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

在海洋岩石圈蚀变过程中，海底水岩相互作用通过不同阶段的碳酸盐和硬石膏脉纹来记录。在缓慢扩张的洋中脊（ODP/IODP腿153、209、304/305）中，对由辉长岩和蛇纹橄榄岩组成的上地幔剖面中的碳酸盐和硬硬岩脉进行了全面的地球化学研究。蚀变基性和超基性岩性现在被认为是丰富的海底岩石。因此，了解这些环境下海底蚀变过程中岩石圈与海水之间的化学交换是评价地球化学旋回的一个重要问题。微量元素丰度和同位素（Li， B， C， O, Sr）组成将用于揭示海洋岩石圈杂岩挖掘和岩石圈地幔隆升过程中基底海水环流的演化过程。将这些数据与地层温度和矿脉年龄的估计相结合，可以重建反应途径和速率。这些数据是审查海洋岩石圈和海洋之间的交换预算所必需的。此外，岩脉形成的温度和年龄信息将有助于揭示岩石圈晚期沿缓慢扩张脊的增生和隆升动力学。ODP Leg 209碳酸盐岩脉的数据表明，微量元素丰度、Li、O、Sr同位素组成和放射性年龄测定可以结合起来解释海洋岩石圈挖掘和与海水相互作用的晚期历史。

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.