稀土元素：海相硅岩沉积环境的有效指标

世界范围内海水的REE研究表明,不同环境海水的REE有一定的差异.海相硅质沉积也显示出与周围海水相似的REE特征,其中最明显的是Ce异常。对已知沉积环境的硅岩所作REE研究说明,利用硅岩的REE特征可以帮助判别海相沉积环境。江西南部寒武—奥陶系中广泛产出厚层的层状硅岩,根据Ce的异常,推测此区硅岩形成于大陆边缘—大洋盆地的过渡地区。

RARE EARTH ELEMENTS:THE EFFECTIVE INDICATOR OF DEPOSITIONAL ENVIRONMENTS OF MARINE CHERTS

Researches on seawater REE over the world indicate that REE in the seawaterfrom various environments are different to a certain extent. Marine siliceous depos-its also exhibit a similar REE pattern to those of their surrounding seawater, inwhich Ce anomaly is the most obvious marker. As shown by studies on REE in theancient cherts of the known depositional environments, cherts from the continental-margin environment exhibit slight negative Ce anomaly or positive Ce anomaly andcherts from the ocean--basin environment exhibit obvious Ce anomaly, while chertsfrom the mid--oceanic ridge environment show intense negative Ce anomaly. There-fore the characteristics of the chert REE pattern can be used to distinguish differ-ent depositional environments. According to the Ce anomalies, the thickbedded che-rts occurring extensively in the Cambrian--Ordovitian in southern Jiangxi are infer-red to be formed in a transitional zone between the continental margin and theocean basin.