The generation of prograde P-T-t points and paths; a textural, compositional, and chronological study of metamorphic monazite

Analogue and computational models principally provide our present understanding of the mechanisms of prograde metamorphism and orogenesis, yet, due to the difficulty of linking prograde age information with the pressure temperature (P-T) evolution of a rock, these models for the most part remain untested. Here, we describe an approach that allows multiple prograde pressure-temperature-time (P-T-t) points to be generated on single samples providing a means to construct detailed P-T-t loops, enabling the duration of metamorphic events, the timing of burial and the rate of heating experienced by individual samples to be determined. We use this combination approach to generate multiple prograde P-T-t points for three samples from the Himalayan and Canadian Cordillera and show for the first time that the duration of the metamorphic events are similar in each area and prograde heating rates vary from 2.4+/-1.2 degreesC/Ma to 5.0+/-2.0 degreesC/Ma. The P-T-t paths generated this way agree well with the established geological history of the studied areas and allow additional constraints to be placed on the mechanisms of orogenesis. (C) 2004 Elsevier B.V. All rights reserved.