Timing of carbonate precipitation in basalts from the Louisville seamount trail: evidence for prolonged interaction between seawater and basement

厚堆积的沉积物通常阻止海水流入古老的洋壳，从而抑制海水与火山基底之间的相互作用。然而，成千上万的火山海山和海洋岛屿冲破了这些沉积物。海山顶部的沉积物覆盖层通常相当薄，这可能使热液流体流过海山以及相关的海水-海山反应在海山形成后的很长一段时间内继续进行。因此，这可能有助于海洋基底与海洋之间的化学和热交换，并有助于调节海水化学，而这两者都被发现受到洋中脊或其附近热液流体通量的强烈控制。然而，迄今为止，海水-海山的相互作用很少得到关注，仍然没有得到很好的理解，我们在这里提出了一个简单的研究，以测试是否海山真的与海水在很长一段时间内相互作用，或者如果相互作用停止后不久，他们的安置。我们建议对西南太平洋路易斯维尔海山小径的四个玄武岩海山内沉淀的碳酸盐物质进行年龄测定。这些海山形成于约50至74 Ma前，并在国际海洋发现计划第330次考察期间进行钻探。我们拥有的59个样品是方解石或文石脉或囊状填充沉淀物。在此之前，已经收集了常量和微量元素以及C，O和Sr同位素数据。这些数据表明，渗透海水和路易斯维尔玄武岩之间存在不同程度的相互作用，形成了低温（<30°C）碳酸盐。原位U-Pb年龄测定是一种可靠的技术，它将为两种可能性中的任何一种提供证据，即，此外，以前曾估计，每年通过海山和海洋岛屿循环的水量与通过大洋中脊玄武岩循环的水量相似。除了提供洞察到海水海山相互作用的寿命，碳酸盐年龄，日期将允许建立第一次估计的作用海山作为全球CO2 sinks.In总结，我们建议调查的持续时间内的潜在重大海水岩石相互作用海洋海山以及其对长期碳循环的直接影响。拟议的工作提供了一个直接的方式来确定这种相互作用的重要性和规模。

Thick piles of sediments usually prevent seawater inflow into old oceanic crust and thus inhibit interactions between seawater and the volcanic basement. Thousands of volcanic seamounts and ocean islands, however, break through such piles of sediments. The sedimentary covers atop seamounts commonly are rather thin, which potentially allows hydrothermal fluid fluxes through seamounts and related seawater–seamount reactions to proceed for long periods of time after seamount formation. This may hence contribute to the chemical and heat exchange between oceanic basement and oceans and to regulating seawater chemistry, both of which have been found to be strongly controlled by hydrothermal fluid fluxes at or near mid-ocean ridges. However, seawater–seamount interactions have to date gained little attention and remain not well understood.We here propose a straightforward study to test if seamounts really interact with seawater over long periods of time or if the interaction ceases soon after their emplacement. We suggest to age-date carbonate materials that precipitated within four basaltic seamounts of the Louisville seamount trail, SW Pacific. The seamounts were emplaced between ~50 and 74 Ma ago and were drilled during International Ocean Discovery Program Expedition 330. We are in the possession of 59 samples that are calcitic or aragonitic vein or vesicle fill precipitates. Prior to this proposal, major and trace element as well as C, O, and Sr isotopic data have already been collected. The data indicate low-temperature (<30°C) carbonate formation with varying degrees of interaction between infiltrating seawater and the Louisville basalts. In situ U–Pb age-dating is a robust technique that will provide evidence for either of the two possibilities, i.e., if carbonates formed in narrow or wide time ranges after seamount emplacement.Further, it has previously been estimated that the yearly volume of water circulating through seamounts and ocean islands is similar to that circulating through basalts at mid-ocean ridges. Aside from providing insights into the longevity of seawater–seamount interactions, the carbonate age-dates will allow setting up first estimates on the role of seamounts as global CO2 sinks.In summary, we propose to investigate the duration of potentially significant seawater–rock interactions within oceanic seamounts as well as its direct implications on the long-term carbon cycle. The proposed work provides a direct way to identify the importance and magnitude of such interactions.