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.本数据库收录了东太平洋海隆（East Pacific Rise）增生形成的洋壳下部辉长岩类岩石的矿物主量与微量元素组成，这些岩石由综合大洋钻探计划第345航次（IODP Leg 345）在赫斯深渊（Hess Deep）回收获取（Gillis等，2014a）。赫斯深渊位于太平洋海域2°15′N、101°30′W处，地处科科斯-纳斯卡扩张中心（Cocos-Nazca spreading centre）西端，该扩张中心为一条向西传播的洋中脊，可逐步拉开相邻东太平洋海隆形成的海洋岩石圈（oceanic lithosphere）（图1a；Searle与Francheteau，1986；Karson等，2002）。赫斯深渊为近东西向展布的洋内裂谷，最深处达5200米海平面下（metres below sea level, mbsl）（图1b、c）。其作为构造窗（tectonic window），完整出露了在快速扩张东太平洋海隆（约130 mm/yr）处增生形成的1.3百万年洋壳剖面（Rioux等，2012；Rowan与Rowley，2014），岩石序列涵盖枕状玄武岩（pillow basalts）、席状岩墙（sheeted dikes）、各向同性辉长岩（isotropic gabbros）、层状辉长岩（layered gabbros）、橄长岩（troctolites）以及上地幔橄榄岩（upper mantle peridotites）（例如Francheteau等，1990、1992；Hekinian等，1993；Lissenberg等，2013）。本数据库收录的辉长岩类岩石具有原始地球化学组成，岩石类型从富橄橄长岩（olivine-rich troctolites）、橄长岩、橄榄辉长岩（olivine gabbros）、橄榄辉长苏长岩（olivine gabbronorites）直至辉长岩。