CHARACTERISTICS AND GENESIS OF SEDIMENT-HOSTED IRON DEPOSITS IN SANANDAJ-SIRJAN BELT, WEST-CENTRAL IRAN
Deformation and metamorphism have modified the original mineralogy, textures and structures. The iron ore in Mooteh is partly associated with calc-silicate assemblages, and the footwall schists in Chahchaghok contain Fe-rich amphiboles. The ore bodies are locally sheared, boudined and dismembered. Representative samples, analyzed at ACME Labs, Vancouver, are characterized by low TiO2 (<0.1%), P2O5 (<0.2%), Ni, Co, V (up to 10, 15, 120 ppm) and Hf, Nb (<1 ppm) but high and variable MnO (up to 5%). REE display large variations (7-62 ppm) and high LaN/YbNratios (5-20). Ce/Ce* varies between 0.8-1.20; Eu/Eu* is highly variable (0.3-7). A distinct correlation exists between the abundances of Ba and LREE and the Eu/Eu* values.
The iron ores are enriched in Zn, Pb, Cu, Mo (up to 8600, 2300, 760, 38 ppm) and Au, Ag (0.07, 2 ppm). The δ34S values for barite from banded ore in Mooteh and Abpooneh analyzed at GG-Hatch Stable Isotope Labs, University of Ottawa, fall in the range19.5-28‰ and 3.4-6.6‰, respectively, consistent with the Late Proterozoic and modified Triassic marine sulfates and the stratigraphic ages of the associated rocks, respectively. The ore mineralogy, textures and geochemistry suggest a sedimentary-diagenetic origin dominated by chemical precipitation. Ore deposition occurred in a marginal basin with episodic volcanic inputs. The iron deposits may represent the distal or shallow-water and oxidized equivalents of black shale/tuff -hosted exhalative base-metal ores.