Rare earth element study on scheelites from tungsten deposits in southwest of Astaneh, Arak, Iran

Two types of tungsten mineralization have been recognized in southwest of Astaneh: 1. Stratabound type at Bamsar with calcareous schists and siliceous tuffs as host rocks, 2. Quartz-tourmaline vein type at Nezamabad, Revesht and Fizaneh hosted in quartzdiorite-granodiorite intrusions. Scheelite is the main tungsten ore mineral in both types. Generally, two distinct REEN patterns are observed in the scheelites from the region: Nezamabad, Revesht and Fizaneh patterns have a convex feature varying from Eu-free to highly negative Eu anomaly, having high Na and ΣREE contents. The samples are enriched in HREE. Bamsar type REEN pattern has lower ΣREE and Na, a relatively flat feature and small to large positive Eu anomalies. The samples are enriched in LREE. According to the REE trends, presence of high-temperature minerals, exsolution textures, presence of organic and graphitic parts, the two types of mineralization share a high temperature and reducing environment, but some differences lie in REE controlling processes. Surface absorption at Bamsar and mixing of complexes mechanism at Nezamabad, Revesht and Fizaneh control the REE patterns. Therefore, it can be concluded that the origin of REE in scheelites in the mineralized areas of Bamsar, Nezamabad, Revesht and Fizaneh share the same source and the differences in ΣREE result from the influence of host rocks in the areas with vein-type mineralization.