Geochemistry and petrology of ODP Leg 121 basalts@en

Basement lavas from Sites 756, 757, and 758 on Ninetyeast Ridge are tholeiitic basalts. Lavas from Sites 756 and 757 appear to be subaerial eruptives, but the lowermost flows from Hole 758A are pillow lavas. In contrast to the compositional variation during the waning stages of Hawaiian volcanism, no alkalic lavas have been recovered from Ninetyeast Ridge and highly evolved lavas were recovered from only one of seven drill sites (DSDP Site 214). All lavas from Site 758 have relatively high MgO contents (8-10 wt%), and they are less evolved than lavas from Sites 756 and 757. […]九十度海岭（Ninetyeast Ridge）756、757和758站位的基底熔岩均为拉斑玄武岩（tholeiitic basalts）。756和757站位的熔岩看似为陆上喷发岩，而758A钻孔的最底部岩流则为枕状熔岩（pillow lavas）。与夏威夷火山活动衰退阶段的成分变化特征不同，九十度海岭未采获碱性熔岩，且7个钻探站位（深海钻探计划DSDP 214站位）中仅1个站位采获了高度分异熔岩。758站位的所有熔岩均具有相对较高的MgO含量（8~10 wt%），且其分异程度低于756和757站位的熔岩。[…]