SECONDARY DISPERSION FROM GOLD DEPOSITS IN WEST TURKEY

Orientation studies over the Sarpdag prospect in the Biga peninsula an d the Arapdagi deposit near Izmir have provided clear evidence for ele mental dispersion around west Turkish gold prospects. Although these d eposits are of different types, silicification associated with the dep osits results in the main part of both deposits forming topographic hi ghs. At Sarpdag gold mineralisation is relatively weak compared with n earby prospects and associated with a silicified cap on the main hill. Comparison of coarse and fine fractions, based on a 190 mu m size spl it of 8 kg of -2 mm material, suggests that gold disperses elastically on the steep slopes, probably within silica, but coarse grains break down giving Au concentrations in the finer fractions at the base of th e main slope. Discrete gold grains, that can be panned, only occur 1-2 km downstream within the streams and heavy mineral concentrations are very limited. This interpretation of Au dispersion is consistent with the data from 1 kg samples collected at the higher primary grade, but more contaminated, Arapdagi prospect. Antimony is the most consistent pathfinder both for the silicified cap at Sarpdag and for gold-rich v eins at Arpadagi. It gives high contrast anomalies. Arsenic is useful being more mobile than Sb, although contrast may be low. High resoluti on Ag data can be useful but base metal enrichments are also often ass ociated with Ag anomalies. Most prospects have some base metal enrichm ents although they can be displaced from the main gold-rich parts of t he deposit and anomalies may be weak. Lead and Cu are the more consist ently useful elements. The use of large (> 8 kg of -2 mm material) sam ples produces consistent stream sediment data that can be used to reli ably interpret single samples and quantify Au anomalies. A survey arou nd the Halikoy Hg and Emirli Sb mines, using these large samples, conf irmed the extension of the known gold-bearing Emirli structure. In con trast the major Hg-bearing Halikoy Fault is gold poor although a struc ture parallel to it is auriferous.