نویسندگان
گروه زمین شناسی
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
The studied area is located in the north of Lorestan and 25 km north of Khorram Abad city. In this area, the Shahbazan Formation with the dominant lithology of limestone and dolomite is 85 meters thick, its lower boundary is a slope on the Kashkan detrial formation and its upper boundary is continuous with the carbonates of the Asmari formation. The facade is covered. Based on petrographic and geochemical studies, two groups of dolomites were identified. Primary dolomites (delomicrites) with a mosaic and often amorphous texture in sizes less than 10 microns and secondary dolomites (dolomicrosparites and doloasparites) with a semi-shaped to shaped texture They were observed in sizes larger than 10 microns and even larger than 250 microns.In the studied dolomites, there is an increasing trend of Fe and Mn elements and a decreasing trend of Sr element from dolomicrites towards dolomicrosparites and dolosparites. The presence of some evidence such as bird's eye porosity, algal laminae and intraclasts and the absence of evaporite minerals in the studied samples showed that the primary dolomites were formed in a tidal model and then As a result of seepage of basin floor sediments in the carbonate platform of Shahbazan Formation, secondary dolomites have expanded in a shallow to medium burial diagenesis model.The relatively high concentration of Na in the studied dolomites (0.1 to 1.4% by weight) indicates the influence of basin floor sediments on them. The ratio of Ca/Mg in all the studied dolomites is higher than the standard limit (1.6) and indicates that they are non-stoichiometric. This issue can be justified considering the age of Shahbazan formation in this part of Lorestan sedimentary basin.
کلیدواژهها [English]
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