The role of organic matter on the mineralogical and geochemical characteristics of the ‎Dopolan‏ ‏bauxite deposit, Chaharmahal and Bakhtiari Province

Dopolan bauxite deposit is located in the high Zagros zone, between Khaneh-Kat and Neyriz ýFormations. Dopolan bauxite consist of 5 separate layer bauxite, respectively from bottom to top ýincluding, iron rich, clay bearing, oolitic, pisolitic and organic matter-rich bauxite. The aim of this ýstudy is investigation on the role of organic matter in the mineralogy deposition of bauxite ýhorizons. Mineralogical studiesþ þinclusive light microscopy (reflected), electron microscopic (SEM) ýand Raman spectroscopy, revealed presence of diaspore in pisolitic, oolitic, clay bauxitic horizons ýand show presence of pyrite, kaolinite, nacrit, bohemite, minerals in organic matter rich and iron ýrich bauxitic horizons. The micromorphelogical studies show that deferruginization is important ýprocess in the deposit. Iron rich and organic rich bauxite horizons show highest values TOC and ýFe. The most specific feature of iron-rich and organic matter-rich bauxitic horizons is abundant ýof pyrite. Present pyrite was explained by high content of organic carbon. The widespread ýoccurrences of pyrite in these horizons seem to be due to the sulfate reduction by bacteria in ýrelatively organic carbon-rich environment. Distribution of organic matter show that carbon ýcontrol mobilization of Fe and Al during bauxitization. Therefore two environmental condition can ýbe deduced in Dopolan deposit. 1) Environment that Al minerals more soluble than Fe minerals ýý2) Environment that Fe minerals more soluble than Al minerals.