Exhumation and carbonation of the Atlantis Bank core complex constrained by in situ U-Pb dating and Δ47 thermometry of calcite veins, SW Indian Ridge

• DOI: 10.1016/j.epsl.2022.117474
• Publication Date: 2022-03-24T22:16:12Z
• Authors: Mark A. Kendrick; Oliver Plümper; Jian-Xin Zhao; Yuexing Feng; William F. Defliese; Inigo A. Müller; Martin Ziegler
• Keywords: Seafloor Spreading; Sill

The Atlantis Bank is a representative example of an oceanic core complex formed on slow-spreading ridge. It dominated by olivine gabbros emplaced at ∼12 Ma and exhumed from original depths more than ∼2500 metres below seafloor (mbsf). In order to investigate the timing exhumation low-temperature alteration we investigated twenty-two calcite veins in samples recovered 809-mbsf Hole U1473A drilled during Expedition 360 International Ocean Discovery Program. yielded laser ablation U-Pb bulk U-Th ages ranging 10.4±0.3 273±5 Ka. They have average Δ47 formation temperature 21±4 °C 87Sr/86Sr rare earth element signatures typical seawater. These data preclude previous cooling models that invoked 250 heat pulse related sill emplacement ∼9.4 Ma. Instead, combined age indicate simple path which were close cooled mean earliest 1.6±0.7 Myr after accretion broadly similar reported for other complexes. However, 12 means it has recorded longer carbonation history. vein ∼83% growth occurred period 3.1±0.9 between ∼10.4 ∼7.3 are estimated concentration 0.15±0.04 wt% CO2. Therefore if veining proportionally one another, initial rate was ∼400±200 μg/g CO2 per Myr. A single with 5.8±0.4 7.3 1 suggesting virtual hiatus carbonation. resumed 0.27-1 three samples. uncertainty these very young substantial, meaning only loosely constrained as to, or lower than, ∼400 demonstrate recent old ocean crust significant probably ongoing. Given complexes form crustal-scale detachments provide high permeability pathways, they bathymetric highs where reactive lithologies can be exposed seafloor, like could sites long-lived seafloor.