Graham D W, Lupton J E, Spera F J, Christie D M
College of Oceanic & Atmospheric Sciences, Oregon State University, Corvallis 97331, USA.
Nature. 2001 Feb 8;409(6821):701-3. doi: 10.1038/35055529.
Helium isotope variations in igneous rocks are important for relating isotopic heterogeneity to convective mixing in the Earth's mantle. High 3He/4He ratios at many ocean islands, along with lower and relatively uniform values in mid-ocean-ridge basalts (MORBs), are thought to result from a well mixed upper-mantle source for MORB and a distinct deeper-mantle source for ocean island basalts. At finer scales, 3He/4He variations along mid-ocean ridges have been related to underlying mantle heterogeneity, but relationships between the scales of geochemical segmentation and mantle convection remain enigmatic. Here we present helium isotope data for MORB glasses recovered along approximately 5,800 km of the southeast Indian ridge, and develop an approach to quantitatively relate spatial variations in geochemical and geophysical parameters at the Earth's surface. A point-to-point correlation analysis reveals structure in the helium isotope data at length scales of approximately 150 and approximately 400 km that appears to be related to secondary convection in the underlying mantle.
火成岩中的氦同位素变化对于将同位素非均质性与地球地幔中的对流混合联系起来很重要。许多海洋岛屿的³He/⁴He比值较高，而大洋中脊玄武岩（MORB）中的比值较低且相对均匀，这被认为是由于MORB的上地幔源充分混合，以及海洋岛屿玄武岩有独特的更深地幔源。在更精细的尺度上，大洋中脊沿线的³He/⁴He变化与下伏地幔的非均质性有关，但地球化学分段尺度与地幔对流之间的关系仍然不明。在此，我们展示了沿东南印度洋中脊约5800公里采集的MORB玻璃的氦同位素数据，并开发了一种方法来定量关联地球表面地球化学和地球物理参数的空间变化。点对点相关性分析揭示了氦同位素数据中长度尺度约为150公里和约400公里的结构，这似乎与下伏地幔中的二次对流有关。
