Geochemistry and intrusive directions in sheeted dikes in the Troodos ophiolite: Implications for mid‐ocean ridge spreading centers

Abstract

Sheeted dikes at mid‐ocean ridge volcanoes represent the link between deep magma production and storage processes and shallow processes such as volcanism and hydrothermal activity. As such, they are crucial for the interpretation of many observations at mid‐ocean ridges or other volcanoes with pronounced rift zones, including topography, hydrothermal systems, petrology, and geochemistry. We carried out a structural, magnetic, and chemical investigation of a 4 × 10 km sheeted dike section in the Troodos ophiolite, Cyprus. On the basis of major and trace element geochemistry, we distinguish dikes that may be correlated with the basal high‐Ti series (HTS) lavas from those of the overlying low‐Ti series (LTS) lavas. All dikes studied are nearly parallel to each other, with vertical or steeply dipping planes whose strike likely indicates the orientation of the spreading center. Anisotropy of magnetic susceptibility measurements suggests that the HTS and LTS dikes intrude in fundamentally different ways. HTS dikes reflect the intrusive behavior of dikes in the vicinity of a magma supply system and define ridge parallel intrusive sheets that radiate out from the magma chamber. LTS dikes show a bimodal, orthogonal set of intrusive directions, one shallow and one near vertical. Near‐lateral propagating dikes provide a means for delivery of magma into distant portions of a rift system, and near‐vertical dike propagation directions are probably associated with feeder dikes to down‐rift surface flows. Our study suggests that the types of dike intrusive behavior in the Troodos ophiolite may also be typical for “normal” mid‐ocean ridges or other major shield volcanoes with well‐developed rift zones.