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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Acknowledgments
The Editorial Board would like to thank all the scientists who served as referees in 2009.

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The Glen Eden Mo-W-Sn deposit, New South Wales, is located at a site of igneous activity, which is characterized by both intrusive and extrusive felsic igneous rocks. Mo, W and Sn mineralization is related to the intrusive rocks as evidenced by temporal, spatial and geochemical relationships. The main part of the deposit is hosted by a pipe-like greisen breccia body, ∼ 500 m in diameter. The mineralization at Glen Eden occurred in two stages: pre-breccia mineralization in the volcanic wall rocks and post-breccia mineralization in the pipe. Minerals such as molybdenite, wolframite, cassiterite, chalcopyrite, sphalerite, arsenopyrite, pyrite, pyrrhotite, and galena were deposited as disseminated grains in the wall rocks and as open-space fillings in the breccia pipe. Quartz, fluorite, muscovite, K-feldspar, and Bi-bearing minerals are also found in the pipe. In addition to common bi-bearing ore minerals (native bismuth, bismuthinite, joseite A, bursaite, and galenobismutite), there is an unknown opaque Bi-bearing mineral with the composition of Bi₄TeS₅. This mineral is white in color with a slight yellowish tint and shows strong reflectance, weak pleochroism, moderate anisotropy in greenish colors, no internal reflections, possible twinning, and low hardness. In the paragenetic sequence, cassiterite and wolframite mostly precipitated before sulfides; however, locally, there was overlap with sulfide mineralization. Hydrothermal minerals were deposited mainly in the temperature range of 350-250 °C from hydrothermal fluids with low salinity (<8 wt% NaCl equivalent) and high salinity (>30 wt% NaCl equivalent) at a pressure of approximately 400 bar. At 250-350°C, hydrothermal fluids had pH = 3.1-5.2, f _H2S = 10^-3.7-10^1.6 bars, f _O2 = 10^-47.8-10^-30.2 bars in the pre-breccia stage and pH = 4.9-5.9, f _H2S = 10^-2.7-10⁰ bars, f _O2>10^-36.7 bars in the post-breccia stage. In the pre-breccia stage, the precipitation of ore minerals occurred mainly due to the increase in pH of hydrothermal fluids as result of the reaction of hydrothermal fluids with wall rock. The deposition in the post-breccia stage mainly occurred by an increase in the pH and f _O2 (due to boiling) of the hydrothermal fluid and a decrease in temperature due to the boiling and mixing of magmatic and meteoric waters.

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The 3400 BC caldera-forming eruption of Numazawa Volcano in NE Japan started with a cataclysmic pyroclastic flow eruption (∼ 2 km³ dense rock equivalent), which accounted for more than 90% of the total volume of the eruption products. This was followed by a Plinian eruption, phreatomagmatic eruptions, and a second Plinian eruption. The juvenile pyroclasts produced during the first two eruption phases are mostly dacitic, whereas those in the two subsequent phases are essentially andesitic. We recognized two distinct types of dacitic pumices: white and gray pumices. The two pumices are virtually identical in terms of both whole-rock composition (∼ 64.8-66.1 wt% SiO₂) and crystal content (∼ 40-46 vol%), but are very different in terms of texture. The white pumice, which typically contains abundant euhedral phenocrysts, is the dominant variety and occurs throughout the pyroclastic flow deposits and in the overlying Plinian fall deposit. The gray pumice, which typically has bread-crusted surfaces and contains ubiquitous crystal fragments and xenoliths, occurs in the upper flow units of the pyroclastic flow deposits. We suggest that the textural differences between the two types of pumices reflect the difference in local stress conditions within the volcanic conduit below the magma fragmentation level. The abundance of euhedral phenocrysts in the white pumice suggests that it is the vesicular equivalent of the dacite that chamber ascended through the central part of the conduit that suffered low shear stress. In contrast, the magma that generated the gray pumice is thought to have originated from similar dacitic magma; the gray pumice magma was probably produced by the mechanical breakage of phenocrysts during magma ascent along the region of high shear stress near the conduit walls. The limited accumulation of the gray pumice in the upper units of the pyroclastic flow deposits suggests that crystal size reduction mainly occurred during the late stage of the pyroclastic flow eruption prior to the first Plinian eruption. It is likely that an abrupt conduit blockage caused by the waning of the eruption activity and the resulting temporal high shear stress at the conduit walls promoted crystal fragmentation, thus forming the gray-pumice magma and resulting in the subsequent eruption being a Plinian eruption.

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Potassic-ferropargasite, ideally KCa₂(Fe₄²⁺Al)Si₆Al₂O₂₂(OH)₂, is a new member of the amphibole group occurring in a schistose calcareous hornfels from Kabutoichiba, Kameyama, Mie Prefecture, central Japan. The amphibole occurs as black subhedral to anhedral crystals, up to about 700 μm long, associated with calcite, biotite, K-feldspar, plagioclase, scapolite, chlorite and titanite. Potassic-ferropargasite is optically biaxial negative with α = 1.680(2), β = 1.690 (calc.), γ = 1.698(2) and 2V = 80-90°. The mineral is monoclinic, space group C2/m, with refined unit-cell parameters a = 9.937(5), b = 18.108(5), c = 5.335(4) Å, β = 105.30(3)°, V = 926.0(9) ų, Z = 2. The three strongest lines in the X-ray powder-diffraction pattern [d in Å (I) hkl] are 2.72 (100) 151, 8.48 (81) 110 and 2.61 (59) 061. Electron-microprobe gave SiO₂ 38.08, TiO₂ 1.92, Al₂O₃ 15.12, Cr₂O₃ 0.44, FeO 19.96, MnO 0.22, MgO 6.22, CaO 11.73, Na₂O 1.57, K₂O 2.74, F 0.13, Cl not detected, O = F + Cl -0.05, total 98.08 wt%, corresponding to (K_0.54Na_0.42)_Σ0.96(Ca_1.95Na_0.05)_Σ2.00(Fe²⁺_2.59Mg_1.44Al_0.67Ti_0.22Cr_0.05Mn_0.03)_Σ5.00(Si_5.91Al_2.09)_Σ8.00O₂₂(OH_1.94F_0.06)_Σ2.00 on the basis of O = 23, assuming OH + F + Cl = 2. The crystal structure of the clinoamphibole type was refined to an R of 6.5%.

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Ultra-depleted dunites from the Sibuyan Island, Romblon (Central Philippines) are primarily composed of olivine, orthopyroxene (<5%), trace clinopyroxene and chromian spinel and are totally free of hydrous minerals and plagioclase. Mineral chemistry shows very refractory compositions (olivine Fo = 92-94; spinel Cr# > 0.75). Rare clinopyroxene preserved in the ultra-depleted dunites is anhedral and interstitial to olivine grains. They are neither subsolidus exsolution products from orthopyroxene nor metasomatic in origin. Clinopyroxene has high Mg# = 0.94-0.97 and low Al₂O₃ contents (<0.85 wt%). They are also very depleted in trace elements with only selected heavy rare earth elements detected during the LA-ICP-MS analysis. Light to middle REEs and LILEs were hardly detected, which is indicative of the very depleted character of the melt that precipitated the clinopyroxene. The calculated melts in equilibrium with the clinopyroxene have heavy REE contents similar to olivine-hosted ultra-depleted melts of MORB affinity from the East Pacific Rise and the Mid-Atlantic Ridge. The formation of the Sibuyan ultra-depleted dunites is being attributed to extremely high degree of dry melting below a mid-oceanic ridge.

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We examined vertical variations of the petrological characteristics of a 33-m-thick peridotite section under the layered gabbro section along Wadi Fizh of the northern Oman ophiolite to understand the formation mechanism of the Mohorovicic discontinuity (Moho) beneath a spreading center. Here, we refer to the base of the layered gabbro section as “L-Moho” for the sake of simplicity. Network-like gabbro sills in peridotites increase in frequency upward to the L-Moho. The L-Moho is underlain by a 1-m-thick wehrlite layer, under which exists a 10-m-thick dunite layer, overlying a harzburgite layer where total pyroxenes slightly increase downward. Wehrlite is also found as screens between gabbro layers above the L-Moho. The mineral chemistry indicates systematic variations toward the L-Moho within the peridotite section; the Fo content (91 to 85) and NiO (0.4 to 0.2 wt%) of olivine decrease; the TiO₂ content of clinopyroxene (0.1 to 0.6 wt%) and spinel (nil to 1.4 wt%) and atomic ratios of Cr/(Cr + Al) (0.5 to 0.6) and Fe³⁺/(Cr + Al + Fe³⁺) (0.05 to >0.1) in spinel increase upsection from the base (harzburgite) to the around L-Moho wehrlite via dunite. These variations are essentially similar to those observed in harzburgite/MORB reaction products from Hess Deep, East Pacific Rise, and possibly indicate that the lithological and mineral chemical variations within the examined peridotite layer resulted from the reaction between a harzburgite and a melt that produced the layered gabbros.

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We measured the Raman spectra of Fe-Mg olivine grains with Mg# [= 100 × Mg/(Mg + Fe)] values ranging from 80-100 under a pressure of up to 4 GPa using a diamond anvil cell (DAC). We focused on a relatively weak peak at around 547 cm^-1, denoted as peak 0, and two intense peaks at around 825 cm^-1 (peak 1) and 857 cm^-1 (peak 2). The peak position (κ) of each peak shifted upward linearly as Mg# and pressure increased; the Mg# derivatives (∂κ/∂Mg#) for peak 0, peak 1, and peak 2 under ambient pressure were 0.496, 0.184, and 0.227 cm^-1/Mg#, respectively. The pressure derivatives (∂κ/∂P) for peak 0, peak 1, and peak 2 were 1.558-2.08, 3.38-3.46, and 3.20-3.35 cm^-1/GPa, respectively. The value of ∂κ/∂P for peak 0 decreased as Mg# increased, whereas those for peak 1 and peak 2 were almost constant against Mg#. The peak positions of peak 0, peak 1, and peak 2 were formulated as functions of Mg# and pressure based on the results. We found that when the ranges of Mg# and pressure are limited to 85-100 and 0-1 GPa, the combination of peak 0 and peak 1 reproduced the original observed data with an error of ± 0.9 for Mg# and an error of ± 0.09 GPa for residual pressure. We applied these functions to a natural olivine inclusion in a diamond obtained from Internationalnaya pipe, Yakutia, Siberia, Russia, and obtained reasonable values of Mg# and pressure—91.6 ± 0.6 Mg# and 0.32 ± 0.05 GPa, respectively.

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Cristobalite and tridymite in andesite and obsidian exhibit bright blue emissions in color cathodoluminescence (CL) images. CL spectra of cristobalite and tridymite show emission bands at 400 and 430 nm, respectively. Their CL intensity decreases with an increase in the electron irradiation time, similar to the short-lived blue luminescence reported in hydrothermal quartz. The reduction rate of the CL intensity of hydrothermal quartz is small as compared to cristobalite and tridymite. The initial CL intensity of both minerals immediately after the electron irradiation is positively correlated with the Al₂O₃ content. This suggests that the blue emissions of cristobalite and tridymite can be attributed to the [AlO₄/M⁺]⁰ defect center (M: H⁺, Li⁺, Na⁺, and K⁺). The electron irradiation of cristobalite and tridymite diffuses the monovalent cations of H⁺, Li⁺, and Na⁺ and destroys their crystal structure, resulting in short-lived blue luminescence. The CL intensity after 600 s of electron irradiation depends on the K₂O impurity content. In contrast to other monovalent cations, the K⁺ cation is not diffused because of its large ionic radius. The CL emissions of cristobalite and tridymite after 600 s of electron irradiation can be attributed to the [AlO₄/M⁺]⁰ defect (M: K⁺). CL images of cristobalite in obsidian from Utah, USA, show a heterogeneous distribution of CL intensity, with oscillatory CL zoning on the rim and radial lath-shaped textures with bright CL superimposed on weak luminescence background. This implies that lath-shaped textures with bright emissions might have crystallized from rhyolitic magma at temperatures higher than the recrystallization temperature minerals in the other areas.

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We report occurrence and origin of graphite in glimmerite and spinellite from an unusual ultramafic complex in Achankovil Shear Zone (ACSZ) in southern India. Raman analyses of primary graphite flakes in close association with spinel and phlogopite confirm the highly crystalline nature. The carbon isotope composition ranges from -7‰ to -9.8‰ typical of mantle-derived graphite. A genetic model is proposed in which carbon was derived from a reduced juvenile mantle source linked to the genesis of volatile rich ultramafic rocks in ACSZ.

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Edited by the Abstracting Committee, Japan Association of Mineralogical Sciences

Ore Minerals and Economic Geology
Age Determination 104168—104170;
Gold Mineralization 104171—104182

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Index to Journal of Mineralogical and Petrological Sciences Vol.104 No.1-6
Author Index
Keyword Index

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Journal of Mineralogical and Petrological Sciences
Volume 104, Number 1-6
February-December, 2009

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