The Late Cretaceous high-sulfidation Au-Cu Chelopech deposit, Bulgaria: geological setting, paragenesis, fluid inclusion microthermometry of enargite, and isotope study (Pb, Sr, S)

The Au-Cu Chelopech deposit contains geologic, alteration and ore mineralogy features typical of epithermal high sulfidation deposits. Lead and sulphur isotope data demonstrate that an early massive pyrite stage and the main Au-Cu high-sulfidation economic ore are the result of two successive stages of the same metallogenic event. Lead and strontium isotope data indicate either extensive fluid circulation through the basement rocks, or hydrothermal fluids derived from Cretaceous intrusions having assimilated basement rocks. Combined lead isotope systematics and paragenetic sequence reveal an evolution from an early, less radiogenic source reservoir (local volcanic rocks?) to a late, more radiogenic source (basement, porphyry-like?). Fluid inclusions in enargite yield low homogenisation temperatures of 101-126°C, and are interpreted as secondaries.