Timing and magnitude of C02 uptake by ocean crust through seawater interaction and carbonate veining

海洋地壳通过海水相互作用和碳酸盐脉纹吸收二氧化碳的时间和幅度

• 批准号: 49046519
• 负责人: Privatdozent Dr. Andreas Klügel
• 金额: --
• 依托单位: Fachgebiet Petrologie der Ozeankruste
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2010-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/49046519?language=en
• 关键词: Timing; magnitude; C02; uptake; ocean

Fluid flow within the flanks of mid-ocean ridges is now recognized as one of the principal processes that control the budgets of many elements in the oceans and the aging ocean crust on long time scales. This includes CO2 for which carbonate veins in basalt crust impose an important sink, yet little is known about the respective global flux. In over thirty years of ocean drilling, ocean crust of all ages has been sampled to depths that allow an assessment of CO2 uptake in the uppermost crust, but flux estimates exisit only for a few sites. Old crust indicates global oceanic uptake fluxes of 2-4•1012 moles CO2/yr, whereas young crustal sections indicate uptake rates that are an order of magnitude smaller. These observations can only be reconciled if the crust takes up CO2 continuously throughout much of its life time, which is at odds with seismic and heat flow evidence suggesting progressive sealing of permeability and virtual shut down of circulation in crust older than 20-50 Myrs. We propose that this major conundrum in ocean floor research can be resolved by comprehensive and systematic analyses of carbonate veins from crustal sections that cover a range of ages of both slow and fast spread crust. Our approach is fourfold:(1) Logging of core archives to establish carbonate vein crustal inventories, (2) determination of trace element abundances in carbonate veins by laser ablation ICP-MS to determine the maturity of fluids from which the carbonate precipitated, (3) Sr isotope dating by laser ablation MC-ICP-MS analyses of suitable carbonate veins, and (4) determination of geochemical changes in vein halos. The expected results will lead to better estimates of the global CO2 flux between ocean crust and oceans and to a more comprehensive understanding of the timing and processes involved in setting this flux. The data will be merged with isotopic data (Ca, Sr, O, C) to be obtained within the framework of a companion proposal.

大洋中脊两侧的流体流动现在被认为是在很长时间尺度上控制海洋中许多元素和老化的洋壳的主要过程之一。这包括玄武岩地壳中的碳酸盐脉构成一个重要的汇的二氧化碳，但人们对各自的全球通量知之甚少。在三十多年的大洋钻探中，所有年代的洋壳都被取样到可以评估最上层地壳吸收二氧化碳的深度，但通量估计只存在于少数几个地点。古老的地壳表明全球海洋吸收通量为2-4.1012摩尔/年，而年轻的地壳剖面表明吸收速率要小一个数量级。只有当地壳在其生命的大部分时间里不断吸收二氧化碳时，这些观察才能得到证实，这与地震和热流证据表明渗透性的逐渐封闭和地壳中超过20-50年的循环实际上是关闭的是不一致的。我们认为，海底研究中的这一重大难题可以通过全面和系统地分析地壳剖面中的碳酸盐脉来解决，这些剖面涵盖了一系列缓慢和快速扩张地壳的时代。我们的方法包括四个方面：(1)记录岩心档案以建立碳酸盐岩脉壳名录；(2)用激光烧蚀电感耦合等离子体质谱(ICPMS)测定碳酸盐脉中的微量元素丰度，以确定碳酸盐沉积流体的成熟度；(3)用激光烧蚀MC-ICPMS分析合适的碳酸盐脉的锶同位素年龄；(4)测定脉晕中的地球化学变化。预期的结果将有助于更好地估计海洋结壳和海洋之间的全球二氧化碳通量，并更全面地了解确定这一通量所涉及的时间和过程。这些数据将与将在配套提案框架内获得的同位素数据(钙、锶、氧、碳)合并。