The amphibole group is a complex, compositionally diverse group among silicates, and exists in large varieties of rock types and P-T ranges making it very useful P-T and petrogenetic indicator. In 2004 the International Mineralogical Association (IMA) revised its 1997 nomenclature scheme for amphiboles to accommodate all known amphibole species including several species discovered after 1997. The main difference between the 1997 and 2004 schemes is that amphiboles were divided into five groups in the 2004 scheme instead of four groups in the 1997 scheme. ClassAmp is an MS Excel-VBA program that implements the 2004 IMA revisions of and additions to the 1997 nomenclature scheme of amphiboles. In addition to implementing the new nomenclature scheme of amphiboles, ClassAmp is flexible where it can be used to classify microprobe or wet chemical analysis; obtain any combination of amphibole's cation names, cation values, structural formula names, structural formula values, groups, names, prefixes, and modifiers; properly format chemical symbols, associated with amphibole nomenclature so that the output can be directly imported to final drafts/publications; and determine pressure-temperature involves amphiboles as well as other petrogenetic determinations.
Petrographical studies examining the development and variations of sub-solidus reactions recorded in the Toki granite represent the three-dimensional cooling pattern of this zoned pluton in Central Japan. Samples collected from 19 boreholes in the Toki granite show characteristics indicative of spatial variations in the extent of the sub-solidus reactions. Exsolution coarsening has produced microperthite, including albite-rich lamellae, in this pluton, while deuteric coarsening has resulted in the formation of patchperthite, myrmekite, and the reaction rim. The extent of the deuteric coarsening reactions can be evaluated from the width and spacing of the albite-rich patch in patchperthite and from the thickness of myrmekite and the reaction rim. The width, spacing, and thickness of these textural features increase systematically with elevation; they also increase gradually in the horizontal inward direction in the western part of the pluton but not in the eastern part of the pluton. The systematic variations in textural development indicate that the Toki granite cooled effectively from the roof and from the western margin during the deuteric coarsening stage. The deuteric coarsening may have occurred at temperatures below 500 °C, as indicated by ternary feldspar thermometry.
The effect of dissolved O2 (DO) concentration or partial pressure of atmospheric oxygen (PO2) on the Fe(II) oxidation rate was investigated at room temperature, by changing pH from 6.89 to 8.03 and PO2 from 7.5 × 10-5 to 0.20 atm. The oxidation experiments were conducted in a glove box into which a gas mixture of Ar and Ar + O2 (1%) was introduced continuously to maintain a given DO concentration. The DO concentration was changed by varying the mixing ratio of Ar and Ar + O2 (1%). The decay constant of the oxidation (λ) was estimated from the experimental data, by assuming that the reaction shows pseudo-first-order behavior:
-d[Fe(II)]/dt = λ[Fe(II)] = k [Fe(II)][O2]x[OH-]y,
which indicates λ (k[O2]x[OH-]y) depends on the solution pH and DO concentration. After determining the pH dependence of the oxidation rate (k" = k[OH-]y), we obtained the relationships between the modified rate constant (k' = k[O2]x) and PO2. The relationships revealed that the oxidation rate deviated from the linear dependence (x = 1) at low PO2 (<10-2 atm) and that the oxidation proceeded faster than in the case where x was assumed to be 1. Our results implied that the atmospheric O2 levels (between 2.5 and 2.0 Ga) estimated from the Fe(II) oxidation in paleosols, ancient soils formed by weathering, are overestimated if the x dependence of the oxidation rate is not taken into account.
Philipsburgite, (Cu,Zn)5Zn(AsO4,PO4)2(OH)6·H2O, an As analogue of kipushite, was discovered in the Yamato mine, Yamaguchi Prefecture, Japan. Philipsburgite occurs in the form of spherical aggregates, 0.5 mm in diameter, with bright green in color. It is associated with malachite and cornwallite in cavities of the oxidized rocks, which consist of quartz and goethite. Spherical philipsburgite consists of platy crystals, 100 μm in length and 1 μm in thickness, with sharp termination. The empirical formula is (Cu4.91,Zn0.09)Σ5.00Zn1.00[(AsO4)1.63(PO4)0.37]Σ2.00(OH)6·1.60H2O on the basis of O = 11 in the anhydrous part per formula unit and the water content was measured by thermogravimetric analysis. The composition is closest to the As end member thus far reported. The unit cell parameters from the X-ray diffraction data are a = 12.359(8), b = 9.247(7), c = 10.734(5) Å, β = 97.22(5)° and V = 1216.9(9) Å3.
Four ammonium sulfate minerals, i.e., boussingaultite, godovikovite, efremovite and tschermigite, were found from coal gas escape fractures at Ikushunbetsu, Mikasa City, Hokkaido, Japan, on the field survey in 2009. The minerals were identified using XRD, SEM-EDS, XRF and/or CHN analyses. This is the first occurrence of these four mineral species in Japan. Godovikovite is the most common species in this survey and has Al/(Al + Fe3+) ∼ 0.9. The mineral coexists with efremovite. These usually occur as very fine admixtures (<10 μm) forming porous crust up to several millimeters in thickness. Boussingaultite [Mg/(Mg + Fe) = 0.96 to 0.97] occurs as aggregates of platy crystals up to 1 mm in diameter and 0.2 mm in thickness or as very fine admixtures (<10 μm) with tschermigite forming porous stalactitic-like aggregate. Godovikovite, efremovite and boussingaultite were formed as a primary sublimate from coal-gas. Tschermigite is considered to be a hydration product of godovikovite.
A remarkably high Li/B ratio has been recognized from a crush-leached fluid extracted from a foliation-parallel quartz vein, IR27, intercalated with a pelitic schist in the northern proximal to the Western Iratsu body of the Sambagawa metamorphic belt, SW Japan. Thin section observation shows that most quartz grains in the vein are polygonal and rarely show the undulatory extinction. These facts suggest that the quartz grains in the vein could be recrystallized under relatively high-T condition with the stress free environment, and that these fluid inclusions could be trapped during the peak metamorphic stage. Most fluid inclusions in the investigated sample are composed of liquid and vapor. Raman spectroscopy revealed that the liquid phase is aqueous fluid and the vapor is mainly a mixture of CH4 and N2. Their ice melting temperatures determined by microthermometry, ranging from -3.5 to -7.1 °C, show a striking contrast against the data of the fluid inclusions in later stage veins, ranging from -0.6 to -1.7 °C. However, the homogenization temperatures of IR27 are much lower than the peak metamorphic temperature of the host pelitic schist. The partition coefficients between the host rock and released fluid (Drock/fluid) calculated from P-T pseudosection show that DBrock/fluid tends to be higher than DLirock/fluid in a pelitic system, because of generally high modes of white mica in pelitic schists. The calculation suggests that the crush-leached fluid obtained from the quartz vein intercalated with the pelitic schist has higher Li/B ratio than fluids of those intercalated with the metabasite.
The photoluminescence (PL) properties of four gypsums from three localities, namely, Inner Mongolia (China), Turkey, and Canada, are investigated at room temperature. Under 365-nm excitation, two types of gypsums from Inner Mongolia exhibit different luminescence colors, namely, yellow and cyan-white, and gypsums from Turkey and Canada exhibit yellow and bluish-white luminescence, respectively. The PL spectra of these gypsums consist of continuous sub-bands distributed in all visible wavelengths, and the excitation spectra of these gypsums consist of continuous sub-bands distributed in a wide range of wavelengths, i.e., 200-500 nm. The features of PL and excitation spectra suggest that the origin of luminescence from these gypsums may be luminescent organic substances included into crystals in the growth process rather than the impurity ions substituted for Ca2+.
Thin discordant gabbronorite veins (∼ 0.5 mm to 3 cm in width) occur within remarkably fresh harzburgite boulders of the Sibuyan Ultramafics. The harzburgite host rock displays protogranular to porphyroclastic textures and is dominantly composed of olivine, orthopyroxene with minor amounts of clinopyroxene, spinel and amphibole. The mineral chemistry of the harzburgite is comparable to depleted abyssal peridotites as shown by the Fo content of the olivine (= 90-91) and Cr# of the spinel (= 0.40-0.52). The gabbronorites are coarse-grained adcumulates and comprised of orthopyroxene, plagioclase and amphibole. Plagioclase in the gabbronorites shows high An content whereas both orthopyroxene and amphibole show variable Mg# almost similar to reported values from arc gabbros. The contact between the harzburgite and the gabbronorite veins is demarcated by the formation of secondary orthopyroxene with low Cr2O3 and CaO contents. Clinopyroxene in the harzburgite shows strong enrichment in light rare earth elements (LREEs). Amphibole rimming the clinopyroxene in the harzburgite has similar patterns as the clinopyroxene but with much higher REE abundance. The amphibole in the gabbronorites also shows enrichment in LREEs, Rb, Ba and Ti. We propose that the harzburgite-gabbronorite occurrence in the Sibuyan Ultramafics is a product of mantle-melt reaction. The metasomatic agent is a silicate melt enriched in Si, Cr, Fe and LREEs. At a bigger scale, the harzburgite-gabbronorite connection observed in the Sibuyan Ultramafics possibly documents early stage modification and conversion of abyssal peridotites to ophiolitic peridotites by SSZ-related melts.
Figure 2 of “40Ar/39Ar ages of granitoids from the Truong Son fold belt and Kontum massif in Laos”, by Sanematsu et al. (vol. 106, no. 1, 13-25, 2011), is missing the pattern of Nape Complex (Bt granodiorite and granite). Below is the corrected Figure 2.