I-Xe dating of silicate and troilite from IAB iron meteorites

Thesis/Dissertation · Sat Dec 31 23:00:00 EST 1977

OSTI ID:6149599

Niemeyer, S

The IAB iron meteorites may be related to the chondrites; siderophile elements in the metal matrix have chondritic abundances, and the abundant silicate inclusions are chondritic both in mineralogy and in chemical composition. Silicate and troilite (FeS) and IAB irons were analyzed by the I-Xe technique. Four IAB silicate samples gave well-defined I-Xe ages (in millions of years relative to Bjurboele; the monitor error (+-2.5 m.y.) is not included): -3.7 +- 0.3 for Woodbine, -0.7 +- 0.6 for Mundrabilla, +1.4 +- 0.7 for Copiapo, and +2.6 +- 0.6 for Landes. The (/sup 129/Xe//sup 132/Xe)/sub trapped/ ratios are consistent with previous values for chondrites, with the exception of Landes which has an extraordinary trapped ratio of 3.5 +- 0.2. Both analyses of silicate from Pitts gave anomalous I-Xe patterns: intermediate-temperature points defined good correlations but higher-temperature (greater than or equal to 1400/sup 0/C) points lay above (extra /sup 129/Xe) these lines. The two correlations have different slopes, so it cannot be assigned a definite I-Xe age to Pitts silicate. Troilite samples from Mundrabilla and Pitts were also analyzed: Pitts troilite gave a complex I-Xe pattern, which suggests an age of +17 m.y.; Mundrabilla troilite defined a good I-Xe correlation, which after correction for neutron capture on /sup 128/Te an age of -10.8 +- 0.7 m.y. Thus, surprisingly, low-melting troilite substantially predates high-melting silicate in Mundrabilla. Abundances of Ga, Ge, and Ni in metal from these meteorites are correlated with I-Xe ages of the silicate (referred to henceforth as the metal-silicate correlation). After exploring possible relationships between the I-Xe ages and other properties of the IAB group, it was concluded that the metal-silicate correlation, the old Mundrabilla troilite, and other results favor a nebular formation model (e.g. Wasson, 1970a).

• Research Organization: California Univ., Berkeley (USA)
• OSTI ID: 6149599
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
AGE ESTIMATION
CHALCOGENIDES
CHONDRITES
DAYS LIVING RADIOISOTOPES
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GALLIUM
GERMANIUM
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IRON COMPOUNDS
IRON METEORITES
IRON SULFIDES
ISOMERIC TRANSITION ISOTOPES
ISOTOPE DATING
ISOTOPE RATIO
ISOTOPES
METALS
METEORITES
MINERALS
NICKEL
NUCLEI
OXYGEN COMPOUNDS
PYRRHOTITE
RADIOISOTOPES
SILICATES
SILICON COMPOUNDS
STABLE ISOTOPES
STONE METEORITES
SULFIDE MINERALS
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TROILITE
XENON 129
XENON 132
XENON ISOTOPES