Geochemistry and tectonic setting of the “ophites” from the external zones of the Betic Cordilleras (southern

Mesozoic basic magmatism in the External Zones of the Betic Cordilleras (S. Spain) is represented by small tectonic bodies (ophites) in Triassic formations, and submarine flows with abundant pillow-Iavas interbedded with Jurassic sediments. Both basic igneous manifestations suffered very low- to low-grade metamorphism, more intense in the case of the ophites. Two types of ophites are distinguished on the basis of their primary mineralogy. In the first type, orthopyroxene is present in the less differentiated products. Clinopyroxene and Ca-plagioclase are the main primary phases and quartz appears in the more evolved rocks. In the second type, olivine is present in the less differentiated products. Ti-rich augite and Ca-plagioclase are also important primary minerals, but quartz is absent. Whole-rock chemistry (major and trace elements, including REE) also allows us to discriminate between these two groups. The first group has higher SiOz and lower TiOz, PzOs and lower NazO/KzO ratios than the second. Normative quartz is almost invariably present in this first group, whereas normative nepheline (lower than 5%) is characteristi