Abstract:
Using hygromagmatophile element abundances (normalized to primordial mantle composition), it is possible to discriminate between the tectonic settings of tholeiitic basalts and basaltic andesites (47.0–53.5% SiO2). Based on field and chemical evidence, data from provinces or grouped localities have been compiled in order to establish chemical reference data sets for ocean-island, continental, ocean-ridge and -floor, subduction-zone, and back-arc environments. The disturbing effects of crustal contamination and hydrothermal alteration on the hygromagmatophile (H-)element patterns are of minor significance in the recognition of plate-tectonic settings.
On the basis of the data sets, magmas from a number of ambiguous tectonic settings have been recognized using their H-element patterns. Attention is directed to problems concerning rifting- and drifting-related basalts in an apparent continental setting, and to the origin of ophiolite complexes. Using available data the pillow lavas of the Troodos Ophiolite Complex, Cyprus, are recognized as basalts erupted in a subduction zone environment.