Primary and secondary halos in weathered and oxidized rocks - an exploration study from Mykonos,Greece

Barite, iron oxide, sulphide, and argentiferous base metal veins occur within the granitic basement of the island of Mykonos, Greece; these veins horsetail where they enter outliers of volcanic-sedimentary rocks which are impregnated with sulphides. Surface rock geochemical surveys were conducted on a regional scale of one sample per 2 to 3 km² and on a local detailed scale down to sample intervals of 25 m; in addition, samples were taken from underground workings and diamond drill core. Major surface halos, kilometres in extent, occur, whereas underground dispersion around veins is limited to a few tens of metres. This apparent contradiction is attributed to the extreme oxidative weathering and local topography. The regional scale surface anomaly is attributed to secondary dispersion in weathered rocks.