Database of mineral compositions within the lowermost oceanic crust accreted at fast-spreading ridges (Hess Deep, East Pacific Rise, IODP Leg 345)

This database contains mineral major and trace element compositions of gabbroic rocks composing the lower oceanic crust accreted at the East Pacific Rise and recovered at Hess Deep during IODP Leg 345 (Gillis et al., 2014a). Hess Deep is located at 2°15’N, 101°30’W in the Pacific Ocean, at the western tip of the Cocos-Nazca spreading centre, a westward-propagating oceanic ridge that progressively opens the oceanic lithosphere formed at the adjacent East Pacific Rise (Fig. 1a; Searle and Francheteau, 1986; Karson et al., 2002). Hess Deep is an East-West trending intraoceanic rift reaching 5200 mbsl (metres below sea level) at its deepest point (Fig. 1b,c). It is a tectonic window exposing a complete section of 1.3 Myr oceanic crust accreted at the fast-spreading East Pacific Rise (~130 mm/yr; Rioux et al., 2012; Rowan and Rowley, 2014), ranging from pillow basalts to sheeted dikes, isotropic gabbros, layered gabbros and troctolites, and upper mantle peridotites (e.g., Francheteau et al., 1990, 1992; Hekinian et al., 1993; Lissenberg et al., 2013).
The gabbroic rocks included in this database are primitive in composition and range from olivine-rich troctolites to troctolites, olivine gabbros, olivine gabbronorites and gabbros.