Keywords: 
• Mudstone /
• REE contents /
• provenance /
• sedimentary environment /
• Tabei up lift /
• Tarim basin

Abstract: Rare earth element (REE) abundance of Ordovician, Triassic and Jurassic mudstone in the Tabei up lift,Tarim basin has been analysed. All the mudstones show the characteristics of high LREE content, uniform HREE and negative Eu anomaly. The ratios such as ΣLREE /ΣHREE, LaN /YbN , (La /Yb) UCC , Eu /Eu³ and Ce /Ce³, however, are obviously different among them, and thus reflecting the different sources and environments when they were formed. The mudstones formed in different ages display variable degrees of REE differentiation and negative Eu anomaly. The Ordovician mudstones have high ratios of ΣLREE /ΣHREE and LaN /YbN (12.1 and 19.8) and significant negative Eu anomaly ( Eu /Eu³= 0.59). The Triassic mudstones, however, show unusual low ratios of ΣLREE /ΣHREE and LaN /YbN (5.9 and 7.7) and small negative Eu anomaly ( Eu /Eu³= 0.78). The Jurassic mudstones are similar to the Ordovician samp les except less negative Eu anomaly ( Eu /Eu ³= 0.72). Similarly, UCC - normalizedm REE patterns of samples also show significant changeswithin different ages. In general, the Ordovician and Jurassic mudstones show slight enrichment of LREE relative to UCC, whereas the Triassic ones show strong LREE depletion.These characteristics indicate that the Ordovician mudstoneswere formed under a relatively stable sedimentary environ- ment. The sources should be the upper continental crust with high maturity. During Permian - Triassic times, the north of the Tarim basin was tectonic and volcanic, which provide abundant volcanic materials. It stepped into the stable sinking period in Jurssic. The REE difference amongmudstones has indicating significance for studying the formation and evolution of the Tarim basin and surrounding orogenic belt