Late Permian lamprophyric magmatism in North-East of Isfahan Province, Iran: A mark of rifting in the Gondwanaland

Abstract

Lamprophyric stocks and pillow lavas are situated in Pal-e-Havand area (South-East of Anarak, North-East of Isfahan Province, Iran) along the Turkmeni–Ordib fault. The predominant minerals of these rocks are amphibole (kaersutite), plagioclase (albite), K-feldspar (sanidine), Cr–Ti spinel, ilmenite, and apatite, with minor amounts of magnetite, chlorite, pumpellyite, epidote, sphene, leucoxene and calcite. Textures are porphyritic, microlitic and variolitic, with calcite amygdals. Combined petrological and geochemical studies classify these rocks as alkaline lamprophyre, in general, and camptonites in particular. The rocks studied are enriched in alkalis, TiO 2 and LREE, with SiO 2 content between 40 to 52 weight percent (wt.%). Similar geochemical characteristics of pillow lavas and stocks and parallel chondrite REE patterns of all samples reveal that they were all derived from a similar mantle source region and underwent similar melt extraction. These rocks are intracontinental alkaline lamprophyres, produced by low degree of partial melting of upper mantle garnet lherzolites. The Paleo-Tethys subduction from Lower Paleozoic is the cause of mantle enrichment in volatiles and lamprophyric magmatism in Upper Paleozoic along the Turkmeni–Ordib fault.