Relationships between syn-tectonic granite fabrics and regional PTtd paths: an example from the Gander-Avalon boundary of NE Newfoundland

Syn-tectonic granitic plutons and their host rocks not only provide a potential wealth of information about the timing and nature of regional kinematics, but also record information about thermal conditions. Successive syn-tectonic plutons emplaced into the Gander Zone of NE Newfoundland preserve fabric overprinting formed during cooling to regional ambient thermal conditions. Ambient conditions have been approximated for each pluton by careful analysis of microstructures and consideration of potential cooling histories, and have illustrated regional exhumation during a tectonic reversal from Silurian-Devonian sinistral transpression to Devonian dextral transpression. Because the time period of emplacement is relatively short by comparison to orogenic events (typically by more than an order of magnitude), individual plutons may record a ‘snap-shot’ of the regional history. By combining information from a number of plutons emplaced sequentially during a period of regional orogenesis, a picture may be built up defining time-temperature-deformation (Ttd) paths. Such information may compliment regional metamorphic PT studies in helping to establish orogenic PTtd paths.