Datowanie metamorfizmu z początku Układu Słonecznego: wiek U-Pb apatytu z meteorytu Leoncin (chondryt zwyczajny LL5-6 o charakterze brekcji monomiktycznej)

The U-Pb system is a useful chronometer for understanding the formation history of chondritic materials. Modern studies showed that the formation ages of chondrites (4.55–4.56 Ga) effectively equal the formation age of the solar system. Recently, researchers have undertaken U-Pb isotopic studies of phosphates separated from equilibrated ordinary chondrites, which are the major hosts for U and are enriched by an order of magnitude or more relative to the bulk rock (typical U concentrations of 0.1–3 ppm in phosphates). The observed Pb-Pb model ages for these phosphates range from 4.563–4.502 Ga, with an analytical precision of 1 Ma and the U-Pb system is apparently concordant. They also argued that the Pb-Pb ages of the phosphates from several H chondrites show a negative correlation with metamorphic grade. They concluded that thermal processing of the equilibrated chondrites took place over a 60 Ma interval and grain size of the phosphates increases with the degree of metamorphism. In the Leoncin meteorite, apatite reveal the 207Pb/206Pb age, which is 4549±61 Ma. The obtained apatite age in the Leoncin meteorite reflects the early solar system formation process. Moreover, the age is an example of the early solar system metamorphism, which confirms a slightly younger event of secondary changes of the parent body for this meteorite. It is also the first isotopic age of a Polish meteorite.