From the subtropics to the central equatorial Pacific Ocean: Neodymium isotopic composition and rare earth element concentration variations
From the subtropics to the central equatorial Pacific Ocean: Neodymium isotopic composition and rare earth element concentration variations
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DOI：
10.1029/2012jc008239
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发表时间：
2013-02-01
影响因子：
3.6
通讯作者：
Cravatte, Sophie
中科院分区：
文献类型：
--
作者：
Grenier, Melanie;Jeandel, Catherine;Cravatte, Sophie
测定了南热带太平洋表层至深水（112个样品）过滤后的钕同位素组成（Nd）和稀土元素（REE）浓度。这些示踪剂分布的相对详细的图片使我们能够改进海洋ε (Nd)变化发生的区域。如前所述，从萨摩亚流向所罗门海和巴布亚新几内亚（PNG）地区的大部分水团的epsilon（Nd）值增加。此外，来自赤道东太平洋（200-550米深）的水团也显示了放射性成因值，可能是在南美海岸和加拉帕戈斯群岛附近获得的。这些（Nd）的变化影响整个水柱。最可能导致这种变化的过程是位于该地区的众多放射性斜坡/边缘与流过的海水之间的“边界交换”。大气沉积的溶解和/或火山灰的扩散流也被认为可以解释在PNG地区地表观测到的放射性成因ε (Nd)。有趣的是，在研究的大部分水团中，正铕（Eu）异常表征了标准化的稀土模式。这一异常与沉积物和岩石样品的REE模式一致，这些样品是当地水的潜在来源。这种一致性强化了一个假设，即由于“边界交换”，岩石成因在海洋REE收支中起着主要作用。这里提供的数据集是进一步采样的良好基础，这些采样将在正在进行的GEOTRACES程序（www.geotraces.org）框架中实现。引用本文：Grenier， M.， C. Jeandel， F. Lacan， D. Vance， C. Venchiarutti， A. cross和S. Cravatte(2013)，从亚热带到赤道太平洋中部：钕同位素组成和稀土元素浓度变化，J. Geophys。海洋学报，18,592-618,doi:10.1029/2012JC008239。
Neodymium isotopic compositions (epsilon(Nd)) and rare earth element (REE) concentrations were measured for filtered surface to deep waters (112 samples) in the Southern Tropical Pacific. The relatively detailed picture of these tracer distributions allowed us to refine the areas where oceanic epsilon(Nd) variations occur. epsilon(Nd) values increase for most of the water masses flowing from Samoa to the Solomon Sea and in the Papua New Guinea (PNG) area, as already observed. Furthermore, water masses arriving from the eastern equatorial Pacific (200-550m depth) also revealed radiogenic values, possibly acquired in the vicinity of the South American coasts and Galapagos Islands. These epsilon(Nd) variations affect the whole water column. The most likely process causing such variations is "boundary exchange" between the numerous radiogenic slopes/margins located in this area and seawater flowing past. Dissolution of atmospheric deposition and/or diffuse streaming of volcanic ash are also suggested to explain the radiogenic epsilon(Nd) observed at the surface in the PNG area. Interestingly, a positive europium (Eu) anomaly characterizes the normalized REE patterns of most of the studied water masses. This anomaly is consistent with the REE patterns of sediment and rock samples that are potential sources for the local waters. Such consistency reinforces the hypothesis that lithogenic sources play a major role in the oceanic REE budget, thanks to "boundary exchange." The data set presented here is a good basis for further sampling that will be realized in the framework of the ongoing GEOTRACES program (www.geotraces.org). Citation: Grenier, M., C. Jeandel, F. Lacan, D. Vance, C. Venchiarutti, A. Cros, and S. Cravatte (2013), From the subtropics to the central equatorial Pacific Ocean: Neodymium isotopic composition and rare earth element concentration variations, J. Geophys. Res. Oceans, 118, 592-618, doi:10.1029/2012JC008239.