Chemical transects across intra-oceanic arcs: implications for the tectonic setting of ophiolites

Taylor, R.N., Murton, B.J. and Nesbitt, R.W. (1992) Chemical transects across intra-oceanic arcs: implications for the tectonic setting of ophiolites. Geological Society London Special Publications, 60 (1), 117-132. (doi:10.1144/GSL.SP.1992.060.01.07).

Abstract

Systematic spatial variations in Ti, Y, and Zr are found in volcanic sequences sampled as transects from back-arc, through arc, to trench within the western Pacific intra-oceanic arc systems. These correlations occur regardless of eruption age, reflecting the retention of relative positions between individual tectonic units. Concentrations of these incompatible elements are taken to reflect the nature of the underlying mantle at a particular trench-volcano distance during the subduction process. Volcanics become more depleted trenchwards, implying that progressively shallower levels melts were extracted from more refractory or harzburgitic mantle. A model is proposed whereby a subduction system is superimposed on a compositionally stratified mantle, which is a product of an earlier spreading event. On the basis of this evidence, the trench-distance variation model is applied to the Troodos ophiolite complex. Similar spatial changes in lava chemistry are found across the ophiolite, providing evidence for the relative position of the Troodos trench and direction of subduction beneath the Troodos basin. These findings have implications for studies in other orogenic terrains where structure and exposure permit their application.

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Contributors

Author: R.N. Taylor

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