Yu Hariya

Mixing behavior in quaternary garnet solid solution and an extended Ellis and Green garnet-clinopyroxene geothermometer

Applications of the different formulations of garnet-clinopyroxene geothermometers to crustal granulites and particularly to metamorphosed manganese formations show a wide scatter of estimates. This is primarily related to the uncertainty associated with the formulation of the activity-composition relationship in garnet solid solution besides that in the clinopyroxene solid solution. The largest uncertainty appears to have resulted from the adopted Mg-Mn interaction parameter in garnet which is yet to be experimentally determined. A fresh statistical regression of eleven pairs of garnet and clinopyroxene equilibrated at identical P-T conditions from a manganese formation in India yields WMg-MnGt(=WMn-Mg) value of 1600±500 cal/mols. An extension of the Ellis and Green (1979) geothermometer, known to work well in normal granulites, incorporating terms associated with the activity coefficients of the exchangeable cations, now yields consistent temperature estimation from normal granulites as well as from metamorphosed manganese formations. The geothermometer, however, will not work well for garnet having XFe≥0.65 and clinopyroxenes containing appreciable Na, Al and/or Fe3+.

Stability of richterite50-tremolite50 solid solution at high pressures and possible presence of sodium calcic amphibole under upper mantle conditions

Abstract High pressure experiments have been made on the stability of richterite 50 -tremolite 50 solid solution by the piston-cylinder type high pressure apparatus in the pressure range from 15 to 40 kb, at temperatures from 700 to 1150°C. This amphibole is stable up to 40 kb at 700°C, and the breakdown pressure gradually decreases with increasing temperatures. It is suggested that this amphibole, on the basis of high pressure experiments, may occur in the upper mantle.

Recent manganese oxide deposits in Hokkaido, Japan

Abstract Recent manganese oxide deposits and manganese-bearing hot-spring waters from Hokkaido, Japan have been studied. There are many active hot-springs in the volcanic zones in Japan and stable isotope data (δD) show that the hot-spring water is derived from surface water. Some hot-spring waters precipitate manganese oxides. They are black, soft and muddy. SEM micrographs show a pipe structure coated by manganese oxides which indicates the role of microorganisms in manganese precipitation. X-ray powder diffraction reveals that they consist of todorokite or birnessite. Pyrolusite is not a primary product from hot-spring waters, but a recrystallized product in the post-depositional environment. Manganese oxides alternated with calcareous sinter and are crusty and consist of rancieite. The concentration of heavy metal elements in manganese oxide is controlled by the crystal structure of magnanese oxide minerals present in the deposits and todorokite contains the most heavy metal elements. REE concentration varies widely and the negative Ce anomaly is an indicator of depositional rate.

Hydrogen isotopic composition of MnO(OH) minerals from manganese oxide and massive sulfide (Kuroko) deposits in Japan

The hydrogen isotopic composition of structural water in MnO(OH) minerals from manganese oxide and massive sulfide deposits (Kuroko) in Tertiary formations fall within a narrow range from -261 to -275 permil relative to standard mean ocean water (SMOW). The δD of two manganites from manganese deposits in Paleozoic formations were -236 and -298 permil, indicating a wider range than in those of Tertiary manganese deposits. The MnO(OH) minerals are more deuterium-depleted. than any other hydrothermal minerals reported to date.Hydrogen isotopic fractionation factors between manganite and water were experimentally determined to be 0.7894, 0.7958, and 0.8078 at 150°, 200°, and 250° C, respectively, under hydrothermal conditions at 500 bars. The present experimental results indicate that if manganites were formed at temperatures below 250° C under isotopic equilibrium conditions, then most manganite mineralization in the ore deposits must have precipitated from meteoric hydrothermal solutions.

Todorokite with Long Spacing and Structure of Manganese Dioxide Minerals

Re-examination of X-ray powder diffraction of todorokite from the Todoroki mine was carried out. We recognize that the diffraction peak of 19.3 A shows the existence of long spacing in the direction of c axis. Calculated unit cell parameters are as follows, a=9.79 A, b=2.86 A, c=19.50A.Todorokite from Urizukuri, Yamaguchi Prefecture also have 19.3A diffraction peak. Such a long spacing may be common in todorokite structure.

Deuterium/Hydrogen Ratios and Water Content of Some Silicate Melts at High Pressure

Various approaches have been made by different workers to determine the role of water in the mantle or the lower crust. For example, Kuroda et al. [1] determined the water content of some hydrosilicate minerals under high pressure and high temperature conditions. The stability field of some hydro-silicate minerals was studied by Kushiro [2], Kushiro et al. [3], Lambert and Wyllie [4], Hariya et al. [5,6] and others. The investigations of the role of water on the magma genesis (Allen et al. [7], Kushiro [8], and Burnham and Davis [9]) and the hydrogen and oxygen isotope frac-tionation of hydrous minerals (Kokubo et al. [10], Sheppard and Epstein [11], and Kuroda et al. [12]) also provide valuable information as to the concentration of water in the upper mantle or the lower crust.

Hydrogen-isotopic composition of some hydrous manganese minerals☆☆☆

Abstract Initial data on the hydrogen-isotopic compositions in hydrous Mn minerals from various occurrences fall in a wide range from −298 to −84‰, relative to SMOW. δ D-values of todorokite and cryptomelane from Tertiary deposits show −89 and −150‰. 10a-manganite and δ-MnO 2 from deep-sea nodules have relatively restricted δ D-values ranging from −96 to −84‰. The δ D-values for manganese bog ores from recent hot springs show almost −105‰. It is recognized that the isotopic values obtained for the deep-sea nodules and recent bog ores are slightly different ranged. Manganite and groutite are unique in their hydrogen-isotopic compositions, having the most depleted δ D-values ranging from −298 to −236‰. MnO(OH) minerals are more deuterium-depleted hydrous minerals than any other hydrothermal minerals from various ore deposits. Hydrogen-isotope fractionation factors between manganite and water were experimentally determined to be 0.7894, 0.7958 and 0.8078 at 150°, 200° and 250°C, respectively. the present experimental results indicate that if manganites were formed at temperatures below 250°C, under isotopic equilibrium conditions, most of the manganite mineralization in the Tertiary manganese deposits must have precipitated from meteoric hydrothermal solutions.