P-T-D histories from quartz: A case study of the application of the TitaniQ thermobarometer to progressive fabric development in metapelites

This study investigates the ability of quartz to record segments of the pressure-temperature-deformation (P-T-D) path in poly-deformed metamorphic terranes and the associated application of the Ti-in-quartz thermobarometer (TitaniQ). Metapelites from the Strafford Dome (eastern Vermont) were selected for this study because they record progressive fabric development during prograde metamorphism and have well constrained P-T-D histories from previous work. Results of this investigation are in agreement with previous studies and demonstrate that quartz in these samples records additional distinct intervals of the P-T-D path. Six preserved quartz equilibration events include: (1) early prograde growth during burial; (2) kyanite-in quartz-producing reactions; (3) prenappe emplacement equilibration during isobaric heating; (4) precipitation of quartz in quartz-feldspar domains during crenulation cleavage development due to solution transfer; (5) quartz-producing (chlorite-out) reactions during heating postnappe emplacement; and (6) retrograde quartz overgrowths from an influx of siliceous fluids. Modeling quartz volume allows for the identification of quartz-producing reactions in P-T space; the same may be done for Ti-phases to better constrain activities during reequilibration events. An integration of cathodoluminescence imaging, microstructural and petrographic investigation, isochemical forward stability modeling, and thermobarometry allows identification and interpretation of zoning patterns in quartz to unravel histories that would otherwise not be obtainable.