K/Ar dating and stable isotope analysis of the Baszkówka and Mt. Tazerzait L5 chondrites

Stanisław Hałas, Artur Wójtowicz

Abstract


We have determined  the content of 40Ar* (1.49 nmol/g) and 4He (1.75 nmol/g) in the Baszkówka meteorite by static vacuum mass spectrometry. The radiogenic argon content was calculated from the measured argon spectrum using the equation: 40Ar* = 40Ar – 295.536Ar assuming a potassium content of 680 ppm wgt. We have obtained K/Ar ages of 3.78 Ga for the chondrules and 3.47 Ga for a bulk sample of Baszkówka. A similar 4He content (1.47 nmol/g) but larger 40Ar* (2.32 nmol/g) content was found for the Mt. Tazerzait bulk sample. The K/Ar age of this meteorite on the basis of the K content (732 ppm) is 4.34 Ga. Sulphur isotope analysis of troilite specimens from both meteorites reveals essentially negative d34S values: –1.25±0.06‰ for Baszkówka and –1.18±0.06‰ for Mt. Tazerzait expressed on the V-CDT scale. This indicates that both chondrites may have a common origin. The oxygen isotope data (d18O = 4.88±0.03‰ and d17O = 3.66±0.10‰) suggests that Baszkówka belongs to the L chondrites.

 


Keywords


Baszkówka; Mt. Tazerzait; chondrites; K/Ar ages; oxygen isotopes; sulphur isotopes

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