Limits and biases on the three-dimensional vorticity analysis using porphyroblas system: a discussion and application to natural example

A description on the systematic errors associated with the measurement of the vorticity numbers is presented and an application to a real example is discussed. We show that strong biases and systematic errors derive both from some physical assumptions (Jeffery or Mulchrone model) rarely encountered by natural systems as well as by the fact that these vorticity techniques require measurements of the geometrical parameters of porphyroblasts-matrix system by using outcrop surfaces or thin section methods that are inherently biased. Applying different vorticity plots we analyse an example and discuss in detail the effective systematic errors distribution and the ambiguity in measuring the mean vorticity numbers Wn.