Geochemical Variability Along the Northern East Pacific Rise: Coincident Source Composition and Ridge Segmentation
Geochemical Variability Along the Northern East Pacific Rise: Coincident Source Composition and Ridge Segmentation
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DOI：
10.1029/2019gc008287
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发表时间：
2019-04
期刊：
影响因子：
3.7
通讯作者：
S. Mallick;V. Salters;C. Langmuir
中科院分区：
文献类型：
--
作者：
S. Mallick;V. Salters;C. Langmuir
东太平洋海隆5.5°N至19°N的100多个洋中脊玄武岩的新微量元素丰度和同位素组成显示，同位素组成沿着与脊不连续性一致的脊轴呈阶梯函数变化。转换断层，重叠的扩展中心，和devals（偏离轴向线性）标志着不同的同位素组成和微量元素比，表明源的变化个别集群的分离。这种相关的化学聚类和形态分割表明，即使在精细尺度上，源成分和分割也可以密切相关。段内的实质性化学变化与源成分有关。这表明，即使在岩段内，岩浆的运移也主要是垂直的，只有有限的沿着-脊运移，而且几乎没有证据表明岩浆房沿走向沿着混合良好。微量元素浓度与同位素组成在分段尺度上有较好的相关性，但在区域尺度上相关性较差。沿东太平洋海隆北方的微量元素和同位素变化沿着可以解释为三个地幔成分：亏损橄榄岩端元，富集橄榄岩端元，和回收辉长岩样成分。辉长岩成分具有同位素特征，表明其来源古老。高分辨率采样表明，在一个段内，化学变异性主要是二元的，但二元混合的端元从段到段发生变化。段内的二元变异的端元是三个端元的组合。
New trace element abundances and isotope compositions for more than 100 mid‐ocean ridge basalts from 5.5°N to 19°N on the East Pacific Rise show step function variations in isotopic composition along the ridge axis that coincide with ridge discontinuities. Transform faults, overlapping spreading centers, and devals (deviation from axial linearity) mark the separation of individual clusters of distinct isotopic composition and trace element ratios that indicate source variations. This correlated chemical clustering and morphological segmentation indicates that source composition and segmentation can be closely related even on a fine scale. Substantial chemical variations within a segment are related to source composition. This suggests that even within segments the magma transport is mainly vertical, and there is limited along‐ridge transport, and there is little evidence for magma chambers that are well mixed along strike. Trace element concentrations show good correlations with isotopic compositions on a segment scale but less so on a regional scale. The trace element and isotopic variability along the northern East Pacific Rise can be explained by three mantle components: a depleted peridotite endmember, an enriched peridotite endmember, and a recycled gabbro‐like component. The gabbroic component has an isotopic signature indicating an ancient origin. The high‐resolution sampling indicates that within a segment the chemical variability is largely binary but that the endmembers of the binary mixing change from segment to segment. The endmembers of the binary variation within a segment are a combination of three of the endmembers.