Geometry, petrography and composition of Shahmirzad Cretaceous dolomite, Centeral Alborz
|Location||The 24 Symposium of Geosciences|
|Holding Date||19 August 2007|
Different types of dolomitic carbonate rocks of Upper Cretaceous which are located in northeast Shahmirzad, Centeral Alborz host many lead-zinc deposits and occurrences.
In this study 3 profiles of carbonate rocks of obsolete lead-zinc mines from Reza-Abad, Heydar-Abad and Reza-Barak has been selected. Geometry, petrography and composition of dolomites have been studied (by Lumsden equation (1979), N CaCO3 = md + b) using thin microscopic sections stained by Alizarin Red-s and Potassium Ferro Sianor, XRD graphs of dolomite and dolomitic rocks, Wet chemical analysis and XRF. Considering these studies, six types of dolomite textures have been recognized, which according to growth sequence of dolomite crystals in time consist of: Xenotopic A (fine crystal), Idiotopic E, P, Xenotopic A (course crystal) and Saddle dolomite. Dolomites of this region are categorized into 3 groups due to calcium carbonate amount: 49-50%, 51-51.5% and lastly more than 55%. The amount of calcium carbonate in hydrothermal dolomites, which is usually accompanied by minerals is more than 55%. Due to these studies, multistage dolomitization in this region can be related to meteoric water and /or after sedimentation carstification and also hydrothermal activities of Cenozoic period