, ▁ne od ym ium , ▁lead , ▁ha f ni um , ▁and ▁os m ium ▁in ▁bas al ts ▁have ▁been ▁much ▁studied ▁to ▁learn ▁about ▁the ▁evolution ▁of ▁the ▁Earth ' s ▁mant le . ▁Is ot op ic ▁r ati os ▁of ▁noble ▁g ases , ▁such ▁as ▁ 3 He / 4 He , ▁are ▁also ▁of ▁great ▁value : ▁for ▁instance , ▁r ati os ▁for ▁bas al ts ▁range ▁from ▁ 6 ▁to ▁ 1 0 ▁for ▁mid - o cean ▁r idge ▁th ole i it ic ▁bas alt ▁( normal ized ▁to ▁atmos pher ic ▁values ), ▁but ▁to ▁ 1 5 – 2 4 ▁and ▁more ▁for ▁ocean - is land ▁bas al ts ▁thought ▁to ▁be ▁derived ▁from ▁mant le ▁pl umes . ▁ ▁Source ▁rocks ▁for ▁the ▁partial ▁mel ts ▁probably ▁include ▁both ▁per id ot ite ▁and ▁py ro x en ite ▁( e . g ., ▁Sob ole v ▁et ▁al ., ▁ 2 0 0 7 ). ▁ ▁Mor ph ology ▁and ▁text ures ▁▁ ▁The ▁shape , ▁structure ▁and ▁texture ▁of ▁a ▁bas alt ▁is ▁di agnostic ▁of ▁how ▁and ▁where ▁it ▁er upt ed — wh ether ▁into ▁the ▁sea , ▁in ▁an ▁explos ive ▁c inder ▁er u ption ▁or ▁as ▁cre eping ▁p ā ho e ho e ▁la va ▁flows , ▁the ▁classic ▁image ▁of ▁Hawai ian ▁bas alt ▁er u ptions . ▁ ▁Sub a er ial ▁er u ptions ▁▁ ▁Bas