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Mitsunobu Tatsumoto

Publications and source records attributed to Mitsunobu Tatsumoto.

7 recordsLinked to original sources
USGS2012

Partition coefficients of Hf, Zr, and ree between phenocrysts and groundmasses

Partition coefficients of Hf, Zr, and REE between olivine, orthopyroxene, clinopyroxene, plagioclase, garnet, amphibole, ilmenite, phlogopite, and liquid are presented. Samples consist of megacrysts in kimberlite, phenocrysts in alkaline basalts, tholeiitic basalts and andesitic to dacitic rocks, and synthetic garnet and clinopyroxene in Hawaiian tholeiites. The Hf-Lu and Zr-Lu elemental fractionations are as large as the Lu-Sm or Lu-Nd fractionation. The Hf and Zr partition coefficients between mafic phenocrysts and liquids are smaller than the Lu partition coefficients, but are similar to the Nd or Sm partition coefficients. The Hf and Zr partition coefficients between ilmenite, phlogopite, and liquid are larger than the Lu partition coefficients for these minerals and their corresponding liquids. The Hf-Zr elemental fractionation does not occur except for extreme fractionation involving Zr-minerals and extremely low fo 2 . These data have an important bearing on chronological and petrogenetic tracer studies involving the Lu-Hf isotopic system.

Journal of Geophysical Research Solid Earth↗
USGS2002

Determination of lead, uranium, thorium, and thallium in silicate glass standard materials by isotope dilution mass spectrometry

A set of four standard glasses has been prepared which have been doped with 61 different elements at the 500-, 50-, 1-, and 0.02-ppm level. The concentrations of lead, uranium, thorium, and thallium have been determined by isotope dilution mass spectrometry at a number of points in each of the glasses. The results obtained from independent determinations in two laboratories demonstrate the homogeneity of the samples and that precision of the order of 0.5% (95% L.E.) may be obtained by the method even at the 20-ppb level for these elements. The chemical and mass spectrometric procedures necessary are presented.

Analytical Chemistry↗
USGS1995

Further evidence for a low U/Pb source in the moon: U-Th-Pb, Sm-Nd, and Ar-Ar, isotopic systematics of lunar meteorite Yamato-793169

The coarse-grained lunar meteorites, Yamato-793169 and Asuka-881757, represent a new type of low-Ti mare basalt. This paper reports the results of a U-Th-Pb, Sm-Nd, and Ar-Ar isotopic study of Yamato-793169 performed as part of a consortium studies of lunar basaltic meteorites. The isotopic study was carried out on a small sample (100 mg) so that only three density fractions could be separated. These fractions were leached with dilute acid in order to eliminate terrestrial Pb contamination. However, the leaching procedure did not completely remove this contamination in some fractions and also apparently caused a fractionation of elements (U, Th, Pb) due to preferential leaching effects, producing a secondary disturbance of the systematics. Furthermore, the Ar-Ar analyses indicate that the isotopic systematics in this meteorite might have been disturbed sometime later than 750 Ma. For these reasons, the ages obtained using different isotopic systems disagree with each other and a precise formation age could not be obtained for this meteorite. However, using what results there are, two reasonable interpretations can be made: (1) the Sm-Nd system yielded an age of 3.4 Ga that could be interpreted as the formation age, assuming that this system is possibly the least disturbed during the metamorphic event(s) that this meteorite experienced at least once, and that all other isotopic systems and their corresponding ages were disturbed, and (2) the U-Pb system yielded a nearly concordant age of 3.8 Ga that could be interpreted as the formation age and the Sm-Nd isotopic systematics were somehow disturbed. We prefer the second interpretation for the reasons discussed below. On a concordia diagram, the CDT (Cañon Diablo troilite)-corrected U-Pb isotopic data yield a discordia line similar to the lunar catastrophic array, indicating that the source of the meteorite formed during early lunar differentiation (∼4.4 Ga) and that the basalt was generated near 3.9 Ga. Total Ar-Ar age on plagioclase is 3.26 Ga, which seems to be too old if the formation age is 3.4 Ga, because low temperature fractions lost large amounts of radiogenic 40 Ar during the late thermal event. If we assume a formation age of 3.8 Ga, the estimated source 238 U/ 204 Pb (μ) is 21.6 ± 3.5 and ϵ Nd is 3.9 ± 0.3. These results indicate that the source of Yamato-793169 is more depleted than Apollo 12 and 15 LT basalts, but less depleted than Asuka-881757. Therefore, Yamato-793169 may represent a new type of LT- or VLT-like mare basalt that is different from Asuka-881757. The wide variety of lead and neodymium isotopic characteristics among LT and VLT mare basalts indicate that the lunar mantle was very heterogeneous with respect to trace element abundances.

Geochimica et Cosmochimica Acta↗
USGS1985

Origin of the Sudbury Complex by meteoritic impact: Neodymium isotopic evidence

Samarium-neodymium isotopic data on whole rocks and minerals of the Sudbury Complex in Canada gave an igneous crystallization age of 1840 ± 21 × 10 6 years. The initial epsilon neodymium values for 15 whole rocks are similar to those for average upper continental crust, falling on the crustal trend of neodymium isotopic evolution as defined by shales. The rare earth element concentration patterns of Sudbury rocks are also similar to upper crustal averages. These data suggest that the Sudbury Complex formed from melts generated in the upper crust and are consistent with a meteoritic impact.

Ontario↗
USGS1969

Isotopic composition of lead in volcanic rocks from central Honshu — with regard to basalt genesis

The isotopic composition of lead and concentrations of lead, uranium, and thorium were determined in tholeiitic and high-alumina basalts, and their calc-alkali rock series, from central Japan. The isotopic composition of lead of high alumina basalts is similar to that of tholeiites from adjacent areas, whereas their silicic differentiates (calc-alkali rock series) are rich in 207 Pb and 208 Pb. This is interpreted as a result of crustal contamination. The isotopic composition of lead in the primary basalts gradually decreases in radiogenic character from the Pacific Ocean side to the Japan Sea side, whereas the observed 238 U/ 204 Pb and 232 Th/ 238 U ratios in the basalts increase in the same direction. This inverse correlation can be interpreted as resulting from differentiation of the upper mantle about 3.6b.y. ago, with tholeiite (Pacific side) generated from a shallower zone than the alkali basalt (Japan Sea side). The magma generation is associated with a process which extracts Pb preferentially to U and Th at shallower depth and U and Th preferentially to Pb at deeper depth in the past (multi differentiation for the source region) or at the magma generation stage. An alternative interpretation of this inverse correlation is that the ocean floor is being thrust under the Japanese Island arcs and the isotopic difference is produced by the degree of mixing of mantle material under the arcs with thrust material.

Honshu↗