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Carbon dioxide released through EDTA dissolution of chrysocolla-rich ore samples from the Huinquintipa (semi-arid Collahausi district) and Mina Sur (hyperarid Chuquicamata district) exotic-type Cu silicate-oxide deposits, northern Chile, has extremely light delta C-13 values (<= -40 parts per thousand) indicative of microbial activity, plausible during distal mineralization. Similar values are herein obtained through EDTA extraction from soil samples taken up to 30 m above a known exotically mineralized palaeochannel between the Huinquintipa deposit and the inferred parental Rosario porphyry copper centre. Moreover, microbiogenic carbon was not evident over areas of established buried hypogene or supergene sulphide mineralization in soil samples from undisturbed sites along a 20 km-long regional east-west traverse through the district. Carbon isotopic analysis of CO2 extracted through EDTA dissolution of soils in semi- or hyperarid settings on the Pacific slope of the Central Andean Cordillera Occidental may therefore specifically assist in the location of buried exotic type Cu deposits.