Low δ18O zircons, U-Pb dating, and the age of the Qinglongshan oxygen and hydrogen isotope anomaly near Donghai in Jiangsu Province, China
Low δ18O zircons, U-Pb dating, and the age of the Qinglongshan oxygen and hydrogen isotope anomaly near Donghai in Jiangsu Province, China
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DOI：
10.1016/s0016-7037(02)00844-x
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发表时间：
2002-06
影响因子：
5
通讯作者：
D. Rumble;D. Giorgis;T. Ireland;Zeming Zhang;Hui-Long Xu;T. Yui;Jingsui Yang;Zhiqin Xu;J. Lio
中科院分区：
文献类型：
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作者：
D. Rumble;D. Giorgis;T. Ireland;Zeming Zhang;Hui-Long Xu;T. Yui;Jingsui Yang;Zhiqin Xu;J. Lio
青龙山附近出露的变质花岗岩中的锆石，其颗粒边缘和核心的 δ18OVSMOW 值为 -7 至 0 ‰。锆石岩心的 238U/206Pb 一致年龄为 684 至 754 Ma，边缘为 221 Ma。不一致的 238U/206Pb 年龄范围为 242 至 632 Ma。结果表明青龙山氧氢同位素异常的起源年龄为新元古代。低 δ18O 值是由充满来自寒冷气候的大气水的热液系统在岩石上留下的印记。地下水循环是由冷却的花岗岩岩浆产生的热量驱动的。热液系统的地质年龄与华南地块震旦纪地层中的南沱砬岩年龄相关，表明青龙山寒冷的气候可能是新元古代“雪球地球”的表现。
Zircons from metamorphosed granites exposed near Qinglongshan have δ18OVSMOWvalues of −7 to 0‰ in both grain rims and cores. The concordant238U/206Pb ages of zircon cores are 684 to 754 Ma with rims at 221 Ma. Discordant238U/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 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.”