巴楚寒武—奥陶系碳酸盐岩微量元素及沉积环境

Trace Elements and Sedimentary Settings of Cambrian-Ordovician Carbonates in Bachu Area, Tarim Basin

研究了塔里木盆地巴楚地区寒武-奥陶系海相碳酸盐岩的微量元素特征,探讨了微量元素的富集机制。分析表明,微量元素的富集与原始沉积环境有着极为密切的关系押微量元素K、Na、Al、Fe等含量在开阔台地和台地边缘浅滩均较低,而在台地斜坡带较高;Mn、Cr、Ni、V等元素的含量从浅水到深水总体呈增加之势,因此可以指示古水深的变化。常量元素w(Ca)/w(Mg)比值在以白云岩为主的蒸发台地、局限台地相中最低,在潮下开阔台地、台地边缘浅滩沉积中则由于白云岩不发育而比较高。开阔台地相w(Sr)/w(Ba)比值较高,而局限台地相、蒸发台地相则相对较低。碳酸盐岩的微量元素结合常量元素分析可以作为沉积环境判别的有效的标志。

The trace element characteristics of Cambian-Ordovician carbonates in Bachu area of Tarim basin are studied, and their enrichment mechanisms are discussed. The results show that the enrichment of trace elements is closely related to the original sedimentary settings. The contents of trace elements as K, Na, Al and Fe are relatively low in open platform and platform marginal shoal in comparison with relatively high contents in the slope zone. Trace elements as Mn, Cr, Ni and V trend towards increases from shallow to deep water sedimentary settings, thus could be used to indicate relatively changes of paleo-water depth. The w(Ca)/w(Mg) ratio of major elements is relatively low in dolomite-dominated evaporate platform and restricted platform facies, while relatively high in open platform and platform marginal shoal deposits where dolomite is not developed. The w(Sr)/w(Ba) ratio of open platform facies is relatively high, while relatively low in dolomite-dominated evaporate platform and restricted platform facies. Hence, the trace elements together with major elements of carbonates could be used as effective mark for identification of the sedimentary settings in this area.