Abstract
Zircons from metamorphosed granites exposed near Qinglongshan have δ18OVSMOW values of -7 to 0‰ in both grain rims and cores. The concordant 238U/206Pb ages of zircon cores are 684 to 754 Ma with rims at 221 Ma. Discordant 238U/206Pb ages range from 242 to 632 Ma. Results demonstrate a Neoproterozoic age for the origin of the Qinglongshan oxygen and hydrogen isotope anomaly. The low δ18O values were imprinted on the rocks by a hydrothermal system charged with meteoric water from a cold climate. Groundwater circulation was driven by heat from cooling granitic magma. The geologic age of the hydrothermal thermal system correlates with that of the Nantuo tillite in the Sinian strata of the South China block, suggesting that Qinglongshan's cold climate may be a manifestation of Neoproterozoic "snowball Earth."
Original language | English |
---|---|
Pages (from-to) | 2299-2306 |
Number of pages | 8 |
Journal | Geochimica et Cosmochimica Acta |
Volume | 66 |
Issue number | 12 |
DOIs | |
Publication status | Published - 2002 |
Externally published | Yes |