Incorporation of As, Sb and Tl in pyrite from the epithermal Kandilka prospect, Eastern Rhodopes, south Bulgaria

The major and trace-element chemistry of two pyrite generations (Py1 and Py2) from the Kandilka epithermal prospect was studied by EDS-scanning electron microscopy and laser ablation ICP-MS techniques. Both generations of pyrite are distinguished by occurrence and chemical properties. Pyrite from the first generation (Py1) is established as trace-element poor, sub- to euhedral (mainly single) crystals up to 200 µm. The later As-bearing pyrite (Py2) forms fine-grained semi-massive aggregates with increased contents of trace-elements. Except for arsenic, Py2 is enriched in gold and antimony. The As content of Py2 increases in an oscillatory manner from core to rim, reflecting changes in As activity and the chemical evolution of ore-bearing fluids. The oscillatory-zoned pyrite is composed of complex rhythmic overgrowths of alternating As-rich and As-poor bands. Positive correlation between As- and Au-content in Py2 is characteristic. According to the current results, the Kandilka prospect could be concerned as a low-sulphidation deposit.