Relationship between the Sr and O isotope compositions of hydrothermal fluids and the spreading and magma-supply rates at oceanic spreading centers
Relationship between the Sr and O isotope compositions of hydrothermal fluids and the spreading and magma-supply rates at oceanic spreading centers
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DOI：
10.1130/0091-7613(1999)027
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发表时间：
1999-12-01
期刊：
影响因子：
5.8
通讯作者：
Humphris, SE
中科院分区：
文献类型：
--
作者：
Bach, W;Humphris, SE
我们发现，在海洋扩张中心的热液流体的Sr和O同位素组成和扩张速率之间的一阶相关性。慢扩张海脊热液流体的同位素特征比快扩张海脊更以岩石为主，这意味着它们与地壳进行了更大程度的Sr和O交换。单个热液点内Sr和O同位素特征的局部时空变化可归因于热液系统响应岩浆或构造事件的短期变化，在深度处发生相分离，并在上升流区与海水混合。然而，这些过程不能解释热液流体中岩石特征的增加与扩张速率的降低之间的系统性全球关系。岩石和循环流体之间更大程度的Sr和O交换可以通过以下方式实现：（1）通过海洋岩石圈的更长的流体流动路径，（2）更多的破碎岩石暴露出更大的反应区域，（3）由于较慢的热液循环而增加的流体停留时间，或（4）所有三者的组合。我们倾向的解释是，在缓慢扩张的洋脊，流体流动路径更长，渗透深度可能更大。
We find a first-order correlation between the Sr and O isotope compositions of hydrothermal fluids and spreading rate at oceanic spreading centers. The isotope signatures of hydrothermal fluids at slow-spreading ridges are more rock dominated than those at fast-spreading ridges, implying that they have undergone a greater extent of Sr and O exchange with the crust, The local spatial and temporal variability in Sr and O isotope signatures within individual hydrothermal sites can be attributed to short-term variations in the hydrothermal system in response to magmatic or tectonic events, phase separation at depth, and mixing with seawater in the upwelling zone. However, these processes cannot explain the systematic global relationship of an increasing rock signature in hydrothermal fluids with decreasing spreading rate. A greater extent of Sr and O exchange between rocks and the circulating fluids can be achieved by (1) a longer fluid-flow pathway through the oceanic lithosphere, (2) more fractured rock that exposes a greater reaction area, (3) an increased residence time of the fluid due to slower hydrothermal circulation, or (4) a combination of all three. Our preferred interpretation is that fluid-flow paths are longer, and depths of penetration are likely greater, at slow-spreading ridges.