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Sampling Guidelines

An important component of this project is the collaboration with colleagues around the world who are able to collect appropriate geochronology samples from key units (mainly regional dolerite dyke swarms) in their regions.

Medium to coarse grain size is critical to success in separating baddeleyites and zircons for U-Pb dating. The coarser the grain size the better, and gabbroic pegmatites are ideal. As a guideline, material from the centre of a >10 m wide dolerite dyke or sill should be suitable. Also we need a GPS location and a good description of the sample site and unit. For dolerite dykes, it is best to collect samples from dykes whose trend is clear and which are part of a regional swarm. Samples can be very small---only need to be about 1-2 kg in size--so there is probably sufficient material for some units already available in your archives.