بلورشناسی، کانی‌شناسی و ژئوشیمی گالن، کانسار سرب نخلک (اصفهان)

Nakhlak lead deposit, one of the oldest and largest Iranian lead mines, is located in 55 Km from the northeast of Anarak town. Nakhlak deposit occurs as stratabound and epigenetic in Upper Cretaceous dolomitic carbonates host rocks. The hypogene ore deposits include galena and barite that are associated in supergene zone with cerussite. Galena occurs as coarse and fine grains with replacement and open space filling texture and Cuboctahedral form. Inclusion of independent minerals such as fahlore (Tennantite-Tetrahedrite Series), sphalerite, pyrite and chalcopyrite are present with wide diversity in size and type for different veins in galena. ICP-MS Analysis of galena indicates presence of valuable trace elements such as silver (932 ppm), antimony (342 ppm), copper (422 ppm), arsenic (91 ppm), among which silver is the most important. Low values of Bi and high values of Sb as well as high ratio of Sb/Bi represent the Nakhlak galena formed in low temperature - pressure conditions. XPMA analysis indicates these trace elements are concentrated as inclusions in galena. According to the characteristics of the galena and other geological features, Mississippi Valley-type model is proposed for Nakhlak lead deposit.