Geochemical investigation of rare earth elements and its relationship to auriferous ore-forming fluids in Senjedeh mine district, central Iran

Muteh gold mining district is located 60 km southwest of Delijan in the central part of the Sanandaj-Sirjan zone (SSZ). It consists of two main ore deposits, including the Chah Khatoon and Senjedeh open pits, and several smaller occurrences. Rock units exposing in the area underwent greenschist to lower amphibolite metamorphism. They consist of NW-SE trending deformed and metamorphosed volcano-sedimentary and acidic volcanic rocks. The gold mineralization in the study area occurred as quartz- sulfide veins and veinlets along N40W tending, NE dipping normal faults in metarhyolite host rock. Geochemical behavior of gold and associated elements in mineralized and altered samples indicates that among the major elements, S, Si and among the trace elements Ag, Te, Th, Bi, Ba increasing with the concentration of gold. The concentration of REE and the spider diagram of the samples from altered and mineralized zone and comparison with unmineralized sample indicate a general increasing enrichment for the all REE especially in LREE in the altered and mineralized zone. LREE enrichment in gold mineralization samples indicates the effect of hydrothermal reduced fluids enriched in sulfur, silica and CO2 on concentration of volatile and mobile elements (LREE) during active tectonic of the region. The negative correlation between gold and HREE elements is probably due to the fluoride fluids that washed and carried these elements.