The Ab-Bagh Late Jurassic-Early Cretaceous sediment-hosted Zn-Pb deposit, Sanandaj-Sirjan zone of Iran: ore geology, fluid inclusions and (S–Sr) isotopes

摘要: Abstract The Ab-Bagh clastic- and carbonate-hosted stratabound stratiform Zn-Pb deposit in the Sanandaj-Sirjan zone, southeastern corner of Malayer-Esfahan metallogenic belt Iran, is typical several sedimentary–exhalative (SEDEX) deposits this belt. hosted a late Jurassic-early Cretaceous sedimentary sequence. Based on position, there are two Zn-Pb-bearing stratigraphic ore horizons. Ore horizon 1 by black shale siltstone. wedge-shaped body located close to synsedimentary normal fault. Petrographic studies indicates that mineralization comprises three sulfide facies: stockwork, bedded massive facies. 2 occurs early carbonates massive-replacement facies concordant with host rock layering; it also underlain stockwork Textures include framboidal, laminated, breccia, replacement, vein-veinlet. Hypogene minerals predominantly sphalerite, galena, pyrite chalcopyrite. Calcite quartz major gangue minerals. Silicification carbonatization main wallrock alteration styles; intensity increases towards feeder zone. relationships between rock-forming minerals, formed during stages: fine-grained bands (stage I) intricately interlayered organic matter-rich beds Sulfide exhibit classic textures, such as laminations bedding, indicative origin. Coarser-grained stage II base metal sulfides show breccia vein-veinlet considered have replacement sub-seafloor fluid flow. Fluid inclusion microthermometry was carried out calcite associated Homogenization temperatures range 180–301 °C, average salinity 17.93 wt% NaCl eq. size distribution framboids ore, geochemistry presence matter, collectively suggest anoxic locally suboxic ambient conditions for basin. δ34S composition pyrite, galena ranges from −5.08 +4.51‰. highest values (+2.66 to + 4.51‰) lowest (−5.08 −4.72‰). In facies, sulfur source bacterially reduced seawater sulfate. Whereas thermochemically sulfate sulfur. 87Sr/86Sr ratios indicate origin forming fluids Paleozoic radiogenic basement. Collectively, isotopic, sedimentological, textural, mineralogical, inclusion, geochemical data support vent-proximal SEDEX deposit.