Mass transfer and fluid flow during detachment faulting and development of an oceanic core complex, Atlantis Massif (MAR 30°N)

摘要: The Atlantis Massif (Mid-Atlantic Ridge, 30°N) is an example of oceanic core complex (OCC) exposed by a major fault system. Our integrated field and analytical study mafic ultramafic rocks on the south wall massif demonstrates interplay fluids, mass transfer, metamorphism in strain localization associated with evolution detachment shear zone development this OCC. Extensive talc-amphibole-chlorite metasomatism as well heterogeneous, crystal-plastic to cataclastic deformation characterize strongly foliated, 100-m-thick faulting. metasomatic are key elements OCC record metamorphic history that distinct from underlying basement rocks. Talc-rich preserve textural geochemical characteristics their protoliths. Although primary textures mineral parageneses commonly obliterated dominated amphibole, bulk rock data point protolith. Major trace indicate mutual interaction between gabbroic during metasomatism, which together microstructures suggest localized circulation oxidizing, Si-Al-Ca-rich fluids transfer high zones. This type flow was more pervasive led serpentinized domains wall. In contrast, microfracturing dominantly static less deformed domains, suggesting significant amount controlled diffuse fractures lack strong preferred orientation. Distinct differences lithologies, overprinting, degree central dome demonstrate lateral vertical heterogeneity composition, alteration, structure