Effective Factors on Environmental distribution of trace elements in the ChahMorra Cu Occurrence, Shahrood

The Chah Morra Cu occurrence is located between 15 to 20 km north of Toroud village, south of Shahrood. In this area, Cu deposits are hosted by the andesitic sequence and most of rocks in this area are composed of andesite. Veins contain minerals such as digenite, bornite, covellite, malachite, cuprite, tenorite, native copper and Fe oxide and hydroxides. Also some orthomagmatic magnetite and chalcopyrrhotite are observed in polished sections. Study of heavy minerals shows that some minerals such as magnetite, titanomagnetite, hematite, limonite, oxidized pyrite, pyroxene, amphibole, epidote, oligist, ilmenite, zircon, apatite, barite and rutile are accumulated in stream sediments. Studies on 65 stream sediment samples analyzed for 44 elements by using ICP-OES method indicates that the Cu mineralization have not polluting effect, however the Chah Morra stream sediments indicate enrichment factor values higher than 1 for some elements including Bi, Co, Cu, Fe, Nb, Ni, Rb, U, Yb. Also the data higher than the standard values show that Cr, Pb, Sc and W in addition to above-mentioned elements are higher than the standard values. Calculation of Igeo shows that the Bi and Nb (second class of pollution), are among the pollutant elements in this area. Calculation of correlation coefficient and dendrogram shows that the pollutant elements aren’t related to copper. Studies on Cu pollution was carried out on 276 litho-geochemical sample analyses. Analytical results show that contaminated points are accompanied by volcanic conglomeratic section (that include copper mineralized cobbles) and mineralized veins as the natural cause of pollution. Also distribution of Cu had been affected by the human activities such as historical and artisanal mining works. Fe contamination in the area is attributed to the alteration of andesitic rocks.