Abstract: (28 Views)
Miocene-aged carbonate sequence in Geshur village section which located in one kilometer to southwest of Harsin, Kermanshah province, is composed of glauconite limestone, glauconite marl, and interlayers of shale. Glauconite mineral is present in all rock facies of this sequence. The abundance of glauconite ranges from 5 to 45% and according to the degree of maturity, they have been observed from slightly evolved with pale green color to highly evolved with very rich green color in thin sections. Featured such as unselected replacement, the presence of highly evolved glauconite pellets, scattered pieces of glauconite in the form of green halo in matrix, weak sorting with phosphate and wrinkled glauconites are some of the most important evidences in the deposition of autochthonous glauconite under the suitable physico-chemical conditions which rqeplacement with carbonate matrix and fossil shells. In the studied samples, the SEM results of glauconite minerals is compatible with the results of petrographic studies. Moreover, the semi-quantitative analysis on glauconite minerals using EDS SEM on FeO and K2O concentrations indicate a positive linear relationship between the FeO and K2O concentrations. The concentrations of most samples are lower than the values of the threshold (K2O < 8%) (Fe2O3 < 7%), which is consistent with the petrographic evidence for autochthonous glauconites.
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