Details

Autor(en) / Beteiligte

• CHEN, Daogong

Titel

Preliminary study of microscale zircon oxygen isotopes for Dabie-Sulu metamorphic rocks: Ion probe in situ analyses

Ist Teil von

• Chinese science bulletin, 2003-08, Vol.48 (16), p.1670-1678

Ort / Verlag

School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China%CRPG-CNRS, Nancy 54501, France

Erscheinungsjahr

2003

Beschreibungen/Notizen

• P5; 151 in situ analyses of oxygen isotopes were carried out by ion micro-probe for zircons from 8 localities of HP-UHP metamorphic rocks including eclogites in the Dabie-Sulu terrane. The results show significant heterogeneity inδ18O values, with variation in different rocks from -8.5‰ to +9.7‰ and within one sample from 2‰ to 12‰. No measurable difference inδ18O was observed between protolith magmatic (detrital) zircons and metamorphic recrystallized zircons within analytical uncertainties from the ion micro-probe measurements. This indicates that the metamorphic zircons have inherited the oxygen isotopic compositions of protolith zircons despite the HP to UHP metamorphism. According to their protolith ages from zircon U-Pb in situ dating by the same ion micro-probe, two groups of oxygen isotope composition are recognized, with one having δ18O values of 6‰-7‰ for old protolith of 1.9-2.5 Ga ages and the other 0‰-2‰ for young protolith of 0.7-0.8 Ga ages. The latter anomalously lowδ18O values of zircons indicate that the magma has had the obvious involvement of meteoric water when forming the young protolith of high-grade metamorphic rocks. This may be correlated with the snowball Earth event occurring in South China and the world elsewhere during the Neoproterozoic.