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Browsing Геология России by Author "Nagahara H."

Now showing items 1-9 of 9

A SHORT DURATION OF CHONDRULE FORMATION IN THE SOLAR NEBULA: EVIDENCE FROM 26AL IN SEMARKONA FERROMAGNESIAN CHONDRULES

Kita N.T.; Togashi S.; Morishita Y.; Nagahara H. (2000)

The 26Al–26Mg systems of five ferromagnesian chondrules from the least metamorphosed ordinary chondrite Semarkona (LL3.0) were studied using a secondary ion mass spectrometer. Their glass or plagioclase portions contain ...
CHEMICAL AND ISOTOPIC FRACTIONATIONS BY EVAPORATION AND THEIR COSMOCHEMICAL IMPLICATIONS

Ozawa K.; Nagahara H. (2001)

A kinetic model for evaporation of a multi-component condensed phase with a fixed rate constant of the reaction is developed. A binary system with two isotopes for one of the components undergoing simple thermal histories ...
EVAPORATION OF FORSTERITE IN H2 GAS

Nagahara H.; Ozawa K. (1996)

Kinetics of evaporation of forsterite in hydrogen gas was investigated by high temperature vacuum experiments in the pressure range plausible for the solar nebula. The evaporation rate at total pressure (Ptot) below 10-6 ...
EXPERIMENTAL STUDY OF INCONGRUENT EVAPORATION KINETICS OF ENSTATITE IN VACUUM AND IN HYDROGEN GAS

Tachibana S.; Tsuchiyama A.; Nagahara H. (2002)

Variations in bulk Mg/Si ratios in the various groups of chondritic meteorites indicate that Mg/Si fractionation occurred in the primitive solar nebula. Enstatite (MgSiO3) evaporates incongruently forming forsterite (Mg2SiO4) ...
ISOTOPIC FRACTIONATION AS A PROBE OF HEATING PROCESSES IN THE SOLAR NEBULA

Nagahara H.; Ozawa K. (2000)

Development of isotopic fractionation in a condensed phase during congruent evaporation by abrupt heating is modeled to estimate heating conditions in the solar nebula. Effects of elemental diffusion in the condensed phase, ...
KINETIC AND EQUILIBRIUM MASS-DEPENDENT ISOTOPE FRACTIONATION LAWS IN NATURE AND THEIR GEOCHEMICAL AND COSMOCHEMICAL SIGNIFICANCE

Young E.D.; Galy A.; Nagahara H. (2002)

The mass-dependent fractionation laws that describe the partitioning of isotopes are different for kinetic and equilibrium reactions. These laws are characterized by the exponent relating the fractionation factors for two ...
KINETICS OF DIFFUSION-CONTROLLED EVAPORATION OF FE-MG OLIVINE: EXPERIMENTAL STUDY AND IMPLICATION FOR STABILITY OF FE-RICH OLIVINE IN THE SOLAR NEBULA

Ozawa K.; Nagahara H. (2000)

Evaporation is a process that caused chemical fractionation in the solar nebula. The evaporation rates of meteorite-forming minerals and silicate melts are key parameters for constraining the timescale of high temperature ...
NON-RAYLEIGH OXYGEN ISOTOPE FRACTIONATION BY MINERAL EVAPORATION: THEORY AND EXPERIMENTS IN THE SYSTEM SIO2 - EXPERIMENTAL DATA IN THE SYSTEM MGO-SIO2-H2 TO 1.0 X 10-9 BAR AND 1870°C WITH VARIABLE OXYGEN FUGACITY

Young E.D.; Nagahara H.; Mysen B.O.; Audet D.M. (1998)

Experiments demonstrate that partial evaporation of solid silica at 1600-1700°C and low pressure (10-9 bar) results in enrichment of 18O/16O and 17O/16O in solid products. Evaporative residues formed in H2 or N2 gas at ...
THE RELATIVE FORMATION AGES OF FERROMAGNESIAN CHONDRULES INFERRED FROM THEIR INITIAL ALUMINUM-26/ALUMINUM-27 RATIOS

Mostefaoui S.; Kita N.T.; Togashi S.; Tachibana S.; Nagahara H.; Morishita Y. (2002)

We performed a systematic high-precision secondary ion mass spectrometry 26Al-26Mg isotopic study for 11 ferromagnesian chondrules from the highly unequilibrated ordinary chondrite Bishunpur (LL3.1). The chondrules are ...

Browsing Геология России by Author "Nagahara H."

Browsing Геология России by Author "Nagahara H."

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