Thermobarometry and mineral chemistry of Central Iran Permo-Triassic lamprophyres in Chahrisseh Region, northeast Isfahan

Chahrisseh magmatic rocks are located in the northeast Isfahan, in the Sanandaj-Sirjan structural zone and parallel to the Qom-Zefre fault. These magmatic masses are located in a continuous section of Permian-Triassic sediments and rarely enter the Early Triassic beds. These rocks contain anhydrous ferromagnesium minerals (olivine, clinopyroxene and plagioclase), hydrous ferromagnesium minerals (amphibole and biotite) in addition to secondary minerals (chlorite, epidote and actinolite). Based on petrographic studies and geochemical analysis of minerals, these magmatic rocks are among the ultramafic lamprophyres with alkaline nature. Different methods of temperature-barometry of minerals show two completely different ranges of pressure and temperature (the first range of temperature 1000 to 1100 ° C and pressure 16 to 20 kbar and the second range of temperature 900 to 1000 ° C and pressure 6 to 13 kbar) which corresponds to the porphyric texture of the rocks. The chemical properties of primary minerals indicate the formation and placement of alkaline lamprophyres in the intercontinental environment. On the other hand, the presence of crustal xenoliths and xenocrysts provides evidence of the effect of crustal contamination. Therefore, it seems that in the short period of time from the end of the Paleozoic to the beginning of the Mesozoic, following the operation of the technical phase of Hercinian, alkaline lamprophyres form in a continental environment and digested parts of the continental crust during ascending to the earthchr('39')s surface.