Alpha-decay of Os-184 revealed by radiogenic W-180 in meteorites: Half life determination and viability as geochronometer

作者：Peters Stefan T M^*; Muenker Carsten; Becker Harry; Schulz Toni

来源：Earth and Planetary Science Letters, 2014, 391: 69-76.

DOI：10.1016/j.epsl.2014.01.030

• meteorites
• (OS)-O-184
• (180)w
• radioactive decay
• planetary differentiation
• geochronometer

The decay of the rare nuclide Os-184 by alpha emission to W-180 has been theoretically predicted, but was previously never observed in experiments. Variable excesses of W-180 were recently observed for iron meteorites, but the contribution to these excesses by Os-184-decay was regarded as insignificant. Here, we present combined W-180 and Os-W concentration data for meteorites and terrestrial rocks, now indicating that the W-180 heterogeneities can be explained by a-decay of Os-184. A combined Os-184-W-180 isochron for iron meteorites and chondrites yields a decay constant value of lambda Os-184(alpha) of 6.49 +/- 1.34 x 10(-14) a(-1) (half life 1.12 +/- 0.23 x 10(13) yr), in good agreement with theoretical estimates. The Os-184-W-180 decay system may constitute a viable tracer and chronometer for important geological processes like core formation, silicate differentiation or late accretion processes. This is illustrated by a measured W-188-deficit in terrestrial basalts relative to chondrites by 1.16 +/- 0.69 parts in 10000, consistent with core formation similar to 4.5 Ga ago.

• 出版日期2014-4-1