Lead and sulfur isotopic studies of the barite-galena deposits in the Karalar area (Gazipasa-Antalya), Southern Turkey

Abstract

The Gazipasa area is covered by Paleozoic-Lower Mesozoic metaclastics and metacarbonates of the Antalya tectonostratigraphic unit, and contains carbonate-hosted lead-zinc and barite deposits. The Buyuk and Boyalik mines investigated in this study contain ore veins and veinlets of barite (80-85%) and galena (10-15%) with small amounts of sphalerite, pyrite, tetrahedrite, limonite, quartz, and calcite. Textural evidence indicates that barite was formed and mylonitized prior to the precipitation of sulfides. The latter occurred in the porous zones between the brecciated barite crystals, especially in the highly mylonitized zones. Sulfur isotopic studies indicate that the sulfur in barite and galena have been derived from different sources. The isotopic composition of sulfur in barite is very different from the sulfur in the Paleozoic rocks of the area, and resembles sea water sulfates and/or sulfate minerals from Late Triassic to the present, while the sulfur of H2S, dissolved in the hydrothermal fluid which precipitated the galena, has a similar isotopic composition to the calcareous rocks of the surrounding Paleozoic formations. Lead isotopic studies indicate that the lead in galena was derived from an upper crustal source with higher U-238/Pb-204 and Th-232/Pb-204 ratios than the average for continental crust. The Pb-isotope model ages for these deposits, range from 434 to 345 Ma (average value is 372 +/- 62 Ma), indicate a Late Ordovician to Lower Carboniferous age. These Pb isotope model ages are not in accordance with the geological data which indicate a Post-Triassic age for the mineralization. The sulfur and lead isotope results suggest that the sulfur in the barite was leached from a Late Triassic to Recent sulfate reservoir, while the sulfur and lead in galena was leached either from the Late Ordovician to Lower Carboniferous carbonate rocks of the area, or from contemporaneous sulfide deposits formed in these rocks. The galena deposits are composed of upper crustal lead deposited along fault zones in the limestones of the Permian Bickici Formation and in small cracks developed in the lower part of these limestones along the overthrust zone between the Triassic Camlica and Permian Bickici Formations. (c) 2006 Elsevier Ltd. All rights reserved.