199 MSA Awards Lectures, Presidential Address, and Annual Business Meeting

Tuesday, 2 November 2010
3:00 PM - 5:30 PM
Mile High Ballroom 2AB/3AB

MSA ROEBLING MEDAL LECTURE: THE THREE PARTNERS OF METAMORPHIC PETROLOGY

Paper number: 199-1
Program: Technical Sessions
Time: 3:00 PM – 3:30 PM

Authors

  • Robert C. Newton Presenting Author
    University of California at Los Amgeles, Los Angeles, CA

Abstract

In addition to supplying the initial motivation for experimental and theoretical petrology, field observations in metamorphic terranes have generated a remarkable feed-back mechanism with which to test the less-direct, and sometimes ambiguous, conclusions of the laboratory-based approaches. A simple example is the Al2SiO5 minerals. “Geo-experimental” phase diagrams, in which equilibrium pressure-temperature relations of the three common polymorphs were constructed entirely from geologic criteria, challenged the validity of the results of experimental petrology in the 1960’s. This audacious geo-experimental approach was upheld by the results of later experiments. Vindication of the quantitative field-based approach in the Al2SiO5 system served notice to the metamorphism community that “field-testing” of conclusions from the indoor methods can provide essential evidence with which to critique and solidify the dataset of petrology. The geo-experimental approach has been applied successfully to more complex mineral systems, including those with solid solutions, such as zoisite-clinozoisite and the sodic plagioclase “peristerite” feldspars.

Minerals containing volatile components provide an important but difficult avenue for on-going investigation, because they can yield information about complex metamorphic fluids, about which little definitive data yet exist. The minerals biotite, apatite, cordierite, scapolite, carbonates and Fe-Ti oxides may contain, in their chemical make-up, records of the activities of H2O, CO2, SO2, O2, F, Cl, and S in mineralizing fluids which have acted to modify the deeper crust and the upper mantle. Experimental and theoretical investigations on these minerals in the presence of multi-component fluids, together with appropriately selected “field-testing”, can serve to interpret such important earth processes as recycling of surface materials through the mantle and the generation of volatile-fluxed magmatism.