جستجوی مقالات مرتبط با کلیدواژه "آنالیز عنصری" در نشریات گروه "زمین شناسی"

The Dariyan Formation with the Aptian age is the youngest reservoir formation of the Upper Khami group which is important in terms of hydrocarbon reservoir potential. This formation is 135 meters thick in the Kuh-e-Mish surface section and consists of thin, thick and massive limestone, marl and shale. Petrographic studies led to the identification of 13 microfacies. These have been deposited in four types of depositional environments, including inner ramp, mid ramp, outer ramp and basin, in a ramp type carbonate platform. Based on petrography, lateral and vertical facies changes, 3 third-order cycles distinguished. An integrated multidisciplinary approach including, petrography, surface gamma-ray spectrometry and trace element analysis have been used for recognition of original carbonate mineralogy and stratigraphic interpretations of this succession. Geochemistry of minor and major elements reveal original aragonitic mineralogy of the Dariyan Formation. Bivariate plot of Mn versus Sr/Ca values illustrated that the Aptian carbonates were affected by semi close diagenetic system with moderate water/rock interaction. Trace elements (Fe and Mn) contents are compared with distribution of sedimentary facies and depositional sequences to investigate and correlate stratigraphic boundaries, which are determined by sequence stratigraphy in shallow marine carbonate platform of the Dariyan Formation. The elemental peaks coinciding with the sequence boundaries and elemental peaks are correlated with maximum flooding surfaces.

Shahbazan Formation with Eocene age is widely developed in Lorestan basin. In the study section, this formation with a thickness of 62 meters is located on the Kashkan Formation and is discontinuously below the Asmari Formation. The lithology of Shahbazan Formation in the study area includes dolomitic carbonate rocks. In order to study micro-facies, 60 samples of this section were collected and 20 samples were selected for elemental analysis. Based on field observations, lithographic and geochemical evidences based on elemental analysis by (EPMA) and (EDS) methods, two groups of dolomite were identified. Primary dolomites include dolomicrites in size between 4 to 10 microns that represent the formation of a tidal zone environment. Secondary dolomites include dolomicrosparite in size between 10 to 20 microns, dolosparites larger than 50 microns that is formed in a shallow to medium burial diagenesis environment due to the seepage of evaporated basin floor brines in to the carbonate platform on Shahbazan Formation in the study area. Low values of Fe versus high values of Sr and Na in dolomicrites, and high concentration of Fe in dolomicrosparite and dolosparite with some evidence such as intraclast, fenestral prosity and lack of evaporative minerals, indicate that these dolomites have been formed from the tidal model, seepage and then shallow to moderate burial. Geochemical evidence showed that the studied dolomites are non- stoichiometric, which can be explained the age of Shahbazan Formation.

The study area is located 60 km southeast of Abadeh city in the northeastem part of Mountain Hambast .In the concerned area there exists complete outcrops from the Middle to the Upper Permian , and has two stratigraphic sections in the Hambast valley as was based on field evidence , petrography and geochemical analysis based on elemental analysis of (EDS) and (EPMA) methods. Two main groups of dolomite minerals including primary dolomite and secondary dolomite were identified .The Primary dolomitic group (called dolomicrites) show mosaic texture and are more anhedral , The second group (dolomicrosparites ) are subhedral. The dolosparites are often subhedral and uhedral.In dolomicrites , Mg is lower than other dolomites due to the highe Ca content.In general , the amount of Sr in the dolomites studied decreases from dolomicrites to dolosparite and increased Sr in dolomicrites is due to the function of diagenesis processes on aragonite shrlls.

The study area is located in Central Iran zone in the Gharavol Mountain (10 Km from north of Bajestan). Jamal Formation in studied section is 349m thick and composed of limestone and dolomite. This formation overlies disconformably the Sardar Formation. Based on petrographical studies, 5 types of dolomites were identified including: fine crystal dolomite (Xenotopic A), fine to medium crystal dolomite (Idiotopic P), euhedral medium crystal dolomite (Idiotopic E), medium and coarse crystal dolomite (Idiotopic S) and idiotopic C. In these dolomites, Sr content varies between 40 to 160 ppm and Na is between 13990 to 40580 ppm. These values are more than values expected for dolomites formed in marine environments. Fe content varies between 1020 to 3770 ppm and Mn is about 140 to 580 ppm. Based on petrographic and elemental analysis, these dolomites formed during early diagenesis (marine water) and shallow to medium burial depth. Origin of Mg2+ for type 1 dolomites was marine water, whereas for others were from pore water, shale diagenesis associated with limestones or probably shales of Sardar Formation.