Vice Professor LI Qiuli and his team research the method of determining the ago of low-temperature eclogites. Previous geochronological results of the low-temperature eclogites are controversial due to Sm–Nd and Rb–Sr isotopic disequilibrium in different mineral fractions.

In the study, they measure U–Pb rutile age data using SIMS (Cameca IMS 1280) for low-temperature eclogites from southwestern Chinese Tianshan orogen, NW China. SIMS U–Pb rutile dating yielded an age of 318±7 Ma, which may record the time when the rocks cooled down to the closure temperature of Pb in rutile (ca.500 °C), but should be very close to the time of eclogite-facies metamorphism in terms of common fast exhumation of coesite-bearing eclogite. This new proof strongly suggests a late Carboniferous collision

between Kazakhstan–Yili block and Central Tianshan microcontinent.

Their paper has published in Lithos. Li et al. SIMS U-Pb rutile age of low-temperature eclogites from southwestern Chinese Tianshan, NW China. Lithos, 2011, 122: 76-86 (Download Here)

Fig. Calibration curves for SIMS rutile U–Pb analyses. (Image by LI Qiuli)

Fig.. U–Pb age concordia diagram for rutile from eclogite at SW Chinese Tianshan. (Image by LI Qiuli)