Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4716201 | Lithos | 2013 | 12 Pages |
Abstract
Pressure estimates from clinopyroxene-melt pairs range from 0 to 10Â kbar overall (13 dykes) indicating polybaric crystallization. The lowest pressures are recorded by clinopyroxene oikocrysts intergrown with plagioclase, which likely represent the dyke emplacement depths. Clinopyroxene phenocrysts and plagioclase-free oikocryst cores yield a higher range of crystallization pressures at 4-6Â kbar, corresponding to mid-crustal depths of 11-17Â km. There is no spatial pattern in the pressure variations, suggesting a rather uniform level of magma stagnation and crystallization in all areas of the HOD. Partial crystallization at intermediate depths is consistent with the inference of entrained crystals and with geochemical evidence for crystal accumulation in some of the dykes. Comparison of model magma densities and the crustal density derived from seismic velocity profiles suggest the dyke magmas had positive buoyancy in the lower- and middle crust and near-neutral buoyancy in the upper crust. The depth of magma stagnation or pooling at 11-17Â km depth may relate to this or to the brittle-ductile transition in the felsic Damara crust.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geochemistry and Petrology
Authors
Jakob K. Keiding, Oliver Frei, Axel D. Renno, Ilya V. Veksler, Robert B. Trumbull,