Sulfur-isotope study of the Ana Yatak massive sulfide deposit, southeastern Turkey

Abstract

The Ana Yatak massive sulfide deposit is located in the Ergani-Maden District of south-eastern Turkey and has been a major source of copper for more than 4,000 years. The mineralization is hosted by strongly chloritized serpentinite, gabbro, diabase, and mudstone. The ore body is similar to 600 x 250 m in maximum dimension, mainly consists of pyrite and chalcopyrite, and locally contains abundant magnetite, pyrrhotite, and chromite. The gangue contains predominantly chlorite, rarely quartz. This paper is mainly concerned with an investigation of the sulfur-isotope systematics of the Ana Yatak deposit. Pyrite and chalcopyrite from the ore and pyrite from the host; rocks were sampled and analyzed to determine their delta(34)S composition. delta(34)S values were found to vary within the range from +4.5 to +9.3 parts per thousand for pyrites (mean delta(34)S = +6.5 +/- 1.8) and from +4.5 to +10.0 for chalcopyrites (mean delta(34)S = +6.7 +/- 1.9) of the ore, and from -5.8 to +8.8 for pyrites (mean delta(34)S = +7.3 +/- 1.3) of the host reck. The delta(34)S compositions of all samples were found to vary from +4.5 to +10.0 parts per thousand. For the chalcopyrite-pyrite pairs, there is a clear relationship of approximately equal delta(34)S values at each sampling site. Frequency distribution of the delta(34)S values is not unimodal and exhibits two peaks. The range of sulfur-isotope systematics implies that the Ana Yatak mineralization was influenced to a greater extent by seawater than by hydrothermal fluids.