0000000000744444
AUTHOR
Gary Stevens
Growth of zircon and titanite during metamorphism in the granitoid-gneiss terrane south of the Barberton greenstone belt, South Africa
AbstractSHRIMP U-Pb zircon and titanite dating have been used to constrain the timing of mid- to lower- crustal metamorphism (∼650—700°C and 8—11 kbar) and syn-kinematic melting in the granitoid gneiss- dominated terrane south of the Barberton greenstone belt, South Africa. This study is concentrated on a clastic metasedimentary unit exposed in one of several greenstone remnants and a late-kinematic trondhjemite intrusive into spatially associated mixed gneisses. Locally, the clastic metasediments show extensive replacement of garnet and plagioclase by epidote and titanite. The titanites yield an upper intercept date of 3229±9 Ma, and provide a minimum age for the peak of metamorphism. Zirc…
Is the Crucible Reproducible? Reconciling Melting Experiments with Thermodynamic Calculations
Experimental studies and thermodynamic modelling have advanced our understanding of partial melting in the crust and have provided a frame-work for the interpretation of migmatites, residual granulites and granites. Each approach has advantages and pitfalls, and each is more appropriate than the other for investigating particular aspects of the melting process. A comparison of these two approaches may be useful because, together, they potentially give more information. A comparison of a small number of experiments with model calculations using equivalent bulk compositions shows important consistencies between the results, especially regarding the overall topologies of key melting equilibria…