Volume 18, Issue 50 (10-2005)
Abstract
Qopi bauxitic horizon is located west of Miandoab, in West-Azarbaidjan, NW of Iran. This stratiform horizon lies along the boundary of Permian carbonates and triassic shales and limestones. The upper Permian uplift exposed the pre-Permian rocks to weathering and bauxitization. Based upon field evidence and petrographic studies, five bauxitic facies are recognized within this horizon. Normative values of constituent minerals and chemical processes characterize the mode of development of bauxitic minerals in this horizon. Chemical data and correlation coefficient show that Al, Ti, Zr, and Nb acted as immobile elements during bauxitization processes. Mass change calculations of elements in the bauxitic units at Qopi indicate that considerable amounts of Si, Ca, Mg, Na, P, and K were leached out from the system. Based upon ratios of immobile elements, the diabasic rocks in the area are the principal source for Qopi bauxitic horizon and at least 17 meters of it was consumed during weathering and bauxitization processes
