Megacrysts are common in alkali basalt of Quaternary age in the northeastern Harrat Shamah basalt fields of Jordan. The dominant phases are Al-clinopyroxene, Al-bronzite, pleonaste spinel and kaersutite amphibole. The megacrysts differ in composition from analogous phases in associated lherzolite xenoliths, but are similar to those in associated Al-augite pyroxenite xenoliths. Major and trace element partioning indicates that most of the megacrysts may have been in equilibrium with their host magmas at high pressure.
ASJC Scopus subject areas
- Earth-Surface Processes