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对东太平洋海隆(EPRⅠ区和Ⅱ区)和南大西洋中脊(SMAR)6个站位新鲜的玄武岩样品进行了岩石学及地球化学研究。结果显示,EPR玄武岩样品可分为辉石玄武岩、气孔玄武岩和玻基玄武岩3种类型,SMAR玄武岩样品主要为辉石玄武岩。EPR和SMAR玄武岩样品的标准矿物组合相同,均出现了石英和紫苏辉石标准矿物,为典型的拉斑玄武岩。EPRⅠ区和SMAR玄武岩表现出轻稀土富集的配分模式,可能受到了富集地幔源区(EMORB)的影响,其玄武岩可能形成于未经历早期熔融事件的富集地幔或部分熔融程度相对较低。EPRⅡ区玄武岩为正常型洋中脊玄武岩(N-MORB),其源区为经历了早期熔融事件的、亏损洋中脊地幔源区(DMM),且源岩部分熔融程度较高。EPRⅠ区与Ⅱ区不同的幔源特征说明东太平洋海隆地幔源区存在不均一性。
Petrology and geochemistry of fresh basalt samples from six stations in the eastern Pacific Seale (EPRⅠ and Ⅱ) and the Southern Atlantic Ridge (SMAR) were studied. The results show that the samples of EPR basalt can be divided into three types: pyroxene basalt, stomatal basalt and glass basalt. The SMAR basalt samples are pyroxene basalts. The standard mineral assemblages for the EPR and SMAR basalt samples are the same and both quartz and peridotite standard minerals appear and are typical tholeiite basalts. The EPRⅠ and SMAR basalts show a pattern of light rare earth enrichment, which may be affected by the enrichment of mantle source (EMORB). The basalts may form in the enriched mantle without previous melting events or have a relatively low degree of partial melting . The basalts in the EPRⅡare normal-type mid-oceanic ridge basalts (N-MORB). Their source regions are DMMs that experienced early melting events and have a high degree of partial melting. The different mantle-source characteristics of EPRⅠand Ⅱ indicate the heterogeneity of the mantle source area in the eastern Pacific Ocean.