S. Parham; M. R. Kamali; F. Fayazi
Abstract
The Dalan Formation (Upper Permian) is mainly composed of limestone and dolostone with minor evaporite interbeds. Upper carbonates of the Dalan Formation constitute one of the main gas reservoirs in the Zagros fold thrust belt especially in the Fars and the Persian Gulf. The upper part of the Dalan Formation ...
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The Dalan Formation (Upper Permian) is mainly composed of limestone and dolostone with minor evaporite interbeds. Upper carbonates of the Dalan Formation constitute one of the main gas reservoirs in the Zagros fold thrust belt especially in the Fars and the Persian Gulf. The upper part of the Dalan Formation consists of oolitic grainstone with high reservoir quality. Based on sedimentological studies in the upper Dalan unit, seven microfacies have been recognized. This microfacies have been deposited in warm, arid intertidal, lagoon and shoal. They deposited in a homoclinal ramp. Different diagenetic process affected this unit are bioturbation, micritization, neomorphism, replacement, dolomitization, anhydritization, mechanical and chemical compaction, cementation, dissolution and fracturing. Based on the evidence like widespread dissolution, formation of moldic and vuggy porosity and precipitation of different types of meteoric cements and based on paragenetic sequences, it can be concluded that the studied interval, have not buried after the deposition, but at least some parts like oolitic shoal exposed subearially and was affected by meteoric diagenesis that was followed by deep burial diagenetic environment.
B. Mehri; E. Rastad; F. Fayyazi
Abstract
The Khanjar Pb– Ag (Zn) deposit is one of the stratabound deposits of Cretaceous age in Central Iran. The ore bodies may be grouped into two main geometric types: 1) Lenses of ore bodies congruent with bedding, 2) Ores as open space filling or with brecciate fabric due to faulting. Both types occur ...
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The Khanjar Pb– Ag (Zn) deposit is one of the stratabound deposits of Cretaceous age in Central Iran. The ore bodies may be grouped into two main geometric types: 1) Lenses of ore bodies congruent with bedding, 2) Ores as open space filling or with brecciate fabric due to faulting. Both types occur in limestone unit (k2b).Three ore bearing facies have been distinguished in the Khanjar area: 1) Siliceous limestone facies; galena, sphalerite and pyrite are the main ore minerals. Minor amounts of chalcopyrite are also visible. 2) Mullusca, Echinoderm wackstone facies with galena and sphalerite. 3) Rudist limestone facies with large amount of galena. As with other stratabound and stratiform Pb- Zn deposits, the main ore minerals are simple and few in number. In addition, galena, sphalerite and pyrite, some tetrahedrite, barite and minor amounts of copper minerals are observed. Pyrite often with framboidal texture and sphalerite with spheroidal texture form always part of paragenesis. Fluid inclusion investigations on saddle dolomite located in fractures with galena and sphalerite demonstrated the homogenization temperature of 145-230 centigrade and salinity of 17.5-23% NaCl equivalent.Geometry of ore bodies, occurrence of ore horizons in certain sedimentary facies, ore textures and structures, depositional environment (Lagoonal), paragenetic sequence of minerals and fluid inclusion data, all suggest that Khanjar Pb- Ag(Zn) deposit is an MVT deposit.
