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Journal Articles Geochemistry, Geophysics, Geosystems Year : 2011

Oceanic core complex development at the ultraslow spreading Mid-Cayman Spreading Center

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Abstract

Roughly a third of the global mid-ocean ridge system spreads at <20 mm/yr (full rate) with predicted low crustal thicknesses, great axial depths, end-member basalt compositions, and prominent axial faults. These predictions are here further investigated along the ultraslow (15-17 mm/yr) Mid-Cayman Spreading Center (MCSC) through a compilation of both previously published and unpublished data. The MCSC sits along the Caribbean-North American plate boundary and is one of the world's deepest (>6 km) spreading centers, and thought to accrete some of the thinnest (∼3 km) crust. The MCSC generates end-member mid-ocean ridge basalt compositions and hosts recently discovered hydrothermal vents. Multibeam bathymetric data reveal that axial depth varies along the MCSC with intraridge rift walls defined by kilometer-scale escarpments and massifs. Dredging and near-bottom work has imaged and sampled predominantly basaltic lavas from the greatest axial depths and ∼15% peridotite surrounded by gabbroic rocks from the prominent massifs. The gabbroic rocks exhibit wide compositional variation (troctolites to ferrogabbros) and in many places contain high-temperature (amphibolite to granulite facies) shear zones. Gabbroic compositions primarily reflect the accumulation of near-liquidus phases that crystallized from a range of basaltic melts, as well as from interactions with interstitial melts in a subaxial mush zone. Magnetization variations inverted from aeromagnetic data are consistent with a discontinuous distribution of basaltic lavas and structurally asymmetric spreading. These observations support an oceanic core complex model for MCSC seafloor spreading, potentially making it a type example of ultraslow seafloor spreading through mush zone and detachment fault crustal processes.
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hal-00585882 , version 1 (18-03-2022)

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N. W. Hayman, N. R. Grindlay, M. R. Perfit, P. Mann, Sylvie Leroy, et al.. Oceanic core complex development at the ultraslow spreading Mid-Cayman Spreading Center. Geochemistry, Geophysics, Geosystems, 2011, 12, pp.Q0AG02, 21 PP. ⟨10.1029/2010GC003240⟩. ⟨hal-00585882⟩
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