The geochemical and isotopic (Li, B, Sr, O, C) compositions of veins from altered oceanic lithosphere at Atlantis Massif: Implications for interactions with seawater

大洋岩石圈变化过程中的海底水-岩相互作用记录了不同阶段的碳酸盐岩脉和硬石膏脉。我们建议对产于由辉长岩和来自缓慢扩张的大洋中脊的蛇纹化橄榄岩组成的上地幔部分中的碳酸盐和硬石膏矿脉进行全面的地球化学研究(ODPIODP腿153,209,304/305)。蚀变镁铁质和超镁铁质岩性现在被认为是丰富的海底岩石。因此，了解在这些环境下海底以下变化过程中岩石圈和海水之间的化学交换是评估地球化学循环的一个重要问题。利用微量元素丰度和同位素组成(Li、B、C、O、Sr)研究大洋核杂岩岩石圈地幔折返和抬升过程中基底海水循环的演化。将这些数据与对矿脉形成温度和年龄的估计相结合，将允许重建反应路径和速率。这些数据是审查大洋岩石圈和海洋之间交换预算所必需的。此外，关于脉体形成的温度和年龄信息将有助于揭示岩石圈沿缓慢扩张脊的后期增生和抬升的动力学。来自ODP209段碳酸盐脉的数据表明，如何结合微量元素丰度、锂、氧、锶同位素组成和放射性年龄测定来破译大洋岩石圈折返的晚期历史以及与海水的相互作用。

Subseafloor water-rock interactions during the alteration of oceanic lithosphere are recorded by different stages of carbonate and anhydrite veining. We propose to carry out a comprehensive geochemical study of carbonate and anhydrite veins hosted in upper mantle sections comprised of gabbroic rocks and serpentinized peridotite from slow spreading Mid-ocean Ridges (ODP/IODP Legs 153, 209, 304/305). Altered mafic and ultramafic lithologies are now recognized as abundant seafloor rocks. Hence, the understanding of chemical exchange between lithosphere and seawater during sub-seafloor alteration in these settings is an important issue in assessing geochemical cycles. Trace element abundances and isotope (Li, B, C, O, Sr) compositions will be used to gain insights in the evolution of seawater circulation in basement during exhumation and uplift of lithospheric mantle in oceanic core complexes. Coupling these data with estimates of formation temperatures and ages of veins will allow the reconstruction of reaction pathways and rates. Such data are required for examinations of exchange budgets between oceanic lithosphere and the oceans. In addition, temperature and age information on vein formation will help unravel the dynamics of late-stage accretion and uplift of lithosphere along slow spreading ridges. Data from carbonate veins of ODP Leg 209 demonstrate how trace element abundances, Li, O, Sr isotope compositions, and radiometric age determinations can be combined to decipher the late-stage history of oceanic lithosphere exhumation and interactions with seawater.