Vertical distribution and alteration of dikes in a profile through the Troodos ophiolite

Abstract

In situ oceanic crust at intermediate depths of from one to five km is presently largely inaccessible to continuous examination and sampling except in the possibly special circumstances of major transform faults. The study of ophiolites over this interval, where thin, sub-vertical dikes are usually important, may provide guidance to the nature of in situ oceanic crust at these depths. The likelihood that similarities exist between in situ and ophiolitic oceanic crust has recently been strengthened by the possible identification of a dike complex below 0.8-km depth in DSDP Hole 504B1. Sub-vertical basic dikes occur over a 4.6-km depth interval from 0.2 to 4.8 km crustal depth in a profile through the Troodos, Cyprus, ophiolite. Exponential growth and arctangent decay in dike density occur over 2.3-km and 1.0-km intervals, respectively. Secondary magnetite is the dominant dike magnetic material of the dikes and associated screens. These results have implications for the construction, alteration history and magnetization of in situ oceanic crust at intermediate depths.