The eastern Southwest Indian Ridge, between 61° and 67°E, has a very low melt supply and comprises several corridors of nearly amagmatic spreading that expose mantle-derived serpentinized peridotite. More volcanically active ridge portions separate these corridors. He, Ne, Pb, Nd, Hf and Sr isotopes were analyzed in basalt glasses dredged on two types of seafloor: volcanic and ultramafic. Basalts dredged in ultramafic seafloor on-axis tend to be slightly more depleted for heavy radiogenic isotopes and show slightly higher 3He/4He isotope ratios than basalts dredged in volcanic seafloor, with no systematic difference in neon isotope ratios. We propose that both types of basalts are derived from the same mantle source, but that the basalts dredged on ultramafic seafloor are more affected by melt/mantle reactions, which slightly modify their isotopic signatures. Our dataset also includes a few basalts, dredged on off-axis ultramafic seafloor, that range in age between 2.6 and 8.8 Ma. These few and widely-spaced off-axis samples, erupted at the ridge axis, are a rare opportunity to capture the potential geochemical variability of the mantle source in an ultramafic seafloor corridor over 8.8 Ma. This temporal variability appears to be minor compared to the overall range of isotopic variability of the on-axis lavas from the 61°-67°E region

中文翻译：

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印度地幔中超过 8.8 Ma 的同位素（He、Ne、Sr、Nd、Hf、Pb）特征

西南印度洋脊东部位于东经 61° 至 67°E 之间，熔体供应量非常低，包括几条近乎岩浆扩张的走廊，暴露出地幔衍生的蛇纹石化橄榄岩。火山活动较多的山脊部分将这些走廊分隔开来。He、Ne、Pb、Nd、Hf 和 Sr 同位素在两种类型的海底：火山和超镁铁质上挖出的玄武岩玻璃中进行了分析。在超基性海底挖出的玄武岩在重放射成因同位素方面往往略多耗尽，并且显示出比在火山海底挖出的玄武岩略高的 3He/4He 同位素比，氖同位素比没有系统差异。我们提出两种类型的玄武岩都来自同一地幔源，但在超基性海底疏浚的玄武岩更受熔体/地幔反应的影响，稍微修改了它们的同位素特征。我们的数据集还包括一些在离轴超镁铁质海底挖掘的玄武岩，年龄范围在 2.6 到 8.8 Ma 之间。这些在脊轴上喷发的少数且间隔很宽的离轴样本是一个难得的机会，可以捕获超过 8.8 Ma 的超基性海底走廊中地幔源的潜在地球化学变化。与来自 61°-67°E 区域的轴上熔岩同位素变化的整体范围相比，这种时间变化似乎很小 这是一个难得的机会，可以捕捉超过 8.8 Ma 的超基性海底走廊中地幔源的潜在地球化学变化。与来自 61°-67°E 区域的轴上熔岩同位素变化的整体范围相比，这种时间变化似乎很小 这是一个难得的机会，可以捕捉超过 8.8 Ma 的超基性海底走廊中地幔源的潜在地球化学变化。与来自 61°-67°E 区域的轴上熔岩同位素变化的整体范围相比，这种时间变化似乎很小