Interpretation of the FIA succession

Figure 2 shows that porphyroblastic samples from which FIAs could be measured are present relatively uniformly across the eastern half of the region only becoming patchily distributed to the west and this is significant for the construction of isograds (see below). Garnet is present in the easternmost samples but staurolite is not. Furthermore, garnet porphyroblasts are commonly overgrown by staurolite. Both features suggest that in this region garnet grew before staurolite and this characteristic (see Table 3) provides one of four criteria that were used to determine the relative timing of successive FIAs. The few samples containing changes in FIA trend from the cores to the rims of garnet porphyroblasts provide a second criterion, a third was provided by samples containing pseudo (p-FIAs) versus actual FIAs (e.g. Figs. 8 and 9) in garnet and staurolite porphyroblasts (Table 4) and a fourth was provided by those porphyroblasts with trails truncated by the matrix foliation versus those whose trails were continuous with it (e.g. Figs. 7 and 10). The FIA succession indicated by arranging changes in FIA trend from garnet to staurolite in the same sample in Table 3 so that they do not conflict is supported by that in Table 4 and by those whose trails are truncated versus continuous with the matrix foliation. This succession is from FIA 1 (trending NE-SW), to FIA 2 (trending E-W), to FIA 3 (trending SE-NW), and FIA 4 (trending NNE-SSW). Table 2 shows all the samples for which FIAs have been determined. Samples containing only one FIA trend have been placed on this table based on that trend and secondly, whether the inclusion trails are truncated (FIA 1) or continuous (FIA 4) with the matrix foliation. FIA 1 and 2 is preserved only in garnet and staurolite porphyroblasts. FIA set 3 is mainly present in garnet and staurolite porphyroblasts. However, a few samples contain this FIA set in andalusite and cordierite porphyroblasts (Table 2). FIA set 4 can be found in each of the porphyroblastic phases. This indicates a progression in the timing of growth as orogenesis proceeded of garnet, staurolite, andalusite and cordierite.