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.

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Carbonatites occur on most continents and are often associated with economic ore deposits. In rare cases, carbonatites are associated with particular Fe and P-rich rocks, the latter of which can also be of economic importance and can form ores for copper, zirconium, or platinum group elements. Here I present some novel experimental constraints in Fe and P-rich carbonate and silicate-rich systems as a starting point to better understand the origin of these rock types. Phase relations in the system CaO-MgO-Fe₂O₃-P₂O₅-SiO₂-H₂O-CO₂ were studied at elevated temperatures (1000-1400 °C) and at high pressures (1 GPa). The liquidus of the systems studied varies between 1300 and 1400 °C. Liquidus phases are, depending on bulk composition, olivine or magnetite. Apatite, pyroxenes and calcite were found to generally crystallize at much lower temperatures. Using experimentally determined mineral and melt compositions, melt compositions were calculated for fractional crystallization of Fe- and P-rich carbonate-rich silicate magma.

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Omphacite-bearing metapelite was found from the Seba area of the Besshi region, Sambagawa metamorphic belt, central Shikoku, Japan. Omphacite occurs as inclusions in garnet together with quartz, sodic amphibole, phengite, and paragonite. The major matrix phases are quartz, albite, phengite, chlorite, subcalcic amphibole, calcite, dolomite, and graphite. Garnet shows a prograde zoning and comprises three segments in order from the crystal center to the margin: the core, inner mantle, and outer mantle. The garnet core shows monotonous decrease of MnO content outward, and includes sodic phases: paragonite and glaucophane. The garnet mantle is substantially homogeneous in composition, and poorer in MnO and richer in MgO than the core. The inner mantle of garnet includes omphacite, paragonite and glaucophane. The outer mantle includes omphacite, but paragonite and glaucophane grains are absent. The jadeite content of omphacite inclusions (X_Jd) increases slightly from 0.55 in grains included in the inner mantle to 0.62 in the outer mantle of garnet.
     The systematic distribution of sodic minerals in garnet documents a prograde evolution of metamorphism from the blueschist to eclogite facies conditions. The occurrence of omphacite-bearing metapelite in the Seba area of the Besshi region is direct evidence of: (1) at least some of the Sambagawa metapelites in the Besshi region certainly experienced eclogite facies metamorphism, and (2) eclogite facies metamorphism extends beyond the previously assumed eclogite facies area in the Sambagawa belt.

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Tertiary and Quaternary lavas from the West Java arc, Indonesia, have been analyzed to identify their major and trace elements and Sr-Nd-Pb isotope compositions. The analyzed samples are basaltic to andesitic in composition and are representative of the across-arc setting in both the Tertiary (Miocene) and Quaternary periods. The results indicate that the major and incompatible trace elements are enriched in the rear arc (RA) lavas compared to the volcanic front (VF) lavas. The Nd isotope composition is systematically more radiogenic in the VF lavas, although Pb and Sr isotope compositions in the VF and RA lavas are virtually identical. The incompatible element variation can be simply explained by the differing degree of partial melting in the mantle source, i.e., the melting is greater in the VF and lesser in the RA. The contrast in the Nd isotope composition originates from the different flux rates of the slab fluid relative to the mantle partial melts; these rates are higher in the RA and lower in the VF. The total fluid addition to the mantle mass is greater in the VF; however, a greater degree of melting in the VF dilutes the contribution of radiogenic Nd from the sediment fluid (Sendjaja et al., 2009). The across-arc geochemical variation between the Tertiary and Quaternary lavas does not differ. This implies that the West Java arc has been in a “steady state” over the past 10 million years, with continuous subduction input from the Indian Ocean sediments and continuous upwelling and replenishment of the depleted mantle source from the back arc.

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The crystal structure of CO₃-cancrinite was analyzed by applying a generalized structure factor expression of the Gram-Charlier expansion to the least-squares refinement performed by using the X-ray intensities measured on single crystals at 173, 293, 473, and 673 K. No satellite reflection or diffuse scattering was observed. The space group is P6₃ with unit cell a = 1.2604(3) and c = 0.51144(8) nm at 173 K, and a = 1.2709(4) and c = 0.5202(6) nm at 823 K. The temperature behavior for the dehydration and the unit cell dimensions were considerably different from those previously reported for CO₃-cancrinite, which shows superstructure reflections..
     Two position vectors were assigned to each of the framework atom sites or the CO₃ site for examining its asymmetric probability density function—one for the free energy minimum and another for the potential energy minimum. Two polarization vectors were obtained for a unit cell from those position vectors and ion charges. The rigid ion contributions to the pyroelectric coefficients p^(σ) (measured under a constant stress σ) and the secondary coefficient p⁽²⁾ were finally estimated from the temperature dependences of the polarization vectors.

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Edited by the Abstracting Committee, Japan Association of Mineralogical Sciences

Ore Minerals and Economic Geology
      Gold Mineralization 105001—10501

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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 below: http://wwwsoc.nii.ac.jp/jams3/jmps.htm

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