Abstract

The extrusive section on the northern flank of the Troodos ophiolite is 1,000 to 1,500 m thick and consists of about 12 lithologic units of pillowed and massive lava and breccia. Some pillowed units, which average 100 to 200 m in thickness, vary systematically from lava tubes up to 6 m in diameter at the base, through common pillows less than 1 m in diameter, to small pillows and extrusive breccias at the top. These assemblages appear to be individual volcanoes, suggesting episodic volcanic accretion. The upper 100 to 200 m of the section is pervasively altered and oxidized, but fresh volcanic glass is preserved throughout most of the extrusive section. The lavas are subdivided on geochemical evidence into a lower, differentiated andesite to dacitic andesite series resembling evolved island-arc tholeiites and an upper series of picrite, mafic basalt, and basaltic andesite very low in TiO2, K2O, P2O5, Nb, Rb, and Ba. The highly depleted basalt and basaltic andesite resemble lavas from ocean crust near island arcs. Lateral continuity of lithologic units interpreted as individual volcanoes and the relatively constant dips of the extrusive rocks suggest that tilting and rotation have not played major roles in the accretion process. The occurrence of fractionated lavas at the base and primitive lavas at the top suggests a broad zone of accretion, located above a subduction zone.

First Page Preview

First page PDF preview
You do not currently have access to this article.