prefecture. The vertical concentrations of radioactive Cs in the sediment core varied little from the surface to 9 cm depth: 20-30 Bq/g for ¹³⁷Cs. The concentration decreased abruptly at depths greater than 9 cm. The radioactive Cs concentrations were particle-size dependent: finer particles exhibited higher concentrations of radioactive Cs. X-ray diffraction analyses of the size-fractionated sample revealed that the contribution of clay minerals (14 Å minerals, kaolin mineral and mica) increased concomitantly with the decrease of particle size, implying a close relation between radioactive Cs concentration and clay mineralogical compositions. Periodical airborne monitoring showed that the ¹³⁷Cs inventory in the reservoir catchment area decreased significantly with time after the accident. Results of a ¹³⁷Cs inventory in the reservoir sediment were almost identical to those for the catchment area immediately after the accident, but were significantly higher than those in the core sampling period. Results might indicate that the reservoir sediments serve as a sink for radioactive Cs.

View full abstract

This paper reports the paragenesis and reaction textures of rare earth minerals such as monazite, zircon, allanite, thorite, xenotime, and apatite in pegmatites within the Setouchi Province, Inner Zone of Southwest Japan. One of the zircon grains described shows parallel growth with thorite, suggesting their limited solid solution. Xenotime grains are sometimes disseminated by thorite and overgrown by zircon. Monazite in most pegmatites is corroded and replaced with an aggregate of allanite, apatite, thorite, and occasional xenotime and zircon. Core-mantle domains in zircon grains in one of the pegmatites give high Th/U ratios (0.8-0.4) with lower U and Th contents, and rim domains give low Th/U ratios (0.5-0.2 or less) with higher U and Th contents. The decrease of the Th/U ratio toward the rim results from the change of co-precipitating phase from monazite to thorite. The indistinguishable monazite age (81.7 ± 6.4 Ma) and zircon age for the rim domains (82.9 ± 2.1 Ma) suggest that the paragenetic change occurred during a single evolution of pegmatite. The composition of the metasomatic fluid changed from Ca-poor to Ca-rich, causing monazite corrosion and the consequent precipitation of thorite and allanite. This, in turn, regulated the Th and U contents and the Th/U ratio in associated zircon, as well as the fluid composition.

View full abstract

Iwateite, Na₂BaMn(PO₄)₂ is a new mineral, which was found in the manganese ore of the No. 3 (Matsumaezawa) deposit in the Tanohata mine, Tanohata Village, Iwate Prefecture, Japan. Iwateite has a glaserite structure, which occurs as granular to anhedral inclusions of 10-100 μm in the main constituent minerals in manganese ore and sérandite crystal. It is colorless with white streaks, non-fluorescent, and it displays very weak pleochroism. Iwateite crystallizes in the trigonal system and belongs to the P3 space group where, a = 5.3642(10), c = 7.039(2) Å, V = 175.41(8) ų, and Z = 1, with a calculated density of 4.06 g/cm³.

View full abstract

Discordant chromitite, one of the structural types of ophiolitic chromitite, and surrounding peridotites, were examined in the mantle section of the northern Oman ophiolite along Wadi Hilti, to constrain its origin. Spinels from chromitite and adjacent peridotites show high Cr# (= Cr/(Cr + Al) atomic ratio), around 0.65 to 0.75, indicating an arc-related feature. Clinopyroxenes from adjacent harzburgites show low HREE contents, indicating a highly depleted character. The calculated melt composition in equilibrium with clinopyroxene in the dunite envelope indicates that the chromitite and surrounding peridotites were derived from arc-related magma, such as boninite. The arc-related magma was probably generated by the flux melting of depleted mantle harzburgite on the subducted slab, in terms of incompatible element enrichment in clinopyroxene from dunite and harzburgite. The highly depleted harzburgite surrounding discordant dunite and chromitite shows transitional changes in spinel and REE chemistry toward the surrounding oceanic harzburgites. This feature indicates that pre-existing oceanic harzburgite was partially modified by arc-related magma. Discordant chromitite, dunite, and highly depleted harzburgites are probably formed at the supra-subduction zone environment just before ophiolite obduction. Such arc-related features in mantle peridotite may be produced at a young sub-arc mantle.

View full abstract

Natural quartz crystals are composed of the rhombohedral r{10.1}, z{01.1} and prizm m{10.0} faces. High-quartz exhibits a hexagonal bipyramidal habit with no prism faces or rarely small prism faces. In either low-quartz or high-quartz, the appearance of a basal c{00.1} faces is extremely rare. It has been shown that the faces from the exceptional localities where quartz crystals with basal faces occur have developed by dissolution or overgrowth on the mechanically-broken surface. In the present study, high-quartz crystals with a basal pinacoid from Nagatani, Nose-town, Osaka Prefecture were investigated by means of SEM-CL, and the growth band implying that the c-faces should be directly developed by an original growth process, neither by a dissolution process nor by overgrowth on the broken surface, was first found.

View full abstract

Manuscripts to be considered for publication in the Journal of Mineralogical and Petrological Sciences should be original, high-quality scientific manuscripts concerned with mineralogical and petrological sciences and related fields. Submitted papers must not have been published previously in any language, and author(s) must agree not to submit papers under review in the Journal of Mineralogical and Petrological Sciences to other journals. The editorial board reserves the right to reject any manuscript that is not of high quality and that does not comply with the journal format outlined below. The editorial board is keen to encourage the submission of articles from a wide range of researchers. Information on submitting manuscripts is also available from the journal web site (http://jams.la.coocan.jp/jmps.htm).

View full abstract