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[HCG35-P06] Chemical composition and classification of frutexites in Alwa Formation, Oman mountains, northern Oman
Keywords:Triassic, limestone, chemical composition, Oman
The predominant feature of the frutexites in the Alwa Formation exhibits 0.1-1.5mm long shrub structure consisting of microlayering by Fe-Mn rich carbonate minerals. Under microscope, two distinct layers showing orange and white colors are recognized and the latter is developed in outer marginal layer of the shrub structure of these carbonate microlayers. In addition, the black color shrubs, which are 0.1-0.5mm long and lack to orange colored layers, are also observed in the black carbonate.
The EDS analysis, using JSM-6510A in Shinshu University, shows the compositional difference of the micro layers of these frutexites. The orange and white colored microlayers of frutexites contain Mg, Fe, Mn as a carbonate component, whereas Al and P concentrates in the black colored microlayers. Thus, the frutexites in the Alwa Formation is classified by two types; Mg-Fe-Mn rich and Al-P rich types. The shrub structure grew as a result of mineralization by microbial activity under fluctuating conditions (Jakubowicz et al., 2014). Thus, this compositional differences and variety of frutexites is possibly related to the microbial activity and bottom water condition during their growth stage.