Constraining melt concentration and strain distribution around basalt dykes in partially molten olivines
S. Vinciguerra, X. Xiao, B. Evans, 2008. "Constraining melt concentration and strain distribution around basalt dykes in partially molten olivines", Structure and Emplacement of High-Level Magmatic Systems, K. Thomson, N. Petford
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Experiments were performed to determine melt concentration and strain distributions around basalt dykes in a San Carlos olivine matrix containing 10 wt% MORB (mid-ocean ridge basalt). Undrained triaxial compression tests were conducted at 1473 K and a confining pressure of 300 MPa, at constant stresses (80–160 MPa) and constant strain rates ranging from 5×10−5 to 3×10−4 s−1. Melt distribution in the dyke–matrix interface was determined by image analysis and chemical profiles. Melt migration appears to be enhanced by porosity of the microstructure and by the loading conditions. The presence of the dyke does not influence the bulk strength of the sample. Highest melt concentrations, and, presumably, the highest stress concentrations, are found at the tip of the dyke. The matrix deformation appears to be controlled by granular flow, but dilatancy occurs near the tip of the dyke, indicating coupled MORB transport and granular flow.
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Structure and Emplacement of High-Level Magmatic Systems
There are continual rounds of annual conferences, special sessions and other symposia that provide ample opportunity for researchers to convene and discuss igneous processes. However, the origins of laccoliths and sills continue to inspire and confound geologists.
In one sense, this is surprising. After all, don’t we know all we need to know about these rocks by now? As testified by the diverse range of topics covered in this volume, the answer is clearly ‘no’.
This book contains contributions on physical geology, igneous petrology, volcanology, structural geology, crustal mechanics and geophysics that cover the entire gambit of geological processes associated with the shallow emplacement of magma. High-level intrusions in sedimentary basins can also act as hydrocarbon reservoirs and as sources for thermal maturation.
In drawing together a diversity of perspectives on the emplacement of sills, laccoliths and dykes we hope to advance further our understanding of their behaviour.