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

点击翻译按钮获取中文摘要

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.