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We present osmium isotopic results obtained by sequential leaching of the Murchison meteorite, which reveal the existence of very large internal anomalies of nucleosynthetic origin (ε 184 Os from -108 to 460; ε 186 Os from -14.1 to 12.6; ε 188 Os from -2.6 to 1.6; ε 190 Os from -1.7 to 1.1).Despite these large variations, the isotopic composition of the total leachable osmium (weighted average of the leachates) is close to that of bulk chondrites. This is consistent with efficient largescale mixing of Os isotopic anomalies in the protosolar nebula. The Os isotopic anomalies are correlated, and can be explained by the variable contributions of components derived from the s, r and p-processes of nucleosynthesis. Surprisingly, much of the s-process rich osmium is released by relatively mild leaching, suggesting the existence of an easily leachable s-process rich presolar phase, or alternatively, of a chemically resistant r-process rich phase.

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