Isotope and Trace Element Evolution: Responding to Sea-level Fluctuation —An Example of Ordovician in Middle Tarim Basin
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摘要: 海相岩石自生矿物中的锶同位素组成可反映其沉积时期的海平面波动趋势。塔中地区奥陶系87Sr／87Sr分析表明，在早奥陶世海平面总体呈下降趋势，而在中晚奥陶世海平面则持续上升并保持在奥陶纪平均海平面之上。氧同位素分析表明，塔中地区下奥陶统的白云岩主要为低海平面期高盐度环境沉积的准同生白云岩。微量元素分析结果支持同位素研究结论。分析测试表明，锶、氧同位素及一些微量元素均对海平面升降波动具有敏感的反应。Abstract: The Strontium isotope composition of marine autogenetic minerals can reflect the sea level fluctuation trend during the minerals deposited. The analysis of the87Sr/86Sr ratio of Ordovician shows the sea level dropped in Early Ordovician and then rose continuously and stayed above the average level in M iddle and Late Ordovician in middle Tarim area. The study of oxygen isotopes indicates the dolostones of the Lower Ordovician are mainly penecontemporaneous dolostones which deposited in the sedimentary environment of the high salinity of the lower sea level. The trace elements geochemistry draws the same conclusion as that of the study of the isotope analysis. In brief, the variation trend of87Sr/86r ratio was reversely interrelated with the sea level fluctuation. Both oxygen isotopes and some elements made remarkably response to the sea level fluctuation during the O rdovician.
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Key words:
- sea level fluctuation /
- isotopes evolution /
- reverse interrelationship /
- Tarim basin
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