The genesis of Late Triassic allochthonous karst-type bauxite deposits of the Kisejin area, Ab-e-Garm district, Iran

摘要

Bauxite deposits in the Kisejin area, western Iran, occur in karst sinkholes and are considered to be allochthonous originating from neighboring volcanic rocks. The bauxite deposits unconformably overlay the dolomites of the early to middle Liassic Elika Formation as lenses and smaller karsts and are covered by Rhaetian to Liassic shales and sandstones. Two profiles were sampled: the Beyglar profile and an unnamed section. Diaspore is accompanied by anatase in the ore. Kaolinite, hematite and minor illite, quartz and chlorite are also observed. Trace elements tend to associate with diaspore (Cr) and Anatase (Nb, Zr, V). The Beyglar bauxite does not indicate zonation within its profile but the unnamed profile shows zonation (from top to bottom): light grey argillite, white bauxite, red bauxite and red argillite. It seems that the sinkhole, in which the Beyglar profile formed, was filled twice.